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van Loevezijn, Gerard B. S., and J. G. M. Raven. "Facies patterns and depositional processes in two Frasnian mixed siliciclastic-carbonate systems in the Cantabrian Mountains, northwest Spain." Geologos 26, no. 1 (April 1, 2020): 1–23. http://dx.doi.org/10.2478/logos-2020-0001.
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AbstractRelative sea level fluctuations during the Frasnian generated two shallow-marine, mixed siliciclastic-carbonate successions in the Devonian Asturo-Leonese Basin. Each system represents a third-order sequence-stratigraphical unit deposited in the same basin during comparable extreme greenhouse conditions without nearby fluvial entry points. Depositional control on the siliciclastic and carbonate distribution was driven by relative sea level fluctuations, basin geometry, availability of sand and the way sediment was distributed by shelf currents. Early Variscan flexural bending of the continental crust changed the basin shape from a shelf with a gradual profile and low dip (early Frasnian) towards a shelf with a steep depositional dip (late Frasnian). Shelf distribution changed from along-shelf transport (early Frasnian) towards offshore-directed gravity flows (late Frasnian). As a consequence, siliciclastic-carbonate distribution changed from a predominance of skeletal carbonate in the proximal shoreface – foreshore area and siliciclastic predominance distally (early Frasnian), to a distribution pattern with proximal shoreface skeletal carbonates, offshore muddy carbonates and a siliciclastic zone in between where gravity flows distributed the siliciclastic sediment down dip (late Frasnian).
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Ali, Syed Haroon, Osman M. Abdullatif, Lamidi O. Babalola, Fawwaz M. Alkhaldi, Yasir Bashir, S. M. Talha Qadri, and Ali Wahid. "Sedimentary facies, depositional environments and conceptual outcrop analogue (Dam Formation, early Miocene) Eastern Arabian Platform, Saudi Arabia: a new high-resolution approach." Journal of Petroleum Exploration and Production Technology 11, no. 6 (May 15, 2021): 2497–518. http://dx.doi.org/10.1007/s13202-021-01181-7.
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AbstractThis paper presents the facies and depositional environment of the early Miocene Dam Formation, Eastern Arabian platform, Saudi Arabia. Deposition of Dam Formation (Fm.) was considered as a restricted shallow marine deposition. Few studies suggest the role of sea-level change in its deposition but were without decisive substantiation. Here, we describe the facies and high-resolution model of Dam Fm. under varying depositional conditions. The depositional conditions were subjected to changing relative sea level and tectonics. High-resolution outcrop photographs, sedimentological logs, and thin sections present that the mixed carbonate–siliciclastic sequence was affected by a regional tectonics. The lower part of Dam Fm. presents the development of carbonate ramp conditions that are represented by limestones and marl. The depositional conditions fluctuated with the fall of sea level, and uplift in the region pushed the siliciclastic down-dip and covered the whole platform. The subsequent rise in sea level was not as pronounced and thus allowed the deposition of microbial laminites and stromatolitic facies. The southeast outcrops, down-dip, are more carbonate prone as compared to the northwest outcrop, which allowed the deposition of siliciclastic-prone sedimentation up-dip. All facies, architecture, heterogeneity, and deposition were controlled by tectonic events including uplift, subsidence, tilting, and syn-sedimentary faulting, consequently affecting relative sea level. The resulting conceptual outcrop model would help to improve our understanding of mixed carbonate–siliciclastic systems and serve as an analogue for other stratigraphic units in the Arabian plate and region. Our results show that Dam Fm. can be a good target for exploration in the Northern Arabian Gulf.
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Xue, Yongan, Chengmin Niu, Wei Xu, Xiaojun Pang, and Li Zhang. "Sedimentary characteristics and genetic mechanisms of high-quality reservoirs in a mixed siliciclastic-carbonate system in the Qinhuangdao area, Bohai Sea, China." Interpretation 8, no. 2 (May 1, 2020): SF95—SF111. http://dx.doi.org/10.1190/int-2019-0144.1.
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Mixed siliciclastic-carbonate sediments occur broadly in modern and ancient systems. Studies on mixing processes began in shallow shelf environments; however, the genetic model of marine mixed sediments is difficult to apply to continental rift basins due to the complex palaeogeographic environment. We identified three mixing types in the first and second members of the Palaeogene Shahejie Formation (E2s1–2) in the Qinhuangdao area of the Bohai Sea: (1) mixed fan delta, (2) retrogradation mixed sheet, and (3) mixed sheet without siliciclastic influx. Tectonic stability, arid climate, and saline lakes are prerequisite conditions for the development of mixed sediments, whereas the palaeogeomorphologic unit should be the critical factor. We also concluded that the primary sedimentary material contains near-source coarse terrestrial debris, and the advantageous lithologic facies producing biological components are the foundation for high-quality mixed reservoirs, which are characterized by thick layers and favorable porosities and permeabilities. The micritic coatings and early dolomitization against the background of a saline lake environment favored the preservation of primary pores, whereas the leaching by atmospheric water and organic acid erosion during thermal evolution of the source rock created many secondary pores. In addition, hydrocarbon charging protected the reservoir space from carbonate cementation.
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Schwarz, Ernesto, Gonzalo D. Veiga, Gastón Álvarez Trentini, Manuel F. Isla, and Luis A. Spalletti. "Expanding the spectrum of shallow‐marine, mixed carbonate–siliciclastic systems: Processes, facies distribution and depositional controls of a siliciclastic‐dominated example." Sedimentology 65, no. 5 (February 20, 2018): 1558–89. http://dx.doi.org/10.1111/sed.12438.
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Zecchin, Massimo and Caffau, Mauro. "Key features of mixed carbonate-siliciclastic shallow-marine systems: the case of the Capo Colonna terrace (southern Italy)." Italian Journal of Geosciences, Vol. 130, n. 3 (December 1, 2011): 370–79. http://dx.doi.org/10.3301/ijg.2011.12.
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Gomez, Fernando J., and Ricardo A. Astini. "Sedimentology and paleoenvironments of the La Laja Formation (Cambrian), Quebrada La Laja, Sierra Chica de Zonda, San Juan, Argentina." Andean Geology 33, no. 1 (June 30, 2010): 19. http://dx.doi.org/10.5027/andgeov33n1-a02.
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The La Laja Formation is a key unit regarding the hypothesis of the Argentine Precordillera as a Laurentia-derived allochtonous terrane in the south central Andes. Together with the Cerro Totora Formation it comprises the oldest unit exposed at the base of the Lower Paleozoic carbonate platform of the Precordillera. According to previous work these units record the rifting-drifting history of this terrane exotic to Gondwana. The La Laja Formation contrasts with the rest of the overlying units of the Cambro-Ordovician carbonate platform by being partly mixed carbonate-siliciclastic. A detailed facies analysis of the five recognized members in the reference section at Quebrada La Laja (Sierra Chica de Zonda, San Juan Province) allow the recognition of 19 microfacies grouped into four main environmentally significant associations: 1) a storm-influenced, deep subtidal environment with variable influx of fine siliciclastic sediments; 2) shallow subtidal, 3) mixed shallow subtidal and 4) shallow subtidal to intertidal occasionally with well developed high-frequency tidal flat cycles. No deeper basinal or slope facies were found. In contrast, the unit largely records shallow-marine facies with some evidence of subaerial exposure. Medium to coarse, calcareous, feldspar-rich sandstones and sandy limestones characterize the El Estero Member. The base of the Soldano Member shows profuse development of cyclicity with capping oolitic shoals. This member and the upper Juan Pobre Member contain deeper subtidal intervals, below the storm weather wave base, with high percentages of fine terrigenous material represented by shaly marls and nodular limestones. Skeletal-rich and oolite-rich storm beds are recorded within them. Relative shallowing to subaerial environments recorded within the Rivadavia and Las Torres members, with the development of ribbon limestones, intraclastic rudstones, microkarstic surfaces and exposure breccias. Herringbone cross-bedded oolite shoals are common at the top of the uppermost Las Torres Member. The transition into the overlying Zonda Formation is represented by an abrupt rearrangement of the depositional systems and development of meter-scale microbial-rich peritidal cycles. Several orders of superposed cyclicity are recorded within the La Laja Formation. Larger-scale cycles ('Grand Cycles') are inferred from alternating members with important amounts of siliciclastics, whereas meter-scale cycles indicate higher frequency superposed mechanisms. Altogether these show a complex depositional history linking environmental and tectono-eustatic signatures.
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Best, Mairi M. R., and Susan M. Kidwell. "Bivalve taphonomy in tropical mixed siliciclastic-carbonate settings. II. Effect of bivalve life habits and shell types." Paleobiology 26, no. 1 (2000): 103–15. http://dx.doi.org/10.1666/0094-8373(2000)026<0103:btitms>2.0.co;2.
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Bivalve death assemblages from subtidal environments within the tropical Bocas del Toro embayment of Caribbean Panama permit a test of the extent to which levels of damage are determined by the intrinsic nature of shell supply (proportion of epifaunal species, thick shells, calcitic shells, low-organic microstructures), as opposed to the extrinsic postmortem environment that shells experience. Only damage to interior surfaces of shells was used, to ensure that damage was unambiguously postmortem in origin. We find that facies-level differences in patterns of damage (the rank order importance of postmortem encrustation, boring, edge-rounding, fine-scale surface degradation) are overwhelmingly controlled by environmental conditions: in each environment, all subsets of the death assemblage present the same damage profile. The composition of shell supply affects only the intensity of the taphonomic signature (i.e., percentage of shells affected) only in environments containing hard substrata (patch reefs, Halimeda gravelly sand, mud among patch reefs). In these environments, epifauna, whether aragonitic or calcitic and whether thin or thick, exhibit significantly higher damage than co-occurring infauna, probably due to the initial period of seafloor exposure they typically experience after death. Thick shells (>0.5 mm), regardless of life habit or mineralogy, are damaged more frequently than thin shells, probably because of selective colonization by fouling organisms. Calcitic shells show no consistently greater frequency of damage than aragonitic shells high-organic microstructures yield mixed patterns. Taphofacies surveys in such depositional systems could thus be confidently based on any subset of the fauna, including diagenetically residual assemblages of calcitic shells and thick-shelled molds. Further tests are needed to determine whether the higher levels of damage observed on some subsets of shells are a consequence of greater time-averaging (thus lower temporal resolution), greater exposure time, preferential attack (potential bias in relative abundance), or some combination of these. Paleobiologically, however, the implication is that ecological subsets of bivalve assemblages are not isotaphonomic, either in tangible damage or in probable bias, within hard-substrate environments, although they may be within soft-sediment environments. In actualistic studies, targeting broad classes of taxa for comparison across environments maximizes our ability to extrapolate taphonomic guidelines into the fossil record, where life habits, skeletal types shallow subtidal habitats have dramatically different patterns of abundance and deployment.
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Darngawn, Jehova L., Satish J. Patel, Jaquilin K. Joseph, and Apuva D. Shitole. "Genetic sequence stratigraphy on the basis of ichnology for the Middle Jurassic basin margin succession of Chorar Island (eastern Kachchh Basin, western India)." Geologos 25, no. 1 (April 1, 2019): 31–41. http://dx.doi.org/10.2478/logos-2019-0003.
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Abstract Synrift basin margin successions are greatly influenced by eustatic sea level changes, tectonics and accommodation space filled in by sediments. The Middle Jurassic (Bajocian–Callovian) of Chorar Island (western India) comprises a ~109-m-thick synrift basin margin succession of clastic, non-clastic and mixed siliciclastic-carbonate rocks which are here analysed and categorised into nine lithofacies. The succession is bioturbated to varying intensities; 16 identified ichnogenera can be assigned to environmentally related groups of five trace fossil assemblages, which include Gyrochorte, Hillichnus, Rhizocorallium, Skolithos and Thalassinoides. These ichnoassemblages document the Skolithos and Cruziana Ichnofacies which marks a change in energy conditions, sedimentation dispersal patterns and bathymetry in a shallow-marine environment. The Bajocian–Callovian succession is further analysed on the basis of sedimentological and ichnological data that show two genetic sequences consisting of Transgressive Systems Tract and Highstand Systems Tract bounded by Maximum Flooding Surface. The synrift basin margin succession of the Middle Jurassic of Chorar Island shows cyclicity in deposition; the Bajocian–Bathonian succession represents progradational to retrogradational coastlines, while the Callovian succession documents an aggrading progradational coastline.
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Vital, Helenice, Moab Praxedes Gomes, Werner Farkatt Tabosa, Eugênio Pires Frazão, Claude Luiz Aguilar Santos, and José Saraiva Plácido Júnior. "Characterization of the Brazilian continental shelf adjacent to Rio Grande do Norte state, NE Brazil." Brazilian Journal of Oceanography 58, spe1 (2010): 43–54. http://dx.doi.org/10.1590/s1679-87592010000500005.
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This study focuses on the analysis of high-resolution seismic profiles, integrated with sedimentological, echosounder, SRTM and satellite image datasets, of the Brazilian continental shelf adjacent to the Rio Grande do Norte State, NE Brazil. Located in the northeast of Brazil, the State of Rio Grande do Norte is bounded by two main coastal and shelf systems: the eastern coastal-shelf, from the Sagi River to the Touros High, and the northern coastal-shelf, extending from Touros High to Tibau. This shelf represents a modern, highly dynamic mixed carbonate-siliciclastic system characterized by reduced width and shallow depths as compared with other parts of the Brazilian shelf. It has an average width of 40 km, the shelf-break lying at a depth of ~ 60 m. This shelf is subject to the full strength of the westerly South Equatorial current combined with high winds and moderate to high tides and waves. A sharply defined stratigraphic boundary, probably between the Pleistocene and Holocene deposits, is clearly to be observed in the seismic record. Incised-valleys extending from the main river mouths (e.g.the Potengi, Açu, and Apodi) to the shelf break dominate the area investigated and may indicate periods of lower sea level.
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Jones, L. E., and B. W. Sellwood. "Palaeogeographic Significance of Clay Mineral Distributions in the Inferior Oolite Group (Mid Jurassic) of Southern England." Clay Minerals 24, no. 1 (March 1989): 91–105. http://dx.doi.org/10.1180/claymin.1989.024.1.08.
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AbstractFive areally distinct mineral assemblages are recognized in the Inferior Oolite of S. England. In each area, vertical (stratigraphic) variations are insignificant. The five assemblages comprise varying proportions of illite, illite-smectite, kaolinite, chlorite and kaolinite-smectite, the mixed-layer clays being largely poorly crystalline and randomly interstratified. A predominantly detrital rather than authigenic origin is suggested for most of the clays. Shallow-water platform carbonates contain kaolinite with illite and illite-smectite. Kaolinite decreases in abundance away from former mid-Jurassic land areas, the deeper shelf and more basinal facies being dominated by illite and/or illite-smectite. Possible volcanic contributions to clay suites are suggested but cannot yet be fully evaluated. The palaeogeographic usefulness of clay mineral suites is confirmed, even in carbonate-dominated systems.
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Ajdanlijsky, George, Annette E. Götz, and André Strasser. "The Early to Middle Triassic continental–marine transition of NW Bulgaria: sedimentology, palynology and sequence stratigraphy." Geologica Carpathica 69, no. 2 (April 1, 2018): 129–48. http://dx.doi.org/10.1515/geoca-2018-0008.
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AbstractSedimentary facies and cycles of the Triassic continental–marine transition of NW Bulgaria are documented in detail from reference sections along the Iskar river gorge between the villages of Tserovo and Opletnya. The depositional environments evolved from anastomosing and meandering river systems in the Petrohan Terrigenous Group to mixed fluvial and tidal settings in the Svidol Formation, and to peritidal and shallow-marine conditions in the Opletnya Member of the Mogila Formation. For the first time, the palynostratigraphic data presented here allow for dating the transitional interval and for the precise identification of a major sequence boundary between the Petrohan Terrigenous Group and the Svidol Formation (Iskar Carbonate Group). This boundary most probably corresponds to the major sequence boundary Ol4 occurring in the upper Olenekian of the Tethyan realm and thus enables interregional correlation. The identification of regionally traceable sequence boundaries based on biostratigraphic age control is a first step towards a more accurate stratigraphic correlation and palaeogeographic interpretation of the Early to early Middle Triassic in NW Bulgaria.
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Dix, George R., and Elliott T. Burden. "Platform drowning leading to cool-water carbonate deposition: evolution of a Late Ordovician (Turinian–Chatfieldian) mixed-sediment platform within the Taconic orogen (Long Point Group, Newfoundland Appalachians)." Canadian Journal of Earth Sciences 55, no. 9 (September 2018): 1036–62. http://dx.doi.org/10.1139/cjes-2018-0020.
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Late Ordovician (Turinian–Chatfieldian) drowning of a mixed carbonate–siliciclastic platform within the Taconic Orogen (Newfoundland Appalachians) is recorded by net deepening of an initial warm, shallow-water platform succession (Lourdes Formation) culminating in a metre-scale thick condensed interval that characterizes a drowning succession punctuated by storm deposits. Composition of transported material suggests that seaward drowning was coupled with back-stepping of a high-energy carbonate factory related to hinterland uplift and erosion that would eventually lead to drowning of the outer platform beneath marine-transported siliciclastic sediments (Winterhouse Formation). In the new offshore shelf setting, a sparse reciprocal stratigraphy of fine- to very coarse-grained phosphatic carbonate and mixed sediment is interpreted to document gravity-flow deposition downgradient from either a sustained or episodically developed high-energy cool-water carbonate source along the inner shelf. Transported carbonate was cemented rapidly at temperatures no warmer than 16 °C–23 °C, possibly within a seasonal oceanic thermocline. An upsection decrease in abundance of carbonate by the early Edenian is associated with a dramatic increase in siliciclastic supply. The Turinian–Edenian succession of platform drowning, oceanographic transition to cool-water carbonate production, and, later, its termination by increased siliciclastic supply reflects a first-order tectonic control proximal to uplift within the Taconic Orogen. Similar structural and oceanographic changes along the contemporary distal Laurentian margin provides the basis, with improved biostratigraphic control, for future analysis of the significance of proximal–distal stratigraphies in response to regional foreland tectonism.
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Best, Mairi M. R., and Susan M. Kidwell. "Bivalve taphonomy in tropical mixed siliciclastic-carbonate settings. I. Environmental variation in shell condition." Paleobiology 26, no. 1 (2000): 80–102. http://dx.doi.org/10.1666/0094-8373(2000)026<0080:btitms>2.0.co;2.
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Contrary to the geological stereotype of pure-carbonate reef platforms, approximately 50% of shallow shelf area in the Tropics is accumulating siliciclastic and mixed siliciclastic-carbonate sediments. Taphonomic characterization of these settings is thus essential for assessing variation among major facies types within the Tropics, as well as for eventual comparison with higher-latitude settings. Our grab samples and dredge samples of bivalve death assemblages from nine stations in five subtidal habitats in a large marine embayment of Caribbean Panama (Bocas del Toro) provide the first actualistic information on the taphonomic condition of shells in Recent tropical siliciclastic sediments. Focusing on unambiguous damage to bivalve shell interiors, we found that the quality of shell preservation in fine-grained siliciclastics is superb: commonly «10% of specimens are affected by encrustation, boring, edge-rounding fine-scale surface alteration via dissolution, microbioerosion maceration. Pure-carbonate and mixed siliciclastic-carbonate environments containing hard substrata (patch reefs, Halimeda gravelly sand, mud among patch reefs) contain higher numbers of more severely damaged shells (generally >25%) and also higher diversities of fossilizable encrusters and borers. Disarticulation and fragmentation are pervasive across all environments and are probably related to predation rather than to postmortem processes. As in other shallow subtidal study areas, the taxonomic compositions of death assemblages have not been homogenized by postmortem transport but show high spatial fidelity to the distribution of living species. Assemblages from the five sedimentary environments have distinct taphonomic signatures, but the strongest differences are between the two fine-grained, exclusively soft-sediment siliciclastic environments on the one hand and the three environments containing hard substrata on the other. Experimental tests for rates and agents of damage, still in progress, indicate that the most critical environmental variables are exhumation cycles and burial rate. Bivalve death assemblages from Bocas del Toro demonstrate that damage levels in tropical fine-grained siliciclastic environments are much lower than in closely associated reefs and algal sands suggest a less filtered record of biological information.
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Ausich, William I., Elizabeth C. Rhenberg, and David L. Meyer. "Batocrinidae (Crinoidea) from the Lower Mississippian (lower Viséan) Fort Payne Formation of Kentucky, Tennessee, and Alabama: systematics, geographic occurrences, and facies distribution." Journal of Paleontology 92, no. 4 (April 22, 2018): 681–712. http://dx.doi.org/10.1017/jpa.2017.135.
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AbstractThe Batocrinidae are characteristic faunal elements in Lower Mississippian shallow-marine settings in North America. Recent delineation of objectively defined genera allows a reexamination of batocrinid species and their distribution in the Fort Payne Formation (early Viséan, late Osagean), a well-studied array of carbonate and siliciclastic facies. The Fort Payne batocrinid fauna has 14 species assigned to six genera, plus hybrid specimens.Magnuscrinus spinosus(Miller and Gurley, 1895a) is reassigned to its original placement inEretmocrinus. Hybrid specimens (Ausich and Meyer, 1994) are regarded asEretmocrinus magnificus×Eretmocrinus spinosus.Macrocrinus casualisis the dominant species ofMacrocrinusin the Fort Payne, andM.mundulusandM.strotobasilarisare recognized in the Fort Payne Formation for the first time.Magnuscrinus cumberlandensisn. sp. is named, 13 species are designated as junior synonyms, the name for the hybrid specimens is changed toEretmocrinus magnificus×Eretmocrinus spinosus, and the previous occurrences of two species in the Fort Payne are rejected. The Eastern Interior Seaway was a mixed carbonate-siliciclastic setting with both shallow- and deep-water epicontinental sea facies ranging from relatively shallow autochthonous green shales to deep-water turbidite facies.Dizygocrinuswas restricted to shallow-water carbonate and siliciclastic facies,Eutrochocrinuswas restricted to shallow-water carbonate facies, andMagnuscrinuswas restricted to deep-water facies. Species distributions varied fromAbatocrinus steropes,Alloprosallocrinus conicus,Macrocrinus mundulus, andUperocrinus nashvillae, which occurred throughout the Eastern Interior Seaway, to species that were restricted to a single facies.Eretmocrinus magnificus,Alloprosallocrinus conicus, andUperocrinus robustuswere the dominant batocrinids in the Fort Payne Formation.UUID:http://zoobank.org/703aafd8-4c73-4edc-9870-e2356e2d28b8
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Fernandez-Mendiola, P. A., and J. Garcia-Mondejar. "Sedimentation of a Lower Cretaceous (Aptian) coral mound complex, Zaraya Mountains, northern Spain." Geological Magazine 126, no. 4 (July 1989): 423–34. http://dx.doi.org/10.1017/s0016756800006609.
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AbstractA Lower Cretaceous mixed carbonate-siliciclastic sequence is well exposed in the Zaraya Mountains in Guipuzcoa Province, northern Spain. The sequence begins with interfingering deltaic platform facies and marine patch-reef carbonates. This unit is dominated by mudstones and sandstone with minor interbeds of shallow-water carbonates (calcareous mudstones and sandstones and grainstone-packstones). A thick mixed carbonate-terrigenous unit overlies the siliciclastics and is composed principally of limestones and marls. Periodic influx of terrigenous sediments over a dominantly carbonate sea-floor gave rise to repeated cycles typical of a mixed shallow-water platform. Demise of the southerly derived deltaic input allowed the development of a mainly carbonate third unit. Large (several metres across) bioherms resulted from high in situ organic productivity (mechanical breakage of bioclasts, algal-induced precipitation, trapping and baffling of lime mudstone). The mounds grew making up a coral carbonate mound complex. This prograded to the south, towards a small backreef basin, and slightly retreated in its forereef margin. A period of tectonic instability is thought to have been responsible for the drowning of the shallow-water complex, which was unable to keep pace with relative sea-level rise.
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Dunbar, Gavin B., and Gerald R. Dickens. "Late Quaternary shedding of shallow-marine carbonate along a tropical mixed siliciclastic-carbonate shelf: Great Barrier Reef, Australia." Sedimentology 50, no. 6 (December 2003): 1061–77. http://dx.doi.org/10.1046/j.1365-3091.2003.00593.x.
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NOVAK, V., and W. RENEMA. "LARGER FORAMINIFERA AS ENVIRONMENTAL DISCRIMINATORS IN MIOCENE MIXED CARBONATE-SILICICLASTIC SYSTEMS." PALAIOS 30, no. 1 (February 23, 2015): 40–52. http://dx.doi.org/10.2110/palo.2013.081.
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Zand-Moghadam, Hamed, Reza Moussavi-Harami, Asadollah Mahboubi, and Hoda Bavi. "Comparison of Tidalites in Siliciclastic, Carbonate, and Mixed Siliciclastic-Carbonate Systems: Examples from Cambrian and Devonian Deposits of East-Central Iran." ISRN Geology 2013 (June 16, 2013): 1–21. http://dx.doi.org/10.1155/2013/534761.
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For the comparison of lithofacies in siliciclastic, carbonate, and mixed siliciclastic-carbonate tidal systems, three successions including Top Quartzite (Lower-Middle Cambrian), Deranjal Formation (Upper Cambrian), and Padeha Formation (Lower-Middle Devonian) in the north of Kerman and Tabas regions (SE and E central Iran) were selected and described, respectively. Lithofacies analysis led to identification of 14 lithofacies (Gcm, Gms, Gt, Sp, St, Sh, Sl, Sr, Sm, Se, Sr(Fl), Sr/Fl, Fl(Sr), and Fl) and 4 architectural elements (CH, LA, SB, and FF) in the Top Quartzite, 7 lithofacies (Dim, Dp, Dr, Ds, Dl, Dr/Dl, and Fcl) and 2 architectural elements (CH, CB) in the Deranjal Formation, and 17 lithofacies (Sp, St, Sh, Sl, Sr, Se, Sr(Fl), Sr/Fl, Fl(Sr), Fl, Dr, Ds, Sr/Dl, El, Efm, Efl, and Edl) and 5 architectural elements (CH, LA, SB, FF, and EF) in the Padeha Formation that have been deposited under the influence of tides. The most diagnostic features for comparison of the three tidalite systems are sedimentary structures, textures, and fabrics as well as architectural elements (lithofacies association). The CH element in siliciclastics has the highest vertical thickness and the least lateral extension, while in the carbonate tidalites, it has the least vertical thickness and the most lateral extension compared to in other systems.
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Qayyum, Farrukh, Octavian Catuneanu, and Crépin Eric Bouanga. "Sequence stratigraphy of a mixed siliciclastic-carbonate setting, Scotian Shelf, Canada." Interpretation 3, no. 2 (May 1, 2015): SN21—SN37. http://dx.doi.org/10.1190/int-2014-0129.1.
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During the Jurassic Period, a large-scale carbonate bank (Abenaki Formation) and a siliciclastic (Sable) delta coexisted in North America. Conventionally, carbonate systems (in situ) are separated from siliciclastic systems (transported) because of their contrasting origin. However, we developed a case study to show that the basic principles of sequence stratigraphy remain applicable. We integrated the results obtained from a regional 2D study and a detailed follow-up study using 3D seismic data of the Scotian Shelf, Canada. The results were integrated with the prepared Wheeler diagrams, and a unified sequence stratigraphic framework was proposed. We determined that two second-order sequences were developed on a larger scale during the Jurassic Period. The first sequence developed during the transition from a ramp to rimmed margin. The second sequence developed during the evolution from a rimmed to ramp margin. These sequences formed a distinct stratigraphic style throughout the Scotian Shelf. The siliciclastic supply varied from the northeast to the southwest depending on the studied site; however, the regions close to the siliciclastic supply contained well-defined clinoform patterns. The topsets of such clinoforms were mostly eroded. Their directions were also found to be different than the carbonate-related clinoform geometries. Most of the carbonates were developed; as such, they kept up and prograded toward a backreef margin during the rimming stages. The second-order sequences were further subdivided into four third-order sequences. These were studied using the 3D seismic data and were found to contain several barrier reefs that could have stratigraphic exploration potential in the Penobscot area.
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Molyneux, Stephen, Jeff Goodall, Roisin McGee, George Mills, and Birgitta Hartung-Kagi. "Observations on the Lower Triassic petroleum prospectivity of the offshore Carnarvon and Roebuck basins." APPEA Journal 56, no. 1 (2016): 173. http://dx.doi.org/10.1071/aj15014.
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Why are the only commercial hydrocarbon discoveries in Lower Triassic and Permian sediments of the western margin of Australia restricted to the Perth Basin and the Petrel Sub-basin? Recent regional analysis by Carnarvon Petroleum has sought to address some key questions about the Lower Triassic Locker Shale and Upper Permian Chinty and Kennedy formations petroleum systems along the shallow water margin of the Carnarvon and offshore Canning (Roebuck/Bedout) basins. This paper aims to address the following questions:Source: Is there evidence in the wells drilled to date of a working petroleum system tied to the Locker Shale or other pre-Jurassic source rocks? Reservoir: What is the palaeogeography and sedimentology of the stratigraphic units and what are the implications for the petroleum systems?The authors believed that a fresh look at the Lower Triassic to Upper Permian petroleum prospectivity of the North West Shelf would be beneficial, and key observations arising from the regional study undertaken are highlighted:Few wells along a 2,000 km area have drilled into Lower Triassic Locker Shale or older stratigraphy. Several of these wells have been geochemically and isotopically typed to potentially non Jurassic source rocks. The basal Triassic Hovea Member of the Kockatea Shale in the Perth Basin is a proven commercial oil source rock and a Hovea Member Equivalent has been identified through palynology and a distinctive sapropelic/algal kerogen facies in nearly 16 wells that penetrate the full Lower Triassic interval on the North West Shelf. Samples from the Upper Permian, the Hovea Member Equivalent and the Locker Shale have been analysed isotopically indicating –28, –34 and –30 delta C13 averages, respectively. Lower Triassic and Upper Permian reservoirs are often high net to gross sands with up to 1,000 mD permeability and around 20% porosity. Depositional processes are varied, from Locker Shale submarine canyon systems to a mixed carbonate clastic marine coastline/shelf of the Upper Permian Chinty and Kennedy formations.
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Zecchin, Massimo, and Octavian Catuneanu. "High-resolution sequence stratigraphy of clastic shelves VI: Mixed siliciclastic-carbonate systems." Marine and Petroleum Geology 88 (December 2017): 712–23. http://dx.doi.org/10.1016/j.marpetgeo.2017.09.012.
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Lucas, Spencer G., William A. DiMichele, Karl Krainer, James E. Barrick, Daniel Vachard, Michael P. Donovan, Cindy Looy, Hans Kerp, and Dan S. Chaney. "The Pennsylvanian System in the Sacramento Mountains, New Mexico, USA." Smithsonian Contributions to Paleobiology, no. 104 (February 22, 2021): iv—215. http://dx.doi.org/10.5479/si.14079809.v1.
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Pennsylvanian sedimentary rocks in the Sacramento Mountains, New Mexico, comprise an ~1 km thick stratigraphic section. The Morrowan-Desmoinesian Gobbler Formation was deposited by shallow marine processes in and near the Alamo clastic trough. In this trough, the Desmoinesian-Missourian Gray Mesa Formation (Bug Scuffle Member, Gobbler Formation) is a relatively thin unit (Space History Member) representing the glacioeustatic Amado event. The Missourian-Virgilian Beeman Formation includes the lower, siliciclastic Indian Wells Canyon Member and overlying, carbonate-rich Horse Ridge Member. The Virgilian Holder Formation consists of algal bioherms (Little Dry Canyon Member) overlain by the mixed carbonate-siliciclastic Mill Ridge Member. The Virgilian-Wolfcampian Bursum Formation is mixed siliciclastic-carbonate strata that represent shallow marine and nonmarine paleoenvironments. Animal and plant remains occur throughout the section. Unit age determinations are primarily based on conodont faunas recovered from the Gobbler, Gray Mesa, and Beeman Formations. Many conodont faunas correlate with Midcontinent cyclothems. Extensive algal and foraminiferal fossils also were identified in limestones from the section and contributed to age determinations. The Beeman Formation in particular contains an extensive Missourian macroflora. The macroflora is of “mixed” composition, containing typical wetland elements intimately intermixed with taxa indicative of seasonally dry habitats. A seasonally wet-dry background climate is indicated. It is unlikely that droughttolerant plants were transported exclusively from “uplands.” Some plant remains have arthropod-feeding evidence. Previous analyses identified late Paleozoic ice-age glacioeustasy as the primary depositional driver of Pennsylvanian sedimentation in the Sacramento Mountains. We question this because of problems with those analyses and because of ample evidence of local tectonics and microclimate changes as important drivers of sedimentation in this area. Three Pennsylvanian Ancestral Rocky Mountain orogeny tectonic pulses can be identified in the Sacramento Mountains: Morrowan-Atokan, Missourian, and late Virgilian-Wolfcampian.
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Videt, Blaise, and Didier Néraudeau. "Palaeoecology of Cenomanian oysters of the northern margin of the Aquitaine Basin." Bulletin de la Société Géologique de France 178, no. 1 (January 1, 2007): 39–50. http://dx.doi.org/10.2113/gssgfbull.178.1.39.
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Abstract The purpose of this paper is to understand which parameters control the palaeoenvironmental distribution of Middle Cretaceous oysters. To reach this objective, the following two step analysis has been carried out. First, ten major Upper Albian to Lower Turonian outcrops from the northern part of the Aquitain Basin (SW France) (fig. 1) were analysed with respect to their sedimentological and palaeontological features (see fig. 2 for oyster distribution). They represent a time interval corresponding to a 2nd order transgression [Hardenbol et al., 1997; Néraudeau et al., 1997], characterised in the Charentes (North Aquitaine Basin) by a great variety of depositional environments and very rich in oyster assemblages [Videt, 2004]. According to previous authors [Moreau, 1993; Néraudeau et al., 1997; Platel, 1989, 1996], this series can be divided into seven lithological units, A to G, four units (A, B, C and G) being subdivided into two or three subunits (A1 and A2, B1 to B3, C1 to C4, G1 and G2). Apart from the sub-units A1 and Tu, which correspond to the Late Albian and Early Turonian respectively, all the lithological sub-units A2 to G2 correspond to the Cenomanian series. A and B belong to the lower Cenomanian, C1 to C3 to the middle Cenomanian, and C4 to G2 to the Upper Cenomanian. In terms of palaeoenvironments, unit A is considered as deposits of a sandy estuary (with local lignite layers) [Néraudeau et al., 2002, 2003; Perrichot, 2003], and unit B as shallow subtidal sand dunes [Vullo et al., 2003]. Unit C corresponds to the optimal development of a carbonate platform with rudists [Chéreau et al., 1997], unit D to a marly open shelf marly facies, unit E to an oyster bank mainly composed of Pycnodonte biauriculata [Dhondt, 1984], unit F to a moderately deep bioclastic facies colonised by rudist Ichthyosarcolites triangularis and, unit G, which forms progressively marly up-section, to progressive platform flooding at the Cenomanian-Turonian boundary. From the analysis of these different lithological units and subunits, the North Aquitaine Basin can be considered as a mixed siliciclastic-carbonate platform. Two main depositional systems have been identified, namely an open one and a closed one. The synthetic distribution of twelve kinds of oysters biofacies (bf1 to bf12) described in these units and subunits is summed up in figure 3 according to depositional type, lithology and depth. Based on the palaeoenvironmental distribution of Middle Cretaceous oysters in the northern part of the Aquitain Basin, the palaeoecological affinities of the nine marine species are discussed regarding seven main parameters i.e., oxygenation, water turbulence, salinity, turbidity, bathymetry, grain size, and substrate consistency (i.e. “hardground” VS “softground”) (fig. 4). Acutostrea aff. incurva (Nilson, 1827) (figs 4, 5h) and Curvostrea rouvillei (Coquand, 1862) (figs 4, 5i) are very rare species with a distribution that is still ambiguous. Apparently they preferred soft substrates and seem to have tolerated lowered oxygen levels. In addition, they are encountered in quiet, deep environments, i.e., the lower infralittoral to circalittoral zones sensu Néraudeau et al. [2001]. Ceratostreon flabellatum (Goldfuss, 1833) (figs 4, 5e) is not a prolific species but was widely distributed all over the carbonate platform. Nevertheless it is mainly marine and located in the infralittoral zone [sensu Néraudeau et al., 2001]. Gyrostrea delettrei (Coquand, 1862) (figs 4, 5g) might have been very widespread but is very rare. It was most abundant in marginal marine environments where it was the sole oyster that tolerated brackish water conditions. Pycnodonte biauriculata (Lamarck, 1819) (figs 4, 5d), in spite of its very short stratigraphic range (Naviculare Ammonite Zone), colonised a wide variety of environments. It is mainly a relatively medium water species (regarding to other species) [Stenzel, 1971; Harry, 1985; Freneix and Viaud, 1986], from the lower infralittoral zone [sensu Néraudeau et al., 2001] but it needed food-laden currents. Pycnodonte vesicularis (Lamarck, 1819) (figs 4, 5f) is also an ubiquitous species. However, in contrast to Pycnodonte biauriculata, it preferred deep, soft substrates (circalittoral and deeper ones? [Néraudeau and Villier, 1997]). Rastellum carinatum (Lamarck, 1806) (figs 4, 5c) and Rastellum diluvianum (Linne, 1767) (figs 4, 5b) exhibit an identical distribution pattern in spite of the fact that R. diluvianum is more selective than Rastellum carinatum. Carter [1968], Jablonsky and Lutz [1980] and Freneix and Viaud [1986] have already demonstrate that these species do not tolerate turbulent conditions but are particularly adapted to quiet water and soft substrates. The two species also do not tolerate salinity variations. Rhynchostreon suborbiculatum (Lamarck, 1801) (figs 4, 5a) is the most ubiquitous species in the Cenomanian of the Aquitain Basin. Videt and Néraudeau [2003] and Videt [2004] have already defined the parameters that affected its shape and its abundance. As the species does not occur in brackish water deposits, salinity seems to have been a major factor limiting its distribution.
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Tournadour, E., S. J. Jorry, S. Etienne, J. Collot, M. Patriat, M. K. BouDagher-Fadel, F. Fournier, et al. "Neogene to Quaternary evolution of carbonate and mixed carbonate-siliciclastic systems along New Caledonia's eastern margin (SW Pacific)." Marine Geology 438 (August 2021): 106524. http://dx.doi.org/10.1016/j.margeo.2021.106524.
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Walker, Wylie, Zane R. Jobe, J. F. Sarg, and Lesli Wood. "Progradational slope architecture and sediment distribution in outcrops of the mixed carbonate-siliciclastic Bone Spring Formation, Permian Basin, west Texas." Geosphere 17, no. 4 (June 10, 2021): 1268–93. http://dx.doi.org/10.1130/ges02355.1.
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Abstract Sediment transport and distribution are the keys to understanding slope-building processes in mixed carbonate-siliciclastic sediment routing systems. The Permian Bone Spring Formation, Delaware Basin, west Texas, is such a mixed system and has been extensively studied in its distal (basinal) extent but is poorly constrained in its proximal upper-slope segment. Here, we define the stratigraphic architecture of proximal outcrops in Guadalupe Mountains National Park in order to delineate the shelf-slope dynamics of carbonate and siliciclastic sediment distribution and delivery to the basin. Upper-slope deposits are predominantly fine-grained carbonate lithologies, interbedded at various scales with terrigenous (i.e., siliciclastic and clay) hemipelagic and gravity-flow deposits. We identify ten slope-building clinothems varying from terrigenous-rich to carbonate-rich and truncated by slope detachment surfaces that record large-scale mass wasting of the shelf margin. X-ray fluorescence (XRF) data indicate that slope detachment surfaces contain elevated proportions of terrigenous sediment, suggesting that failure is triggered by changes in accommodation or sediment supply at the shelf margin. A well-exposed terrigenous-rich clinothem, identified here as the 1st Bone Spring Sand, provides evidence that carbonate and terrigenous sediments were deposited contemporaneously, suggesting that both autogenic and allogenic processes influenced sediment accumulation. The mixing of lithologies at multiple scales and the prevalence of mass wasting acted as primary controls on the stacking patterns of terrigenous and carbonate lithologies of the Bone Spring Formation, not only on the shelf margin and upper slope, but also in the distal, basinal deposits of the Delaware Basin.
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Lavoie, Denis. "Peritidal origin of the Lower Ordovician Upton Group, southern Quebec Appalachians." Canadian Journal of Earth Sciences 29, no. 5 (May 1, 1992): 1106–18. http://dx.doi.org/10.1139/e92-088.
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The Lower Ordovician Upton Group is part of the Cambrian–Ordovician external domain of the Appalachian Orogen of southern Quebec. It is a mixed carbonate–siliciclastic–volcanic succession occurring within flyschoid sediment of the Lower Cambrian Granby Nappe. The bulk of the Upton Group is a grey, massive, recrystallized limestone of probable peritidal and shallow subtidal origin. Associated siliciclastic lithofacies are typical of peritidal and outer-shelf settings. The proposed peritidal paleoenvironmental model differs from previous interpretations and indicates that it is unlikely that the Upton Group is a slab derived from the Ordovician continental margin which has slid into the Granby Nappe.
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Xu, Wei, Zhengyu Li, Huiyong Li, Can Zhang, Meng Zhao, Hongliu Zeng, and Yiran Ding. "The relationship between source supply and mixed deposition of siliciclastic and carbonate: First to second member of the Shahejie Formation, Paleogene, Bohai Sea area, China." Interpretation 9, no. 2 (April 21, 2021): SC45—SC52. http://dx.doi.org/10.1190/int-2020-0182.1.
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There are various types of mixed siliciclastic-carbonate sediments developed in the Bohai Sea area during the period of the first to second member of the Shahejie Formation (E2s1-2) of the Paleocene. We have concluded that the period of E2s1-2 was very suitable for the development of carbonate minerals and organisms because of the stable tectonic background, the weak siliciclastic influence of large source systems outside the basin, and the high salinity of the water. There were many local uplifts inside the basin during E2s1-2, and the source area, supply direction, and quantity of the local provenance varied greatly. We summarized that the mixed sediments generally developed in the intermittent and stagnant periods of the source supply, or on the flank or distal end of the source supply direction due to the absence of direct interference of terrigenous clasts. To a large extent, the formation of different types of mixed deposits is controlled by the different spatiotemporal relationship with siliciclastic supply. The background of strong source supply led to the formation of large-scale mixed deposits that were mainly composed of terrigenous clasts. Mixed deposits are mainly composed of organisms and carbonate with relatively large depositional thickness formed on the flank of source supply in the steep slope area. On the flank of source supply in the gentle slope belt, thinner mixed deposits with terrigenous clasts mainly formed and thin-layer carbonate clastic-dominated deposits formed on abandoned deltas. On the uplift of the buried hill far away from the provenance, thick mixed deposits mainly composed of bioclastic were formed whereas fine-grained mixed deposits formed under the low-energy argillaceous background.
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Salazar-Ortiz, Edward A., Daniel Rincón-Martínez, Liliana A. Páez, Sandra M. Restrepo, and Sofía Barragán. "Middle Eocene mixed carbonate-siliciclastic systems in the southern Caribbean (NW colombian margin)." Journal of South American Earth Sciences 99 (April 2020): 102507. http://dx.doi.org/10.1016/j.jsames.2020.102507.
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Soja, Constance M. "Using fossils to identify allochthonous oceanic islands in the ancient geologic record." Paleontological Society Special Publications 6 (1992): 275. http://dx.doi.org/10.1017/s2475262200008352.
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Silurian organisms preserved in southeastern Alaska (Alexander terrane) inhabited marine environments within an island-arc complex during a phase of waning volcanism and are fossilized in a diversity of shallow-marine platform and deep-water deposits. These fossils exhibit a distinctive suite of characteristics and share fundamental similarities with biotas of Paleozoic-Mesozoic age that are preserved in other accreted island terranes of North America. These special attributes reflect the colonization, evolution, and diversification of marine organisms adjacent to subconical/conical volcanic edifices characterized by relatively high rates of subsidence, steep submarine slopes, tectonic instability, and biogeographic isolation. Recognition of these diagnostic features enables many ancient island faunas to be distinguished from those that lived on the craton and enhances differentiation of island biotas from pelagic assemblages that accumulated as oozes in deep ocean basins.Although island faunas exhibit a high degree of variability in taxonomic diversity, levels of endemism, and provincial affinities, many share a significant number of similarities. Several of these shared attributes reflect organismal evolution in biogeographic isolation at island sites separated from continental and other source regions by considerable geographic distances or at locations unfavorably situated with respect to oceanic currents transporting teleplanic larvae. Comparison of Silurian island-arc faunas from Alaska with coeval assemblages from different tectonic settings and with modern volcanic islands shows that oceanic island biotas commonly are characterized by: (1) initially impoverished, normal marine faunas of low diversity and abundance that are preserved in exceptionally thick platform sequences; (2) sequential development of organic structures from fringing to barrier reefs on the outer shelf during thermal subsidence and lateral expansion of the carbonate platform; (3) restricted faunas devoid of normal marine shelly benthos and tolerant of quiet-water conditions, muddy substrates, and fluctuations in salinity, temperature, and oxygen concentrations in back-reef lagoons; (4) extensive taphonomic redistribution of organisms along bathymetric gradients and downslope preservation in debris flows, slumps, and turbidites of mixed fossil assemblages derived from shelf and shelf-margin habitats; (5) rapid lateral and vertical changes in biofacies, reflecting complex depositional systems in fault-block basins; (6) insular biotas with relatively high levels of endemism; (7) complex paleobiogeographic affinities expressed in assemblages that comprise mixtures of taxa from different faunal regions; and (8) relict biotas that may represent the protracted survival of some organisms in island refugia.Because many accreted islands are poorly preserved and highly deformed, recognizing these distinctive features in oceanic island faunas enhances identification of allochthonous volcanic arcs, seamounts, atolls, and hot-spot islands in the ancient geologic record. Using fossils to identify islands in accreted terranes is especially important when island origins of strata are suspected but difficult to prove because calc-alkaline volcano-plutonic rocks or derivative volcanogenic and quartz-poor siliciclastic deposits are absent or not exposed. Hence, relying on fossils to recognize oceanic islands that survived destructive tectonic processes offers an expanded list of geologic criteria to aid in reconstructing plate boundaries marking ancient zones of convergence and to use in unraveling the tectonic history of ocean basins recorded in suspect terranes.
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Mclntyre, C. L., and P. J. Stickland. "SEQUENCE STRATIGRAPHY AND HYDROCARBON PROSPECTIVITY OF THE CAMPANIAN TO EOCENE SUCCESSION, NORTHERN BONAPARTE BASIN, AUSTRALIA." APPEA Journal 38, no. 1 (1998): 313. http://dx.doi.org/10.1071/aj97015.
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The Campanian to Eocene succession of the Northern Bonaparte Basin contains a number of siliciclastic reservoirs which provide alternative targets to the Callovian structural plays that have dominated exploration to date. The succession is part of the Passive Margin Megasequence which extends from the Aptian to the Pliocene, and is traditionally subdivided into the Turnstone, Johnson and Grebe Formations.Prograding deltaics of the Turnstone Formation swamped an incipient Early-Campanian carbonate ramp following a second-order sequence-boundary. Five third-order sequences are recognised within the Turnstone Formation, each dominated by Lowstand (shelf-margin wedge) and Highstand Systems Tract components. A coeval basinal carbonate system resulted in the deposition of marls and lutites distal of the clastic deltaics. In the Early Paleocene, drowning of the clastic system led to the establishment of a productive carbonate ramp. Rare lowstand siliciclastic reservoirs are developed within carbonate-dominated prograding complexes, as incised valley-fill, and possibly within prominent slope canyons. In the Late Paleocene, a third-order transgression drowned the carbonate system. The Early Eocene Grebe sandstones were then deposited as a second-order lowstand package upon a prominent sequence-boundary. Subsequent flooding of the siliciclastic system resulted in the re-establishment of the prograding carbonate ramp system.The morphology of the passive-margin was strongly influenced by the interplay between sediment-supply and subsidence. The predominantly ramp-like geometry of the margin promoted the development of numerous shallow-marine lowstand reservoirs. The hydrocarbon prospectivity of each of these reservoirs is primarily controlled by the magnitude of the subsequent flooding events: Only the largest transgressions resulted in sufficient reduction of depositional energy to isolate the lowstand siliciclastics.Vertical migration remains the critical risk for all passive margin plays, as the reservoirs are separated from the Late Jurassic and Early Cretaceous source kitchens by up to one kilometre of claystone dominated sequences. None-the-less, the widespread occurrence of shallow hydrocarbon shows in the greater Bonaparte Basin indicates that Neogene faulting does provide locally valid migration pathways into post-rift reservoirs.
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Álvaro, J. Javier, Cristina González-Gómez, and Daniel Vizcaïno. "Paleogeographic patterns of the Cambrian-Ordovician transition in the southern Montagne Noire (France) : preliminary results." Bulletin de la Société Géologique de France 174, no. 3 (May 1, 2003): 217–25. http://dx.doi.org/10.2113/174.3.217.
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Abstract The Cambrian-Ordovician transition in the southern Montagne Noire records a major siliciclastic regressive trend of prograding shoaling complexes (the La Dentelle Formation), separating two transgressive storm-dominated sedimentary systems of mixed (carbonate-siliciclastic) deposits. The latter comprise the underlying La Gardie and Val d’Homs Formations, and the overlying Mounio Formation, all of them displaying evidence of an important synsedimentary tectonic activity. Isolated settings of carbonate productivity, located on intra-shelf ramps and horsts, contain the richest and diversified faunistic communities comprising trilobites, echinoderms, conodonts, carbonate- and phosphate-shell brachiopods, sponge spicules, etc. Although the Cambrian-Ordovician transition of the southern Montagne Noire did not record volcanic events but a rather distensive regime inducing paleotopographies, the latter may reflect a distinct extensional regime recorded in other earliest Ordovician platforms of the French Massif Central, involving oceanization and a major magmatic activity.
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Chen, Hehe, Xiaomin Zhu, Ruisheng Shi, and Zili Zhang. "Seismic geomorphology of shoal-water deltaic and mixed carbonate-siliciclastic beach-bar systems in hanging wall of rift basins: Paleogene of the Raoyang Sag, Bohai Bay Basin, China." Interpretation 8, no. 2 (May 1, 2020): SF1—SF19. http://dx.doi.org/10.1190/int-2019-0108.1.
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Recent studies of ancient rift basins focus on the tectonosedimentary models, which emphasize the control of tectonics on the distribution and evolution of depositional systems in rift basins, whereas these studies seldom address stratigraphic dominated depositional models. Compared to footwall depositional systems, hanging wall depositional systems are especially underexplored due to their fine-grained, thin-layered, and widely distributed features. We integrated seismic data, cores, and well logs to define the dispersal of hanging wall depositional systems that are related to the fluctuation of lacustrine level in the late synrift and postrift stages. We identified one third-order sequence (SQ1) on the seismic reflection data and subdivided five fourth-order sequences (SSQ1–SSQ5) based on the features of parasequence sets. The strata in SQ1 record a complete regressive and progressive lacustrine process. We interpreted shoal-water deltaic systems and mixed carbonate-siliciclastic beach-bar systems in the SQ1. Within SSQ1 and SSQ2, sediments fed from the northwest, west, and southwest, and developed shoal-water deltaic systems with an average width range of the distributary channel belts within 680–1220 m. In SSQ3, beach-bar systems gradually changed from clastic beach bars to mixed carbonate-siliciclastic beach bars in a basinward direction. Clastic beach-bar systems and mixed carbonate-siliciclastic beach-bar systems were extending north–northeast with an average length of approximately 3.5–8 km and a width of 1–4 km. For those in SSQ4 and SSQ5, shoal-water deltaic systems prograded into the lacustrine, and distributary channel belts occur with an average width range within 520–880 m. We developed a spatial and temporal quantitative evaluation of deltaic and beach-bar reservoirs within a third-order sequence on the hanging wall dip slope, and it has potential worldwide implications for other hanging wall dip slopes in rift basins.
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Sun, X. W. "PREDICTION OF CARBONATE RESERVOIRS AND TRAPS BY APPLYING SEQUENCE STRATIGRAPHY IN THE EASTERN WARBURTON BASIN, SOUTH AUSTRALIA." APPEA Journal 38, no. 1 (1998): 380. http://dx.doi.org/10.1071/aj97018.
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The Early Palaeozoic eastern Warburton Basin unconformably underlies the Cooper and Eromanga Basins. Four seismic sequence sets (I−IV) are interpreted. Among them, sequence set II is subdivided into four Cambro-Ordovician depositional sequences. Sequence 1, the oldest, is a shallow shelf deposit that occurs only in the Gidgealpa area. Sequences 2 and 3 were deposited in a wider area; from west to east, environments varyied from deep siliciclastic ramp, carbonate inner-shelf, peritidal, shelf edge, and slope-to-basin. Their seismic reflection configurations are high-amplitude, regionally parallel-continuous, layered patterns, locally mounded geometry, as well as divergent-fill patterns. Sequence 4, the youngest, was deposited in a mixed siliciclastic and carbonate, storm-dominate shelf. Its seismic reflection configurations are moderate amplitude, parallel-layered patterns, decreasing in amplitude upwards.Boundaries between the four sequences generated good secondary porosity in the carbonates. Karst development is interpreted to have generated much of this porosity in shelf and peritidal carbonates, and carbonate build-ups. Shoal-water sandy limestone and calcareous sandstone of Sequence 4 may be other potential reservoir rocks. Potential source rocks comprise mudstone and shale of slope and basin lithofacies. There are two kinds of stratigraphic trap. One is in Sequences 2 and 3, associated with high-relief carbonate build-ups encased in lagoonal mudstone and shelf edge sealed by transgressive siltstone and shale. The other is a transgressive marine shale enclosing porous dolostone of the karstified Sequence 1. In addition, petroleum may have migrated from Permian source rocks of the Cooper Basin to karstified carbonate reservoirs of the Warburton Basin at unconformities.
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Jenkins, Chelsea E., and Steven M. Holland. "Continental-scale biogeographic variation: provinces versus gradients in the Upper Ordovician of Laurentia." Paleobiology 42, no. 3 (May 6, 2016): 410–25. http://dx.doi.org/10.1017/pab.2015.56.
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AbstractAlthough provinces are widely used to delimit large-scale variations in biotic composition, it is unknown to what extent such variations simply reflect large-scale gradients, much as has been shown at smaller scales for communities. We examine here whether four previously described Middle and Late Ordovician provinces on Laurentia are best described as distinct provinces or as biotic gradients through a combination of the Paleobiology Database and new field data. Both data sets indicate considerable overlap in faunal composition, with spatial patterns in Jaccard similarity, quantified Jaccard similarity, and nonmetric multidimensional scaling ordination structure that correspond to variations in substrate type, specifically from carbonate-dominated strata in western Laurentia to mixed carbonate–siliciclastic strata in the midcontinent to siliciclastic-dominated rocks in easternmost Laurentia. Because sampling was limited to shallow-subtidal settings, this gradient cannot be attributed to variations in water depth. Likewise, geographic distance accounts for only a quarter of the variation in faunal composition. This cross-continent faunal gradient increases in strength into the early Late Ordovician, and appears to represent increased siliciclastic influx into eastern Laurentia during the Taconic orogeny. These results raise the question of whether biogeographic provinces may be in general better interpreted and analyzed as biotic gradients rather than as discrete entities.
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Dinauer, Ashley, and Alfonso Mucci. "Spatial variability in surface-water <i>p</i>CO<sub>2</sub> and gas exchange in the world's largest semi-enclosed estuarine system: St. Lawrence Estuary (Canada)." Biogeosciences 14, no. 13 (July 6, 2017): 3221–37. http://dx.doi.org/10.5194/bg-14-3221-2017.
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Abstract. The incomplete spatial coverage of CO2 partial pressure (pCO2) measurements across estuary types represents a significant knowledge gap in current regional- and global-scale estimates of estuarine CO2 emissions. Given the limited research on CO2 dynamics in large estuaries and bay systems, as well as the sources of error in the calculation of pCO2 (carbonic acid dissociation constants, organic alkalinity), estimates of air–sea CO2 fluxes in estuaries are subject to large uncertainties. The Estuary and Gulf of St. Lawrence (EGSL) at the lower limit of the subarctic region in eastern Canada is the world's largest estuarine system, and is characterized by an exceptional richness in environmental diversity. It is among the world's most intensively studied estuaries, yet there are no published data on its surface-water pCO2 distribution. To fill this data gap, a comprehensive dataset was compiled from direct and indirect measurements of carbonate system parameters in the surface waters of the EGSL during the spring or summer of 2003–2016. The calculated surface-water pCO2 ranged from 435 to 765 µatm in the shallow partially mixed upper estuary, 139–578 µatm in the deep stratified lower estuary, and 207–478 µatm along the Laurentian Channel in the Gulf of St. Lawrence. Overall, at the time of sampling, the St. Lawrence Estuary served as a very weak source of CO2 to the atmosphere, with an area-averaged CO2 degassing flux of 0.98 to 2.02 mmol C m−2 d−1 (0.36 to 0.74 mol C m−2 yr−1). A preliminary analysis revealed that respiration (upper estuary), photosynthesis (lower estuary), and temperature (Gulf of St. Lawrence) controlled the spatial variability in surface-water pCO2. Whereas we used the dissociation constants of Cai and Wang (1998) to calculate estuarine pCO2, formulations recommended for best practices in open ocean environments may underestimate pCO2 at low salinities, while those of Millero (2010) may result in overestimates.
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Tâmega, Frederico Tapajós de Souza, Paula Spotorno De Oliveira, Ricardo Coutinho, and Davide Bassi. "Taxonomic assessment of fossil Holocene coralline red algae (Rhodophyta, Corallinales, Hapalidiales) from southwestern Atlantic." Phytotaxa 245, no. 4 (February 4, 2016): 237. http://dx.doi.org/10.11646/phytotaxa.245.4.1.
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Holocene shallow-water carbonate and mixed siliciclastic-carbonate deposits from the Arraial do Cabo Bay, Brazil, southwestern Atlantic, contain well-preserved coralline red algae. These comprise four species of three genera representing the subfamilies Lithophylloideae, Mastophoroideae and Melobesioideae: Lithophyllum pustulatum, Spongites fruticulosus, Spongites yendoi, Mesophyllum engelharti. Geniculate corallines are present as algal debris. This study represents the first fossil record of these species in southwestern Atlantic Ocean. They inhabited the studied area since at least 13.000 years and are still thriving in the present-day assemblages. Only L. pustulatum and S. fruticulosus have old fossil records traced back into the Oligocene from the Mediterranean region. From ca. 3.000 years ago these species thrive in intertidal settings along the southwestern Atlantic Ocean coasts, which have been characterized by a regressive sea-level trend.
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Mancini, Ernest A., and Berry H. Tew. "Recognition of maximum flooding events in mixed siliciclastic-carbonate systems: Key to global chronostratigraphic correlation." Geology 25, no. 4 (1997): 351. http://dx.doi.org/10.1130/0091-7613(1997)025<0351:romfei>2.3.co;2.
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Lowe, David G., R. W. C. Arnott, Godfrey S. Nowlan, and A. D. McCracken. "Lithostratigraphic and allostratigraphic framework of the Cambrian–Ordovician Potsdam Group and correlations across Early Paleozoic southern Laurentia." Canadian Journal of Earth Sciences 54, no. 5 (May 2017): 550–85. http://dx.doi.org/10.1139/cjes-2016-0151.
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The Potsdam Group is a Cambrian to Lower Ordovician siliciclastic unit that crops out along the southeastern margins of the Ottawa graben. From its base upward, the Potsdam consists of the Ausable, Hannawa Falls, and Keeseville formations. In addition, the Potsdam is subdivided into three allounits: allounit 1 comprises the Ausable and Hannawa Falls, and allounits 2 and 3, respectively, the lower and upper parts of the Keeseville. Allounit 1 records Early to Middle Cambrian syn-rift arkosic fluvial sedimentation (Ausable Formation) with interfingering mudstone, arkose, and dolostone of the marine Altona Member recording transgression of the easternmost part of the Ottawa graben. Rift sedimentation was followed by a Middle Cambrian climate change resulting in local quartzose aeolian sedimentation (Hannawa Falls Formation). Allounit 1 sedimentation termination coincided with latest(?) Middle Cambrian tectonic reactivation of parts of the Ottawa graben. Allounit 2 (lower Keeseville) records mainly Upper Cambrian quartzose fluvial sedimentation, with transgression of the northern Ottawa graben resulting in deposition of mixed carbonate–siliciclastic strata of the marine Rivière Aux Outardes Member. Sedimentation was then terminated by an earliest Ordovician regression and unconformity development. Allounit 3 (upper Keeseville) records diachronous transgression across the Ottawa graben that by the Arenigian culminated in mixed carbonate–siliciclastic, shallow marine sedimentation (Theresa Formation). The contact separating the Potsdam Group and Theresa Formation is conformable, except locally in parts of the northern Ottawa graben where the presence of localized islands and (or) coastal salients resulted in subaerial exposure and erosion of the uppermost Potsdam strata, and accordingly unconformity development.
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Tomassetti, Laura, and Marco Brandano. "Sea level changes recorded in mixed siliciclastic–carbonate shallow-water deposits: The Cala di Labra Formation (Burdigalian, Corsica)." Sedimentary Geology 294 (August 2013): 58–67. http://dx.doi.org/10.1016/j.sedgeo.2013.05.005.
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Bilotte, Michel, Laurent Koess, and Elie-Jean Debroas. "Relationships between tectonics and sedimentation on the northeastern margin of the Subpyrenean trough during the late Santonian." Bulletin de la Société Géologique de France 176, no. 5 (September 1, 2005): 443–55. http://dx.doi.org/10.2113/176.5.443.
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Abstract In the eastern part of the Aquitaine Basin and to the south of the Toulouse high, the Subpyrenean trough is a narrow trench oriented N110°E to N130° E. The deposits on the northeastern side of this depression are preserved in the autochthonous Mesozoic cover of the Variscan Mouthoumet Massif, but also in the parautochthonous or allochthonous tectonic units that fringe to the north (Camps – Peyrepertuse slice, fig. 2) the North Pyrenean frontal thrust. From the Middle Cenomanian to the Lower Santonian included (96 to 85 Ma ago), the sedimentation in the Mouthoumet Massif indicates shallow marine carbonate or mixed (carbonate to terrigenous) conditions. The different facies depend mainly on two parameters : the variations of the accommodation space for sedimentation and the location of the numerous rudist buildups. The deposits are first organized in a homoclinal ramp until the Turonian. From the Coniacian up to the early Santonian, drowned platform patterns prevail. During the late Santonian and more precisely around 85 Ma with an other event around 84 Ma, the Mouthoumet Massif and its cover broke up under tectonic stresses. Positive and negative topographies reactivate the Variscan fault system. Platform – slope/basin morphologies substituted the preceeding ramp and drowned platform morphology. Looking to the south and in the direction N120°E, the distal slope received gravitational and turbiditic sediments called the Grès de Labastide (fig. 7). The sediment supply shifted from north to south and from east to west. To the north of this slope, the platform itself broke up into a mosaic of rhomboedric blocks, leading to a graben and horst morphology. Those units are clearly different according to the character of their sedimentary facies, deltaic or reefal (Montagne des Cornes, Calcaires de Camps – Peyrepertuse). The detailed stratigraphic and sedimentologic studies of some of these systems reveal a tectono-sedimentary evolution involving two successive cycles Ss1 (lower Upper Santonian) and Ss2 (Uppermost Santonian). In the western part of the Mouthoumet Massif this cyclic evolution is recorded from south to north, on the Parahou slope, the Rennes-les-Bains graben and the Bugarach horst. The lower cycle Ss1, located on the Rennes-les-Bains graben, is approximatively 85 Ma to 84 Ma in age. It starts with reworked deposits (lowstand systems tract) made up of sometimes several m3 elements derived from former sedimentary deposits (from Turonian up to Lower Santonian) even when the same deposits are in place on the adjacent horsts (e.g. the eastern horst of Bugarach). Those reworked deposits fill the bottom of the graben, principally in the transit zones (debris-flows of the Conglomerat de la Ferrière), or in the Parahou slope (slumps and debris-flows of the Cascade des Mathieux); then the deltaic complex of Rennes-les-Bains covers the older chaotic deposits; the blue marls and the overlying sandy facies (transgressive and highstand systems tracts) related to prodelta and deltafront deposits represent the infilling of the Rennes-les Bains graben. The upper cycle Ss2 developed probably between 84 Ma to 83,5 Ma; its geographical extension overlaps the limits of the lower cycle (e.g. the Bugarach horst), but its sedimentary organisation is still the same including: on the Parahou slope debris-flow and intrabasinal reworking (Conglomérat des Gascous: lowstand systems tract); on the northern platform transgressive and highstand systems tracts, present in the Montagne des Cornes delta where the Marnes bleues de Sougraigne represent the prodelta deposits, and the terrigenous and rudist buildups of the delta front deposits (fig.7). The final infilling results from the spreading from NE to SW, of the (estuarine ? to) fluvial deposits of the Grès d’Alet Formation at around 83 Ma. In the eastern part of the Mouthoumet Massif, sedimentary development is punctuated by tectonic events. Nevertheless, it is possible to identify in some outcrops the main elements of the two tectono-sedimentary cycles. – The cycle Ss1 is partly preserved in the genetic sequence which links the Calcaires de Camps-Peyrepertuse (shelf margin wedge systems tract) and the Marnes du Pla de Sagnes (transgressive systems tract). The cycle Ss2 is only known through different facies of the Grès de Labastide Formation: reworked deposits on the slope; coarse-grained silicoclastic deposits on the transit zones. – In the cycle Ss1 differences appear between the western and the eastern parts of the Mouthoumet massif. When in the western area deltaic conditions prevailed, in the eastern area a shallow carbonate and buildup facies developed. Such differences disappear in the cycle Ss2 by the general establishment of fore slope deltaic deposits. The geodynamic reconstruction resulting from plate kinematics indicates a major change between the early Coniacian (89 Ma) and the Middle Campanian (79 Ma), when the sinistral/divergent motion of Iberia with respect to stable Europe turned to a dextral/convergent movement. The tectono-sedimentary events presented here took place during this period (85 Ma to 83 Ma). The tectono-sedimentary evolution of the subpyrenean trough and the shift of the European and Iberian plates are thought to be intimately linked. The new chronological and geodynamical data proposed herein show that the genesis and the evolution of the subpyrenean sedimentary processes related to the northern Aquitanian margin of the Subpyrenean trough allow to draw some basic conclusions: – the opening of the Subpyrenean trough occurred in two steps, the first around 85 Ma and the second around 84 Ma; – this caused a change in the sedimentary setting with platform environments replacing the earlier ramp geometry; – the Subpyrenean trough formed and evolved under transtensive tectonic conditions; – during the late Santonian two tectono-eustatic sequences marked the former stages of the eastward opening and infilling of this basin; – the diachronous infilling which began here around 83,5 Ma prograded to the western Plantaurel and Petites-Pyrénées area; – no significant northward shifting of the depositional-axis of the Senonian basins occurred; – only a gradual westward shift of the depositional centers, along the subpyrenean direction of the slope area (N110°E to N130°E) was noticed.
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Kamali, M. R., N. M. Lemon, and S. N. Apak. "POROSITY GENERATION AND RESERVOIR POTENTIAL OF OULDBURRA FORMATION CARBONATES, OFFICER BASIN, SOUTH AUSTRALIA." APPEA Journal 35, no. 1 (1995): 106. http://dx.doi.org/10.1071/aj94007.
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Porosity generation and reservoir potential of the early Cambrian Ouldburra Formation in the eastern Officer Basin is delineated by combining petrographical, petrophysical and sedimentological studies. The shallow marine Ouldburra Formation consists of carbonates, mixed carbonates and clastics, clastics and evaporites. Detailed analysis of more than 100 samples shows that dolomitisation resulted in substantial secondary porosity development within the carbonates. Secondary porosity has also been generated within the mixed siliciclastic-carbonate zone by carbonate matrix and grain dissolution as well as by dolomitisation. Prospective reservoir units correspond to highstand shallow marine facies where short periods of subaerial exposure resulted in diagenetic changes.Sedimentary facies and rock character indicate that sabkha and brine reflux models are applied to dolomitisation within the Ouldburra Formation. Dolomite mainly occurs in two stages: common anhedral dolomites formed early by replacement of pre-existing limestone, and saddle dolomite and coarse crystalline dolomite formed during the late stages of burial diagenesis, associated with hydrocarbon shows. The dolomite reservoirs identified are ranked on the basis of their porosity distribution and texture into groups I to IV. Dolomites with rank I and II exhibit excellent to good reservoir characteristics respectively.The Ouldburra Formation shows many depositional and diagenetic similarities to the Richfield Member of the Lucas Formation in the Michigan Basin of the USA. Substantial oil and gas production from middle Devonian shallow water to sabkha dolomites makes the Richfield Member an attractive reservoir analogue to the Ouldburra Formation.
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RATCLIFFE, K. T., and A. T. THOMAS. "Carbonate depositional environments in the late Wenlock of England and Wales." Geological Magazine 136, no. 2 (March 1999): 189–204. http://dx.doi.org/10.1017/s0016756899002538.
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Based on outcrop studies and borehole data, six bedded lithofacies and two reef types are recognized within the Much Wenlock Limestone Formation of the English Midlands and Welsh Borderland. The lithofacies are interpreted to represent a series of carbonate shelf environments extending from below storm wave-base to well above fair weather wave-base. In common with many other shallow marine carbonate depositional systems, the principal controls on lithofacies development were hydrodynamic energy, the supply of fine clastic sediment, and patterns of colonization of the sea floor by organisms. Reef distribution was probably controlled by the nature of the substrate, water circulation, and rate of siliciclastic sedimentation. A depositional model is proposed which incorporates biostratigraphical evidence suggesting that the formation youngs to the west on the northern part of the shelf. Deposition of the Much Wenlock Limestone Formation there began in the West Midlands, where 12 m of microbial limestone were lain down in a mid-shelf setting during a local regression. The remainder of the shelf was dominated by low energy siliciclastic deposition at that time. The West Midlands then returned to somewhat deeper water, lower energy deposition, the resulting impure calcareous muds becoming diagenetically changed into the nodular limestone lithofacies. That lithofacies is commonly overlain successively by the interbedded limestone and silty mudstone lithofacies, and then the crinoidal grainstone lithofacies. This vertical lithofacies sequence is uniform over the entire northern part of the shelf, reflecting a gradual decrease in water depth. The crinoidal grainstone lithofacies was deposited as a wave-influenced carbonate sandbody which prograded from east to west. Lithofacies sequences on the southern shelf are laterally impersistent, probably due to greater tectonic instability and topographical variablity.
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DELPOMDOR, Franck R. A., Archange M. ILAMBWETSI, Fabricío A. CAXITO, and Antonio C. PEDROSA-SOARES. "New interpretation of the basal Bambuí Group, Sete Lagoas High (Minas Gerais, E Brazil) by sedimentological studies and regional implications for the aftermath of the Marinoan glaciation: Correlations across Brazil and Central Africa." Geologica Belgica 23, no. 1-2 (January 4, 2020): 1–17. http://dx.doi.org/10.20341/gb.2019.010.
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Along the preserved southeast border (i.e., the Sete Lagoas High) of the Bambuí basin, the Pedro Leopoldo Member, basal succession of the Sete Lagoas Formation, unconformably overlies the Archean basement, and mostly includes carbonates with thin pelite intercalations and rare ruditic deposits. One of these, the so-called Carrancas conglomerate in its type-section, has been considered one of the lowermost rudite deposits of the Bambuí basin, being frequently ascribed to a Neoproterozoic glaciation. However, our detailed study, based on facies analysis, reveals that the Carrancas conglomerate was deposited by sediment gravity flow currents within the basal Pedro Leopoldo Member. Two outcrop sections in the São José de Lapa and Vespasiano areas, including thirteen abandoned quarry-cut and cliff outcrops, display eight distinct lithofacies (LF1 to LF8) forming a shallowing-upward carbonate ramp succession. It is composed, from the base to the top, by a mixed siliciclastic-carbonate outer ramp distally bounded by a slope-outer ramp system with sediment gravity flow deposits, a deep outer ramp developed below storm-wave base environments, an outer-middle ramp with aragonite pseudomorph crystal fans developed in a CaCO3 oversaturated below storm-wave base environment in suboxic/anoxic conditions. According to published isotope data correlating δ13C trends and values in basal carbonates of the Pedro Leopoldo Member of the Sete Lagoas and Januária highs, the relatively deep outer-slope ramp mixed siliciclastic-carbonate units of the study area appear to be coeval in age with the cap dolostone of shallow-water inner ramp of the Januária High. The absence of a cap dolostone in the Sete Lagoas High could be explained by lack of accommodation space or a regional erosion due to the tectonically driven forebulge uplift of the Sete Lagoas High. The Pedro Leopoldo Member in the Sete Lagoas High was accumulated in a brine-seawater bottom waters under suboxic/anoxic conditions in the relatively deeper portion of the carbonate ramp system, whilst the cap dolostone in the Januária High was developed in oxygenated mixed layer and intermediate water near the surface water in the shallower portion of the carbonate ramp system. Such lateral variations of facies and δ13C fluctuations are similar to those recorded by the cap carbonate sequences of the basal Schisto-Calcaire/Lukala (Sub)Group in the West Congo Belt and the basal Araras Group in the Paraguay Belt, which display a similar wide range of sub-environments like the studied part of the Pedro Leopoldo Member.
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Francis, J. M., G. B. Dunbar, G. R. Dickens, I. A. Sutherland, and A. W. Droxler. "Siliciclastic Sediment Across the North Queensland Margin (Australia): A Holocene Perspective on Reciprocal Versus Coeval Deposition in Tropical Mixed Siliciclastic-Carbonate Systems." Journal of Sedimentary Research 77, no. 7 (July 1, 2007): 572–86. http://dx.doi.org/10.2110/jsr.2007.057.
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Al-Mojel, Abdullah, Philippe Razin, Yves-Michel Le Nindre, and Guillaume Dera. "Shallow-marine depositional sequences in a transgressive mixed siliciclastic-carbonate system: The Early Jurassic Marrat Formation from central Saudi Arabia." Journal of African Earth Sciences 167 (July 2020): 103429. http://dx.doi.org/10.1016/j.jafrearsci.2019.02.011.
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Varga, Andrea, Gábor Bozsó, István Garaguly, Béla Raucsik, Attila Bencsik, and Balázs Kóbor. "Cements, Waters, and Scales: An Integrated Study of the Szeged Geothermal Systems (SE Hungary) to Characterize Natural Environmental Conditions of the Thermal Aquifer." Geofluids 2019 (April 24, 2019): 1–21. http://dx.doi.org/10.1155/2019/4863814.
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The study area, Pannonian Basin (Central Europe), is characterized by high heat flow and presence of low-enthalpy geothermal waters. In the Szeged Geothermal Systems (Hungary), having Miocene to Pliocene sandstone aquifers with dominantly Na–HCO3-type thermal water, unwanted carbonate scaling was observed. An integrated approach consisting of host rock and scale mineralogical and petrographic analyses as well as water chemistry led to a better understanding of the characteristic natural (geogenic) environmental conditions of the geothermal aquifers and to highlight their technical importance. Analyses of the reservoir sandstones showed that they are mineralogically immature mixed carbonate-siliciclastic rocks with significant macroporosity. Detrital carbonate grains such as dolomite and limestone fragments appear as important framework components (up to ~20–25%). During water–rock interactions, they could serve as a potential source of the calcium and bicarbonate ions, contributing to the elevated scaling potential. Therefore, this sandstone aquifer cannot be considered as a conventional siliciclastic reservoir. In mudrocks, a significant amount of organic matter also occurs, triggering CO2producing reactions. Correspondingly, framboidal pyrite and ferroan calcite are the main cement minerals in all of the studied sandstone samples which can suggest that calcite saturation state of the thermal fluid is close to equilibrium in oxygen-depleted pore water. Analysis of the dominant carbonate crystals in the scale can suggest that growth of the feather dendrites of low-Mg calcite was probably driven by rapid CO2degassing of CO2-rich thermal water under far-from-equilibrium conditions. Based on hydrogeochemical data and related indices for scaling and corrosion ability, the produced bicarbonate-rich (up to 3180 mg/l) thermal water has a significant potential for carbonate scaling which supports the aforementioned statement. Taking into consideration our present knowledge of geological setting of the studied geothermal systems, temporal changes in chemical composition and temperature of the thermal water during the heating period can indicate upwelling fluids from a deep aquifer. Regarding the pre-Neogene basement, hydrologic contact with a Triassic carbonate aquifer might be reflected in the observed chemical features such as decreased total dissolved solids and increased bicarbonate content with high scale-forming ability. The proposed upflow of basin-derived water could be channeled by Neogene to Quaternary fault zones, including compaction effects creating fault systems above the elevated basement high. The results may help to understand the cause of the high carbonate scale precipitation rates in geothermal systems tapping sandstone aquifers.
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Daniell, James, Thomas Manoy, Robin J. Beaman, Jody M. Webster, and Ángel Puga-Bernabéu. "Shelf-edge delta and reef development on a mixed siliciclastic–carbonate margin, central Great Barrier Reef." Journal of Sedimentary Research 90, no. 10 (October 1, 2020): 1286–304. http://dx.doi.org/10.2110/jsr.2020.61.
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ABSTRACT The Great Barrier Reef (GBR) is the world's largest extant mixed silicilastic–carbonate margin. Previous research on the Great Barrier Reef has suggested that the extensive barrier reef system may act as an impermeable barrier and limit the development of delta systems during lowstands, but sufficient geophysical data to support this hypothesis are lacking. We use dense sparker seismic and sub-bottom profiler data to better understand the structure of a large lobe-shaped feature (∼ 10 km × 10 km) on the shelf edge of the central GBR and the interactions between siliciclastic and carbonate sedimentary systems. Interpreted sparker seismic contains prograding clinoforms and suggest that the lobe-shaped feature was a river-dominated shelf-edge delta. A delta on the shelf edge implies that the presence of an exposed barrier reef was not a major impediment to deposition and that other adjacent lobe-shaped features are also deltaic deposits. The shelf-edge deltas were deposited onto a broad upper-slope terrace that allowed continued progradation and limited incision when sea level fell below the shelf edge. Delta foresets are commonly colonized by coral reefs, but the spatial and temporal relationship between reefs and some deltaic units remains unclear. The presence of multiple shelf-edge deltas that link to previously mapped Burdekin River paleo-channels indicates a complex history of sedimentation, with the Burdekin River delta migrating up to 100 km along the GBR margin during the late Quaternary. Regional bathymetric data suggest that large modern or recent shelf-edge deltas are rare on the GBR and that there was a broad range of sedimentary processes operating along the margin of the GBR during periods of low sea level.
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Utami, Dwi Amanda, Lars Reuning, Maximillian Hallenberger, and Sri Yudawati Cahyarini. "The mineralogic and isotopic fingerprint of equatorial carbonates: Kepulauan Seribu, Indonesia." International Journal of Earth Sciences 110, no. 2 (January 18, 2021): 513–34. http://dx.doi.org/10.1007/s00531-020-01968-9.
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AbstractKepulauan Seribu is an isolated patch reef complex situated in the Java Sea (Indonesia) and is a typical example for a humid, equatorial carbonate system. We investigate the mineralogical and isotopic fingerprint of Panggang, one of the reef platforms of Kepulauan Seribu, to evaluate differences to other carbonate systems, using isotope in combination with XRD and SEM analysis. A characteristic property of shallow water (< 20 m) sediments from Kepulauan Seribu is their increased LMC content (~ 10%) derived from some genera of rotaliid foraminifers and bivalves. The relative abundance of these faunal elements in shallow waters might be related to at least temporary turbid conditions caused by sediment-laden river runoff. This influence is also evidenced by the presence of low amounts of siliciclastic minerals below the regional wave base. Kepulauan Seribu carbonates are characterized by very low δ13C and δ18O values. This is related to the isotopically depleted riverine input. The δ13CDIC in riverine water is reduced by the contribution of 12C from riverside mangroves. Deep atmospheric convection and intensive rains contribute 18O-depleted freshwater in the river catchments, finally reducing salinity in the Java Sea. The depleted δ13C signature in carbonates is further enhanced by the lack of green algae and inorganic carbonates and abundance of coral debris. Low δ18O values in carbonates are favored by the high water temperatures in the equatorial setting. Since equatorial carbonates in SE Asia, including the Java Sea, are typically influenced by high turbidity and/or river runoff, the observed distinctively low isotope values likely are characteristic for equatorial carbonate systems in the region.
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Hanken, Nils-Martin, Alfred Uchman, Jesper Kresten Nielsen, Snorre Olaussen, Tor Eggebø, and Reidar Steinsland. "Late Ordovician Trace Fossils from Offshore to Shallow Water Mixed Siliciclastic and Carbonate Facies in the Ringerike Area, Oslo Region, Norway." Ichnos 23, no. 3-4 (September 6, 2016): 189–221. http://dx.doi.org/10.1080/10420940.2016.1199427.
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McLean, Duncan, Matthew Booth, David J. Bodman, and Finlay D. McLean. "Carboniferous records of the Zoophycos group of trace fossils from England, Wales, the Isle of Man and the North Sea." Proceedings of the Yorkshire Geological Society 63, no. 2 (May 29, 2020): 135–45. http://dx.doi.org/10.1144/pygs2019-007.
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The Zoophycos group of trace fossils is common in Carboniferous to recent marine strata and sediments, and is a common component of ichnofaunas in the Visean and Namurian stages of England and Wales. A review of new and published records indicates that it is often present in limestones and sandstones of Chadian to Arnsbergian age. Thereafter it is less common, and restricted to clastic rocks. There are no known records within Carboniferous strata above the lowest Westphalian. The form is most common and often abundant in limestones of the Yoredale facies in the upper Visean and lower Namurian stages of northern England, particularly so in northern Northumberland. Where detailed sedimentological data exist, they indicate that the organisms responsible for the Zoophycos group burrowed into unconsolidated carbonate substrate that was deposited under low accumulation rates, often affected by storm wave action and where seawater flow provided a nutrient supply. However, in mixed carbonate–clastic settings, the deep-tier nature of Zoophycos may indicate that the organism lived in overlying shallow-marine, clastic-dominated depositional environments and burrowed down into the carbonate substrate. The same may be true of siliciclastic depositional settings where the presence of Zoophycos in some sandstones may reflect the palaeoenvironment of the overlying, finer-grained transgressive marine (prodelta and distal mouth bar) deposits.Supplementary material: A spreadsheet with details of Carboniferous records of Zoophycos group fossils from England, Wales, the Isle of Man and the North Sea is available at https://doi.org/10.6084/m9.figshare.c.4994636