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1
Okada, Hakuyu. "Anatomy of trench-slope basins: Examples from the Nankai Trough." Palaeogeography, Palaeoclimatology, Palaeoecology 71, no. 1-2 (June 1989): 3–13. http://dx.doi.org/10.1016/0031-0182(89)90026-6.
2
Narayanaswamy, Bhavani E., and James A. Blake. "A new species of Orbiniella (Polychaeta: Orbiniidae) from deep basins of Antarctica." Journal of the Marine Biological Association of the United Kingdom 85, no. 4 (June 27, 2005): 843–46. http://dx.doi.org/10.1017/s0025315405011793.
Анотація:
During the 2002 Antarctic Deep-sea Biodiversity (ANDEEP) programme to the Drake Passage, Weddell Sea Basin and South Sandwich Slope and trench, a new deep-water species of orbiniid polychaete was collected: Orbiniella andeepia sp. nov. Orbiniella andeepia appears to be most closely related to O. marionensis but differs in capillary setal structure, the type and number of acicular spines found in each podial lobe. Orbiniella andeepia is only the third deep-water species of Orbiniella to be discovered. It exhibits both a wide depth- and geographic-range within the Antarctic slope and abyssal sediments.
3
Fralick, Philip, Jinhua Wu, and Howard R. Williams. "Trench and slope basin deposits in an Archean metasedimentary belt, Superior Province, Canadian Shield." Canadian Journal of Earth Sciences 29, no. 12 (December 1, 1992): 2551–57. http://dx.doi.org/10.1139/e92-202.
Анотація:
The identification of a late Archean arc–trench assemblage in northwestern Ontario provides the opportunity to compare depositional systems developed in a Precambrian convergent setting with Cenozoic examples. Two types of sedimentary associations exist in the accretionary complex. Medium- to thick-bedded Bouma A, AB, and ABC felsic turbidites dominate the belt. These are primarily organized into unstructured sequences and reflect deposition in a ramp-like environment with multiple feed points supplying sediment from a forearc basin. Mafic turbidites with possible shallow water reworked intervals form isolated pods within the metasedimentary belt. Erosion of upthrust blocks of sedimentary strata containing ultramafic masses supplied this sediment to elevated slope basins. These types of depositional systems are similar in many respects to those developed in Cenozoic and Holocene arc–trench settings.
4
De Rosa, R., G. G. Zuffa, A. Taira, and J. K. Leggett. "Petrography of trench sands from the Nankai Trough, southwest Japan: implications for long-distance turbidite transportation." Geological Magazine 123, no. 5 (September 1986): 477–86. http://dx.doi.org/10.1017/s0016756800035068.
Анотація:
AbstractTwenty-three samples of Quaternary sands from Deep Sea Drilling Project (DSDP) Leg 87 Sites 582 (trench axis) and 583 (lowermost terrace of uplifted trench sediments in the accretionary prism) off Shikoku show a 70–80% volcanic component in the terrigenous grain population. This component comprises 30–40% neovolcanic grains, among which basic and intermediate types are present in roughly equal proportions, and 60–70% palaeovolcanic grains, which are predominantly of acidic composition. No volcanic terrane occurs, in the hinterland of the Shikoku portion of the Nankai Trough, and the first such rocks to the east (up the very slight depositional slope of the Nankai Trough axis) are not encountered for more than 500 km. These, occupying the Izu Peninsula and the majority of the Tokai drainage basin to the north, are Neogene and Recent volcanics which are of comparable variability to the volcanic grains in the sands off Shikoku.The minor component of sedimentary, metamorphic and plutonic grains in the Leg 87 sand samples can be matched with the basinal clastic ophiolitic Shimanto and Chichibu terranes and the high-pressure metamorphic Sambagawa terrane which border the Nankai Trough fore-arc along southwest Japan. This detritus also most likely derives from the Tokai drainage basin, where the easternmost outcrops of the above-mentioned terranes occur, because most sediments deriving from Shikoku and the Kii regions are ponded in terraced fore-arc basins or in basins on the lower slope. Only three major submarine canyons debouch into the floor of the Nankai Trough. The easternmost of these, the Suruga Trough, taps the volcanic Izu/Tokai hinterland, and is therefore the conduit for most sand fed to the trench off Shikoku.
5
Patton, J. R., C. Goldfinger, A. E. Morey, C. Romsos, B. Black, and Y. Djadjadihardja. "Seismoturbidite record as preserved at core sites at the Cascadia and Sumatra–Andaman subduction zones." Natural Hazards and Earth System Sciences 13, no. 4 (April 4, 2013): 833–67. http://dx.doi.org/10.5194/nhess-13-833-2013.
Анотація:
Abstract. Turbidite deposition along slope and trench settings is evaluated for the Cascadia and Sumatra–Andaman subduction zones. Source proximity, basin effects, turbidity current flow path, temporal and spatial earthquake rupture, hydrodynamics, and topography all likely play roles in the deposition of the turbidites as evidenced by the vertical structure of the final deposits. Channel systems tend to promote low-frequency components of the content of the current over longer distances, while more proximal slope basins and base-of-slope apron fan settings result in a turbidite structure that is likely influenced by local physiography and other factors. Cascadia's margin is dominated by glacial cycle constructed pathways which promote turbidity current flows for large distances. Sumatra margin pathways do not inherit these antecedent sedimentary systems, so turbidity currents are more localized.
6
Stevens, Scott H., and Gregory F. Moore. "Deformational and sedimentary processes in trench slope basins of the western Sunda Arc, Indonesia." Marine Geology 69, no. 1-2 (December 1985): 93–112. http://dx.doi.org/10.1016/0025-3227(85)90135-5.
7
PAL, TAPAN, PARTHA PRATIM CHAKRABORTY, TANAY DUTTA GUPTA, and CHANAM DEBOJIT SINGH. "Geodynamic evolution of the outer-arc–forearc belt in the Andaman Islands, the central part of the Burma–Java subduction complex." Geological Magazine 140, no. 3 (May 2003): 289–307. http://dx.doi.org/10.1017/s0016756803007805.
Анотація:
The Andaman Islands, the central part of Burma–Java subduction complex, expose tectonostratigraphic units of an accretionary prism in an outer-arc setting and turbidites of a forearc setting. A number of N–S-trending dismembered ophiolite slices of Cretaceous age, occurring at different structural levels with Eocene trench-slope sediments, were uplifted and emplaced by a series of E–dipping thrusts. Subsequently, N–S normal and E–W strike-slip faults resulted in the development of a forearc basin with deposition of Oligocene and Mio-Pliocene sediments. Metapelites and metabasics of greenschist to amphibolite grade occur in a melange zone of ophiolites. The Eocene Mithakhari Group represents pelagic trench sediments and coarser clastics derived from ophiolites. Evidence of frequent facies changes, predominance of mass flow deposits, syn-sedimentary basinal disturbance and wide palaeogeographic variation indicate deposition of Eocene sediments in isolated basins of an immature trench-slope setting. Deposition of the Oligocene Andaman Flysch Group in a forearc setting is indicated by the large-scale persistence of beds, lack of small-scale lithological variation, bimodal provenance, less deformation, a well-defined submarine fan sequence and development predominantly on the eastern part of the outer arc. The Mio-Pliocene Archipelago Group includes alternations of siliciclastic turbidites and subaqueous pyroclastic flow deposits in the lower part and carbonate turbidites in the upper part, suggesting its deposition in the shallower forearc compared to the siliciclastic Oligocene sediments.
8
Malie, Pierre, Julien Bailleul, Frank Chanier, Renaud Toullec, Geoffroy Mahieux, Vincent Caron, Brad Field, Rafael Ferreiro Mählmann, and Sébastien Potel. "Spatial distribution and tectonic framework of fossil tubular concretions as onshore analogues of cold seep plumbing systems, North Island of New Zealand." Bulletin de la Société géologique de France 188, no. 4 (2017): 25. http://dx.doi.org/10.1051/bsgf/2017192.
Анотація:
Analysis of offshore seismic lines suggests that a strong relationship exists between tectonic structures and fluid migration in accretionary prisms. However, only few field analogues of plumbing systems and their tectonic frameworks have been investigated in detail until now. The uplifted accretionary prism of the Hikurangi Margin (North Island, New Zealand) exposes early to late Miocene mudrocks in coastal cliffs of Cape Turnagain and in the Akitio syncline, south-east of the Pongaroa city. These outcrops display tubular carbonate concretions corresponding to complex subsurface plumbing networks of paleo-seeps within Miocene trench slope basins. We present here, new results on the spatial distribution of these tubular carbonate concretions, with particular attention to their relation to tectonic structures. In the Pongaroa area, tubular carbonate concretions in lower Miocene mudrocks occur along a N-S trend, while in middle Miocene strata they occur along a NNE-SSW direction. The N-S trend parallels a major fault zone (i.e. the Breakdown fault zone), which separates two wide synclines, the Waihoki and the Akitio synclines. During the Early-Middle Miocene, the Breakdown fault zone controlled the evolution of the Akitio trench slope basin constituting its western edge. The NNE-SSW strike parallels the axis of the Akitio syncline and is also parallel to the present-day subduction front. Our results therefore show that tubular concretions are parallel to post-Middle Miocene second order folding and thrusting in the northeastern limb of the Akitio syncline. In the Cape Turnagain area, tubular concretions occur in the western limb of the Cape Turnagain syncline, in the footwall of the major seaward-verging Cape Turnagain fault. This suggests that fluid migrations may occur not only in the crests of anticlines, as observed offshore for present-day plumbing system of cold seeps, but also in the footwalls of thrust faults. All these observations show that the spatial distribution of tubular concretions is controlled by regional tectonic structures with paleo-fluid migrations related to major deformation episodes of the accretionary prism. Thus, we distinguish three episodes events that likely triggered fluid migration leading to the formation of the tubular concretions: (1) In the Early Miocene, shortly after the onset of development of the Akitio trench slope basin, on its inner (western) edge; (2) During the late Middle Miocene, during an extensional deformation episode on the western limb of the Akitio trench slope basin; (3) At the end of the Late Miocene, during a second major shortening period at the footwall of major thrust fault, such as in the Cape Turnagain area.
9
Bailleul, Julien, Frank Chanier, Jacky Ferrière, Cécile Robin, Andrew Nicol, Geoffroy Mahieux, Christian Gorini, and Vincent Caron. "Neogene evolution of lower trench-slope basins and wedge development in the central Hikurangi subduction margin, New Zealand." Tectonophysics 591 (April 2013): 152–74. http://dx.doi.org/10.1016/j.tecto.2013.01.003.
10
Gambi, Cristina, Nikolaos Lampadariou, and Roberto Danovaro. "Latitudinal, longitudinal and bathymetric patterns of abundance, biomass of metazoan meiofauna: importance of the rare taxa and anomalies in the deep Mediterranean Sea." Advances in Oceanography and Limnology 1, no. 1 (June 1, 2010): 167. http://dx.doi.org/10.4081/aiol.2010.5299.
Анотація:
Quantitative information on the spatial distribution of meiofaunal abundance, biomass and biodiversity (as richness of higher taxa) is summarised from 476 sites of the deep- Mediterranean Sea, at depths ranging from ca. 200 to 4617 m. Meiofaunal abundance (46531 and 30624 ind 10 cm2 at 200–1000 and 1000–2000m depth intervals) and biomass (12516 and 11920 mgC 10 cm2 at 200–1000 and 1000–2000m depth intervals) in the bathyal sediments of the Mediterranean Sea are similar to those reported in oceans worldwide but at much higher depths (abyssal or hadal). Meiofaunal abundance, biomass and richness of taxa displayed a common decreasing bathymetric pattern, but showed a steeper negative slope than in other oceanic regions. Latitudinal and longitudinal gradients revealed idiosyncratic patterns when different basins (Western, Central and Eastern) and habitats (open slope, canyon, deep basin and trench) were considered. The results of the non parametric multivariate multiple regression analyses revealed that, conversely to what expected, depth is not the key factor in explaining the variance of meiofaunal assemblages living down to 2000m depth. The quality and quantity of food sources explained a larger fraction of the variance of meiofaunal variables (47, 25 and 33% for abundance, biomass and diversity, respectively) and the importance of food sources increased with increasing depth. However, most of the variance remains unexplained suggesting that other factors (such as episodic events, deep currents, other unexplored yet environmental characteristics) can act a key role in driving the observed meiofaunal spatial patterns. The analysis of rare taxa (on a data set of 183 samples), suggested that differences in the meiofaunal community were evident when dominating taxa (nematodes, copepods and polychaetes) were excluded. We report the presence of rare taxa exclusively present in open slope (amphipods) and canyon (cnidarians and decapod larvae) systems, whereas others are exclusively found in one of the two basins (e.g. gastrotrichs in the Western basin and amphipods and gastropods in the Eastern basin). The apparent preference of some rare taxa for a specific habitat or basin could have important implications for the identification of the hot spots of benthic diversity, for identifying the connectivity among systems and for an appropriate management of deep-sea habitats in the Mediterranean Sea.
11
Clift, Peter D., and Alastair H. F. Robertson. "A Cretaceous Neo-Tethyan carbonate margin in Argolis, southern Greece." Geological Magazine 127, no. 4 (July 1990): 299–308. http://dx.doi.org/10.1017/s0016756800014862.
Анотація:
AbstractThe Argolis Peninsula, southern Greece, is believed to form part of a Pelagonian microcontinent located between two oceanic basins, the Pindos to the west and theVardar to the east, in Triassic to Tertiary time. In eastern Argolis, two important units are exposed: (i) the Ermioni Limestones cropping out in the southwest; (ii) the Poros Formation, observed on an offshore island in the northeast, and on the adjacent mainland. Both these units comprise late Cretaceous (Aptian-Maastrichtian) pelagic limestones, calciturbidites, lenticular matrix- and clast-supported limestone conglomerates and slump sheets. However, the Poros Formation is distinguished from the Ermioni Limestones by the presence of bituminous micritic limestones and an increasing proportion of shale up sequence. These successions are deep-water slope carbonates that once formed the southeast-facing passive margin of the Pelagonian platform (Akros Limestone). Beyond this lay a late Cretaceous ocean basin in the Vardar Zone. This ocean was consumed in an easterly-dipping subduction zone in latest Cretaceous (?) to early Tertiary time, giving rise to an accretionary complex (Ermioni Complex). During early Tertiary (Palaeocene-Eocene) time the passive continental margin (Pelagonian Zone) collided with the trench and accretionary complex to the east. As the suture tightened, former lower-slope carbonates (Ermioni Limestones) were accreted to the base of the over-riding thrust sheets and emplaced onto the platform. Farther west, bituminous upper slope carbonates (Poros Formation) flexurally subsided and passed transitionally upwards into calcareous flysch and olistostromes in a foreland basin. These sediments were then overridden by the emplacing thrust stack and themselves underplated. Late-stage high-angle faulting then disrupted the tectonostratigraphy, in places juxtaposing relatively high and low structural levels of the complex.
12
Bailleul, J., C. Robin, F. Chanier, F. Guillocheau, B. Field, and J. Ferriere. "Turbidite Systems in the Inner Forearc Domain of the Hikurangi Convergent Margin (New Zealand): New Constraints on the Development of Trench-Slope Basins." Journal of Sedimentary Research 77, no. 4 (April 1, 2007): 263–83. http://dx.doi.org/10.2110/jsr.2007.028.
13
Vozárová, Anna, Katarína Šarinová, Dušan Laurinc, Elena Lepekhina, Jozef Vozár, Nickolay Rodionov, and Pavel Lvov. "Exhumation history of the Variscan suture: Constrains on the detrital zircon geochronology from Carboniferous–Permian sandstones (Northern Gemericum; Western Carpathians)." Geologica Carpathica 70, no. 6 (December 1, 2019): 512–30. http://dx.doi.org/10.2478/geoca-2019-0030.
Анотація:
Abstract The Late Paleozoic sedimentary basins in the Northern Gemericum evolved gradually in time and space within the collisional tectonic regime of the Western Carpathian Variscan orogenic belt. The detrital zircon age spectra, obtained from the Mississippian, Pennsylvanian and Permian metasediments, have distinctive age distribution patterns that reflect the tectonic setting of the host sediments. An expressive unimodal zircon distribution, with an age peak at 352 Ma, is shown by the basal Mississippian metasediments. These represent a relic of the convergent trench-slope sedimentary basin fill. In comparison, the Pennsylvanian detrital zircon populations display distinct multimodal distributions, with the main age peaks at 351, 450, 565 Ma and smaller peaks at ~2.0 and ~2.7 Ga. This is consistent with derivation of clastic detritus from the collisional suture into the foreland basin. Similarly, the Permian sedimentary formations exhibit the multimodal distribution of zircon ages, with main peaks at 300, 355 and 475 Ma. The main difference, in comparison with the Pennsylvanian detrital zircon assemblages, is the sporadic occurrence of the Kasimovian– Asselian (306–294 Ma), as well as the Artinskian–Kungurian (280–276 Ma) igneous zircons. The youngest magmatic zircon ages nearly correspond to the syn-sedimentary volcanic activity with the depositional age of the Permian host sediments and clearly indicate the extensional, rift-related setting.
14
CHERNOVA, NATALIA, RALF THIEL, and IRINA EIDUS. "Four new species of Careproctus (Cottoidei: Liparidae) from the deep-water vicinity of the southern Kuril Islands (Western North Pacific)." Zootaxa 4821, no. 1 (July 30, 2020): 71–87. http://dx.doi.org/10.11646/zootaxa.4821.1.3.
Анотація:
Four new species of Careproctus (Cottoidei: Liparidae) are described from the Bussol Strait (the deepest channel of the Kuril archipelago) and two neighboring abyssal basins of the Western North Pacific. Careproctus laperousei sp. nov. from the northern slope of the Kuril-Kamchatka Trench (depths of 4796–4803 m) has the following characters: vertebrae 57, pectoral-fin rays 26, principal caudal-fin rays 8 and pore pattern 2-6-7-1; it differs from the most similar congeners from the North Pacific in having a black peritoneum, short head (22.5 % of standard length, SL) and large disk (37.0 % of head length, lc). Careproctus brevipectoralis sp. nov. from the Kuril Basin of the Sea of Okhotsk (depths of 3301 m) has the following characters: vertebrae 55, pectoral-fin rays 26, caudal-fin rays 9, pore pattern 2-6-7-1 and peritoneum black; it differs from congeners by the absence of pleural ribs, deep and compressed leaf-like body (greatest depth 119 % lc, depth above anal-fin origin 113 % lc), small head (18 % SL), short pectoral fin (11 % SL) and cartilaginous-like tissue surrounding the dorsal fin. Careproctus pulcher sp. nov. and Careproctus globulus sp. nov., both having 46 vertebrae, are found on the Pacific side of the Bussol Strait at depths of 2350–2358 m. Careproctus pulcher sp. nov. is characterized by pectoral-fin rays 31–32, caudal-fin rays 10, pore pattern 2-6-7-1 and peritoneum pale; it differs from the most similar congeners in having a shorter head (25.5–26.3 % SL in adults) and gill opening reaching ventrally to 4th pectoral ray. Careproctus globulus sp. nov. has the following characters: pectoral-fin rays about 24, caudal-fin rays 8 and peritoneum black; it differs from other species in having a globular body, deep curve of vertebral column and pore pattern 2-5-6-1. Thus, based on these collections, the underwater sill of the Bussol Strait is inhabited by different species of Careproctus than the neighboring abyssal plains, Kuril-Kamchatka Trench and the Kuril Basin of the Sea of Okhotsk. Careproctus laperousei sp. nov. is the most deep-water Careproctus in the North Pacific.
15
McArthur, Adam D., Julien Bailleul, Geoffroy Mahieux, Barbara Claussmann, Alex Wunderlich, and William D. McCaffrey. "Deformation–sedimentation feedback and the development of anomalously thick aggradational turbidite lobes: Outcrop and subsurface examples from the Hikurangi Margin, New Zealand." Journal of Sedimentary Research 91, no. 4 (April 9, 2021): 362–89. http://dx.doi.org/10.2110/jsr.2020.013.
Анотація:
ABSTRACT Concepts of the interaction between autogenic (e.g., flow process) and allogenic (e.g., tectonics) controls on sedimentation have advanced to a state that allows the controlling forces to be distinguished. Here we examine outcropping and subsurface Neogene deep-marine clastic systems that traversed the Hikurangi subduction margin via thrust-bounded trench-slope basins, providing an opportunity to examine the interplay of structural deformation and deep-marine sedimentation. Sedimentary logging and mapping of Miocene outcrops from the exhumed portion of the subduction wedge record heavily amalgamated, sand-rich lobe complexes, up to 200 m thick, which accumulated behind NE–SW-oriented growth structures. There was no significant deposition from low-density parts of the gravity flows in the basin center, although lateral fringes demonstrate fining and thinning indicative of deposits from low-density flows. Seismic data from the offshore portion of the margin show analogous lobate reflector geometries. These deposits accumulate into complexes up to 5 km wide, 8 km long, and 300 m thick, comparable in scale with the outcropping lobes on this margin. Mapping reveals lobe complexes that are vertically stacked behind thrusts. These results illustrate repeated trapping of the sandier parts of turbidity currents to form aggradational lobe complexes, with the finer-grained suspended load bypassing to areas downstream. However, the repeated development of lobes characterized by partial bypass implies that a feedback mechanism operates to perpetuate a partial confinement condition, via rejuvenation of accommodation. The mechanism proposed is a coupling of sediment loading and deformation rate, such that load-driven subsidence focuses stress on basin-bounding faults and perpetuates generation of accommodation in the basin, hence modulating tectonic forcing. Recognition of such a mechanism has implications for understanding the tectono-stratigraphic evolution of deep-marine fold and thrust belts and the distribution of resources within them.
16
Cooper, David J. W., Michael P. Searle, and Mohammed Y. Ali. "Structural evolution of Jabal Qumayrah: A salt-intruded culmination in the northern Oman Mountains." GeoArabia 17, no. 2 (April 1, 2012): 121–50. http://dx.doi.org/10.2113/geoarabia1702121.
Анотація:
ABSTRACT The Jabal Qumayrah area of the northern Oman Mountains records the evolution and subsequent destruction of a Mesozoic passive continental margin in the Oman segment of the Neo-Tethys Ocean, followed by the re-establishment of a passive margin, punctuated by phases of Tertiary compression. Almost uniquely along the Oman Mountains, it also contains intrusions of salt. Detachment of oceanic sediments and volcanics during the early phases of NE-directed subduction beneath the nascent Semail Ophiolite created an in-sequence stack of imbricated thrust units comprising distal trench units (Haybi Complex), and deep-ocean and continental rise sediments derived from the Mesozoic Oman margin (the Hawasina Complex). These were emplaced onto the depressed margin beneath and ahead of the ophiolite during its obduction in the Cenomanian– Coniacian. The Mesozoic continental slope sediments of the Sumeini Group had already been largely over-ridden by the more distal thrust sheets when the Hawasina sole thrust propagated into those sediments. This detached a Sumeini Group thrust sheet, which was transported westward for at least 7 km, carrying with it the overlying Hawasina thrust stack. Structurally lower parts of the Hawasina thrust stack (Hamrat Duru Group) also extended ahead of the Sumeini Group thrust sheet, but they were not restacked with it, indicating motion continued along this part of the Hawasina sole thrust. Further footwall collapse detached at least one more imbricate within the Sumeini Group and the combined thrust stack was then folded along a N-S axis, possibly above a frontal ramp. This was associated with complex out-of-sequence forward and back-thrusting at the lower structural levels. A right-lateral scissors fault developed at right angles to the direction of nappe transport, associated with normal faulting down-to-south. Late-stage culmination within the nappe pile created an asymmetrical west-facing dome, around which the structurally overlying Hawasina thrust sheets are folded. Passive margin sedimentation was re-established in the Campanian–Maastrichtian following subsidence of the locally emergent nappe pile and was dominated by carbonate sedimentation with little clastic input from the ophiolite or Hawasina sediments. Stable sedimentation persisted until Oligocene–Miocene compression, synchronous with the Zagros compressional event in Iran, resulted in west-facing folding along the western side of the northern Oman Mountains and their subsequent uplift. The Jabal Qumayrah massif preserves a salt intrusion composed of gypsum and anhydrite, the top of which is now exposed in the centre of the culmination. The origin of the salt remains unclear and investigations continue. Possible sources include the extension of the major regional salt basins found in the foreland, in particular those at the Ediacaran/Cambrian boundary (Ara Group), beneath the Hawasina Nappes and Semail Ophiolite. Alternatively, evaporitic basins may have developed locally along the edge of the proto Neo-Tethyan margin during the earliest rifting phase, beneath what became the continental slope deposits, although there is little evidence for these elsewhere in the autochthonous shelf succession.
17
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.
Анотація:
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.
18
Garcia, Emmanuel Soliman M., David T. Sandwell, and Dan Bassett. "Outer trench slope flexure and faulting at Pacific basin subduction zones." Geophysical Journal International 218, no. 1 (March 27, 2019): 708–28. http://dx.doi.org/10.1093/gji/ggz155.
Анотація:
SUMMARY Flexure and fracturing of the seafloor on the outer trench wall of subduction zones reflect bending of the lithosphere beyond its elastic limit. To investigate these inelastic processes, we have developed a full nonlinear inversion approach for estimating the bending moment, curvature and outer trench wall fracturing using shipboard bathymetry and satellite altimetry-derived gravity data as constraints. Bending moments and downward forces are imposed along curved trench axes and an iterative method is used to calculate the nonlinear response for 26 sites in the circum-Pacific region having seafloor age ranging from 15 to 148 Ma. We use standard thermal and yield strength envelope models to develop the nonlinear moment versus curvature relationship. Two coefficients of friction of 0.6 and 0.3 are considered and we find that the lower value provides a better overall fit to the data. The main result is that the lithosphere is nearly moment saturated at the trench axis. The effective elastic thickness of the plate on the outer trench slope is at least three times smaller than the elastic thickness of the plate before bending at the outer rise in agreement with previous studies. The average seafloor depth of the unbent plate in these 26 sites matches the Parsons & Sclater depth versus age model beyond 120 Ma. We also use the model to predict the offsets of normal faults on the outer trench walls and compare this with the horst and graben structures observed by multibeam surveys. The model with the lower coefficient of friction fits the fault offset data close to the trench axis. However, the model predicts significant fracturing of the lithosphere between 75 and 150 km away from the trench axis where no fracturing is observed. To reconcile these observations, we impose a thermoelastic pre-stress in the lithosphere prior to subduction. This pre-stress delays the onset of fracturing in better agreement with the data.
19
Doubleday, P. A., D. I. M. Macdonald, and P. A. R. Nell. "Sedimentology and structure of the trench-slope to forearc basin transition in the Mesozoic of Alexander Island, Antarctica." Geological Magazine 130, no. 6 (November 1993): 737–54. http://dx.doi.org/10.1017/s0016756800023128.
Анотація:
AbstractThe Mesozoic forearc of Alexander Island, Antarctica, is one of the few places in the world where the original stratigraphic relationship between a forearc basin and an accretionary complex is exposed. Newlydiscovered sedimentary rocks exposed at the western edge of the forearc basin fill (the Kimmeridgian–Albian Fossil Bluff Group) record the events associated with the basin formation. These strata are assigned to the newly defined Selene Nunatak Formation (?Bathonian) and Atoll Nunataks Formation (?Bathonian-Tithonian) within the Fossil Bluff Group.The Selene Nunatak Formation contains variable thicknesses of conglomeratesand sandstones, predominantly derived from the LeMay Group accretionary complex upon which it is unconformable. The formation marks emergence and subsequent erosion of the inner forearc area. It is conformably overlain by the1 km thick Atoll Nunataks Formation, characterized by thinly-bedded mudstones and silty mudstones representing a marine transgression followed by trench-slope deposition. The Atoll Nunataks Formation marks a phase of subsidence, possibly in response to tectonic events in the accretionary prism that are known to have occurred at about the same time.The Atoll Nunataks Formation is conformably overlain by the Himalia Ridge Formation, a thick sequence of basin-wide arc-derived conglomerates. This transition from fine- to coarse-grained deposition suggests that a well-developed depositional trough (and hence trench-slope break) had formed by that time. The Atoll Nunataks Formation therefore spans the formation of the forearc basin, and marks the transition from trench-slope to forearc basin deposition.
20
Underwood, Michael B., and Charles R. Norville. "Deposition of sand in a trench-slope basin by unconfined turbidity currents." Marine Geology 71, no. 3-4 (May 1986): 383–92. http://dx.doi.org/10.1016/0025-3227(86)90080-0.
21
Sangana, Peter, Qin Gao, and Zilong Li. "The Impact of the Caroline Ridge Subduction on the Geomorphological Characteristics of Major Landforms in the Yap Subduction Zone." Journal of Marine Science and Engineering 10, no. 10 (October 3, 2022): 1414. http://dx.doi.org/10.3390/jmse10101414.
Анотація:
The Caroline Ridge (CR) subduction underneath the Philippine Sea Plate brings complex morphotectonic characteristics to the Yap Subduction Zone (YSZ) compared to other normal intra-oceanic subduction systems. However, due to the relative paucity of precise geomorphological information, the detailed morphotectonic settings of the YSZ remain unclear. Therefore, we combine the latest-released bathymetry, marine geomorphometry techniques, and geophysical information to investigate the geomorphological characteristics of landforms in the YSZ and their inter-relationship with the CR subduction. The Parece Vela Basin displays NE-SW oriented fractures which are believed to be influenced by the subduction of CR in the ESE-WNW direction. The north part of the Yap arc exhibits higher Bouguer anomalies, implying the absence of the overlying normal volcanic arc crust. The arc-ward trench shows abnormal higher slope values and reveals two significant slope breaks. The Yap Trench axis reveals varying water depths with an extraordinarily deep point at around 9000 m. The sea-ward trench slope displays higher slope values than normal and shows the presence of grabens, horsts, and normal faults which indicate the bending of the CR before subduction. The CR subduction is observed to be critical in the formation of significant geomorphological characteristics in the YSZ.
22
Zhigulev, V. V., and A. V. Zhigulev. "Geological evolution of the northern Mid Kuril trough based on seismic facies analysis." Geosystems of Transition Zones 5, no. 3 (2021): 275–86. http://dx.doi.org/10.30730/gtrz.2021.5.3.275-286.
Анотація:
The model of geological evolution of an interarc basin, which is the north-east ending of Mid Kuril trough located on the continental slope of Kuril-Kamchatka trench, was constructed. Seismic facies analysis was first applied to define sedimentation conditions in a deep water trench. The analysis was based on the 2D CDP reflection seismic data obtained by Dalmorneftegeophysica JSC in 2014. According to the modeling results, the basin began to form in the Late Cretaceous and passed several stages. Initial subsidence of a local crust area of the incipient basin changed over to its further separation from the adjacent waters of the Sea of Okhotsk and Pacific Ocean by various volcanic formations framing its contour. The basin waters and the Pacific Ocean waters merged as a result of subsidence and submersion of volcanic structures on the east basin framing at the final stage during the Oligocene-Middle Miocene. This subsidence is directly related to the global processes associated with Kuril-Kamchatka ocean trench appearance such as inherent crust subsidence along valley bottom line accompanied by increase in inclination angle of its flanks. It was concluded that the trench origination time approximately corresponds to the Oligocene-Middle Miocene boundary.
23
McCRORY, PATRICIA A. "Evolution of a trench-slope basin within the Cascadia subduction margin: the Neogene Humboldt Basin, California." Sedimentology 42, no. 2 (April 1995): 223–47. http://dx.doi.org/10.1111/j.1365-3091.1995.tb02100.x.
24
Bassett, Kari N., and Richard Orlowski. "Pahau Terrane type locality: Fan delta in an accretionary prism trench‐slope basin." New Zealand Journal of Geology and Geophysics 47, no. 4 (December 2004): 603–23. http://dx.doi.org/10.1080/00288306.2004.9515079.
25
Underwood, Michael B., and David G. Howell. "Thermal maturity of the Cambria slab, an inferred trench-slope basin in central California." Geology 15, no. 3 (1987): 216. http://dx.doi.org/10.1130/0091-7613(1987)15<216:tmotcs>2.0.co;2.
26
Becker, David G., and Mark Cloos. "Melange Diapirs into the Cambria Slab: a Franciscan Trench Slope Basin near Cambria, California." Journal of Geology 93, no. 2 (March 1985): 101–10. http://dx.doi.org/10.1086/628934.
27
Gawlick, Hans-Jürgen, Sigrid Missoni +, Hisashi Suzuki, Špela Goričan, and Luis O'Dogherty. "Mesozoic tectonostratigraphy of the Eastern Alps (Northern Calcareous Alps, Austria): a radiolarian perspective / Mezozojska tektonostratigrafija Vzhodnih Alp (Severne Apneniške Alpe, Avstrija): radiolarijska perspektiva." Folia biologica et geologica 63, no. 2 (September 7, 2022): 5–33. http://dx.doi.org/10.3986/fbg0096.
Анотація:
The topic of the field trip is the Mesozoic geodynamic evolution in the Western Tethys realm well recorded in deep-water settings, especially in the radiolarian-bearing sedimentary rocks and radiolarites in the Eastern Alps (Northern Calcareous Alps). The well preserved Mesozoic sedimentary successions deposited in the Northern Calcareous Alps reflect two different Wilson cycles with its mountain building processes: Evolution of the Neo-Tethys Ocean to the south/southeast: The Middle Triassic oceanic break-up (Late Anisian) was followed by the Middle Triassic to Middle Jurassic passive margin evolution and later by Middle to early Late Jurassic thrusting related to ophiolite obduction and subsequent latest Jurassic to Early Cretaceous mountain uplift of the Neo-Tethys orogen to the south of the todays Northern Calcareous Alps. Evolution of the Alpine Atlantic Ocean (named Penninic Ocean in the Eastern Alps) to the north/northwest: The Late Early to Middle Jurassic oceanic break-up was followed by the Middle Jurassic to Late Cretaceous passive margin evolution and Late Cretaceous to Palaeogene subduction of the Penninic realm, Palaeogene collision and subsequent Neogene mountain uplift with its gravitational collapse (Lateral Tectonic Extrusion) of the Alpine orogen s.str. For another orogenesis in the “Mid-Cretaceous” (Aptian-Cenomanian), i.e. between these two well recognizable Wilson cycles, the geodynamic background has not been well explored or explained yet. This “Mid-Cretaceous” orogenesis draws a veil over the older Mesozoic plate configuration and has generated controversial discussion about the geodynamic evolution and palaeogeography in Triassic to Early Cretaceous times. However, this orogenesis is not connected to the Neo-Tethys or the Alpine Atlantic Wilson cycle. The field trip will focus on Triassic to Early Cretaceous deep-water, radiolarian-bearing sedimentary rocks deposited during the geodynamic history of the Neo-Tethys in different basins: rift-basins, shelf areas to continental slope, oceanic domains, and trench-like foreland basins. Special emphasis will be on the Jurassic to Early Cretaceous history, i.e. the geodynamic evolution before the “Mid-Cretaceous” tectonic motions and the influence of the evolution of two oceanic domains on the depositional environment above a drowned Triassic shelf (Apulian or wider Adria plate) between the Neo-Tethys Ocean to the south/southeast and the Alpine Atlantic Ocean to the north/northwest. The geodynamically triggered interplay between carbonate production, siliciclastic/volcanic input and deposition of siliceous rocks/radiolarites in combination with the asynchrony of basin formation frequently allows the calibration of radiolarians with e.g., ammonoids, conodonts, calpionellids and other organisms. Following the Middle Triassic (Late Anisian) Neo-Tethys oceanic break-up and the demise of shallow-water carbonate production, deposition of Middle Triassic (Late Anisian to Ladinian) radiolarian-bearing, mainly carbonate deep-water sediments is widespread all over the shelf. Deposition of radiolarites in the Eastern Alps is limited to the outer shelf/continental slope and the Neo-Tethys oceanic domain to the south/southeast. Widespread shallow-water carbonate production started again in the latest Middle Triassic (Late Ladinian) and lasted until the end of the Triassic, interrupted only by short-lasting siliciclastic intervals (“Mid-Carnian” turnover, Lunz event). In the Late Triassic huge carbonate platforms were formed. Deposition of Late Triassic open-marine and radiolarian-bearing sediments is therefore limited mainly to the outer shelf region and radiolarites were deposited only on the Neo-Tethys ocean floor. In Jurassic times, after the demise/drowning of the Late Triassic carbonate platform, calcareous siliceous sediments were again deposited widely. Rifting in the Alpine Atlantic realm to the north/northwest started in the Early Jurassic with oceanic break-up occurring from the Early/Middle Jurassic boundary onwards. The opening of the Alpine Atlantic to the north/northwest and, contemporaneously, the onset of convergence in the Neo-Tethys to the south/southeast worked in concert with radiolarite deposition culminating in the Middle Jurassic. Radiolarites were deposited practically all over the drowned continent except the areas of the Adriatic Carbonate Platform. Obduction of Neo-Tethys derived ophiolites since the Middle Jurassic led to the formation of a thin-skinned orogen with the formation of trench-like foreland basins in front of the advancing ophiolites. In these basins sedimentary mélanges with a radiolaritic-argillaceous matrix were deposited until the early Late Jurassic. Kimmeridgian-Tithonian shallow-water carbonate production on upper surfaces of the nappes restricted radiolarite deposition to remaining deep-water basins. In the frame of mountain uplift from the latest Jurassic (Tithonian) onwards the palaeotopography becomes overprinted by unroofing. Remaining deep-water foreland basins were successively filled in the Early Cretaceous by the erosional products of the uplifted Middle-Late Jurassic Neotethyan orogen. During this field trip in one of the most classical areas of the world, the central Northern Calcareous Alps with its world-wide known touristic highlights, we will visit locations documenting the interplay between siliciclastic input, volcanic activity, carbonate production, various tectonic motions and deposition of radiolarian-bearing siliceous rocks to radiolarites. Key words: Western Tethys realm, Triassic, Jurassic, Radiolarites, Palaeogeography IZVLEČEK Ekskurzija je posvečena mezozojski geodinamični evoluciji zahodne Tetide. Ta je dobro zabeležena v globokomorskih okoljih, še posebej v radiolaritih in drugih radiolarijskih sedimentnih kamninah v Vzhodnih Alpah, katerih del so Severne Apneniške Alpe. Dobro ohranjena mezozojska sedimentna zaporedja v Severnih Apneniških Alpah odražajo dva različna Wilsonova cikla z gorotvornimi procesi. Prvi cikel se nanaša na razvoj oceana Neotetida na jugu do jugovzhodu. Oceanskemu razpadu v srednjem triasu (zgornjem aniziju) je sledil razvoj pasivnega roba do srednje jure in pozneje, v srednji in zgornji juri, narivanje, povezano z obdukcijo ofiolitov. Na koncu jure in v spodnji kredi se je dvigal Neotetidin orogen, lociran južno od današnjih Severnih Apneniških Alp. Drugi cikel je povezan z razvojem oceana Alpski Atlantik (imenovanega Peninski ocean v Vzhodnih Alpah) na severu do severozahodu. Oceanskemu razpadu proti koncu spodnje jure in v srednji juri je sledil razvoj pasivnega roba od srednje jure do zgornje krede in subdukcija Peninika v zgornji kredi in paleogenu. Sledila je kolizija v paleogenu, v neogenu pa nadaljnje dviganje orogena z gravitacijskim kolapsom (lateralnim tektonskim iztiskanjem) Alpskega orogena sensu stricto. Obstajajo še dokazi za orogenezo v “srednji kredi” (aptij-cenomanij) med tema dvema dobro prepoznavnima Wilsonovima cikloma, vendar geodinamično ozadje te orogeneze še ni dobro raziskano ali pojasnjeno. “Srednjekredna” orogeneza zakriva starejšo mezozojsko konfiguracijo plošč, kar je vzrok za kontroverzno razpravo o geodinamičnem razvoju in paleogeografiji od triasa do spodnje krede. Ta orogeneza ni bila povezana z Wilsonovim ciklom Neotetide ali Alpskega Atlantika. Fokus ekskurzije je na radiolarijskih globokomorskih sedimentnih zaporedjih na robu Neotetide od triasa do spodnje krede. Zaporedja so bila odložena v različnih okoljih: v riftnih bazenih, na šelfu in kontinentalnem pobočju, v oceanu in v predgornih bazenih. Poseben poudarek bo na evoluciji v juri in spodnji kredi oziroma na geodinamičnem razvoju pred “srednjekrednimi” tektonskimi premiki. Poudarjen bo vpliv razvoja dveh oceanov na sedimentacijsko okolje, ki se je diferenciralo, ko se je potopil triasni šelf (Apulijska ali širša Jadranska plošča) med Neotetido na jugu/jugovzhodu in poznejšim Alpskim Atlantikom na severu/severozahodu. Geodinamična evolucija in medsebojni vplivi med produkcijo karbonatov, siliciklastičnim ali vulkanskim vnosom in odlaganjem kremenični sedimentov/radiolaritov v kombinaciji z asinhronim oblikovanjem bazenov omogočajo, da se v določenih obdobjih radiolariji pojavljajo skupaj z drugimi organizmi, npr. amonoidi, konodonti in kalpionelidami. Po razpadu Neotetide v srednjem triasu (zgornjem aniziju) in prenehanju produkcije karbonatov v plitvi vodi so bili po celotnem šelfu razširjeni srednjetriasni (zgornjeanizijski do ladinijski) radiolarijski, predvsem karbonatni globokomorski sedimenti. Odlaganje radiolaritov je bilo v Vzhodnih Alpah omejeno na zunanji šelf in kontinentalno pobočje ter na oceansko območje Neotetide na jugu/jugovzhodu. Razširjena produkcija karbonatov v plitvi vodi se je ponovno vzpostavila na koncu srednjega triasa (v zgornjem ladiniju) in je trajala do konca triasa. Prekinjena je bila le s kratkotrajnimi siliciklastičnimi intervali (»srednjekarnijski« obrat, dogodek Lunz). V zgornjem triasu so nastale obsežne karbonatne platforme. Odlaganje zgornjetriasnih globokomorskih sedimentov in sedimentov, ki vsebujejo radiolarije, je bilo torej omejeno predvsem na območja zunanjega šelfa, radiolariti pa so se odlagali zgolj na oceanskem dnu Neotetide. V juri, po potopitvi zgornjetriasne karbonatne platforme, so se s kremenico bogati karbonatni sedimenti ponovno odlagali na širšem območju. V spodnji juri se je začel tudi rifting na severu/severozahodu, ki je na meji med spodnjo in srednjo juro privedel do oceanizacije Alpskega Atlantika. Odpiranje Alpskega Atlantika na severu/severozahodu in sočasni začetek konvergence v Neotetidi na jugu/jugovzhodu sta hkrati delovala na poglabljanje bazenov na kontinentalnem robu, tako da je odlaganje radiolaritov v srednji juri doseglo višek. Radiolariti so se odlagali tako rekoč po celotnem potopljenem območju razen na Jadranski karbonatni platformi. Obdukcija ofiolitov z območja Neotitide od srednje jure dalje je privedla do oblikovanja tankoslojnega orogena in nastanka jarkom podobnih predgornih bazenov pred napredujočimi ofioliti. V teh bazenih so se do začetka zgornje jure odlagali melanži z radiolaritno-glinastim vezivom. V kimmeridgiju in tithoniju se je na novo nastalih pokrovih vzpostavila plitvovodna karbonatna produkcija, radiolariti pa so ostali omejeni na preostale globokovodne bazene. Zaradi dvigovanja orogena od zgornje jure (od tithonija) naprej in posledično erozije se je paleotopografija popolnoma spremenila. Preostali globokomorski predgorni bazeni so bili v spodnji kredi drug za drugim zapolnjeni z materialom, erodiranim z dvignjenega srednje do zgornjejurskega orogena Neotetide. Ekskurzija je speljana po enem najbolj klasičnih območij sveta, osrednjih Severnih Apneniških Alpah, s svetovno znanimi turističnimi znamenitostmi. Obiskali bomo lokacije s sedimentnimi zaporedji, iz katerih lahko razberemo medsebojno povezanost med vnosom siliciklastitov, vulkansko dejavnostjo, produkcijo karbonatov, različnimi tektonskimi dogajanji ter odlaganjem radiolaritov in drugih kremeničnih kamnin z radiolariji. Ključne besede: Zahodna Tetida, trias, jura, radiolariti, paleogeografija
28
GEORGE, ANNETTE D. "Deposition and deformation of an Early Cretaceous trench-slope basin deposit, Torlesse terrane, New Zealand." Geological Society of America Bulletin 104, no. 5 (1992): 570. http://dx.doi.org/10.1130/0016-7606(1992)104<0570:dadoae>2.3.co;2.
29
Yue, Jianwei, Xuanjia Huang, Limin Zhao, and Zifa Wang. "A Stability Analysis of the Ancient Site of Liye Based on the Strength Reduction Method." Applied Sciences 12, no. 6 (March 15, 2022): 2986. http://dx.doi.org/10.3390/app12062986.
Анотація:
Due to the effects of time and space, there is a continuous deterioration of the surface layers of earthen sites and a corresponding decline in soil stability. Evaluating the stability of these sites is very important for potential site restoration. In this study, we analyze, evaluate, and summarize the factors that adversely affect the ancient moat site in Liye, a town of Longshan County, Hunan Province, China, through on-site investigation, sampling, and testing. An X-ray diffractometer and a scanning electron microscope were used to analyze the chemical composition and microstructure of the soil sample of the trench, and the ABAQUS software was used to produce two-dimensional models of seriously damaged areas. Using the strength reduction method, we obtained the minimum safety factor of the trench under its natural state and after rainfall; thus, the stability of the trench was examined under different working conditions. Additionally, we evaluated the safety and stability performance of the more dangerous sections to provide a basis for the safety evaluation, protection, and repair of the trench. The results show that rain erosion, freeze–thaw cycles, and man-made damage are the primary factors contributing to a deterioration of the soil site. The safety factor of the trench is found to decrease with increases in water content; thus, water has an impact on the strength of the site wall. The wall soil has larger pores and more initial cracks than does the trench soil, which is easy to peel off. As a result, there is a high probability of a secondary deformation of the wall slope. Our results identify the real state of the existing site and provide both a basis for stability evaluation and a scientific formulation for restoration schemes.
30
Underwood, M. B., G. F. Moore, A. Taira, A. Klaus, M. E. J. Wilson, C. L. Fergusson, S. Hirano, and J. Steurer. "Sedimentary and Tectonic Evolution of a Trench-Slope Basin in the Nankai Subduction Zone of Southwest Japan." Journal of Sedimentary Research 73, no. 4 (July 1, 2003): 589–602. http://dx.doi.org/10.1306/092002730589.
31
McArthur, Adam D., Julien Bailleul, Frank Chanier, Alan Clare, and William D. McCaffrey. "Lateral, longitudinal, and temporal variation in trench-slope basin fill: examples from the Neogene Akitio sub-basin, Hikurangi Margin, New Zealand." New Zealand Journal of Geology and Geophysics 65, no. 1 (October 6, 2021): 105–40. http://dx.doi.org/10.1080/00288306.2021.1977343.
32
Lemenkova, Polina. "Analysis of the difference in depths and variation in slope steepness of the Sunda Trench, Indonesia, east Indian Ocean." Revista de Geomorfologie 22, no. 1 (December 13, 2020): 21–41. http://dx.doi.org/10.21094/rg.2020.096.
Анотація:
The paper discusses geomorphology of the Sunda Trench, an oceanic trench located in eastern Indian Ocean along the Sumatra and Java Islands of the Indonesian archipelago. In particular, it analysis the difference in depths and variation in slope steepness between the two segments of the trench: the southern Java transect (coordinates 108.8°E 10.10°S to 113.0°E 10.75°S) and the northern Sumatra transect (97.5°E 1.1°S to 101.0°E 5.5°S). The thematic maps and geomorphological modelling were plotted using Generic Mapping Tools (GMT). The materials include high-resolution data on topography, geology and geophysics: GEBCO 15 arc-minute resolution grid, EGM2008 2.5 minute Earth Gravitation Model of 2008, GlobSed global 5‐arc‐minute total sediment thickness and vector geological datasets. In addition to the GEBCO-based bathymetric data, geological, topographic and geophysical maps, the results include enlarged transects for the Java and Sumatra segments, their slope gradients and cross-section profiles, derived from the bathymetric GEBCO dataset. The geomorphology framework of the Sunda Trench is largely controlled by the subduction of the Australian plate underneath the Sunda microplate. The geological processes take place in basin of the Indian Ocean at different stages of its evolution and influence the nature of the submarine geomorphology and geometric shape of the trench. Sunda Trench is seismically active part of the Pacific Ring of Fire. A large number of the catastrophic earthquakes are recorded around the trench. The histograms shows variation in depths along the segments of the Sumatra and Java. The Java segment has a bell-shaped data distribution in contrast to the Sumatra with bimodal pattern. The Java segment has the most repetitive depths at -2,500 to -5,200 m. The Sumatra transect has two peaks: 1) a classic bell-shaped peak at depths -4,500 m to -5,500 m; 2) shelf area with a peak from 0 to -1,750 m. The data at middle depths (-1,750 to -4,500 m) have a frequency <300 samples. The most frequent bathymetry for the Sumatra segment corresponds to the -4,750 m to -5,000 m (2,151 samples). Comparing to the Sumatra segment, the Java segment is deeper. For the depths >-6,000 m, there are only 138 samples for the Sumatra while 547 samples for Java. Furthermore, Java segment has more symmetrical geometric shape while Sumatra segment is asymmetric, one-sided. The Sumatra segment has a steepness of 57.86° on its eastern side (facing Sumatra Island) and a contrasting 14.58° on the western part. The Java segment has a steepness of 64.34° on its northern side (facing Java Island) and 24.95° on the southern part (facing Indian Ocean). The paper contributes to the studies of the submarine geomorphology in Indonesia.
33
Jipa, Dan C., and Cornel Olariu. "Significance of the Bucegi Conglomerate olistoliths in the Albian source-to-sink system from the Carpathian Bend basin in Romania." Interpretation 6, no. 1 (February 1, 2018): T29—T37. http://dx.doi.org/10.1190/int-2017-0030.1.
Анотація:
The presence of exotic blocks (or olistoliths) in sedimentary deposits is usually regarded as an indication of a deepwater slope environment. We evaluate olistoliths accumulated in shallow water at the upper edge of a slope setting using outcrop data. The study area is in the Bucegi Mountains in the southeast “bend” of the Carpathian Mountains in Romania. The studied deposits belong to the Bucegi Formation, a dominantly conglomerate succession of Albian age. The Lower Bucegi member has been accumulated as a large conglomerate submarine fan. The Upper Member forms a shelf-to-trench sedimentary system with deposits dominated by sandstones and conglomerates. The olistoliths are embedded in debris flow conglomerates, most of them from the Bucegi Upper Member, and a lower number from the Bucegi Lower Member. The olistoliths are all located in a small ([Formula: see text]) zone, close to the Dambovicioara source area. The olistoliths have been transported into the basin for up to 10 km on relative gentle gradients. The blocks’ deposition is restricted to the shallow-water environment on a narrow low-gradient shelf and in some instances on the upper continental slope. Within the Albian source-to-sink system, the olistoliths occurrence marks the entry zone of the land-derived detrital material into the basin and points to the main sediment transport fairways into deeper parts of the basin.
34
Li, Hua, A. J. van Loon, and Youbin He. "Cannibalism of contourites by gravity flows: explanation of the facies distribution of the Ordovician Pingliang Formation along the southern margin of the Ordos Basin, China." Canadian Journal of Earth Sciences 57, no. 3 (March 2020): 331–47. http://dx.doi.org/10.1139/cjes-2018-0225.
Анотація:
The Late Ordovician Pingliang Formation accumulated along the southern margin of the Ordos Basin in China. The convergence of the Yangtze Plate and Sino-Korean Plate led to a trench–arc–basin system during the Middle Ordovician, with a platform- and slope-dominated setting in the east where a graben complicated the overall simple paleogeographical picture, relatively parallel zones of a platform and a slope setting in the middle, and a change from platform to slope to deep marine to a trench setting in the west. This configuration resulted in various types of gravity flow deposits and contourites with different compositions and pathways. The present study focuses on the typical characteristics of contourites in the geological record and the relationships between contour currents and gravity flows. The Pingliang Formation contains eleven lithofacies grouped into five facies associations. These facies associations represent deep sea autochthonous deposits, several types of debrites, turbidites, and contourites, as well as turbidites within which the fine-grained top portion was reworked by a contour current. The various lithofacies are concentrated in different parts of the study area: micritic contourites and debrites are concentrated in the eastern part; debrites, and sandstone and siltstone turbidites are concentrated in the middle part; and calcarenitic turbidites, contourites, and reworked turbidites occur in the western part. The main contour current ran parallel to the contour lines from east to west. Although most of the contour current continually moved westward in the eastern part of the study area, a minor part split off and followed a semicircular pathway through the Fuping Graben; its velocity became reduced here so that micritic contourites were deposited. The velocity of the contour current was increased locally when it entered a confined trough in the western part of the study area. The relatively high energy of the contour current here resulted in calcarenitic contourites. The velocity of the contour current was low where it ran through an open environment, resulting in fine-grained, thin contourites in the middle part of the study area. Large turbidity currents and debris flows occurred here, and their high energy destroyed almost all earlier deposited contourites. This explains why traces of contour currents in the middle part of the study are very scarce, although the east–west-running contour current must have passed through this area.
35
Yamamoto, Yuzuru. "Dewatering structure and soft-sediment deformation controlled by slope instability: examples from the late Miocene to Pliocene Miura–Boso accretionary prism and trench-slope basin, central Japan." Marine Geology 356 (October 2014): 65–70. http://dx.doi.org/10.1016/j.margeo.2014.05.016.
36
Schwab, J. M., S. Krastel, M. Grün, F. Gross, P. Pananont, P. Jintasaeranee, S. Bunsomboonsakul, W. Weinrebe, and D. Winkelmann. "Submarine mass wasting and associated tsunami risk offshore western Thailand, Andaman Sea, Indian Ocean." Natural Hazards and Earth System Sciences 12, no. 8 (August 17, 2012): 2609–30. http://dx.doi.org/10.5194/nhess-12-2609-2012.
Анотація:
Abstract. 2-D seismic data from the top and the western slope of Mergui Ridge in water depths between 300 and 2200 m off the Thai west coast have been investigated in order to identify mass transport deposits (MTDs) and evaluate the tsunamigenic potential of submarine landslides in this outer shelf area. Based on our newly collected data, 17 mass transport deposits have been identified. Minimum volumes of individual MTDs range between 0.3 km3 and 14 km3. Landslide deposits have been identified in three different settings: (i) stacked MTDs within disturbed and faulted basin sediments at the transition of the East Andaman Basin to the Mergui Ridge; (ii) MTDs within a pile of drift sediments at the basin-ridge transition; and (iii) MTDs near the edge of/on top of Mergui Ridge in relatively shallow water depths (< 1000 m). Our data indicate that the Mergui Ridge slope area seems to have been generally unstable with repeated occurrence of slide events. We find that the most likely causes for slope instabilities may be the presence of unstable drift sediments, excess pore pressure, and active tectonics. Most MTDs are located in large water depths (> 1000 m) and/or comprise small volumes suggesting a small tsunami potential. Moreover, the recurrence rates of failure events seem to be low. Some MTDs with tsunami potential, however, have been identified on top of Mergui Ridge. Mass-wasting events that may occur in the future at similar locations may trigger tsunamis if they comprise sufficient volumes. Landslide tsunamis, emerging from slope failures in the working area and affecting western Thailand coastal areas therefore cannot be excluded, though the probability is very small compared to the probability of earthquake-triggered tsunamis, arising from the Sunda Trench.
37
Maiorova, Anastassya S., and Andrey V. Adrianov. "Deep-sea sipunculans from the Kuril Basin of the Sea of Okhotsk and the adjacent slope of the Kuril-Kamchatka Trench." Deep Sea Research Part II: Topical Studies in Oceanography 154 (August 2018): 167–76. http://dx.doi.org/10.1016/j.dsr2.2018.06.004.
38
Meisina, C. "Characterisation of weathered clayey soils responsible for shallow landslides." Natural Hazards and Earth System Sciences 6, no. 5 (September 25, 2006): 825–38. http://dx.doi.org/10.5194/nhess-6-825-2006.
Анотація:
Abstract. Shallow earth translational slides and earth flows, affecting colluvial soils derived by the weathering of the clayey bedrock, are a recurrent problem causing damage to buildings and roads in many areas of Apennines. The susceptibility assessment, e.g. slope stability models, requires the preliminary characterization of these superficial covers (lithology, geotechnical and hydraulic parameters). The aim of the work is to develop and test a methodology for the identification and mapping of weathered clayey soils responsible for shallow landslides. A test site in Northern Apennines (Province of Pavia) was selected. Argillaceous and marly successions characterize the area. Shallow landslides occurred periodically due to high intensity rainfalls. Trench pits were used for the soil profile description (lithology, structure, grade of weathering, thickness) and sampling. The main geological, topographic and geomorphologic parameters of shallow landslides were analysed. Field surveys were integrated with some geotechnical laboratory tests (index properties, suction and volumetric characteristic determination, methylene blue adsorption test, linear shrinkage, swell strain). Engineering geological zoning was carried out by grouping the superficial soils on the basis of the following attributes: topographic conditions (slope angle), landslide occurrence, lithology (grain size), geometry (thickness), lithology of the bedrock, hydrogeological and geotechnical characteristics. The resulting engineering-geological units (areas that may be regarded as homogeneous from the geomorphologic and engineering – geological point of view) were analysed in terms of shallow slope instability.
39
Liang, Xiao, Genhou Wang, Jinhan Gao, Haishui Jiang, Guoli Yuan, Dian Li, Wentao Cao, et al. "A late Permian–Triassic trench‐slope basin in the Central Qiangtang metamorphic belt, Northern Tibet: Stratigraphy, sedimentology, syndepositional deformation and tectonic implications." Basin Research 33, no. 4 (March 19, 2021): 2383–410. http://dx.doi.org/10.1111/bre.12561.
40
Ito, Makoto, Sakumi Ishimoto, Kento Ito, and Nobuhiro Kotake. "Geometry and lithofacies of coarse-grained injectites and extrudites in a late Pliocene trench-slope basin on the southern Boso Peninsula, Japan." Sedimentary Geology 344 (October 2016): 336–49. http://dx.doi.org/10.1016/j.sedgeo.2016.02.015.
41
Gani, M. Royhan, and M. Mustafa Alam. "Trench-slope controlled deep-sea clastics in the exposed lower Surma Group in the southeastern fold belt of the Bengal Basin, Bangladesh." Sedimentary Geology 127, no. 3-4 (September 1999): 221–36. http://dx.doi.org/10.1016/s0037-0738(99)00050-0.
42
Hinzen, K. G., K. Reamer, and T. Rose. "Results of Analysis of Digital Elevation Models Used Site Selection for Paleoseismological Investigations at the Rurrand Fault." Netherlands Journal of Geosciences 80, no. 3-4 (December 2001): 109–17. http://dx.doi.org/10.1017/s0016774600023775.
Анотація:
AbstractTopographic and morphologic models based on detailed Digital Elevation Models (DEM) of the Rur Graben, in particular a 33 km section of the Rurrand Fault, proved to be essential in preliminary investigations for the site selection of a trench for detailedpaleoseismologicalinvestigations. The entire DEM in the 33 km Jülich-Düren area displayed as a color-shaded terrain map clearly illustrates the main features of the eastern border fault of the Rur Graben. As investigations concentrated on the 8x6 km Stetternich-Hambach section of the Rurrand fault, the use of contoured topographic, gray-shaded terrain and terrain slope maps helped delineate the main features of the surface fault expression. On the basis of topographic profiles constructed from the DEM, no fault scarp could be identified; however, the detailed surveying results from two geophysical profiles correlated well with the topographic data.
43
Kamenev, Gennady M. "Three new deep-sea species of Thyasiridae (Mollusca: Bivalvia) from the abyssal plain of the northwestern Pacific Ocean and hadal depths of the Kuril-Kamchatka Trench." PeerJ 8 (November 25, 2020): e10405. http://dx.doi.org/10.7717/peerj.10405.
Анотація:
The Thyasiridae is the most species-rich family of bivalves in the abyssal and hadal zones of the northwestern Pacific Ocean. In recent years, with at least 14 thyasirid species found in that region at depths exceeding 3,000 m. Some of them are the numerically dominant species in bottom communities. However, all members in that family have not yet been identified to the species level. Based on the material collected from 1953 to 2016 by five deep-sea expeditions, three new species of Thyasiridae (Mollusca: Bivalvia) are described from the abyssal and hadal zones of the northwestern Pacific. “Axinulus” roseus sp. nov. was found in the Kuril-Kamchatka Trench at 9,000–9,583 m depth. This species has a large rhomboidal shell with strong commarginal sculpture, a well defined, long and deep lunule and escutcheon without an auricle, a ctenidium consisting of a single demibranch, extensively lobed lateral pouches, and a large prodissoconch with specific sculpture. It is one of the dominant species in terms of abundance in macrobenthic communities in the deepest basin of the Kuril-Kamchatka Trench with a population density of up to 396 ind. m−2. The species has a shell length of up to 9.0 mm and it is the largest thyasirid with a single demibranch. “Axinulus” oliveri sp. nov. was found in a vast region of the northwestern Pacific on the abyssal plain adjacent to the Kuril-Kamchatka Trench, on the abyssal slope of the Kuril Islands, and in the Kuril-Kamchatka Trench at 4,648–6,168 m depth. This species is characterized by its ovate-rhomboidal shell, a well defined, deep and long escutcheon with a distinct auricle, a ctenidium with a single demibranch, and extensively lobed lateral pouches. It is widespread in the northwestern Pacific and forms populations with a density of up to 36 ind. m−2. Scanning electron microscopic observation of the gills of “A.” roseus sp. nov. and “A.” oliveri sp. nov. revealed that these species are not chemosymbiotic. “Axinulus” roseus sp. nov. and “A.” oliveri sp. nov. are provisionally assigned to the genus Axinulus, because they differ from the type species of the genus in a number of morphological and anatomical features. Parathyasira fragilis sp. nov. was found on the abyssal plain adjacent to the Kuril-Kamchatka Trench at 5,249–5,399 m depth. This species is distinguished by its very thin, fragile, dorsoventrally elongated, rhomboidal shell with very long anterodorsal margin and a long, wide, flat lunule. The taxonomic position of the new species is discussed.
44
Burgreen, Blair, and Stephan Graham. "Evolution of a deep-water lobe system in the Neogene trench-slope setting of the East Coast Basin, New Zealand: Lobe stratigraphy and architecture in a weakly confined basin configuration." Marine and Petroleum Geology 54 (June 2014): 1–22. http://dx.doi.org/10.1016/j.marpetgeo.2014.02.011.
45
Kushtan, D. P., and D. V. Kuzmich. "STUDENETS-BUCHATSKA — THE NEW SETTLEMENT OF SCYTHIAN PERIOD IN THE MID-DNIEPER BASIN." Archaeology and Early History of Ukraine 33, no. 4 (December 25, 2019): 213–19. http://dx.doi.org/10.37445/adiu.2019.04.12.
Анотація:
The paper introduces the archaeological materials discovered in 2018 on the territory of Studenets village of Kaniv district, Cherkasy region. Here, along Buchatska Street, the site of Scythian Age was stumbled upon while digging the water-pipe trench. The site included the accumulation of ceramic vessels, laying compactly on the same level. Some of them were turned upside down (fig. 4).
In total six vessels have been discovered (fig. 6). Three of them are kitchen pots ornamented with finger-prints on the edge and neck. Three other vessels are tableware with more thorough surface: two pots and a black-glazed conical bowl. The typological features of the ceramics allow to date the group to the late 5th—4th centuries BC.
The discovered object as well as the surface finds indicate the presence of the Early Iron Age settlement here. It occupied the middle part of the slope of watershed terrace facing to the Dnieper. On both sides the settlement is bounded by the upper spurs of the spring which, connecting with each other, form a stream flowing into the Kaniv reservoir after 2 km. The approximate area of the settlement is about 5 hectares (fig. 2). Most likely, it belongs to the economic district of the Scythian settlement «Viha» with an area of 27 hectares, located 3 km to the northeast, near the village of Buchak (fig. 1).
The materials, being introduced into the scientific circulation, will complement the map of the archeological sites of Trakhtemiriv peninsula, as well as enrich our knowledge of the material and spiritual culture of the ancient population lived here in the Early Iron Age
46
Sloss, Craig R., Stephanie Tillquist, Sarah McGill, Tiah Penny, Craig Ballington, Luke Nothdurft, Jessica Trofimovs, Mark J. Lawrence, and Christoph E. Schrank. "Sedimentology and stratigraphy of syn-subduction Miocene fine-grained turbidites deposited in first stages of trench-slope basin development: Whakataki Formation, North Island, New Zealand." Sedimentary Geology 414 (March 2021): 105819. http://dx.doi.org/10.1016/j.sedgeo.2020.105819.
47
Nogi, Yuichi, Shoichi Hosoya, Chiaki Kato, and Koki Horikoshi. "Colwellia piezophila sp. nov., a novel piezophilic species from deep-sea sediments of the Japan Trench." International Journal of Systematic and Evolutionary Microbiology 54, no. 5 (September 1, 2004): 1627–31. http://dx.doi.org/10.1099/ijs.0.03049-0.
Анотація:
Two strains of obligately piezophilic bacteria were isolated from sediment collected from the bottom surface of a small canyon on the seaward slope of the Japan Trench at a depth of 6278 m. The isolated strains, Y223GT and Y251E, are closely affiliated with members of the genus Colwellia on the basis of 16S rRNA gene sequence analysis. The G+C contents of both strains were about 39 mol%. DNA–DNA hybridization values between these strains and Colwellia reference strains were significantly lower than those accepted as the phylogenetic definition of a species. The novel strains are Gram-negative, polarly flagellated and facultatively anaerobic. The optimal pressure for growth was 60 MPa at both 4 and 10 °C; the most rapid growth rate was observed at 10 °C and 60 MPa. No growth occurred at 15 °C under any pressure studied. The major isoprenoid quinone is Q-8. The predominant cellular fatty acids are C16 : 0 and C16 : 1. Based on the taxonomic differences observed, the isolated strains appear to represent a novel obligately piezophilic Colwellia species. The name Colwellia piezophila sp. nov. (type strain Y223GT=JCM 11831T=ATCC BAA-637T) is proposed.
48
Morey, A. E., C. Goldfinger, C. E. Briles, D. G. Gavin, D. Colombaroli, and J. E. Kusler. "Are great Cascadia earthquakes recorded in the sedimentary records from small forearc lakes?" Natural Hazards and Earth System Sciences 13, no. 10 (October 9, 2013): 2441–63. http://dx.doi.org/10.5194/nhess-13-2441-2013.
Анотація:
Abstract. Here we investigate sedimentary records from four small inland lakes located in the southern Cascadia forearc region for evidence of earthquakes. Three of these lakes are in the Klamath Mountains near the Oregon–California border, and one is in the central Oregon Coast range. The sedimentary sequences recovered from these lakes are composed of normal lake sediment interbedded with disturbance event layers. The thickest of these layers are graded, and appear to be turbidites or linked debrites (turbidites with a basal debris-flow deposit), suggesting rapid deposition. Variations in particle size and organic content of these layers are reflected in the density and magnetic susceptibility data. The frequency and timing of these events, based on radiocarbon ages from detrital organics, is similar to the offshore seismogenic turbidite record from trench and slope basin cores along the Cascadia margin. Stratigraphic correlation of these anomalous deposits based on radiocarbon ages, down-core density, and magnetic susceptibility data between lake and offshore records suggest synchronous triggering. The areal extent and multiple depositional environments over which these events appear to correlate suggest that these deposits were most likely caused by shaking during great Cascadia earthquakes.
49
Blamey, Nigel J. F., Karem Azmy, and James Conliffe. "Geochemistry and diagenetic history of the Ordovician Lower Head Formation sandstones, western Newfoundland, Canada." Canadian Journal of Earth Sciences 53, no. 12 (December 2016): 1501–10. http://dx.doi.org/10.1139/cjes-2015-0169.
Анотація:
The Lower Head Formation in the Parson’s Pond area (western Newfoundland, Canada) comprises siltstones with very fine grained to fine-grained sandstones. Petrography confirms that these sandstones are matrix rich, essentially wackes, with detrital minerals including quartz, feldspar, biotite, and numerous accessory minerals. Observed petrographic features suggest that the Lower Head sediments are the distal product of erosion, with sediment sourced from the Dashwoods microcontinent and Lushs Bight oceanic tract and thoroughly mixed in an earlier basin prior to final deposition in a trench slope basin. The Lower Head Formation sandstones have low porosity, with early diagenetic cements (C1) and later calcite in crosscutting calcite veinlets (C2). Petrographic, isotopic, and fluid inclusion analyses indicate that C1 cements formed during the early stages of diagenesis. Both δ13C and δ18O isotopes for the C1 calcite cements are isotopically heavier than the C2 calcite veins. Fluid inclusion homogenization temperatures for the later crosscutting C2 calcite generally range between 78 and 116 °C, with a mean of 100.7 °C (±9.75 °C) and fluid salinities of 5.41–15.98 equiv. wt.% NaCl. Fluid inclusion gas analysis from C2 calcite confirms that CO2/CH4 generally has an inverse correlation with N2/Ar. Petroleum-bearing fluid inclusions were also recorded in C2 calcite cements, indicating that these fractures were conduits for hydrocarbon migration prior and (or) during cementation. However, the early cementation and associated low porosity of the Lower Head Formation sandstones indicate that they offer restricted pathways to migrating fluids and volatiles, and any hydrocarbon migration must have been fracture controlled.
50
Matsumoto, T., M. Kimura, M. Nakamura, and T. Ono. "Large-scale slope failure and active erosion occurring in the southwest Ryukyu fore-arc area." Natural Hazards and Earth System Sciences 1, no. 4 (December 31, 2001): 203–11. http://dx.doi.org/10.5194/nhess-1-203-2001.
Анотація:
Abstract. The southwestern Ryukyu area east of Taiwan Island is an arcuate boundary between Philippine Sea Plate and Eurasian Plate. The topographic features in the area are characterised by (1) a large-scale amphitheatre off Ishigaki Island, just on the estimated epicentre of the tsunamigenic earthquake in 1771, (2) lots of deep sea canyons located north of the amphitheatre, (3) 15–20 km wide fore-arc basin, (4) 15–20 km wide flat plane in the axial area of the trench, (5) E-W trending half grabens located on the fore-arc area, etc., which were revealed by several recent topographic survey expeditions. The diving survey by SHINKAI6500 in the fore-arc area on a spur located 120 km south of Ishigaki Island was carried out in 1992. The site is characterised dominantly by rough topography consisting of a series of steep slopes and escarpments. A part of the surface is eroded due to the weight of the sediment itself and consequently the basement layer is exposed. The site was covered with suspended particles during the diving, due to the present surface sliding and erosion. The same site was resurveyed in 1997 by ROV KAIKO, which confirmed the continuous slope failure taking place in the site. Another example that was observed by KAIKO expedition in 1997 is a largescale mud block on the southward dipping slope 80 km south of Ishigaki Island. This is apparently derived from the shallower part of the steep slope on the southern edge of the fan deposit south of Ishigaki Island. The topographic features suggest N-S or NE-SW tensional stress over the whole study area. In this sense, the relative motion between the two plates in this area is oblique to the plate boundary. So, the seaward migration of the plate boundary may occur due to the gravitational instability at the boundary of the two different lithospheric structures. This is evidenced by a lack of accretionary sediment on the fore-arc and the mechanism of a recent earthquake which occurred on 3 May 1998 in the Philippine Sea Plate 250 km SSE of Ishigaki Island.