Journal articles: 'Radiolaria, Fossil. Marine sediments'

1

Casey, Richard E. "Radiolaria." Notes for a Short Course: Studies in Geology 18 (1987): 213–47. http://dx.doi.org/10.1017/s027116480000155x.

Full text

Abstract:

Radiolaria are marine holoplanktonic animal-like protists belonging to the Superclass Actinopodea of the Subphylum Sarcodina. When biologists speak of radiolarians they usually mean the subgroup Acantharia that are common in nearshore waters and are sometimes involved in plankton blooms. When paleontologists speak of radiolarians they usually mean the subgroups preserved in the fossil record; the Polycystina (or polycystine) encompassing Spumellaria and Nassellaria, which possess solid opaline skeletal structures, and the Phaeodaria (or phaeodarians), which possess hollow skeletal structures of an admixture of silica and organic matter.

APA, Harvard, Vancouver, ISO, and other styles

2

Olivero, Eduardo B., and Maria I. López Cabrera. "EuflabellaN. Igen.: Complex Horizontal Spreite Burrows in Upper Cretaceous–Paleogene Shallow-Marine Sandstones of Antarctica and Tierra del Fuego." Journal of Paleontology 87, no. 3 (May 2013): 413–26. http://dx.doi.org/10.1666/12-088.1.

Full text

Abstract:

Fine-grained sandstones and siltstones of Late Cretaceous to Eocene age in Antarctica and Tierra del Fuego yield an association of well-known shallow-marine trace fossils. Among them stick out complex spreite burrows, which are formally described asEuflabellan. igen. and subdivided into five ichnospecies with different burrowing programs and occurrences. As shown by concentrations of diatoms, radiolarians, foraminifers, and calcispheres in particular backfill lamellae, the unknown trace makers lived on fresh detritus from the surface as well as the burrowed sediment. In some ichnospecies, vertical sections show that the spreite is three-dimensionally meandering in upward direction and that upper laminae tend to rework the upper backfill of the folds underneath. This could mean a second harvest, after cultivated bacteria had time to ferment refractory sediment components, which the metazoan trace maker had been unable to digest before.

APA, Harvard, Vancouver, ISO, and other styles

3

Haggart, James W., J. Brian Mahoney, Michelle Forgette, Elizabeth S. Carter, Claudia J. Schröder-Adams, Catherine I. MacLaurin, and Arthur R. Sweet. "Paleoenvironmental and chronological constraints on the Mount Tatlow succession, British Columbia: first recognition of radiolarian and foraminiferal faunas in the Intermontane Cretaceous back-arc basins of western Canada1This article is one of a series of papers published in this Special Issue on the theme of New insights in Cordilleran Intermontane geoscience: reducing exploration risk in the mountain pine beetle-affected area, British Columbia.2Geological Survey of Canada Contribution 20100279." Canadian Journal of Earth Sciences 48, no. 6 (June 2011): 952–72. http://dx.doi.org/10.1139/e11-019.

Full text

Abstract:

The Cretaceous succession at Mount Tatlow, British Columbia, is a cornerstone of Cordilleran stratigraphy, preserving a mostly continuous record of upper Lower Cretaceous to lower Upper Cretaceous sedimentary strata. The succession is capped by volcanic strata of the Powell Creek formation. Lithofacies assemblages within the Mount Tatlow succession reflect sedimentation in a deep-water submarine fan system at the base of the section, to overlying submarine-fan and to pro-deltaic deposition, and, finally, to delta-plain sedimentation at the top of the succession. Radiolarian and foraminifer fossils from the lower part of the Mount Tatlow section are the first recovered from the Intermontane basins of British Columbia and indicate a middle Albian to Cenomanian age, most likely Cenomanian. The presence of these fossils indicates that open-marine conditions existed locally in the basin at this time, but the strongly altered and pyritized nature of the fauna suggests that a reducing environment fostered early diagenetic pyritization processes in the subsurface sediments. Detrital zircon populations collected from the succession are in agreement with the paleontological ages.

APA, Harvard, Vancouver, ISO, and other styles

4

Dickens, Angela F., Yves Gélinas, Caroline A. Masiello, Stuart Wakeham, and John I. Hedges. "Reburial of fossil organic carbon in marine sediments." Nature 427, no. 6972 (January 2004): 336–39. http://dx.doi.org/10.1038/nature02299.

Full text

APA, Harvard, Vancouver, ISO, and other styles

5

Streiker, Scott, and Rachel Smith. "The NEST Laboratory: The Art of a Multi-User Facility." Microscopy Today 14, no. 6 (November 2006): 52–55. http://dx.doi.org/10.1017/s1551929500058909.

Full text

Abstract:

Radiolaria are marine protozoa that have thrived in the world's oceans for millions of years. They are particularly unique among marine plankton in that they build silica skeletons, which have allowed them to be preserved in the fossil record. These skeletons are ornate and complex and often demonstrate perfect geometric form and symmetry. The complex and beautiful glass-like structures are visually interesting when examined with electron microscopy. These attributes, coupled with their availability, size, ease of mounting and preparation make them superb specimens for introducing students to the use of electron microscopy (EM).

APA, Harvard, Vancouver, ISO, and other styles

6

Haslett, Simon K., and Paul D. Robinson. "Detecting radiolaria in the field." Journal of Micropalaeontology 10, no. 1 (August 1, 1991): 22. http://dx.doi.org/10.1144/jm.10.1.22.

Full text

Abstract:

Abstract. Radiolaria can be preserved in all types of marine sedimentary rocks, the method for their extraction being dependent on the mineralogy of the radiolarian test and the nature of the rock-type in which they occur. In the past radiolaria could only be viewed in thin section (Hinde, 1890; Hinde & Fox, 1895), with no method of detecting the presence of radiolaria prior to sectioning. Modern extraction techniques are normally laboratory based and use hazardous chemicals, therefore it is advantageous to establish the radiolarian content of the sample before collection and transportation back to the laboratory. This can be achieved in a number of ways:-1. Non-lithified sediments. Radiolaria are separated from the sediment by washing the sample over a set of small sieves. Two mesh sizes should be used, a coarse mesh around 150μm to separate large litho-fragments, and a fine mesh no greater than 63μm to concentrate the radiolaria. The fine fraction is then washed with dilute hydrochloric acid (HCl) to eliminate the calcareous microfossils, leaving a pure radiolarian sludge, which is dried on filter paper.2. Siliceous rock-types. Methods for extracting radiolaria from cherts have been in use since the early 1970’s (Dumitrica, 1970; Pessagno & Newport, 1972), and have recently been applied to field-work (Cordey & Krauss, 1990). The recognition of fossiliferous bedded cherts is possible with the use of a hand-lens in good sunlight. If radiolaria are present, they should be detectable as small protrusions, especially along laminae. To extract the radiolaria, break up the sample. . .

APA, Harvard, Vancouver, ISO, and other styles

7

McLoughlin, Stephen. "Plant fossil distributions in some Australian Permian non-marine sediments." Sedimentary Geology 85, no. 1-4 (May 1993): 601–19. http://dx.doi.org/10.1016/0037-0738(93)90104-d.

Full text

APA, Harvard, Vancouver, ISO, and other styles

8

Hendy, Austin J. W. "The influence of lithification on Cenozoic marine biodiversity trends." Paleobiology 35, no. 1 (2009): 51–62. http://dx.doi.org/10.1666/07047.1.

Full text

Abstract:

Recent research has corroborated the long-held view that the diversity of genera within benthic marine communities has increased from the Paleozoic to the Cenozoic as much as three- to fourfold, after mitigating for such biasing influences as secular variation in time-averaging and environmental coverage. However, these efforts have not accounted for the considerable increase in the availability of unlithified fossiliferous sediments in strata of late Mesozoic and Cenozoic age. Analyses presented here on the Cenozoic fossil record of New Zealand demonstrate that unlithified sediments not only increase the amount of fossil material and hence the observed diversity therein, but they also preserve a pool of taxa that is compositionally distinct from lithified sediments. The implication is that a large component of the difference in estimates of within-community diversity between Paleozoic and Cenozoic assemblages may relate to the increased availability of unlithified sediments in the Cenozoic.

APA, Harvard, Vancouver, ISO, and other styles

9

Lejzerowicz, Franck, Philippe Esling, Wojciech Majewski, Witold Szczuciński, Johan Decelle, Cyril Obadia, Pedro Martinez Arbizu, and Jan Pawlowski. "Ancient DNA complements microfossil record in deep-sea subsurface sediments." Biology Letters 9, no. 4 (August 23, 2013): 20130283. http://dx.doi.org/10.1098/rsbl.2013.0283.

Full text

Abstract:

Deep-sea subsurface sediments are the most important archives of marine biodiversity. Until now, these archives were studied mainly using the microfossil record, disregarding large amounts of DNA accumulated on the deep-sea floor. Accessing ancient DNA (aDNA) molecules preserved down-core would offer unique insights into the history of marine biodiversity, including both fossilized and non-fossilized taxa. Here, we recover aDNA of eukaryotic origin across four cores collected at abyssal depths in the South Atlantic, in up to 32.5 thousand-year-old sediment layers. Our study focuses on Foraminifera and Radiolaria, two major groups of marine microfossils also comprising diverse non-fossilized taxa. We describe their assemblages in down-core sediment layers applying both micropalaeontological and environmental DNA sequencing approaches. Short fragments of the foraminiferal and radiolarian small subunit rRNA gene recovered from sedimentary DNA extracts provide evidence that eukaryotic aDNA is preserved in deep-sea sediments encompassing the last glacial maximum. Most aDNA were assigned to non-fossilized taxa that also dominate in molecular studies of modern environments. Our study reveals the potential of aDNA to better document the evolution of past marine ecosystems and opens new horizons for the development of deep-sea palaeogenomics.

APA, Harvard, Vancouver, ISO, and other styles

10

Haslett, Simon K. "Late Neogene-Quaternary radiolarian biostratigraphy: a brief review." Journal of Micropalaeontology 23, no. 1 (May 1, 2004): 39–47. http://dx.doi.org/10.1144/jm.23.1.39.

Full text

Abstract:

Abstract. Since the 1950s, it has become apparent that Radiolaria have significant biostratigraphical potential throughout Phanerozoic time, including the Late Neogene and Quaternary. Radiolarian biozonation schemes for this period have been developed, including a Standard Tropical Zonation, which illustrates the pan-oceanic application of radiolarian biostratigraphy to Pliocene–Quaternary sediments. The biostratigraphical resolution obtainable using Radiolaria is equivalent to other microfossil groups, such as planktonic foraminifera. The recognition of abundance events of Cycladophora davisiana, and of some other species, are an alternative radiolarian dating technique for the Pliocene–Quaternary, akin to dating sediment using oxygen stable isotope (δ18O) records and with similar resolution. A number of studies have used astronomical timescales, derived from orbitally tuning δ18O and gamma ray attenuation porosity evaluator (GRAPE) records, to provide ages for radiolarian biodatums. This approach should be adopted as a more accurate alternative to palaeomagnetic chronologies with their inherent flaws. This commentary concludes that Radiolaria are important microfossils and, as a group, continue to offer significant potential as a biostratigraphical tool in future studies of the marine Pliocene–Quaternary.

APA, Harvard, Vancouver, ISO, and other styles

11

Egorova, E. N. "Fossil bivalves in marine sediments of Vestfold Hills in Eastern Antarctica." Biology Bulletin 43, no. 7 (December 2016): 619–27. http://dx.doi.org/10.1134/s1062359016070050.

Full text

APA, Harvard, Vancouver, ISO, and other styles

12

KAGEMORI, K., N. AIKAWA, K. ISHIMARU, S. KAWAI, M. YUKAWA, H. IMASEKI, K. SERA, and S. FUTATSUGAWA. "SULFUR IN A FOSSIL WOOD FROM THE PLEISTOCENE MARINE CLAY." International Journal of PIXE 14, no. 01n02 (January 2004): 67–73. http://dx.doi.org/10.1142/s0129083504000112.

Full text

Abstract:

In anoxic marine sediments sulfur is considered to be essential to the formation of humic substances. It is also estimated that sulfur may play a crucial role in the degradation of wood buried in marine sediments. In order to confirm this prediction, we observed the tissue of fossil wood from the marine clay aged 1.1 million years by polarizing microscopy and SEM before the determination of its sulfur content by PIXE and EDXA, and its distribution by μ-PIXE. Results show that the sample contained about 6000 μg/g of total sulfur and tracheid cells with birefringence, which have probably preserved the original wood components contain less sulfur compared to those without birefringence, which are heavily degraded. This might suggest the participation of sulfur in the degradation or the formation of humic substances occurred in wood tissue during diagenesis.

APA, Harvard, Vancouver, ISO, and other styles

13

Morrison, Kurt, Gareth J. Dyke, and Luis M. Chiappe. "Cretaceous fossil birds from Hornby Island (British Columbia)." Canadian Journal of Earth Sciences 42, no. 12 (December 1, 2005): 2097–101. http://dx.doi.org/10.1139/e05-081.

Full text

Abstract:

We present the first records of Mesozoic fossil birds to be described from British Columbia. New fossil avians from the Campanian Northumberland Formation on Hornby Island (Strait of Georgia) add to the known distributions of two groups of fossil birds during the latter stage of the Mesozoic. New specimens referred to the clades Ornithurae and Enantiornithes demonstrate the presence of a diverse marine avifauna in Canadian Pacific marine sediments prior to the CretaceousTertiary (KT) boundary. These new fossil bird remains from coastal rocks on the west coast of British Columbia lend further support to suggestions that ocean-going birds were important constituents of marine ecosystems in the terminal stages of the Mesozoic.

APA, Harvard, Vancouver, ISO, and other styles

14

Kao, S. J., R. G. Hilton, K. Selvaraj, M. Dai, F. Zehetner, J. C. Huang, S. C. Hsu, et al. "Preservation of terrestrial organic carbon in marine sediments off shore Taiwan: mountain building and atmospheric carbon dioxide sequestration." Earth Surface Dynamics Discussions 1, no. 1 (July 17, 2013): 177–206. http://dx.doi.org/10.5194/esurfd-1-177-2013.

Full text

Abstract:

Abstract. Geological sequestration of atmospheric carbon dioxide (CO2) can be achieved by the erosion of organic carbon (OC) from the terrestrial biosphere and its burial in long-lived marine sediments. Rivers on mountain islands of Oceania in the western Pacific have very high rates of OC export to the ocean, yet its preservation offshore remains poorly constrained. Here we use the OC content (Corg, %), radiocarbon (Δ14Corg) and stable isotope (δ13Corg) composition of sediments offshore Taiwan to assess the fate of terrestrial OC. We account for rock-derived fossil OC to assess the preservation of OC eroded from the terrestrial biosphere (non-fossil OC) during flood discharges (hyperpycnal river plumes) and when river inputs are dispersed more widely (hypopycnal). The Corg, Δ14Corg and δ13Corg of marine sediment traps and cores indicate that during flood discharges, terrestrial OC is transferred efficiently to the deep ocean and accumulates offshore with little evidence for terrestrial OC loss. In marine sediments fed by dispersive river inputs, the Corg, Δ14Corg and δ13Corg are consistent with mixing of marine OC and terrestrial OC and suggest that efficient preservation of terrestrial OC (> 70%) is also associated with hypopycnal delivery. Re-burial of fossil OC is pervasive. Our findings from Taiwan suggest that erosion and marine burial of terrestrial non-fossil OC may sequester > 8 TgC yr−1 across Oceania, a significant geological CO2 sink which requires better constraint. We postulate that mountain islands of Oceania provide strong link between tectonic uplift and the carbon cycle, one moderated by the climatic variability that controls terrestrial OC delivery to the ocean.

APA, Harvard, Vancouver, ISO, and other styles

15

Gustavson, Thomas C., and T. Delevoryas. "Caulerpa-like marine alga from Permian strata, Palo Duro Basin, West Texas." Journal of Paleontology 66, no. 1 (January 1992): 160–61. http://dx.doi.org/10.1017/s0022336000033564.

Full text

Abstract:

A fossil counterpart to ths extant marine noncalcareous green algal genus Caulerpa was recovered from Permian (Wolfcampian) marine sediments of the Palo Duro Basin, a part of the larger Permian Basin, West Texas. These fossil algal remains were recognized in core from the Department of Energy/Stone and Webster Engineering Corporation No. 1 Zeech well (Figure 1). The fossil form is described and compared to a morphologically similar extant species of Caulerpa. The geologic setting of the Palo Duro Basin is also briefly described as is the environment in which the modern algal genus Caulerpa lives.

APA, Harvard, Vancouver, ISO, and other styles

16

Tolosa, I., S. Fiorini, B. Gasser, J. Martín, and J. C. Miquel. "Carbon sources in the Beaufort Sea revealed by molecular lipid biomarkers and compound specific isotope analysis." Biogeosciences Discussions 9, no. 10 (October 12, 2012): 13925–85. http://dx.doi.org/10.5194/bgd-9-13925-2012.

Full text

Abstract:

Abstract. Molecular lipid biomarkers (hydrocarbons, alcohols, sterols and fatty acids) and compound specific isotope analysis of suspended particulate organic matter (SPM) and surface sediments of the Mackenzie Shelf and slope (Southeast Beaufort Sea, Arctic Ocean), were studied in summer 2009. The concentrations of the molecular lipid markers, characteristic of known organic matter sources, were grouped and used as proxies to evaluate the relative importance of fresh algal, detrital algal, fossil, C3 terrestrial plants, bacterial and zooplankton material in the sedimentary organic matter (OM). Fossil and detrital algal contributions were the major fractions of the freshwater SPM from the Mackenzie River with ~34% each of the total molecular biomarkers. Fresh algal, C3 terrestrial, bacterial and zooplanktonic components represented much lower percentages, 17, 10, 4 and < 1%, respectively. In marine SPM from the Mackenzie slope, the major contributions were fresh and detrital algal components (> 80%) with a minor contribution of fossil and C3 terrestrial biomarkers. Characterization of the sediments revealed a major sink of refractory algal material mixed with some fresh algal material, fossil hydrocarbons and a small input of C3 terrestrial sources. In particular, the sediments from the shelf and at the mouth of the Amundsen Gulf presented the highest contribution of detrital algal material (60–75%) whereas those from the slope contained the highest proportion of fossil (40%) and C3 terrestrial plant material (10%). Overall, considering that the detrital algal material is marine derived, autochthonous sources contributed more than allochthonous sources to the OM lipid pool. Using the ratio of an allochthonous biomarker (normalized to total organic carbon, TOC) found in the sediments to those measured at the river mouth water, we estimated that the fraction of terrestrial material preserved in the sediments accounted for 30–40% of the total carbon in the inner shelf sediments, 17% in the outer shelf and Amundsen Gulf and up to 25% in the slope sediments.

APA, Harvard, Vancouver, ISO, and other styles

17

Izumi, Kentaro, and Kazuko Yoshizawa. "Star-shaped trace fossil and Phymatoderma from Neogene deep-sea deposits in central Japan: probable echiuran feeding and fecal traces." Journal of Paleontology 90, no. 6 (October 11, 2016): 1169–80. http://dx.doi.org/10.1017/jpa.2016.95.

Full text

Abstract:

AbstractA co-occurrence of the ichnogenus Phymatoderma and a star-shaped horizontal trace fossil was discovered from Neogene deep-marine deposits (Misaki Formation, central Japan), and is described herein for the first time. Phymatoderma consists of a straight to slightly curved tunnel that shows first- or second-order branches. The tunnels are 5.30–27.25 mm in diameter and are filled with ellipsoidal pellets. The relatively well-preserved star-shaped trace fossil is a large horizontal structure (~18 cm×19 cm) that consists of at least 10 spokes with diameters ranging from 11.49–20.96 mm. As compared to modern analogous surface-feeding traces produced by abyssal echiuran worms and their burrow morphology, it is highly likely that the star-shaped trace fossil and Phymatoderma found from the Misaki Formation are feeding and fecal traces of ancient deep-sea echiurans, respectively. Difference in preservation potential between surface and subsurface traces may result in rare occurrence of star-shaped trace fossils as compared to Phymatoderma. Microscopic observation of the pelletal infill of Phymatoderma also reveals that the trace-maker fed on organic debris and microorganisms such as diatoms and radiolaria.

APA, Harvard, Vancouver, ISO, and other styles

18

Tolosa, I., S. Fiorini, B. Gasser, J. Martín, and J. C. Miquel. "Carbon sources in suspended particles and surface sediments from the Beaufort Sea revealed by molecular lipid biomarkers and compound-specific isotope analysis." Biogeosciences 10, no. 3 (March 26, 2013): 2061–87. http://dx.doi.org/10.5194/bg-10-2061-2013.

Full text

Abstract:

Abstract. Molecular lipid biomarkers (hydrocarbons, alcohols, sterols and fatty acids) and compound-specific isotope analysis of suspended particulate organic matter (SPM) and surface sediments of the Mackenzie Shelf and slope (southeast Beaufort Sea, Arctic Ocean) were studied in summer 2009. The concentrations of the molecular lipid markers, characteristic of known organic matter sources, were grouped and used as proxies to evaluate the relative importance of fresh algal, detrital algal, fossil, C3 terrestrial plants, bacterial and zooplankton material in the organic matter (OM) of this area. Fossil and detrital algal contributions were the major fractions of the freshwater SPM from the Mackenzie River with ~34% each of the total molecular biomarkers. Fresh algal, C3 terrestrial, bacterial and zooplanktonic components represented much lower percentages, 17, 10, 4 and <1%, respectively. In marine SPM from the Mackenzie slope, the major contributions were fresh and detrital algal components (>80%), with a minor contribution of fossil and C3 terrestrial biomarkers. Characterization of the sediments revealed a major sink of refractory algal material mixed with some fresh algal material, fossil hydrocarbons and a small input of C3 terrestrial sources. In particular, the sediments from the shelf and at the mouth of the Amundsen Gulf presented the highest contribution of detrital algal material (60–75%), whereas those from the slope contained the highest proportion of fossil (40%) and C3 terrestrial plant material (10%). Overall, considering that the detrital algal material is marine derived, autochthonous sources contributed more than allochthonous sources to the OM lipid pool. Using the ratio of an allochthonous biomarker (normalized to total organic carbon, TOC) found in the sediments to those measured at the river mouth water, we estimated that the fraction of terrestrial material preserved in the sediments accounted for 30–40% of the total carbon in the inner shelf sediments, 17% in the outer shelf and Amundsen Gulf and up to 25% in the slope sediments. These estimates are low compared to other studies conducted 5–20 yr earlier, and they support the increase in primary production during the last decade mainly because of the increase in the number of ice-free days and due to the strength and persistence of winds favouring upwelling.

APA, Harvard, Vancouver, ISO, and other styles

19

Zonneveld, K. A. F., G. J. M. Versteegh, S. Kasten, T. I. Eglinton, K. C. Emeis, C. Huguet, B. P. Koch, et al. "Selective preservation of organic matter in marine environments – processes and impact on the fossil record." Biogeosciences Discussions 6, no. 4 (July 1, 2009): 6371–440. http://dx.doi.org/10.5194/bgd-6-6371-2009.

Full text

Abstract:

Abstract. The present paper is the result of a workshop sponsored by the Research Centre Ocean Margins, the International Graduate College EUROPROX and the Alfred Wegener Institute for Polar Research. The workshop brought together specialists on organic matter degradation and on proxy-based environmental reconstruction. The paper deals with the main theme of the workshop, understanding the impact of selective degradation/preservation of organic matter (OM) in marine sediments on the interpretation of the fossil record. Special attention is paid to (A) the influence of the molecular composition of OM in relation to the biological and physical depositional environment, including new methods for determining complex organic biomolecules, (B) the impact of selective OM preservation on the interpretation of proxies for marine palaeoceanographic and palaeoclimatic reconstruction, and (C) past marine productivity and selective preservation in sediments.

APA, Harvard, Vancouver, ISO, and other styles

20

Alverson, Andrew J. "Timing marine–freshwater transitions in the diatom order Thalassiosirales." Paleobiology 40, no. 1 (2014): 91–101. http://dx.doi.org/10.1666/12055.

Full text

Abstract:

With species found throughout both marine and fresh waters, the diatom order Thalassiosirales is one of the most phylogenetically and ecologically diverse lineages of planktonic diatoms. A clear understanding of the timescale of Thalassiosirales evolution would provide novel insights into the rates and patterns of species diversification associated with major habitat shifts, as well as provide valuable context for understanding the age and evolutionary history of the model species, Cyclotella nana (= Thalassiosira pseudonana). The freshwater fossil record for Thalassiosirales is extensive, well characterized, and generally supportive of a Miocene origin for the major freshwater lineages. The marine record is, by comparison, more sparse and in many cases, unverified. The discovery of freshwater thalassiosiroids in Eocene sediments pushed the freshwater fossil record considerably further back in time, highlighting an apparent gap of some 30 million years. An alternative interpretation is that the Miocene and Eocene reports represent competing hypotheses. In the absence of additional independent and decisive fossil data, I explored the relative plausibility of these two scenarios with Bayesian relaxed molecular clock methods under a range of fossil calibration schemes. Although I found no support for the Eocene fossil dates, the two major freshwater colonization events probably occurred much earlier than previously thought—as early as the Paleocene for Cyclotella, followed by an Eocene origin for the cyclostephanoid lineage. Much of the extant freshwater diversity in both lineages traces back to the Miocene, however, giving the impression of a single Miocene origin. Efforts to infer the timescale of Thalassiosirales evolution more accurately would benefit from a systematic reevaluation of the marine fossil record and formal integration of fossil species into existing phylogenetic hypotheses.

APA, Harvard, Vancouver, ISO, and other styles

21

Peters, Shanan E. "The problem with the Paleozoic." Paleobiology 33, no. 2 (2007): 165–81. http://dx.doi.org/10.1666/06067.1.

Full text

Abstract:

Unfossiliferous marine sedimentary rocks of Phanerozoic age are known to all field-oriented paleontologists. These troublesome units are often encountered in the field, perhaps cursed roundly for a moment or two, and usually shrugged off in pursuit of the next fossiliferous interval. Paleontologists tend not to discuss barren units, and they rarely publish on the absence of a fauna from what appears to be unaltered marine rock. But aren't barren marine sediments revealing something important about their paleoenvironment and possibly about the paleoenvironments of conformably adjacent fossil-bearing units? Shouldn't paleontologists be just as interested in knowing the locations and ages of unfossiliferous sediments as they are fossiliferous strata?

APA, Harvard, Vancouver, ISO, and other styles

22

Renaudie, Johan, Effi-Laura Drews, and Simon Böhne. "The Paleocene record of marine diatoms in deep-sea sediments." Fossil Record 21, no. 2 (August 20, 2018): 183–205. http://dx.doi.org/10.5194/fr-21-183-2018.

Full text

Abstract:

Abstract. Marine planktonic diatoms, as today's ocean main carbon and silicon exporters, are central to developing an understanding of the interplay between the evolution of marine life and climate change. The diatom fossil record extends as far as the Early Cretaceous, and the late Paleogene to Recent interval is relatively complete and well documented. Their early Paleogene record, when diatoms first expanded substantially in the marine plankton, is hampered by decreased preservation (notably an episode of intense chertification in the early Eocene) as well as by observation bias. In this article, we attempt to correct for the latter by collecting diatom data in various Paleocene samples from legacy Deep Sea Drilling Project and Ocean Drilling Program deep-sea sediment sections. The results show a different picture from what previous analyses concluded, in that the Paleocene deep-sea diatoms seem in fact to have been as diverse and abundant as in the later Eocene, while exhibiting very substantial survivorship of Cretaceous species up until the Eocene.

APA, Harvard, Vancouver, ISO, and other styles

23

Marlowe, I. T., S. C. Brassell, G. Eglinton, and J. C. Green. "Long-chain alkenones and alkyl alkenoates and the fossil coccolith record of marine sediments." Chemical Geology 88, no. 3-4 (November 1990): 349–75. http://dx.doi.org/10.1016/0009-2541(90)90098-r.

Full text

APA, Harvard, Vancouver, ISO, and other styles

24

Kędzierski, M., A. Uchman, Z. Sawlowicz, and A. Briguglio. "Fossilized bioelectric wire – the trace fossil Trichichnus." Biogeosciences 12, no. 8 (April 16, 2015): 2301–9. http://dx.doi.org/10.5194/bg-12-2301-2015.

Full text

Abstract:

Abstract. The trace fossil Trichichnus is proposed as an indicator of fossil bioelectric bacterial activity at the oxic–anoxic interface zone of marine sediments. This fulfils the idea that such processes, commonly found in the modern realm, should be also present in the geological past. Trichichnus is an exceptional trace fossil due to its very thin diameter (mostly less than 1 mm) and common pyritic filling. It is ubiquitous in some fine-grained sediments, where it has been interpreted as a burrow formed deeper than any other trace fossils, below the redox boundary. Trichichnus, formerly referred to as deeply burrowed invertebrates, has been found as remnant of a fossilized intrasediment bacterial mat that is pyritized. As visualized in 3-D by means of X-ray computed microtomography scanner, Trichichnus forms dense filamentous fabric, which reflects that it is produced by modern large, mat-forming, sulfide-oxidizing bacteria, belonging mostly to Thioploca-related taxa, which are able to house a complex bacterial consortium. Several stages of Trichichnus formation, including filamentous, bacterial mat and its pyritization, are proposed to explain an electron exchange between oxic and suboxic/anoxic layers in the sediment. Therefore, Trichichnus can be considered a fossilized "electric wire".

APA, Harvard, Vancouver, ISO, and other styles

25

Kutluk, Hatice, and Yuri Mazei. "Organic-walled Fossil Testate Amoebae Records (late Cretaceous–holocene) from the Neotethyan–mediterranean Region." Journal of Foraminiferal Research 48, no. 2 (April 20, 2018): 121–41. http://dx.doi.org/10.2113/gsjfr.48.2.121.

Full text

Abstract:

Abstract The significance of fossil testate amoebae having organic shells and their application for biostratigraphical and paleoecological studies are unexplored fields, although these organisms are extensively used as bioindicators in ecological studies of Recent and Holocene environments. Some taxa of fossil testate amoebae with organic (chitinous, pseudochitinous, or proteinaceous) shells were recovered in Turkey from a series of palynological samples, ranging in age from Late Cretaceous to Holocene. A total of 202 samples were processed from sediments from 11 sites representing fluvial flood-plain, lacustrine, estuarine, and peat-swamp as well as shallow and deep marine facies. Nineteen taxa of the genera Arcella, Centropyxis, Frenzelina, Microcometes, Nebela, Phryganella, Pyxidicula, and Sphenoderia were recorded from the Late Cretaceous, Lower−Middle Eocene, Lower Miocene, and Quaternary sediments. The literature on fossil organic-walled testate amoebae records was also reviewed and compared with the findings in this study.

APA, Harvard, Vancouver, ISO, and other styles

26

Strelnikova, Nina I., and Andrey Yu Gladenkov. "Diatoms and their application in stratigraphic and paleogeographic studies." Issues of modern algology (Вопросы современной альгологии), no. 2(20) (2019): 1–38. http://dx.doi.org/10.33624/2311-0147-2019-2(20)-1-38.

Full text

Abstract:

Modern data on diatom algae – unicellular microorganisms with siliceous frustule composing Class Bacillariophyceae, are reviewed. Brief characteristic of biology, morphology, frustule structure and its elements, principles of diatom systematics, and also biogeography and ecology are given. A role of diatoms in sedimentation and peculiarities of preservation of their remains in bottom sediments are discussed. Special attention is paid to issues of effective application of data on fossil diatoms for detailed biostratigraphic subdivision, dating and correlation of sedimentary successions (first of all, marine deposits) as well as for paleoenvironmental reconstructions. General characteristic of diatom zonations proposed for marine Cretaceous and Cenozoic sediments is given. Main features of diatom evolution are discussed.

APA, Harvard, Vancouver, ISO, and other styles

27

Mahan, Shannon A., Harrison J. Gray, Jeffrey S. Pigati, Jim Wilson, Nathaniel A. Lifton, James B. Paces, and Maarten Blaauw. "A geochronologic framework for the Ziegler Reservoir fossil site, Snowmass Village, Colorado." Quaternary Research 82, no. 3 (November 2014): 490–503. http://dx.doi.org/10.1016/j.yqres.2014.03.004.

Full text

Abstract:

AbstractThe Ziegler Reservoir fossil site near Snowmass Village, Colorado (USA), provides a unique opportunity to reconstruct high-altitude paleoenvironmental conditions in the Rocky Mountains during the Last Interglacial Period. We used four different techniques to establish a chronological framework for the site. Radiocarbon dating of lake organics, bone collagen, and shell carbonate, and in situ cosmogenic 10Be and 26Al ages on a boulder on the crest of a moraine that impounded the lake suggest that the ages of the sediments that hosted the fossils are between ~140 ka and >45 ka. Uranium-series ages of vertebrate remains generally fall within these bounds, but extremely low uranium concentrations and evidence of open-system behavior limit their utility. Optically stimulated luminescence (OSL) ages (n = 18) obtained from fine-grained quartz maintain stratigraphic order, were replicable, and provide reliable ages for the lake sediments. Analysis of the equivalent dose (DE) dispersion of the OSL samples showed that the sediments were fully bleached prior to deposition and low scatter suggests that eolian processes were likely the dominant transport mechanism for fine-grained sediments into the lake. The resulting ages show that the fossil-bearing sediments span the latest part of Marine Oxygen Isotope Stage (MIS) 6, all of MIS 5 and MIS 4, and the earliest part of MIS 3.

APA, Harvard, Vancouver, ISO, and other styles

28

Fritz, William J. "Plant Taphonomy in Areas of Explosive Volcanism." Notes for a Short Course: Studies in Geology 15 (1986): 1–9. http://dx.doi.org/10.1017/s0271164800001299.

Full text

Abstract:

Coarse-grained volcaniclastic sediments are a common part of the non-marine geologic record along most continental margins. Many of these volcanic sediment units contain well-preserved assemblages of fossil plants. Because much of the work on depositional environments, dating, correlations and paleoenvironments has been derived from studies of plants, it is important to understand the processes that incorporate the plants into the volcaniclastic sediments. In this paper I plan to concentrate on processes that bury and preserve trees, logs and stumps.

APA, Harvard, Vancouver, ISO, and other styles

29

Taylor, David W., J. Michael Moldowan, and Leo J. Hickey. "Investigation of the terrestrial occurrence and biological source of the petroleum geochemical biomarker oleanane." Paleontological Society Special Publications 6 (1992): 286. http://dx.doi.org/10.1017/s2475262200008467.

Full text

Abstract:

Oleanane is a triterpane that is commonly found in Late Cretaceous (Campanian) through Cenozoic marine and deltaic rocks and related oils. Based on its affinity to the β-Amyrin group of natural products and its abundance in Tertiary deltaic sediments and oils, such as in the Niger Delta, oleanane is thought to be a geochemical fossil of terrestrial flowering plants. The β-Amyrin group forms the basis of many angiosperm triterpenoids and triterpenoid saponins. These compounds appear in moderately advanced flowering plant lineages and are often used as a defense against herbivores. This group of compounds has not been reported from any other seed plant group, including conifers.We examined a suite of middle to early Cretaceous terrestrial sediments and plant fossils for the presence of oleanane. The existence of oleanane was documented by Gas Chromatography - Mass Spectrometry (GC-MS) and confirmed with Metastable Reaction Monitoring (MRM) GC-MS.Oleanane was identified from fossil bennettitaleans, an extinct group of seed plants. Cycadeoidea paynei and C. superba are permineralized fossil stems and are from the Early Cretaceous Inyan Kara Group of the Black Hills, SD. Oleanane was also found in carbonaceous compressed leaf fossils of Dioonites from the Barremian - early Aptian (Zone I) of the Potomac Group from Richmond, VA. This increases the number of seed plant groups known to have oleanane, and is of additional interest as the bennettitaleans are thought to be closely related to angiosperms.Oleanane was not found in contemporaneous fossil conifers. Our sample consisted of fossil conifer wood collected from the Campanian Magothy Beds of Martha's Vineyard, MA; the Cenomanian Raritan Formation of Sayreville, NJ; and the Barremian - early Aptian Patuxent Formation of Greenbelt, MD.Confirmed reports of oleanane have been from Late Cretaceous and younger marine sediments. We now report oleanane from Early Cretaceous terrestrial strata of the Inyan Kara Group. In addition we systematically sampled the sequence of Cretaceous terrestrial sediments of the coastal plain of the eastern U.S.A, and found oleanane in the Barremian - early Aptian (Zone I) Potomac Group. Preliminary data indicate variation in the occurrence of oleanane in contemporaneous Early Cretaceous sites from the Potomac Group. The localities accumulated in different depositional environments and the occurrence may be controlled by lithofacies.

APA, Harvard, Vancouver, ISO, and other styles

30

Moran, Jean E., Udo Fehn, and Ray T. D. Teng. "Variations in 129I/127I ratios in recent marine sediments: evidence for a fossil organic component." Chemical Geology 152, no. 1-2 (October 1998): 193–203. http://dx.doi.org/10.1016/s0009-2541(98)00106-5.

Full text

APA, Harvard, Vancouver, ISO, and other styles

31

Demírcan, Huríye, and Alfred Uchman. "The miniature echinoid trace fossil Bichordites kuzunensis isp. nov. from early Oligocene prodelta sediments of the Mezardere Formation, Gökçeada Island, NW Turkey." Acta Geologica Polonica 62, no. 2 (June 1, 2012): 205–15. http://dx.doi.org/10.2478/v10263-012-0010-2.

Full text

Abstract:

ABSTRACT Demircan, H. and Uchman, A. 2012. The miniature echinoid trace fossil Bichordites kuzunensis isp. nov. from early Oligocene prodelta sediments of the Mezardere Formation, Gokceada Island, northwest Turkey. Acta GeologicaPolonica, 62 (2), 205-215. Warszawa. The pascichnial trace fossil Bichordites kuzunensis isp. nov. occurs as an epichnial complex structure in early Oligocene prodelta sediments of the Thrace Basin in Gokceada Island, northwest Turkey. It displays characteristics of irregular echinoid burrows such as overall shape and a double meniscate filling with a chevron dorsal suture, in addition to the feature typical of the so far monospecific Bichordites Plaziat and Mahmoudi, 1988, that is a single central core around a single drainage tube. Its miniature size can be related to the small size of the tracemaker (ontogenic feature) or to its dwarfism in a stressed deltaic environment (palaeoecological feature). Its occurrence indicates a period of fully marine conditions during accumulation of the deltaic sediments of the Mezardere Formation.

APA, Harvard, Vancouver, ISO, and other styles

32

Wysocka, Anna, Andrzej Radwański, Marcin Górka, Maciej Bąbel, Urszula Radwańska, and Michał Złotnik. "The Middle Miocene of the Fore-Carpathian Basin (Poland, Ukraine and Moldova)." Acta Geologica Polonica 66, no. 3 (September 1, 2016): 359–409. http://dx.doi.org/10.1515/agp-2016-0017.

Full text

Abstract:

Abstract Studies of Miocene sediments in the Fore-Carpathian Basin, conducted by geologists from the University of Warsaw have provided new insights on the distribution of the facies infilling the basin, particularly in the forebulge and back-bulge zones. The origin of the large-scale sand bodies, evaporitic deposits and large-scale organic buildups is discussed, described and verified. These deposits originated in variable, shallow marine settings, differing in their water chemistry and the dynamics of sedimentary processes, and are unique with regard to the fossil assemblages they yield. Many years of taxonomic, biostratigraphic, palaeoecologic and ecotaphonomic investigations have resulted in the identification of the fossil assemblages of these sediments, their age, sedimentary settings and post-mortem conditions. Detailed studies were focused on corals, polychaetes, most classes of molluscs, crustaceans, echinoderms, and fishes.

APA, Harvard, Vancouver, ISO, and other styles

33

Miura, Hideki, Kiichi Moriwaki, Hideaki Maemoku, and Kazuomi Hirakawa. "Fluctuations of the East Antarctic ice-sheet margin since the last glaciation from the stratigraphy of raised beach deposits along the Sôya Coast." Annals of Glaciology 27 (1998): 297–301. http://dx.doi.org/10.3189/1998aog27-1-297-301.

Full text

Abstract:

The fluctuation of the East Antarctic ice-shect (EAIS) margin and relative sea-level change since the last glaciation are discussed from the stratigraphy and TAMS 14C ages of raised beach deposits in the northern part of the Soya Coast.The beach deposits reveal two marine sediment layers with in situ fossil shells of Laternula elliptica, and an interbedded fluvial sediment layer. The l4C ages of fossils in the lower, older marine beds ranged from 36 to 43 ka, and in the upper, younger beds from 4.9 to 5.2 ka without reservoir correction. Neither marine layers nor in situ fossil shells were disturbed by ice-sheet loading or scouring. The interbedded fluvial sediments appear to have been deposited by a stronger fluvial process than present meltwater activity in the area. These facts lead us to the following conclusions: (1) marine transgression occurred during the last interstadial around 40 ka or the Last Intcrglacial, and in the Holocene around 5 ka: (2) the EATS possibly retreated from the northern Sôya Coast prior to the Last Glaciol Maximum (LGM); (3) the fluvial process may have occurred during a period of low sea level which may have been a warmer period than the present, probably during the late-Glaciol to postglaciol age; and (4) the EAIS did not rcadvance over these sediments during or since the LGM.

APA, Harvard, Vancouver, ISO, and other styles

34

Chan-gyu, Yun. "New Example of Cosmopolitodus hastalis (Lamniformes, Lamnidae) from the Miocene of South Korea." Zoodiversity 54, no. 5 (2020): 433–38. http://dx.doi.org/10.15407/zoo2020.05.433.

Full text

Abstract:

The author reports the discovery of an isolated juvenile tooth of an extinct lamnid shark Carcharodon hastalis from the Duho Formation, Pohang City, South Korea. This tooth is approximately 11 mm in height, suggesting a juvenile affinity of an individual this tooth originated. In life, the shark is estimated to have been approximately less than 2 m in length. This is the second reported fossil record of Carcharodon hastalis in the Korean Peninsula and the first permineralized fossil remain as well. Although largely undescribed, fossil shark assemblage of the Duho Formation is similar to those of contemporaneous Japanese marine sediments, indicating epipelagic or pelagic sharks were already diversified throughout the East sea during the Middle Miocene.

APA, Harvard, Vancouver, ISO, and other styles

35

Williams, Mark, John L. Smellie, Joanne S. Johnson, and Daniel B. Blake. "Late Miocene Asterozoans (Echinodermata) in the James Ross Island Volcanic Group." Antarctic Science 18, no. 1 (March 2006): 117–22. http://dx.doi.org/10.1017/s0954102006000113.

Full text

Abstract:

Asterozoans (Echinodermata) of Late Miocene age (6.02 ± 0.12 Ma) are preserved as external moulds in water-lain tuffs of the James Ross Island Volcanic Group (JRIVG), James Ross Island, Antarctic Peninsula. The asterozoans are complete, and appear to represent specimens suffocated after having been pinioned by rapid sedimentation on the distal fringe of an erupting sub-aqueous tuff cone. Although the coarse nature of the host sediments has obliterated the fine morphological detail of the specimens, at least one suggests evidence of entrainment by a turbidity current. A second shows evidence of detachment of the distal tip of one of its arms. In addition to fossil discoveries from glaciomarine sediments, the volcanic tuffs of the JRIVG represent a new source of fossil data that can be used to interpret the ecology and environment of the Antarctic marine shelf biota during the Neogene.

APA, Harvard, Vancouver, ISO, and other styles

36

Jiao, Li Ping, Xia Sun, and Yang Luo. "Chinese Arctic Yellow River Station Research Monitoring Program. 1. Polycyclic Aromatic Hydrocarbons in Sediment from Svalbard." Applied Mechanics and Materials 522-524 (February 2014): 25–33. http://dx.doi.org/10.4028/www.scientific.net/amm.522-524.25.

Full text

Abstract:

Surface sediments of the west coast of Svalbard near Ny-Ålesund Spitsbergen were collected. PAHs of lake sediments (mean: 260, range: 11 - 1100 ng/g dry wt) were higher than previously report of surface lake sediment in Svalbard 1995, suggesting significant PAH contamination is occurring due to long-term atmospheric transport and local coal mining and fossil fuel sources, pointing to the role of Arctic lakes as potential reservoirs of semi-volatile organic compounds, including PAHs. Compound-specific analysis revealed different PAH patterns between Svalbard lakes and European high mountain lakes, showing higher proportions of low molecular weight compounds and lower levels of high molecular weight PAHs in Svalbard lakes. PAH indicator ratios suggest that the majority of PAHs in lake sediments have pyrogenic origins (coal mining, fossil fuel and biomass combustion), while coastal marine sediments were mainly contaminated by petroleum-derived PAHs (shipping activities in coastal areas, and perhaps as a result of an oil spill in 1986). Sediment fluxes of PAHs were estimated to be 0.2 - 22 ng cm-2yr-1. The current PAH levels exceeded Canadian sediment quality guidelines, suggesting the presence of possible risks for aquatic organisms and the need for further studies.

APA, Harvard, Vancouver, ISO, and other styles

37

Gallagher, W. B. "Oligotrophic oceans and minimalist organisms: collapse of the Maastrichtian marine ecosystem and Paleocene recovery in the Cretaceous-Tertiary sequence of New Jersey." Netherlands Journal of Geosciences - Geologie en Mijnbouw 82, no. 3 (August 2003): 225–31. http://dx.doi.org/10.1017/s0016774600020813.

Full text

Abstract:

AbstractThe inner Atlantic Coastal Plain of New Jersey reveals exposures of fossiliferous Maastrichtian and Danian deposits. Recent fossil discoveries in this interval are here reported, and placed in the context of Cretaceous/Tertiary (K/T) faunal changes. The exposure at the Inversand Pit at Sewell (New Jersey) is the last active marl mine in the region, and stands as an important reference section for the many significant discoveries of vertebrate fossils produced by the marl mining industry at its zenith. Changes in planktonic populations across the K/T boundary are related to Maastrichtian/Danian marine ecosystem community reorganisation, by demonstrating changes in abundance of dominant marine invertebrates in successive fossil assemblages. Marine invertebrates with non-planktotrophic larval stages were briefly the commonest fossils preserved in the Danian sediments of this region. Late surviving examples of Cretaceous fauna now restricted to the Indo-Pacific region may imply biogeographic changes linked to the K/T mass extinction event.

APA, Harvard, Vancouver, ISO, and other styles

38

Chin, Karen, John Bloch, Arthur Sweet, Justin Tweet, Jaelyn Eberle, Stephen Cumbaa, Jakub Witkowski, and David Harwood. "Life in a temperate Polar sea: a unique taphonomic window on the structure of a Late Cretaceous Arctic marine ecosystem." Proceedings of the Royal Society B: Biological Sciences 275, no. 1652 (August 19, 2008): 2675–85. http://dx.doi.org/10.1098/rspb.2008.0801.

Full text

Abstract:

As the earth faces a warming climate, the rock record reminds us that comparable climatic scenarios have occurred before. In the Late Cretaceous, Arctic marine organisms were not subject to frigid temperatures but still contended with seasonal extremes in photoperiod. Here, we describe an unusual fossil assemblage from Devon Island, Arctic Canada, that offers a snapshot of a ca 75 Myr ago marine palaeoecosystem adapted to such conditions. Thick siliceous biogenic sediments and glaucony sands reveal remarkably persistent high primary productivity along a high-latitude Late Cretaceous coastline. Abundant fossil faeces demonstrate that this planktonic bounty supported benthic invertebrates and large, possibly seasonal, vertebrates in short food chains. These ancient organisms filled trophic roles comparable to those of extant Arctic species, but there were fundamental differences in resource dynamics. Whereas most of the modern Arctic is oligotrophic and structured by resources from melting sea ice, we suggest that forested terrestrial landscapes helped support the ancient marine community through high levels of terrigenous organic input.

APA, Harvard, Vancouver, ISO, and other styles

39

Piasecki, S., L. Stemmerik, J. D. Friderichsen, and A. K. Higgins. "Stratigraphy of the post-Caledonian sediments in the Germania Land area, North-East Greenland." Rapport Grønlands Geologiske Undersøgelse 162 (January 1, 1994): 177–84. http://dx.doi.org/10.34194/rapggu.v162.8260.

Full text

Abstract:

Sediment outliers in North-East Greenland are briefly described and dated on the basis of macro- and microscopic plant fossils. Conglomerates and sandstones at Depotnæsset are probably of Late Carboniferous age based on the content of poorly preserved spores and pollen together with Stigmaria molds. Conglomerates, sandstones and coals from localities west of Germania Land are of Early to Middle Jurassic age based on poorly preserved fossil leaves and sporomorphs. The sedimentary facies and the fossil content of the Upper Carboniferous sediments suggest that the transition between the continental Carboniferous basins of East Greenland and the marine basins of North Greenland was situated north of 78°N. The maturity of the sporomorphs suggests that the Upper Carboniferous basins subsided by 1.5–2 km in Late Carboniferous to Middle Jurassic time, whereas subsidence of the Jurassic basins was negligible.

APA, Harvard, Vancouver, ISO, and other styles

40

Sperling, Erik A. "Tackling the 99%: Can We Begin to Understand the Paleoecology of the Small and Soft-Bodied Animal Majority?" Paleontological Society Papers 19 (October 2013): 77–86. http://dx.doi.org/10.1017/s1089332600002692.

Full text

Abstract:

Not all organisms have an equal chance of entering the fossil record. Previo—us attempts to quantify this percentage suggest that for megascopic marine organisms (megafauna), ∼30% would be predicted to leave no identifiable fossils. Here, that exercise is repeated for marine macrofauna, for which ∼80% are predicted to leave no identifiable fossils. The percentage will be far higher for meiofauna, the numerically most dominant marine animals. The organisms which are often most abundant in marine sediments, such as small polychaetes and nematodes, have essentially no fossil record. Yet such organisms are ecologically important in the modern oceans, and almost certainly were in ancient environments as well, so it is useful to consider the roles they play in different ecosystems. Insight into the evolution and paleoecology of these groups can be gained by using molecular divergence estimates to infer temporal origins combined with modern distributional and ecological data. As a case study, this approach is applied to the small and soft-bodied early animal fauna living under low levels of atmospheric oxygen that likely characterized the Precambrian.

APA, Harvard, Vancouver, ISO, and other styles

41

Dyke, Gareth, Xia Wang, and Gary Kaiser. "Large fossil birds from a Late Cretaceous marine turbidite sequence on Hornby Island (British Columbia)." Canadian Journal of Earth Sciences 48, no. 11 (November 2011): 1489–96. http://dx.doi.org/10.1139/e11-050.

Full text

Abstract:

Few fossil birds and non-avian dinosaurs are known from Mesozoic sediments bordering the eastern margin of the Pacific Ocean. Here, we describe additional remains of Late Cretaceous birds from a deep-water marine turbidite sequence of the Northumberland Formation exposed on Hornby Island, British Columbia. The bones described here are referable (based on hypothesized autapomorphies) to the Cretaceous avian lineages Enantiornithes and Ornithurae and fall into at least two size classes within either lineage. This suggests the presence of multiple taxa occurring within the Northumberland Formation.

APA, Harvard, Vancouver, ISO, and other styles

42

Esperante, Raúl, Leonard Brand, Kevin E. Nick, Orlando Poma, and Mario Urbina. "Exceptional occurrence of fossil baleen in shallow marine sediments of the Neogene Pisco Formation, Southern Peru." Palaeogeography, Palaeoclimatology, Palaeoecology 257, no. 3 (January 2008): 344–60. http://dx.doi.org/10.1016/j.palaeo.2007.11.001.

Full text

APA, Harvard, Vancouver, ISO, and other styles

43

SZABO, BARNEY J. "Uranium-series dating of fossil corals from marine sediments of southeastern United States Atlantic Coastal Plain." Geological Society of America Bulletin 96, no. 3 (1985): 398. http://dx.doi.org/10.1130/0016-7606(1985)96<398:udofcf>2.0.co;2.

Full text

APA, Harvard, Vancouver, ISO, and other styles

44

Curran, H. Allen. "Trace Fossils in Quaternary, Bahamian-Style Carbonate Environments: The Modern to Fossil Transition." Short Courses in Paleontology 5 (1992): 105–20. http://dx.doi.org/10.1017/s2475263000002300.

Full text

Abstract:

Tracemaking organisms are common and diverse components of the fauna and flora of tropical, shallow-marine and coastal carbonate environments. In the shallow subtidal zone, the burrowing activity of callianassid shrimp commonly is the dominant process in the modification of original depositional fabrics (Tudhope and Scoffin, 1984; Tedesco and Wanless, 1991). Both borers and burrowers have great potential to leave their mark in tropical carbonate sediments and rocks and to become part of the fossil record.

APA, Harvard, Vancouver, ISO, and other styles

45

Jovanovic, Gordana, Stjepan Coric, and Sejfudin Vrabac. "The first evidence of marine Badenian transgression near Koceljeva (central Paratethys, Western Serbia)." Annales g?ologiques de la Peninsule balkanique 80, no. 1 (2019): 1–15. http://dx.doi.org/10.2298/gabp1901001j.

Full text

Abstract:

This paper presents the first detailed biostratigraphic investigation of deposits cropping out in stream Sumijevac near Koceljeva (western Serbia). The most important fossil communities and their significance are presented. New biostratigraphic results have been achieved by the study of calcareous nannoplankton, foraminifera and mollusks fauna which clearly indicate the presence of the lower Badenian zone (Lagenid Zone), and defines preciously time of the marine transgression in this area. Further, the revised age of the sedimentary deposits presented here provides the necessary background information for future research of the Badenian sediments of Serbia and neighbouring regions.

APA, Harvard, Vancouver, ISO, and other styles

46

Rust, Jes. "Oldest known pteroplistine cricket and other Gryllidae (Orthoptera) from the Paleogene Fur and Ølst Formations of Denmark." Insect Systematics & Evolution 30, no. 1 (1999): 35–45. http://dx.doi.org/10.1163/187631200x00192.

Full text

Abstract:

AbstractThe present paper reports on a study of 16 fossil specimens of Gryllidae from the Paleogene marine sediments of the Fur and Ølst Formations (Paleocene/Eocene) of Denmark. The oldest known Pteroplistinae, Pteroplistus danicus sp. n., is described on the basis of 2 isolated male forewings. Additional material consists of isolated male and female forewings, several almost complete female specimens, and large body fragments. The systematic position of these specimens, however, is unclear, because diagnostic characters are not preserved. Possible synapomorphic characters of the wing venation shared by P danicus sp. n., the second known fossil species of Pteroplistinae Eneopterotrypus chopardi Zeuner from the Eocene, and extant Pteroplistinae are proposed. Most of the fossil crickets derive from the Paleocene Ølst Formation. Pteroplistinae are poor flyers, thus their presence suggests near shore conditions of the former marine environment, which is confirmed by analysis of the fish fauna and other insect groups. The present geographical restriction of the Pteroplistinae to India, Vietnam, and Malaysia is presumably a consequence of climatic changes during the Cenozoic.

APA, Harvard, Vancouver, ISO, and other styles

47

Emery, K. O., A. S. Merrill, and E. R. M. Druffel. "Changed Late Quaternary Marine Environments on Atlantic Continental Shelf and Upper Slope." Quaternary Research 30, no. 3 (November 1988): 251–69. http://dx.doi.org/10.1016/0033-5894(88)90002-6.

Full text

Abstract:

About 2000 large sediment samples were collected during the early 1960s throughout the continental shelf off the Atlantic coast of the United States to establish and map sediment types including sediments relict from times of glacially low (and subsequently higher) sea levels. In about 510 of these samples we found fossil shells of mollusks remaining from environmental conditions different from those at present. Publications and collections by others contain about 70 additional samples having relict mollusks. Some of these shells indicate lower sea levels, others colder water, and still others warmer water than is now present. Radiocarbon measurements from earlier studies by us and others established the dates of colder water (late Pleistocene), and we made additional measurements to learn the dates of warmer water (about 1000 to 2000 yr B.P.). The results show reasonably enough that continental shelves are the sites of relict faunas as well as of sediments that indicate changed and complex environmental histories.

APA, Harvard, Vancouver, ISO, and other styles

48

Elorza, J., and F. Garcia-Garmilla. "Chert appearance in the Cueva-Bedón carbonate platform (upper Cretaceous, northern Spain)." Geological Magazine 130, no. 6 (November 1993): 805–16. http://dx.doi.org/10.1017/s0016756800023177.

Full text

Abstract:

AbstractNodular chert from the Cueva-Bedón carbonate platform (late Turonian-earliest Coniacian) occurs above the type 1 sequence boundary and in association with a transgressive systems tract deposit. It formed by selective replacement of grainstones-packstones, and Thalassinoides burrow fillings. Other minor types of selective silicification include the replacement of anhydrite nodules, forming quartz geodes, and the partial or total replacement of oysters and inoceramids. The chert nodules consist predominantly of microquartz with volumetrically minor fibrous quartz (length-fast chalcedony) and megaquartz. The silica has a mainly biogenic source (siliceous sponge spicules and radiolarians). Lepisphere textures that are indicative of an intermediate opal-CT precursor are evident in chert nodules, which indicates the chert formed by a maturation process from opalA to opal-CT to quartz. The δ 18O values of microquartz suggest a precipitation from marine fluids. The fabric of quartz geodes consists of irregular bands of heterometric megaquartz, quartzine and lutecite spherulites, and a well developed band of petaloidal megaquartz that contains small anhydrite inclusions. Bivalve shells are replaced mainly by fibrousquartz (quartzine-lutecite), which forms extensive beekite rings. The silica source of the replaced fossils is also biogenic, but silicification couldhave occurred by direct quartz replacement without an opal-CT precursor. Field and petrographic evidence indicate that silicification was an early diagenetic process that affected both uncompacted and compacted sediments, andwas inhibited when the dolomitization began. There seems to exist a syncrony in age (late Turonian-earliest Coniacian) between the nodular chert in the Cueva-Bedón carbonate platform and the bedded and nodular chert ofthe Plentzia carbonate turbidites in the deeper Basque Arc.

APA, Harvard, Vancouver, ISO, and other styles

49

Kędzierski, M., A. Uchman, Z. Sawlowicz, and A. Briguglio. "Fossilized bioelectric wire – the trace fossil <i>Trichichnus</i>." Biogeosciences Discussions 11, no. 12 (December 18, 2014): 17707–28. http://dx.doi.org/10.5194/bgd-11-17707-2014.

Full text

Abstract:

Abstract. The trace fossil Trichichnus is proposed as an indicator of fossil bioelectric bacterial activity at the interface oxic – anoxic zone of marine sediments. This fulfils the idea that such processes, commonly found in the modern realm, should be also present in the geological past. Trichichnus is an exceptional trace fossil due to its very thin diameter (mostly less than 1 mm) and common pyritic filling. It is ubiquitous in some fine-grained sediments, where it has been interpreted as a burrow formed deeper than any other trace fossils, below the redox boundary. Trichichnus formerly referred to as deeply burrowed invertebrates, has been found as remnant of a fossilized intrasediment bacterial mat that is pyritized. As visualized in 3-D by means of X-ray computed microtomography scanner, Trichichnus forms dense filamentous fabric, which reflects that produced by modern large, mat-forming, sulphide-oxidizing bacteria, belonging mostly to Trichichnus-related taxa, which are able to house a complex bacterial consortium. Several stages of Trichichnus formation, including filamentous, bacterial mat and its pyritization, are proposed to explain an electron exchange between oxic and suboxic/anoxic layers in the sediment. Therefore, Trichichnus can be considered a fossilized "electric wire".

APA, Harvard, Vancouver, ISO, and other styles

50

Borówka, Ryszard, and Bernard Cedro. "Holocene marine ingressions in the coastal zone of the pomeranian bay based on radiocarbon assays." Geochronometria 38, no. 1 (March 1, 2011): 85–92. http://dx.doi.org/10.2478/s13386-011-0009-6.

Full text

Abstract:

Abstract In recent years, a team at the Geology and Paleogeography Unit, Marine Sciences Institute, University of Szczecin, has been performing geological, geochronological and paleogeographic surveys in (i) the Szczecin Lagoon and Świna Gate Sandbar and (ii) the estuary section of the Rega river valley near Mrzeżyno. These studies have helped to examine and identify not only the distribution of fossil marine sediments but also their lithological and sedimentological characteristics. The age of marine ingressions and regressions in the coastal zone of the Pomeranian Bay were determined using approximately 170 radiocarbon assays. It was found that the marine ingression associated with the ‘Littorina transgression’ was not synchronous at these two areas. It started earlier in the Mrzeżyno area, ca. 8300-8200 cal BP. In that first phase, marine sediments developed as tightly packed sands containing a few fragments of shells. In several profiles, these deposits were separated from the bottom and top with layers of peat, thus allowing an indirect determination of their age. The next phase of ingression began about 7300 cal BP. These younger marine sediments already contained quite numerous shells of marine malacofauna, especially Cardium glaucum, often found in a life position. In the area of the Szczecin Lagoon and Swina Gate Sandbar, the oldest marine ingression started as early as about 7350 cal BP. The quite clear trace is a considerably thicker series of marine sands with numerous sea shells representing marine and brackish-marine environments, including Cardium glaucum shells in a life position, which made it possible to identify the age and the rate of accumulation of marine sands.

APA, Harvard, Vancouver, ISO, and other styles

Journal articles on the topic 'Radiolaria, Fossil. Marine sediments'

Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles