The taphonomy of fishes living in lacustrine environments has been extensively studied in both the laboratory and the fossil record; the taphonomy of marine fishes, however, is poorly known. Triassic marine fishes with heavy ganoid and cosmoid scales, which provided protection from rapid taphonomic loss, offer a means to examine marine fish taphonomy in the fossil record. Four genera of Early Triassic fishes (the ray-finned actinopterygians Albertonia, Bobasatrania, Boreosomus, and the lobe-finned coelacanth (sarcopterygian), Whiteia) from the Wapiti Lake, British Columbia locality of the Lower Triassic Sulphur Mountain Formation were examined in order to gain a better understanding of the taphonomy of fish in marine environments, determine ambient environmental conditions in the region during the Early Triassic, and ascertain the habitat and mode of life of the fish. Results indicate that environmental conditions that contributed to the preservation of the fossil fishes of the current study included deposition in deep, quiet waters, which reduced the odds of disarticulation, colder waters under higher pressure, which slowed decay and limited postmortem floatation, and waters that were anoxic, which discouraged predators and scavengers. In addition, the thickness of the primitive ganoid and cosmoid scales of the fossil fishes also increased their preservation potential. Taphonomic, physiological and environmental indicators suggest that Whiteia, Albertonia, and possibly Bobasatrania lived in deep, cold waters near the oxygen minimum zone, while Boreosomus lived higher in the water column. While the anatomical and physiological characteristics of modern fishes will likely continue to inhibit marine taphonomy studies, examination of ancient fish, particularly those with ganoid or cosmoid scales, may provide future avenues of research to gain a better understanding of marine fish taphonomy and provide a powerful tool to examine ancient fish behavior and their environment.
A high resolution study of sediments, microfaunas (ostracods and foraminifers), and stable isotopes of ostracod shells from core PRD05, sampled from the Da’ao plain of the Pearl River Delta, provides new data about palaeoenvironmental changes during the Late Quaternary. The basal fluvial gravelly sediments of the core, representing the lowest deposits of the Quaternary at the core site, were possibly formed prior to the transgression associated with the last interglacial stage. This fluvial setting changed into a marginal marine setting during the last interglacial stage, any record of calcareous fossils were destroyed by subsequent dissolution during the last glacial phase, when the upper part of the deltaic sediments experienced subaerial oxidation, indicated by a mottled clay layer in the core. The postglacial sealevel rise in the South China Sea began at ~16,700 cal yr B. P. During the first phase of sea-level rise (from ~16,700 to 10,100 cal yr B. P.), a swamp environment developed at the core site. At ~10,100 cal yr B. P., marine waters intruded onto the Da’ao plain and reached the core site through the Modaomen channel. This timing was earlier than in other parts of the Pearl River Delta. Since then, a semi-enclosed estuarine environment developed and was maintained until ~5560 cal yr B. P. During this transgressive interval, short-term environmental fluctuations can be recognized based on microfauna and shell geochemical data. From ~10,100 to 8630 cal yr B. P., the sea-level rose, which was followed by a fall from ~8630 to 8520 cal yr B. P. An expanded transgression occurred between ~8520 and 7900 cal yr B. P. The time intervals from ~8520 to 8200 cal yr B. P. and from ~8080 to 7900 cal yr B. P. were marked by peak transgression. From ~7900 to 5560 cal yr B. P., the core site generally showed a reduced marine influence and enhanced freshwater input. A fluvial environment developed from ~5560 to 3100 cal yr B. P., and was succeeded by an alluvial plain setting.
Mineralized wood collected from Late Pliocene strata near Gorbki village in the Transcarpathian region of Beregovo Kholmogor’e in southwestern Ukraine was anatomically studied and identified. The wood possesses distinctive anatomical features and has distinct growth rings with an abrupt transition from early- to late-wood. Wood consists of tracheids with 1-3 seriate, dominating bi-seriate, opposite pits on the radial walls and taxodioid cross- field pitting, indentures present. Rays are uni-seriate and 1 to 73 cells high. Ray parenchyma horizontal walls thin and smooth. Axial parenchyma distributed in early- and late-wood and is solitary and diffuse, with end walls nearly smooth or slightly nodular. The combination of features observed in the wood indicates it belongs to the conifer family Taxodiaceae and is most similar to modern Sequoia and assigned to the fossil genus Sequoioxylon. Comparison with species of Sequoioxylon show it is most similar to Sequoioxylon burejense, but ray tracheids were not found in our specimens. We describe the specimens here as Sequoioxylon cf. s. burejense noting this similarity. Extant Sequoia is distributed in the northern California coastal forest eco-region of northern California and southern Oregon in the United States where they usually grow in a unique environment with heavy seasonal precipitation (2500 mm annually), cool coastal air and fog drip. This study supplies magafossil evidence of Sequoioxylon as an element of the Late Pliocene forest community in Ukraine and indicates a climate with heavy seasonal precipitation and fog drip.
Carbonate strata of the Mesoproterozoic Wumishan Formation in the Jixian area near Tianjin are ~3300 m thick and were deposited over some 100 million years (from ~1310±20 Ma to ~1207±10 Ma). Metre-scale cycles (parasequences) dominate the succession. They are generally of the peritidal carbonate type, and mostly show an approximately symmetrical lithofacies succession with thick stromatolite biostromes and small thromboliteoncolite bioherms constituting the central part and tidal-flat dolomites forming the upper and lower parts. Lagoonal-supratidal dolomitic shales with palaeosol caps make up the topmost layers. The boundaries of the Wumishan cycles are typically exposure surfaces, and there is abundant evidence for fresh-water diagenesis. Widespread 1:4 stacking patterns indicate that the individual Wumishan cycles are sixthorder parasequences, with 4 parasequences constituting one fifth-order parasequence set. Locally, 5-8 beds or couplets, can be discerned in some of the cycles. The regular vertical stacking pattern of beds within the sixth-order parasequences, forming the fifth-order parasequence sets, are interpreted as the result of environmental fluctuations controlled by Milankovitch rhythms, namely the superimposition of precession, and short and long-eccentricity. The widespread 1:4 stacking pattern in the cyclic succession, as well as the local 1:5-8 stacking patterns of the beds within the cycles, suggest that the Milankovitch rhythms had similar ratios in the Mesoproterozoic as in the Phanerozoic. Based on the cycle stacking patterns, 26 thirdorder sequences can be distinguished and these group into 6 second-order, transgressiveregressive megasequences (or sequence sets), all reflecting a composite, hierarchical succession of relative sea-level changes.
The Mesoproterozoic Wumishan Formation consists mainly of dolomites that represent diagenetically transformed limestones deposited in a shallow peritidal environment. Although the environment was tectonically stable, the study area in the Changping District (north of the Beijing area) was affected by synsedimentary earthquakes. Later, the dolomites in the study area were intruded by a granite. This resulted in contact metamorphism of the dolomites, changing them in a halo around the intrusion into marble. This marble, which is exposed near Taoyukou Village, shows some levels with well-developed stromatolites. The stromatolites contain structures that point at deformation when the stromatolites had not yet been lithified, and thus represent soft-sediment deformation structures. The stromatolites apparently built up during a time-span when repeated deformational processes affected the still unlithified sediment, from the sedimentary surface down to maximally a few decimeters. The deformed stromatolites thus represent seismites, which feature is exceptionally rarely recognizable in marble.
We analyzed the major and rare earth element compositions of siliceous deposits from the Upper Devonian Liujiang Formation, Lower Carboniferous Luzhai Formation, Lower-Middle Permian Sidazhai Formation and Tapi Formation, which are widely distributed as bedded cherts in the interplatform basinal successions of the Youjiang Basin. The Liujiang Formation and Luzhai Formation cherts generally have high Al/(Al+Fe+Mn) values (0.38-0.94) and are non-hydrothermal cherts. These cherts are generally characterized by moderately negative Ce anomalies and high Y/Ho values relatived to PAAS, indicating that the Youjiang Basin might have evolved into an open rift basin during the Late Devonian-Early Carboniferous. The Sidazhai Formation cherts from Ziyun generally have high Al/(Al+Fe+Mn) values (0.60-0.78), suggesting negligible contribution from a hydrothermal component. The Sidazhai Formation cherts from Hechi and the Tapi Formation cherts from Malipo generally have low Al/(Al+Fe+Mn) values (0.09-0.41), indicating an intense hydrothermal input. Relatived to the Sidazhai Formation cherts, the Tapi Formation cherts have higher Ce/Ce* values (0.68±0.19) and lower Y/Ho values (41.83±13.27), which may be affected by the terrigenous input from the Vietnam Block. The Sidazhai Formation cherts from Ziyun and Hechi exhibit negative Ce anomalies (0.43±0.12, 0.33±0.17, respectively) with high Y/Ho values (57.44±16.20, 46.02±4.27, respectively), resembling the geochemical characteristics of open-ocean basin cherts. These cherts were deposited on a passive continental margin adjacent to the Babu branch ocean, which may have contributed to upwelling. Detailed spatial studies on geochemical characteristics of the Late Paleozoic cherts can unravel the evolution of the Youjiang Basin.
Based on the data from 121 boreholes (9552 samples) and the distribution pattern analysis of foraminifera, ostracods, pollen, spores, wooly rhinoceros, elephants, water buffalo and beachrocks in time and space, three abrupt climate change events since the Late Pleistocene are recognized in the North China Plain. These climatic events caused three very warm periods and two severely cold periods. During the two warmest periods, the mean temperature was about 7℃ higher than at present, and during the two extreme cold periods, the mean temperature was some 6℃ lower than today. Moreover, the last warm period was in the Middle Holocene; its mean temperature was 3℃ higher than now in the region.