نتایج جستجو برای: microfossil
تعداد نتایج: 309 فیلتر نتایج به سال:
Climate-driven Oxygen Minimum Zone (OMZ) expansions in the geologic record provide an opportunity to characterize the spatial and temporal scales of OMZ change. Here we investigate OMZ expansion through the global-scale warming event of the most recent deglaciation (18-11 ka), an event with clear relevance to understanding modern anthropogenic climate change. Deglacial marine sediment records w...
Many questions in evolutionary biology require an estimate of divergence times but, for groups with a sparse fossil record, such estimates rely heavily on molecular dating methods. The accuracy of these methods depends on both an adequate underlying model and the appropriate implementation of fossil evidence as calibration points. We explore the effect of these in Poaceae (grasses), a diverse p...
New analytical approaches and discoveries are demanding fresh thinking about the early fossil record. The 1.88-Ga Gunflint chert provides an important benchmark for the analysis of early fossil preservation. High-resolution analysis of Gunflintia shows that microtaphonomy can help to resolve long-standing paleobiological questions. Novel 3D nanoscale reconstructions of the most ancient complex ...
A new chroococcalean cyanobacterium is described from approximately 1-billion-year-old non-marine deposits of the Torridonian Group of Scotland and the Nonesuch Formation of Michigan, USA. Individual cells of the new microfossil, Eohalothece lacustrina gen. et sp. nov., are associated with benthic microbial biofilms, but the majority of samples are recovered in palynological preparations in the...
The timing of continental-scale marine flooding events in Western Amazonia during the Neogene is still an unsolved question. Despite broad proxy-based evidence such events, pathways and duration late Miocene incursions remain controversial. We provide coupled calcareous organic microfossil geochemical data from six onshore cores sequences Solimões Basin, Brazil. Our records support minor influe...
In the previous paper, geological ages of Late Cretaceous, Paleocene, late Middle to Eocene, Oligocene and early Early Miocene were confirmed at first time, based on occurrences both age diagnostic larger foraminifera associated planktonic foraminifera, from Sashida Limestone included basalt pebbles, Sashida, Kamo-Gun, south Izu Peninsula. Therefore, was made up clastic carbonate rocks various ...
The present contribution provides a study of calcareous nannofossils and siliceous microfossils from the Sawai Bay Formation on Car Nicobar Island, northern Indian Ocean. Two stratigraphically short sediment intervals near have been examined. Qualitative quantitative microfossil analyses show ‘A’ Section to be devoid microfossils, while 24 well-preserved nannofossil taxa are identified. ‘B’ yie...
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