4 results for late quaternary sediment core
Contributors: Yasuhara, Moriaki, Okahashi, Hisayo
Late Quaternary deep-sea ostracode taxonomy of the eastern North Atlantic...sediment core enabled us to provide a robust taxonomic baseline of the...late Quaternary sediments from Ocean Drilling Program (ODP) Hole 982A,...Late Quaternary deep-sea ostracod taxonomy of the eastern North Atlantic...late Quaternary sediments from Ocean Drilling Program (ODP) Hole 982A,...Late Quaternary deep-sea ostracod taxonomy of the eastern North Atlantic ... Taxonomic revision and re-evaluation of the eastern North Atlantic deep-sea ostracodes are conducted based on late Quaternary sediments from Ocean Drilling Program (ODP) Hole 982A, Rockall Plateau, eastern North Atlantic. Twenty one genera and 51 species were examined and (re-)illustrated with high-resolution scanning electron microscopy images. Six new species are described: Polycope lunaris, Argilloecia labri, Bythoceratina nuda, Cytheropteron colesoabyssorum, Cytheropteron colesopunctatum, and Cytheropteron paramediotumidum. Excellent fossil ostracode preservation in this sediment core enabled us to provide a robust taxonomic baseline of the eastern North Atlantic deep-sea ostracodes for application to palaeoceanographical, palaeoecological, and biogeographical studies.
Data from: Regional-scale spatial heterogeneity in the Late Paleocene paratropical forests of the U.S. Gulf Coast
Contributors: Jardine, Phillip E., Harrington, Guy J., Stidham, Thomas A.
cores to compare spatial patterns in the Late Paleocene GCP to modern ...Late Paleocene paratropical forests of the U.S. Gulf Coast...Late Paleocene GCP with any particular modern biome. Our results demonstrate... sediment cores. The file was created in MS Excel 2008....sediment cores. The file was created in MS Excel 2008....Late Paleocene Calvert Bluff and Tuscahoma formations of the formerly ...cores used. Supplement Figure 2 shows the locations of the core sites ...lake cores used. Supplement Figure 2 shows the locations of the core sites ... The study of spatial patterns in biotic compositional variability in deep time is key to understanding the macroecological response of species assemblages to global change. Globally warm climatic phases are marked by the expansion of megathermal climates into currently extra-tropical areas. However, there is currently little information on whether vegetation in these ‘paratropical’ regions resembled spatially modern tropical or extra-tropical biomes. In this paper we explore spatial heterogeneity in extra-tropical megathermal vegetation, using sporomorph (pollen and spore) data from the Late Paleocene Calvert Bluff and Tuscahoma formations of the formerly paratropical US Gulf Coast (Texas, Mississippi and Alabama). The dataset comprises 139 sporomorph taxa recorded from 56 samples. Additive diversity partitioning, non-metric multidimensional scaling, and cluster analysis show compositional heterogeneity both spatially and lithologically within the US Gulf Coastal Plain (GCP) microflora. We then use sporomorph data from Holocene lake cores to compare spatial patterns in the Late Paleocene GCP to modern tropical and extra-tropical biomes. Distance decay analysis of the Holocene data reveals a higher rate of spatial turnover in tropical versus extra-tropical vegetation types, consistent with a latitudinal gradient in floral compositional heterogeneity. The specific combination of rate and scale dependency of distance decay in the Holocene assemblages prevented us from associating the Late Paleocene GCP with any particular modern biome. Our results demonstrate the importance of spatial scale, taphonomy and lithology in determining patterns of spatial heterogeneity, and show the potential of the fossil sporomorph record for studying spatial patterns and processes in deep time.
Contributors: Yasuhara, Moriaki, Hunt, Gene, Cronin, Thomas M., Hokanishi, Natsumi, Kawahata, Hodaka, Tsujimoto, Akira, Ishitake, Miho
Core Research...Quaternary climate changes underscores the interaction between the physical...Quaternary climate changes underscores the importance of the interaction...Quaternary deep-sea benthic communities in the North Pacific Ocean ... There is a growing evidence that changes in deep-sea benthic ecosystems are modulated by climate changes, but most evidence to date comes from the North Atlantic Ocean. Here we analyze new ostracod and published foraminiferal records for the last 250,000 years on Shatsky Rise in the North Pacific Ocean. Using linear models, we evaluate statistically the ability of environmental drivers (temperature, productivity, and seasonality of productivity) to predict changes in faunal diversity, abundance and composition. These microfossil data show glacial-interglacial shifts in overall abundances and species diversities that are low during glacial intervals and high during interglacials. These patterns replicate those previously documented in the North Atlantic Ocean, suggesting that the climatic forcing of the deep-sea ecosystem is widespread, and possibly global in nature. However, these results also reveal differences with prior studies that probably reflect the isolated nature of Shatsky Rise as a remote oceanic plateau. Ostracod assemblages on Shatsky Rise are highly endemic but of low diversity, consistent with the limited dispersal potential of these animals. Benthic foraminifera, by contrast, have much greater dispersal ability and their assemblages at Shatsky Rise show diversities typical for deep-sea faunas in other regions. Statistical analyses also reveal ostracod–foraminferal differences in relationships between environmental drivers and biotic change. Rarefied diversity is best explained as a hump-shaped function of surface productivity in ostracods, but as having a weak and positive relationship with temperature in foraminifera. Abundance shows a positive relationship with both productivity and seasonality of productivity in foraminifera, and a hump-shaped relationship in ostracods. Finally, species composition in ostracods is influenced by both temperature and productivity, but only a temperature effect is evident in foraminifera. Though complex in detail, the global-scale link between deep-sea ecosystems and Quaternary climate changes underscores the interaction between the physical and biological components of paleoceanographical research to better understand the history of the biosphere.
Contributors: Woodward, Craig A., Shulmeister, James, Larsen, Joshua, Jacobsen, Geraldine E., Zawadzki, Atun
sedimentation rate, eutrophication or change in hydrology. ... Increased catchment erosion and nutrient loading are commonly recognized impacts of deforestation on global wetlands. In contrast, an increase in water availability in deforested catchments is well known in modern studies but is rarely considered when evaluating past human impacts. We used a Budyko water balance approach, a meta-analysis of global wetland response to deforestation, and paleoecological studies from Australasia to explore this issue. After complete deforestation, we demonstrated that water available to wetlands increases by up to 15% of annual precipitation. This can convert ephemeral swamps to permanent lakes or even create new wetlands. This effect is globally significant, with 9 to 12% of wetlands affected, including 20 to 40% of Ramsar wetlands, but is widely unrecognized because human impact studies rarely test for it.