نتایج جستجو برای: nannofossil
تعداد نتایج: 231 فیلتر نتایج به سال:
Larger benthic foraminifera (LBF) are common and diverse throughout the Paleogene sediments of southern Tanzania, but have previously been little studied. A recent programme of onshore drilling known as the Tanzania Drilling Project has recovered large proportion of this succession for palaeoclimatic and palaeontological study. The sediment is largely a hemipelagic clay with secondary gravity s...
Abstraet The amount and type of organic matter present in an exceptionally complete upper Aptian to lower Cenomanian sequence of sediments from ODP site 763 on the Exmouth Plateau has been determined. Organic carbon concentrations average 0.2~o. Organic matter is marine in origin, and its production and preservation was low over the ca. 20-million-year interval recorded by this sequence. Becaus...
Adercotryma glomeratum is one of the most geographically and bathymetrically widespread species of Recent deep-sea benthic foraminifera, but the evolutionary history of this distinct agglutinated species is poorly known. In addition to one or two Recent species probably closely related to A. glomeratum, the Eocene-Oligocene species Adercotryma agterbergi has been described, but we suggest that ...
In this preliminary biometric study of the calcareous nannofossil species Chiasmolithus expansus, Chiasmolithus oamaruensis, and Chiasmolithus altus from the upper middle Eocene to lower Oligocene of Sites 647 and 748, we document a complete gradation of forms among all three species. Chiasmolithus oamaruensis has significantly higher morphologic variance than the other species. The Chiasmolith...
Planktic foraminifera are commonly used for first-order age control in deep-sea sediments from low-latitude regions based on a robust tropical–subtropical zonation scheme. Although multiple Neogene planktic foraminiferal biostratigraphic zonations mid-latitude exist, quantification of diachroneity the species as datums to test paleobiogeographic patterns origination and dispersal is lacking. He...
The upper Miocene to Pleistocene Shimajiri Group, composed mainly of siltstone and sandstone, occurs on some the Ryukyu Islands in southwestern Japan. This group is thought have been deposited a shelf-slope fore-arc basin setting before accumulation coral reef deposits (Ryukyu Group). We investigated calcareous nannofossil biostratigraphy Group Offshore Okinawa 1-x well, drilled near northeaste...
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