16. Late Neogene Paleoceanography in the Western North Pacific
نویسنده
چکیده
Late Neogene paleoceanographic history in the western North Pacific is discussed on the basis of: (1) Td (diatom temperature) values, (2) species composition, and (3) the structure of diatom assemblages at Sites 579 and 580. These factors provide a record of fluctuations of the past position of the subarctic-subtropic front because these sites lie within the transition zone between the modern day subarctic and central water masses. Changes in species composition during the past 4.0 m.y. are recognized. Major paleoclimatic events are discussed on the basis of Td values. Distinct, large drops in surface water temperature, estimated on the basis of Td values, occurred 2.5, 2.0, and 1.6 m.y. ago. Large fluctuations of surface water temperature are recognized throughout the recovered sediments. The preglacial/glacial boundary occurs 2.50-2.85 m.y. ago at 40°N in the western North Pacific.
منابع مشابه
Distribution and geochemical variations among paleogene volcanic rocks from the north-central Lut block, eastern Iran
The Lut block in eastern Iran is a micro-continental block within the convergent orogen between the Arabian, Eurasian and Indian plates. Large areas of the north-central, eastern, and western Lut block are covered by volcanic rocks of Paleogene, Neogene and Quaternary age. Peak volcanic activity took place in the north-central part of the Lut block during the Eocene, and then dramatically decr...
متن کاملOn some Vetigastropoda (Mollusca, Gastropoda) from the Plio-Pleistocene of the Philippines with descriptions of three new species.
We studied representatives of seven vetigastropod families in an extremely well-preserved Plio-Pleistocene mollusc fauna found in relatively deep water sediments (c. 200-300 m paleodepth) from the north-western Philippines. The fauna is systematically described and its paleoenvironmental and paleobiogeographical character is explored. Twenty-six species of gastropods were studied, three of whic...
متن کاملPhylogenetic relationships within the aquatic snail genus Tryonia: implications for biogeography of the North American Southwest.
We examined the phylogenetic relationships among 23 species of the North American aquatic snail genus Tryonia (Hydrobiidae), 10 additional representatives of the subfamily Cochliopinae, and two outgroups. Maximum parsimony analysis of a 601-base-pair sequence from the mitochondrial COI gene did not support monophyly of the genus nor its subgenus Paupertryonia. A clade composed of the type speci...
متن کاملCovariability of western tropical Pacific-North Pacific atmospheric circulation during summer
North Pacific subtropical high (NPSH) is permanent high-pressure system over the Northern Pacific Ocean and it extends to the western North Pacific during the boreal summer (June-July-August), which is so called the western North Pacific subtropical high (WNPSH). Here, we examine the covariability of the NPSH-WNPSH during summer using both observation and Coupled Model Intercomparison Project p...
متن کاملFirst mammal fossil locality from the late Miocene of Zagros, western Iran
A new and the first mammal fossil locality from the Zagros Basin of Iran is reported here. The fossil locality, known as Dimeh, is located in the Lorestan province, west of Iran. The fauna includes abundant bovid cranial remains, mostly representing boselaphines and palaeoryxoids, as well as gazelles and spiral horned antelopes. Hipparionine horses similar to Hippotherium group are also represe...
متن کامل