English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

Sediments containing foraminifers were penetrated at all three sites drilled during DSDP Leg 56 as the first part of a Japan Trench transect. Two sites were on the inner wall of the trench (Site 435, 3401 m; Site 434, 5986 m), and one was on the oceanic plate east of the trench (Site 436, 5240 m). Because the lysocline in this area is at about 2000 meters and the calcite-compensation depth is at about 3500 meters, calcareous foraminifers are generally not abundant in the sediments; however, the biostratigraphy based upon planktonic foraminifer faunas agrees with that based predominantly upon siliceous microfossils from the sites. Hole 435A yielded the oldest of the planktonic foraminifers from the three sites. Two plankonic foraminifer lineages were particularly important in determining the biostratigraphy of the sites. The Neogloboquadrina asanoi-kagaensis-himiensis-eggeri lineage underwent rapid evolution around the Pliocene-Pleistocene boundary and is widely recognized in the oil-producing region of northern Japan and in the northwest Pacific. Second, the Globorotalia orientalis-inflata praeinflata-inflata inflata lineage evolved during the Pliocene; tests of these species are very resistant to dissolution. During the Pleistocene, individuals of Neogloboquadrina pachyderma preferentially coiled sinistrally in the cold waters north of the subarctic boundary and dextrally in temperate waters south of it. The ratio of these two forms was used to identify relative motions of near-surface waters of the Kuroshio and Oyashio Currents in the transect area in response to Quaternary climatic fluctuations. Benthic foraminifers characteristic of modern surface sediments were used to interpret uplift and plate motions of the Japan Trench as recorded at Leg 56 sites. Materials from the DSDP sites and from piston cores taken elsewhere in the region permitted extension of the foraminifer bathymetry of Matoba (1977) to the bottom of the Japan Trench; the lower bathyal, abyssal, and hadal biofacies are recognized. The sediments of the oceanic plate have a benthic foraminifer fauna distincly different from that of the inner trench wall at comparable depths. There is no evidence from these contrasting faunas to indicate that sediments of the oceanic plate are added to the landward trench wall during subduction. Manganese micronodules recovered from pelagic clay at Site 436 contained external models of Paleogene(?) juvenile planktonic foraminifers. That the tests of these foraminifers did not dissolve before the manganese was deposited is significant to theories of manganesenodule formation. Two new foraminifer species, Globorotalia wilesi and Silicosigmoilina splendida, are named. INTRODUCTION trench slope (Sites 438 and 439). We suspected that, in accord with observations at other trenches, sediments of The DSDP transect across the Japan Trench (Legs 56 the oceanic plate were being scraped off during subducand 57) was designed to sample representative sections tion, forming an accretionary wedge at the foot of the of contrasting elements of this tectonically active marlandward wall. Foraminifer studies were intended to gin, including the oceanic plate (Sites 436 and 437), the provide (1) planktonic foraminifer ages to determine acbase of the landward trench wall (Sites 434 and 441), cumulation rates and to identify stratigraphic gaps the mid-slope terrace (Sites 435 and 440), and the inner within the sections, and (2) benthic foraminifer data

Foraminifers from Deep Sea Drilling Project Sites 434, 435, and 436, Japan Trench