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

Four sites were drilled on the Bellingshausen Abyssal Plain and continental rise off Antarctica during Leg 35 of the Deep Sea Drilling Project. Site 322 penetrated 513 meters of lower Miocene (? Oligocene) to Holocene diatomaceous claystone, siltstone, and sandstone overlying basalt. A similar Neogene section at Site 323 caps 63 meters of upper Maestrichtian to (?) Oligocene brown nanno claystone and Fe-claystone bottoming on basalt. Site 324 penetrated 218 meters of Pliocene-Pleistocene terrigenous clay with interbedded silt layers interpreted as contourites, and 718 meters of lower Miocene-Holocene diatomaceous claystone grading downward into coarse sandstone were drilled at Site 325. The brown Fe-claystone at Site 323 and a similar, thin basal unit at Site 322 indicate pelagic deposition, largely from volcanogenic sources at rates <0.5 cm/1000 yr, from the late Maestrichtian to the (?) Oligocene. Abundant nannoplankton in lower Paleocene claystone suggest depression of the CCD at this time, in contrast to a shallow CCD in most other areas of the world's oceans. Significant bottom-current activity was not initiated until the latest Oligocene or early Miocene, probably in response to formation of deep gaps in the Drake Passage area. An apparent 35-40 m.y. hiatus in sedimentation (middle Paleocene-Oligocene) at Site 323 may represent erosion by Miocene bottom currents. The subsequent sedimentary record is dominated by turbidites derived from Antarctica and exhibits frequent reworking by bottom currents at Sites 322, 323, and 325. Silt and clay contourites, deposited from contour currents flowing west along the continental rise, are found at Site 324. The earliest firm evidence for Antarctic glaciation encountered on Leg 35 is ice-rafted debris in lower middle Miocene sediment at Site 325. Comparison of our drilling results with those of Legs 28 and 29 shows a clear latitudinal control on the earliest occurrence of ice rafting: late Oligocene to early Miocene at 65°-70°S ranging to late Miocene to Pliocene at 55°-60°S. The earliest ice-rafting is preceded in all cases by deposition of diatomaceous sediment which is taken to indicate the northward migration of the polar front zone. Analysis of sedimentary textures, composition, and rates of accumulation in Leg 35 cores suggests increasing glaciation of West Antarctica through the Miocene, culminating in a glacial maximum with grounded shelf ice near the Miocene-Pliocene boundary. The timing of Pliocene-Pleistocene fluctuations in the glaciation of West Antarctica is not clearly defined in Leg 35 cores, but the ice sheet probably again reached extensive, but ungrounded, shelf-ice conditions several times during this period. 'Lamont-Doherty Geological Observatory of Columbia University, Palisades, N.Y. Woods Hole Oceanographic Institution, Woods Hole, Massachusetts. Sonoma State College, Rohnert Park, California. Florida State University, Tallahassee, Florida.

Continental Rise and Abyssal Plain Sedimentation in the Southeast Pacific BasinLeg 35 Deep Sea Drilling Project

Continental Rise and Abyssal Plain Sedimentation in the Southeast Pacific BasinLeg 35 Deep Sea Drilling Project