Biofacies evidence for Late Cambrian low-paleolatitude oceans, western United State and central Asia

Conference · Thu Jan 31 23:00:00 EST 1991 · AAPG Bulletin (American Association of Petroleum Geologists); (United States)

OSTI ID:5210859

Taylor, M E ^[1]; Cook, H E ^[2]; Melnikova, L ^[3]

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1. Geological Survey, Denver, CO (United States)
2. Geological Survey, Menlo Park, CA (United States)
3. Palaeontological Inst., Moscow (Russian Federation)

Biofacies that formed on carbonate platform-margin slopes adjacent to an early Paleozoic, low-paleolatitude paleoocean are contained in the Upper Cambrian Swarbrick Formation, Tyby Shale, and Upper Cambrian-lowest Ordovician Hales Limestone of the Hot Creek Range, Nevada, and the Upper Cambrian-lowest Ordovician part of the Shabakty Suite of the Malyi Karatau, southern Kazakhstan. These in-situ limestones formed in platform-margin slope and basin-plain environments. Shoal-water faunal assemblages occur in carbonate-turbidite and debris-flow deposits interbedded with in-situ deeper water assemblages of the submarine-fan facies. Abundant sponge spicules, geographically widespread benthic trilobites, and rare ostracodes occur in some of the in-situ beds. In contrast, the shoal-water platform environments were well oxygenated and contain mainly endemic trilobite assemblages. These biofacies characteristics support an interpretation that Late Cambrian oceans were poorly oxygenated, but not anoxic, below the surface mixing layer and that benthic trilobite faunas were widely distributed in response to the more-or-less continuous deep water, low-oxygen habitats. Elements of the Late Cambrian low-oxygen biofacies are widespread in the Tien Shan structural belt of China and the Soviet Union, in central and eastern China, and along the western margin of early Paleozoic North America. This facies distribution pattern defines the transition from low-paleolatitude, shoal-water carbonate platforms to open oceans which have since been destroyed by pre-Late Ordovician and pre-middle Paleozoic Paleotectonic activity.

• OSTI ID: 5210859
• Report Number(s): CONF-9103128--
• Journal Information: AAPG Bulletin (American Association of Petroleum Geologists); (United States), Journal Name: AAPG Bulletin (American Association of Petroleum Geologists); (United States) Vol. 75:2; ISSN AABUD; ISSN 0149-1423
• Country of Publication: United States
• Language: English

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58 GEOSCIENCES
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DEVELOPED COUNTRIES
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FEDERAL REGION IX
GEOLOGIC AGES
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