Sizing up the sub-Tommotian unconformity in Siberia
1995; Geological Society of America; Volume: 23; Issue: 12 Linguagem: Inglês
10.1130/0091-7613(1995)023 2.3.co;2
ISSN1943-2682
AutoresAndrew H. Knoll, Alan J. Kaufman, М. А. Семихатов, J. P. Grotzinger, William A. Adams,
Tópico(s)Geological and Geophysical Studies
ResumoSedimentary rocks in the western Anabar region, northwestern Siberia, preserve an exceptional record of evolution and biogeochemical events near the Proterozoic-Cambrian boundary. Carbon isotopic data on petrographically and geochemically screened samples collected at 1 to 2 m intervals support correlation of the lower Anabar succession (Staraya Reckha and lower Manykai Formations) with sub-Tommotian carbonates of the Ust'-Yu-doma Formation in southeastern Siberia. In contrast, the upper Manykai and most of the overlying Medvezhya Formation appear to preserve a sedimentary and paleontological record of an evolutionary important time interval represented in southeastern Siberia only by the sub-Tommotian unconformity. Correlation of the Anabar section with other northern Siberian successions that contain well-dated volcanic rocks permits the estimate that the sub-Tommotian unconformity in southeastern Siberia spans approximately 3 to 6 m.y. Diverse small shelly fossils (but not archaeocyathans) previously thought to mark the base of the Tommotian Stage evolved sequentially throughout this earlier interval.
Referência(s)