Geochemical evidence for a catastrophic biotic event at the Frasnian/Famennian boundary in south China

Journal Article · Thu Aug 01 00:00:00 EDT 1991 · Geology; (United States)

DOI:https://doi.org/10.1130/0091-7613(1991)019<0776:GEFACB>2.3.CO;2· OSTI ID:5996303

Wang, Kun; Chatterton, B D.E. ^[1]; Orth, C J; Attrep, M Jr ^[2]; Hou, Hongfei ^[3]; Geldsetzer, H H.J. ^[4]

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1. Univ. of Alberta, Edmonton (Canada)
2. Los Alamos National Lab., NM (United States)
3. Chinese Academy of Geological Sciences, Beijing (China)
4. Geological Survey of Canada, Alberta (United States)

A strong {delta}{sup 13}C anomaly coincides with a weak Ir anomaly at the Frasnian/Famennian (F/F) boundary exposed at Xiangtian, Guangxi, south China. The maximum whole-rock Ir abundance is 0.23 ppb (0.35 ppb on a carbonate-free basis) compared with averages of 0.016 and 0.044 ppb above and below the boundary interval. The {delta}{sup 13}C in carbonate abruptly shifts from a late Frasnian level of about +1{per thousand} to {minus}2.49 {per thousand}in the boundary interval and then abruptly returns to pre-boundary levels, suggesting a temporary reduction of surface-water biomass. A widely distributed (over at least several hundred kilometers) limestone breccia unit of possible wave-deposit origin is present directly below the boundary in south China. Enrichments of Al, V, Cr, As, and U, and a dip in the Mn abundance in the boundary interval indicate that reducing conditions might have been associated with the element enrichment. However, an alternative hypothesis is that oceanic impact(s) at the F/F boundary near south China provided the excess Ir and caused the biotic crisis and the formation of breccia deposits observed in the Late Devonian South China Sea.

• OSTI ID: 5996303
• Journal Information: Geology; (United States), Vol. 19:8; ISSN 0091-7613
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
CHINA
GEOLOGIC FORMATIONS
GEOCHEMISTRY
GEOLOGIC HISTORY
ALUMINIUM
ARSENIC
BOUNDARY CONDITIONS
CARBON 13
CARBONATE ROCKS
CHINA SEA
CHROMIUM
DEVONIAN PERIOD
DISASTERS
ECOLOGICAL CONCENTRATION
GEOLOGIC MODELS
IRIDIUM
ISOTOPE RATIO
LIMESTONE
MANGANESE
URANIUM
VANADIUM
ACTINIDES
ASIA
CARBON ISOTOPES
CHEMISTRY
ELEMENTS
EVEN-ODD NUCLEI
GEOLOGIC AGES
ISOTOPES
LIGHT NUCLEI
METALS
NUCLEI
PACIFIC OCEAN
PALEOZOIC ERA
PLATINUM METALS
ROCKS
SEAS
SEDIMENTARY ROCKS
SEMIMETALS
STABLE ISOTOPES
SURFACE WATERS
TRANSITION ELEMENTS
580000* - Geosciences