Controls and feedback functions for Late Proterozoic environments: Erosion as a master variable

Conference · Wed Jan 01 04:00:00 EST 1992 · Geological Society of America, Abstracts with Programs; (United States)

OSTI ID:5880150

Derry, L A ^[1]

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1. CRPG-CNRS, Vandoeuvre (France)

The carbon isotopic record of the Late Proterozoic shows large and rapid variations, which have been interpreted to reflect changes in carbon cycling and organic carbon burial rates. The Sr isotopic record also shows large variations, which reflect changes in submarine hydrothermal activity and global erosion rates. These variations in turn imply the possibility of important environmental changes during the Late Riphean and Vendian. Consideration of both the cycles of oxygen and phosphorus can help clarify both the causes and consequences of changes in the behavior of the carbon cycle. The prolonged period (ca. 200 Ma) of positive [delta][sup 13]C in Riphean marine carbonates cannot represent an era of high productivity and rapid Corg burial, because of the negative feedback cycle of P. Rather, enhanced preservation of organic matter due to marine anoxia must have been responsible. The formation of Fe hydroxy-phosphates species also limited P availability. A much briefer episode of high [delta][sup 13]C in post-Varanger sediments is associated with increased erosion rates during the Pan-African collision, and represents a period of rapid Corg burial. This excursion can be driven by increased productivity because of increased P cycling during the period of high erosion. It was also aided by rapid sedimentation rates in continental margin sequences. However, this increase was eventually limited by diminishing erosion rates and availability of P. The oxygen flux from the carbon system was easily sufficient to rapidly increase atmospheric P[sub O2]. Increased erosion is thus both a forcing function and a feedback function for the atmospheric oxygen reservoir.

• OSTI ID: 5880150
• Report Number(s): CONF-921058--
• Conference Information: Journal Name: Geological Society of America, Abstracts with Programs; (United States) Journal Volume: 24:7
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580000* -- Geosciences
CARBON CYCLE
CARBONATE ROCKS
DEPOSITION
ELEMENTS
EROSION
GEOLOGIC AGES
ISOTOPE RATIO
MATTER
NONMETALS
ORGANIC MATTER
OXYGEN
PARTIAL PRESSURE
PHOSPHORUS
PRECAMBRIAN ERA
ROCKS
SEDIMENTARY ROCKS