NASA Logo

NTRS

NTRS - NASA Technical Reports Server

Back to Results
Terminal Proterozoic reorganization of biogeochemical cyclesThe Proterozoic aeon (2,500-540 million years ago) saw episodic increases in atmospheric oxygen content, the evolution of multicellular life and, at its close, an enormous radiation of animal diversity. These profound biological and environmental changes must have been linked, but the underlying mechanisms have been obscure. Here we show that hydrocarbons extracted from Proterozoic sediments in several locations worldwide are derived mainly from bacteria or other heterotrophs rather than from photosynthetic organisms. Biodegradation of algal products in sedimenting matter was therefore unusually complete, indicating that organic material was extensively reworked as it sank slowly through the water column. We propose that a significant proportion of this reworking will have been mediated by sulphate-reducing bacteria, forming sulphide. The production of sulphide and consumption of oxygen near the ocean surface will have inhibited transport of O2 to the deep ocean. We find that preservation of algal-lipid skeletons improves at the beginning of the Cambrian, reflecting the increase in transport by rapidly sinking faecal pellets. We suggest that this rapid removal of organic matter will have increased oxygenation of surface waters, leading to a descent of the O2-sulphide interface to the sea floor and to marked changes in the marine environment, ultimately contributing to the Cambrian radiation.
Document ID
20040112224
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Logan, G. A.
(Indiana University Bloomington 47405-1403, United States)
Hayes, J. M.
Hieshima, G. B.
Summons, R. E.
Date Acquired
August 21, 2013
Publication Date
July 6, 1995
Publication Information
Publication: Nature
Volume: 376
Issue: 6535
ISSN: 0028-0836
Subject Category
Geosciences (General)
Distribution Limits
Public
Copyright
Other
Keywords
Non-NASA Center
NASA Discipline Exobiology
NASA Discipline Number 52-30
NASA Program Exobiology

Available Downloads

There are no available downloads for this record.
No Preview Available