Page 99 - BE Book PESD 2021 22

PESD_GSU_20200714_0552_(completed): Oxygenation of the Proterozoic
ocean

PESD_GSU_20200714_0552_(completed)
1. Title of the Project:

Oxygenation of the Proterozoic ocean
2. Name of Proposing Scientists:
Amlan Banerjee
3. Brief objectives and justification:

To model time dependent oxygenation of the ocean water as a function of temperature and
oxygen fugacity of the atmosphere and field verification using various geochemical proxies
of the carbonate and clastic (shale) rocks from the Proterozoic Purana basins. To understand
the early oxygenation history of the atmosphere and ocean during Proterozoic time, numerical
models supported by geochemical proxies (examples, iron, molybdenium, calcium,
chromium; carbon, oxygen, and sulphur isotope data, trace element abundances and
biomarkers) of the carbonate rock samples collected from the Proterozoic basins of India.
4. Name of Others Scientists Associated with their affiliation:

4.1. From the Institute:
From the Institute: Prof. Sarbani Patranabis Deb and Prof. Dilip Saha.
4.2. From other Institutions:

From other Institutions: Dr. Mirosław Słowakiewicz, is an adjunct professor based in the
Institute of Geological Sciences, Polish Academy of Sciences.

5. Date of Commencement:
01/04/2017
6. Date of Completion:

31/03/2020
7. Completion report(max 500 words) including complete list of publications and
patents based on the work from the project:
Time dependent numerical models of oxygenation of the ocean water as a function of
temperature and oxygen fugacity are being developed with a oxygen sink term. Preliminary
results suggest that oxygen diffusion (i) is a slow process, but (ii) travels fast in advective
mixing of the ocean water, (iii) dependent on the initial distribution of available oxygen in
ocean water and (iv) rate of oxygen diffusion decreases with increase in water temperature.
Numerical calculations suggest that the temperature of modern ocean water generally
decreases with greater depth whereas density and dissolved oxygen increase and
consequently, as a result of the positive density profile, modern ocean circulation behaves as
a forced convective system. In contrast to this scenario, we propose that at times during the
Precambrian (Archean and Proterozoic) inverted profiles could have developed in which, with
depth, ocean water temperature increased and density and dissolved oxygen decreased. This
positive temperature profile along with the negative density distribution pattern resulted in
palaeo-ocean circulation behaving as a free convective system. It is proposed that this free
convection, which may have been stable, or chaotic and subject to secondary instabilities,
hindered the oxygenation of the palaeo-ocean. It may not be coincidental that the Great
Oxygenation Event (GOE) and Huronian glaciations are synchronous, similar to those of the

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