Reply to ‘Discussion of “Magnetostratigraphic confirmation of a much faster tempo for sea-level change for the Middle Triassic Latemar platform carbonates” by D. V. Kent, G. Muttoni and P. Brack [Earth Planet. Sci. Lett. 228 (2004), 369-377]’ by L. Hinnov

Middle Triassic radiolarian bedded cherts in the Mino Belt, central Japan, include a sequence showing an abrupt facies change from the lower to the upper, where grey–black bedded cherts enriched in carbonaceous matter and framboidal pyrite are overlain by brick-red hematitic bedded cherts. Brownish-yellow chert enriched in goethite and purple-red chert occur at the boundary between the grey–black bedded cherts and the brick-red bedded cherts. This facies change is in accordance with stratigraphic variations of geochemical characteristics; the lower section grey–black bedded cherts, compared with the upper section brick-red bedded cherts, are enriched in Ctot and Stot, and are characterized by lower MnO/TiO2, higher FeO/Fe2O3* (total iron as Fe2O3) and more variable Fe2O3*/TiO2 values. Some of the lower section samples, in addition, are characterized by an enrichment in some transition metals (Ni, Cu, and Zn). The covariation of mineralogical and geochemical characteristics indicates that sedimentary environments and diagenetic processes were different between the lower and the upper section bedded cherts. During the deposition of the lower section bedded cherts, the sedimentary environment was anoxic and bacterial sulphate reduction occurred during the early diagenetic stage. In contrast, the upper section bedded cherts were subjected to less reducing diagenetic processes; active sulphate reduction did not occur. The change of sedimentary environment and diagenetic process at the site of deposition is likely to be attributed to the fluctuated concentration of dissolved oxygen in the water mass of a semi-closed marginal ocean basin, which was potentially caused by sea-level change that occurred during Middle Triassic time.

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Significant continental ice volumes on mid-Paleocene Antarctica? Latitudinal temperature gradients, sea level change and the carbon cycle

Rendiconti online della Società Geologica Italiana ◽

10.3301/rol.2014.30 ◽

2014 ◽

Vol 31 ◽

pp. 31-32

Author(s):

Peter Bijl

Keyword(s):

Carbon Cycle ◽

Sea Level ◽

Sea Level Change ◽

Temperature Gradients ◽

Level Change

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Phanerozoic Oxygen

10.23943/princeton/9780691145020.003.0011 ◽

2017 ◽

Author(s):

Donald Eugene Canfield

Keyword(s):

Oxygen Consumption ◽

Organic Carbon ◽

Sea Level ◽

Time Scale ◽

Atmospheric Oxygen ◽

Sea Level Change ◽

Oxygen Production ◽

Level Change ◽

History Of ◽

Geologic Processes

This chapter discusses the modeling of the history of atmospheric oxygen. The most recently deposited sediments will also be the most prone to weathering through processes like sea-level change or uplift of the land. Thus, through rapid recycling, high rates of oxygen production through the burial of organic-rich sediments will quickly lead to high rates of oxygen consumption through the exposure of these organic-rich sediments to weathering. From a modeling perspective, rapid recycling helps to dampen oxygen changes. This is important because the fluxes of oxygen through the atmosphere during organic carbon and pyrite burial, and by weathering, are huge compared to the relatively small amounts of oxygen in the atmosphere. Thus, all of the oxygen in the present atmosphere is cycled through geologic processes of oxygen liberation (organic carbon and pyrite burial) and consumption (weathering) on a time scale of about 2 to 3 million years.

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