Could the Late Permian deep ocean have been anoxic
نویسندگان
چکیده
Models ofocean circulation and biogeochemical cy les are used to speculate bout possible m chanisms of deep-sea anoxia across the Pertoo-Triassic boundary. Two modes of likely Late Permian ocean thermohaline circulation are identified: a vigorous "therm',d mode" driven by cooling in southern polar latitudes and aweaker "haline mode" driven by evaporation fromthe subtropics. We find that the thermal mode, typical of climates such as our own, is unlikely to surpport deep-sea anoxia. The haline mode, which might exist in warm climates with enhanced hy rological cycles, can lead to significant but periodic epletion of oxygen in the Panthalassic deep o ean. However, owing tothe inherent instability of the haline mode, a deep-sea •oxia persisting for millions of ye,•u s is not clearly supported by this tudy, though mechanisms emerge which might be consistent with the observed record. The nhanced hy rological cycle (or educed oceanic d apycnal mixing) required toobtain the haline mode r main unconstrah•:d for the Late Permian.
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Association of S-depleted pyrite layers with negative carbonate dC excursions at the Permian-Triassic boundary: Evidence for upwelling of sulfidic deep-ocean water masses
[1] A marine Permian-Triassic boundary (PTB) section at Nhi Tao, Vietnam, contains a series of at least 9 pyritic horizons characterized by concurrent decreases in pyrite S(dSpy) and carbonate C-isotopic compositions (dCcarb). The first and largest of the events that precipitated these pyritic horizons was coincident with the Late Permian mass extinction, while subsequent events were generally ...
متن کاملReply to Comment by Roberta M. Hotinski, Lee R. Kump, and Karen L. Bice on ‘‘Could the Late Permian deep ocean have been anoxic?’’
[1] Two recent studies [Hotinski et al., 2001; Zhang et al., 2001] have modeled and discussed Late Permian ocean circulation and oxygenation. These studies have reached significantly different conclusions. Zhang et al. [2001] find that a ‘‘thermal mode’’ ocean circulation driven by cooling in polar latitudes is unlikely to support deep-sea anoxia, but a ‘‘haline mode’’ ocean circulation, a shal...
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