Phanerozoic patterns and controls of carbonate sedimentation.

Modern shallow water marine carbonate accumulation rate is about 3.0 m/kyr within 30$\sp\circ$ of the equator, and declines exponentially as a function of surface water temperature and saturation state to less than 0.1 m/kyr in temperate regions. Accumulation of abiotic aragonite and calcite ooids and cement has similar spatial distributions, within mean latitudes between 25$\sp\circ$ and 28$\sp\circ$. Minimum surface water saturation ($\Omega\sb{\rm arg}$) requisite for ooid-cement carbonate precipitation is 3.8 for aragonite and 3.4 for calcite. During progressive continental emergence over the past 100 my, global epicratonic shelf area has decreased by about 50% while area of shelf carbonate accumulation has declined from 27.0 to 1.4 $\*$ 10$\sp6$ km$\sp2$, a reduction coeval with a latitudinal decrease in platform accumulation from about 50$\sp\circ$ to 28$\sp\circ$ latitude, and a six-fold decline in the shallow water carbonate accumulation from a Cretaceous rate of 0.6 $\*$ 10$\sp6$ km$\sp3$/my. Concurrently, the oceanic carbonate compensation depth deepened by about 1.5 km, mostly at the Eocene Oligocene boundary, attendant with a three-fold areal increase in pelagic carbonate deposition and a four-fold increase in deep water carbonate flux from a value of 0.05 $\*$ 10$\sp6$ km$\sp3$/my during the Cretaceous. Transfer of carbonate accumulation from shallow cratonic to deep oceanic settings records the central role of sedimentary environment surface area in the partitioning of finite carbonate fluxes within the global ocean. Areas of carbonate accumulation have varied in space and time, and deposition zones closest to the equator during periods of continental emergence and greatest in extent during maximum transgression. Study of Phanerozoic ooid and cement occurrences indicate that the ratio of inorganically precipitated calcite or aragonite has changed in response to variation in atmospheric CO$\sb2$ and/or oceanic temperature/saturation gradient. Abiotic aragonite formation predominated over calcite precipitation in equatorial localities during periods of continental emergence when areas of carbonate accumulation were confined to relatively low latitudes. Aragonite dominance in ooid/cement carbonate implies higher seawater saturation state and the areal restriction of carbonate sediment accumulation during periods of continental emergence suggests steeper pole-to-equator temperature/saturation gradients during periods of marine regression. Similarity of distribution patterns of Phanerozoic carbonate sequences and marine ooid/cement occurrences suggests that physicochemical processes that control levels of carbonate saturation are more important than biological processes for predicting sites of limestone accumulation.PhDGeologyUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/105251/1/9116261.pdfDescription of 9116261.pdf : Restricted to UM users only