Mass-transport deposits, though common in carbonate basins, normally occur as widespread sheets or debris wedges, as in the Devonian of Canada and elsewhere, or in modern interplatform troughs of the Bahamas.

Reexamination of a seaward-prograding Cambrian and Ordovician continental margin section in central Nevada reveals a 150-m thick interval whose facies resemble current models of submarine-fan deposition. The upper 100 m of sediment is assigned to an inner-fan setting and is characterized by submarine slides and several entrenched channels 10 m deep and 500 m wide. The channels are filled with disorganized boulder-bearing conglomerates but are not arranged in any well-defined thinning- and fining-upward sequences. Stratigraphically below this interval are thinning- and fining-upward organized, pebble to cobble-bearing channelized conglomerates, 30 to 50 m thick. These channels are 1 to 5 m deep, 20 to 100 m wide, and rapidly coalesce laterally and vertically. The conglomerates grade la erally into and are interbedded with thin and discontinuously bedded ripple-laminated and graded calcarenites, similar to detrital overbank-levee and interchannel deposits. These sedimentary units probably represent a system of braided channels in a mid-fan position. Below the braided channels are 10 to 20 m of thickening- and coarsening-upward cycles of virtually nonchanneled beds; beds in the cycles are composed of calcarenites exhibiting Bouma divisions. These carbonate sand sequences are interpreted to represent prograding outer-fan lobes.

The recognition of carbonate submarine-fan sequences raises several questions. (1) What sedimentologic and tectonic conditions are conducive to fan development in carbonate provinces? (2) Do these conditions resemble those for clastic-fan development, or do carbonate provinces have unique requirements? By recognizing carbonate submarine fans and the geologic conditions that control their sediment dispersal patterns, areas of maximum sediment accumulation may be predicted as an aid in exploring for petroleum reservoirs of deeper water carbonate environments.

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