Mixed Carbonate-Siliciclastic Sequences

The study of carbonate-siliciclastic mixed sequences has seen an increase in the number of investigations that focus on mixed settings as part of the continuum between the carbonate and clastic end members. Cyclic deposition in mixed basins by reciprocal sedimentation has become one of the foundation blocks for sequence stratigraphy. In addition, these mixed sequences have a variety of distinctive petroleum reservoir characteristics, important for both exploration and development programs. The emphasis now is on reevaluating ancient sequences in the light of a more dynamic understanding of spatial and temporal variations and controls on these sequences. Examples in this volume are subdivided under the following headings: Shelf Wide, Coastal and Inner Shelf, Middle to Outer Shelf, Slope to Basin and Paleokarst. Many mixed sequences have been described in the literature, but understanding the controls of these sequences from a process approach in now in an adolescent stage.
Slope and Basinal Carbonate Deposition in the Nolichucky Shale (Upper Cambrian), East Tennessee: Effect of Carbonate Suppression by Siliciclastic Deposition on Basin-Margin Morphology Available to Purchase
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Published:January 01, 1991
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CiteCitation
J. L. Foreman, K. R. Walker, L. J. Weber, S. G. Driese, R. B. Dreier, 1991. "Slope and Basinal Carbonate Deposition in the Nolichucky Shale (Upper Cambrian), East Tennessee: Effect of Carbonate Suppression by Siliciclastic Deposition on Basin-Margin Morphology", Mixed Carbonate-Siliciclastic Sequences, Anthony J. Lomando, Paul M. Harris
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Abstract
Intraclastic limestone, thin fossiliferous limestone, and oolitic limestone interbedded with fissile shale are characteristic of the Nolichucky Shale (Upper Cambrian) in the Whiteoak Mountain thrust sheet, eastern Tennessee. These lithologies are interpreted as slope and basinal units deposited in water depths that may have exceeded 250 to 300 m. Intraclastic limestone debris flow deposits and skeletal and oolitic calcarenite turbidites indicate that nearly all carbonate is allochthonous, derived from up-slope and platform shallow-water environments. Storms were a dominant factor in initializing down-slope transport from shallower-water settings.
Polymictic limestone conglomerate and shallow-water-derived calcarenite, composed of ooids, peloids, and fossils, indicate that depositional slopes were steep enough at times to permit considerable transport (in excess of 20 km) from up-slope areas. During times of increased siliciclastic sedimentation, carbonate production was suppressed and the basin margin had a gentle ramp morphology. Algal and oolitic shoals built up close to sea level when siliciclastic input was reduced, resulting in the progradation of carbonate facies into the basin. Depositional slopes at the basin margin were steepened to the point that gravity sediment flows were effective in transporting shallow-water carbonate lithologies into the basin.