Changes

Carbonate sediments with ribbon geometries show a complex lateral facies progression in map view. A tendency for lateral accretion in successive cycles creates a subtle shingled geometry, which can make accurate correlation difficult (see Chapter 10, this publication, and [[:File:M91FG67.JPG|Figure 2]]). For example, laterally accreting grainstones show a shingled geometry on a kilometer scale in Albian carbonates in northern Mexico ([[:File:M91FG196.JPG|Figure 1]]).<ref name=Osleger /> It can be a mistake to fit a layer-cake geometry to these systems because this results in reservoir models where lateral connectivity is predicted to be more extensive than is the case.<ref>Tinker, S. W., 1996, [http://archives.datapages.com/data/bulletns/1994-96/data/pg/0080/0004/0450/0460.htm Building the 3-D jigsaw puzzle, applications of sequence stratigraphy to 3-D reservoir characterization, Permian Basin]: AAPG Bulletin, v. 80, no. 4, p. 460–484.</ref> Facies belts may be difficult to define as lithofacies variation in carbonates is frequently transitional rather than sharp.

Carbonate sediments with ribbon geometries show a complex lateral facies progression in map view. A tendency for lateral accretion in successive cycles creates a subtle shingled geometry, which can make accurate correlation difficult (see Chapter 10, this publication, and [[:File:M91FG67.JPG|Figure 2]]). For example, laterally accreting grainstones show a shingled geometry on a kilometer scale in Albian carbonates in northern Mexico ([[:File:M91FG196.JPG|Figure 1]]).<ref name=Osleger /> It can be a mistake to fit a layer-cake geometry to these systems because this results in reservoir models where lateral connectivity is predicted to be more extensive than is the case.<ref>Tinker, S. W., 1996, [http://archives.datapages.com/data/bulletns/1994-96/data/pg/0080/0004/0450/0460.htm Building the 3-D jigsaw puzzle, applications of sequence stratigraphy to 3-D reservoir characterization, Permian Basin]: AAPG Bulletin, v. 80, no. 4, p. 460–484.</ref> Facies belts may be difficult to define as lithofacies variation in carbonates is frequently transitional rather than sharp.

Carbonate sedimentation is very rapid and the build-up of carbonate sediment can exceed sea-level rise in a short period of time. For example, Neumann and Land (1975) estimated that the carbonate sediment accumulation rate in the Bight of Abaco in the Bahamas is 120 mm (5 in.) per thousand years. This is about three times the estimated subsidence rate of 38 mm (1.4 in.) per thousand years. The phrase carbonate factory is commonly used to describe the manner in which large volumes of sediment are produced on tropical shelfs.

Carbonate sedimentation is very rapid and the build-up of carbonate sediment can exceed sea-level rise in a short period of time. For example, Neumann and Land<ref>Neumann, A. C., and L. S. Land, 1975, Lime mud deposition and calcareous algae in the Bight of Abaco, Bahamas: A budget: Journal of Sedimentary Petrology, v. 45, no. 4, p. 763–786.</ref> estimated that the carbonate sediment accumulation rate in the Bight of Abaco in the Bahamas is 120 mm (5 in.) per thousand years. This is about three times the estimated subsidence rate of 38 mm (1.4 in.) per thousand years. The phrase carbonate factory is commonly used to describe the manner in which large volumes of sediment are produced on tropical shelfs.

Vertically, carbonates can be characterized by high-frequency stacking, with shoaling-upward cycles a few meters thick. Westphal et al. (2004) described high-frequency depositional cycles from the Mississippian Madison Formation in the Wind River Basin of Wyoming. The cycles occur over a meter-scale thickness and consist of a lower transgressive and an upper regressive hemicycle. The transgressive hemicycle is dominated by tidal flat sediments (laminated mudstone and wackestone) and subtidal deposits (e.g., stromatilites). The regressive hemicycle comprises high-energy carbonate sand-shoal facies ([[:File:M91FG197.JPG|Figure 3]]).

Vertically, carbonates can be characterized by high-frequency stacking, with shoaling-upward cycles a few meters thick. Westphal et al. (2004) described high-frequency depositional cycles from the Mississippian Madison Formation in the Wind River Basin of Wyoming. The cycles occur over a meter-scale thickness and consist of a lower transgressive and an upper regressive hemicycle. The transgressive hemicycle is dominated by tidal flat sediments (laminated mudstone and wackestone) and subtidal deposits (e.g., stromatilites). The regressive hemicycle comprises high-energy carbonate sand-shoal facies ([[:File:M91FG197.JPG|Figure 3]]).