Changes

==Interpreting the maps==

==Interpreting the maps==

Biofacies map patterns are defined by distribution of benthic foraminiferal biofacies.<ref name=ch04r7 /><ref name=ch04r9 /> Figure 4-29 shows the biofacies distribution below, within, and above the ''Glob alt'' sandstone interval. In upward stratigraphic order, these intervals are interpreted as the sediment accumulated during (1) falling, (2) low, and (3) rising phases of sea level, respectively. A scenario to explain biofacies and sediment patterns in the example is as follows.

 

Biofacies map patterns are defined by distribution of benthic foraminiferal biofacies.<ref name=ch04r7 /><ref name=ch04r9 /> [[:file:sedimentary-basin-analysis_fig4-29.png|Figure 2]] shows the biofacies distribution below, within, and above the ''Glob alt'' sandstone interval. In upward stratigraphic order, these intervals are interpreted as the sediment accumulated during (1) falling, (2) low, and (3) rising phases of sea level, respectively. A scenario to explain biofacies and sediment patterns in the example is as follows.

* During the lowering of sea level, the biofacies distributions and sites of maximum sediment accumulation move seaward (Figure 4-29A) where they are deposited on top of the preceding condensed section and associated maximum flooding surface (Figure 4-18). Within the initial lowering phase, the rate of slope and intraslope basin sediment accumulation increases, with fine-grained deposits above the underlying condensed section. As lowering progresses, the river systems bypass sediment across the shelf, depositing it directly on the upper slope. Remobilized sand and sand supplied directly from rivers during floods may be transported downslope by gravity-flow processes, depositing potential reservoirs.<ref name=ch04r81>Prior, D., B., Bornhold, B., D., Wiseman, W., J. Jr., Lowe, D., R., 1987, Turbidity current activity in a British Columbia fjord: Science, vol. 237, p. 1330–1333., 10., 1126/science., 237., 4820., 1330</ref> These sands accumulate at changes in the depositional gradient as slope fan and basin-floor fan deposits within the intraslope basins (minibasins).<ref name=ch04r22>Bouma, A., H., 1982, [http://archives.datapages.com/data/specpubs/history2/data/a110/a110/0001/0550/0567.htm Intraslope basins in northwest Gulf of Mexico: a key to ancient submarine canyons and fans], in Watkins, J. S., and C. L. Drake, eds., Studies in Continental Margin Geology: AAPG Memoir 34, p. 567–581.</ref>

* During the lowering of sea level, the biofacies distributions and sites of maximum sediment accumulation move seaward (Figure 4-29A) where they are deposited on top of the preceding condensed section and associated maximum flooding surface (Figure 4-18). Within the initial lowering phase, the rate of slope and intraslope basin sediment accumulation increases, with fine-grained deposits above the underlying condensed section. As lowering progresses, the river systems bypass sediment across the shelf, depositing it directly on the upper slope. Remobilized sand and sand supplied directly from rivers during floods may be transported downslope by gravity-flow processes, depositing potential reservoirs.<ref name=ch04r81>Prior, D., B., Bornhold, B., D., Wiseman, W., J. Jr., Lowe, D., R., 1987, Turbidity current activity in a British Columbia fjord: Science, vol. 237, p. 1330–1333., 10., 1126/science., 237., 4820., 1330</ref> These sands accumulate at changes in the depositional gradient as slope fan and basin-floor fan deposits within the intraslope basins (minibasins).<ref name=ch04r22>Bouma, A., H., 1982, [http://archives.datapages.com/data/specpubs/history2/data/a110/a110/0001/0550/0567.htm Intraslope basins in northwest Gulf of Mexico: a key to ancient submarine canyons and fans], in Watkins, J. S., and C. L. Drake, eds., Studies in Continental Margin Geology: AAPG Memoir 34, p. 567–581.</ref>