Changes

==Microfossil abundance patterns==

==Microfossil abundance patterns==

Microfossil abundance patterns derived from examining well cuttings may provide highresolution observations for identifying depositional sequences. Total microfossil abundance patterns reflect changes in sediment accumulation rates, provided the biogenic productivity varies less than the sediment accumulation rate. For example, during the reduced rate of sediment accumulation associated with transgression, the middle-shelf and deeper transgressive-phase deposits may be characterized by an increase in fossil abundance due to relative terrigenous sediment starvation and consequent concentration of fossil material. If the same conditions of biotic productivity hold during the increased rate of sediment accumulation associated with a [[Depocenter#Sediment_supply_rate_and_facies_patterns|prograding]] system, the accumulated sediments may be characterized by a decrease in fossil abundance due to dilution and environmental stress.<ref name=ch04r87>Shaffer, B., L., 1987a, The potential of calcareous nannofossils for recognizing Plio–Pleistocene climatic cycles and sequence boundaries on the shelf: Proceedings, Gulf Coast Section SEPM 8th Annual Research conference, p. 142–145.</ref><ref name=ch04r10>Armentrout, J., M., Clement, J., F., 1990, Biostratigraphic calibration of depositional cycles: a case study in High Island–Galveston–East Breaks areas, offshore Texas: Proceedings, Gulf Coast Section SEPM 11th Annual Research Conference, p. 21–51.</ref>

Microfossil abundance patterns derived from examining well cuttings may provide highresolution observations for identifying depositional sequences. Total microfossil abundance patterns reflect changes in sediment accumulation rates, provided the biogenic productivity varies less than the sediment accumulation rate. For example, during the reduced rate of sediment accumulation associated with transgression, the middle-shelf and deeper transgressive-phase deposits may be characterized by an increase in fossil abundance due to relative terrigenous sediment starvation and consequent concentration of fossil material. If the same conditions of biotic productivity hold during the increased rate of sediment accumulation associated with a [[Depocenter#Sediment_supply_rate_and_facies_patterns|prograding]] system, the accumulated sediments may be characterized by a decrease in fossil abundance due to dilution and environmental stress.<ref name=ch04r87>Shaffer, B. L., 1987a, The potential of calcareous nannofossils for recognizing Plio–Pleistocene climatic cycles and sequence boundaries on the shelf: Proceedings, Gulf Coast Section SEPM 8th Annual Research conference, p. 142–145.</ref><ref name=ch04r10>Armentrout, J. M.,and J. F. Clement, 1990, Biostratigraphic calibration of depositional cycles: a case study in High Island–Galveston–East Breaks areas, offshore Texas: Proceedings, Gulf Coast Section SEPM 11th Annual Research Conference, p. 21–51.</ref>

==Applying abundance patterns==

==Applying abundance patterns==