ABSTRACT

Two major episodes of shelf-margin reefing that occurred during the Early Cretaceous (Aptian-Albian-Cenomanian) are represented by the transgressive Hosston-Sligo complex and the regressive Glen Rose-Edwards complex. The Glen Rose-Edwards sequence can be broken up into 3 distinct carbonate buildups: middle Glen Rose, upper Glen Rose, and Edwards. Eustatic sea level rise, subsidence, and reef growth or sediment accumulation were dominant influences on shelf-margin deposition. The respective reef trends thicken eastward from east Texas into central Louisiana and southern Mississippi due to increased rate of subsidence and sea level rise in that direction.

Well cores and cuttings indicate that similar lithofacies occur throughout the Lower Cretaceous shelf margin. However, lithologic and diagenetic factors combined to produce extraordinary sections of facies-controlled porosity within the middle Glen Rose reef buildup. Although both hydrodynamic and organic processes were important factors in growth and maintenance of the middle Glen Rose reef buildup, the buildup is best described as an ecologic (organic) reef. A regional meteoric hydrologic system was responsible for extensive secondary moldic porosity in the skeletal-supported and grain-supported sediments. Algal binding within the reef interval contributed to the development of fenestral-moldic porosity. Extensive dolomitization is common and acted to create or destroy porosity.

Hydrocarbon production from the Lower Cretaceous shelf margin in the east Texas-Louisiana-Mississippi region has been limited mainly to the Edwards section. Application of recently developed facies and diagenetic models may increase further exploration potential of the entire Cretaceous shelf margin.

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