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The AAPG/Datapages Combined Publications Database
Houston Geological Society Bulletin
Abstract
Abstract: Denkman Sandstone Member (Norphlet)-An Important Jurassic
Reservoir in Mississippi, Alabama, and Florida
By
A clean, generally well-sorted, commonly
porous, sandstone unit separates marine lower Smackover carbonate mudstone above from nonmarine red
beds of the Norphlet Formation below in parts of southern Mississippi, southwestern
Alabama, and
northwestern Florida. This sandstone unit has been
called basal Smackover, Norphlet, or Denkman.
The name Denkman Sandstone was proposed for this
unit by Murray (1961) who designated the Lion No. 2
Denkman, Sec. 22, T7N, R4E, Rankin County, Mississippi,
as the type section. The Denkman Sandstone,
which locally exceeds 1000 feet in thickness,
a lithologically distinct mappable unit. Nevertheless,
it is included in the Norphlet Formation by the
industry; and in this paper it is called the Denkman
Sandstone Member of the Norphlet Formation.
The Denkman Member is overlain with little or
no gradation by basal Smackover carbonates and
grader downward into red beds, the more characteristic
lithology of the Norphlet in the Gulf Cod Province.
The Denkman changes updip into a conglomeratic facies interpreted
to be alluvial fan and fluvial deposits. The Denkman consists of well-sorted,
fine-to-medium grained, in part rounded and frosted, quartz grains with some feldspar,
chert, and rock fragment grains. The section is characterized by thick sets of planar cross laminae.
It does not contain fossils or carbonate beds and commonly has good intergranular porosity and permeability.
Unlike sandstone beds in the overlying Smackover, it contains little or no carbonate
cement except in its uppermost part. The intergranular cement is commonly anhydrite or silica and
locally halite.
Regional distribution and stratigraphic relationships show the Denkman to be a clean sandstone
facies of the Norphlet elastic wedge complex derived from north and east source areas. The vertical
sequence of lithology and sedimentary structures indicate a fluvial and eolian origin far most of the
Denkman sandstone. Locally, the upper few feet are marine in origin, probably the result of reworking
during subsequent Smackover transgression. Except for this marine upper portion, the
Denkman Member marks the end of a major Jurassic evaporite to nonmarine cycle (Werner Anhydrite -
Loyann Salt - Norphlet depositional cycle). It is overlain by a more complete marine to nonmarine
cycle (Smackover-Buckner-Haynesville-Cotton Valley depositional cycle).
The Denkman Member commonly has excellent reservoir properties. Porosity is locally present
below depths of 20,000 feet and production has been established at South State Line Field between
17,909 and 18,279 feet. It has been found productive from Jackson, Mississippi, southeastward
over a distance of 180 miles to near Pensacola, Florida. The Denkman is an oil reservoir at the
Pelahatchie, Prairie Branch, Archusa Springs, East Nancy, Little Escambia Creek, Jay, Mount
Curmel and Blackjack Creek Fields and a gas and condensate reservoir at Flomaton, Big Escambia
Creek and South State Line Fields. It is and will continue to be an important exploration objective
along the southeast part of the Jurassic trend in the Gulf Coast Province. End_of_Record - Last_Page 1---------------