Sandstone Trends, Sequence Framework, and Depositional Settings of the Upper Cretaceous Woodbine Group: "Eaglebine" Play, Southern East Texas Basin
Hentz, Tucker F.; Ambrose, William A.
The Woodbine Group of the southern East Texas Basin has come under increasing scrutiny as an emerging resource play. Termed the "Eaglebine" play, which also includes well-developed overlying Turonian Eagle Ford Group sandstones, because it is in the early stages of development, little is known about the regional distribution and depositional character of the Woodbine reservoir facies. In Leon, Madison, and western Houston Counties, the Woodbine section is significantly shalier than in the basin-axis area to the northeast, reflecting a regional facies transition to off-axis Pepper Shale facies of the southwest. Moreover, sandstone intervals are correspondingly thinner and discontinuous, ranging from only 0 to 20 ft (0-6 m) in thickness but locally >50 ft (>15 m).
Thickest sandstone intervals occur at the tops of at least five upward-coarsening, highstand-dominated sequences in the upper half of the Woodbine Group between third-order transgressive systems tracts above the Cenomanian Buda Limestone and at the base of the Eagle Ford Group. Correlation from the basin-axis area northeast of the study area indicates that the succession, which thins by at least one-third, is equivalent to only the lower two-thirds of the thickest Woodbine basin fill. The thinning represents systematic depositional pinch-out (onlap) of fourth-order sequences of the upper Woodbine section toward the west margin of the basin, as previously documented in a study of its east margin.
Gross-sandstone maps indicate that primary sandstone trends of the middle Woodbine sequences are oriented north-northeast to south-southwest, recording digitate delta lobes. Sandstones of the uppermost Woodbine section, which occur in the west part of the study area (western Houston County), are as much as 60 ft [18 m] thick and massive.
Two middle Woodbine cores from southwest Leon County are characterized by fine- to very fine grained, planar-stratified, and rippled sandstone overlying soft-sediment-folded siltstones. They represent fluvial-dominated, delta-front facies at the downdip terminations of the digitate delta. In contrast, facies from the uppermost Woodbine in Houston County contain beds of intensely burrowed, fine-grained sandstone that most likely record deposition in a wave-dominated, lower- to midshoreface setting.
AAPG Search and Discovery Article #90163©2013AAPG 2013 Annual Convention and Exhibition, Pittsburgh, Pennsylvania, May 19-22, 2013