Fluvial sedimentology and architecture of the middle Frio Formation (Oligocene), Jim Wells, Klegerg, and Nueces Counties, south Texas

Conference · Fri Mar 01 00:00:00 EST 1991 · AAPG Bulletin (American Association of Petroleum Geologists); (United States)

OSTI ID:5584829

Kerr, D R ^[1]

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1. Univ. of Texas, Austin (United States)

The middle Frio Formation of the northeastern Gueydan fluvial system comprises fluvial and overbank deposits averaging 2,000 to 3,000 ft in thickness. Discrete genetic intervals are defined from subsurface studies using four cores totaling 575 ft, high-resolution resistivity borehole images, and electrical logs. A genetic interval is composed of four facies: (1) Channel-fill facies (30-ft thick and 2,500-ft wide) includes an overall fining-upward texture and upward diminution in sedimentary structure scale: intraclast gravel lag; large-scale trough cross-stratified, medium-grained sandstone; parallel-stratified and ripple-laminated fine-grained sandstone to sandy mudstone containing pedogenic nodule and root molds; (2) splay fine-grained sandstones (up to 20-ft thick) are parallel-stratified and ripple-laminated and are organized into beds with variable vertical thickness trends; (3)Levee sandstones and mudstones are thinly bedded with low-angle surfaces and slump structures; (4) floodplain mudstones contain structures and fabrics indicating variable wet and dry conditions. Three scales of architectural elements are readily identifiable in the subsurface. (1) Multitiered lateral accretion bars are the principal; channel-filling element; (2) Levee-confined channel systems have a lower tortuosity than the inferred thalweg, and splay complexes extend up to 2 mi from channel systems; (3) discrete genetic intervals form a continuum of stacking patterns: from laterally stacked, where sandstone bodies contact one another or are vertically separated by only a few feet of the floodplain facies, to vertically stacked, where floodplain facies substantially separate sandstone bodies.

• OSTI ID: 5584829
• Report Number(s): CONF-910403-; CODEN: AABUD
• Journal Information: AAPG Bulletin (American Association of Petroleum Geologists); (United States), Vol. 75:3; Conference: Annual meeting of the American Association of Petroleum Geologists (AAPG), Dallas, TX (United States), 7-10 Apr 1991; ISSN 0149-1423
• Country of Publication: United States
• Language: English

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