Preliminary results on depositional cyclicity of Cisco Group (Virgilian and Wolfcampian), eastern shelf, north-central Texas

Conference · Mon Feb 01 00:00:00 EST 1993 · Geological Society of America, Abstracts with Programs; (United States)

OSTI ID:5975728

Yang, Wan; Kominz, M A ^[1]

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1. Univ. of Texas, Austin, TX (United States). Dept. of Geological Sciences

A hierarchical pattern of cyclic fluvial/deltaic, shelf, and slope siliciclastics and carbonates was delineated in a preliminary outcrop and subsurface study of Cisco strata. About 50 outcrop transgressive-regressive cycles were delineated based on lithology, fossil content, depositional environment, and stratigraphic position from [approximately]100 measured sections in the Colorado River to Brazos River valley area. The average cycle thickness is 7--8m. Typically, transgression is represented by marly mudstone and limestone; maximum transgression by black shale; regression by limestone and siliciclastics, capped by variegated paleosol and erosional surfaces. Complete cycles are rare: black shale was often not present; transgressive and regressive limestones coalesce; siliciclastics may comprise the entire cycle. Preliminary cycle correlation indicates that major limestone beds are correlatable, as are many minor cycles. The authors have differentiated regional transgression-regression events from local ones, suggesting that cyclic deposition was controlled by both auto- and allo-cyclic processes. Subsurface lithologic interpretation delineated 32 limestone-shale and 24 sandstone-shale cycles on Well-log 1 located on carbonate bank; 35 limestone-shale and 30 sandstone-shale cycles on Well-log 2 on the fluvial/deltaic system. The average cycle thickness is [approximately]10m. Gamma analysis of Kominz and Bond (1990) and spectral analysis were applied to test and estimate cycle periodicity and accumulation rates of different facies of the cycles. Gamma analysis tests the assumption that cycle period and accumulation rates of different facies are constant. Best-fit gammas (= time/thickness) obtained for both well-logs were used to convert thickness into time. Spectral analysis of the time series detected several distinct spectral peaks.

• OSTI ID: 5975728
• Report Number(s): CONF-9303212-; CODEN: GAAPBC
• Journal Information: Geological Society of America, Abstracts with Programs; (United States), Vol. 25:1; Conference: 27. annual Geological Society of America (GSA) South-Central Section meeting, Fort Worth, TX (United States), 15-16 Mar 1993; ISSN 0016-7592
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
SEDIMENTARY BASINS
DEPOSITION
GAMMA LOGGING
STRATIGRAPHY
TEXAS
AGE ESTIMATION
CARBONATE ROCKS
GEOLOGIC HISTORY
LITHOLOGY
PALEONTOLOGY
SANDSTONES
SHALES
DEVELOPED COUNTRIES
GEOLOGIC STRUCTURES
GEOLOGY
NORTH AMERICA
PETROLOGY
RADIOACTIVITY LOGGING
ROCKS
SEDIMENTARY ROCKS
USA
WELL LOGGING
580000* - Geosciences