Origin and Geometry of Storm-Deposited Sand Beds in Modern Sediments of the Texas Continental Shelf

  1. D. J. P. Swift4,
  2. G. F. Oertel4,
  3. R. W. Tillman5 and
  4. J. A. Thorne6
  1. J. W. Snedden1,† and
  2. D. Nummedal2

Published Online: 14 APR 2009

DOI: 10.1002/9781444303933.ch8

Shelf Sand and Sandstone Bodies: Geometry, Facies and Sequence Stratigraphy

Shelf Sand and Sandstone Bodies: Geometry, Facies and Sequence Stratigraphy

How to Cite

Snedden, J. W. and Nummedal, D. (1992) Origin and Geometry of Storm-Deposited Sand Beds in Modern Sediments of the Texas Continental Shelf, in Shelf Sand and Sandstone Bodies: Geometry, Facies and Sequence Stratigraphy (eds D. J. P. Swift, G. F. Oertel, R. W. Tillman and J. A. Thorne), Blackwell Publishing Ltd., Oxford, UK. doi: 10.1002/9781444303933.ch8

Editor Information

  1. 4

    Norfolk, Virginia, USA

  2. 5

    Tulsa, Oklahoma, USA

  3. 6

    Plano, Texas, USA

Author Information

  1. 1

    Mobil Exploration and Producing Services, Inc., P.O. Box 650232, Dallas, TX 75265, USA

  2. 2

    Department of Geology and Geophysics, Louisiana State University, Baton Rouge, LA 70803, USA

  1. Mobil Research and Development Corporation, Dallas Research Laboratory, P.O. Box 819047, Dallas, TX 75381-9047, USA

Publication History

  1. Published Online: 14 APR 2009
  2. Published Print: 30 JAN 1992

ISBN Information

Print ISBN: 9780632032372

Online ISBN: 9781444303933

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Keywords:

  • origin and geometry of storm-deposited sand beds in modern sediments of Texas continental shelf;
  • sedimentary characteristics of discrete sand beds;
  • textural analysis performed using different methods;
  • hummocky cross-stratification (HCS);
  • lateral grain-size trends;
  • sand body geometry - direct function of environment of deposition and processes operating within environment;
  • shelf sand transport processes

Summary

Box cores taken from surficial sediments of the central Texas continental shelf reveal the presence of thin (1–10 cm) discrete beds of sand and silt in an otherwise clayey sedimentary section. The discrete beds are characterized by vertical upward fining grain-size trends, grading from very fine sand to fine silt. Physical sedimentary structures are dominantly planar laminae that locally pass upwards into low-angle inclined lamination. Basal contacts are always sharp, while upper contacts can be either sharp or gradational. Offshore decreases in grain size, thickness and frequency of the discrete sand beds are also observed.

This evidence is compatible with the two hypotheses commonly offered to explain the origin of storm-deposited beds: storm-surge ebb induced turbidity currents or geostrophic storm flows.

Consideration of the driving forces behind shelf sediment transport and mapping of the distribution of one recent storm bed permit further testing of these hypotheses. The along-shelf continuity of a single sand bed, dated as contemporaneous with the passage of Hurricane Carla across the Texas shelf in 1961, is inconsistent with the turbidity current hypothesis. The strike-trending sand body geometry and the seaward fining within the Carla bed imply a sand transport pathway beginning in the shoreface zone and oriented obliquely offshore and along shelf.

Analysis of current and wave measurements from the shelf during the passage of smaller storms, such as Hurricane Allen, suggests that storm flows are geostrophically balanced, driven primarily by the wind-induced hydrostatic pressure gradients. There appears to be a recognizable relationship between the wind field, sea-surface slope, wave propagation, and near-bottom combined-flow kinematics. Building upon this, a sand transport model was developed for Hurricane Carla. This reconstruction indicates that the combined flow present during the storm had sufficient strength and the proper transport kinematics to account for the observed sand body geometry.