Print this pageEPR MEMORANDUM REPORT 23
OCTOBER 1956
SEDIMENTARY FEATURES DIAGNOSTIC OF ALLUVIAL POINT BAR SANDS*
* Appreciation is expressed to Shell Oil Company, AAPG, and Rufus J. LeBlanc, Sr., for their respective efforts, and permission, in regard to publication of this classical report on clastic sediments.
BY
H. A. BERNARD AND C. F. MAJOR
INTRODUCTION
Requests for criteria useful in the recognition of subsurface
alluvial sands and the prediction of their trends are increasing
steadily since it is becoming more apparent that considerable
quantities of hydro carbons occur in these deposits.
This report describes the characteristic depositional features of
stream meander or point bar deposits, predominantly sands, and
has been prepared in response to requests from operating
personnel of Shell Oil Company A more detailed report on the
depositional sequences, trends, and especially, the directional
features of point bar deposits is in preparation.
The report includes numerous photographs of the sediments and
sedimentary structures, together with comments on their origin
and relation ship to specific depositional areas within the river
meander loop portion of an alluvial environment. Sediments and
features of similar nature occur in deltaic environments subject
to sizable floods.
The principal streams of the southeast Texas Gulf Coast Plain,
the Brazos, Oyster Creek-Brazos, Trinity. Colorado, Caney
Creek-Colorado, and Sabine rivers were studied (Figure 1), but most of the observations were
made on the Brazos River near Richmond, Texas (Figure
2). Sediments and sedimentary features similar to those of
the above streams have been observed in the Tertiary and
Quaternary deposits of the Gulf and Atlantic coastal plains. The
Gulf Coast rivers are representative of most coastal plain rivers
through out the world, and criteria established from the study of
the deposits of these streams should be applicable to the studies
of most ancient alluvial sediments of similar depositional
basins.
