About This Item

Share This Item

The AAPG/Datapages Combined Publications Database

AAPG Bulletin


Volume: 49 (1965)

Issue: 3. (March)

First Page: 346

Last Page: 346

Title: Facies and Development of the Colorado River Delta in Texas: ABSTRACT

Author(s): W. H. Kanes, Dana Wells, A. C. Donaldson

Article Type: Meeting abstract


The Recent delta of the Colorado River of Texas is an exceptional model for analyzing sediment and faunal facies relationships in environments associated with deltas. The small size facilitates close spacing of cores, which is essential for detailed facies study. Moreover, air photographs document growth from a straight shoreline to the lobe-shaped deposit formed prior to artificial channeling of the river through a barrier island. A 6- to 8-foot platform of deltaic sediments now dividing Matagorda Bay was deposited in the 6-year period following removal of an upstream log jam. Continuous cores (37) and borings (10) define the deltaic facies complex and the underlying bay facies in the northeastern section of the delta, which is unaffected by man-made modifications. The s quence of facies and environments encountered in sections is: (1) clays and silts, 1 to 5 feet thick (delta plain), including silty clays and clayey silts containing numerous roots and root fibers (natural levee), silty clays with roots and "algal-encrusted" washout pans (marsh), and massive to burrowed clays (channel fill); (2) sands, 2 to 6 feet thick, characterized by small-scale cross bedding (delta front); (3) laminated silty clays, 1 to 5 feet thick, (prodelta); and (4) laminated to burrow-mottled silty clays and clayey silts, 10 to 14 feet thick (bay), unconformably overlying the Pleistocene. Color variations, together with X-ray radiographs recording laminations and burrows, are most useful in distinguishing between facies of bay and prodelta environments. The faunas characterizi g the facies and environments are more variable than are the sediments; juvenile and small mollusks, less than ΒΌ inch, seem more definitive of environments here than do Foraminifera. Subsidence of 1 to 2 feet is estimated to have resulted from compaction since initial delta formation.

End_of_Article - Last_Page 346------------

Copyright 1997 American Association of Petroleum Geologists