Evolution of Prograding Channels and Relation to Splay Deltas: Geomorphology and Reservoir Characteristics From the Red River Delta in Lake Texoma

Abstract

Examination of modern fluvial-lacustrine systems reveal a relative absence of lobate deltas and a higher frequency of prograding channels into the lake basin. In order to better understand the morphology of lake deltas and the processes of prograding channels, we examined the Red River delta in Lake Texoma, TX. Lake and river beds were cored with a Dutch auger to map the lithology and associate facies, and successive aerial photos were utilized to interpret delta evolution through time. Vertical aerial photographs show an initial prograding Red River channel formed along the northeast bank of Lake Texoma beginning in 1984. In 2004, the levee of the prograding channel was breached, the existing channel was abandoned, and a lobate delta began to form to the south. This was followed by the formation of a step down, falling stage lobate delta that laps onto the face of the first delta. Between 2012 and 2014, these two deltas coalesced into a new prograding channel that cut through and persists today along the southwest bank of Lake Texoma. Coring results indicate that sands accumulate at the location of avulsion, the lobate deltas consist of coarsening upwards sands, and the new channel is mud dominated with minimal sand reaching the channel mouth and abundant levee sand deposits. We propose the initial levee breach provided a sand source locally available to the system adjacent to the channel, allowing for the formation of the coarsening upwards, sandy lobate deltas to form. The shift from lobate delta formation to a prograding channel morphology is caused by the channel profile lengthening sufficiently to separate the sand from the mud load in the Red River delta, as evidenced by the lack of sands at the river mouth. The channel is prograding into Lake Texoma by eroding the mouth bar and simultaneously depositing sands onto the levees. Two facies will be left in the rock record, coarsening upwards lobate delta sands, and mud dominated channel deposits with extensive thin sand sheets as wings. These deposits should be, and are, common on high-accommodation floodplain deposits of the rock record.

AAPG Datapages/Search and Discovery Article #90259 ©2016 AAPG Annual Convention and Exhibition, Calgary, Alberta, Canada, June 19-22, 2016