SANABRIA, DIEGO I.
Rice University, Houston, TX

Abstract: Climatic Control on the Development of Continental Stratigraphic Sequences: An Example From the Lower Jurassic Kayenta Formation of the Colorado Plateau

Sequence stratigraphy of continental strata is an increasingly active field in sedimentary research. Early sequence stratigraphic models dealt with the lowermost reaches of fluvial systems and their response to base level changes. Subsequent research has attempted to separate the effects of climate, tectonics, autocyclic processes, and base level changes in the genesis of stratigraphic sequences.

The Lower Jurassic Kayenta Formation of the Colorado Plateau constitutes an excellent example of climatic control on the development of stratigraphic sequences in and to semi-arid continental settings. The Kayenta Formation is the result of accumulation in a variety of depositional environments including flood-dominated ephemeral streams, eolian dunes, wadis, interdune areas, lakes, and shallow ephemeral ponds. Field work in Colorado, Utah, and Arizona suggests that wet/dry climatic cycles controlled the regional distribution of major facies tracts.

Dry periods are characterized by increased evapotranspiration rates, low lake levels, depressed water tables, and the development of widespread deflationary surfaces. Falls of the lake level triggered valley incision at the lower reaches of the fluvial systems. Thus, sequence boundaries at the base of incised valleys correlate with major deflationary surfaces in a landward direction.

Regionally extensive eolian facies preserved during the subsequent rise of the water table are essentially correlative with incised valley fills deposited mainly during the lowstand. Similarly, widespread fluvial deposits are dominant during wetter periods and correlate downdip with lacustrine parasequences arranged in aggradational to progradational stacking patterns.

AAPG Search and Discovery Article #90928©1999 AAPG Annual Convention, San Antonio, Texas