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GMEG - Geology, Minerals, Energy, & Geophysics Science Center

Geologic and Geomorphic Evolution of the lower Colorado River




Geology and Geomorphology of the southern Lower Colorado River Valley

Geologic mapping of the southern Colorado River corridor (SoCOLO), which extends from Parker Dam to Imperial Dam and includes the Great Valley of the Lower Colorado River.

The Great Valley includes the Parker, Palo Verde and Cibola valleys. This reach of the river contrasts starkly with the NoLOCO. The topography includes a more widely dispersed array of rugged ranges protruding from broad plains of river and tributary alluvium, thus giving the region more of a ‘buried’ character. The Miocene geologic history of this reach is dominantly one of large-scale extension expressed in metamorphic core-complexes and related upper plate tilted fault blocks. Syn-extensional basins were local but merged with adjacent basins as extension waned. The late Cenozoic geologic history of the river in the SoLOCO is also somewhat different and may include a complex interaction among the river’s ancient delta, terminal lake(s), and the sea. Paleontological data suggests a complex history involving Marine incursion followed by restricted marine or saline lacustrine conditions, both in conjunction with the arrival of Colorado River water from the north. Our mapping and topical study efforts will focus on the mapping, characterization, and analysis of deposits, landforms, sedimentary facies and micropaleontologic evidence that bear on this important difference between the two parts of the proposed map area.

Objectives: The overall objective of this task is to develop 1:50,000 geologic maps of the river corridor between Parker Dam and Imperial Dam (SoCOLO). Overall, this task involves mapping in a large area with fewer existing geologic datasets and will require more work overall than the NoLOCO map. Therefore, under the time constraints of a five-year project, we will first focus on the following: mapping in four 1:24,000 geologic quadrangles in collaboration with a STATEMAP-funded AZGS mapping effort; and publication of a 1:100,000-scale map of the east part of the Blythe 30’x60’quadrangle.

Map showing key places, geologic map coverage land management status







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