Defining regional and local sediment sources in the ancestral Colorado River system: A heavy mineral study of a mixed provenance unit in the Fish creek-vallecito basin, Southern California
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Date
2023
Journal Title
Journal ISSN
Volume Title
Publisher
MDPI
Abstract
The Colorado River has flowed across the dextral strike-slip plate boundary between the
North American and Pacific plates since the latest Miocene or earliest Pliocene. The Fish Creek-
Vallecito Basin (FCVB) lies on the Pacific Plate in southern California, dextrally offset from the
point where the modern Colorado river enters the Salton Trough; it contains a record of ancestral
Colorado River sedimentation from 5.3–2.5 Ma. The basin stratigraphy exhibits a changing balance
between locally derived (L-Suite) and Colorado River (C-Suite) sediments. This paper focuses on the
Palm Springs Group (PSG), a thick fluvial and alluvial sequence deposited on the upper delta plain
(between 4.2–2.5 Ma) when the Colorado was active in the area, allowing the detailed examination
of the processes of sediment mixing from two distinct provenance areas. The PSG consists of three
coeval formations: 1) Canebrake Conglomerate, a basin margin that has coarse alluvial fan deposits
derived from surrounding igneous basement; 2) Olla Formation, fan-fringe sandstones containing
L-Suite, C-Suite, and mixed units; and 3) Arroyo Diablo Formation, mineralogically mature C-Suite
sandstones. Stratigraphic analysis demonstrates that the river flowed through a landscape with relief
up to 2000 m.
Description
Keywords
Palaeotopography, Climate change, Southern California, sediment flux, Geoscience
Citation
McGill, P. et al. (2023). Defining regional and local sediment sources in the ancestral Colorado River system: A heavy mineral study of a mixed provenance unit in the Fish creek-vallecito basin, Southern California. Geosciences ,13(2), 45. https://doi.org/10.3390/geosciences13020045