Eocene–Recent drainage evolution of the Colorado River and its precursor: an integrated provenance perspective from SW California

Abstract

The Colorado River in the SW of the USA is one of Earth's few continental-scale rivers with an active margin delta. Deformation along this transform margin, as well as associated intra-plate strain, has resulted in significant changes in sediment routing from the continental interior and post-depositional translation of older deltaic units. The oldest candidate deposits, fluvial sandstones of the Eocene Sespe Group, are now exposed in the Santa Monica Mountains, 300 km to the north of the Colorado River. Heavy mineral data from this basin indicate that sediment was sourced by a large river system, with some affinity to the early Pliocene Colorado River, but was unlikely to have been integrated across the Colorado Plateau. Sedimentological and mineralogical evidence from the earliest (c. 5.3 Ma) unequivocal Colorado River-derived sediments in the Salton Trough provide evidence for a rapid transition from locally derived sedimentation. Lack of evidence for a precursor phase of suspended-load sediment suggests that drainage capture took place in a proximal position, favouring a ‘top-down’ process of lake spillover. Following drainage integration, significant changes in heavy mineral assemblages of fluvio-deltaic sediments, particularly evident from apatite–tourmaline and garnet–zircon indices, as well as U–Pb ages of detrital zircons, document the integration of the fluvial system to its present form and progressive incision of the Colorado Plateau from the Miocene to the present.

Taxonomic hypotheses and the biogeography of speciation in the Tiger Whiptail complex (Aspidoscelis tigris: Squamata, Teiidae)

“…In late Miocene-early Pliocene, headwater erosion and basin 'spillover' forged a connection between the river and the Gulf of California via the Salton Trough (Dorsey et al, 2018;Nicholson et al, 2019). The Gila River system, which had previously drained directly into the Gulf (Eberly & Stanley, 1978) was similarly incorporated.…”

The geoengineering approach to the study of rivers and reservoirs

“…In this section a number of studies on modern systems (Blum 2019;Sinclair et al 2016;Nicholson et al 2019) are compared with ancient counterparts, from the Cenozoic (Stow et al 2016) and Mesozoic (Dal' Bó et al 2018;Yeste et al 2018;Fambrini et al 2019) through to the Paleozoic (Reesink 2016;Ellen et al 2018). In reconciling these two timescales, it is necessary to find common ground between studies which focus on the plan-view (topdown) evolution of fluvial systems (often the focus of modern studies) and the cross-sectional view often employed by studies of ancient relict landforms in the geological record.…”

“…The Colorado River in the SW USA is one of the Earth's few continental-scale rivers with an active margin delta (Nicholson et al 2019). Deformation along this transform margin, as well as associated intra-plate strain, has resulted in significant changes in sediment routing from the continental interior and post-depositional translation of older deltaic units.…”

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

“…In the latest Miocene and Early Pliocene, the FCVB was located directly west of this entry point [2]. Because of this, the basin contains the most complete record of early ancestral Colorado River sedimentation anywhere in California [3][4][5][6][7][8][9]. This sedimentary record is important for the geological history of the western cordillera, representing the first sedimentation from the elevated Colorado Plateau to reach the Pacific margin [2,10].…”