Colorado River Sand Research Articles

Using Ostracode Amino Acid D/L Ratios and Microfossil Analysis to Correlate Alluvial Packages along the Lower Colorado River Corridor, with Insight into the Early Pliocene Integration of the Colorado River and the Gulf of California

The lower Colorado River corridor below Grand Canyon developed sometime between ∼5.3 Ma and ∼4.8 Ma, as evidenced by the first appearance of Colorado River-derived sediments of the Bouse Formation in basins along its modern course and the abrupt appearance of distinctive hematite-stained “C-suite” Colorado River sand grains near the base of the Wind Caves member of the Latrania Formation in the Salton Trough. The oldest recognized evidence for a through-flowing Colorado River is the ∼4.5 Ma to ∼3.5 Ma Bullhead Alluvium. Interest and debate focuses on whether a “pre-Bullhead” Colorado River might have first reached the Salton Trough at 5.3 Ma, prior to deposition of some of the Bouse Formation. Fine-grained but undated Colorado River sediments have been recognized on the Yuma Proving Grounds, Arizona, since the 1970s. These sediments have been correlated by some to the Bouse Formation, and thus, would pre-date the Bullhead Alluvium and might provide evidence for the existence of a “pre-Bullhead” Colorado River. In this study, I use the extent of amino acid racemization in ostracode valves and microfossil assemblages to test correlations between the fine-grained sediments on the Yuma Proving Grounds with other independently dated lower Colorado River corridor alluvial packages that were deposited at ∼5 Ma (Bouse Formation) and at ∼75 ka to ∼60 ka (Chemehuevi Formation). The results of this study confidently demonstrate that the fine-grained sediments on the Yuma Proving Grounds are not late Miocene or early Pliocene in age but instead are correlative with the late Pleistocene Chemehuevi Formation. Evidence for a “pre-Bullhead” Colorado River remains elusive.

Punctuated Sediment Discharge during Early Pliocene Birth of the Colorado River: Evidence from Regional Stratigraphy, Sedimentology, and Paleontology

The Colorado River in the southwestern U.S. provides an excellent natural laboratory for studying the origins of a continent-scale river system, because deposits that formed prior to and during river initiation are well exposed in the lower river valley and nearby basinal sink. This paper presents a synthesis of regional stratigraphy, sedimentology, and micropaleontology from the southern Bouse Formation and similar-age deposits in the western Salton Trough, which we use to interpret processes that controlled the birth and early evolution of the Colorado River. The southern Bouse Formation is divided into three laterally persistent members: basal carbonate, siliciclastic, and upper bioclastic members. Basal carbonate accumulated in a tide-dominated marine embayment during a rise of relative sea level between ~6.3 and 5.4Ma, prior to arrival of the Colorado River. The transition to green claystone records initial rapid influx of river water and its distal clay wash load into the subtidal marine embayment at ~5.4–5.3Ma. This was followed by rapid southward progradation of the Colorado River delta, establishment of the earliest through-flowing river, and deposition of river-derived turbidites in the western Salton Trough (Wind Caves paleocanyon) between ~5.3 and 5.1Ma. Early delta progradation was followed by regional shut-down of river sand output between ~5.1 and 4.8Ma that resulted in deposition of marine clay in the Salton Trough, retreat of the delta, and re-flooding of the lower river valley by shallow marine water that deposited the Bouse upper bioclastic member. Resumption of sediment discharge at ~4.8Ma drove massive progradation of fluvial-deltaic deposits back down the river valley into the northern Gulf and Salton Trough.These results provide evidence for a discontinuous, start-stop-start history of sand output during initiation of the Colorado River that is not predicted by existing models for this system. The underlying controls on punctuated sediment discharge are assessed by comparing the depositional chronology to the record of global sea-level change. The lower Colorado River Valley and Salton Trough experienced marine transgression during a gradual fall in global sea level between ~6.3 and 5.5Ma, implicating tectonic subsidence as the main driver of latest Miocene relative sea-level rise. A major fall of global sea level at 5.3Ma outpaced subsidence and drove regional delta progradation, earliest flushing of Colorado River sand into the northern Gulf of California, and erosion of Bouse basal carbonate and siliciclastic members. The lower Colorado River valley was re-flooded by shallow marine waters during smaller changes in global sea level~5.1–4.8Ma, after the river first ran through it, which requires a mechanism to stop delivery of sand to the lower river valley. We propose that tectonically controlled subsidence along the lower Colorado River, upstream of the southern Bouse study area, temporarily trapped sediment and stopped delivery of sand to the lower river valley and northern Gulf of California for ~200–300 kyr. Massive progradation of the fluvial-deltaic system back down the river valley into the Salton Trough starting ~4.8–4.5Ma apparently was driven by a huge increase in sediment discharge that overwhelmed the sediment-storage capacity of sub-basins along the lower river corridor and established the fully integrated river channel network.

Detrital-zircon U-Pb evidence precludes paleo–Colorado River sediment in the exposed Muddy Creek Formation of the Virgin River depression

Only since 5–6 Ma has the Colorado River flowed through the western Grand Canyon into the Grand Wash Trough at the eastern end of Lake Mead. Before then, the river may have flowed through a paleocanyon transiting the Kaibab uplift at a stratigraphic level above the present eastern Grand Canyon to cross the Shivwits Plateau north of the western Grand Canyon and enter the Virgin River drainage, which exits the Colorado Plateau into the Virgin River depression north of Lake Mead. U-Pb age spectra of detrital zircons from Miocene–Pliocene basin fill of the Muddy Creek Formation in the Virgin River depression preclude any paleo–Colorado River sand in Muddy Creek exposures but fail to show that a Miocene paleo–Colorado River never flowed into the Virgin River depression, because all exposed Muddy Creek horizons sampled for detrital zircons postdate ca. 6 Ma. Detrital-zircon populations from available surface collections cannot test for the presence of Colorado River sediment within unexposed lower Muddy Creek or sub–Muddy Creek strata in the subsurface of the Virgin River depression. Alternate scenarios include rejection of paleo–Colorado flow into the Virgin River drainage at any time, or exit of the pre–6 Ma paleo–Colorado River from the upper Virgin paleodrainage toward the northwest into the eastern Great Basin without flowing southwest into the Virgin River depression through the Virgin River gorge, which may be younger than ca. 6 Ma.

Chronology of Miocene–Pliocene deposits at Split Mountain Gorge, Southern California: A record of regional tectonics and Colorado River evolution

Late Miocene to early Pliocene deposits at Split Mountain Gorge, California, preserve a record of basinal response to changes in regional tectonics, paleogeography, and evolution of the Colorado River. The base of the Elephant Trees Formation, magnetostratigraphically dated as 8.1 ± 0.4 Ma, provides the earliest well-dated record of extension in the southwestern Salton Trough. The oldest marine sediments are ca. 6.3 Ma. The nearly synchronous timing of marine incursion in the Salton Trough and northern Gulf of California region supports a model for localization of Pacifi c‐North America plate motion in the Gulf ca. 6 Ma. The fi rst appearance of Colorado River sand at the Miocene-Pliocene boundary (5.33 Ma) suggests rapid propagation of the river to the Salton Trough, and supports a lake-spillover hypothesis for initiation of the lower Colorado River.

Conservation genetics, evolution and distinct population segments of the Mojave fringe-toed lizard, Uma scoparia

Mojave fringe-toed lizards, Uma scoparia, occur only on desert sand dunes and associated mosaics of small sand ramps. Consequently, the distribution is naturally discontinuous and geographically complex. Many populations are vulnerable to local extirpation, and some are now gone. We synthesized genealogical and paleoecological data to explain the geographic relationships among populations of U. scoparia based on mitochondrial DNA sequence data. The species appears to have arisen from a common ancestor with U. notata by a vicariance event, associated with the formation and development of the Lower Colorado River. Within U. scoparia, two major maternal lineages are associated with the development of river drainage systems. The northern lineage is from the Amargosa River. The southerly lineage includes the Mojave River basin, Bristol Trough, Clark's Pass, and Colorado River sand transport systems. The northernmost lineage of U. scoparia, isolated in the vicinity of Plio-Pleistocene Lake Tecopa, has the greatest amount of DNA sequence divergence. The southern populations exhibit little local genetic differentiation. A small population near Red Pass Lake contains haplotypes from both the northern and southern lineages. We define two distinct population segments (DPSs), one associated with the Amargosa River lineage, and the other with Red Pass Dune.

Geochemical indicators of separate sources for eolian sands in the eastern Mojave Desert, California, and western Arizona

Research Article| April 01, 2002 Geochemical indicators of separate sources for eolian sands in the eastern Mojave Desert, California, and western Arizona James R. Zimbelman; James R. Zimbelman 1Center for Earth and Planetary Studies, National Air and Space Museum, Smithsonian Institution, Washington, DC 20560-0315, USA Search for other works by this author on: GSW Google Scholar Steven H. Williams Steven H. Williams 2Biological Sciences Curriculum Study, 5415 Mark Dabling Boulevard, Colorado Springs, Colorado 80918, USA Search for other works by this author on: GSW Google Scholar GSA Bulletin (2002) 114 (4): 490–496. https://doi.org/10.1130/0016-7606(2002)114<0490:GIOSSF>2.0.CO;2 Article history received: 17 Feb 2000 rev-recd: 21 Dec 2000 accepted: 01 May 2001 first online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation James R. Zimbelman, Steven H. Williams; Geochemical indicators of separate sources for eolian sands in the eastern Mojave Desert, California, and western Arizona. GSA Bulletin 2002;; 114 (4): 490–496. doi: https://doi.org/10.1130/0016-7606(2002)114<0490:GIOSSF>2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract Low, stabilized sand dunes cover much of the Cactus and La Posa Plains in western Arizona, near the town of Parker. The provenance of the dunes is not well defined, and it had been hypothesized that they were possibly related to extensive eolian sand deposits in the eastern Mojave Desert of California, on the other side of the Colorado River. Major oxide analyses of bulk sand samples collected from southeastern California and western Arizona show clear chemical differences. The Mojave sands all have SiO2 < 79 wt%, Al2O3 > 10 wt%, and Na2O + K2O > 5 wt%, whereas the Colorado River and Arizona sands have SiO2 > 81 wt%, Al2O3 < 6 wt%, and Na2O + K2O < 4 wt%. These results show that the stabilized dunes near Parker are chemically indistinguishable from Colorado River sands. The chemical differences between the southeastern California sands and the western Arizona sands are supported by X-ray diffraction results that indicate these two sand populations have significant differences in the relative abundance of quartz and feldspar. Our data also indicate a near-source origin for the Mojave sands, whereas the Colorado River and Arizona sands have undergone more prolonged chemical weathering. The major oxide results are consistent with published trace element studies by others that clearly distinguished between mature and immature sands in California and Colorado. The quartz/feldspar ratio may be amenable to measurement by some advanced remote-sensing instruments. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Provenance Investigations Using Magnetic Susceptibility

ABSTRACT In situ outcrop measurement of magnetic susceptibility with a portable hand-held meter is a quick and useful tool in provenance investigations of siliciclastic strata. The volume percent of magnetite in sandstone and granitoid conglomerate clasts can be approximated and related to potential source areas. Two provenance investigations in southern California illustrate this technique. Magnetic-susceptibility measurements of sandstone and granitoid conglomerate clasts in Upper Cretaceous forearc strata of the Cabrillo Formation in San Diego indicate that the source region(s) were dominated by ilmenite-series granitoid rocks similar to those that underlie the eastern part of the mid-Cretaceous Peninsular Ranges batholith (PRB). These data are consistent with recent thermochronologic studies of the batholith and forearc sandstone that document rapid uplift, cooling, and erosion in the eastern part of the batholith at approximately the same time the Cabrillo Formation was deposited. Magnetic susceptibility of sandstone through part of a 6 km-thick section of Neogene rift-related strata in the western Salton Trough clearly record the abrupt arrival in earliest Pliocene time of ancestral Colorado River sediments into the basin. Pre-Colorado River sediments are dominated by local ilmenite-only granitoid source regions of the eastern Peninsular Ranges that contrast with regional magnetite-bearing Colorado River sands. The transition previously has been recognized via painstaking petrographic and micropaleontologic studies. The change in provenance can be recognized in a few minutes in the field using in situ magnetic-susceptibility measurements.

Sand supply to the Algodones dunefield, south‐eastern California, USA

ABSTRACTIn an effort to gain a better understanding of the relationship between climate, sand supply and aeolian sand deposition, an investigation was undertaken in the Algodones dunefield of south‐eastern California to determine: (1) the source of the sand and (2) the mode of sand supply to the Algodones dunefield. Textural, geochemical and mineralogical analyses show that the dune sands were mainly derived from Colorado River sands during episodes when the Colorado River drained west to the Salton Basin instead of south to the Gulf of California. A model is presented which relates episodic aeolian deposition in the Algodones dunefield to the growth of the resulting lake under a persistent, intense north‐westerly wind regime and to subsequent desiccation of the lake following diversion of the Colorado River to the Gulf of California. Late Holocene radiocarbon ages for relict lake shoreline deposits correlate with documented episodes of extreme flooding and increased winter storminess across the south‐western United States. These conditions are likely to have been the cause of intensified north‐westerly winds which coincided with high stands of Lake Cahuilla. Although diversion of the Colorado River to the Salton Basin occurred at least three times during the late Holocene, it is evident that the river did not change its course in response to the majority of the floods. It appears that the critical control on diversion of the river was the difference in gradient between courses leading to the Salton Basin and Gulf of California, which in turn was influenced by fluvial deposition and tectonic activity. Flooding was able to cause diversion of the Colorado River to the Salton Basin only when the difference in gradient between the two courses was relatively small.

Effects of glen canyon dam on colorado river sand deposits used as campsites in grand canyon national park, USA

AbstractGlen Canyon Dam, located on the Colorado River 24km upstream from Grand Canyon National Park, has affected downstream alluvial sand deposits which are used as campsites by recreational boaters. Inventories of campsite numbers and sizes conducted in 1973, 1983 and 1991, and comparison of aerial photograph series taken in 1965, 1973, 1984 and 1990 show that there has been a system‐wide decrease in the number and size of campsites. Campsites are unevenly distributed along the river, and availability is regarded as ‘critical’ along reaches comprising 45% of the river, based on interviews with river guides. During the first 10 years of Glen Canyon Dam operations, at least 30% of all campsites decreased in size. During the next 18 years, between 1973 and 1991, 32% of all campsites decreased in size, and campsite capacity decreased by 44%. High annual dam releases in excess of power plant capacity in 1983 caused a net system‐wide increase in the number of campsites, but decreased campsite capacity in two critical reaches. The ‘benefit’ of sand aggradation due to the 1983 high flow was short‐lived, and by 1991 only a few campsites were larger than they had been in 1973. In contrast, other sites, especially in critical reaches, were eroded by the 1983 high flows and have not recovered in size. Options for future dam management must consider the variable response of campsites to high flows in critical and non‐critical reaches and the duration over which ‘beneficial’ high flow effects persist.

Composition of Holocene Colorado River Sand: An Example of Mixed-Provenance Sand Derived from Multiple Tectonic Elements of the Cordilleran Continental Margin

ABSTRACT The Colorado River and its tributaries drain a complex provenance that includes multiple tectonic elements of the Proterozoic to Phanerozoic Cordilleran margin. In order to provide (1) a more reliable estimate than that reported in the literature for the composition of Holocene Colorado River sand, and (2) a standard for comparison with ancient sandstones that may contain detritus derived from a similar complex provenance, 25 unconsolidated samples were collected along the lower reaches of the Colorado River for detailed petrological examination. Each specimen was artificially consolidated with epoxy, thin sectioned, and stained for feldspar. Each author, utilizing the Gazzi-Dickinson point-count method, counted 400 points per sample; the results from the two point-count operators wer averaged. The average Colorado River sand in our collection is medium-grained, moderately to well sorted, and composed of 66.2%Q, 18.1%F, 14.7%L, and 1.3% miscellaneous grains. Q, on average, is composed of 89% monocrystalline and 11% polycrystalline quartz grains. The average plagioclase-to-total-feldspar ratio is 0.66, and the average unstable-aphanitic-rock-fragment population (L) consists of 6% metamorphic (Lm), 43% volcanic (Lv), 51% sedimentary (Ls), and 1% alterite fragments. On the QFL provenance-discrimination diagram developed by W. R. Dickinson and associates, our point-count data plot entirely within the recycled-orogen field. W. R. Dickinson and colleagues ascribed such provenances to subduction complexes, collision orogens, and foreland uplifts ass ciated with fold-and-thrust belts. Rocks in the Colorado River drainage basin, however, include (1) remnants of Precambrian crystalline rocks which form a part of cratonal North America; (2) miogeoclinal and platformal sequences that developed along the North American continental margin during Paleozoic time; (3) deformed Paleozoic and Mesozoic sedimentary successions that make up the Sevier-Laramide fold-and-thrust belt; (4) Mesozoic and Cenozoic sedimentary fill of the Sevier foreland basin; (5) Cenozoic basement-cored uplifts that formed during the Laramide orogeny; (6) plutonic and volcanic rocks of the Mesozoic and Cenozoic Cordilleran continental-margin magmatic arc; and (7) Cenozoic sedimentary and volcanic rocks associated with extension and dextral shear along the Cordilleran co tinental margin. Thus, the QFL compositions of Holocene sand derived from the Colorado River drainage basin do not fit neatly into the recycled-orogen model proposed by W. R. Dickinson and colleagues. In contrast, on the QmFLt provenance-discrimination diagram also engendered by W. R. Dickinson and associates, 16 samples plot in the mixed-provenance field, and nine specimens plot in the quartzose-recycled or transitional-continental fields. On the LmLvLs diagram formulated by R. V. Ingersoll and C. A. Suczek, our samples plot close to the Lv-Ls join, approximately midway between the fields of magmatic arcs, rifted continental margins, and suture belts, probably as a result of their mixed heritage. Thus, the QmFL SUB>t and LmLvLs diagrams produce results that reflect more accurately, than do the results derived from the QFL provenance-discrimination diagram, the complex multiple tectonic characteristics of the source rocks in the Colorado River drainage basin. Our samples, therefore, represent excellent examples of mixed-provenance sands. Casual use of only the QFL diagram can lead to erroneous interpretations of provenances composed of more than one major tectonic element.

Gold flotation from Colorado River sand with the air-sparged hydrocyclone

Pilot-scale tests indicate that effective concentration of fine gold from Colorado River sands can be achieved by flotation with the air-sparged hydrocyclone. The fine sands (55% −400 mesh and 0.01 opt*) from gravity concentration were processed with a 5-cm air-sparged hydrocyclone (capacity ~1.0 t/h dry solids). Concentrate grades as high as 5.0 opt were produced in a single stage at a recovery of 75%. The separation efficiency was significantly better than that achieved in conventional batch flotation experiments.

Holocene Continental Sedimentation in the Salton Basin, California: A Reconnaissance

The Salton Basin of southern California is roughly triangular. It ranges from 5 to 130 km in width and is 200 km long. The fault-bounded trough has been filling with a complex series of continental clastic deposits in late Pleistocene and Holocene time. The Holocene deposits are estimated to be up to 60 to 100 m thick. Two major sources supply sediment to the basin. The Colorado River, carrying eroded debris from the Colorado Plateau, has intermittently flowed into the southern part of the basin and deposited sand and mud in deltaic and lacustrine facies. Sediment derived from sources at basin margins is deposited in alluvial fans, braided streams, barrier beaches, and lacustrine beds. Sands from both sources have been reworked into extensive aeolian deposits. The lacustrine muds and silts form an extensive central deposit with which all other facies interfinger or are deposited upon. Abrupt facies changes are common. One example is a 60 m vertical sequence of lacustrine muds overlain by coarse alluvial fan deposits upon which a barrier beach is developed. Lateral changes are also sharp; examples are lacustrine muds cut by meandering or braided channels filled with fine to coarse sand and gravel. Sand thicknesses change abruptly due to changes in transport directions and gradients. The sands from the two major source areas are compositionally distinctive. Colorado River sands contain 60 to 70 percent quartz, 2 percent chert, and 20 percent feldspar, whereas most sands that are derived from the basin margins contain 40 to 50 percent quartz, 30 percent feldspar, and 1 percent chert. The remainder in both sand types is made up of clay, rock fragments, detrital carbonates, and heavy minerals. This information is particularly useful in determining the source of aeolian sands. It shows that the Algodones Dunes are derived from Colorado River sands rather than basin margin sources as suggested by other workers. Faunal variations in the lacustrine sediments are related to salinity changes with changes in lake volume. The saline lacustrine fauna is a restricted type and is unlike the marine fauna of the nearby northern Gulf of California.