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At least 415 records · Page 23Linked to original sources
USGS2021

Latest Quaternary slip rates of the San Bernardino strand of the San Andreas fault, southern California, from Cajon Creek to Badger Canyon

Four new latest Pleistocene slip rates from two sites along the northwestern half of the San Bernardino strand of the San Andreas fault suggest the slip rate decreases southeastward as slip transfers from the Mojave section of the San Andreas fault onto the northern San Jacinto fault zone. At Badger Canyon, offsets coupled with radiocarbon and optically stimulated luminescence (OSL) ages provide three independent slip rates (with 95% confidence intervals): (1) the apex of the oldest dated alluvial fan (~30–28 ka) is right-laterally offset about 300–400 m yielding a slip rate of 13.5 +2.2/-2.5 mm/yr; (2) a terrace riser incised into the northwestern side of this alluvial fan is offset about 280-290 m and was abandoned ~23 ka, yielding a slip rate of 11.9 +0.9/-1.2 mm/yr; and (3) a younger alluvial fan (13-15 ka) has been offset 120–200 m from the same source canyon, yielding a slip rate of 11.8 +4.2/-3.5 mm/yr. These rates are all consistent and result in a preferred, time-averaged rate for the past ~28 ka of 12.8 +5.3/-4.7 mm/yr (95% confidence interval), with an 84% confidence interval of 10-16 mm/yr. At Matthews Ranch, in Pitman Canyon, about 13 km northwest of Badger Canyon, a landslide offset ~ 650 m with a 10Be age of ~47 ka yields a slip rate of 14.5 +9.9/-6.2 mm/yr (95% confidence interval). All of these slip rates for the San Bernardino strand are significantly slower than a previously published rate of 24.5 ± 3.5 mm/yr at the southern end of the Mojave section of the San Andreas fault (Weldon and Sieh, 1985), suggesting that ~12 mm/yr of slip transfers from the Mojave section of the San Andreas fault to the northern San Jacinto fault zone (and other faults) between Lone Pine Canyon and Badger Canyon, with most (if not all) of this slip transfer happening near Cajon Creek. This has been a consistent behavior of the fault for at least the past ~47 ka.

California↗
USGS1993

Glyphidocythere, a new deep marine, paradoxostomatid (Ostracoda) from the Quaternary and recent of the Indo-Pacific

Chapman’s (1910) Pseudocythere funafutiensis from 1924m off Funafuti, western Pacific is redescribed and illustrated together with additional Pleistocene and Recent material from the Coral and Tasman seas. A new paradoxostomatid genus, Glyphidocythere, is described to accommodate it and two other species yet to be formally described from the Banda Sea, eastern Indonesia. The genus is apparently restricted to the marine slope environment of low (less than 20°) southern latitudes. In the Coral and Tasman seas G. funafutiensis occurs within a narrow bathyal depth range (955m to 1754m) coincident with the Antarctic Intermediate Water.

Journal of Micropalaeontology↗
USGS2003

Quaternary sedimentation and subsidence history of Lake Baikal, Siberia, based on seismic stratigraphy and coring

The long, continuous, high-latitude, stratigraphic record of Lake Baikal was deposited in three broad sedimentary environments, defined by high-resolution seismic-reflection and coring methods: (1) turbidite depositional systems, by far the most widespread, characterizing most of the margins and floors of the main basins of the lake, (2) large deltas of major drainages, and (3) tectonically or topographically isolated ridges and banks. Holocene sedimentation rates based on radiocarbon ages vary by more than an order of magnitude among these environments, from less than about 0.03 mm/yr on ridges and banks to more than about 0.3 mm/yr on basin floors. Extrapolating these rates, with a correction for compaction, yields tentative estimates of about 25 and 11 Ma for the inception of rifting in the Central and North basins, respectively, and less than 6 Ma for the 200-m sediment depth on Academician Ridge. The Selenga Delta has the distinctive form of a classic prograding Gilbert-type delta, but its history appears to represent a complex combination of tectonism and sedimentation. The central part of the delta is underlain by prograding, shallow-water sequences, now several hundred meters below the lake surface. These deposits and much of the delta slope are mantled by fine-grained, deep-water, hemipelagic deposits whose base is estimated to be about 650,000 years old. Modern coarse-grained sediment bypasses the delta slope through fault-controlled canyons that feed large, subaqueous fans at the ends of the South and Central basins. These relations, along with abundant other evidence of recent faulting and the great depths of the Central and South basins, suggest that these two rift basins have experienced a period of unusually rapid subsidence over the last 650,000 years, during at least part of which sedimentation has failed to keep pace.

Lake Baikal↗
USGS1992

Lithofacies analysis of colluvial sediments - an aid in interpreting the recent history of Quaternary normal faults in the Basin and Range Province, western United States

Inferring the frequency and magnitude of past earthquakes from the stratigraphy in exposures of normal-faulted sediments is difficult because colluvial lithofacies assemblages adjacent to faults are complex. Similarities in facies assemblages adjacent to young fault scarps in arid to semiarid areas, such as the Basin and Range province, allow lithofacies to be grouped into two genetic architectural elements: debris and wash elements. Upper and lower facies associations can commonly be recognized within each element. A lithofacies code scheme, similar to those used in the analysis of fluvial and glacial lithofacies sequences, provides a concise way of illustrating lithofacies relations in fault exposures. The source lithology of colluvial lithofacies is shown in the code, and soil-horizon symbols can be included. The architecture of lithofacies assemblages near fault scarps in semiarid areas is explained by a model of colluvial sedimentation in response to a single surface faulting event. Analysis of lithofacies assemblages exposed in three trenches across normal faults in the eastern Basin and Range shows how the model can be used to interpret fault histories. Similar facies analysis methods may be useful in interpreting colluvial sequences formed by non-tectonic processes.

Journal of Sedimentary Petrology↗
USGS2001

Physiography and late Quaternary-Holocene processes of Northeastern Gulf of Mexico outer continental shelf off Mississippi and Alabama

High-resolution multibeam mapping of the mid- and outer continental shelf and upper slope off Mississippi and Alabama reveals a complex bathymetry that reflects conditions during the last eustatic rise and the present high stand of sea level. The most prominent bathymetric features are pinnacles and hardgrounds that are scattered throughout the area. These features generally stand <10 m above the surrounding seafloor, cover large areas, and display a variety of morphologies. Almost all the reef pinnacles and hardgrounds have zones of high acoustic backscatter on their summits and on the seafloor immediately adjacent to their southwest walls. In addition, they also have erosional moats on the seafloor to the southwest. Large fields of bedforms are scattered throughout the mapped area. The asymmetries and orientations of the bedforms suggest that they were formed by excursions of the northeast-flowing Loop Current. In contrast, the pervasive ponding of sediment on the northeast sides of bathymetric highs indicates that one of the predominant directions of sediment transport has been to the south and southwest. The shelf break is a zone of numerous landslides of various sizes and complexities. The morphology of several landslide scars indicates that some of the failures occurred recently. One large reef-capped salt dome was mapped in the area, surrounded by a large field of pock-marks. Fields of pockmarks are also scattered on the shelf. The growth and demise of the reefs are related to the fluctuating transgression of eustatic sea level during the last deglaciation. Two episodes of reef drowning are correlated with the increased rates of sea-level rise during documented melt-water pulses; the first occurred from 14.8 to 14.2 ka and the second from 11.8 to 11.2 ka. Rates of sea-level rise exceeded the maximum growth rate of hermatypic corals only during these two intervals since the last glacial maximum and thus drowned the coral communities.

Alabama, Mississippi↗
USGS1981

Synthesis of silicoflagellate stratigraphy for maestrichtian to quaternary marine sediment

Cosmopolitan and low-latitude silicoflagellate distributions determined from Deep Sea Drilling Project cores are synthesized into a sequence of 23 biostratigraphic zones and subzones for tropical and subtropical ocean areas. The stratigraphic relation of major morphologic changes in silicoflagellates from all areas is summarized. Two new Neogene subzones, one new Paleogene subzone, one new species, and one new variety are defined: Dictyocha perlaevis ornata Subzone, Dictyocha neonautica Subzone, Distephanus speculum haliomma Subzone, Dictyocha neonautica Bukry, n. sp., and D. neonautica var. cocosensis Bukry, n. var.

Book chapter↗
USGS1991

Regressive coastal deposits on Quaternary continental shelves: Preservation and legacy

Regressive coastal deposits containing internal downlapping surfaces are common on continental shelves of the world. Through theoretical considerations and evaluation of examples from the literature and our own studies in California and Italy, we have examined the conditions that lead both to the formation and preservation of these deposits. Coastal downlapping deposits form by progradation of coastal and deltaic lithosomes during stable and falling sea level. in addition to the rate and direction of sea-level change, the major controls governing the development of downlapping deposits are sediment availability and shelf morphology (gradient, surface irregularity, and depth of shelf break). Continental margins receiving a large, continuous supply of sediment commonly have vertical stacks of thick, laterally extensive deposits; those fed by relatively small coastal streams may have well-developed shelf-margin deposits if accommodation space was available. in the absence of feeder streams, shelf-margin downlapping deposits can form from locally derived sediment. Regressive coastal deposits are preserved in a variety of settings, but they are least likely to be preserved on broad, low-gradient (coastal plain) shelves, where small drops in relative sea level were accompanied by large seaward shifts of the shoreline. Even on high-gradient tectonic margins, downlapping deposits commonly are not preserved on the midshelf. The process of shoreface erosion during a transgression is efficient at planing off deposits from previous depositional cycles. Where the deposits are thin, the deposit is partially or wholly reworked; where they are thick, the basal part may be preserved. Regressive deposits are most likely to be preserved along the shelf margin, where relatively thick sequences form at or below the position of the lowstand sea level. On many continental shelves, the coarse sandy texture of outer-shelf sediment largely reflects original deposition in a regressive coastal environment during a fall and lowstand of relative sea level.

California↗
USGS2005

Quaternary geomorphology and modern coastal development in response to an inherent geologic framework: An example from Charleston, South Carolina

Coastal landscapes evolve over wide-ranging spatial and temporal scales in response to physical and biological processes that interact with a wide range of variables. To develop better predictive models for these dynamic areas, we must understand the influence of these variables on coastal morphologies and ultimately how they influence coastal processes. This study defines the influence of geologic framework variability on a classic mixed-energy coastline, and establishes four categorical scales of spatial and temporal influence on the coastal system. The near-surface, geologic framework was delineated using high-resolution seismic profiles, shallow vibracores, detailed geomorphic maps, historical shorelines, aerial photographs, and existing studies, and compared to the long- and short-term development of two coastal compartments near Charleston, South Carolina. Although it is clear that the imprint of a mixed-energy tidal and wave signal (basin-scale) dictates formation of drumstick barriers and that immediate responses to wave climate are dramatic, island size, position, and longer-term dynamics are influenced by a series of inherent, complex near-surface stratigraphic geometries. Major near-surface Tertiary geometries influence inlet placement and drainage development (island-scale) through multiple interglacial cycles and overall channel morphology (local-scale). During the modern marine transgression, the halo of ebb-tidal deltas greatly influence inlet region dynamics, while truncated beach ridges and exposed, differentially erodable Cenozoic deposits in the active system influence historical shoreline dynamics and active shoreface morphologies (block-scale). This study concludes that the mixed-energy imprint of wave and tide theories dominates general coastal morphology, but that underlying stratigraphic influences on the coast provide site-specific, long-standing imprints on coastal evolution.

Journal of Coastal Research↗
USGS1989

Development rates of Late Quaternary soils, Silver Lake playa, California

Soils formed on alluvial fan deposits that range in age from about 35 000 to 200 yr BP near Silver Lake playa in the Mojave Desert permit study of the rates of soil development in an arid, hyperthermic climate. Field-described properties of soils were quantified and analyzed using a soil development index that combines properties and horizon thicknesses. We compared the variability in index values from five independent descriptions of the same soil profile with the variability in values from four soils of the same age described by different people. The variability due to description accounts for between 30 and 80% of the total variability (that due to both the soils and description) for the properties described, which emphasizes the need for consistent soil descriptions. Pedogenic CaCO 3 (as indicated by color), pH increase, and dry consistence appear to change with age at linear rates, whereas rubification appears to change at a logarithmic rate. The linear rates are best attributed to the progressive accumulation of CaCO 3 - and salt-rich eolian dust derived from the playa and other more distant sources. The total-texture values of soils on fans older than 10 000 yr BP are similar, which suggests that playas in this area may have been wet enough to restrict the availability of fines from these sources for many thousands of years prior to 10 000 yr BP. Index values for most properties of soils on the lower fans adjacent to the playa increase at faster rates than those of soils of the same age on the upper fans farther from the playa, probably due to the proximity to this local dust source. Equations derived from regressions of soil age and properties can be used to estimate ages of undated, lithologically similar deposits in similar climates and geomorphic settings.

California↗
USGS1980

Results and assessment of uranium series dating of vertebrate fossils from Quaternary alluvium in Colorado

An average uranium-series age of 102,000 ± 14,000 yr for bones from Louviers Alluvium, near Denver, Colorado, is compatible with the inferred geologic age of from 120,000 to 150,000 yr. A uranium-series date of about 190,000 yr for a bone from Slocum Alluvium, near Canon City, Colorado, is consistent with the inferred geologic age of from 150,000 to 260,000 yr. Age determinations for the Broadway Alluvium are inconsistent but its geologic age is considered to be 15,000 to 30,000 yr BP.

Colorado↗