SEARCH · Search USGS

Results for “The Holocene”

Search indexed USGS publications on groundwater, aquifers, geologic maps, mineral resources and earthquakes. Explore source records by subject and place.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 775 records · Page 43Linked to original sources

USGS2007

Field and laboratory data From an earthquake history study of scarps of the Lake Creek-Boundary Creek fault between the Elwha River and Siebert Creek, Clallam County, Washington

Fault scarps recently discovered on Airborne Laser Swath Mapping (ALSM; also known as LiDAR) imagery show Holocene movement on the Lake Creek–Boundary Creek fault on the north flank of the Olympic Mountains of northwestern Washington State. Such recent movement suggests the fault is a potential source of large earthquakes. As part of the effort to assess seismic hazard in the Puget Sound region, we map scarps on ALSM imagery and show primary field and laboratory data from backhoe trenches across scarps that are being used to develop a latest Pleistocene and Holocene history of large earthquakes on the fault. Although some scarp segments 0.5–2 km long along the fault are remarkably straight and distinct on shaded ASLM imagery, most scarps displace the ground surface <1 m, and, therefore, are difficult to locate in dense brush and forest. We are confident of a surface-faulting or folding origin and a latest Pleistocene to Holocene age only for scarps between Lake Aldwell and the easternmost fork of Siebert Creek, a distance of 22 km. Stratigraphy in five trenches at four sites help determine the history of surface-deforming earthquakes since glacier recession and alluvial deposition 11–17 ka. Although the trend and plunge of indicators of fault slip were measured only in the weathered basalt exposed in one trench, upward-splaying fault patterns and inconsistent displacement of successive beds along faults in three of the five trenches suggest significant lateral as well as vertical slip during the surface-faulting or folding earthquakes that produced the scarps. Radiocarbon ages on fragments of wood charcoal from two wedges of scarp-derived colluvium in a graben-fault trench suggest two surface-faulting earthquakes between 2,000 and 700 years ago. The three youngest of nine radiocarbon ages on charcoal fragments from probable scarp-derived colluvum in a fold-scarp trench 1.2 km to the west suggest a possible earlier surface-faulting earthquake less than 5,000 years ago.

Washington↗

USGS2007

Geologic map of the Craters of the Moon 30' x 60' Quadrangle, Idaho

The Craters of the Moon 30 x 60 minute quadrangle shows the geology of the northern two-thirds of the Craters of the Moon (COM) lava field and volcanic structures of the northern and central parts of the Great Rift volcanic rift zone. The COM lava field is the largest, predominantly Holocene lava field in the conterminous United States. The northwest corner of the map shows older sedimentary, intrusive, and volcanic rocks that range in age from Ordovician to Miocene. These rocks provide evidence of compressional fold and thrust events of the Antler and Sevier orogenies. Compression was followed by voluminous volcanism represented by the Challis Volcanic Group. Basin-and-Range faulting followed in Neogene time. The COM lava field covers about 1,600 square kilometers and contains about 30 cubic kilometers of lava flows and associated vent deposits. Stratigraphic relationships, paleomagnetic studies, and radiocarbon ages indicate that the field formed during eight eruptive periods designated as H, the oldest, to A, the youngest. Each eruptive period was several hundred years or less in duration and separated from other eruptive periods by non-eruptive recurrence intervals of several hundred to about 3,000 years. The first eruptive period began about 15,000 carbon-14 years ago and the latest one ended about 2,100 carbon-14 years ago. All available field, paleomagnetic, radiocarbon, and argon-40/argon-39 data are incorporated in this map and they quantitatively refine the volcanic and paleomagnetic history of the pre-Holocene lava fields and the COM lava field. In a sense, these data determine the 'pulse rate' for Pleistocene and Holocene basaltic volcanism in the area of this map. Twenty-three new argon-40/argon-39 geochronologic data reveal a fairly complete and continuous record of basaltic volcanism in the Craters of the Moon 30 x 60 minute quadrangle for the last 500 ka. The ages cluster into age groupings at ~30 ka, 50-70 ka, 100-125 ka, 260-290 ka, 320-340 ka, and 475 ka. There are apparent periods of ~30 to 60 ka duration when little or no volcanic activity took place between groups. Magnetic polarity and remanent inclination and declination directions for most lava flows in the quadrangle have normal magnetic polarity; they were emplaced during the Brunhes Normal Polarity Chron and are younger than 780,000 years. Directions of remanent magnetization and the new argon-40/argon-39 ages were used to correlate and approximately date lava flows and lava fields for this map.

Scientific Investigations Map↗

USGS2018

Geologic map of the north half of the Lake Walcott 30'×60' quadrangle, Idaho

The geologic map of the northern half of the Lake Walcott 30ʹ×60ʹ quadrangle shows the volcanic geology of the southern part of the Craters of the Moon lava field, the complex geologic features of the Holocene Kings Bowl and Wapi lava fields, and the southern part of the Great Rift volcanic rift zone. The long extent and distribution of skylights in lava-tube systems of the Horse Butte and Wapi Park lava fields are depicted on this map. 40 Ar/ 39 Ar and K/Ar age determinations give detail to the Holocene, late Pleistocene, and late middle Pleistocene volcanic lava fields in this quadrangle. Most of the younger basalt eruptions (less than 150 thousand years [ka]) have occurred along the Great Rift volcanic rift zone, but two of the younger lava fields are located in the western part of the quadrangle. Kimama Butte, a shield volcano, is 87±11 ka, and Shale Butte is dated at 11±6 ka. Paleomagnetic studies have shown that the Horse Butte-Inferno Chasm eruptive fissure system has at least five paleomagnetic-correlative lava fields, the Claasen vent complex consists of at least seven correlative lava fields, and the Streifling-Flat Top vent complex includes at least four correlative lava fields. This map provides geologic, geochronologic, and paleomagnetic data for Holocene lava fields along the southern part of the Great Rift, and for late Pleistocene and late middle Pleistocene lava fields in the central and western parts of the quadrangle. These data can contribute to wise management and preservation of the Craters of the Moon National Monument and for broad-scale understanding of the basaltic-volcanic evolution of the eastern Snake River Plain.

Idaho↗

USGS2020

Geologic map of the northern Harrat Rahat volcanic field, Kingdom of Saudi Arabia

Harrat Rahat, in the west-central part of the Kingdom of Saudi Arabia, is the largest of 15 Cenozoic harrats (Arabic for “volcanic field”) distributed on the Arabian plate. It extends more than 300 km north-south and 50 to 75 km east-west, and it covers an area of approximately 20,000 km 2 , has a volume of approximately 2,000 km 3 , and encompasses more than 900 observable vents. Volcanism commenced around 10 Ma and has continued into historic time, the most recent eruption occurring in 1256 C.E. Volcanic products are dominated by alkali basalt and hawaiite lava flows, with subordinate mugearite lava flows, as well as benmoreite and trachyte lava flows, domes, and pyroclastic flows. This geologic map distinguishes 239 eruptive units that cover an area of 3,340 km 2 in northern Harrat Rahat and the adjacent city of Al-Madinah. Results are presented as a geologic map of the study area at 1:75,000 scale and of smaller regions of particular interest at 1:25,000 scale, along with interpretive text. Most units are basaltic lava flows that erupted from the broadly north-northwest-trending main vent axis that constructed the topographic crest of the volcanic field. This 300- to 400-m-high vent axis, which has a width of 6 to 10 km, lies in the eastern one-third of northern Harrat Rahat. Basalt and hawaiite lava flows can extend as far as 27 km from their vents, but most are 10 to 15 km long. Evolved products such as mugearites, benmoreites, and trachytes are less extensive; the trachytic pyroclastic flows extend as far as 9 km from their source vents, although most only reach 4 to 6 km. Vents of the evolved products are restricted to the main vent axis or its flanks. No volcanic rocks older than 1.2 Ma are exposed in the map area, and about 90 percent of the exposed volcanic rocks erupted during the past 570 thousand years. As depicted on the geologic maps, eruption ages and field relations define 12 eruptive stages for northern Harrat Rahat for the past 1.2 million years. Other important geochronological findings include (1) several late Pleistocene lava flows near Al-Madinah, which previously were interpreted as Holocene from archeological evidence; (2) the eruption age of a cluster of cinder cones and small lava flows in the western outskirts of Al-Madinah (previously ascribed to an eruption in 641 C.E.) is actually 13.3±1.9 ka, close to the Pleistocene-Holocene boundary; and (3) only two Holocene eruptions have been identified in the map area, those of the historically described basalt of Al Labah in 1256 C.E. and the dome and pyroclastic flows of the trachyte of Um Rgaibah at 4.2±5.2 ka.

Scientific Investigations Map↗

USGS2025

Surficial geology and Quaternary tectonics of the Madison Valley and fault zone, Madison, Gallatin, and Beaverhead Counties, southwest Montana

The north-northwest-striking Madison fault is approximately 95 kilometers in length, lying at the confluence of the northeastern Basin and Range province and the Yellowstone tectonic parabola. The fault zone consists primarily of west-dipping normal faults that have east-dipping antithetic faults, which create the Madison Valley graben and several northeast-trending intrabasin faults. The Madison fault and associated sections discussed herein refer to the main west-dipping, range-bounding fault along the eastern side of the valley. Detailed geologic mapping (1:12,000 scale) of the entire fault zone and fault scarp profiling (total of 102 profiles) of the Madison fault reveal greater late Quaternary paleoseismic activity towards the south, including at least three paleoevents along the southern part of the fault that postdate Pinedale glaciation. Early to middle Holocene alluvial fans have vertical surface offsets that average between 2.0 and 3.0 meters and define the characteristic single-event surface offset. Pinedale lateral moraines have vertical surface offsets as great as 12.0 meters. Late Pleistocene to Holocene multiple-event fault scarps show little evidence of beveling, suggesting short seismic recurrence intervals and potential late Pleistocene and Holocene temporal clustering. Long-term average tectonic activity rates indicate slip rates ranging from 0.18–0.6 millimeters per year. Based on a comparison of fault-scarp height versus maximum slope angle of known regression lines developed from other paleoseismic investigations, the most recent event ranges from 5–1 ka. The northern section of the fault zone is defined by multiple normal faults, which detached the hanging walls of Laramide thrust faults within the Paleozoic and Mesozoic strata. This resulted in the partitioning of extension along multiple preexisting structures and less displacement along individual normal fault strands. Structural controls on lateral propagation of individual paleoevents involve the position of lateral ramps along preexisting Laramide contractional faults. This resulted in greater displacement within the larger basement-cored structures along the southern section of the fault zone, where extension is accommodated by one inferred principal basement-involved normal fault. Inferred east-northeast trending, intrabasin, normal faults within the southern half of the fault zone have no late Pleistocene displacement.

Idaho, Montana, Wyoming↗

USGS2025

Map of topographic lineaments interpreted as recent surface ruptures along the Bennett Valley and Southern Maacama Fault Zones, Sonoma County, California

This study documents lidar-illuminated topographic lineaments interpreted as evidence of recent surface fault ruptures and surface ruptures related to distributed deformation along the Bennett Valley Fault Zone and the southernmost Maacama Fault Zone in the northern San Francisco Bay area (fig. 1, on map sheet). Together, these fault zones form a structural connection across a right stepover between the main Maacama Fault Zone and the Rodgers Creek Fault, overlapping principal strands of the San Andreas plate boundary system north of San Francisco Bay (figs. 1, 2, on map sheet) that accommodate about a quarter of the ~40 millimeters per year of regional dextral tectonic slip (Parsons and others, 2013). Although much of the Bennett Valley Fault Zone is seismically active (McLaughlin and others, 2012; Sowers and others, 2010), only the north end of the fault zone (the “Spring Valley strand,” indicated on southern map panel of map sheet and labeled “D” in figure 2, on map sheet) was previously known to have youthful geomorphic expression and to displace Holocene deposits (McLaughlin and others, 2008; Sowers and others, 2010; Sowers and others, 2016). Holocene activity along the length of the Bennett Valley Fault Zone and southernmost Maacama Fault Zone, with possible implications for rupture propagation, continuity, and slip transfer, had not been identified. However, fault splays that project eastward from the Rodgers Creek Fault have been mapped and hypothesized to accommodate slip transfer to the Bennett Valley Fault Zone (Hecker and Randolph Loar, 2018). The generally subtle and distributed nature of surface-rupture evidence along the Bennett Valley and southernmost Maacama Fault Zones, and extensive vegetation cover, had left recent faulting previously unmapped along most of the zone. The map presented here represents a new compilation of inferred surface-rupture features detected using high-resolution topographic lidar data from an airborne lidar survey of Sonoma County, California (OpenTopography, 2014). These data, which enable subtle topographic features to be discerned, indicate that recent (likely Holocene) surface ruptures extend throughout the Bennett Valley and southernmost Maacama Fault Zones. The rupture-lineament map was created using a GIS (geographic information system) framework and is included herein as an image map at a scale of 1:36,000 and as digital datasets (included as supplemental information to this report). The mapping is intended to lay the groundwork for future studies designed to better characterize how plate-boundary slip is accommodated on this important and complex system of faults.

California↗

USGS2003

An index of ecological integrity for the Mississippi alluvial plain ecoregion: index development and relations to selected landscape variables

Macroinvertebrate community, fish community, water-quality, and habitat data collected from 36 sites in the Mississippi Alluvial Plain Ecoregion during 1996-98 by the U.S. Geological Survey were considered for a multimetric test of ecological integrity. Test metrics were correlated to site scores of a Detrended Correspondence Analysis of the fish community (the biological community that was the most statistically significant for indicating ecological conditions in the ecoregion) and six metrics--four fish metrics, one chemical metric (total ammonia plus organic nitrogen) and one physical metric (turbidity)--having the highest correlations were selected for the index. Index results indicate that sites in the northern half of the study unit (in Arkansas and Missouri) were less degraded than sites in the southern half of the study unit (in Louisiana and Mississippi). Of 148 landscape variables evaluated, the percentage of Holocene deposits and cotton insecticide rates had the highest correlations to index of ecological integrity results. sites having the highest (best) index scores had the lowest percentages of Holocene deposits and the lowest cotton insecticide use rates, indicating that factors relating to the amount of Holocene deposits and cotton insecticide use rates partially explain differences in ecological conditions throughout the Mississippi Alluvial Plain Ecoregion.

Arkansas, Kentucky, Louisiana, Mississippi, Missou↗

USGS1973

Geology and quality of water in the Modesto-Merced area, San Joaquin Valley, California, with a brief section on hydrology

The Modesto-Merced area includes about 1,800 square miles on the northeast side of the San Joaquin Valley. The physiographic units in the area are (1) Sierra Nevada, (2) dissected uplands, (3) low alluvial plains and fans, (4) river flood plains and channels, and (5) overflow lands. Geologic units consist of consolidated rocks and unconsolidated deposits. The dominant structure of the geologic units is that of a homocline, which reflects the southwestward-tilted fault block of the Sierra Nevada. The consolidated rocks include: (1) basement complex (pre-Tertiary), (2) marine sandstone and shale (Cretaceous), (3) Ione Formation and other sedimentary rocks (Eocene), (4) Valley Springs Formation (late? Miocene), and (5) the Mehrten Formation (Miocene and Pliocene). In the eastern part of the area, the consolidated rocks generally yield small quantities of water to wells except for the Mehrten Formation which is an important aquifer. The unconsolidated deposits include: (1) continental deposits (Pliocene and Pleistocene?), (2) lacustrine and marsh deposits (Pleistocene), (3) older alluvium (Pleistocene and Holocene?), (4) younger alluvium (Holocene), and (5) flood-basin deposits (Holocene). The continental deposits and older alluvium are the main water-yielding units in the unconsolidated deposits. The lacustrine and marsh deposits (E-clay) and the flood-basin deposits yield little water to wells, and the younger alluvium in most places probably yields only moderate quantities of water to wells. There are three ground-water bodies in the Modesto-Merced area: (1) the unconfined water body, (2) the confined water body, and (3) the water body in consolidated rocks. The unconfined water body occurs in the unconsolidated deposits above and east of the E-clay, except in the western and southern parts of the area where clay lenses occur and semiconfined conditions exist. The confined water body occurs in the unconsolidated deposits below the E-clay and extends downward to the base of fresh water. The water body in consolidated rocks occurs under both perched and confined conditions. Ground-water movement in the unconfined and the confined water bodies is generally westward toward the valley trough. In the unconfined water body, the water also moves toward the major rivers, and toward pumping depressions at Modesto and near El Nido. Because of the higher head in the unconfined water body, water slowly moves from it through the E-clay to the underlying confined water body. Surface water is used extensively for irrigation in most of the study area; consequently, shallow water in the unconfined water body has to be controlled by pumping. Nevertheless, water levels near Modesto declined about 6 feet between 1958 and 1962, for the most part during the dry years 1959-61. Near El Nido, water levels declined about 70 feet between 1942 and 1967. In the confined water body, water levels were high in the winter and spring and low in the summer and fall, reflecting irrigation practices. In the southwestern part of the area, water levels in the confined water body declined about 14 feet from 1962 to 1968 and rose slightly after 1968, whereas in the northwestern part water levels remained fairly constant. Water from the upper reaches of the Stanislaus, Tuolumne, Merced, and Chowchilla Rivers is calcium bicarbonate in chemical type and is of excellent quality. As those rivers cross the valley floor, their water quality is generally degraded by return flows from irrigated land, and in the Tuolumne River by saline water discharged from abandoned gas wells. Average dissolvedsolids content in the major rivers, as indicated by chemical analyses, do not exceed 400 mg/1 (milligrams per liter) except in the San Joaquin River where average dissolved-solids content has not exceeded 1,050 mg/l. Water from minor streams in the area is bicarbonate in chemical type with dissolved-solids content ranging from 56 mg/1 to about 350 mg/l. Although chloride-type fresh ground water occurs in the unconfined and confined water bodies and in the water body in consolidated rocks, most of the fresh ground water is a bicarbonate type that has a dissolved-solids content of less than 500 mg/l. Water having dissolved solids in excess of about 2,000 mg/1 is considered to be saline. Saline water extends below the base of fresh water to the basement complex and, except in the extreme eastern part, underlies most of the study area. Saline water also occurs as lenses above the base of fresh water in the unconfined and confined water bodies.

California↗

USGS1981

Geohydrologic reconnaissance of the Crofton Unit, northeastern Nebraska

This report describes the results of a reconnaissance of the sources, location, quantity, and quality of ground water in the proposed irrigation project area called the "Crofton Unit," an area of approximately 350 square miles in northeastern Nebraska. Precambrian Sioux Quartzite underlies the entire study area. Throughout most of the area, the Sioux is overlain by undifferentiated Paleozoic rocks. The Sioux and, where present, the Paleozoic rocks are overlain unconformably by Cretaceous formations, including both the Dakota and Niobrara Formations. Surface strata are Pleistocene and Holocene deposits of sand and gravel and Pleistocene deposits of glacial till. The Dakota and Niobrara Formations are each capable of yielding sufficient water for irrigation in parts of the area. Pleistocene and Holocene deposits yield adequate water for irrigation in the southern part of the area where saturated thicknesses range from 25 to 176 feet and along the flood plain of the Missouri River where saturated thicknesses range from 40 to 101 feet. Reported yields of 13 Pleistocene irrigation wells sampled for water-quality analyses averaged 857 gallons per minute. Water from wells developed in the Dakota Formation is a calcium sulfate type. Use of this water for successful long-term irrigation would necessitate burdensome salinity-control measures because of the salinity of the water. Water from wells developed in the Niobrara Formation is a calcium bicarbonate type and is suitable for irrigation of most crops. Water from wells developed in both Niobrara and Pleistocene deposits generally is a calcium sulfate type and may be used for irrigation of salt-tolerant crops with special measures for salinity control. The quality of water from Pleistocene and Holocene deposits is highly variable. In both the southern part of the area and along the Missouri River, water from these deposits is a calcium bicarbonate type and generally suitable for irrigation.

Nebraska↗

USGS1988

Hydrogeology and predevelopment flow in the Texas Gulf Coast aquifer systems

A multilayered ground-water flow system exists in the Coastal Plain sediments of Texas. The Tertiary and Quaternary clastic deposits have an area! extent of 128,000 square miles onshore and in the Gulf of Mexico. Two distinct aquifer systems are recognized for the sediments, which range in thickness from a few feet to more than 12,000 feet. The older system the Texas coastal uplands aquifer system consists of four aquifers and two confining units in the Wilcox and Claiborne Groups. It is bounded from below by the practically impermeable Midway confining unit or by the top of the geopressured zone. It is bounded from above by the poorly permeable Vicksburg-Jackson confining unit, which separates it from the younger coastal lowlands aquifer system. The coastal lowlands aquifer system consists of five permeable zones and two confining units that range in age from Oligocene to Holocene. The hydrogeologic units of both systems are exposed in bands that parallel the coastline. The units dip and thicken toward the Gulf. Quality of water in the aquifer systems varies greatly, with dissolved solids ranging from a few hundred to more than 200,000 milligrams per liter. A three-dimensional, variable-density digital model was developed to simulate predevelopment flow in the aquifer systems, for which steady-state conditions were assumed. Horizontal hydraulic conductivities of the aquifers and permeable zones in the calibrated model range from 15 feet per day for the middle Wilcox aquifer, to 170 feet per day for the Holocene-upper Pleistocene aquifer. Vertical hydraulic conductivities range from 1 x 10 -5 foot per day for the Vicksburg-Jackson confining unit, to 1 x 10 -2 foot per day for four of the aquifers and permeable zones. The simulated values of transmissivity and leakance are functions of the percent of sand that is present in each model grid block. There is a large range in precipitation across the study area, from about 21 inches per year in the west to about 56 inches per year in the east. Eastward from a line through Corpus Christi and San Antonio, average annual precipitation ranges from about 30 to about 56 inches. A few inches per year reaches the saturated zone in topographically high areas and is discharged in low areas as evapotranspiration, seepage, springflow, and stream base flow. A smaller amount of water flows through the aquifers and permeable zones downdip from the outcrop areas. This flow results in upward or downward leakage into adjacent hydrogeologic units, but is generally upward into overlying units. Westward from the line through Corpus Christi and San Antonio, average annual precipitation ranges from about 30 to about 21 inches. The general pattern of flow in the aquifers and permeable zones is similar to that in the east, but rates of flow are somewhat smaller. In contrast to the east, ground-water discharge in the west is generally not visible. Evapotranspiration is the main mechanism for ground-water discharge, with most ground water being discharged through evapotranspiration by phreatophytes. Simulated discharge and recharge rates in the combined outcrop areas of all units do not exceed 6 inches per year. The large rates occur in small, local topographically low and high areas. The average discharge rate simulated in the outcrops of the units is 0.45 inch per year. The recharge area is considerably smaller than the discharge area, and the average recharge rate over this smaller area is 0.74 inch per year. Total simulated recharge in the outcrop areas is 269 million cubic feet per day, which is offset by an equal amount of discharge in the outcrop areas. The smallest rates of leakage are across the Vicksburg-Jackson confining unit, with downward and upward rates of less than one million cubic feet per day. The greatest rate of leakage is 47 million cubic feet per day upward into the Holocene-upper Pleistocene permeable zone.

Texas↗

USGS1972

Subsurface geology of the late Tertiary and Quaternary water-bearing deposits of the southern part of the San Joaquin Valley, California

The study area, which includes about 5,000 square miles of the southern part of the San Joaquin Valley, is a broad structural trough of mostly interior drainage. The Sierra Nevada on the east is composed of consolidated igneous and metamorphic rocks of pre-Tertiary age. The surface of these rocks slopes 4?-6? southwestward from the foothills and underlies the valley. The Coast Ranges on the west consist mostly of complexly folded and faulted consolidated marine and nonmarine sedimentary rocks of Jurassic, Cretaceous, and Tertiary age, which dip eastward and overlie the basement complex. Unconsolidated deposits, of late Pliocene to Holocene age, blanket the underlying consolidated rocks in the valley and are the source of most of the fresh ground water. The unconsolidated deposits, the subject of this report, are divided into informal stratigraphic units on the basis of source of sediment, environment of deposition, and texture. Flood-basin, lacustrine, and marsh deposits are fine grained and underlie the valley trough. They range in age from late Pliocene to Holocene. These deposits, consisting of nearly impermeable gypsiferous fine sand, silt, and clay, are more than 3,000 feet thick beneath parts of Tulare Lake bed. In other parts of the trough, flood-basin, lacustrine, and marsh deposits branch into clayey or silty clay tongues designated by the letter symbols A to F. Three of these tongues, the E, C, and A clays, lie beneath large areas of the southern part of the valley. The E clay includes the Corcoran Clay Member of the Tulare Formation, the most extensive hydrologic confining layer in the valley. The E clay underlies about 3,500 square miles of bottom land and western slopes. The beds generally are dark-greenish-gray mostly diatomaceous silty clay of Pleistocene age. Marginally, the unit bifurcates into an upper and a lower stratum that contains thin beds of moderately yellowish-brown silt and sand. The E clay is warped into broad, gentle northwesterly trending anticlines and synclines. The C clay, of Pleistocene age, is a fine-grained lacustrine or paludal deposit occurring 220-300 feet beneath Tulare Lake bed and parts of Fresno Slough. The beds consist of bluish-gray silty clay. Structural contours indicate that the C clay has been extensively warped and folded. The A clay of Pleistocene and Holocene (?) age is a fine-grained lacustrine or paludal deposit occurring 10-60 feet beneath Buena Vista, Kern, and Tulare Lake beds, and parts of Fresno Slough. The clay is mainly blue or dark greenish gray, plastic, and highly organic. In some areas the unit is separated into an upper and a lower stratum by several feet of sand. A radiocarbon date of 26,780 ? 600 years was obtained from wood cored 3 feet beneath the clay. Continental deposits are arkosic beds of late Pliocene and Pleistocene (?) age and were derived from the Sierra Nevada, Tehachapi, and San Emigdio Mountains. In places, a reduced-oxidized contact transgresses the deposits derived from the Sierra Nevada. The reduced deposits consist of moderately permeable bluish-green or bluish-gray fine to medium sand, silt, and clay. The oxidized deposits consist mainly of poorly permeable yellowish-brown silt and fine sand. Deposits derived from the Tehachapi and the San Emigdio Mountains consist of poorly to moderately permeable yellowish-brown sand and silt. Continental and alluvial deposits of Tertiary and Quaternary age that were derived from the Coast Ranges consist mainly of poorly to moderately permeable yellowish-brown gravel, sand, silt, and clay. They include the Tulare Formation and overlying alluvial deposits. Alluvium is composed of coarse arkosic deposits derived from the Sierra Nevada, Tehachapi, and San Emigdio Mountains. A reduced-oxidized contact also transgresses the alluvial deposits derived from the Sierra Nevada. The oxidized deposits consist of poorly to highly permeable yellowish-brown gravel, sand, silt, and clay. The reduc

Water Supply Paper↗

USGS2019

Late-Glacial paleoecology of the Middle Susitna Valley, Alaska: Environmental context for human dispersal

We present here the results of multi-proxy analyses (sediment geochemistry, diatoms, and pollen) from sediment cores collected at four lakes in the middle Susitna Valley, Alaska. These lakes form a transect from the tundra to the boreal forest. The retrieved cores span from ~12,000 cal yr BP to the present, with age control provided by radiometric dates and tephra deposits, some of which are newly identified. Results indicate that deglaciation occurred before 12,000 cal yr BP and that by that time, the lakes were deep, productive, and surrounded by shrub tundra. The lake with the highest sampling resolution indicates a brief climatic reversal ~11,500 cal yr BP with decreased diatom-inferred lake level and lowered lake productivity, and reduced shrub presence. During the early to middle Holocene, all of the sedimentary records provide evidence of climatic amelioration with tree expansion and productive lakes. A middle to late Holocene climatic deterioration with reduced trees and a shallower, less productive lake is also indicated. In addition, the prominent Watana tephra at ~4,000 cal yr BP likely reduced lake productivity and affected the vegetation. Even though the region was relatively productive soon after deglaciation, people did not occupy the region until ~11,000 cal yr BP, about 1000 years later, and then only sparsely. By the middle and late Holocene, the region was more densely populated and this shift in human occupancy presumably reflects changes in resource abundance, especially caribou. Whether the Watana ashfall influenced caribou abundance and thus people, is still under investigation, but given the tephra’s effect on vegetation and lake productivity, it seems likely.

Alaska↗

USGS2022

A statistical framework for integrating nonparametric proxy distributions into geological reconstructions of relative sea level

Robust, proxy-based reconstructions of relative sea-level (RSL) change are critical to distinguishing the processes that drive spatial and temporal sea-level variability. The relationships between individual proxies and RSL can be complex and are often poorly represented by traditional methods that assume Gaussian likelihood distributions. We develop a new statistical framework to estimate past RSL change based on nonparametric, empirical modern distributions of proxies in relation to RSL, applying the framework to corals and mangroves as an illustrative example. We validate our model by comparing its skill in reconstructing RSL and rates of change to two previous RSL models using synthetic time-series datasets based on Holocene sea-level data from South Florida. The new framework results in lower bias, better model fit, and greater accuracy and precision than the two previous RSL models. We also perform sensitivity tests using sea-level scenarios based on two periods of interest – meltwater pulses (MWPs) and the Holocene – to analyze the sensitivity of the statistical reconstructions to the quantity and precision of proxy data; we define high-precision indicators, such as mangroves and the reef-crest coral Acropora palmata , with 2 σ vertical uncertainties within ± 3 m and lower-precision indicators, such as Orbicella spp., with 2 σ vertical uncertainties within ± 10 m. For reconstructing rapid rates of change in RSL of up to ∼ 40 m kyr −1 , such as those that may have characterized MWPs during deglacial periods, we find that employing the nonparametric model with 5 to 10 high-precision data points per kiloyear enables us to constrain rates to within ± 3 m kyr −1 (1 σ ). For reconstructing RSL with rates of up to ∼ 15 m kyr −1 , as observed during the Holocene, we conclude that employing the model with 5 to 10 high-precision (or a combination of high- and low-precision) data points per kiloyear enables precise estimates of RSL within ± ∼ "> 2 m (2 σ ) and accurate RSL reconstructions with errors ≲ 0.7 m. Employing the nonparametric model with only lower-precision indicators also produces fairly accurate estimates of RSL with errors ≲ 1.50 m, although with less precision, only constraining RSL to ± ∼ "> 3–4 m (2 σ ). Although the model performs better than previous models in terms of bias, model fit, accuracy, and precision, it is computationally expensive to run because it requires inverting large matrices for every sample. The new model also provides minimal gains over similar models when a large quantity of high-precision data are available. Therefore, we recommend incorporating the nonparametric likelihood distributions when no other information (e.g., reef facies or epibionts indicative of shallow-water environments to refine coral elevational uncertainties) or no high-precision data are available at a location or during a given time period of interest.

Advances in Statistical Climatology, Meteorology a↗

USGS2000

Influence of inner-continental shelf geologic framework on the evolution and behavior of the barrier-island system between Fire Island Inlet and Shinnecock Inlet, Long Island, New York

High-resolution, sea-floor mapping techniques, including sidescan-sonar and subbottom profiling, were used to investigate how the geologic framework of the inner-continental shelf influenced the Holocene evolution and modern behavior of the Fire Island barrier-island system, Long Island, New York. The inner-continental shelf off Long Island is divided into two physiographic provinces by a broad outcrop of Cretaceous coastal-plain strata offshore of Watch Hill; this outcrop was part of a subaerial headland during the Holocene marine transgression. Erosion of the headland during transgression furnished sediment to the inner-continental shelf downdrift to the west. The sediment was, in turn, reworked by oceanographic processes into a series of shoreface-attached sand ridges. The oldest (~1200 yr BP) and most stable part of the barrier-island system is immediately landward of the outcropping coastal-plain strata and thickest sand ridges. East of Watch Hill, Pleistocene sediment either is exposed on the inner-continental shelf or is buried by a veneer of modern reworked sediment. Here the barrier-island system has migrated landward at a faster rate than the segment west of Watch Hill and has been breached by numerous historic inlets. Because the Pleistocene sedimentary deposit is generally of uniform thickness throughout the study area and unconformably overlies the Cretaceous coastal-plain strata, both the Holocene and historical evolution of the Fire Island barrier-island system are controlled by the physiography of this regional unconformity. In particular, the shoreface-connected sand ridges appear to be a significant source of sediment to the western portion of Fire Island. Previous attempts to develop a sediment budget for this coastal system have failed to explain volumetric discrepancies, primarily because poor assumptions were made about the nature of sediment transport in the system. A more realistic sediment budget must include a significantly larger spatial scale, including sediment input from the inner-continental shelf.

New York↗

USGS1982

Microfaunal analysis of late Quaternary deposits of the northern Bering Sea.

Holocene microfaunal associations and distribution patterns define three inner-shelf (1-20m) biofacies in Norton Sound, northern Bering Sea. The Holocene facies relations are the basis for interpreting early Holocene and late Pleistocene environmental conditions in the NE Bering Sea area. Norton Sound cores provide evidence of two marine transgressions and a varying river input.-from Author

Geologie en Mijnbouw↗

USGS1982

Geotechnical characteristics of bottom sediments in the northeastern Bering Sea.

Sediment of Holocene age derived from the Yukon River, consisting dominantly of silty fine sand and sandy silt, covers the bottom of central and western Norton Sound, which is a high energy environment involving extensive ice loading, high waves, and strong bottom currents. The sediment characteristics indicate that it is susceptible to liquefaction during major storms. Substantially finer grained, weak and highly compressible sediment of Holocene age covers eastern Norton Sound and the Port Clarence embayment, which are low energy environments. Pleistocene peaty deposits underlie the Holocene and late Pleistocene deposits in both Norton Sound and Chirikov Basin and are somewhat overconsolidated. The presence of gas indicates high in situ pore pressure and hence low material strength.-from Authors

Geologie en Mijnbouw↗

USGS1990

Geologic map and geothermal assessment of the Mount Adams volcanic field, Cascade Range of southern Washington

More than 60 Quaternary vents make up the basalt-to-rhyodacite Mount Adams volcanic field and have erupted scoriae and lavas with a total volume of >370 km3. The Mount Adams andesite-dacite stratocone itself is a compound edifice that includes the high cone above 2300 m (20-10 ka), remnants of at least two earlier andesite-dacite cones as old as 0.5 Ma, and 7 Holocene flank vents. Four other Holocene vents and tens of vents contemporaneous with Mount Adams are peripheral to the stratocone. All of these vents, including Mount Adams, lie within a N-S eruptive zone 55 km long and 5 km wide. The age of all known Mount Adams silicic products (>100 ka) and the heterogeneous mafic compositions of the summit cone and Holocene lavas make it unlikely that the stratocone is underlain by an upper-crustal reservoir. Rather, the stratocone at the focus is built up of fractionated hybrid magmas that rise from MASH zones (melting-assimilation-storage-homogenization). The pyroclastic core of breccia and scoria at Mount Adams has undergone acid-sulfate leaching and deposition of alunite, kaolinite, silica, gypsum, sulfur, and Fe-oxides and has been a constant source of avalanches and debris flows. Most heat supplied from depth to the fumarolically altered core is dispersed by the high precipitation rate and high permeability of the rubbly lava flows so that a hydrothermal convection pattern is not maintained. Summit-restricted fumaroles are weak and diffuse.

Conference Paper↗

USGS2003

On the preservation of laminated sediments along the western margin of North America

Piston, gravity, and multicores as well as hydrographic data were collected along the Pacific margin of Baja California to reconstruct past variations in the intensity of the oxygen-minimum zone (OMZ). Gravity cores collected from within the OMZ north of 24??N did not contain laminated surface sediments even though bottom water oxygen (BWO) concentrations were close to 5 ??mol/kg. However, many of the cores collected south of 24??N did contain millimeter- to centimeter-scale, brown to black laminations in Holocene and older sediments but not in sediments deposited during the Last Glacial Maximum. In addition to the dark laminations, Holocene sediments in Soledad Basin, silled at 290 m, also contain white coccolith laminae that probably represent individual blooms. Two open margin cores from 430 and 700 m depth that were selected for detailed radiocarbon dating show distinct transitions from bioturbated glacial sediment to laminated Holocene sediment occurring at 12.9 and 11.5 ka, respectively. The transition is delayed and more gradual (11.3-10.0 ka) in another dated core from Soledad Basin. The observations indicate that bottom-water oxygen concentrations dropped below a threshold for the preservation of laminations at different times or that a synchronous hydrographic change left an asynchronous sedimentary imprint due to local factors. With the caveat that laminated sections should therefore not be correlated without independent age control, the pattern of older sequences of laminations along the North American western margin reported by this and previous studies suggests that multiple patterns of regional productivity and ventilation prevailed over the past 60 kyr. Copyright 2003 by the American Geophysical Union.

Paleoceanography↗