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USGS1958

Origin of manganese deposits of Busuanga Island, Philippines

The manganese deposits of Busuanga Island, Palawan, are tabular and broadly lenticular bodies which lie conformably within a thick sequence of deformed abort beds. The purpose of this study is to determine the probable mode of origin of the deposits. Similar deposits in other parts of the world have been described by others as products of several different genetic processes. Field and laboratory methods of research were employed in the course of the investigation. Detailed geologic mapping was done on the surface and underground, and many samples of rocks and ores were obtained. Later, intensive study of samples from four typical deposits and from the rooks in the surrounding areas was undertaken, using a variety of laboratory techniques. Microscopic study of thin sections and polished surfaces was supplemented by X-ray and chemical work. More than one hundred X-ray diffraction powder photographs were made to identify minerals, and qualitative chemical studies were made of a number of aamples by use of the X-ray spectrograph. In addition, quantitative chemical analyses were made of certain samples. Finally, published accounts of the occurrence and geological behavior of manganese and silica were consulted to aid in interpretation of the data at hand. Oherty layers in the manganese deposits are lithologically similar to the chart wallrooks and country rook beds. Radiolarian fossils are common in the chart and are also found in some ore specimens. Manganese content of the wallrocks and the country rock beds, however, in essentially nil. The manganese deposits contain mostly psilomelane-type oxides in their near-surface parts, and in the deepest mines this ore grades downward into siliceous protore. In three of the deposits studied, the protore consists mainly of braanite and quartz; in the fourth deposit, hausmannite and the silicate alleghatvite make up the milk of the protore. Some of the protoro is massive, but cherty stones are commonly well layered parallel to the wall rock structure. Grain size is very small, but, like the silica in the chert beds, becomes relatively coarse where the rocks are much deformed. No evidence of large-scale replacement or cross-cutting veins is found in the protores. It is concluded that the original manganiferous deposits were largely non-clastic or oolloidal marine sediments laid down in a reducing environment. The protorea were developed from these beds by processes of diagenesis and low-grade regional metamorphism. The protores were in turn altered to black oxide ore by near-surface agencies during the present erosion cycle. Particular interest is attached to the occurrence of alleghanyite and traces of pyroxmangite and hubnerite(?) in the protorea.

Busuanga Island↗

USGS2012

Empirical relationships among resilience indicators on Micronesian reefs

A process-orientated understanding of ecosystems usually starts with an exploratory analysis of empirical relationships among potential drivers and state variables. While relationships among herbivory, algal cover, and coral recruitment, have been explored in the Caribbean, the nature of such relationships in the Pacific appears to be variable or unclear. Here, we examine potential drivers structuring the benthos and herbivorous fish assemblages of outer-shelf reefs in Micronesia (Palau, Guam and Pohnpei). Surveys were stratified by wave exposure and protection from fishing. High biomass of most herbivores was favoured by high wave exposure. High abundance of large-bodied scarids was associated with low turf abundance, high coral cover, and marine reserves. The remaining herbivores were more abundant in reefs with low coral cover, possibly because space and hence food limitation occur in high-coral-cover reefs. Rugosity had no detectable effect on herbivorous fish abundance once differences in exposure and coral cover were accounted for. At identical depths, high wave exposure was associated with greater volumes (cover × canopy height) of macroalgae and algal turfs, which most likely resulted from high primary productivity driven by flow. In exposed areas, macroalgal cover declined as the acanthurid biomass increased. The volume of algal turfs was negatively associated with coral cover and herbivore biomass. In turn, high coral cover and herbivore biomass are likely to intensify grazing. The density of juvenile corals was variable where macroalgal cover was low but was confined to lower densities where macroalgal cover was high. High coral cover and density of juvenile corals were favoured in sheltered habitats. While a weak positive relationship was found between scarid biomass and juvenile coral density, we hypothesise that high scarid densities may hinder juvenile density through increased corallivory. New hypotheses emerged that will help clarify the role of acanthurids, wave exposure, and corallivory in driving the recovery of Pacific coral communities.

Pohnpei↗

USGS2017

Acetoclastic Methanosaeta are dominant methanogens in organic-rich Antarctic marine sediments

Despite accounting for the majority of sedimentary methane, the physiology and relative abundance of subsurface methanogens remain poorly understood. We combined intact polar lipid and metagenome techniques to better constrain the presence and functions of methanogens within the highly reducing, organic-rich sediments of Antarctica’s Adélie Basin. The assembly of metagenomic sequence data identified phylogenic and functional marker genes of methanogens and generated the first Methanosaeta sp. genome from a deep subsurface sedimentary environment. Based on structural and isotopic measurements, glycerol dialkyl glycerol tetraethers with diglycosyl phosphatidylglycerol head groups were classified as biomarkers for active methanogens. The stable carbon isotope (δ 13 C) values of these biomarkers and the Methanosaeta partial genome suggest that these organisms are acetoclastic methanogens and represent a relatively small (0.2%) but active population. Metagenomic and lipid analyses suggest that Thaumarchaeota and heterotrophic bacteria co-exist with Methanosaeta and together contribute to increasing concentrations and δ 13 C values of dissolved inorganic carbon with depth. This study presents the first functional insights of deep subsurface Methanosaeta organisms and highlights their role in methane production and overall carbon cycling within sedimentary environments.

ISME Journal↗

USGS2024

Mixed-layer kaolinite-montmorillonite from the Yucatan Peninsula, Mexico

Clay beds 1–2 m thick and interbedded with marine limestones probably of early Eocene age are composed of nearly pure mixed-layer kaolinite-montmorillonite. Particle size studies, electron micrographs, X-ray diffraction studies, chemical analyses, cation exchange experiments, DTA, and TGA indicate that clays from three different localities contain roughly equal proportions of randomly interlayered kaolinite and montmorillonite layers. The montmorillonite structural formulas average K 0·2 Na 0·2 Ca 0·2 Mg 0·2 (Al 2·5 Fe 1·0 3+ Mg 0·5 )(Al 0·75 Si 7.25 )O 20+ (OH) 4− , with a deficiency of structural (OH) in either the montmorillonite or kaolinite layers. Nonexchangeable K + indicates that a few layers are mica-like. Crystals are mostly round plates 1/10 to 1/20 µ across. The feature most diagnostic of the mixed-layer character is an X-ray reflection near 8 Å after heating at 300°C. The clays are inferred to have developed by weathering of volcanic ash and subsequent erosion and deposition in protected nearshore basins.

Clays and Clay Minerals↗

USGS1992

Hydrogeology of the Cambrian-Ordovician aquifer system in the northern Midwest, United States with a section on ground-water quality

The Cambrian-Ordovician aquifer system contains the most extensive and continuous aquifers in the northern Midwest of the United States. It is the source of water for many municipalities, industries, and rural water users. Since the beginning of ground-water development from the aquifer system in the late 1800's, hydraulic heads have declined hundreds of feet in the heavily pumped Chicago-Milwaukee area and somewhat less in other metropolitan areas. The U.S. Geological Survey has completed a regional assessment of this aquifer system within a 161,000-square-mile area encompassing northern Illinois, northwestern Indiana, Iowa, southeastern Minnesota, northern Missouri, and Wisconsin. Consolidated sedimentary rocks in the northern Midwest range in age from Precambrian to Cretaceous and crop out in generally concentric, arcuate patterns, dipping away from structural highs (arches) on the Precambrian basement in northern Minnesota and Wisconsin toward structural lows (basins) to the south and east. The sedimentary bedrock is generally overlain by a veneer of glacial drift. Thickness of the sedimentary sequence increases to about 5,000 feet in the Forest City basin of southwestern Iowa and to about 14,000 and more than 15,000 feet in the Illinois and Michigan basins, respectively. Cambrian and Ordovician age rocks, mainly marine sandstone and carbonate rocks, compose much of the sedimentary sequence and form the Cambrian-Ordovician aquifer system. The aquifer system lies on the Precambrian basement, regarded as a regional confining unit. Six hydrogeologic units are defined; they are arranged as alternating pairs of an aquifer and an overlying confining. unit. The units are named using the predominant geologic nomenclature of the upper Mississippi Valley, which includes most of the study area. In the southern quarter of the area, the hydrogeologic units consist of equivalent formations of the Ozark area (mostly carbonate rocks). The uppermost part of the aquifer system is the Maquoketa confining unit, which consists of the Maquoketa Shale and the underlying dolomite and shale of the Galena Dolomite and the Decorah, Platteville, and Glenwood Formations. The underlying St. Peter-Prairie du Chien-Jordan aquifer is an important source of ground water in the western part of the area in Iowa and Minnesota, where the uniform Jordan Sandstone is hydraulically connected to overlying fractured dolomite of the Prairie du Chien Group. The unit is less important in the eastern part of Wisconsin and Illinois because the Jordan Sandstone is absent and the Prairie du Chien Group is thin or absent due to pre-St. Peter Sandstone erosion. Equivalent rocks in northern Missouri-the Roubidoux Formation and the Gasconade and Eminence Dolomites-are mainly carbonate rocks that are somewhat permeable and contain some sandstone. The St. Lawrence and Franconia Formations underlying the St. Peter-Prairie du Chien-Jordan aquifer consist generally of silty and shaly, fine-grained, poorly sorted, and dolomitic sandstones that restrict vertical movement of ground water and form a regional confining unit. In the southern and eastern parts of the area, the Potosi and Derby-Doerun Dolomites and the upper part of the Davis Formation are the equivalent rocks (mainly carbonate rocks). In the east-central part of the area in Illinois and Wisconsin, the Ironton-Galesville aquifer forms the most important aquifer of the Cambrian-Ordovician aquifer system, contributing about one-third of the yield from wells in the aquifer system in the Chicago area. The aquifer terminates to the west, south, and east, where the sandstones grade into less permeable carbonate rocks in central Iowa, central Illinois, and northwestern Indiana, respectively. The underlying Eau Claire Formation and its partial equivalent to the southwest, the Bonneterre Formation, form an important confining unit above the Mount Simon aquifer throughout much of the study area. Siltstone and shale are fairly common in the upper part of the Eau Claire Formation but less so in its northernmost extent in Wisconsin. Dolomite content increases southward and westward, where a middle dolomite facies grades laterally into the Bonneterre in Missouri, southwestern Minnesota, extreme south-central Wisconsin, and possibly in western Iowa. The basal unit in the Cambrian-Ordovician aquifer system, the Mount Simon aquifer, is present throughout the study area, except where it is absent over local highs of the Precambrian basement. It consists primarily of the Mount Simon Sandstone in the north and its equivalent in northern Missouri, the Lamotte Sandstone. The underlying Hinckley Sandstone of Precambrian age is included in Minnesota, as is the overlying Elmhurst Sandstone Member of the Eau Claire Formation in northern Illinois. The aquifer increases greatly in thickness and the water is progressively more saline away from the northern structural highs toward the basins. Much of the movement and discharge of ground water in the northern Midwest occurs in local, unconfined, shallow flow systems within a few miles of points of recharge. The rest of the water is semiconfined or confined in intermediate or regional flow systems within the bedrock, where flow is deeper, slower, and traverses much longer distances from recharge areas to discharge areas. The major areas of recharge to regional confined flow are in northwestern Iowa, southeastern Minnesota, western, southern, and eastern Wisconsin, and northern Illinois. Although the rate of flow is small, significant recharge to the Cambrian-Ordovician aquifer system also occurs as leakage through the Maquoketa confining unit, where the vertical hydraulic gradient is downward. Ground water in much of the confined aquifer system moves laterally from recharge areas toward the major river valleys and Lake Michigan or down dip toward the structural basins. The longest flow paths extend as much as 400 miles from northwestern Iowa southeast toward the Illinois basin or to the Mississippi River and Missouri River valleys near their confluence. Other major confined flow is from eastern Wisconsin toward the Michigan basin and southward flow from northeastern Illinois toward the Illinois basin. Regional ground-water discharge from the aquifer system is mainly diffuse upward leakage from confined aquifers along flow paths toward the structural basins. Very saline water around and brines within the basins restrict regional flow into the basins, forcing ground water to discharge upward. Water in intermediate flow systems discharges upward to the major river valleys. Original heads of more than 100 feet above land surface were recorded in the aquifer system near Lake Michigan in eastern Wisconsin and at Dubuque, Iowa, along the Mississippi River. The Cambrian-Ordovician aquifer system was developed rapidly in the late 1800's after the first deep well was drilled in Chicago in 1864. Many flowing wells were not controlled, which caused water levels in deep wells to decline, and many no longer flowed by the early 1900's. Heads in the aquifers have declined very little in most of the recharge or unconfined areas since ground-water withdrawal began, but major declines have occurred in confined areas. The largest declines in head are at Chicago, Illinois, Milwaukee and Green Bay, Wisconsin, and Mason City, Iowa, where the aquifer system is confined by the Maquoketa confining unit. The composite head in the aquifer system declined more than 900 feet in the deepest cones of depression in the Chicago area from 1864 to 1980 and about 375 feet in the cone at Milwaukee from 1880 to 1980. More than 200 feet of decline has occurred at Mason City. The head declined as much as 440 feet in Green Bay from 1886 to 1957, when the city discontinued use of its deep wells and began using water from Lake Michigan. The largest centers of pumping are in the Chicago and Twin Cities (Minneapolis-St. Paul, Minnesota) metropolitan areas about 180 million gallons per day each in 1980. Pumpage exceeded 10 million gallons per day in only a few other areas in 1980. Ground water in the Cambrian-Ordovician aquifer system in the northern Midwest is characterized by an extreme range of mineralization, but its quality in most of the area is good. The major cations are calcium, magnesium, and sodium, and the major anions are bicarbonate, sulfate, and chloride. Sodium, sulfate, and chloride distributions are closely related to the distribution pattern of dissolved solids but not in the same proportion. Dissolved-solids concentration is generally less than 1,000 milligrams per liter in the recharge areas of Wisconsin, southern Minnesota, northeastern Iowa, and north-central Illinois where the aquifer system crops out or subcrops beneath glacial drift. Ground water there is the Ca-Mg-HC03 type, derived from and identical to that in the overlying glacial drift. In northwestern Iowa and southwestern Minnesota, the water in both the glacial drift and the Cambrian-Ordovician aquifer system is a Ca-Na-S04HC03 type, derived from oxidation of pyrite in the overlying Cretaceous Dakota Formation. Transition to higher dissolved solids in the confined areas commonly is accompanied by increased sulfate concentration and· the occurrence of Ca-Na-S04-type water. Salinity of the ground water increases progressively toward the .basins, where dissolved solids exceed 200,000 milligrams per liter. Saline water is present in the Mount Simon aquifer near Lake Michigan in eastern Wisconsin and northeastern Illinois but occurs in successively younger rocks to the east and south as they dip toward the basins. Similarly, salinity increases down dip in Iowa to the southwest and south; however, regional ground-water flow in Iowa is from northwest to southeast. Much of the ground water in the confined aquifer system is isotopically depleted in 0180 and OD with respect to modern precipitation-an indication that the water originated as precipitation in a much colder climate than the present and probably was derived from recharge of glacial meltwater. On the basis of o34S values for sulfur in sulfate, it is believed that isostatic loading from glacial ice over the Michigan basin reversed the hydraulic gradient to trend westward, opposite from the present gradient, causing saline water in the Michigan basin to discharge westward through the present recharge areas. Natural water-quality problems in the Cambrian-Ordovician aquifer system are mainly the high dissolved-solids concentrations and associated high concentrations of sulfate and chloride, which limit the use of the water for municipal and domestic purposes in much of the confined aquifer system in central and southern Illinois, Indiana, southern and western Iowa, and northern Missouri. Another concern is that radium activity exceeds normal background concentrations of a few picocuries per liter in much of the confined aquifer system in eastern Wisconsin, northeastern Illinois, and central Iowa. Other common problems are high hardness and locally excessive concentrations of iron and hydrogen sulfide.

Iowa, Illinois, Indiana, Michigan, Minnesota, Miss↗

USGS1983

Crustal structure of the northern mississippi embayment and a comparison with other continental rift zones

Previous geological and geophysical investigations have suggested that the Mississippi Embayment is the site of a Late Precambrian continental rift that was reactivated in the Mesozoic. New information on the deep structure of the northern Mississippi Embayment, gained through an extensive seismic refraction survey, supports a rifting hypothesis. The data indicate that the crust of the Mississippi Embayment may be characterized by six primary layers that correspond geologically to unconsolidated Mesozoic and Tertiary sediments (1.8 km/s), Paleozoic carbonate and clastic sedimentary rocks (5.9 km/s), a low-velocity layer of Early Paleozoic sediments (4.9 km/s), crystalline upper crust (6.2 km/s), lower crust (6.6 km/s), modified lower crust (7.3 km/s), and mantle. Average crustal thickness is approximately 41 km. The presence and configuration of the low-velocity layer provide new evidence for rifting in the Mississippi Embayment. The layer lies within the northeast-trending upper-crustal graben reported by Kane et al. (1981), and probably represents marine shales deposited in the graben after rifting. The confirmation and delineation of a 7.3 km/s layer, identified in previous studies, implies that the lower crust has been altered by injection of mantle material. Our results indicate that this layer reaches a maximum thickness in the north-central Embayment and thins gradually to the southeast and northwest, and more rapidly to the southwest along the axis of the graben. The apparent doming of the 7.3 km/s layer in the north-central Embayment suggests that rifting may be the result of a triple junction located in the Reelfoot Basin area. The crustal structure of the Mississippi Embayment is compared to other continental rifts: the Rhinegraben, Limagnegraben, Rio Grande Rift, Gregory Rift, and the Salton Trough. This comparison suggests that alteration of the lower crust is a ubiquitous feature of continental rifts.

Mississippi embayment↗

USGS2020

Genetic diversity, population structure, and historical demography of a highly vagile and human‐impacted seabird in the Pacific Ocean: The red‐tailed tropicbird, Phaethon rubricauda

Many seabird breeding colonies have recovered from heavy anthropogenic disturbance after conservation actions. The widely distributed red‐tailed tropicbird, Phaethon rubricauda , was used as a model species to assess potential anthropogenic impacts on the genetic diversity of breeding colonies in the Pacific Ocean. Cytochrome c oxidase subunit I and control region sequences analyses were conducted across the range of the species in the Pacific Ocean. The study sites were at islands without human‐related disturbance (non‐impacted islands) and with human‐related disturbance (impacted islands). We hypothesized that (i) breeding colonies of the red‐tailed tropicbird on impacted islands have lower genetic diversity compared with colonies on non‐impacted islands, and (ii) breeding colonies of the red‐tailed tropicbird show significant fine and broad‐scale genetic structure across the Pacific Ocean. Bayesian skyline analyses were conducted to infer past changes in population sizes. Genetic diversity was similar between impacted and non‐impacted islands. There was significant broad‐scale genetic structure among colonies separated by over 6,000 km, but a lack of significant fine‐scale genetic structure within Australasia and Hawai'i, although a significant level of differentiation was found within Chile with Φ ST analyses. Skyline analyses showed that effective population sizes remained relatively constant through time, but experienced either a slight decrease or the end of an expansion event through the last 1,000 years. These changes may be related to the arrival of humans on Pacific islands. Impacted islands may have received immigrants from other relatively close islands, buffering the loss of genetic diversity. However, it is also possible that colonies have retained ancestral variation or that a large effective population size coupled with a long generation time (13 years) has prevented the loss of genetic diversity in human‐impacted islands. Future research using higher‐resolution markers is needed to resolve the population genetic structure of the red‐tailed tropicbird in an ecological time‐scale.

Hawaii↗

USGS2017

Habitat suitability models for groundfish in the Gulf of Alaska

Identifying and quantifying the major ecosystem processes that regulate recruitment strength of commercially and ecologically important fish species is a central goal of fisheries management research. In the Gulf of Alaska (GOA) five groundfish species are of particular interest: sablefish ( Anoplopoma fimbria ), Pacific cod ( Gadus macrocephalus ), walleye pollock ( Gadus chalcogrammus ), arrowtooth flounder ( Atheresthes stomias ), and Pacific ocean perch ( Sebastes alutus ). Habitat suitability models (HSM) were developed for the demersal early juvenile stage to inform survival to recruitment for these species, using catch data and seafloor habitat metrics with presence-only models. Regional-scale maps were produced that predict the probability of suitable habitat available in the GOA from settlement through residency in nursery areas. For example, the HSM for sablefish (150–399 mm) described suitable habitat as bathymetrically low-lying areas with low rocky structure within 25–300 m depth. In contrast, the HSM for Pacific ocean perch (50–200 mm) described suitable habitat as bathymetry rises with rocky structure present on north-south facing slopes within 85–270 m depth. These habitat covariates are useful to refine population estimates for North Pacific groundfish species and to inform life stage-specific definitions of Essential Fish Habitat. This application of MaxEnt models should be applicable for species with low occurrence of spatial data in other marine ecosystems globally.

Alaska↗

USGS2024

Shallow faulting and folding beneath south‐central Seattle, Washington State, from land‐based high‐resolution seismic‐reflection imaging

The geologic framework of the Seattle fault zone (SFZ) has been extensively studied, but the structure and fault strand locations in the central portion of the fault zone through the city of Seattle have remained controversial. Much of what is known about the SFZ has come from light detection and ranging (lidar)‐topographic surveys and paleoseismic investigations of fault scarps primarily west of Puget Sound, regional gravity and aeromagnetic modeling, and multiscale marine seismic imaging in waters both west and east of Seattle. We analyze ∼24 km of land‐based P ‐wave seismic‐reflection data that fill in a critical gap in our understanding of the SFZ beneath the urban areas of West Seattle, south‐central Seattle, and Mercer Island. These data image deformed strata in the upper 1 km, including upwarped Tertiary rock and younger sediments. Collectively, these data provide evidence for multiple Quaternary‐active thrust faults, back thrusts, and sub‐basins within the SFZ beneath the city of Seattle. The results indicate that multiple and potentially active back thrusts in the upper ∼500 m extend across the length of the SFZ and the entire urban corridor that may be analogous to those on Bainbridge Island west of Puget Sound.

Washington↗

USGS2007

Geologic Map of the Gold Creek Gold District, Elko County, Nevada

The Gold Creek, Nev. area displays important stratigraphic and structural relationships between Paleozoic and early Tertiary sedimentary strata in an area dominated by large intrusive bodies of Mesozoic age and extensive volcanic fields of middle to late Tertiary age. An autochthonous sequence includes the Cambrian and Proterozoic(?) Prospect Mountain Quartzite and the overlying Cambrian and Ordovician Tennessee Mountain Formation. This autochthon is overlain by three allochthonous plates each composed of a distinctive sequence of strata and having a distinctive internal structure. The structurally lowest plate is composed of the Havallah sequence, locally of Mississippian and Pennsylvanian age, which is folded on north-south trending axes. The next higher plate is composed of somewhat younger Pennsylvanian and Permian strata cut by east-west trending low-angle faults. The highest plate is composed of early Tertiary non-marine sedimentary and igneous rocks folded on varied but mainly north-south trending axes. The question of whether the allochthonous plates were emplaced by contractional or extensional forces is indeterminate from the local evidence. Mineral deposits include gold placers of moderate size and small pockets of base metals, none of which is currently being exploited.

Scientific Investigations Map↗

USGS2000

Map of Distribution of Bottom Sediments on the Continental Shelf, Gulf of Alaska

Introduction The U.S. Geological Survey has a long history of exploring marine geology in the Gulf of Alaska. As part of a cooperative program with other federal and state agencies, the USGS is investigating the relations between ocean-floor geology and benthic marine biohabitats. This bottom sediment map, compiled from published literature will help marine biologists develop an understanding of sea-floor geology in relation to various biological habitats. The pattern of sea-floor sedimentation and bottom morphology in the Gulf of Alaska reflects a complex interplay of regional tectonism, glacial advances and retreats, oceanic and tidal currents, waves, storms, eustatic change, and gravity-driven processes. This map, based on numerous cruises during the period of 1970-1996, shows distribution of bottom sediments in areas of study on the continental shelf. The samples were collected with piston, box, and gravity corers, and grab samplers. The interpretations of sediment distribution are the products of sediment size analyses combined with interpretations of high-resolution seismic reflection profiles. The sea floor was separated into several areas as follows: Cook Inlet -- Hazards studies in this embayment emphasized sediment distribution, sediment dynamics, bedforms, shallow faults, and seafloor stability. Migrating mega-sandwaves, driven by strong tidal currents, influence seabed habitats and stability of the seafloor, especially near pipelines and drilling platforms. The coarseness of the bottom sediment reinforces the influence of the strong tidal currents on the seafloor habitats. Kodiak Shelf -- Tectonic framework studies demonstrate the development of an accretionary wedge as the Pacific Plate underthrusts the Alaskan landmass. Seismic data across the accretionary wedge reveal anomalies indicative of fluid/gas vent sites in this segment of the continental margin. Geologic hazards research shows that movement along numerous shallow faults poses a risk to sea floor structures. Sea-floor sediment on shallow banks is eroded by seasonal wave-generated currents. The winnowing action of the large storm waves results in concentrations of gravel over broad segments of the Kodiak shelf. Northeastern Gulf of Alaska -- Tectonic framework studies demonstrate that rocks of distant origin (Yakutat terrane) are currently attached to and moving with the Pacific Plate, as it collides with and is subducted beneath southern Alaska. This collision process has led to pronounced structural deformation of the continental margin and adjacent southern Alaska. Consequences include rapidly rising mountains and high fluvial and glacial sedimentation rates on the adjacent margin and ocean floor. The northeastern Gulf of Alaska shelf also has concentrations of winnowed (lag) gravel on Tarr Bank and on the outer shelf southeast of Yakutat Bay. Between Kayak Island and Yakutat Bay the outer shelf consists of pebbly mud (diamict). This diamict is a product of glacial marine sedimentation during the Pleistocene and is present today as a relict sediment. A prograding wedge of Holocene sediment consisting of nearshore sand grading seaward into clayey silt and silty clay covers the relict pebbly mud to mid-shelf and beyond. Shelf and slope channel systems transport glacially derived sediment across the continental margin into Surveyor Channel, an abyssal fan and channel system that reaches over 1,000 km to the Aleutian Trench.

Miscellaneous Field Studies Map↗

USGS1982

Cretaceous biostratigraphy in the Wyoming thrust belt.

In the Cretaceous section of the thrust belt, fossils are especially useful for dating and correlating repetitive facies of different ages in structurally complex terrain. The biostratigraphic zonation for the region is based on megafossils (chiefly ammonites) , which permit accurate dating and correlation of outcrop sections, and which have been calibrated with the radiometric time scale for the Western Interior. Molluscan and vertebrate zone fossils are difficult to obtain from the subsurface, however, and ammonites are restricted to rocks of marine origin. Palynomorphs (plant microfossils) have proven to be the most valuable fossils in the subsurface because they can be recovered from drill cuttings. Palynomorphs also are found in both marine and nonmarine rocks and can be used for correlation between facies. Stratigraphic ranges of selected Cretaceous marine and nonmarine palynomorphs in previously designated reference sections in Fossil Basin, Wyoming are correlated with the occurrence of ammonites and other zone fossils in the same sections. These correlations can be related to known isotopic ages, and they contribute to the calibration of palynomorph ranges in the Cretaceous of the Western Interior. -from Authors

Mountain Geologist↗

USGS2012

Invertebrate assemblages in the lower Klamath River, with reference to Manayunkia speciosa

The freshwater polychaete, Manayunkia speciosa Leidy (Canalipalpata Sabellidae), is the intermediate host for two myxozoan pathogens (Ceratomyxa shasta and Parvicapsula minibicornis) that cause substantial mortalities of juvenile salmon in the Pacific Northwest, particularly in the Klamath River below Iron Gate Dam in California. Information on the distribution of M. speciosa in the Klamath River may facilitate targeted control of polychaete populations to disrupt the parasites that affect fish populations. We sampled invertebrate assemblages in the lower Klamath River in the summer and fall of 2005 and 2006 to estimate distribution patterns of M. speciosa and to characterize assemblage structure of invertebrates in reaches where the polychaete was both collected and not collected. The polychaete was most often found in a reach of river extending 100 km downstream from the Shasta River (river km 185-287). The reach in which it was found supported high taxonomic richness of invertebrates and a high abundance of filtering collectors including marine relicts such as sponges, unioinid mussels, and bryozoans. We suggest that the large, stable substrate on which these were found represents primary, optimal habitat for the polychaete, also a marine relict. Reaches above and below the zone where we collected polychaetes showed a general trend of reduced taxonomic richness as distance away from the polychaete zone increased, and also showed differing relative abundances of non-insect taxa and functional feeding groups. Differences in invertebrate assemblages between years were coincident with large differences in water flows. We suggest flows and food resources may play important roles in invertebrate distribution patterns.

California Fish and Game↗

USGS2008

Thermal stability of ladderane lipids as determined by hydrous pyrolysis

Anaerobic ammonium oxidation (anammox) has been recognized as a major process resulting in loss of fixed inorganic nitrogen in the marine environment. Ladderane lipids, membrane lipids unique to anammox bacteria, have been used as markers for the detection of anammox in marine settings. However, the fate of ladderane lipids after sediment burial and maturation is unknown. In this study, anammox bacterial cell material was artificially matured by hydrous pyrolysis at constant temperatures ranging from 120 to 365 ??C for 72 h to study the stability of ladderane lipids during progressive dia- and catagenesis. HPLC-MS/MS analysis revealed that structural alterations of ladderane lipids already occurred at 120 ??C. At temperatures >140 ??C, ladderane lipids were absent and only more thermally stable products could be detected, i.e., ladderane derivatives in which some of the cyclobutane rings were opened. These diagenetic products of ladderane lipids were still detectable up to temperatures of 260 ??C using GC-MS. Thus, ladderane lipids are unlikely to occur in ancient sediments and sedimentary rocks, but specific diagenetic products of ladderane lipids will likely be present in sediments and sedimentary rocks of relatively low maturity (i.e., C31 hopane 22S/(22S + 22R) ratio <0.2 or ????/(???? + ???? + ????) ratio of >0.5). ?? 2008 Elsevier Ltd.

Organic Geochemistry↗

USGS2006

A new probabilistic seismic hazard assessment for greater Tokyo

Tokyo and its outlying cities are home to one-quarter of Japan's 127 million people. Highly destructive earthquakes struck the capital in 1703, 1855 and 1923, the last of which took 105 000 lives. Fuelled by greater Tokyo's rich seismological record, but challenged by its magnificent complexity, our joint Japanese-US group carried out a new study of the capital's earthquake hazards. We used the prehistoric record of great earthquakes preserved by uplifted marine terraces and tsunami deposits (17 M???8 shocks in the past 7000 years), a newly digitized dataset of historical shaking (10 000 observations in the past 400 years), the dense modern seismic network (300 000 earthquakes in the past 30 years), and Japan's GeoNet array (150 GPS vectors in the past 10 years) to reinterpret the tectonic structure, identify active faults and their slip rates and estimate their earthquake frequency. We propose that a dislodged fragment of the Pacific plate is jammed between the Pacific, Philippine Sea and Eurasian plates beneath the Kanto plain on which Tokyo sits. We suggest that the Kanto fragment controls much of Tokyo's seismic behaviour for large earthquakes, including the damaging 1855 M???7.3 Ansei-Edo shock. On the basis of the frequency of earthquakes beneath greater Tokyo, events with magnitude and location similar to the M??? 7.3 Ansei-Edo event have a ca 20% likelihood in an average 30 year period. In contrast, our renewal (time-dependent) probability for the great M??? 7.9 plate boundary shocks such as struck in 1923 and 1703 is 0.5% for the next 30 years, with a time-averaged 30 year probability of ca 10%. The resulting net likelihood for severe shaking (ca 0.9g peak ground acceleration (PGA)) in Tokyo, Kawasaki and Yokohama for the next 30 years is ca 30%. The long historical record in Kanto also affords a rare opportunity to calculate the probability of shaking in an alternative manner exclusively from intensity observations. This approach permits robust estimates for the spatial distribution of expected shaking, even for sites with few observations. The resulting probability of severe shaking is ca 35% in Tokyo, Kawasaki and Yokohama and ca 10% in Chiba for an average 30 year period, in good agreement with our independent estimate, and thus bolstering our view that Tokyo's hazard looms large. Given $1 trillion estimates for the cost of an M???7.3 shock beneath Tokyo, our probability implies a $13 billion annual probable loss. ?? 2006 The Royal Society.

Philosophical Transactions of the Royal Society A:↗

USGS2002

Field guide to geologic excursions in southwestern Utah and adjacent areas of Arizona and Nevada

This field guide contains road logs for field trips planned in conjunction with the 2002 Rocky Mountain Section meeting of the Geological Society of America held at Southern Utah University in Cedar City, Utah. There are a total of eight field trips, covering various locations and topics in southwestern Utah and adjacent areas of Arizona and Nevada. In addition, the field guide contains a road log for a set of Geological Engineering Field Camp Exercises run annually by the University of Missouri at Rolla in and around Cedar City. Two of the field trips address structural aspects of the geology in southwestern Utah and northwestern Arizona; two trips deal with ground water in the region; and along with the Field Camp Exercises, one trip, to the Grand Staircase, is designed specifically for educators. The remaining trips examine the volcanology and mineral resources of a large area in and around the Tusher Mountains in Utah; marine and brackish water strata in the Grand Staircase-Escalante National Monument; and the Pine Valley Mountains, which are cored by what may be the largest known laccolith in the world. The "Three Corners" area of Utah, Arizona, and Nevada is home to truly world-class geology, and I am confident that all of the 2002 Rocky Mountain Section meeting attendees will find a field trip suited to their interests.

Arizona, Nevada, Utah↗

USGS2014

Attenuation and scattering tomography of the deep plumbing system of Mount St. Helens

We present a combined 3-D P wave attenuation, 2-D S coda attenuation, and 3-D S coda scattering tomography model of fluid pathways, feeding systems, and sediments below Mount St. Helens (MSH) volcano between depths of 0 and 18 km. High-scattering and high-attenuation shallow anomalies are indicative of magma and fluid-rich zones within and below the volcanic edifice down to 6 km depth, where a high-scattering body outlines the top of deeper aseismic velocity anomalies. Both the volcanic edifice and these structures induce a combination of strong scattering and attenuation on any seismic wavefield, particularly those recorded on the northern and eastern flanks of the volcanic cone. North of the cone between depths of 0 and 10 km, a low-velocity, high-scattering, and high-attenuation north-south trending trough is attributed to thick piles of Tertiary marine sediments within the St. Helens Seismic Zone. A laterally extended 3-D scattering contrast at depths of 10 to 14 km is related to the boundary between upper and lower crust and caused in our interpretation by the large-scale interaction of the Siletz terrane with the Cascade arc crust. This contrast presents a low-scattering, 4–6 km 2 “hole” under the northeastern flank of the volcano. We infer that this section represents the main path of magma ascent from depths greater than 6 km at MSH, with a small north-east shift in the lower plumbing system of the volcano. We conclude that combinations of different nonstandard tomographic methods, leading toward full-waveform tomography, represent the future of seismic volcano imaging.

Washington↗

USGS2002

Sand wave fields beneath the Loop Current, Gulf of Mexico: Reworking of fan sands

Extensive fields of large barchan-like sand waves and longitudinal sand ribbons have been mapped by deep-towed SeaMARC IA sidescan sonar on part of the middle and lower Mississippi Fan that lies in about 3200 m of water. The area is beneath the strongly flowing Loop Current. The bedforms have not been adequately sampled but probably consist of winnowed siliciclastic-foraminiferal sands. The size (about 200 m from wingtip to wingtip) and shape of the large barchans is consistent with a previously observed peak current speed of 30 cm/s, measured 25 m above the seabed. The types of small-scale bedforms and the scoured surfaces of chemical crusts, seen on nearby bottom photographs, indicate that near-bed currents in excess of 30 cm/s may sometimes occur. At the time of the survey the sand transport direction was to the northwest, in the opposite direction to the Loop Current but consistent with there being a deep boundary current along the foot of the Florida Escarpment. Some reworking of the underlying sandy turbidites and debris flow deposits is apparent on the sidescan sonar records. Reworking by deep-sea currents, resulting in erosion and in deposits characterised by coarsening upwards structures and cross-bedding, is a process that has been proposed for sand found in cores in shallower parts of the Gulf of Mexico. This process is more widespread than hitherto supposed.

Marine Geology↗