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USGS2012

Demographic population model for American shad: will access to additional habitat upstream of dams increase population sizes?

American shad Alosa sapidissima are in decline in their native range, and modeling possible management scenarios could help guide their restoration. We developed a density-dependent, deterministic, stage-based matrix model to predict the population-level results of transporting American shad to suitable spawning habitat upstream of dams on the Roanoke River, North Carolina and Virginia. We used data on sonic-tagged adult American shad and oxytetracycline-marked American shad fry both above and below dams on the Roanoke River with information from other systems to estimate a starting population size and vital rates. We modeled the adult female population over 30 years under plausible scenarios of adult transport, effective fecundity (egg production), and survival of adults (i.e., to return to spawn the next year) and juveniles (from spawned egg to age 1). We also evaluated the potential effects of increased survival for adults and juveniles. The adult female population size in the Roanoke River was estimated to be 5,224. With no transport, the model predicted a slow population increase over the next 30 years. Predicted population increases were highest when survival was improved during the first year of life. Transport was predicted to benefit the population only if high rates of effective fecundity and juvenile survival could be achieved. Currently, transported adults and young are less likely to successfully out-migrate than individuals below the dams, and the estimated adult population size is much smaller than either of two assumed values of carrying capacity for the lower river; therefore, transport is not predicted to help restore the stock under present conditions. Research on survival rates, density-dependent processes, and the impacts of structures to increase out-migration success would improve evaluation of the potential benefits of access to additional spawning habitat for American shad.

North Carolina, Virginia↗

USGS2008

Phase shift from a coral to a corallimorph-dominated reef associated with a shipwreck on Palmyra atoll

Coral reefs can undergo relatively rapid changes in the dominant biota, a phenomenon referred to as phase shift. Various reasons have been proposed to explain this phenomenon including increased human disturbance, pollution, or changes in coral reef biota that serve a major ecological function such as depletion of grazers. However, pinpointing the actual factors potentially responsible can be problematic. Here we show a phase shift from coral to the corallimorpharian Rhodactis howesii associated with a long line vessel that wrecked in 1991 on an isolated atoll (Palmyra) in the central Pacific Ocean. We documented high densities of R. howesii near the ship that progressively decreased with distance from the ship whereas R. howesii were rare to absent in other parts of the atoll. We also confirmed high densities of R. howesii around several buoys recently installed on the atoll in 2001. This is the first time that a phase shift on a coral leef has been unambiguously associated with man-made structures. This association was made, in part, because of the remoteness of Palmyra and its recent history of minimal human habitation or impact. Phase shifts can have long-term negative ramification for coral reefs, and eradication of organisms responsible for phase shifts in marine ecosystems can be difficult, particularly if such organisms cover a large area. The extensive R. howesii invasion and subsequent loss of coral reef habitat at Palmyra also highlights the importance of rapid removal of shipwrecks on corals reefs to mitigate the potential of reef overgrowth by invasives.

Palmyra Atoll↗

USGS2011

Integrating science and resource management in Tampa Bay, Florida

Tampa Bay is recognized internationally for its remarkable progress towards recovery since it was pronounced "dead" in the late 1970s. Due to significant efforts by local governments, industries and private citizens throughout the watershed, water clarity in Tampa Bay is now equal to what it was in 1950, when population in the watershed was less than one-quarter of what it is today. Seagrass extent has increased by more than 8,000 acres since the mid-1980s, and fish and wildlife populations are increasing. Central to this successful turn-around has been the Tampa Bay resource management community's long-term commitment to development and implementation of strong science-based management strategies. Research institutions and agencies, including Eckerd College, the Florida Wildlife Commission Fish and Wildlife Research Institute, Mote Marine Laboratory, National Oceanic and Atmospheric Administration, the Southwest Florida Water Management District, University of South Florida, U.S. Environmental Protection Agency, U.S. Geological Survey, local and State governments, and private companies contribute significantly to the scientific basis of our understanding of Tampa Bay's structure and ecological function. Resource management agencies, including the Tampa Bay Regional Planning Council's Agency on Bay Management, the Southwest Florida Water Management District's Surface Water Improvement and Management Program, and the Tampa Bay Estuary Program, depend upon this scientific basis to develop and implement regional adaptive management programs. The importance of integrating science with management has become fully recognized by scientists and managers throughout the region, State and Nation. Scientific studies conducted in Tampa Bay over the past 10–15 years are increasingly diverse and complex, and resource management programs reflect our increased knowledge of geology, hydrology and hydrodynamics, ecology and restoration techniques. However, a synthesis of this research and its integration into resource management has not been prepared for Tampa Bay since the mid-1980s. The need for an up-to-date synthesis of Tampa Bay science and management has resulted in the production of this document. The U.S. Geological Survey recently completed a 5-year Tampa Bay Integrated Science Study, and the Tampa Bay Estuary Program updated the Comprehensive Conservation and Management Plan for Tampa Bay in 2006. These efforts build upon results of the many research and management studies and programs summarized here.

Florida↗

USGS2018

Hawai‘i and U.S.-Affiliated Pacific Islands

The U.S. Pacific Islands are culturally and environmentally diverse, treasured by the 1.9 million people who call them home. Pacific islands are particularly vulnerable to climate change impacts due to their exposure and isolation, small size, low elevation (in the case of atolls), and concentration of infrastructure and economy along the coasts. A prevalent cause of year-to-year changes in climate patterns around the globe and in the Pacific Islands region is the El Niño –Southern Oscillation (ENSO). The El Niño and La Niña phases of ENSO can dramatically affect precipitation, air and ocean temperature, sea surface height, storminess, wave size, and trade winds. It is unknown exactly how the timing and intensity of ENSO will continue to change in the coming decades, but recent climate model results suggest a doubling in frequency of both El Niño and La Niña extremes in this century as compared to the 20th century under scenarios with more warming, including the higher scenario (RCP8.5). On islands, all natural sources of freshwater come from rainfall received within their limited land areas. Severe droughts are common, making water shortage one of the most important climate-related risks in the region. As temperature continues to rise and cloud cover decreases in some areas, evaporation is expected to increase, causing both reduced water supply and higher water demand. Streamflow in Hawai‘i has declined over approximately the past 100 years, consistent with observed decreases in rainfall. The impacts of sea level rise in the Pacific include coastal erosion, episodic flooding, permanent inundation, heightened exposure to marine hazards, and saltwater intrusion to surface water and groundwater systems. Sea level rise will disproportionately affect the tropical Pacific and potentially exceed the global average. Invasive species , landscape change, habitat alteration, and reduced resilience have resulted in extinctions and diminished ecosystem function. Inundation of atolls in the coming decades is projected to impact existing on-island ecosystems. Wildlife that relies on coastal habitats will likely also be severely impacted. In Hawaiʻi, coral reefs contribute an estimated $477 million to the local economy every year. Under projected warming of approximately 0.5°F per decade, all nearshore coral reefs in the Hawai‘i and Pacific Islands region will experience annual bleaching before 2050. An ecosystem -based approach to international management of open ocean fisheries in the Pacific that incorporates climate-informed catch limits is expected to produce more realistic future harvest levels and enhance ecosystem resilience. Indigenous communities of the Pacific derive their sense of identity from the islands. Emerging issues for Indigenous communities of the Pacific include the resilience of marine-managed areas and climate-induced human migration from their traditional lands. The rich body of traditional knowledge is place-based and localized and is useful in adaptation planning because it builds on intergenerational sharing of observations. Documenting the kinds of governance structures or decision-making hierarchies created for management of these lands and waters is also important as a learning tool that can be shared with other island communities. Across the region, groups are coming together to minimize damage and disruption from coastal flooding and inundation as well as other climate-related impacts. Social cohesion is already strong in many communities, making it possible to work together to take action. Early intervention can lower economic, environmental, social, and cultural costs and reduce or prevent conflict and displacement from ancestral land and resources.

Report↗

USGS2008

Trace fossils and sedimentary facies from a Late Cambrian‐Early Ordovician tide‐dominated shelf (Santa Rosita Formation, northwest Argentina): Implications for ichnofacies models of shallow marine successions

The Santa Rosita Formation is one the most widely distributed lower Paleozoic units of northwest Argentina. At the Quebrada del Salto Alto section, east of Purmamarca, Jujuy Province, it is represented by four sedimentary facies: thick‐bedded planar cross‐stratified quartzose sandstones (A), thin‐bedded planar cross‐stratified quartzose sandstones and mudstones (B), wave‐rippled sandstones and bioturbated mudstones (C), and black and greenish gray shales (D). Paleocurrent data, sandstone architecture, and sedimentary structures from faciès A and B indicate bipolar/bimodal paleoflows, suggesting the action of tidal currents. The succession is interpreted as that of a tide‐dominated shelf, with only secondary influence of wave processes. Trace fossils are restricted to facies B and C. The Cruziana ichnocoenosis is preserved on the soles of thin‐bedded planar cross‐stratified quartzose sandstones (faciès B). This ichnocoenosis consists of Conostichus isp., Cruziana omanica, C. semiplicata, C. cf. tortworthi, Cruziana isp. Helminthopsis abeli, Monomorphichnus bilinearis, M. multilineatus, Palaeophycus tubularis, Rusophycus carbonarias, R. latus , and R. isp. The occurrence of Cruziana semiplicata , C. omanica, C. cf. tortworthi , and Rusophycus latus supports a Late Cambrian‐Tremadoc age. Slabbing of Cruziana shows complex interactions between biologic and sedimentologic processes, and suggests a predominance of exhumed traces, washed out and recast by tractive sand deposition. Sandstone soles are densely packed with biogenic structures and exhibit distinctive clusters of Rusophycus isp. that most likely represent trilobite nesting burrows. The Cruziana ichnocoenosis records the resident fauna of a protected, lower intertidal to subtidal interbar setting. The Skolithos ichnocoenosis is represented by high to low density vertical burrows of Skolithos linearis , which extend downwards to the quartzose sandstone soles of faciès B and cross the Cruziana ichnocoenosis. The Skolithos ichnocoenosis represents colonization by suspension‐feeding organisms following a major change in environmental conditions, related to the migration of lower intertidal to subtidal sandwaves. The Planolites ichnocoenosis consists exclusively of Planolites montanus within mudstones overlying wave‐rippled sandstones (facies C). The Planolites ichnocoenosis records opportunistic colonization by inf aunal deposit feeders that mined the organic‐rich fine‐grained sediment during the waning phase of storms that scoured organic detritus from the sea bottom. The section records, from base to top, a Cruziana‐Skolithos ichnofacies zone, a Skolithos ichnofacies zone and an unbioturbated zone typified by the thick‐bedded cross‐stratified quartzose sandstone (fades A). This trend reflects progressively higher energy conditions linked to the establishment of a large sand wave complex. The presence of a mixed Cruziana‐Skolithos ichnofacies in the lower interval reflects changes in substrate and energy levels, rather than water depth. Accordingly, contrasting ichnocoenoses from interbars (Cruziana) and sandwaves (Skolithos) must be considered an example of ichnofacies controlled by local parameters instead of general bathymétrie trends. Conversely, the vertical replacement of the Cruziana ichnofacies by the Skolithos ichnofacies towards the middle interval of the section reflects the environmental changes associated with the transition between the intertidal and subtidal zones. As overall tidal energy increases from supratidal to subtidal settings, the Skolithos ichnofacies tends to occur seaward of the Cruziana ichnofacies in tide‐dominated shallow marine environments. Therefore, onshore‐offshore ichnofacies replacement in tide‐dominated shallow seas is opposite to that in wave‐dominated marine settings.

Ichnos: An International Journal for Plant and Ani↗

USGS1984

Wave-formed structures and paleoenvironmental reconstruction

Wave-formed sedimentary structures can be powerful interpretive tools because they reflect not only the velocity and direction of the oscillatory currents, but also the length of the horizontal component of orbital motion and the presence of velocity asymmetry within the flow. Several of these aspects can be related through standard wave theories to combinations of wave dimensions and water depth that have definable natural limits. For a particular grain size, threshold of particle movement and that of conversion from a rippled to flat bed indicate flow-velocity limits. The ratio of ripple spacing to grain size provides an estimate of the length of the near-bottom orbital motion. The degree of velocity asymmetry is related to the asymmetry of the bedforms, though it presently cannot be estimated with confidence. A plot of water depth versus wave height (h-H diagram) provides a convenient approach for showing the combination of wave parameters and water depths capable of generating any particular structure in sand of a given grain size. Natural limits on wave height and inferences or assumptions regarding either water depth or wave period based on geologic evidence allow refinement of the paleoenvironmental reconstruction. The assumptions and the degree of approximation involved in the different techniques impose significant constraints. Inferences based on wave-formed structures are most reliable when they are drawn in the context of other evidence such as the association of sedimentary features or progradational sequences.

Marine Geology↗

USGS2011

Isostatic gravity map of the Point Sur 30' x 60' quadrangle and adjacent areas, California

This isostatic residual gravity map is part of a regional effort to investigate the tectonics and water resources of the central Coast Range. This map serves as a basis for modeling the shape of basins and for determining the location and geometry of faults in the area. Local spatial variations in the Earth's gravity field (after removing variations caused by instrument drift, earth-tides, latitude, elevation, terrain, and deep crustal structure), as expressed by the isostatic anomaly, reflect the distribution of densities in the mid- to upper crust, which in turn can be related to rock type. Steep gradients in the isostatic gravity field often indicate lithologic or structural boundaries. Gravity highs reflect the Mesozoic granitic and Franciscan Complex basement rocks that comprise both the northwest-trending Santa Lucia and Gabilan Ranges, whereas gravity lows in Salinas Valley and the offshore basins reflect the thick accumulations of low-density alluvial and marine sediment. Gravity lows also occur where there are thick deposits of low-density Monterey Formation in the hills southeast of Arroyo Seco (>2 km, Marion, 1986). Within the map area, isostatic residual gravity values range from approximately -60 mGal offshore in the northern part of the Sur basin to approximately 22 mGal in the Santa Lucia Range.

California↗

USGS2000

Geologic map and database of the Salem East and Turner 7.5 minute quadrangles, Marion County, Oregon: A digital database

The Salem East and Turner 7.5-minute quadrangles are situated in the center of the Willamette Valley near the western margin of the Columbia River Basalt Group (CRBG) distribution. The terrain within the area is of low to moderate relief, ranging from about 150 to almost 1,100-ft elevation. Mill Creek flows northward from the Stayton basin (Turner quadrangle) to the northern Willamette Valley (Salem East quadrangle) through a low that dissects the Columbia River basalt that forms the Salem Hills on the west and the Waldo Hills to the east. Approximately eight flows of CRBG form a thickness of up to 700 in these two quadrangles. The Ginkgo intracanyon flow that extends from east to west through the south half of the Turner quadrangle is exposed in the hills along the southeast part of the quadrangle. Previous geologic mapping by Thayer (1939) and Bela (1981) while providing the general geologic framework did not subdivide the CRBG which limited their ability to delineate structural elements. Reconnaissance mapping of the CRBG units in the Willamette Valley indicated that these stratigraphic units could serve as a series of unique reference horizons for identifying post-Miocene folding and faulting (Beeson and others, 1985,1989; Beeson and Tolan, 1990). Crenna, et al. (1994) compiled previous mapping in the Willamette Valley in a study of the tectonics of the Salem area. The major emphasis of this study was to identify and map CRBG units within the Salem East and Turner Quadrangles and to utilize this detailed CRBG stratigraphy to identify and characterize structural features. Water well logs were used to provide better subsurface stratigraphic control. Three other quadrangles (Scotts Mills, Silverton, and Stayton NE) in the Willamette Valley have been mapped in this way (Tolan and Beeson, 1999). This area was a lowland area of weathered and eroded marine sedimentary when the Columbia River basalts encroached on this area approximately 15-16 m.y. ago. An incipient Coast Range apparently stopped or diverted the fluid lava flows from moving much farther westward toward the coast at this latitude. It is assumed also that an ancestral Willamette River flowed northward through this low-lying area so that water was present as streams and ponds along the flood plain.

Oregon↗

USGS1975

Hydrocarbon potential, geologic hazards, and the technology, time-frame and infrastructure for exploration and development of the lower Cook Inlet, Alaska; a preliminary assessment

The Lower Cook Inlet Outer Continental Shelf (OCS) contains 5600 km 2 of submerged land in less than 200 m of water 150 to 350 km southwest of Anchorage, Alaska. This area could contain from 0.3 to 1.4 billion barrels of oil and from 0.6 to 2.7 trillion cubic feet of natural gas depending upon the statistical confidence level indicated. The known geology of this submerged area, is extrapolated to the offshore from onshore data. The sedimentary rocks are as old as Triassic and as young as Pleistocene. The Mesozoic strata include volcanic rocks, volcanoclastic and marine clastic sediments. Tertiary, rocks from which the oil and gas in Upper Cook Inlet are produced, consist of nonmarine conglomerate, sandstone, siltstone and coal. The potential objective section for oil and gas in this OCS area ranges from Middle Jurassic through the Tertiary. The present structural configuration of this area is a northeast trending trough filled with Tertiary sediments. The trough is flanked by two major faults, the Bruin Bay fault on the northwest and the Border Ranges fault on the southeast. Between these faults is the OCS area containing anticlinal structures and faults which may be traps for hydrocarbons. Potential geologic hazards are present in this area. It is an area of intense tectonism expressed as seismic activity (earthquakes) and volcanic eruptions which produce many natural disturbances including tsunamis. This distribution of soft sediment and other submarine features which relate to geologic hazards are only generally known.

Alaska↗

USGS1984

Reconnaissance geology of the Al'Awshaziyah Quadrangle, sheet 26/41 B, Kingdom of Saudi Arabia

The Al 'Awshaziyah quadrangle (26/41 B) is located between lat 26°30' and 27°00 f N. and long 41°30' and 42°00' E. in the northeastern part of the Arabian Shield. The quadrangle contains surficial Quaternary deposits and locally exposed underlying upper Proterozoic intrusive, volcanic, and volcaniclastic rocks. The oldest rocks, gabbro and pyroxenite, are tentatively correlated with the Ha'il mafic-ultramafic complex to the north of the quadrangle. Two younger volcanic sequences, structurally more or less distinct but compositionally transitional, have been identified. The Aqab formation (about 640-610 Ma old) consists of slightly metamorphosed, moderately to strongly folded flows and tuffs of basalt, dacite, and minor rhyolite. An interlayered subaerial conglomerate and a lack of deep-marine sediments distinguish the Aqab from the older and distinctly oceanic Nuf formation. The.Aqab formation is overlain by felsic ash-flow tuffs and related fragmental rocks of the Al 'Awshaziyah formation whose major source is a large caldera in the western part of the quadrangle. Plutonic rocks include granites that predate and postdate both the Aqab and Al 'Awshaziyah formations. The youngest granites, dated at about 580 Ma, are the Salma and Ar Rumman batholiths and are more -alkaline and more silicic than the older granites. The Ar Rumman granite is peralkaline. Even the youngest intrusive rocks have been cut by faults that are probably related to the northwest-trending Najd fault system. No metallic mineralization has been recognized in the quadrangle. A small quarry near the western boundary of the quadrangle produces crushed rock.

Open-File Report↗

USGS2020

Geology and assessment of undiscovered oil and gas resources of the Sverdrup Basin Province, Arctic Canada, 2008

The Sverdrup Basin Province, an area of 515,000 square kilometers on the northern margin of North America, extends 1,300 kilometers across the Canadian Arctic Islands from near the Mackenzie Delta to northern Ellesmere Island. It consists of an intracratonic late Paleozoic to early Cenozoic rift-sag basin and a Mesozoic rift shoulder that bounds it on the north. Basin inception was Mississippian, manifested by deposition of nonmarine strata in rift basins, followed by Pennyslvanian marine transgression, which began with evaporites and progressed to Permian carbonate and clastic deposition at basin fringes and organic-rich marine strata in the basin center. Sediment transport was both northward from North America and southward from a now-subsided or rifted-away landmass to the north. Mesozoic strata indicate continued marine deposition, including both organic-rich, fine-grained rocks deposited during highstands and progradational deltaic sequences. A new episode of rifting began in Middle Jurassic time and culminated in the opening of the Canada Basin by Early Cretaceous seafloor spreading. The Sverdrup Rim formed as the rift shoulder between North America and the thinned, subsided crust to the north. Widespread Upper Cretaceous organic-rich shales were deposited during the major transgression induced by Canada Basin opening, followed by an influx of coarser east-derived detritus. In Paleogene time, incipient North Atlantic seafloor spreading caused deformation in northeasternmost North America, producing uplifts that shed detritus westward across the Sverdrup Basin. Tight folding and thrusting resulting from the Eurekan orogeny took place in the eastern part of the basin during the Eocene, with decreasing intensity of deformation westward. Since deformation ended in late Eocene time, little significant tectonism or deposition has taken place. Two petroleum systems were defined in the Sverdrup Basin Province. Upper Paleozoic marine shale generated petroleum beginning in the Early Triassic, but this petroleum system was not quantitatively assessed because reservoir quality in adjacent strata is poor, the rocks are mostly overmature, and subsequent deformation likely affected trap integrity. The second petroleum system was sourced by Lower Triassic strata rich in oil-prone organic matter. Oil was generated during Paleogene burial synchronous with Eurekan deformation, and the oil migrated into Triassic and Jurassic deltaic, shallow marine and nonmarine strata. However, most of the oil may have escaped during deformation and subsequent uplift and erosion, which probably caused oil to be displaced from traps by gas expansion. The population of undiscovered accumulations was characterized as likely to include stratigraphically trapped and small, structurally trapped accumulations, with a median size of 80 million barrels of oil (MMBO); the number of undiscovered accumulations was estimated to be between 1 and 50, with the most likely number being 10. The resulting estimate of undiscovered, technically recoverable, conventional oil resources is 61 to 1,255 MMBO, with a mean of 427 MMBO. Undiscovered, technically recoverable, conventional gas resources are estimated at 4.95 trillion cubic feet (TCF), with slightly more than half of that in nonassociated gas accumulations. A third petroleum system in the adjacent Amerasia Basin Province to the north was considered somewhat likely to contain accumulations on the Sverdrup Rim. Deeply buried Upper Jurassic, Upper Cretaceous, and Eocene organic-rich strata probably generated oil that may have migrated up the continental slope into Triassic to Paleogene sandstones on the Sverdrup Rim. Based on analogy with the Barrow Arch in Alaska, a median of 20 accumulations was estimated, with accumulation volumes as much as 2,500 MMBO and a median of 100 MMBO. The probability of at least one accumulation of the minimum size assessed (50 MMBO) was estimated at 0.22. The resulting estimate of undiscovered, technically recoverable, conventional oil resources is 0 to 2,679 MMBO, with a mean of 424 MMBO. Mean estimates for associated and nonassociated gas are 1.3 and 2.3 TCF, respectively.

Sverdrup Basin↗

USGS1962

Tuscaloosa formation in Tennessee

Late Cretaceous Tuscaloosa Formation occurs as discontinuous remnants that cap many of the ridges in the Western Highland Rim. Typically the formation consists of well-rounded, poorly sorted chert gravel which is trimodal in size distribution. The gravel fraction (mode 15 to 40+ mm) consists of Devonian and Mississippian chert and a small percentage of sandstone pebbles. The medium sand fraction (mode 0.5 mm) consists mainly of angular to well-rounded chert grains developed by attrition during transport. Well-rounded and frosted quartz grains also are present. The fine fraction (mode 0.15 mm) consists of clay, authi-genic (?) mica, and quartz. At its eastern limit the Tuscaloosa is locally well sorted and contains quartz pebbles and a large proportion of quartz sand. Also present in the same area are well-sorted, heavy-mineral-bearing sands and bimodal (0.04, 0.2 mm) siltstone, which contains sand-sized pellet aggregates and fragmentary plant fossils. The finest fraction (less than 0.044 mm) of both eastern and western facies of the Tuscaloosa consists of 60-80 per cent quartz, 5-30 per cent kaolin, and 5-30 per cent montmorillonite, all of which are present in Devonian and Mississippian bedrock. Minor exotic constituents include volcanic(?) glass and heavy minerals. The Mississippian chert gravel in the Tuscaloosa is of local origin, but the Devonian chert was transported from a western source. Other components from a western source are sandstone pebbles and frosted sand grains, both of which probably were derived from Cambrian or Ordovician formations that cropped out on the Pascola arch, an eastward-sloping extension of the Ozark dome. Quartz pebbles, heavy minerals, and some of the angular quartz sand present at the eastern edge of the Tuscaloosa may have been derived from Pennsylvanian sandstone and conglomerates that cropped out north and south of the Pascola arch. Most of the Tuscaloosa Formation is believed to be of nonmarine origin, deposited on the eastward-sloping flank of the Pascola arch. The eastern facies of the Tuscaloosa is believed to be partly marine in origin, the exotic components having been swept in by longshore currents. During deposition of the Tuscaloosa , the Ozark dome and the Cincinnati arch were connected by the Pascola arch, which is now deeply buried beneath the Mississippi Embayment, At that time the Pascola arch stood structurally about 3000 feet higher than at present, and its structural shape and dimensions were comparable to the present Nashville dome. During deposition of the Tuscaloosa the Nashville dome was structurally about 1000 feet lower than at present, and its crest probably was submerged beneath the sea.

Tennessee↗

USGS2010

Geophysical and sampling data from the inner continental shelf: Northern Cape Cod Bay, Massachusetts

The U.S. Geological Survey (USGS) and the Massachusetts Office of Coastal Zone Management (CZM) have cooperated to map approximately 480 km2 of the inner continental shelf in northern Cape Cod Bay, MA. This report contains geophysical and sampling data collected by the USGS during five research cruises between 2006 and 2008. The geophysical data include (1) swath bathymetry from interferometric sonar, (2) acoustic backscatter from interferometric and sidescan sonars, and (3) subsurface stratigraphy and structure from seismic-reflection profilers. The seafloor sampling data include sediment samples, photographs, and video tracklines. These spatial data support research on the influence that sea-level change and sediment supply have on coastal evolution and help identify the type, distribution, and quality of subtidal marine habitats within the coastal zone of Massachusetts.

Open-File Report↗

USGS1972

Preliminary mariner 9 report on the geology of Mars

Mariner 9 pictures indicate that the surface of Mars has been shaped by impact, volcanic, tectonic, erosional and depositional activity. The moonlike cratered terrain, identified as the dominant surface unit from the Mariner 6 and 7 flyby data, has proven to be less typical of Mars than previously believed, although extensive in the mid- and high-latitude regions of the southern hemisphere. Martian craters are highly modified but their size-frequency distribution and morphology suggest that most were formed by impact. Circular basins encompassed by rugged terrain and filled with smooth plains material are recognized. These structures, like the craters, are more modified than corresponding features on the Moon and they exercise a less dominant influence on the regional geology. Smooth plains with few visible craters fill the large basins and the floors of larger craters; they also occupy large parts of the northern hemisphere where the plains lap against higher landforms. The middle northern latitudes of Mars from 90 to 150† longitude contain at least four large shield volcanoes each of which is about twice as massive as the largest on Earth. Steep-sided domes with summit craters and large, fresh-appearing volcanic craters with smooth rims are also present in this region. Multiple flow structures, ridges with lobate flanks, chain craters, and sinuous rilles occur in all regions, suggesting widespread volcanism. Evidence for tectonic activity postdating formation of the cratered terrain and some of the plains units is abundant in the equatorial area from 0 to 120° longitude.Some regions exhibit a complex semiradial array of graben that suggest doming and stretching of the surface. Others contain intensity faulted terrain with broader, deeper graben separated by a complex mosaic of flat-topped blocks. An east-west-trending canyon system about 100–200 km wide and about 2500 km long extends through the Coprates-Eos region. The canyons have gullied walls indicative of extensive headward erosion since their initial formation. Regionally depressed areas called chaotic terrain consist of intricately broken and jumbled blocks and appear to result from breaking up and slumping of older geologic units. Compressional features have not been identified in any of the pictures analyzed to data. Plumose light and dark surface markings can be explained by eolian transport. Mariner 9 has thus revealed that Mars is a complex planet with its own distinctive geologic history and that it is less primitive than the Moon.

Icarus↗

USGS2013

Introduction to the special issue on “Understanding and predicting change in the coastal ecosystems of the northern Gulf of Mexico”

The coastal region of the northern Gulf of Mexico owes its current landscape structure to an array of tectonic, erosional and depositional, climatic, geochemical, hydrological, ecological, and human processes that have resulted in some of the world's most complex, dynamic, productive, and threatened ecosystems. Catastrophic hurricane landfalls, ongoing subsidence and erosion exacerbated by sea-level rise, disintegration of barrier island chains, and high rates of wetland loss have called attention to the vulnerability of northern Gulf coast ecosystems, habitats, built infrastructure, and economy to natural and anthropogenic threats. The devastating hurricanes of 2005 (Katrina and Rita) motivated the U.S. Geological Survey Coastal and Marine Geology Program and partnering researchers to pursue studies aimed at understanding and predicting landscape change and the associated storm hazard vulnerability of northern Gulf coast region ecosystems and human communities. Attaining this science goal requires increased knowledge of landscape evolution on geologic, historical, and human time scales, and analysis of the implications of such changes in the natural and built components of the landscape for hurricane impact susceptibility. This Special Issue of the Journal of Coastal Research communicates northern Gulf of Mexico research results that (1) improve knowledge of prior climates and depositional environments, (2) assess broad regional ecosystem structure and change over Holocene to human time scales, (3) undertake process studies and change analyses of dynamic landscape components, and (4) integrate framework, climate, variable time and spatial scale mapping, monitoring, and discipline-specific process investigations within interdisciplinary studies.

Journal of Coastal Research↗

USGS2017

Geomorphology, denudation rates, and stream channel profiles reveal patterns of mountain building adjacent to the San Andreas fault in northern California, USA

Relative horizontal motion along strike-slip faults can build mountains when motion is oblique to the trend of the strike-slip boundary. The resulting contraction and uplift pose off-fault seismic hazards, which are often difficult to detect because of the poor vertical resolution of satellite geodesy and difficulty of locating offset datable landforms in active mountain ranges. Sparse geomorphic markers, topographic analyses, and measurement of denudation allow us to map spatiotemporal patterns of uplift along the northern San Andreas fault. Between Jenner and Mendocino, California, emergent marine terraces found southwest of the San Andreas fault record late Pleistocene uplift rates between 0.20 and 0.45 mm yr –1 along much of the coast. However, on the northeast side of the San Andreas fault, a zone of rapid uplift (0.6–1.0 mm yr –1 ) exists adjacent to the San Andreas fault, but rates decay northeastward as the coast becomes more distant from the San Andreas fault. A newly dated 4.5 Ma shallow-marine deposit located at ∼500 m above sea level (masl) adjacent to the San Andreas fault is warped down to just 150 masl 15 km northeast of the San Andreas fault, and it is exposed at just 60–110 masl to the west of the fault. Landscape denudation rates calculated from abundance of cosmogenic radionuclides in fluvial sediment northeast of, and adjacent to, the San Andreas fault are 0.16–0.29 mm yr –1 , but they are only 0.03–0.07 mm yr –1 west of the fault. Basin-average channel steepness and the denudation rates can be used to infer the erosive properties of the underlying bedrock. Calibrated erosion rates can then be estimated across the entire landscape using the spatial distribution of channel steepness with these erosive properties. The lower-elevation areas of this landscape that show high channel steepness (and hence calibrated erosion rate) are distinct from higher-elevation areas with systematically lower channel steepness and denudation rates. These two areas do not appear to be coincident with lithologic contacts. Assuming that changes in rock uplift rates are manifest in channel steepness values as an upstream-propagating kinematic wave that separates high and low channel steepness values, the distance that this transition has migrated vertically provides an estimate of the timing of rock uplift rate increase. This analysis suggests that rock uplift rates along the coast changed from 0.3 to 0.75 mm yr –1 between 450 and 350 ka. This zone of recent, relatively rapid crustal deformation along the plate boundary may be a result of the impingement of relatively strong crust underlying the Gualala block into the thinner, weaker oceanic crust left at the western margin of the North American plate by the westward migration of the subduction zone prior to establishment of the current transform plate boundary. The warped Pliocene marine deposits and the presence of a topographic ridge support the patterns indicated by the channel steepness analyses, and further indicate that the zone of rapid uplift may herald elevated off-fault seismic hazard if this uplift is created by periodic stick-slip motion on contractional structures.

California↗

USGS2008

Physical properties of repressurized samples recovered during the 2006 National Gas Hydrate Program expedition offshore India

As part of an international cooperative research program, the U.S. Geological Survey (USGS) and researchers from the National Gas Hydrate Program (NGHP) of India are studying the physical properties of sediment recovered during the NGHP-01 cruise conducted offshore India during 2006. Here we report on index property, acoustic velocity, and triaxial shear test results for samples recovered from the Krishna-Godavari Basin. In addition, we discuss the effects of sample storage temperature, handling, and change in structure of fine-grained sediment. Although complex, sub-vertical planar gas-hydrate structures were observed in the silty clay to clayey silt samples prior to entering the Gas Hydrate And Sediment Test Laboratory Instrument (GHASTLI), the samples yielded little gas post test. This suggests most, if not all, gas hydrate dissociated during sample transfer. Mechanical properties of hydrate-bearing marine sediment are best measured by avoiding sample depressurization. By contrast, mechanical properties of hydrate-free sediments, that are shipped and stored at atmospheric pressure can be approximated by consolidating core material to the original in situ effective stress.

Conference Paper↗

USGS2026

An integrated mudstone facies classification scheme and revised interpretation of the sedimentologic processes driving carbon burial in the Cenomanian–Turonian Greenhorn Formation, Colorado, U.S.A.

Standardizing facies descriptions has proven key to integrating interpretations of depositional processes and environments from sedimentologic observations with geochemistry data for mudstone lithologies. Because of their fine-grained nature, high degree of compaction, and heterogeneous composition, standardizing methods for mudstone descriptions has proven difficult, but it is critical to formulating meaningful interpretations of the processes that govern the accumulation of organic-rich lithologies and their role in both petroleum systems and the global carbon cycle. In this study, we have developed a modified facies classification scheme for mudstone lithologies that incorporates sedimentologic and compositional observation at the hand-sample and thin-section scales with geochemical measurements, including bulk organic and inorganic geochemistry, to characterize these rocks and their variability more completely for improved interpretations of depositional environments during a low-order sea-level transgression. The facies described in this study are of the Cenomanian–Turonian Greenhorn Formation in the USGS #1 Portland Core drilled in Fremont County, Colorado. Strata of the Greenhorn Formation span Oceanic Anoxic Event 2 (OAE-2) and the preceding interval. Lithologies range from organic-rich argillaceous mudstones with varied sedimentary structures to organic-lean, highly bioturbated limestones. Six facies were identified, each differentiated by varied sedimentary structures and geochemical composition. These facies occur in a predictable stratigraphic stacking pattern that represents a low-order sea-level transgression with interpreted depositional environments ranging from terrigenous-dominated pro-delta and muddy continental shelf at the base of the interval to pelagic offshore marine at the top of the Greenhorn Formation. Though the facies are consistent with previous interpretations of depositional environments at this locale in the Cretaceous Western Interior Seaway during the Greenhorn cyclothem, the sedimentary processes governing the accumulation of organic-rich strata that have defined this interval are significantly revised. Variability in the proximity and intensity of bottom currents driven by storms and geostrophic flows were key to the accumulation of each facies, with significant sediment transport occurring even through deposition in the most oxygen-depleted bottom waters. The methodology and interpretations provided here are now being employed to basin-scale predictions of organic enrichment utilizing calibrated petrophysical methods. The approach and results from this study improve understanding of how organic and inorganic carbon was sequestered during perturbations to the global carbon cycle associated with events such as OAE-2.

Colorado↗