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USGS2013

Historical methane hydrate project review

In 1995, U.S. Geological Survey made the first systematic assessment of the volume of natural gas stored in the hydrate accumulations of the United States. That study, along with numerous other studies, has shown that the amount of gas stored as methane hydrates in the world greatly exceeds the volume of known conventional gas resources. However, gas hydrates represent both a scientific and technical challenge and much remains to be learned about their characteristics and occurrence in nature. Methane hydrate research in recent years has mostly focused on: (1) documenting the geologic parameters that control the occurrence and stability of gas hydrates in nature, (2) assessing the volume of natural gas stored within various gas hydrate accumulations, (3) analyzing the production response and characteristics of methane hydrates, (4) identifying and predicting natural and induced environmental and climate impacts of natural gas hydrates, and (5) analyzing the effects of methane hydrate on drilling safety. Methane hydrates are naturally occurring crystalline substances composed of water and gas, in which a solid water-‐lattice holds gas molecules in a cage-‐like structure. The gas and water becomes a solid under specific temperature and pressure conditions within the Earth, called the hydrate stability zone. Other factors that control the presence of methane hydrate in nature include the source of the gas included within the hydrates, the physical and chemical controls on the migration of gas with a sedimentary basin containing methane hydrates, the availability of the water also included in the hydrate structure, and the presence of a suitable host sediment or “reservoir”. The geologic controls on the occurrence of gas hydrates have become collectively known as the “methane hydrate petroleum system”, which has become the focus of numerous hydrate research programs. Recognizing the importance of methane hydrate research and the need for a coordinated effort, the U.S. Congress enacted Public Law 106-‐193, the Methane Hydrate Research and Development Act of 2000. This Act called for the Secretary of Energy to begin a methane hydrate research and development program in consultation with other U.S. federal agencies. At the same time a new methane hydrate research program had been launched in Japan by the Ministry of International Trade and Industry to develop plans for a methane hydrate exploratory drilling project in the Nankai Trough. Since this early start we have seen other countries including India, China, Canada, and the Republic of Korea establish large gas hydrate research and development programs. These national led efforts have also included the investment in a long list of important scientific research drilling expeditions and production test studies that have provided a wealth of information on the occurrence of methane hydrate in nature. The most notable expeditions and projects have including the following: -‐Ocean Drilling Program Leg 164 (1995) -‐Japan Nankai Trough Project (1999-‐2000) -‐Ocean Drilling Program Leg 204 (2004) -‐Japan Tokai-‐oki to Kumano-‐nada Project (2004) -‐Gulf of Mexico JIP Leg I (2005) -‐Integrated Ocean Drilling Program Expedition 311 (2005) -‐Malaysia Gumusut-‐Kakap Project (2006) -‐India NGHP Expedition 01 (2006) -‐China GMGS Expedition 01 (2007) -‐Republic of Korea UBGH Expedition 01 (2007) -‐Gulf of Mexico JIP Leg II (2009) -‐Republic of Korea UBGH Expedition 02 (2010) -‐MH-‐21 Nankai Trough Pre-‐Production Expedition (2012-‐2013) -‐Mallik Gas Hydrate Testing Projects (1998/2002/2007-‐2008) -‐Alaska Mount Elbert Stratigraphic Test Well (2007) -‐Alaska Iġnik Sikumi Methane Hydrate Production Test Well (2011-‐2012) Research coring and seismic programs carried out by the Ocean Drilling Program (ODP) and Integrated Ocean Drilling Program (IODP), starting with the ODP Leg 164 drilling of the Blake Ridge in the Atlantic Ocean in 1995, have also contributed greatly to our understanding of the geologic controls on the formation, occurrence, and stability of gas hydrates in marine environments. For the most part methane hydrate research expeditions carried out by the ODP and IODP provided the foundation for our scientific understanding of gas hydrates. The methane hydrate research efforts under ODP-‐IODP have mostly dealt with the assessment of the geologic controls on the occurrence of gas hydrate, with a specific goal to study the role methane hydrates may play in the global carbon cycle. Over the last 10 years, national led methane hydrate research programs, along with industry interest have led to the development and execution of major methane hydrate production field test programs. Two of the most important production field testing programs have been conducted at the Mallik site in the Mackenzie River Delta of Canada and in the Eileen methane hydrate accumulation on the North Slope of Alaska. Most recently we have also seen the completion of the world’s first marine methane hydrate production test in the Nankai Trough in the offshore of Japan. Industry interest in gas hydrates has also included important projects that have dealt with the assessment of geologic hazards associated with the presence of hydrates. The scientific drilling and associated coring, logging, and borehole monitoring technologies developed in the long list of methane hydrate related field studies are one of the most important developments and contributions associated with methane hydrate research and development activities. Methane hydrate drilling has been conducted from advanced scientific drilling platforms like the JOIDES Resolution and the D/V Chikyu, which feature highly advanced integrated core laboratories and borehole logging capabilities. Hydrate research drilling has also included the use of a wide array of industry, geotechnical and multi-‐service ships. All of which have been effectively used to collect invaluable geologic and engineering data on the occurrence of methane hydrates throughout the world. Technologies designed specifically for the collection and analysis of undisturbed methane hydrate samples have included the development of a host of pressure core systems and associated specialty laboratory apparatus. The study and use of both wireline conveyed and logging-‐while-‐drilling technologies have also contributed greatly to our understanding of the in-‐situ nature of hydrate-‐bearing sediments. Recent developments in borehole instrumentation specifically designed to monitor changes associated with hydrates in nature through time or to evaluate the response of hydrate accumulations to production have also contributed greatly to our understanding of the complex nature and evolution of methane hydrate systems. Our understanding of how methane hydrates occur and behave in nature is still growing and evolving – we do not yet know if methane hydrates can be economically produced, nor do we know fully the role of hydrates as an agent of climate change or as a geologic hazard. But it is known for certain that scientific drilling has contributed greatly to our understanding of hydrates in nature and will continue to be a critical source of the information to advance our understanding of methane hydrates.

Report↗

USGS2006

Genetic structure of eelgrass Zostera marina meadows in an embayment with restricted water flow

Genetic structure of the seagrass Zostera marina in a coastal lagoon with restricted water flow, and with heterogeneous water residence times and oceanographic characteristics, was assessed using 8 polymorphic microsatellite loci. Analyses of genetic differentiation (θ) and Bayesian clustering suggested that the Z. marina population in San Quintin Bay (SQB) is genetically substructured, with at least 4 genetically different groups: (1) West Head, (2) Mouth, (3) East Arm, and (4) East Head. The greatest θ value was observed between the most distant sites (θ = 0.095). The lowest values were found among sites closest to the mouth of the coastal lagoon (θ = 0.000 to 0.009). The maximum likelihood approach showed that the sites at the mouth have a mixed pattern of gene flow without a unidirectional pattern. In contrast, there was a clear pattern of asymmetrical gene flow from the mouth towards the West Head. These results suggested that the restriction of water flow at the heads, current pattern, and the distance between sites can reduce genetic flow and promote genetic differences within Z. marina meadows in small water embayments such as SQB. Though the population is genetically substructured and a 14% decline in cover has been detected, this study did not show evidence of a recent genetic bottleneck. In contrast, mouth sites have experienced a recent expansion in their population size, and also perhaps a recent influx of rare alleles from genetically distinct immigrants

Marine Ecology Progress Series↗

USGS2014

Assessing inundation hazards to nuclear powerplant sites using geologically extended histories of riverine floods, tsunamis, and storm surges

Most nuclear powerplants in the United States are near rivers, large lakes, or oceans. As evident from the Fukushima Daiichi, Japan, disaster of 2011, these water bodies pose inundation threats. Geologic records can extend knowledge of rare hazards from flooding, storm surges, and tsunamis. This knowledge can aid in assessing the safety of critical structures such as dams and energy plants, for which even remotely possible hazards are pertinent. Quantitative analysis of inundation from geologic records perhaps is most developed for and applied to riverine flood hazards, but because of recent natural disasters, geologic investigations also are now used widely for understanding tsunami hazards and coastal storm surges. Layered sedimentary deposits commonly give the most complete geologic record of large floods, storm surges, and tsunamis. Sedimentary layers may be preserved for hundreds or thousands of years in suitable depositional environments, thereby providing an archive of rare, high-magnitude events. All inundation hazards discussed in this report—riverine floods, tsunamis, and storm surges—have had long records extracted from sedimentary sequences, many specifically for hazard assessment. Geologic records commonly are imprecise, so most hazard assessments benefit from evaluation of many sites and rigorous uncertainty assessment. Despite uncertainties, geologic records commonly can improve knowledge of the types and magnitudes of hazards threatening specific sites or regions. New statistical tools and approaches can efficiently incorporate geologic information into frequency assessments. These tools are most developed for riverine flood hazards, but are to some degree transferable to other episodic natural phenomena such as tsunamis and storm surges. Even with these efficient statistical approaches for examining geologic records, systematic landscape changes may reduce the applicability of retrospective assessments. These non-stationarity issues (such as climate change, sea‑level rise, land-use, dams and flow regulation) may all affect the validity of using past experience—no matter how complete the record—to assess future likelihoods. These issues require site-specific consideration for nearly all hazard assessments drawn from geologic evidence. A screening of the 104 nuclear powerplants in the United States licensed by the Nuclear Regulatory Commission (at 64 sites) indicates several sites for which paleoflood studies likely would provide additional flood-frequency information. Two sites—Duane Arnold, Iowa, on the Cedar River; and David-Besse, Ohio, on the Toussaint River—have geologic conditions suitable for creating and preserving stratigraphic records of flooding and few upstream dams that may complicate flood-frequency analysis. One site—Crystal River, Florida1, on the Withlacoochee River and only 4 kilometers from the coast—has high potential as a candidate for assessing riverine and marine inundation hazards. Several sites on the Mississippi River have high geologic potential, but upstream dams almost certainly now regulate peak flows. Nevertheless, studies on the Mississippi River to evaluate long-term flood frequency may provide results applicable to a wide spectrum of regional hazard issues. Several sites in the southeastern United States have high geologic potential, and studies at these sites also may be helpful in evaluating hazards from outburst floods from landslide dams (river blockages formed by mass movements), which may be a regional hazard. For all these sites, closer investigation and field reconnaissance would be needed to confirm suitable deposits and settings for a complete paleoflood analysis. Similar screenings may help identify high-potential sites for geologic investigations of tsunami and storm-surge hazards.

Scientific Investigations Report↗

USGS2024

Evaluation of extinction risk for stream fishes within an urban riverscape using population viability analysis

1. The Santa Ana River in the Los Angeles region of California demonstrates common habitat degradation symptoms that are characteristic of the urban stream syndrome. These impacts have altered the Santa Ana River community structure, with few species as impacted as the native Santa Ana sucker (sucker; Pantosteus santaanae ). 2. Consequently, a recovery plan developed for sucker identified the need for a population viability analysis (PVA) to assess sucker extirpation risk. However, PVAs can be data-intensive and are subject to several sources of bias when standardized protocols are absent. 3. More than 20 years of sucker and arroyo chub (chub; Gila orcuttii ) surveys using different methods were compiled to build an integrated hierarchical multi-population PVA to estimate trends in abundance and extirpation probability of these native fishes from the Santa Ana River. 4. PVA modelling indicated similar patterns in sucker and chub abundance along the Santa Ana River, with the highest abundance of both species in the upper regions of the river during the early 2000s and downstream in recent years (2018–2022). Extirpation risk was estimated to be greatest near wastewater treatment facilities, where native fish abundance estimates have been zero since 2018. Extirpation risk was lower downstream of the wastewater treatment facilities for both species, although extinction risk was higher for sucker than chub throughout the river. 5. As the model evolves and more data are collected, the PVA could be used to assess the effects of various management actions, such as non-native predator removals and native fish re-introductions, on sucker and chub persistence.

California↗

USGS2017

Perspectives on chemical oceanography in the 21st century: Participants of the COME ABOARD Meeting examine aspects of the field in the context of 40 years of DISCO

The questions that chemical oceanographers prioritize over the coming decades, and the methods we use to address these questions, will define our field's contribution to 21st century science. In recognition of this, the U.S. National Science Foundation and National Oceanic and Atmospheric Administration galvanized a community effort (the Chemical Oceanography MEeting: A BOttom-up Approach to Research Directions, or COME ABOARD) to synthesize bottom-up perspectives on selected areas of research in Chemical Oceanography. Representing only a small subset of the community, COME ABOARD participants did not attempt to identify targeted research directions for the field. Instead, we focused on how best to foster diverse research in Chemical Oceanography, placing emphasis on the following themes: strengthening our core chemical skillset; expanding our tools through collaboration with chemists, engineers, and computer scientists; considering new roles for large programs; enhancing interface research through interdisciplinary collaboration; and expanding ocean literacy by engaging with the public. For each theme, COME ABOARD participants reflected on the present state of Chemical Oceanography, where the community hopes to go and why, and actionable pathways to get there. A unifying concept among the discussions was that dissimilar funding structures and metrics of success may be required to accommodate the various levels of readiness and stages of knowledge development found throughout our community. In addition to the science, participants of the concurrent Dissertations Symposium in Chemical Oceanography (DISCO) XXV, a meeting of recent and forthcoming Ph.D. graduates in Chemical Oceanography, provided perspectives on how our field could show leadership in addressing long-standing diversity and early-career challenges that are pervasive throughout science. Here we summarize the COME ABOARD Meeting discussions, providing a synthesis of reflections and perspectives on the field.

Marine Chemistry↗

USGS1982

Assessment of the petroleum, coal, and geothermal resources of the Economic Community of West African States (ECOWAS) region

Approximately 85 percent of the land area of the ECOWAS (Economic Community of West African States) region is covered by basement rocks (igneous and highly metamorphosed rocks) or relatively thin layers of Paleozoic, Upper Precambrian, and 'Continental Intercalaire? sedimentary rocks. These areas have little or no petroleum potential. Areas of the ECOWAS region that have potential for petroleum production or potential for increased petroleum production include the narrow belt of sedimentary rocks that stretches along the continental margin from Mauritania to Nigeria and the Niger Delta and the Benue depression. The Senegal Basin, located on the continental margin of Mauritania, Senegal, Gambia, Guinea Bissau, and Guinea, has been intensely explored by the oil industry and most of the larger structures onshore and on the shelf probably have been tested by drilling with little or no resulting commercial production. Unless basic ideas pertaining to the petroleum geology of the Senegal Basin are revised, future discoveries are expected to be limited to small fields overlooked by industry at a time when petroleum prices were low. On the continental shelf of Sierra Leone and the continental shelf of northeast and central Liberia, the sedimentary rocks are relatively thin, and industry has shown little interest in the area. On the continental rise of these countries, however, the sedimentary section, deposited in a complex fault-block system, increases in thickness. A renewal of industry interest in this deep-water area will probably follow further development of deep-water production technology. A recent oil discovery on the continental slope off the Ivory Coast is expected to spur further exploration offshore of southeastern Liberia, Ivory Coast, Ghana, Togo, and Benin. This relatively unexplored area in the Gulf of Guinea has good possibilities .for the discovery of giant oil fields. Nigeria's oil development from the Niger Delta may have peaked, as 13 of 14 giant oil fields were discovered prior to 1969 and the greatest number of fields were discovered in the period 1965 through 1967. Like delta regions in other parts of the world, individual oil fields of the Niger Delta are small to medium by world standards and future discoveries, therefore, are likely to reflect this reality. The natural gas resources of the Niger Delta, unlike its oil resources, are comparatively underdeveloped. Parts of the Benue depression in Nigeria and Niger could contain significant deposits of petroleum. The lower Benue depression, immediately north of the Niger Delta, has been extensively explored by drilling. Except for noncommercial discoveries of oil and gas and traces of oil and gas on the ground surface, the results of exploration in the lower Benue depression were negative. However, in the Lake Chad area of Chad and in southern Chad near the Central African Republic boundary, oil and gas discoveries were made just prior to the cessation of all drilling and exploration activity in early 1979. It is rumored that these discoveries may be large although little information is available. The relation between the two areas in Chad and their overall relation to the Benue depression is poorly understood; however, the possibility of thick sedimentary sections containing Cretaceous marine source rock and Tertiary reservoir beds-all contained within grabens in a highly faulted failed-arm system subjected to high heat flow--is attractive. Of the ECOWAS countries, only Nigeria and Niger produce coal commercially. Nigeria produces subbituminous coal from Paleocene-Maestrichtian and Maestrichtian (Late Cretaceous) age rocks of the Niger Delta region; reserves are estimated, on the basis of extensive drilling, to be 350 million tons (standard coal equivalent). In addition, lignite deposits of the Niger Delta appear to be large but have not been developed. Niger produces small amounts of coal used locally by uranium mine and mill operations from C

Open-File Report↗

USGS1984

Speculations on the petroleum geology of the accretionary body: an example from the central Aleutians

In the 300 km wide Adak-Amlia sector of the central Aleutian Trench ??? 36 000 km3 of offscraped trench fill makes up the wedge-shaped mass of the Aleutian accretionary body. Within this wedge, seismic reflection profiles reveal an abundance of potential hydrocarbon-trapping structures. These structures include antiforms, thrust and normal faults, and stratigraphic pinchouts. Maximum closure on these features is 2 km. In addition, the silt and possibly sand size sediment within the offscraped turbidite deposits, and the porous diatomaceous pelagic deposits interbedded with and at the base of the wedge, may define suitable reservoirs for the entrapment of hydrocarbons. Potential seals for these reservoirs include diagenetically-altered and -produced siliceous and carbonate sediment. The organic carbon input into the central Aleutian Trench, based on carbon analyses of DSDP Legs 18 and 19 core samples, suggests that the average organic carbon content within the accretionary body is approximately 0.3-0.6%. Heat flow across the Aleutian Terrace indicates that at present the oil generation window lies at a depth of 3-6.5 km. At depths of 8 km (which corresponds to the maximum depth the offscraped sediment has been seismically resolved beneath the lower trench slope), the probable high (170-180??C) temperatures prohibit all but gas generation. The dewatering of trench sediment and subducted oceanic crust should produce an abundance of fluids circulating within the accretionary body. These fluids and gases can conduct hydrocarbons to any of the abundant trapping geometries or be lost from the system through sea floor seepage. In the Aleutian accretionary body all the conditions necessary for the formation of oil and gas deposits exist. The size and ultimate preservation of these deposits, however, are dependent on the deformational history of the prism both during accretion and after the accretion process has been superceded by subsequent tectonic regimes. ?? 1984.

Marine and Petroleum Geology↗

USGS1979

Metals in Devonian kerogenous marine strata at Gibellini and Bisoni properties in southern Fish Creek Range, Eureka County, Nevada

A kerogen-rich sequence of siliceous mudstone, siltstone, and chert as much as 60 m thick on ridge 7129 in the southern Fish Creek Range, referred to as Gibellini facies of the Woodruff Formation, has been evaluated on the surface and in drill holes principally for its potential resources of vanadium, zinc, selenium, molybdenum, and syncrude oil content. The strata are part of a strongly deformed allochthonous mass of eugeosynclinal Devonian marine rocks that overlie deformed allochthonous Mississippian siliceous rocks and relatively undeformed autochthonous Mississippian Antler flysch at this locality. The vanadium in fresh black rocks obtained from drill holes and fresh exposures in trenches and roadcuts occurs chiefly in organic matter. Concentrations of vanadium oxide (V2O5) in unoxidized samples range from 3,000 to 7,000 ppm. In oxidized and bleached rock that is prevalent at the surface, concentrations of vanadium oxide range from 6,000 to 8,000 ppm, suggesting a tendency toward enrichment due to surficial weathering and ground-water movement. Zinc occurs in sphalerite, and selenium occurs in organic matter; molybdenum appears to occur both in molybdenite and in organic matter. Concentrations of zinc in unoxidized rock range from 4,000 to 18,000 ppm, whereas in oxidized rock they range from 30 to 100 ppm, showing strong depletion due to weathering. Concentrations of selenium in unoxidized rock range from 30 to 200 ppm, whereas in oxidized rock they range from 200 to 400 ppm, indicating some enrichment upon weathering. Concentrations of molybdenum in unoxidized rock range from 70 to 960 ppm, whereas in oxidized rock they range from 30 to 80 ppm, indicating strong depletion upon weathering. Most fresh black rock is low-grade oil shale, and yields as much as 12 gallons/short ton of syncrude oil. Metahewettite is the principal vanadium mineral in the oxidized zone, but it also occurs sparsely as small nodules and fillings of microfractures in unweathered strata. In fresh rock, bluish-white opaline-like silica (chalcedonic quartz) fills microfractures, and is believed to have originated by diagenetic mobilization of opaline silica from radiolarian tests and sponge spicules. As revealed by microscopic study, the Gibellini facies originally consisted of siliceous muds, slimes, and oozes high in organic constituents. The organic matter is amorphous flaky and stringy sapropel, and probably includes remains of bacteria, phytoplankton, zooplankton, and minor higher plants. Recognizable organic remnants include radiolarian tests, sponge spicules, conodonts, brachiopod shells, algae, and humic debris. Diagnostic radiolarians indicate a Late Devonian age for the Gibellini facies of the Woodruff Formation. Some pyrite is disseminated through the rock and may be primary (syngenetic) but significant pyrite and marcasite occur in chalcedonic quartz veinlets and appear to be diagenetic. In fresh rock, black solid bitumen and liquid oil fill voids and microfractures. These early phase hydrocarbons probably were released during diagenesis from complex nonhydrocarbon molecular structures originating from living organisms, and formed without any major thermal degradation of the kerogen. Gas chromatographic analysis of the saturated hydrocarbon fraction indicates a very complex mixture dominated by branched and cyclic compounds. Conodont and palynomorph color alteration, vitrinite reflectance, and other organic geochemical data suggest that the organic matter in the rock is thermally immature and has not been subjected to temperatures greater than 60?C since deposition in Devonian time. All of these characteristics are consistent with the interpretation of a relatively low temperature and a shallow-burial history for the Gibellini facies on ridge 7129.

Open-File Report↗

USGS2000

Formation of ferromanganese crusts on northwest intertropical Pacific seamounts: Electron photomicrography and microprobe chemistry

Seven ferromanganese crusts from the northwest intertropical Pacific seamounts were analyzed for photomicroscopic growth structures, microprobe chemistry, and ages based on Co-chronometer growth rate. The crusts on the Marshall Islands seamounts are thick and ale divided into phosphatized lower older and nonphosphatized upper younger growth generations: the older crust consists of compact laminations and columns impregnated with carbonate fluoapatite (CFA), whereas the younger crust is characterized by porous botryoids and columns of ??-MnO2 and Fe oxyhydroxide. The crusts on the Federated States of Micronesia (FSM) and Palau Islands seamounts are thin and are often incorporated with inorganic opal-A in the uppermost part, comprising the younger generation. Some crusts show scours and fractures. Although the growth of crusts has been often interrupted by mass failure of slope sediments, the crusts on the Marshall Islands seamounts are estimated to have grown at rate of about 3 mm/Ma since the middle Eocene and to have been phosphatized in the late Oligocene during the host seamounts were located beneath the equatorial zone of high productivity. Prolonged infiltration of the oxygen minimum zone (OMZ) water into shallower water older crusts redistributed crust composition by precipitating CFA, enriching subsequent amounts of Mn and Ni, and removing some Co. The younger crust has formed at slower rate (about 2 mm/Ma) under the stronger influence of bottom-water circulation in the north of the equatorial zone, concentrating abundant Co. In the uppermost part of some crusts, siliceous skeletons transform with burial to inorganic opal-A and Si-rich Fe oxyhydroxide, suggesting that biosilica diagenesis can enhance crust growth. (C) 2000 Elsevier Science B.V.

Marine Geology↗

USGS1970

Development of the Astoria Canyon-Fan physiography and comparison with similar systems

A detailed bathymetric study of Astoria Canyon and Astoria Fan provides a model for typical submarine canyon-fan systems. The present canyon head is 9 miles (17 km) west of the Columbia River mouth but buried Pleistocene channels appear to have connected the two features in the past. The canyon, which is distinguished by its relief, V-shaped profiles, and numerous tributaries, winds sinuously and is coincident with apparent structural trends across the continental shelf and slope. At the fan apex, the canyon mouth merges smoothly into Astoria Channel, which is characterized by its U-shaped profiles, lower walls of even height, and levee development. Astoria Channel and the fan valley at the base of the continental slope are the most recently active of a series of main fan valleys that appear to have: ( 1 ) progressively “hooked left”; ( 2 ) migrated from north to south across the fan during its formation; and ( 3 ) been partly responsible for the asymmetrical shape of the fan. The deep, narrow upper fan valleys that characterize the steep (> 1:100, or 0°35′) and rough (10–30 fathoms, or 18–55 m) upper fan surface break into distributaries on the middle fan, where there is the sharpest change in gradient. The main valleys become broader and shallower down the fan, while the generally concave fan surface grades to nearly a flat seafloor (to gradients < 1:1000, or 0°0.5′), (< 10 fathoms, or 18 m relief). Similarity of Astoria Canyon-Fan system with other deep-sea fan and alluvial fan systems, suggests the hypothesis that size of drainage basin, sediment size, and sediment load control the size, gradient, and valley development of any fan system. Data from bathymetry, seismic refraction stations, and sediment load of the Columbia River indicate that the cutting of Astoria Canyon and the deposition of the unconsolidated sediment layer forming Astoria Fan could have been accomplished during the Pleistocene. A similar history can be suggested for other major submarine canyon-fan systems.

Oregon↗

USGS1935

Geology and ground-water resources of the island of Oahu, Hawaii

Oahu, one of the islands of the Hawaiian group, lies in the Mid-Pacific 2,100 miles southwest of San Francisco. The principal city is Honolulu. The Koolau Range makes up the eastern part of the island, and the Waianae Range the western part. Both are extinct basaltic volcanoes deeply dissected by erosion. The Koolau Volcano was the later to become extinct. The Waianae Range is made up of three groups of lavas erupted in Tertiary and possibly in early Pleistocene time. The exposed part of the older lava is nearly 2,000 feet thick and consists largely of thin-bedded pahoehoe. It is separated in most places from the middle lavas by an angular unconformity and talus breccia and in a few places by an erosional unconformity. The middle basalts are about 2,000 feet thick and closely resemble the lower ones except that they contain more aa. The upper lavas reach a thickness of about 2,300 feet and are mostly massive aa flows. The last eruptions produced large cinder cones and some nephelite basalts. The Waianae Volcano, like other Hawaiian volcanoes, produced only small amounts of ash, and the lavas were largely extruded from fissures a few feet wide, now occupied by dikes. The center of activity was near Kolekole Pass, at the head of Lualualei Valley. The Koolau Volcano is made up of two groups of lavas extruded in Tertiary and early Pleistocene (?) time. The older group, the Kailua volcanic series, is greatly altered by hydrothermal action and was extruded from fissures near Lanikai. The flows of the younger group, the Koolau volcanic series, were extruded from fissures about a mile south of the Kailua rift and have an exposed thickness of about 3,000 feet. The Koolau Volcano produced even less ash than the Waianae Volcano, and its flows are thin-bedded pahoehoe and aa. The eruptive center of the Koolau Volcano lies between Kaneohe and Waimanalo. Great amounts of both the Waianae and Koolau Ranges were removed by fluvial and marine erosion during the Pleistocene. The master streams are characterized by deep amphitheater-headed valleys. After this erosion cycle the island was submerged more than 1,200 feet, and these great valleys were drowned and alluviated. Besides this submergence, several strand lines, preserved up to 100 feet above present sea level occur, which may be due to world-wide changes in sea level in response to the withdrawal and restoration of water concurrent with the advances and recessions of the polar ice caps and to accompanying changes in the ocean floor. During this time of shifting ocean levels spasmodic eruptions occurred on the southeast end of the Koolau Range, producing numerous lava flows and tuff cones, most of which are nephelite basalt. The last of these eruptions occurred in Recent time. A description of the climate, rates of run-off, and results of experiments to determine evaporation and transpiration in the areas of high rainfall are given. It was found that the consumptive use decreases materially and becomes a very small percentage of the rainfall in the areas of high precipitation. The lava rocks of the island are very permeable and, because of a rainfall reaching a maximum of 300 inches a year, carry large amounts of ground water, confined and unconfined, basal and perched. The basal ground water floats on salt water because of its lower specific gravity. Consequently for each foot the water table stands above sea level, salt water lies about 42 feet below sea level, in accordance with the sea along the coast as basal ground water. In most places the lava rocks along the shore are overlain by an impermeable or nearly impermeable caprock consisting of submerged lateritic soils and marine noncalcareous sediments. These deposits retard the escape of basal ground water into the sea and give rise to artesian water, but unlike most other artesian systems, this one has no lower restraining formation. The artesian water is the principal source of domestic, municipal, and irrigation supplies. The average annual quantity pumped for the period 1928 to 1933 amounted to about 105,000,000,000 gallons, nearly 90 percent of which came from Koolau hasalt and the remainder from Waianae basalt. There are ten artesian areas in the Koolau Range and two in the Waianae Range. Hydraulic gradients in these basins were found to range from 1.2 to 3 feet to the mile. Because of these extremely flat gradients and the high permeability of the aquifers it is possible to reverse the hydraulic gradients by draft and make the water flow from one artesian area to another. The artesian water levels fluctuate in response to seasonal variations in draft and recharge and in a lesser way to tidal, barometric, and seismic pressures. The water, as shown by chemical analysis, is of excellent quality except where it is contaminated with sea water. Methods have been devised for freshening wells that have gone salty, for detecting leaks, for sealing leaky and defective wells, and for recharging the artesian basins. Owing to the danger of the wells becoming brackish with increased draft, it is believed that further large developments will be more successful if shafts are sunk to sea level in the basalt as far inland as practicable, and tunnels are driven from the bottom of the shafts near the top of the saturated zone. Favorable places for such development exist in Honolulu. In addition to the basal water in the volcanic rocks, water is found in the recent gravel, beach, and dune deposits, and the emerged reef limestone. This water has been recovered by wells and tunnels, and there are favorable localities for developing additional water of this type. The island contains two types of basal springs—those like the Pearl Harbor Springs, which issue from basalt and are supplied by overflow and leakage from the artesian basin, and those which issue from the coastal-plain sediments and are mainly return irrigation water. The total quantity of basal ground water issuing as springs is estimated to be 100,000,000 gallons a day. Ground water occurs at high levels, confined by dikes and perched on tuff, alluvium, and soil beds. These structures give rise to innumerable high-level springs. In the Koolau Range 60 tunnels yield about 33,000,000 gallons daily, of which about 95 percent is obtained from tunnels penetrating the dike complex of the Koolau volcanic series, about 2 percent from tunnels entering post-Koolau ash or tuff deposits, and the remainder from tunnels whose geologic relations are not certainly known. The average daily yield of the tunnels that recover dike water is 2,330 gallons a foot, but the average daily yield of the tunnels in post-Koolau tuff is 450 gallons a foot, and that of the tunnels in alluvium or soil is only 23 gallons a foot. Owing largely to the much lower rainfall on the Waianac Range, its 35 tunnels (not including two new tunnels under construction) yield only about 2,400,000 gallons daily, about 94 percent of which is believed to be obtained from dike systems. The average daily yield of the tunnels in this range that are supplied by dike systems is 581 gallons a foot, as compared to 5 gallons a foot from tunnels in ash or tuff. An extensive tunnel system is proposed to develop a large supply of high-level water for Honolulu from the dike complex of the Koolau series, and high-level water can be recovered by tunnels at many other places. The average daily discharge of all high-level springs in the Koolau Range is about 58,000,000 gallons, of which about 94 percent comes from the Koolau dike complex and about 6 percent from post-Koolau volcanic rocks. The average daily discharge of all high-level springs in the Waianae Range is about 500,000 gallons of which about 81 percent issues from the dike complex.

Hawaii↗

USGS1989

Geology of the Arabian Peninsula; shield area of western Saudi Arabia

Western Arabia lies within the low-latitude desert of north Africa and the Middle East, the core being the Arabian segment of the African Shield. The core of complex basement rocks accounts for about 670,000 km 2 , or one-third of the Arabian Peninsula. Reconnaissance mapping of these crystalline rocks, together with bordering sedimentary rocks and volcanic flows, begun in 1950, resulted during the next 13 years in a series of geologic and geographic maps without extensive texts. The maps served as general guides for development of natural resources, including water supplies, ore deposits, and building materials. An intensive exploration program that began in 1963 and involved numerous geologists has vastly increased geologic information. Rainfall in Arabia is meager and episodic, and vegetation is sparse except in isolated copses on the crest of the Hejaz Range. Comparison of flora with similar species in the Sudan, where records of rainfall have long been kept, allows evaluation of mean annual precipitation. Wandering bedouin following fodder created a delicate balance between population and water supply-now disturbed by wells drilled in alluvium and lava fields. A trapezoidal region of Precambrian crystalline rocks lies along the northeast flank of the Red Sea, with two long prongs extending northwest and southeast for a total of 1,800 km. These basement rocks of the Arabian Shield are well exposed on the uplands, scarp mountains, and coastal pediments where the Phanerozoic cover rocks have been stripped as a result of Paleozoic epeirogeny and Tertiary ramping. The shield outcrops are divided into three tectonic provinces by N. 45°W.- trending shear zones of the Najd fault system of latest Proterozoic and possibly earliest Paleozoic time. The southwestern province, the 'Asir1 upland, was sharply uplifted and tilted to the northeast during the Neogene. The northwestern province, consisting of the Ash Shifa'- Hisma upland as well as Jabal Shammar farther east, similarly was uplifted and tilted. These two provinces are separated by the flat-lying median N ajd province, which is chiefly bounded by the principal Najd faults. The outcrops of the shield rocks are of the Late Proterozoic Eonupper Riphean to Vendian or Infracambrian epochs, including the Ediacarian System. The most reliable isotopic ages range from about 900 to 560 m.y., but some Middle Proterozoic rocks may be present in the easternmost shield. The rocks are divided into six lithostratigraphic sequences, two plutonic suites, and an ophiolitic suite. The mafic and ultramafic volcanic and plutonic rocks of the ophiolitic suite everywhere were emplaced tectonically and are probably of different ages in different places. Some ophiolite occurs as obducted blocks, but most is highly deformed and altered to serpentinite in fault zones that mostly define sutures between different tectonic blocks or terranes within the shield. Three of the lithostratigraphic sequences consist of mafic to silicic volcanic rocks and volcanic-derived clastic rocks which, with their subvolcanic plutonic rocks of a dioritic suite, probably formed in oceanic island arcs during convergent plate tectonism. These rocks make up the primary, or first-formed, crust of the shield. Chemical analyses show that the primary shield rocks, regardless of age, are principally calc-alkalic with some associated tholeiitic varieties. Most of the layered rocks are andesitic, but they range from basalt to dacite and in places contain intercalated pillow basalt, marble, chert, and carbonaceous or graphitic schist. Most of the plutonic rocks of the dioritic suite are dioritic, but they range from gabbro to trondhjemite and rarely contain potassium feldspar. The sequences and an associated dioritic suite become younger toward the eastern shield, that is, the primary crust of the shield youngs toward the east. Two western sequences consist of the Jiddah (Samran) and BaishBahah Groups and range in radiometric age from about 900 to 800 m.y.; the eastern sequence consists of the Halaban (Hulayfah) Group and ranges from 800 to about 700 m.y. During subsequent orogeny, most of the rocks were intensely deformed and mostly metamorphosed to upper greenschist facies, but rising in places to the almandine-amphibolite facies. Two other lithostratigraphic sequences with an associated plutonic granitic suite are the products of two mountain-building episodes during which the primary crust was greatly thickened and converted into craton. The two sequences, including largely the Ablah (Al Ays) and Murdama (Shammar) Groups, consist of abundant sedimentary rocks, commonly arkosic, that are the erosional products of the orogenic mountains. They are several thousand meters thick. Less abundant calc-alkalic to alkalic volcanic rocks, commonly dacitic and rhyolitic, are intercalated with the sedimentary rocks. The plutonic rocks of the granitic suite in association with both sequences have syntectonic and posttectonic phases, are products of the orogenies, and are the principal new ingredients making up the craton. Gneiss domes were a significant part of these cratonization orogenies. In association with orogenic crustal heating, some of the low-density, more silicic tonalitic and trondhjemitic rocks of the primary crust rose as gneiss domes. Partial melting in the middle or lower crust below the gneiss domes produced large volumes of granitic magma that intruded the gneiss domes as granodioritic batholiths. The Ablah Group and the older part of the granitic suite are about 775 to 740 Ma old and are associated with the Ablah orogeny and early cratonization in the western and earlier formed half of the shield. The Murdama (Shammar) Group and the younger part of the granitic suite are about 660 to 580 Ma old and are associated with the culminant orogeny and late cratonization that was shieldwide. The granitic suite during both orogenies consists of early, syntectonic granodiorite batholiths associated with the gneiss domes and late, posttectonic monzogranite plutons. Only during the culminant orogeny, late magmatic evolution produced syenogranite and alkali-feldspar granite commonly in circular and ring-structured plutons and with associated explosive volcanic deposits (Shammar Group); final products, some of which have economic potential, were peralkalic and peraluminous. The late plutonism of the culminant orogeny was distinctly bimodal in that subordinate gabbroic rocks are associated with the granites. Various building blocks or terranes of the andesitic and dioritic primary crust were collisionally agglomerated during the Ablah orogeny, early cratonization, whereas the entire shield as currently exposed was further collisionally accreted and compressionally consolidated during the culminant orogeny, final cratonization. Thousands of kilometers of oceanic crust had to be subducted in about 300 m.y. to form the large primary crust of the Arabian Shield. The inevitable collisional events during consumption of such a large volume of oceanic crust invariably led to numerous collisional orogenies that collectively encompass the widely known Pan African tectonic episode. The youngest lithostratigraphic sequence, the Jubaylah Group, is essentially postcratonic, although it is the end product of the collisional culminant orogeny. Final east-west compression of the entire shield from about 580 to 560 m.y. caused the craton to fracture along the large northwest-trending, left-lateral faults and elsewhere along lesser, northeast-trending, right-lateral, conjugate faults of the N ajd fault system. Erosional products of this more localized deformation were the sedimentary rocks of the Jubaylah Group, which also includes intercalated andesitic to basaltic volcanic rocks of a mafic alkalic compositional trend. The collisional edge of an old continental plate (or tectonic fragments thereof), suspected on the eastern edge of the Arabian Shield, has not been shown with certainty to be exposed. Presumably, widespread contamination from such an old continental crust affects U/Pb, Sm/Nd, Rb/Sr, and common lead ratios in the young plutonic rocks of the easternmost shield. One mass of anorthosite near Jabal Khida' on the central eastern edge of the shield may be a fragment of this old continental plate in that associated granodiorite may be as old as 1,600 to 1,800 Ma. Epeirogenic uplift, erosion, and cooling of the uppermost shield during Early and Middle Cambrian time is indicated by an average fission track age of 510±52 m.y., on sphene from diorite (hornblende K-Ar age of 615±12 m.y.) in the southwestern part of the shield. The hiatus was followed by extensive deposition of the Cambro-Ordovician Saq Sandstone in the north and northeast and the Wajid Sandstone in the southeast and south of the shield. The Cambrian Siq Sandstone had already been deposited in the northern part. During the middle and late Paleozoic, broad epeirogeny caused further erosion of the shield until marine transgression deposited the Upper Permian Khuff Formation at least in the eastern part of the shield. In the southwestern shield, the nonmarine Upper Triassic Khums Sandstone was deposited variably on Wajid or Precambrian rocks and is overlain by limestone of the middle Upper Jurassic Amran Formation. Except for shallow marine sandstone of problematic Cretaceous age deposited on the Amran Formation in the south.western shield and on Precambrian rocks in the northwestern shield, the younger beds on the shield are Paleocene and younger, with the possibility that the lowermost are upper Maestrichtian. The early Tertiary beds contain vertebrate fossils of coastal marine or estuarine environment 250 km east of the Red Sea in the central shield. Marginal marine sediments were deposited in a western tongue of the latest Tethys Sea as late as Eocene on the western shield and at least as far south as Jiddah. The great harrats of flood basalt erupted on th~ western shield during late Oligocene and early Miocene at the same time a 2,000-kmlong continental rift valley developed along the future Red Sea axis. Within this rift valley, Baid freshwater tuffaceous lakebeds were deposited between mafic and silicic volcanoes. During late early Miocene time, the Red Sea opened at a rate of 4.4 cm/yr in a firststage movement while continental dikes and swarms of oceanic tholeiitic dikes, gabbro, and granophyre plutonic rocks were intruded into the rift sedimentary and volcanic rocks at the newly formed continental margin. The continental margin was deformed and greatly extended at this time. About 14 or 15 m.y., as the first-stage spreading stopped, the Red Sea Escarpment rose; its erosion caused deposition of coarse conglomerate of the Bathan Formation. About 3,000 m of evaporite was deposited on the young Red Sea oceanic crust during the late Miocene desiccation crisis. A second stage of sea-floor spreading about 4-5 m.y. produced the Red Sea axial trough, consisting of oceanic crust, as well as renewed uplift and tilting of the three tectonic provinces in response to compression from counterclockwise rotation against the Dead Sea Rift. This late movement caused widespread major stream capture, especially along the wadis that formerly drained southwesterly or northwesterly, the channels turning westward through narrow gorges to the coastal plain and the Red Sea.

Professional Paper↗

USGS2008

Cause-specific temporal and spatial trends in green sea turtle strandings in the Hawaiian Archipelago (1982-2003)

We investigated cause-specific temporal and spatial trends in sea turtle strandings in the Hawaiian Archipelago. Five species of sea turtle were recorded in 3,861 strandings over a 22-year period (1982–2003). Green turtles comprised 97% of these strandings with size and gender composition reflecting the demographic structure of the resident green turtle population and relative green turtle abundance in Hawaiian waters. The cause of strandings was determined by necropsy based on a complete gross external and internal examination. Totally 75% of the 3,732 green turtle strandings were from Oahu where strandings occur year-round. The most common known cause of the green turtle strandings was the tumour-forming disease, fibropapillomatosis (28%) followed by hook-and-line fishing gear-induced trauma (7%), gillnet fishing gear-induced trauma (5%), boat strike (2.5%), and shark attack (2.7%). Miscellaneous causes comprised 5.4% of strandings whereas 49% of green turtle strandings could not be attributed to any known cause. Green turtle strandings attributable to boat strike were more likely from Kauai and Oahu while fibropapilloma strandings were more likely from Oahu and Maui. Hook-and-line gear strandings were more likely from Oahu due to higher per capita inshore fishing effort. The specific mortality rate (conditional probability) for fibropapillomatosis was 88%, 69% for gillnet gear and 52% for hook-and-line gear. The probability of a dead green turtle stranding increased from 1982 but levelled off by the mid-1990s. The declining mortality risk was because the prevalence and severity of fibropapillomatosis has decreased recently and so has the mortality risk attributable to gillnet gear. Despite exposure to disease and inshore fishing gears, the Hawaiian green turtle stock continues to recover following protection since the late 1970s. Nevertheless, measures to reduce incidental capture of sea turtles in coastal Hawaiian fisheries would be prudent, especially since strandings attributable to hook-and-line fishing gear have increased steadily since 1982.

Hawai'i↗

USGS2000

Hydrology and water and sediment quality at James Campbell National Wildlife Refuge near Kahuku, Island of Oahu, Hawaii

The James Campbell National Wildlife Refuge occupies two lowland marsh and pond complexes on the northern coastal plain of Oahu: the mostly natural ponds and wetlands of the Punamano Unit and the constructed ponds of the Kii Unit. The U.S. Fish and Wildlife Service manages the Refuge primarily to protect and enhance habitat for four endangered species of Hawaiian waterbirds. Kii Unit is fed by artesian wells and rainfall, whereas Punamano Unit is fed naturally by rainfall, runoff, and ground-water seepage. Streams drain from the uplands into lowland ditches that pass through Kii Unit on their way to the ocean. A high-capacity pump transfers water from the inner ditch terminus at Kii to the ocean outlet channel. Stormwaters also exit the inner ditch system over flood-relief swales near the outlet pump and through a culvert with a one-way valve. A hydrologic investigation was done from November 1996 through February 1998 to identify and quantify principal inflows and outflows of water to and from the Refuge, identify hydraulic factors affecting flooding, document ground-water/surface-water interactions, determine the adequacy of the current freshwater supply, and determine water and sediment quality. These goals were accomplished by installing and operating a network of stream-gaging stations, meteorology stations, and shallow ground-water piezometers, by computing water budgets for the two Refuge units, and by sampling and analyzing water and pond-bottom sediments for major ions, trace metals, and organic compounds. Streamflow during the study was dominated by winter stormflows, followed by a gradual recession of flow into summer 1997, as water that had been stored in alluvial fans drained to lowland ditches. Outflow at the ditch terminus in 1997 was 125 million gallons greater than measured inflow to the coastal plain, mainly reflecting gains from ground water along the ditches between outlying gages and the ditch terminus. Of the measured 1997 outflow, 98 percent was through the Kii outlet pump, with the outlet culvert valve only opening for brief periods during storms. Large volumes of stormflow overflowed the flood-relief swales unmeasured. The largest storm of the study, in November 1996, was estimated to have a flood frequency of about 3 to 4 years. Streamflow exceeded culvert capacity and overtopped Kamehameha Highway at Kalaeokahipa Stream and Hospital ditch. Slight overbank flooding in Kii ditch resulted strictly from high discharge. Minor overbank flooding farther out on the coastal plain probably was caused mainly by the small hydraulic gradients available to convey stormflows along the lowland ditches. Stormwaters flooded Kii ponds and flowed back upstream along Punamano ditch into Punamano marsh, introducing suspended sediment and possibly other contaminants to the Refuge. Two smaller storms in January 1997 resulted in smaller flows and no overbank flooding. The Kii outlet pump ran continuously for 7 days during the November 1996 storm and for 1 to 2 days during the January 1997 storms. During all three storms, the outlet culvert valve opened and the inner ditches overtopped the flood-relief swales, allowing free outflow of water from the inner ditch. Backwater effects hindered drainage during the January 1997 storms at Hospital ditch at Kamehameha Highway, and at Punamano ditch at Nudist Camp Road (where the backflow into Punamano marsh in November 1996 constituted an extreme backwater effect). A probable marine backwater effect was imposed at the ocean outlet ditch during the November 1996 storm through a combination of high spring tides and wave setup from large surf. Whether this backwater effect propagated upstream in the ditches to affect inland sites could not be determined conclusively. A sand plug may have built up in the ocean outlet channel before the November 1996 storm, but if so, it probably washed out prior to, or early in the storm, and was not present at the time of peak stage at inland sites. A season-long buildup of the sand plug in late 1997 was inferred from rising water levels in the outlet ditch. Seawater flows up the outlet channel or over the sand berm and into the outer ditch system on most high tides, and particularly during spring high tides. Ponds and ditches of the Refuge and surrounding lowlands have mud- and clay-lined bottoms that form an effective confining unit and inhibit interaction with an underlying shallow limestone aquifer. At Kii Unit, pond levels are higher than adjacent ditch levels and underlying ground-water levels, establishing lateral and downward head gradients that could foster seepage losses from the ponds. Regional ground-water discharge from the Koolau aquifer to the coastal-plain sediments is mostly diffuse, but is concentrated where ridges of Koolau Basalt plunge beneath coastal-plain sediments near Punamano Unit and at the head of Hospital ditch. Kii ditch gains brackish ground water downstream of Kamehameha Highway. Wastewater disposal from the sewage treatment plant adjoining Kii Unit poses little or no threat to Refuge habitat. Disposal is at six injection wells located 0.45 mi away at Kahuku, and the wells inject into confined limestone aquifers that do not extend to Kii Unit. The natural freshwater supply to Punamano Unit is adequate for maintaining the wildlife habitat, judging from stable pond levels and low salinities there. A monthly water budget for Punamano showed an apparent annual deficit in measurable flows in 1997, requiring unmeasured ground-water gains equalling 51 inches of water. The freshwater supply to Kii Unit is inadequate according to Refuge managers, because there is not enough water to manipulate levels adequately in the ponds during most of the year, and particularly during the driest months. This is confirmed by monthly deficits in the water budget for the Kii ponds during summer months. However, the Kii budget showed an annual surplus in measurable flows for 1997 equalling 24 inches of water. Unmeasured losses are required to explain the apparent annual surplus, such as discharge to the ditches through pond water-control structures and downward and/or lateral ground-water seepage. The apparent surplus at Kii is strictly hydrologic and is not a surplus in a management sense; it cannot be stored or used to supply the Refuge, but instead reflects losses from the system that render this amount of water unavailable for use. The budget year, 1997, was drier than normal (24 percent below long-term mean rainfall) and so the measured potential evaporation for 1997 was probably higher than the long-term mean. Few metals or organic compounds of potential concern were detected in pond and ditch waters and in pond-bottom sediments. Detected pesticides were at trace levels or just above minimum reporting limits. Exceptions that exceeded quality guidelines for freshwater sediment were copper and zinc in sediment from Kii ponds C and D, and copper in sediment from Punamano north pond. Therefore, urban and agricultural runoff probably have contributed little in the way of harmful metals or organic compounds to the Refuge, although the potential for such contribution remains from periodic flooding of the ponds by ditch stormflows. Salinity was low throughout most Refuge waters, qualifying as fresh to slightly brackish and suitable for the environmental needs of Refuge fauna. Higher salinities have been observed in ditches during past periods of sugarcane cultivation and saltwater aquaculture, however. Resumption of saltwater aquaculture could raise ditch salinities if saltwater effluents are disposed directly into the ditches, as they were in the past.

Hawaii↗

USGS2018

Strong variation in weathering of layered rock maintains hillslope‐scale strength under high precipitation

The evolution of volcanic landscapes and their landslide potential are both dependent upon the weathering of layered volcanic rock sequences. We characterize critical zone structure using shallow seismic V p and V s profiles and vertical exposures of rock across a basaltic climosequence on Kohala peninsula, Hawai’i, and exploit the dramatic gradient in mean annual precipitation (MAP) across the peninsula as a proxy for weathering intensity. Seismic velocity increases rapidly with depth and the velocity–depth gradient is uniform across three sites with 500–600 mm/yr MAP, where the transition to unaltered bedrock occurs at a depth of 4 to 10 m. In contrast, velocity increases with depth less rapidly at wetter sites, but this gradient remains constant across increasing MAP from 1000 to 3000 mm/yr and the transition to unaltered bedrock is near the maximum depth of investigation (15–25 m). In detail, the profiles of seismic velocity and of weathering at wet sites are nowhere monotonic functions of depth. The uniform average velocity gradient and the greater depths of low velocities may be explained by the averaging of velocities over intercalated highly weathered sites with less weathered layers at sites where MAP > 1000 mm/yr. Hence, the main effect of climate is not the progressive deepening of a near‐surface altered layer, but rather the rapid weathering of high permeability zones within rock subjected to precipitation greater than ~1000 mm/yr. Although weathering suggests mechanical weakening, the nearly horizontal orientation of alternating weathered and unweathered horizons with respect to topography also plays a role in the slope stability of these heterogeneous rock masses. We speculate that where steep, rapidly evolving hillslopes exist, the sub‐horizontal orientation of weak/strong horizons allows such sites to remain nearly as strong as their less weathered counterparts at drier sites, as is exemplified by the 50°–60° slopes maintained in the amphitheater canyons on the northwest flank of the island.

Hawai'i↗

USGS1997

Preliminary geologic map of the San Fernando 7.5' quadrangle, southern California: A digital database

The city of San Fernando sits atop a structurally complex, sedimentologically diverse, and tectonically evolving late Tertiary-Quaternary basin situated within the Transverse Ranges of southern California. The surrounding San Fernando Valley (SFV) contains the headwaters of the Los Angeles River and its tributaries. Prior to the advent of flood control, the valley floor was composed of active alluvial fans and floodplains. Seasonal streams emanating from Pacoima and Big Tujunga Canyons drain the complex western San Gabriel Mountains and deposit coarse, highly permeable alluvium that contains generally high-quality ground water. The more shallow western part derives mainly from Tertiary and pre-Tertiary sedimentary rocks, and is underlain by less permeable, fine-grained deposits containing persistent shallow ground water and poorer water quality. Home of the 1971 San Fernando and the 1994 Northridge earthquakes, the SFV experienced near-record levels of strong ground motion in 1994 that caused widespread damage from strong shaking and ground failure. A new map of late Quaternary deposits of the San Fernando area shows that the SFV is a structural trough that has been filled from the sides, with the major source of sediment being large drainages in the San Gabriel Mountains. Deposition on the major alluvial fan of Tujunga Wash and Pacoima Wash, which issues from the San Gabriel Mountains, and on smaller fans, has been influenced by ongoing compressional tectonics in the valley. Late Pleistocene deposits have been cut by active faults and warped over growing folds. Holocene alluvial fans are locally ponded behind active uplifts. The resulting complex pattern of deposits has a major effect on liquefaction hazards. Young sandy sediments generally are highly susceptible to liquefaction where they are saturated, but the distribution of young deposits, their grain size characteristics, and the level of ground water all are complexly dependent on the tectonics of the valley. The San Fernando area lies on the southern slopes of the San Gabriel Mountains. The basement rocks here include high-grade metamorphic rocks of Precambrian age. The mountains are largely composed of crystalline basement that includes the Pelona Scist of probable Mesozoic age that has been overthrust by Precambrian gneisses; the gneisses were subsequently intruded by Mesozoic plutons prior to overthrusting along the latest Cretaceous Vincent thrust. Gneisses of somewhat variable composition and possibly varying ages are found in four terranes, but not all are in contact with Pelona Schist. Large tracts of Precambrian (1.2 billion years old) andesine anorthosite are intrusive into 1.7 billion year-old Mendenhall gneiss, and are found in the western part of the San Gabriels. Mixed with these are younger marble, limestone, and schist of possible Paleozoic age found in association with plutons along the southern margin of the range. The older rocks are intruded by diorite, quartz diorite, and granodiorite of Jurassic age. Also present are siliceous sedimentary rocks of Jurassic age. A thick section of Tertiary sedimentary and volcanic rocks overlie these units. The sediments located south of the San Gabriel Fault are totally different in character from those on the northern range flank, and mostly resemble the western Transverse Ranges due to their deposition in the southeastern Ventura basin; approximately 3,000 m of these sediments are exposed north and west of the city of San Fernando in the Tujunga syncline. Some of the Tertiary rocks are Paleocene and Eocene in age, but the bulk of these rocks are Oligocene and Miocene in age. The Vasquez and Sespe Formations of basal basaltic volcanic and sandstone are Oligocene and lower Miocene in age. These are overlain by clastic rocks of Tick Canyon and Mint Canyon Formations of middle to late Miocene age. Above these rocks are the Castaic, Modelo, and Santa Margarita Formations of fossiliferous marine shale, sand

California↗

USGS2021

Diagenetic barite-pyrite-wurtzite formation and redox signatures in Triassic mudstone, Brooks Range, northern Alaska

Mineralogical and geochemical studies of interbedded black and gray mudstones in the Triassic part of the Triassic-Jurassic Otuk Formation (northern Alaska) document locally abundant barite and pyrite plus diverse redox signatures. These strata, deposited in an outer shelf setting at paleolatitudes of ~45 to 60°N, show widespread sedimentological evidence for bioturbation. Barite occurs preferentially in black mudstones (TOC = 0.93–6.46 wt%), forming displacive euhedral crystals with pyrite inclusions and rims, and late albite inclusions or intergrowths. Pyrite also occurs as small (3–20 μm) framboids, discontinuous laminae, euhedral and anhedral crystals, and replacements of barite and fossils (mainly radiolarians). Paragenetically early wurtzite is present as clusters of very small (1–3 μm) aggregates of radiating crystals 0.5 to 1.0 μm long with cores of organic matter that overgrow framboidal pyrite; later wurtzite forms 10- to 30-μm bladed crystals. Equant grains (3–30 μm) and small (20 μm) angular clusters of zinc sulfide that include <1-μm-long, comb-like structures are sphalerite or wurtzite, or both. Minor siderite forms euhedral crystals intergrown with albite that enclose wurtzite and barite. Illite shows intergrowths with sphalerite; rare K-feldspar is intergrown with barite. Formation of these minerals and assemblages is attributed to early diagenetic processes. Whole-rock geochemical data for 15 samples show large ranges in redox proxies including Post Archean Average Shale (PAAS)-normalized enrichment factors (EFs) for V, U, Mo, and Re, and Al-normalized ratios for V, U, and Mo. Results for most black mudstones, with or without abundant barite and/or pyrite, suggest deposition within an oxygen minimum zone. Cerium anomalies, PAAS-normalized and calculated on a detrital-free basis, range widely from 0.49 to 0.96 and may reflect diagenetic overprinting by Ce-depleted fluids. Considering data for both black and gray mudstones, the overall geochemical pattern together with evidence from pyrite framboid sizes suggest that redox conditions fluctuated greatly from euxinic to oxic, like the redox profiles reported for modern shelf sediments offshore Peru and Namibia. The euxinic redox signatures in some Otuk black mudstones may correlate with widespread Early to Middle Triassic ocean anoxic events proposed for other regions. Calculations of median EFs for trace elements in Otuk black mudstones reveal both enrichments and depletions. Normalizations to the median composition of the three least-mineralized black mudstones show that barite- and/or pyrite-rich samples display large (>50%) positive changes for Li (+80.4%), V (+75.6%), Sr (+75.9%), Ba (+790%), Cu (+92.1%), Ni (+169%), Ag (+156%), Au (+3091%), As (+109%), Sb (+476%), and Se (+205%); Zn shows a moderate positive change of +42.1%. Moderate negative changes are evident only for Ge (−47.2%) and W (−30.6%). The local enrichments may reflect one or more factors including redox variations in bottom waters and pore fluids, element mobility during diagenesis, and selective fractionation into minerals such as barite, pyrite, and wurtzite. Anomalously low U/Al and UEF values, compared to those for other modern and ancient organic-rich sediments and sedimentary rocks, are attributed to increased solubility and loss of U during bioturbation-related oxygenation in the subsurface. Physicochemical constraints on barite, pyrite, and wurtzite formation are informed by use of a pH-fO2 plot constructed at 10 °C. Based on paragenetic evidence for multistage deposition of these three minerals, together with the presence of illite intergrown with ZnS and K-feldspar with barite, proposed diagenetic trends involve an increase in pH and fO2 related to the ingress of sulfate-rich pore fluids during bioturbation, followed by a return to lower then higher pH and fO2 conditions linked to carbon, sulfur, barium, and iron cycling during diagenesis. Labile Ba of marine pelagic origin was mobilized from organic-rich sediment upward to the sulfate-methane transition zone where barite precipitated during the interaction of reduced Ba- and CH4-rich fluids with sulfate-bearing pore fluids. The formation of paragenetically early wurtzite (ZnS) crystals, as well as locally high EF values for Cu, Ni, Ag, and Au, is attributed to metal enrichment of pore fluids, with sources being derived in part from water-column deposition from hydrothermal plumes related to coeval Triassic seafloor vent systems including a volcanogenic massive sulfide deposit in British Columbia and the Wrangellia Large Igneous Province in Alaska.

Alaska↗

USGS2021

Genetic connectivity of the West Indian manatee in the southern range and limited evidence of hybridization with Amazonian manatees

The Antillean subspecies of the West Indian manatee is classified as endangered by the International Union for the Conservation of Nature (IUCN) Red List. In Brazil, the manatee population is listed as endangered with an estimated population size of 500–1,000. Historic hunting, recent habitat degradation, and fisheries bycatch have decreased the population size. The Amazonian manatee is listed as vulnerable by the IUCN with unknown population sizes within Brazil. The Antillean manatee occurs in sympatry with the Amazonian manatee in Brazil and hybridization has been previously indicated. To provide information on the genetic structure, diversity, and degree of hybridization in the sympatric zone near the Amazon River mouth, the mitochondrial DNA control region and 13 nuclear microsatellite markers were assessed on the two species. Samples were analyzed from the Antillean subspecies across its distribution in Brazil ( n = 78) and from the Amazonian species ( n = 17) at the Amazon River mouth and inland mainstem river. To assess the previously defined evolutionary significant units of Antillean manatees in the area, an additional 11 samples from Venezuela and Guyana were included. The Antillean manatee was found to be a single population in Brazil and had lower than average number of alleles (3.00), expected heterozygosity (0.34), and haplotype diversity (0.15) when compared to many other manatee populations. The low values may be influenced by the small population size and extended pressures from anthropogenic threats. Gene flow was identified with Venezuela/Guyana in admixed Antillean Brazil samples, although the two populations were found to be moderately divergent. The nuclear loci in Venezuela/Guyana Antillean manatee samples indicated high differentiation from the samples collected in the Amazon River ( F ST = 0.35 and R ST = 0.18, p = 0.0001). No indication of nuclear hybridization was found except for a single sample, “Poque” that had been identified previously. The distribution of Antillean manatees in Brazil is extensive and the areas with unique habitat and threats would benefit from independent management and conservation actions. Gene flow, resulting in genetic diversity and long-term population stability, could be improved in the southern range through habitat restoration, and the establishments of travel corridors and protected areas, which are particularly important for successful parturition and neonatal calf survival.

Frontiers in Marine Science↗