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USGS1978

Water resources data for Hawaii and other Pacific areas, water year 1977: Volume 2. Trust Territory of the Pacific Islands, Guam, American Samoa, and Northern Mariana Islands

Volume 2 of water resources data for the 1977 water year for other Pacific areas consist of records of stage, discharge, and water temperature; stage of a reservoir; and water levels in wells and springs. This report contains discharge records for 42 gaging stations; stage only record for 1 gaging station; water temperature for 26 gaging stations; and water levels for 13 observation wells. Also included are 56 low-flow partial-record stations. Additional water data were collected at various sites, not part of the systematic data collection program, and are published as miscellaneous measurements. These data represent that part of the National Water Data System operated by the U.S. Geological Survey and cooperating Governments and Federal agencies in other Pacific areas.

Hawaii↗

USGS2002

A National survey of methyl tert -butyl ether and other volatile organic compounds in drinking-water sources: Results of the random source-water survey

Methyl tert -butyl ether (MTBE) was detected in source water used by 8.7 percent of randomly selected community water systems (CWSs) in the United States at concentrations that ranged from 0.2 to 20 micrograms per liter ( μ g/L). The Random Survey conducted by the U.S. Geological Survey, in cooperation with the Metropolitan Water District of Southern California and the Oregon Health & Science University, was designed to provide an assessment of the frequency of detection, concentration, and distribution of MTBE, three other ether gasoline oxygenates, and 62 other volatile organic compounds (VOCs) in ground- and surface-water sources used for drinking-water supplies. The Random Survey was the first of two components of a national assessment of the quality of source water supplying CWSs sponsored by the American Water Works Association Research Foundation. A total of 954 CWSs were selected for VOC sampling from the population of nearly 47,000 active, self-supplied CWSs in all 50 States, Native American Lands, and Puerto Rico based on a statistical design that stratified on CWS size (population served), type of source water (ground and surface water), and geographic distribution (State). At a reporting level of 0.2 μ g/L, VOCs were detected in 27 percent of source-water samples collected from May 3, 1999 through October 23, 2000. Chloroform (in 13 percent of samples) was the most frequently detected of 42 VOCs present in the source-water samples, followed by MTBE. VOC concentrations were generally less than 10 μ g/L 95 percent of the 530 detections and 63 percent were less than 1.0 μ g/L. Concentrations of 1,1-dichloroethene, tetrachloroethene, trichloroethene, vinyl chloride, and total trihalomethanes (TTHMs), however, exceeded drinking-water regulations in eight samples. Detections of most VOCs were more frequent in surface-water sources than in ground-water sources, with gasoline compounds collectively and MTBE individually detected significantly more often in surface water. Use of personal and commercial motorized watercraft on surface-water bodies that are drinking-water sources is probably the reason for the elevated detections of gasoline contaminants relative to ground water. MTBE detections demonstrated a seasonal pattern with more frequent detections in surface water in summer months, which is consistent with seasonal watercraft use. The detection frequency of most VOCs was significantly related to urban land use and population density. Detections of any VOC, non-trihalo-methane compounds, gasoline compounds collectively, the specific gasoline compounds benzene, toluene, ethylbenzene, and xylenes (BTEX), MTBE, solvents, and refrigerants were significantly greater in areas with more than 60 percent urban land use and (or) population density greater than 1,000 people per square mile than in source waters from less urbanized or lower population-density areas. MTBE detections were five times more frequent in source waters from areas with high MTBE use than in source waters from low or no MTBE use, but, unlike other gasoline compounds, MTBE detections were not significantly related to the density of gasoline storage tanks near drinking-water sources.

Water-Resources Investigations Report↗

USGS2006

Major improvements in progress for Southern California Earthquake Monitoring

Major improvements in seismic and strong-motion monitoring networks are being implemented in southern California to better meet the needs of emergency response personnel, structural engineers, and the research community in promoting earthquake hazard reduction. Known as the TriNet project, the improvements are being coordinated by the California Institute of Technology (Caltech), the U.S. Geological Survey (USGS), and the California Division of Mines and Geology (CDMG) of the state's Department of Conservation. Already the ambitious instrument and system development project has started to record and disseminate ground motions from a spatially dense and robust network of high quality seismographs.

Eos, Transactions, American Geophysical Union↗

USGS1971

Quaternary faulting in the eastern Alaska Range

Quaternary faulting is well displayed along the Denali fault system and the recently recognized and related Totschunda fault system in the eastern Alaska Range. The principal movement on both fault systems is right-lateral strike-slip. Offset glacial features of Wisconsin age indicate minimum Holocene slip rates of 1.1 to 3.5 cm per year along parts of the Denali fault system, and 0.9 to 3.3 cm per year along the Totschunda fault system. Strike-slip movement along the Denali fault system may be no older than early Pliocene and, southeast of the Totschunda fault system junction, may have terminated by the middle Pleistocene. The strike-slip Totschunda fault system, a much younger feature probably no older than middle Pleistocene, exhibits 9 to 10 km of right-lateral offset and 1,500 m of relative vertical movement. The Totschunda fault system is aligned with, and has the same sense of slip as, the Fairweather fault in the Gulf of Alaska. The Denali fault system and the Queen Charlotte Islands fault are part of a major transform fault system separating the North American and Pacific plates. Continental southern Alaska between the Aleutian arc and the Denali fault system is now largely coupled to the Pacific plate. The Totschunda-Fairweather alignment probably represents the beginning of a new transform fault by-passing the southeast part of the Denali fault system.

Alaska↗

USGS1990

Kilbuck terrane: Oldest known rocks in Alaska

The Kilbuck terrane in southwestern Alaska is a narrow, thin crustal sliver or flake of amphibolite facies orthogneiss. The igneous protolith of this gneiss was a suite of subduction-related platonic rocks. U-Pb data on zircons from trondhjemitic and granitic samples yield upper-intercept (igneous) ages of 2070 ±16 and 2040 ±74 Ma, respectively. Nd isotope data from these rocks suggest that a diorite-tonalite-trondhjemite suite (ε Nd [T] = +2.1 to +2.7; T is time of crystallization) evolved from partial melts of depleted mantle with no discernible contamination by older crust, whereas a coeval granitic pluton (ε Nd [T] = -5.7) contains a significant component derived from Archean crust. Orthogneisses with similar age and Nd isotope characteristics are found in the Idono complex 250 km to the north. Early Proterozoic rocks are unknown elsewhere in Alaska. However, Phanerozoic plutons cutting several "continental" terranes in Alaska (southern Brooks Range and Ruby, Seward, and Yukon-Tanana terranes) have Nd isotope compositions indicative of Early Proterozoic (or older) crustal components that could be correlative with rocks of the Kilbuck terrane. Rocks with similar igneous ages in cratonal North America are rare, and those few that are known have Nd isotope compositions distinct from those of the Kilbuck terrane. Conversely, provinces with Nd model ages off 2.0-2.1 Ga are characterized by extensive 1.8 Ga or younger plutonism, which is unknown in the Kilbuck terrane. At present the case for a North American parentage of the Kilbuck terrane is not compelling. The possibility that the Kilbuck terrane was displaced from provinces off similar age in other cratons (e.g., Australian, Baltic, Guiana, and west African shields), or from the poorly dated Siberian craton, cannot be excluded.

Geology↗

USGS1988

The Blake Plateau Basin and Carolina Trough

Presently, the continental margin of the southeastern United States (Fig. 1) forms a zone of transition between the actively building, steep-fronted carbonate platform of the Bahamas and the typical eastern North American terrigenous clastic-dominated, drowned, shelf-slope-rise configuration. This region of the continental margin is underlain by two major sedimentary basins—the Blake Plateau Basin and the Carolina Trough (Fig. 2)—which are different in shape, basement structure, and history. Indeed, the two southern basins show some of the greatest contrasts of any basins of eastern North America, especially in their early response to rifting and in the change from rifting to drifting. The region has experienced abrupt major changes in geological conditions, most notably the onset of Gulf Stream flow in the early Tertiary. Morphologically, the area is dominated by the broad, flat Blake Plateau at about 800-1,000 m water depth (Fig. 1). The plateau is bounded to the east by the extremely steep Blake Escarpment, descending to 5,000 m water depths. To the west, a short continental slope rises to a continental shelf. This Blake Plateau morphology characterizes the margin east of Florida and north of the Bahamas. North of Florida the margin merges into the typical shelf-slope-rise morphology. Just north of the Blake Escarpment and its northern projection, the Blake Spur, the Blake Ridge extends away from the continental slope at water depths exceeding 2,000 m (Fig. 1). This broad ridge is a Cenozoic, sedimentary drift deposit controlled by bottom currents. (For the reader who is beginning to wonder why half of the features of this region seem to be named "Blake", the Blake was a Coast Survey steamer from which investigations off the southeastern U.S. were carried out in 1877 to 1880. Ferromanganese nodules were discovered on the Blake Plateau at that time [Murray, 1885].)

Blake Plateau basin; Carolina Trough↗

USGS2000

Ad hoc committee on global climate issues: Annual report

The AAPG Ad Hoc Committee on Global Climate Issues has studied the supposition of human-induced climate change since the committee's inception in January 1998. This paper details the progress and findings of the committee through June 1999. At that time there had been essentially no geologic input into the global climate change debate. The following statements reflect the current state of climate knowledge from the geologic perspective as interpreted by the majority of the committee membership. The committee recognizes that new data could change its conclusions. The earth's climate is constantly changing owing to natural variability in earth processes. Natural climate variability over recent geological time is greater than reasonable estimates of potential human-induced greenhouse gas changes. Because no tool is available to test the supposition of human-induced climate change and the range of natural variability is so great, there is no discernible human influence on global climate at this time.

American Association of Petroleum Geologists Bulle↗

USGS2016

The 3D Elevation Program and America's infrastructure

Infrastructure—the physical framework of transportation, energy, communications, water supply, and other systems—and construction management—the overall planning, coordination, and control of a project from beginning to end—are critical to the Nation’s prosperity. The American Society of Civil Engineers has warned that, despite the importance of the Nation’s infrastructure, it is in fair to poor condition and needs sizable and urgent investments to maintain and modernize it, and to ensure that it is sustainable and resilient. Three-dimensional (3D) light detection and ranging (lidar) elevation data provide valuable productivity, safety, and cost-saving benefits to infrastructure improvement projects and associated construction management. By providing data to users, the 3D Elevation Program (3DEP) of the U.S. Geological Survey reduces users’ costs and risks and allows them to concentrate on their mission objectives. 3DEP includes (1) data acquisition partnerships that leverage funding, (2) contracts with experienced private mapping firms, (3) technical expertise, lidar data standards, and specifications, and (4) most important, public access to high-quality 3D elevation data. The size and breadth of improvements for the Nation’s infrastructure and construction management needs call for an efficient, systematic approach to acquiring foundational 3D elevation data. The 3DEP approach to national data coverage will yield large cost savings over individual project-by-project acquisitions and will ensure that data are accessible for other critical applications.

Fact Sheet↗

USGS2020

Hydrogeologic units, contour maps, and cross sections of the Boone and Roubidoux aquifers, northeastern Oklahoma, 2020

The Boone and Roubidoux aquifers (or their equivalents) are the main sources of fresh groundwater in northeastern Oklahoma. Projected total water demand of both surface water and groundwater in northeastern Oklahoma is expected to increase approximately 56 percent from 2010 to 2060. This report provides an overview of the hydrogeology of northeastern Oklahoma, with an emphasis on the hydrogeologic units composing and surrounding the Boone and Roubidoux aquifers (the Western Interior Plains confining unit, the Boone aquifer, the Ozark confining unit, and the Roubidoux aquifer). This report also provides the hydrogeologic framework for an ongoing (as of 2020) hydrologic investigation to aid the Oklahoma Water Resources Board in determining the maximum annual yields of the Boone and Roubidoux aquifers. As a first step of this ongoing hydrologic investigation, the U.S. Geological Survey, in cooperation with the Oklahoma Water Resources Board and U.S. Army Corps of Engineers, developed hydrogeologic-unit maps, contour maps for the bases of the four hydrogeologic units, and generalized cross sections to further characterize the hydrogeologic framework of the Boone and Roubidoux aquifers. The contour maps illustrate the altitudes of the bases of each hydrogeologic unit. The altitude of the base of the Western Interior Plains confining unit ranged from 1,316 to −6,437 feet (ft) relative to North American Vertical Datum of 1988. The altitude of the base of the Boone aquifer ranged from 1,327 to −6,681 ft. The altitude of the base of the Ozark confining unit ranged from 1,275 to −6,720 ft. The altitude of the base of the Roubidoux aquifer ranged from 403 to −9,488 ft.

Oklahoma↗

USGS2011

Geomorphic and hydrologic dynamics of zero-order basins

The 1987 International Symposium on Erosion and Sedimentation in the Pacific Rim, held August 3–7, 1987, in Corvallis, Oreg., included a special session on the geomorphic and hydrologic dynamics of zero-order drainage basins. “Zero-order basin” is one of several terms used to describe unchanneled swales or hollows that may occupy considerable areas of higher-order drainage basins. These basins serve as important accumulation sites for water, sediment, and accompanying contaminants that subsequently may enter streams. Moreover, in many terrains along the Pacific rim, zero-order basins are significant geologic hazard sites in which rapid landslides and debris flows commonly begin. Widespread recognition o f the importance of zero-order basins has occurred only within the last 15 years, and this special session was aimed at collecting and assessing some of the pertinent knowledge that has been gained to date.

Oregon↗

USGS2014

Report of the committee on chemistry of natural waters, 1933–34

The personnel of this Committee during the past year, practically the same as during the previous year, has been as follows: C. S. Howard, Chairman—United States Geological Survey, Washington, D.C. L. C. Case—Gypsy Oil Company, Tulsa, Oklahoma. W. D. Collins—United States Geological Survey, Washington, D.C. H. F. Flynn—United States Engineer Office, 35 South Ninth Street, Philadelphia, Pennsylvania. W. P. Kelley—University of California, Riverside, California. Alfred C. Lane—Tufts College, Tufts College, Massachusetts. Augustus Locke—477 Mills Building, San Francisco, California. R. D. Leitch—United States Bureau of Mines, Pittsburgh, Pennsylvania. H. T. Logan—United States Bureau of Standards, Washington, D.C. Thomas S. Lovering—United States Geological Survey, Washington, D.C. Thomas E. Means—111 Sutter Street, San Francisco, California. F. B. Plummer—University of Texas, Austin, Texas. J. W. Sale—United States Food and Drug Administration, Washington, D.C. C S. Scofield—Bureau of Plant Industry, Department of Agriculture, Washington, D.C. Thomas G. Thompson—University of Washington, Seattle, Washington.

Eos, Transactions, American Geophysical Union↗

USGS2014

Ground‐water studies in the Southwest

Geologists are concerned with the rock‐systems that form the crust of the Earth. The groundwater geologists are concerned with the rock‐systems specifically because the open spaces which the rocks contain serve as reservoirs and conduits for water—water which performs a large part of the geologic work that is in progress today and has been in progress during past ages; water which affects profoundly the whole hydrologic cycle and is still the principal source of water‐supply for mankind, as it has been for primitive man and the other land animals before the time of artificial waterworks.

Eos, Transactions, American Geophysical Union↗

USGS1969

Mesozoic California and the underflow of Pacific mantle

The Mesozoic evolution of California is interpreted as dominated by the underflow of oceanic mantle beneath the continental margin. Underflow during part of Late Cretaceous time of more than 2000 km of the eastern Pacific plate seems required by the marine magnetic data. Correspondingly, varied oceanic environments—abyssal hill, island arc, trench, oceanic crust, and upper mantle, perhaps also continental rise and abyssal plain—appear to be represented in the eugeosynclinal terranes of California. The rock juxtapositions accord with the concept that these materials were scraped off against the continent as the oceanic plate slid beneath it along Mesozoic Benioff seismic zones, which are now seen as serpentine belts separating profoundly different rock assemblages. The chaotic Franciscan Formation of coastal California consists of deep-ocean Late Jurassic to Late Cretaceous sedimentary, volcanic, crustal, and mantle materials. As open-ocean abyssal oozes and the oceanic crust beneath them were swept into the Benioff-zone trench at the continental margin, they were covered by terrigenous clastic sediments, and the entire complex was carried beneath the correlative continental-shelf and continental-slope deposits (Great Valley sequence) and the older Mesozoic complexes. The other eugeosynclinal terranes of California can be interpreted, albeit with less confidence, in similar terms of underflow of Pacific mantle. In the Klamath Mountains and northern Sierra Nevada, for example, Ordovician and Silurian ocean-floor materials, overlain by or juxtaposed against an Upper Silurian to Permian island arc, were swept in first to the continent, along with a large fragment of oceanic crust and mantle and another fragment of an old orogenic belt. This debris was followed by Permian and Triassic ocean-floor deposits. Late Triassic and Jurassic volcanic products from stocks and batholiths forming in the welded complexes lapped across both landward and oceanward sides of the region. Reversal of Cenozoic extension, strike-slip faulting, and volcanic crustal growth in the western United States reveals a Cretaceous tectonic pattern strikingly like the modern pattern of the Andes, so the paleotectonic setting of North America can be inferred from the South American present. The Mesozoic batholiths of North America, like the late Cenozoic volcanic belt of the central Andes, are products of the same rapid motion of oceanic plates that carried oceanic sediments against the continent to form eugeosynclinal terranes. Magmas generated in the Benioff zones formed the batholiths and the volcanic fields which initially capped them.

California↗

USGS1970

Sea-floor spreading at the junction between Gorda Rise and Mendocino Ridge

A Quaternary deformation pattern revealed by new sub-bottom acoustic profiles supplements previous knowledge derived chiefly from magnetic and seismic evidence on the contemporary tectonics off northern California. An inferred age for the sedimentary cover along the axis of the southern part of Gorda Rise suggests that no volcanism has occurred along that part of the rise for more than 100,000 years. Sea-floor spreading at the rise crest has been accommodated by sinking of a keystone block that forms the floor of Escanaba Trough, the median valley of the rise. Differential movement between Pacific and American tectonic plates could have caused the deformation pattern, and during this movement, the displacement offshore beyond the northwest end of the San Andreas fault is inferred to have divided at Cape Mendocino between a fault along Mendocino Ridge and a fault segment that connects with the Blanco fault farther northwest.

California↗

USGS2003

Lithofacies control in detrital zircon provenance studies: Insights from the Cretaceous Methow basin, southern Canadian Cordillera

High-frequency sampling for detrital zircon analysis can provide a detailed record of fine-scale basin evolution by revealing the temporal and spatial variability of detrital zircon ages within clastic sedimentary successions. This investigation employed detailed sampling of two sedimentary successions in the Methow/Methow-Tyaughton basin of the southern Canadian Cordillera to characterize the heterogeneity of detrital zircon signatures within single lithofacies and assess the applicability of detrital zircon analysis in distinguishing fine-scale provenance changes not apparent in lithologic analysis of the strata. The Methow/Methow-Tyaughton basin contains two distinct stratigraphic sequences of middle Albian to Santonian clastic sedimentary rocks: submarine-fan deposits of the Harts Pass Formation/Jackass Mountain Group and fluvial deposits of the Winthrop Formation. Although both stratigraphic sequences displayed consistent ranges in detrital zircon ages on a broad scale, detailed sampling within each succession revealed heterogeneity in the detrital zircon age distributions that was systematic and predictable in the turbidite succession but unpredictable in the fluvial succession. These results suggest that a high-density sampling approach permits interpretation of finescale changes within a lithologically uniform turbiditic sedimentary succession, but heterogeneity within fluvial systems may be too large and unpredictable to permit accurate fine-scale characterization of the evolution of source regions. The robust composite detrital zircon age signature developed for these two successions permits comparison of the Methow/Methow-Tyaughton basin age signature with known plutonic source-rock ages from major plutonic belts throughout the Cretaceous North American margin. The Methow/Methow-Tyaughton basin detrital zircon age signature matches best with source regions in the southern Canadian Cordillera, requiring that the basin developed in close proximity to the southern Canadian Cordillera and providing evidence against large-scale dextral translation of the Methow terrane.

Geological Society of America Bulletin↗

USGS2007

Quality of Selected Hungarian Coals

As part of a program conducted jointly by the U.S. Geological Survey and the Hungarian Geological Survey under the auspices of the United States-Hungarian Science and Technology Fund, a total of 39 samples from five coal mines in Hungary were selected for analysis. The mine areas sampled represent most of the coal mined recently in Hungary. Almost all the coal is used to generate electricity. Coals from the five mines (four underground, one surface) reflect differences in age, depositional setting, organic and inorganic components of the original sediments, and deformational history. Classified according to the ranking system of the American Society for Testing and Materials, the coals range in rank from lignite B (Pliocene[?] coals) to high volatile A bituminous (Jurassic coals). With respect to grade classification, based on seam-weighted averages of moisture, ash, and sulfur contents: (1) all contain high moisture (more than 10 percent), (2) all except the Eocene coals are high (more than 15 percent) in ash yield, and (3) two (Jurassic and Eocene coals) are high in sulfur (more than 3 percent) and three (Cretaceous, Miocene, and Pliocene coals) have medium sulfur contents (1 to 3 percent). Average heat values range from 4,000 to 8,650 British thermal units per pound.

Scientific Investigations Report↗

USGS2021

Risk-informed levee erosion countermeasure site selection and design in the Sacramento area part 2: Probabilistic numerical simulation of bank erosion

USACE partnered with the United States Department of Agriculture, Agricultural Research Service, United States Geological Survey, and Texas A&M University to evaluate the erodibility of the river banks and levees to inform probabilistic numerical simulations using the Bank Stability and Toe Erosion Model (BSTEM). This paper, the second of two parts, addresses processing the collected data to inform inputs for probabilistic bank erosion estimates in BSTEM. Measuring the intrinsic soil properties for BSTEM is discussed in part one. Soil critical shear stress and soil erodibility coefficients were calibrated by Unified Soil Classification soil type to observed erosion on the American River. Adjustments were made in the probability density functions for these parameters to reflect field-measured variability and carry forward the reduction in error achieved during calibration. The resulting calibrated values were tested at additional sites, validating the resulting critical shear stress and soil erodibility coefficient values and probability density functions for more robust probabilistic bank erosion estimates using BSTEM.

California↗

USGS1973

Geology and paleontology of Canal Zone and adjoining parts of Panama: Description of Tertiary mollusks (additions to gastropods, scaphopods, pelecypods Nuculidae to Malleidae)

Chapter E adds 112 described species and subspecies (a few briefly described) to the some 440 covered in preceding chapters : 27 additional gastropods, 18 scaphopods, and 67 pelecypods in 10 families. It is estimated that about 125 species are to be added in chapter F, the final chapter. The Arcidae is by far the largest family in the pelecypods so far studied : 30 species in six genera. The genus Anadara is the largest in that family : 25 species, representing the subgenera Hawaiarca? , Rasia, Tosarca, Grandiarca, Potiarca , and Cunearca . Potiarca , based on a living western Pacific species, is adopted for many American species heretofore assigned to Cunearca . Eighteen of the 27 additional gastropods were found at a new locality in the late Eocene part of the Gatuncillo formation. They 'are assigned to 16 genera, 14 of which are not represented at other Gatuncillo localities. The genera include Faunus, Turnpanotonos , and Bezaneonia , which are rare in America, and the rare endemic American genus Harrisianella . The marine member of the Bohio (?) formation is now assigned to the late Eocene, instead of late Eocene or early Oligocene—the only change in age assignment. Eocene affinities are especially strengthened by the presence of Samanoetia samanensis and Volvariella? , if indeed the unnamed species represents that genus, as seems likely. Both the marine member of the Bohio( ?) and the late Oligocene part of the Bohio contain early small species of Anadara , subgenus Rasia . The fossils from the moderately deep-water facies of the late Oligocene Caimito formation include the earliest hexagonal Dentalium of the subgenus Dentalium s.s., from the American mainland, and a widespread and abundant species of the essentially deep-water subgenus Fissidentalium . Anadara chiriquiensis chiriquiensis , a relatively small form of the subgenus Grandiarca that is widely distributed in the Miocene Caribbean province, occurs in the Culebra formation. For the most part it indicates brackish water. Among the fossils from the La Boca formation proper, Cyphoma aff. C. intermedia is the earliest representative of an endemic American genus, and Isognomon mimeticus , a remarkable, narrowly mytiliform species is the type of the new subgenus Mimonion . Both the Culebra and La Boca, both of early Miocene age, contain predecessors of Gatun species. As in other chapters, the largest number of species is from the middle Miocene Gatun formation: 50 species. Bailya crossata is the first Tertiary species of the genus from the Caribbean region, and the earliest now known. A bizarre, incomplete gastropod is described as xancid?, genus?. The Gatun contains 13 of the 24 species of Anadara and half of the 12 species of the subgenus Rasia of that genus. In consideration of two battered and worn specimens of a large form of the subgenus Grandiarca , identified as Anadara grandis patricia? , the similar Tertiary forms in the Caribbean region are reviewed and divided into a brackish-water group and a marine group. The Gatun fauna now totals some 330 species.

Professional Paper↗