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45 records · Page 3Linked to original sources
USGS2008

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

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

Ichnos: An International Journal for Plant and Ani↗
USGS2004

Regional analysis of spiculite faunas in the permian phosphoria basin: Implications for paleoceanography

The sponge spiculites of the Permian Phosphoria basin, Antler high, and eastern Havallah basin were the southernmost expression of one of the largest spiculite belts in the Earth's history. This spiculite belt extended from Nevada to the Barents Sea. In Idaho and Nevada, the spicule populations of this belt are dominated by demosponge spicules and are distinctive for their abundant rhax microscleres, large monaxons, and lithistid desmas. They form an Eastern Belt of spiculites that interfingers with spicule assemblages derived from choristid demosponges and hexactinellids that lived along the eastern margin of the deeper Havallah basin. The Havallah basin assemblages are similar to those in Permian arc terranes to the west, and together the sponge populations in this domain constitute a dis- tinct Central Belt. Radiolarians are virtually absent in the siliceous microfossil populations of the Eastern Belt, abundant in the populations of the Central Belt, and dominant in the populations of a Western Belt confined to Mesozoic accretionary complexes in the Pacific Coast States. The scattered sponge spicules in the Western Belt radiolarites were derived from hexactinellids. During the Permian, the relative abundance and apparent diversity of siliceous sponges expanded over a wide range of depths in the basins from Nevada and Idaho to the open ocean. Radiolarian preservation and apparent diversity increased in the deeper Cordilleran basins as well. In the Arctic regions, significant sponge spiculites were deposited in epicratonic basins. At the same time that siliceous sponge populations expanded along the northwestern margin of Pangea, warm-water carbonate producers disappeared. Suppression of carbonate-producing organisms along the margin was critical to the accu- mulation and preservation of both the demosponge spiculites in the Eastern Belt and the spicule-rich argillites of the Central Belt. Vigorous thermohaline circulation was the major control on the paleobiogeography of the late Early, Middle, and early Late Permian along northwest Pangea. It was driven by cold, nutrient- and oxygen-rich northern waters and it produced a coastal current that swept down the margin of the supercontinent. The upwelling associated with deposition of world-class phosphorites in the Phosphoria basin was a part of this larger oceanographic system.

Handbook of Exploration and Environmental Geochemi↗
USGS2001

Cruise Report; RV Moana Wave cruise M1-01-GM; the bathymetry and acoustic backscatter of the mid shelf to upper slope off Panama City, Florida, northeastern Gulf of Mexico; September 3, through October 12, 2001, Panama City, FL to Panama City, FL

A zone of deep-water reefs is thought to extend from the mid and outer shelf south of Mississippi and Alabama to at least the northwestern Florida shelf off Panama City, Florida (Figure 1, 67kb). The reefs off Mississippi and Alabama are found in water depths of 60 to 120 m (Ludwick and Walton, 1957; Gardner et al., in press) and were the focus of a multibeam echosounder (MBES) mapping survey by the U.S. Geological Survey (USGS) in 2000 (Gardner et al., 2000; in press). If this deep-water-reef trend does exist along the northwestern Florida shelf, then it is critical to determine the accurate geomorphology and type of the reefs that occur because of their importance as benthic habitats for fisheries. Precisely georeferenced high-resolution mapping of bathymetry is a fundamental first step in the study of areas suspected to be critical habitats. Morphology is thought to be critical to defining the distribution of dominant demersal plankton/planktivores communities. Fish faunas of shallow hermatypic reefs have been well studied, but those of deep ahermatypic reefs have been relatively ignored. The ecology of deep-water ahermatypic reefs is fundamentally different from hermatypic reefs because autochthonous intracellular symbiotic zooxanthellae (the carbon source for hermatypic corals) do not form the base of the trophic web in ahermatypic reefs. Instead, exogenous plankton, transported to the reef by currents, serves as the primary carbon source. Thus, one of the principle uses of the morphology data will be to identify whether any reefs found are hermatypic or ahermatypic in origin. Community structure and trophodynamics of demersal fishes of the outer continental of the northeastern Gulf of Mexico presently are the focus of a major USGS reseach project. A goal of the project is to answer questions concerning the relative roles played by morphology and surficial geology in controling biological differentiation. Deep-water reefs are important because they are fish havens, key spawning sites, and are critical early larval and juvenile habitats for economically important sport/food fishes. It is known that deep-water reefs function as a key source for re-population (via seasonal and ontogenetic migration) of heavily impacted inshore reefs. The deep-water reefs south of Mississippi and Alabama support a lush fauna of ahermatypic hard corals, soft corals, black corals, sessile crinoids and sponges, that together form a living habitat for a well-developed fish fauna. The fish fauna comprises typical Caribbean reef fishes and Carolinian shelf fishes, plus epipelagic fishes, and a few deep-sea fishes. The base of the megafaunal invertebrate food web is plankton, borne by essentially continuous semi-laminar currents generated by eddies, spawned off the Loop Current, that periodically travel across the shelf edge. A few, sidescan-sonar surveys have been made of areas locally identified as Destin Pinnacles, Steamboat Lumps Marine Reserve (Koenig et al., 2000; Scanlon, et al., 2000; 2001), Twin Ridges (Briere, et al., 2000; Scanlon, et al., 2000), and Madison-Swanson Marine Reserve (Koenig et al., 2000; Scanlon, et al., 2000; 2001). However, no quantitative and little qualitative information about the geomorphology and surficial geology can be gained from these data. Existing bathymetry along the northwestern Florida shelf suggests the existence of areas of possible isolated deep-water reefs. NOAA bathymetric maps NOS NH16-9 and NG16-12 show geomorphic expressions that hint of the presence of reefs in isolated areas rather than in a continuous zone. There has been no systematic, high-resolution bathymetry collected in this area, prior to this cruise. After the successful mapping of the deep-water reefs on the Mississippi and Alabama shelf (Gardner et al., 2000; in press), a partnership composed of the USGS, Minerals Management Service, and NOAA was formed to continue the deep-reef mapping to the northwest Florida mid shelf and upper slope. This cruise is the first fruit of that partnership.

Florida↗
USGS1994

Habitat impacts of offshore drilling, eastern Gulf of Mexico

In this survey six offshore exploratory drill sites in a variety of environments and water depths were examined using a small research submersible. Sites varied from locations off northwest Florida to as far west as offshore Alabama. Water depths ranged from 21 m (70 ft) to 149 m (489 ft), and bottom sediments ranged from carbonate mud to Shelly quartz sand and silt to hard limestone. The age of the sites (the time between cessation of drilling activities and our observations) ranged from 15 months to 17 years . In a previous MMS-funded study, Shinn et al. (1989) and Dustan et al . (1991) examined eight sites off South Florida, where the age of the sites ranged from 2 to 29 years. The study documented repeatedly variability of impact from site to site . In the present study, we note a similar wide divergence of impacts . Using the concentration of barium (the major component of drill mud), cuttings, and trace metals as a basis, we found that time is the single most important factor determining the nature of habitat recovery. Older sites, particularly the 17-year-old site, were relatively pristine. At a 7-year-old site, two hurricanes did far more damage than drilling . At other sites, we documented a significant amount of discarded debris, and at two 5-year-old sites, large concentrations of barium and cuttings. Impacts, such as the extent of debris and cuttings, affected the bottom ranging in area from almost negligible (17-year-old site) to as much as 3 acres (4-year-old site) . As suspected, those sites with the most debris and/or open boreholes attracted the most abundant and diverse fish fauna.

Open-File Report↗
USGS1991

Cenozoic giant pectinids from California and the Tertiary Caribbean Province: Lyropecten, "Macrochlamis," Vertipecten, and Nodipecten species

Tertiary pectinids recognized for more than 125 years by field geologists can now be used to date and correlate 3-4 m.y. increments of the geologic record and to determine faunal distributions in relation to tectonic terranes. Fossil pectinids are commonly preserved in shallowmarine clastic deposits that mostly lack microfossils. The stratigraphic ranges of Lyropecten, "Macrochlamis," Vertipecten , and Nodipecten can be used to subdivide provincial megafaunal stages in California and to correlate chronostratigraphic units in the Pacific Northwest and Atlantic Coastal Plain. One New World taxon, "Macrochlamis" magnolia ojaiensis, n. subsp., supports a direct correlation between the middle "Vaqueros" Stage of California (interpolated as 27-23 m.y. B.P.) and an Upper Chattian-Lower Aquitanian Stage section in southwestern Switzerland. Two lithologic units widespread in California, the Vaqueros Formation (spanning 12 m.y., from the late Oligocene into the early Miocene) and Temblor Formation (deposited over a period of 26 m.y., from the late Eocene or early Oligocene to the middle Miocene), transgress much longer periods of time than have been generally recognized. Certain species pairs are identified as cognates, close relatives descended from a common ancestor. Close similarities are found between widely separated assemblages from the Salton Trough of California and the Caribbean, the Gulf Coastal Plain of eastern Mexico and the Sinu Valley of western Colombia, the Santa Rosalia area in Baja California Sur, Mexico, and the Paraguana Peninsula of Venezuela. Distribution patterns for relatively recently dispersed taxa have important implications for middle to late Cenozoic paleogeography and tectonic history, especially in west Mexico and the Caribbean. Speciation was concurrent with the closure of the Isthmus of Panama, the opening of the Gulf of California, and possibly with the northward translation of segments of the California Continental Borderland. Tertiary Caribbean and PacificPanamic Lyropectens and Nodipectens are plotted on a simplified tectonic map as an early step in considering Cenozoic molluscan distributions in relation to major plate boundaries. Taxa having unusual distributions are tabulated with the tectonic events that may have modified their observed geographic ranges. Southern California and the Baja California peninsula include tectonostratigraphic terranes and tectonic slivers that may have moved on the order of hundreds or thousands of kilometers in the Paleogene. Relations between recently dispersed faunas and tectonic terrane boundaries are further complicated by short-term variations in oceanographic phenomena such as currents, El Nino events, and shifts in areas of upwelling. Lyropecten evolved in the late Oligocene or early Miocene, Nodipecten by the late middle Miocene. According to the classification used here, Lyropecten still lives in the Galapagos. Holocene Nodipectens divide the Pacific-Panamic and Caribbean provinces into two subprovinces each. Habitat, life history, dispersal, and growth data are summarized for living Nodipectens, whose distinctive shell features include ledges and hollow nodes. Phylogenetic lineages are based on progressive trends in node formation and rib schemes, some of which have biostratigraphic significance.

Professional Paper↗
USGS2010

Reconnaissance geologic map of the Hayfork 15' quadrangle, Trinity County, California

The Hayfork 15' quadrangle is located just west of the Weaverville 15' quadrangle in the southern part of the Klamath Mountains geologic province of northern California. It spans parts of six generally north-northwest-trending tectonostratigraphic terranes that are, from east to west, the Eastern Klamath, Central Metamorphic, North Fork, Eastern Hayfork, Western Hayfork, and Rattlesnake Creek terranes. Remnants of a once-widespread postaccretionary overlap assemblage, the Cretaceous Great Valley sequence, crop out at three localities in the southern part of the Hayfork quadrangle. The Tertiary fluvial and lacustrine Weaverville Formation occupies a large, shallow, east-northeast-trending graben in the south half of the quadrangle. The small area of Eastern Klamath terrane is part of the Oregon Mountain outlier, which is more widely exposed to the east in the Weaverville 15' quadrangle. It was originally mapped as a thrust plate of Bragdon(?) Formation, but it is now thought by some to be part of an outlier of Yreka terrane that has been dislocated 60 km southward by the La Grange Fault. The Central Metamorphic terrane, which forms the footwall of the La Grange Fault, was formed by the eastward subduction of oceanic crustal basalt (the Salmon Hornblende Schist) and its overlying siliceous sediments with interbedded limestone (the Abrams Mica Schist) beneath the Eastern Klamath terrane. Rb-Sr analysis of the Abrams Mica Schist indicates a Middle Devonian metamorphic age of approximately 380 Ma, which probably represents the age of subduction. The North Fork terrane, which is faulted against the western boundary of the Central Metamorphic terrane, consists of the Permian(?) North Fork ophiolite and overlying broken formation and melange of Permian to Early Jurassic (Pliensbachian) marine metasedimentary and metavolcanic rocks. The ophiolite, which crops out along the western border of the terrane, is thrust westward over the Eastern Hayfork terrane. The Eastern Hayfork terrane is a broken formation and melange of volcanic and sedimentary rocks, including chert and blocks of amphibolite, limestone, and serpentinized ultramafic rocks. The chert contains radiolarians of Permian and Triassic ages, but none of clearly Jurassic age. In contrast, the cherts of the North Fork terrane contain Early and Middle Jurassic radiolarians in addition to those of Permian and Triassic ages; also, some limestones of the Eastern Hayfork terrane contain fossil faunas of Tethyan affinity, but those of the North Fork terrane do not. The Western Hayfork terrane is an andesitic volcanic arc that was accreted to the Eastern Hayfork terrane. It consists mainly of metavolcaniclastic andesitic agglomerate and tuff, as well as argillite and chert, and it includes the dioritic Ironside Mountain batholith, which intruded during Middle Jurassic time. Two large patches of Western Hayfork terrane mapped in the central part of the Eastern Hayfork terrane may be exposed through windows in the Eastern Hayfork terrane, although the structural relation is not clear. The Rattlesnake Creek terrane is a melange that occupies only a small area in the southwest corner of the Hayfork quadrangle; however, it is a major unit in the Hyampom 15' quadrangle to the west. It consists mainly of broken and sheared ophiolitic rocks of probable Permian or early Mesozoic age. The Cretaceous Great Valley sequence overlap assemblage here postdates the Early Cretaceous (approximately 136 Ma) emplacement of the Shasta Bally batholith, which is widely exposed to the east in the Weaverville 15' quadrangle. The Great Valley sequence once covered much of the southern Klamath Mountains; however, in the Hayfork quadrangle, only three small patches remain near its southern boundary. Weakly consolidated nonmarine sedimentary rocks of the Weaverville Formation of mid-Tertiary age, which contain abundant fossil plants, occupy a large, shallow, east-northeast-trending graben

California↗
USGS1996

Holocene paleoenvironments of Northeast Iowa

This paper presents the biotic, sedimentary, geomorphic, and climatic history of the upper part of the Roberts Creek Basin, northeastern Iowa for the late—glacial and Holocene, and compares these records with a C—O isotopic sequence from Coldwater Cave, 60 km northwest of Roberts Creek. The biotic record (pollen, vascular plant and bryophyte macrofossils, and insects) is preserved in floodplain alluvium that underlies three constructional surfaces separated by low scarps. Each surface is underlain by a lithologically and temporally distinct alluvial fill. The highest surface is underlain by the Gunder Member of the Deforest Formation, dating from 11 000 to 4000 yr BP; beneath the intermediate level is the Roberts Creek Member, dating from 4000 to 400 yr BP; and the lowest level is underlain by the Camp Creek Member, deposited during the last 380 yr. Pollen and plant macrofossils in the alluvial fill show that a typical late—glacial spruce forest was replaced by Quercus and Ulmus in the early Holocene. This early—to—middle Holocene forest became dominated by mesic elements such as Acer saccharum, Tilia americana, Ostrya virginiana, and Carpinus caroliniana as late as 5500 yr BP; in contrast, the closest sites to the west and north were at their warmest and driest and were covered by prairie vegetation between 6500 and 5500 yr BP. After 5500 yr BP, the forest in the Roberts Creek area was replaced by prairie, as indicated by a rich assemblage of plant macrofossils, although only Ambrosia and Poaceae became abundant in the pollen record. The return of Quercus ≈ 3000 BP (while nonarboreal pollen percentages remained relatively high) indicates that oak savanna prevailed with little change until settlement time. The bryophyte assemblages strongly support the vascular plant record. Rich fen species characteristic of boreal habitats occur only in the late—glacial. They are replaced by a number of deciduous—forest elements when early—to—middle Holocene forests were present, but mosses of forest habitats completely disappear when prairie became dominant. A few deciduous—forest taxa return during the late—Holocene, when oak savanna prevailed. The C—O isotopic record from stalagmite s in Coldwater Cave indicates a relatively stable environment from ≈ 8000 to 5100 yr BP, when the δ 13 C values indicate a change in vegetation dominated by C 3 (predominantly forest) to C 4 (predominantly prairie) plants. About 4900 yr BP, the rise in 18 O values indicates a temperature increase of ≈ 1.5 ° C. The fact that the vegetational change suggested by the δ 13 C values preceded the temperature increase suggests that fire may have been an important factor in converting forest to prairie. Abundant charred seeds and other plant material at Roberts Creek 4830 yr BP support this hypothesis. The 18 O values remain constant from ≈ 5100 to ≈ 3000 yr BP, but the δ 13 C values gradually rise, indicating that soil formed under forest takes at least 2000 yr for its carbon to reach equilibrium after replacement by prairie vegetation. The return of oak to form savanna is reflected in the gradual decline of δ 13 C values in the last 3000 yr BP; O isotopic values drop sharply by ≈ 1 ° C ≈ 2800 yr BP and then were relatively stable. In contrast to the vegetational and isotopic records, the insect assemblages suggest little change in the local environments throughout most of the Holocene. All of the beetle taxa presently occur in eastern Iowa. The relative stability through the Holocene indicates that both open grassland and riparian woodland elements were present throughout. Settlement, land clearing, and land cultivation by EuroAmericans in the region caused rapid erosion of the upland landscape, the deposition of 1—2 m of sediment across the floodplain, a replacement of the native vegetation with ruderal species, a decimation of the native insect fauna, and a degradation of water quality in the stream. These changes in the landscape, vegetation, and insect faunas are as striking as those associated with glacial—interglacial transitions. The timing and direction of changes in the vegetation at Roberts Creek generally correlate well with the carbon and oxygen isotopic record in speleothems at nearby Coldwater Cave and indicate that climate was the main forcing function. However, the contrast between the vegetational change and the stability of the beetle population suggests that climatic changes were subtle. We hypothesize that the factors involved in the Holocene changes were seasonal changes in temperature and precipitation that may not have resulted in much mean annual change. Such changes may have affected the vegetation more than the insect fauna.

Iowa↗
USGS1991

Birds of the Kilbuck and Ahklun mountain region, Alaska

Between 1952 and 1988, we studied the abundance, distribution, occurrence, and habitats used by birds in the northwest portion of Bristol Bay and the adjacent Kilbuck and Ahklun mountains. In the 809 days we were present, we conducted 53 studies or surveys of birds in the region. We gathered information on 185 species, of which 65% (121) nested, 10% (19) probably nested, and 11% (21) were permanent residents in the region. Most breeding or probably breeding forms were of North American (58%; 81) or Beringian (24%; 33) affinity, while the remainder of the species were of Panboreal (17%; 24) and Old World (1%; 2) affinity. Similarly, most of the 44 migrants and visitants were of North American (41%; 18) affinity, while the remainder were of Beringian (32%; 14) and Panboreal (27%; 12) affinity. Of the 140 species that nested or probably nested, 53% (73) were abundant to fairly common, 29% (40) were uncommon to very rare, and 20% (27) were localized. Shrub thicket, dwarf shrub mat, coniferous forest, deciduous forest, mixed deciduous-coniferous forest, and fluviatile water and shoreline habitats supported the greatest diversity of species breeding and suspected of breeding. The highest concentrations of birds occurred in the estuaries of Nanvak, Chagvan, and Goodnews bays during spring and fall migrations and on the coastal and island cliffs during the breeding season. The information presented here provides the basis for range extensions of several species. Our records further clarify the known or probable Alaska breeding ranges of 11 species (fork-tailed storm-petrel, Oceanodroma furcata ; double-crested cormorant, Phalacrocorax auritus ; red-faced cormorant, Phatacrocorax utile , brant, Branta bernicla ; king eider, Somateria spectabilis ; white-tailed ptarmigan, Lagopus leucurus ; black-bellied plover, Pluvialis squatarola ; Pacific golden-plover, Pluvialis fulva ; lesser yellowlegs, Tringa flavipes ; Say's phoebe, Sayomis saya ; and Bohemian waxwing, Bombycilla garrulus ). We also provide further information on distributions or documentation of unusual occurrences for nine taxa (frigatebird, Fregata spp.; Baikal teal, Anas formosa ; American kestrel, Falco sparverius ; Terek sandpiper, Xenus cinereus ; bristle-thighed curlew, Numenius tahitiensis ; slaty-backed gull, Larus schistisagus ; rufous hummingbird, Selasphorus rufus ; song sparrow, Melospiza melodia ; and red-winged blackbird, Agelaius phoeniceus ). We provide quantitative data on the coastal migration of 11 species along Bristol Bay (red-throated loon, Gavia stellata ; Pacific loon, Gavia pacifica ; pelagic cormorant, Phalacrocorax pelagicus ; emperor goose, Chen canagica ; brant; Steller's eider, Polysticta stellen ; common eider, Somateria mollissima ; king eider; black scoter, Melanina nigra ; white-winged scoter, Melanina fusca ; and surf scoter, Melanina perspicillatd ). We document changes in nesting densities, differences in numbers, or habitat variations of 32 species in response to human activities (e.g., semipalmated plover, Charadrius semipalmatus ; arctic tern, Sterna paradisaea ; tree swallow, Tachycineta bicolor , varied thrush, Ixoreus naevius ; yellow-rumped warbler, Dendroica coronata ; and American tree sparrow, Spizella arborea ). We report the changes in a major colony of Aleutian terns ( Sterna aleatico ) at irregular intervals over 50 years.

Alaska↗
USGS2015

Southern Salish Sea Habitat Map Series: Admiralty Inlet

In 2010 the Environmental Protection Agency, Region 10 initiated the Puget Sound Scientific Studies and Technical Investigations Assistance Program, designed to support research in support of implementing the Puget Sound Action Agenda. The Action Agenda was created in response to Puget Sound having been designated as one of 28 estuaries of national significance under section 320 of the U.S. Clean Water Act, and its overall goal is to restore the Puget Sound Estuary's environment by 2020. The Southern Salish Sea Mapping Project was funded by the Assistance Program request for proposals process, which also supports a large number of coastal-zone- and ocean-management issues. The issues include the recommendations of the Marine Protected Areas Work Group to the Washington State Legislature (Van Cleve and others, 2009), which endorses a Puget Sound and coast-wide marine conservation needs assessment, gap analysis of existing Marine Protected Areas (MPA) and recommendations for action. This publication is the first of four U.S. Geological Survey Scientific Investigation Maps that make up the Southern Salish Sea Mapping Project. The remaining three map blocks to be published in the future, located south of Admiralty Inlet, are shown in figure 1. Puget Sound is a deep, fjord-type estuary covering an area of 2,330 km 2 in the Pacific Northwest region of the United States (fig. 1). It is connected to the ocean by the Strait of Juan de Fuca, a turbulent passage approximately 160 km in length and 22 km wide at its west end, expanding to over 40 km wide at its east end (Thomson, 1994). During the Pleistocene, the area was occupied several times by lobes of continental ice, resulting in a complex basin-fill of glacial and interglacial deposits that are locally as thick as 1100 m (Johnson and others, 2001). The last glaciation, called the Fraser glaciation, began after 28,800±740 14 C yr B.P. when ice started a slow expansion (Clague, 1981). At peak advance the westward Juan de Fuca lobe reached the edge of the continental shelf through the Juan de Fuca Strait shortly before 14,460±200 14 C yr B.P. (Herzer and Bornhold, 1982). The southward Puget lobe advanced to its terminal position in Puget Sound by around 14,150 14 C yr B.P. (Porter and Swanson, 1998). Ice retreated from its maximum to northern Whidbey Island by 13,650±350 14 C yr B.P. (Dethier and others, 1995). Retreating glaciers resulted in a thick sequence of ice-contact, glacial-marine sediment, and early post-glacial sediments (Linden and Schurrer, 1988). These deposits have experienced the effects of a marine transgression followed by regression, resulting in a sea-level several tens of meters lower than the present day (Linden and Schurrer, 1988). A second transgression brought sea level to about the present level by around 5,470±120 14 C yr B.P. (Clague and others, 1982) establishing the present oceanographic and geologic environment Puget Sound is separated into four interconnected basins; Whidbey, Central (Main), Hood Canal, and South (Thomson, 1994). The Whidbey, Central, and Hood Canal basins are the three main branches of the Puget Sound estuary and are separated from the Strait of Juan de Fuca by a double sill at Admiralty Inlet. The Admiralty Inlet map area includes the Inlet and a portion of the Whidbey Basin (fig. 1). The shallower South Basin is separated by a sill at Tacoma Narrows and is highly branched with numerous finger inlets. Flow within Puget Sound is dominated by tidal currents of as much as 1 m/s at Admiralty Inlet, reducing to approximately 0.5 m/s in the Central Basin (Lavelle and others, 1988). The lack of silt and clay-sized sediments in the Admiralty Inlet map area is likely a result of the strong currents (see Ground-Truth Studies for the Admiralty Inlet Map Area, sheet 3). The subtidal component of flow reaches approximately 0.1 m/s and is driven by density gradients arising from the contrast in salty ocean water at the entrance and freshwater inputs from stream flow (Lavelle and others, 1988). The total freshwater input to Puget Sound is approximately 3.4 x 10 6 m 3 /day, primarily from the Skagit River (Cannon, 1983). The subtidal circulation mostly consists of a two-layered flow in the basins with fresher water exiting at the surface and saltier water entering at depth (Ebbesmeyer and Cannon, 2001). In general, surface waters flow north and deeper waters flow south; variations arise from wind effects that can drive a surface current in the same direction as the wind, and a baroclinic response in the lower layer to about 100-m depth (Matsuura and Cannon, 1997). Oceanographic properties are influenced by temporal forcing parameters such as reduced stream flow during the 2000-01 drought that increased surface salinity and decreased differences between surface and bottom waters (Newton and others, 2003). On offshore seismic-reflection profiles, Pleistocene strata (excluding latest Pleistocene glacial and post-glacial deposits) form a distinct seismic unit, bounded below by pre-Tertiary or Tertiary basement and above by typically flat-lying latest Pleistocene to Holocene deposits that fill in erosional or depositional relief (Johnson and others, 2001). Cores from central Puget Sound have accumulation rates that range from 85 to 1200 mg/cm 2 /yr, or 0.12 to 2.4 cm/yr; the highest accumulation rates are near the southern end of central Puget Sound (Carpenter and others, 1985). Carpenter and others (1985) un-weighted arithmetic mean of accumulation rates for central Puget Sound deeper stations is 480±340 (± one standard deviation) mg/cm 2 /yr. Lavelle and others (1985) also found rates as high as 1200 mg/cm 2 /yr over the past approximately 70 years in cores in the Central Basin off of and north and south of Elliott Bay. Puget Sound basin rates are comparable to rates in midshelf silt deposits on the Washington coast north of the Columbia River (Nittrouer and others, 1979). The deep subtidal (in other words, below SCUBA depths) habitats of Puget Sound are relatively poorly known. A few subtidal surveys exist for several habitat types from the 1960s and 1970s (reviewed in Dethier, 1990), using grab and box core data. The Dethier (1990) review divides habitat up into Coast and Marine Ecological Classification Standard (CMECS) substrate, water column energy, and depth zones but does not attempt to map these habitats, rather it is an inventory of habitats found in the area and the flora and fauna associated with each habitat. The approach of the Southern Salish Sea Mapping project is to create highly detailed seafloor maps through collection, integration, interpretation, and visualization of swath sonar data (the undersea equivalent of satellite remote-sensing data in terrestrial mapping), acoustic backscatter, seafloor video, seafloor photography, and bottom-sediment sampling data. This approach is based in part on methods presented and data collection and product needs identified at the Washington State Seafloor Mapping Workshop (Washington State Seafloor Mapping Workshop Steering Committee, 2008), attended by coastal and marine managers and scientists. The map products display seafloor geomorphology and substrate, and identify potential marine benthic habitats. It is emphasized that the more interpretive habitat and geology maps rely on the integration of multiple, new high-resolution datasets and that mapping at small scales would not be possible without such data. Oceanographic current and wave data is not included in this analysis, however, the accompanying geographic information system (GIS) data set is designed and intended to be combined with oceanographic and biologic data sets assembled by others in the future and some of the GIS data has already been incorporated in the unpublished Nature Conservancy Benthic Habitats of Puget Sound database. This publication includes four map sheets, explanatory text, and a descriptive pamphlet. Each map sheet is published as a portable document format (PDF) file. ESRI ArcGIS compatible geotiffs (for example, bathymetry) and shapefiles (for example video observation points) will be available for download in the data catalog associated with this publication (Cochrane, 2015). An ArcGIS Project File with the symbology used to generate the map sheets is also provided. For those who do not own the full suite of ESRI GIS and mapping software, the data can be read using ESRI ArcReader, a free viewer that is available at http://www.esri.com/software/arcgis/arcreader/index.html .

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