ALBERT

Beschreibung / Inhaltsverzeichnis: Hydrogeologic setting -- Mine flooding and aftermath -- Flooding and formation of rubble chimneys -- Water-level recovery and migration of brine -- Interception of brine and saline water -- Geochemical modeling -- Inverse models -- Forward models -- Discussion of results from geochemical modeling -- Simulated migration of brine and saline water during recovery of water levels -- One-dimensional flow -- Three-dimensional flow -- Model design -- Model calibration -- Model results -- Discussion of results -- Simulated pumping of brine and saline water -- Model design -- Model results -- Model sensitivity -- Discussion of results -- Implications for future mitigation efforts -- Current conditions in the collapse area -- Considerations for future mitigation

Beschreibung / Inhaltsverzeichnis: Augustine Island (volcano) in lower Cook Inlet, Alaska, has erupted repeatedly in late-Holocene and historical times. Eruptions typically beget high-energy volcanic processes. Most notable are bouldery debris avalanches containing immense angular clasts shed from summit domes. Coarse deposits of these avalanches form much of Augustines lower flanks. A new geologic map at 1:25,000 scale depicts these deposits, these processes. We correlate deposits by tephra layers calibrated by many radiocarbon dates.Augustine Volcano began erupting on the flank of a small island of Jurassic clastic-sedimentary rock before the late Wisconsin glaciation (late Pleistocene). The oldest known effusions ranged from olivine basalt explosively propelled by steam, to highly explosive magmatic eruptions of dacite or rhyodacite shed as pumice flows. Late Wisconsin piedmont glaciers issuing from the mountainous western mainland surrounded the island while dacitic eruptive debris swept down the south volcano flank.

Beschreibung / Inhaltsverzeichnis: A new map of standardized, mesoscale (tens to thousands of hectares) terrestrial ecosystems for the conterminous United States was developed by using a biophysical stratification approach. The ecosystems delineated in this top-down, deductive modeling effort are described in NatureServe's classification of terrestrial ecological systems of the United States. The ecosystems were mapped as physically distinct areas and were associated with known distributions of vegetation assemblages by using a standardized methodology first developed for South America. This approach follows the geoecosystems concept of R.J. Huggett and the ecosystem geography approach of R.G. Bailey.Unique physical environments were delineated through a geospatial combination of national data layers for biogeography, bioclimate, surficial materials lithology, land surface forms, and topographic moisture potential. Combining these layers resulted in a comprehensive biophysical stratification of the conterminous United States, which produced 13,482 unique biophysical areas. These were considered as fundamental units of ecosystem structure and were aggregated into 419 potential terrestrial ecosystems.

Beschreibung / Inhaltsverzeichnis: Comparing altered wetlands to natural wetlands in the same region improves the ability to interpret the gradual and cumulative effects of human development on freshwater wetlands. Hydrologic differences require explicit attention because they affect nearly all wetland functions and are an overriding influence on other comparisons involving wetland water quality and ecology. This study adopts several new approaches to quantify wetland hydrologic characteristics and then describes and compares the hydrology, water quality, and ecology of 10 isolated freshwater marsh and cypress wetlands in the mantled karst landscape of central Florida. Four of the wetlands are natural, and the other six have water levels indirectly lowered by ground-water withdrawals on municipally owned well fields. For several decades, the water levels in four of these altered wetlands have been raised by adding ground water in a mitigation process called augmentation. The two wetlands left unaugmented were impaired because their water levels were lowered. Multifaceted comparisons between the altered and natural wetlands are used to examine differences between marshes and cypress wetlands and to describe the effects of augmentation practices on the wetland ecosystems.

Beschreibung / Inhaltsverzeichnis: The southern Española basin consists of a westward- and northward-thickening wedge of rift fill, composed primarily of Santa Fe Group sediments, that serves as an important aquifer for the city of Santa Fe and surrounding areas. Detailed aeromagnetic surveys were flown to better understand ground-water resources in this aquifer. This report presents a synthesis of these data with gravity data and other constraints. The interpretations were accomplished using qualitative interpretation, state-of-art data analysis techniques, and two- and three-dimensional modeling. The results depict the presence of and depth to many geologic features that have hydrogeologic significance, including shallow faults, different types of igneous units, and basement rocks. The results are presented as map interpretations, geophysical profile models, and a digital surface that represents the base and thickness of Santa Fe Group sediments, as well as vector files of some volcanic features and faults.

Beschreibung / Inhaltsverzeichnis: Modern concepts on processes of seismically active parts of converging plate interfaces are derived from lab experiments, theoretical inferences, and geophysical observations, which have either poor resolution, or are strongly dependent on insufficiently constrained assumptions. Therefore, we studied a continuous exposure of an ancient subduction channel in the depth range of its former seismogenic zone in the Central Alps of Europe. This subduction channel developed due to Late Cretaceous - Early Tertiary subduction and accretion of the South Penninic lower plate underneath the Adriatic upper plate (Austroalpine domain). Additionally, we include information from Southern Chile, where material, which formerly underwent deformation within a subduction channel, was exhumed to the surface by large scale basal accretion. There, we concentrated on the formation of mineralized vein systems. However, we mainly focused on the exhumed plate interface zone in the European Alps. During subduction of the South Penninic ocean, material from both the continental upper plate and the oceanic lower plate was progressively involved into the subduction factory and transported downwards, forming either the shaly and serpentinic matrix of the subduction mélange, or competent clasts. Rb/Sr deformation ages for mylonitized rocks of the South Penninic mélange and for deformed Austroalpine basement shed light on the pre-Alpine and Alpine deformation history along the suture, as well as on the mode of syn-subduction interplate mass transfer. According to our Rb/Sr deformation ages and our structural data, the latest increment of subduction-related deformation occurred at ~50 Ma, and is characterized by a roughly top-W direction of tectonic transport. Identical Rb/Sr ages for pervasively deformed Austroalpine and South Penninic rocks point to tectonic erosion of the upper plate during subduction. This is also evidenced by the presence of upper plate clasts in the subduction mélange, and from the syn-subduction evolution of Gosau forearc basins pointing to tectonic erosion as prevailing mass transfer mode during the time of subduction. Lack of a metamorphic contrast between the South Penninic mélange and the Austroalpine upper plate favors exhumation of the suture zone due to a combination of tectonic underplating and surface erosion. The end of sedimentation in the forearc Gosau basins is contemporaneous with basal accretion of the South Penninic mélange and the Middle Penninic units at ~50 Ma. Therefore, we hypothesize a causal link of both processes, with the change from tectonic erosion to basal accretion caused by underplating of subducted material, which is responsible for a regional uplift leading to inversion of the forearc basins. The end of subduction-related deformation is most likely caused by locking of the South Penninic paleosubduction interface due to underplating of the Middle Penninic micro-continent, so that the active subduction interface is relocated into the new Middle Penninic footwall. Pseudotachylytes along a restricted segment of the upper plate base delineated by ca. 200°C updip and ca. 300°C downdip - define the limits of the unstable slip region within the fossil seismogenic coupling zone. Our 40Ar/39Ar ages constrain the generation of pseudotachylytes during a time span between 60 Ma to 80 Ma. The heterogeneous texture of the ultra fine grained pseudotachylyte groundmass is composed of a mixture of amphibole, feldspar and biotite, as well as of incorporated rock fragments and single minerals of comparable size. Due to the temporal similarity between subduction and pseudotachylyte formation, and the fact that the pseudotachylytes occur subparallel to the main thrust where Austroalpine rocks were overthrust onto South Penninic rocks, we interpret the generation of pseudotachylytes to be related to unstable slip processes occurring along the plate interface zone during subduction.The zone of unstable slip coincides with a domain of intense formation of foliation-parallel mineralized veins with partly blocky minerals in the subduction mélange. We suggest that the mineralized veins reflect seismic failure in the mélange due to their similarity in spatial distribution and textures compared to pseudotachylytes. Mineralized veins, and brittle fractures continue into the conditionally stable region below, maybe indicating a domain of slow earthquakes and non-volcanic tremors as recently discovered for this depth range along many active convergent margins. The conditionally stable zone above the unstable slip area is devoid of mineralized veins, but displays ample evidence of fluid-assisted processes like the deeper zone: solution-precipitation creep and dehydration reactions in the mélange matrix, hydration and sealing of the base of the upper plate. Seismic rupture is possibly expressed by ubiquitous localized deformation zones. Fluids are most likely provided by dehydration during subduction of sedimentary material from different sources. This is indicated by elevated Sr isotope signatures of marine (meta-) carbonates from the South Penninic mélange, which are caused by the interaction of syn-subduction fluids with old continental crust.In summary, the exposed plate interface has experienced flow and fracturing over an extended period of time reflecting a multistage evolution, but resembles active convergent plate margins in terms of e.g. sediment input, earthquake distribution, fluid circulation, and possible slow slip events and associated tremors.

Beschreibung / Inhaltsverzeichnis: The Gogebic iron range is an elongate belt of Paleoproterozoic strata extending from the west shore of Lake Gogebic in the upper peninsula of Michigan for about 125 km westward into northern Wisconsin. It is one of six major informally named iron ranges in the Lake Superior region and produced about 325 million tons of direct-shipping ore between 1887 and 1967. A significant resource of concentrating-grade ore remains in the western and eastern parts of the range.The iron range forms a broad, gently southward-opening arc where the central part of the range exposes rocks that were deposited somewhat north of the eastern and western parts. A fundamental boundary marking both the tectonic setting of deposition and the later deformation within the Penokean orogen lies fortuitously in an east-west direction along the range so that the central part of the range preserves sediments deposited north of that boundary, whereas the eastern and western parts of the range were deposited south of the boundary. Thus, the central part of the range provides a record of sedimentation and very mild deformation in a part of the Penokean orogen farthest from the interior of the orogen to the south. The eastern and western parts of the range, in contrast, exhibit a depositional and deformational style typical of parts closer to the interior of the orogen. A second fortuitous feature of the iron range is that the entire area was tilted from 40° to 90° northward by Mesoproterozoic deformation so that the map view offers an oblique cross section of the Paleoproterozoic sedimentary sequence and structures. Together, these features make the Gogebic iron range a unique area in which to observe (1) the lateral transition from deposition on a stable platform to deposition in a tectonically and volcanically active region, and (2) the transition from essentially undeformed Paleoproterozoic strata to their folded and faulted equivalents.

Beschreibung / Inhaltsverzeichnis: We have used terrestrial cosmogenic nuclides (TCN) to establish the age of some of the most extensive Quaternary alluvial fans in Death Valley, California. These intermediate-age alluvial fans are most extensive on the western side of the valley, where tectonic deformation is considerably less pronounced than on the eastern side of the valley. These fans are characterized by a relatively smooth, densely packed desert pavement formed by well-varnished (blackened) clasts. These surfaces have been mapped as the Q2 gravel by previous workers and as unit Qai (intermediate age) by us. However, the intermediate-age gravels probably contain multiple subunits, as evidenced by slight differences in morphologic expression, soil formation, and inset geomorphic relations. The TCN technique used herein sums the cosmogenic 36Cl in approximately 2.5-meter-deep profiles through soil and host alluvium, thus avoiding some of the problems associated with the more typical surface-exposure dating of boulders or smaller clasts.

Beschreibung / Inhaltsverzeichnis: Excessive nutrient [phosphorus (P) and nitrogen (N)] input from point and nonpoint sources is frequently associated with degraded water quality in streams and rivers. Point-source discharges of nutrients are fairly constant and are controlled by the U.S. Environmental Protection Agency's (USEPA) National Pollutant Discharge Elimination System. To reduce inputs from nonpoint sources, agricultural performance standards and regulations for croplands and livestock operations are being proposed by various States. In addition, the USEPA is establishing regionally based nutrient criteria that can be refined by each State to determine whether actions are needed to improve water quality. More confidence in the environmental benefits of the proposed performance standards and nutrient criteria would be possible with improved understanding of the biotic responses to a range of nutrient concentrations in different environmental settings.

Beschreibung / Inhaltsverzeichnis: Professional Paper 1746 (this book) is the second of the three books; it is being published in both English and Icelandic editions. This book provides information about all named glaciers in Iceland, historic and modern. Descriptions, with geographic coordinates, and bibliographic citations to all glacier place-names on published maps, books, and scientific articles are included. Maps, oblique aerial photographs, ground photographs, and satellite images document each of the 269 modern named glaciers of Iceland.

Beschreibung / Inhaltsverzeichnis: The Uncompahgre mining district, part of the Ouray mining district, includes an area of about 15 mi2 on the northwestern flank of the San Juan Mountains in southwestern Colorado from which ores of gold, silver, copper, lead, and zinc have had a gross value of $14 to 15 million.Bedrock within the district ranges in age from Proterozoic to Cenozoic. At least three major uplifts of the ancestral San Juan Mountains occurred during the Proterozoic and at the close of the Paleozoic and Mesozoic, respectively. The last event, known as the Laramide orogeny, locally was accompanied by extensive intrusion of igneous rocks.The principal ore deposits of the district were associated with crosscutting and laccolithic intrusions of porphyritic granodiorite formed during the Laramide orogeny. The ores were deposited chiefly in Paleozoic and Mesozoic sedimentary strata. Ore deposits range from low-grade, contact-metamorphic through pyritic base-metal bodies containing silver and gold tellurides and native gold to silver-bearing lead-zinc deposits.

Beschreibung / Inhaltsverzeichnis: The styles of deformation of the fore-arc wedges along the Chilean convergent margin are observed to vary significantly, despite similar plate kinematic conditions. Here, I focus on the analysis of fore-arc deformation on two regions along the Chilean convergent margin at 20°-24°S and 37°-42°S. Although both regions are subjected to the oblique subduction of the oceanic Nazca plate and backstopped by the Andes mountain chain; they display different patterns of deformation. The northern Chilean study area (20° - 24°S) is characterized by an exceptionally thick crust of about 60 km beneath the Altiplano Puna plateau, lack of an accretionary wedge in the fore-arc due to hyperarid climate, and consequently a sediment starved trench. Two major margin parallel strike slip faults are observed in this area, the Atacama Fault Zone (AFZ) and the Precordilleran Fault System (PFS). Both strike-slip faults do not exhibit significant recent displacement. The southern study area (37° - 42°S), compared to the northern study area, is characterized by lower topography, high precipitation rates (~2000 mm/yr), and a younger subducted oceanic plate. An active strike-slip fault, the Liquine-Ofqui-Fault-Zone (LOFZ), shows ~1 cm/yr recent dextral movement and shapes the surface of this area. Thus, the southern Chilean study area exhibits localized strike-slip motion. Within this area the largest earthquake ever recorded, the 1960 Valdivia earthquake, occurred with a moment magnitude of MW=9.5. I have constructed 2D thermal models and 3D mechanical models for both Chilean study areas to study processes related to active subduction. The applied numerical method is the finite element technique by means of the commercial software package ABAQUS.The thermal models are focused on the thermal conditions along the plate interface. The thermal structure along the plate interface reveals the limits of coupling but also the type of transition from coupled to uncoupled and vice versa. The model results show that shear heating at the plate interface is an important mechanism that should be taken into account. The models also show that the thermal condition at the downdip limit of the coupling zone leads to a sharp decrease of friction along the interface. Due to the different geometries of the two Chilean study areas, such as the slab dip and the thickness of the continental crust, the downdip limit of the southern study area is slightly shallower than that of the northern study area. The results of the 2D thermal models are used to constrain the spatial extent of the coupling zone in the 3D mechanical models. 3D numerical simulations are used to investigate how geometry, rheology and mechanical parameters influence strain partitioning and styles of deformation in the Chilean fore-arc. The general outline of the models is based on the fore-arc geometry and boundary conditions as derived from geophysical and geological field data. I examined the influence of different rheological approaches and varying physical properties of the fore-arc to identify and constrain the parameters controlling the difference in surface deformation between the northern and southern study area. The results of numerical studies demonstrate that a small slab dip, a high coefficient of basal friction, a high obliquity of convergence, and a high Young's modulus favour localisation of deformation in the fore-arc wedge. This parameter study helped me to constrain preferred models for the two Chilean study areas that fit to first order observations. These preferred models explain the difference in styles of deformation as controlled by the angle of obliquity, the dip of subducting slab, and the strength of wedge material. The difference in styles can be even larger if I apply stronger coupling between plates within the southern area; however, several independent observations indicate opposite tendency showing southward decrease of intensity of coupling. The weaker wedge material of the preferred model for the northern study area is associated with advanced development of the adjacent orogen, the Central Andes. Analysis of world-wide examples of oblique subduction zones supports the conclusion that more mature subduction zones demonstrate less pronounced localization of strike-slip motion.

Beschreibung / Inhaltsverzeichnis: Earthquakes pose a serious hazard for urban areas of the Pacific Northwest. Marine geophysical data probe earthquake source regions and can help spur preparedness for possible major disasters.