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USGS1993

Chapter 6: Chronology of displacement on the San Andreas fault in central California: Evidence from reversed positions of exotic rock bodies near Parkfield, California

This chapter presents a synthesis of data pertaining to post-early Miocene slip on the San Andreas fault in central California and suggests a three-phase evolition of the San Andreas system. The cricial evidence that supports the three phases of evolution conies from the reversed positions of two exotic rock fragments in the vicinity of Parkfield, California. The three-phase evolution of the San Andreas is also supported by the correlation of other exotic fragments, the basement rocks on which they lie, overlying Tertiary stratigraphic sequences, and distinctive Miocene strata derived from these fragments during their transport along the fault. The 40-km-long section of the San Andreas fault near Parkfield is characterized by exotic blocks composed of Cretaceous hornblende quartz gabbro at Gold Hill and lower Miocene volcanic rocks in Lang Canyon. The gabbro is correlated petrographically with similar rocks near Eagle Rest Peak, 145 km to the southeast, and near Logan, 165 km to the northwest. The lower Miocene volcanic rocks, informally termed the volcanic rocks of Lang Canyon, are correlated with the Neenach Volcanics 220 km to the southeast and the Pinnacles Volcanics 95 km to the northwest. All three fragments of volcanic rocks are unconformably overlain by similar successions of Tertiary sedimentary rocks. The original positions of the bodies of gabbro and volcanic bodies and their overlying sedimentary cover may be reconstructed from these exotic fragments that now lie along the San Andreas fault between San Juan Bautista and the northwestern Mojave Desert. The original undeformed gabbroic body was composed of the hornblende quartz gabbro of Eagle Rest Peak, Gold Hill, and Logan. In its initial prefaulted position, the original gabbroic body lay about 55 km northwest of the early Miocene volcanic assemblage. The undeformed volcanic assemblage was composed of the Neenach Volcanics, Pinnacles Volcanics, and volcanic rocks of Lang Canyon. The original spatial relationship between the undeformed gabbro and volcanic assemblage and their sedimentary cover is preserved in the present position of the gabbro of Logan and the Pinnacles Volcanics. However, in the Parkfield segment of the San Andreas, the gabbro of Gold Hill lies east of the main trace of the San Andreas fault, and the volcanic rocks of Lang Canyon lie 2 km west of the fault. The reversed relative positions of the gabbro of Gold Hill and the volcanic rocks of Lang Canyon suggest a complex history of movement on the San Andreas fault. Consequently, plainspastic reconstruction of these bodies and their overlying sedimentary cover is constrained by the unusual distribution of exotic blocks near Parkfield. The resulting proposed history of movement is divided into three stages that begins with the eruption of the early Miocene volcanic rocks about 24 Ma. The Neenach-Pinnacles Volcanics, erupted after passage of the Mendocino triple junction, were soon cut by the growing San Andreas transform system. During the first phase of movement the Salinian block, which contains the Pinnacles and Logan godies, was detached from the Mojave and Sierran blocks. The Pinnacles and Logan bodies were transported about 95 km northwest from the Neenach Volcanics and the gabbro of Eagle Rest Peak. At the end of the first phase, the Logan and Pinnacles fragments lay adjacent to the west side of what is now the San Joaquin Valley. Concurrently, fan-deltas deposited debris that was derived from the Gabilan Range, the fan-deltas spread across the San Andreas fault into the middle Miocene sea in the San Joaquin trough. During the second phase of movement, the San Andreas—at least locally—stepped eastward and detached a second fragment from the Neenach Volcanics. This fragment consists of the volcanic rocks of Lang Canyon. Slip was transferred to the new trace of the San Andreas fault, and the older trace became completely or largely inactive. After transferral of slip to the new trace of the San Andreas fault, the volcanic rocks of Lang Canyon and the Pinnacles Volcanics remained about 95 km apart on the Salinian Block west of the San Andreas fault. During the third phase, the Gold Hill fragement was slivered off the Logan fragment and was tectonically emplaced on the east side of the San Andreas fault when the Logan fragment lay at the latitude of Gold Hill. The process of slivering off of the Gold Hill fragment was accomplished by deformation of the San Andreas in an eastward bend along what is now the Jack Ranch fault. Bending of the fault was stimulated by the presence of highly sheared Franciscan rocks that crop out near the San Andreas and extend to great depth. Eventually the San Andreas bent to such a degree that slip could not be conducted around the bend, and a new, stable, straight segment was formed. The straightening of the fault resulted in slivering of the Gold Hill fragment from the Logan fragment. After detachment of the Gold Hill fragment, the Salinian block containing the gabbro of Logan, the Pinnacles Volcanics, and the volcanic rocks of Lang Canyon was transported an additional 160 km northwest to its present position. This reconstruction honors the current positions of all the related exotic fragments of gabbro, volcanics, and sedimentary rocks. The timing of the sequence of movements required to reconstruct the original bodies suggests that the three phases of evolution of the San Andreas fault in central California are characterized by increasing slip rates. The rate for the first phase probably averaged about 10 mm/yr over a period of about 8 m.y. The rate for the second phase averaged about 8 mm/yr over a period of about 7 m.y. The rate rate for the third phase averaged about 33 mm/yr over a period of about 5 m.y.

California↗
USGS2008

Genetic characterization of Hawaiian isolates of Plasmodium relictum reveals mixed-genotype infections

Background: The relatively recent introduction of a highly efficient mosquito vector and an avian pathogen (Plasmodium relictum) to an isolated island ecosystem with nai??ve, highly susceptible avian hosts provides a unique opportunity to investigate evolution of virulence in a natural system. Mixed infections can significantly contribute to the uncertainty in host-pathogen dynamics with direct impacts on virulence. Toward further understanding of how host-parasite and parasite-parasite relationships may impact virulence, this study characterizes within-host diversity of malaria parasite populations based on genetic analysis of the trap (thrombospondin-related anonymous protein) gene in isolates originating from Hawaii, Maui and Kauai Islands. Methods: A total of 397 clones were produced by nested PCR amplification and cloning of a 1664 bp fragment of the trap gene from two malarial isolates, K1 (Kauai) and KV115 (Hawaii) that have been used for experimental studies, and from additional isolates from wild birds on Kauai, Maui and Hawaii Islands. Diversity of clones was evaluated initially by RFLP-based screening, followed by complete sequencing of 33 selected clones. Results: RFLP analysis of trap revealed a minimum of 28 distinct RFLP haplotypes among the 397 clones from 18 birds. Multiple trap haplotypes were detected in every bird evaluated, with an average of 5.9 haplotypes per bird. Overall diversity did not differ between the experimental isolates, however, a greater number of unique haplotypes were detected in K1 than in KV115. We detected high levels of clonal diversity with clear delineation between isolates K1 and KV115 in a haplotype network. The patterns of within-host haplotype clustering are consistent with the possibility of a clonal genetic structure and rapid within-host mutation after infection. Conclusion: Avian malaria (P. relictum) and Avipoxvirus are the significant infectious diseases currently affecting the native Hawaiian avifauna. This study shows that clonal diversity of Hawaiian isolates of P. relictum is much higher than previously recognized. Mixed infections can significantly contribute to the uncertainty in host-pathogen dynamics with direct implications for host demographics, disease management strategies, and evolution of virulence. The results of this study indicate a widespread presence of multiple-genotype malaria infections with high clonal diversity in native birds of Hawaii, which when coupled with concurrent infection with Avipoxvirus, may significantly influence evolution of virulence. ?? 2008 Jarvi et al; licensee BioMed Central Ltd.

Biology Direct↗
USGS2023

Coevolution with host fishes shapes parasitic life histories in a group of freshwater mussels (Unionidae: Quadrulini)

Ecological interactions among species often lead to parasitic lineages coevolving with host resources, which is often suggested as the primary driver of parasite diversification. Freshwater mussels are bivalves that possess a parasitic life cycle requiring larval encystment on freshwater vertebrates to complete metamorphosis. The North American freshwater mussel tribe Quadrulini has a suite of life history adaptations including highly specialized patterns of host use, infection strategies, and variable larval morphologies. However, the evolution of life histories has yet to be explored using phylogenetic comparative methods. In this study, we use a holistic approach incorporating biogeographical, ecological, molecular, and morphological datasets to reconstruct the evolution of Quadrulini. Comparative phylogenetic analyses suggested the diversification of Quadrulini has been driven, at least in part, by codiversification with their primary host fishes in Ictaluridae. Major diversification events in both ictalurids and quadrulines were estimated to have occurred in the Mississippi River basin throughout the Miocene. Life history characteristics associated with parasitism were supported to have coevolved with host repertories, supporting the hypothesis that ecological interactions with host fishes have shaped the evolution of highly specialized traits in this group. Our findings demonstrate the importance of ecological interactions with host resources in shaping the evolutionary history of freshwater mussels.

Bulletin of the Society of Systematic Biologists↗
USGS2013

Assessing grain-size correspondence between flow and deposits of controlled floods in the Colorado River, USA

Flood-deposited sediment has been used to decipher environmental parameters such as variability in watershed sediment supply, paleoflood hydrology, and channel morphology. It is not well known, however, how accurately the deposits reflect sedimentary processes within the flow, and hence what sampling intensity is needed to decipher records of recent or long-past conditions. We examine these problems using deposits from dam-regulated floods in the Colorado River corridor through Marble Canyon–Grand Canyon, Arizona, U.S.A., in which steady-peaked floods represent a simple end-member case. For these simple floods, most deposits show inverse grading that reflects coarsening suspended sediment (a result of fine-sediment-supply limitation), but there is enough eddy-scale variability that some profiles show normal grading that did not reflect grain-size evolution in the flow as a whole. To infer systemwide grain-size evolution in modern or ancient depositional systems requires sampling enough deposit profiles that the standard error of the mean of grain-size-change measurements becomes small relative to the magnitude of observed changes. For simple, steady-peaked floods, 5–10 profiles or fewer may suffice to characterize grain-size trends robustly, but many more samples may be needed from deposits with greater variability in their grain-size evolution.

Journal of Sedimentary Research↗
USGS2021

Formation of miarolitic-class, segregation-type pegmatites in the Taishanmiao batholith, China: The role of pressure fluctuations and volatile exsolution during pegmatite formation in a closed, isochoric system

The Taishanmiao granitic batholith, located in the Eastern Qinling Orogen in Henan Province, China, contains numerous small (mostly tens of centimeters in maximum dimension) bodies exhibiting textures and mineralogy characteristics of simple quartz and alkali feldspar pegmatites. Analysis of melt inclusions (MI) and fluid inclusions (FI) in pegmatitic quartz, combined with Rhyolite-MELTS modeling of the crystallization of the granite, have been applied to develop a conceptual model of the physical and geochemical processes associated with the formation of the pegmatites. These results allow us to consider the formation of the Taishanmiao pegmatites within the context of varios models that have been proposed for pegmatite formation. Field observations and geochemical data indicate that the pegmatites represent the latest stage in the crystallization of the Taishanmiao granite and occupy ≤4 vol% of the syenogranite phase of the batholith. Results of Rhyolite-MELTS modeling suggest that the pegmatite-forming melts can be produced through continuous fractional crystallization of the Taishanmiao granitic magma, consistent with the designation of the pegmatites as a miarolitic class, segregation-type pegmatites rather than the more common intrusive-type of pegmatite. The mineral assemblage predicted by Rhyolite-MELTS after ~96% of the original granite-forming melt had crystallized consists of ~51 vol% alkali feldspar, 34 vol% quartz, 14 vol% plagioclase, 0.1 vol% biotite, and 1 vol% magnetite, similar to the alkali feldspar + quartz dominated mineralogy of the pegmatites. Moreover, the modeled residual melt composition following crystallization of ~96% of the original melt is similar to the composition of homogenized MI in quartz within the pegmatite. Rhyolite-MELTS predicts that the granite-forming melt remained volatile-undersaturated during crystallization of the batholith and contained ~6.3 wt% H 2 O and ~500 ppm CO 2 after ~96% crystallization when the pegmatites began to develop. The Rhyolite-MELTS prediction that the melt was volatile-undersaturated at the time the pegmatites began to form, but became volatile-saturated during the early stages of pegmatite formation, is consistent with the presence of some inclusion assemblages consisting of only MI, while others contain co-existing MI and FI. The relationship between halogen (F and Cl) and Na abundances in MI is also consistent with the interpretation that the very earliest stages of pegmatite formation occurred in the presence of a volatile-undersaturated melt and that the melt became volatile saturated as crystallization progressed. We propose a closed system, isochoric model for the formation of the pegmatites. Accordingly, the Taishanmiao granite crystallized isobarically at ~3.3 kbar, and the pegmatites began to form at ~734 °C and ~ 3.3 kbar, after ~96% of the original granitic melt had crystallized. During the final stages of crystallization of the granite, small pockets of the remaining residual melt became isolated within the enclosing granite and evolved as constant mass (closed), constant volume (isochoric) systems, similar to the manner in which volatile-rich melt inclusions in igneous phenocrysts evolve during post-entrapment crystallization under isochoric conditions. As a result of the negative volume change associated with crystallization, pressure in the pegmatite initially decreases as crystals form, and this leads to volatile exsolution from the melt phase. The changing PTX conditions produce a pressure-induced “liquidus deficit” that is analogous to liquidus undercooling and results in crystal growth as required to return the system to equilibrium PTX conditions. Owing to the complex closed system, isochoric PVTX evolution of the melt-crystal-volatile system, the pressure does not decrease rapidly or monotonically during pegmatite formation but, rather, gradually fluctuates such that at some stages in the evolution of the pegmatite the pressure is decreasing while at other times the pressure increases as the system cools to maintain mass and volume balance. This behavior, in turn, leads to alternating episodes of precipitation and dissolution that serve to coarsen (ripen) the crystals to produce the pegmatitic texture. The evolution of the pegmatitic melt described here is analogous to that which has been well-documented to occur in volatile-rich MI that undergo closed system, isochoric, post-entrapment crystallization.

American Mineralogist↗
USGS2009

Approaches to modeling weathered regolith

Sustainable soils are a requirement for maintaining human civilizations ( Carter and Dale 1974 ; Lal 1989 ). However, as the “most complicated biomaterial on the planet” ( Young and Crawford 2004 ), soils represent one of the most difficult systems to understand and model with respect to chemical, physical, and biological coupling over time (Fig. 1 ). Despite the complexity of these interactions, certain patterns in soil properties and development are universally observed and have been used in soil science as a means for classification. Elemental, mineralogical, or isotopic concentrations in soils plotted versus depth beneath the land surface comprise such patterns. Soil depth profiles are often reported for solid soil materials, and, less frequently, for solutes in soil pore waters. These profiles cross a large range in spatial scales that traditionally have been studied by different disciplines. For example, shallow, biologically active horizons are commonly defined as the soil zone in agronomic studies whereas the mobile layer of the regolith is referred to as soil in geomorphological studies. In contrast, many geochemical studies target chemical weathering to tens or even hundreds of meters in depth, sometimes extending the definition of “soils” to include the entire regolith down to parent bedrock or alluvium. Soil profiles also exhibit a large range in temporal scales ( Amundson 2004 ; Brantley 2008b ). Solid-state profiles document chemical and mineralogical changes integrated over the time scales of evolution of regolith from protolith. This “geologic time” can vary from tens to hundreds of years for weathered material developed on moraines deposited by active glaciers ( Anderson et al. 1997 ), to millions or possibly hundreds of millions of years of regolith evolution as documented in laterites and bauxites on stable cratons ( Nahon 1986 ). In contrast, solute profiles reflect much shorter time scales corresponding to the residence time of the soil water which commonly ranges from days to decades ( Stonestrom et al. 1998 ). Factors impacting soil minerals can therefore be related to geologically old processes while those impacting pore waters are related to contemporary processes. We first discuss a geochemical frame work for modeling soil profiles, including a simple scheme that depends on the extent of enrichment or depletion. Such profiles are comprised of reaction fronts affected by chemical, hydrologic, geologic and biologic processes that control soil evolution. We then present a hierarchy of models that have been used to interpret both solid state and solute compositions in regolith. The more simple approaches to model depletion in soils, using analytical models, are first described. The most elementary of these is a linear model that calculates rate constants from the slopes of either solid or solute weathering gradients: these rate constants represent lumped parameters that describe weathering in terms of an integrated reaction rate. Two other analytical models are then presented that have been used to fit solid state elemental profiles with exponential and sigmoidal functions. All of these analytical approaches are derived for models of soils as containing a limited number of components, phases, and species. At a more complex level, numerical models are then presented to elucidate how kinetic and transport parameters as well as chemical, hydrologic, and physical soil data can be incorporated. We consider two forms of these models, first relatively simple spreadsheet calculators and then more sophisticated multi-component, multi-phase reactive-transport numerical codes. Our treatment of reactive transport modeling is relatively cursory, in recognition of the treatment in the chapter by Steefel and Maher (2009 , this volume). Because these models incorporate more phases, components, and species than the other approaches and explicitly model the more fundamental reaction mechanisms involved, they generally have a greater need for parameterization. In our conclusion section, we discuss how this hierarchy of approaches can yield generalizations about soils that are often complementary.

Reviews in Mineralogy and Geochemistry↗
USGS2024

The early Earth as an analogue for exoplanetary biogeochemistry

Planet Earth has evolved over the past 4.5 billion years from an entirely anoxic planet with possibly a different tectonic regime to the oxygenated world with horizontal plate tectonics that we know today. For most of this time, Earth has been inhabited by a purely microbial biosphere albeit with seemingly increasing complexity over time. A rich record of this geobiological evolution over most of Earth’s history thus provides insights into the remote detectability of microbial life under a variety of planetary conditions. Here we leverage Earth’s geobiological record with the aim of (a) illustrating the current state of knowledge and key knowledge gaps about the early Earth as a reference point in exoplanet science research; (b) compiling biotic and abiotic mechanisms that controlled the evolution of the atmosphere over time; and (c) reviewing current constraints on the detectability of Earth’s early biosphere with state-of-the-art telescope technology. We highlight that life may have originated on a planet with a different (stagnant lid) tectonic regime and strong hydrothermal activity, and under these conditions, biogenic CH 4 gas was perhaps the most detectable atmospheric biosignature. Oxygenic photosynthesis, which is responsible for essentially all O 2 gas in the modern atmosphere, appears to have emerged concurrently with the establishment of modern plate tectonics and the emergence of continental crust, but O 2 accumulation to modern levels only occurred late in Earth’s history, perhaps tied to the rise of land plants. Nutrient limitation in anoxic oceans, promoted by hydrothermal Fe fluxes, may have limited biological productivity and O 2 production. N 2 O is an alternative biosignature that was perhaps significant on the redox-stratified Proterozoic Earth. We conclude that the detectability of atmospheric biosignatures on Earth was not only dependent on biological evolution but also strongly controlled by the evolving tectonic context.

Reviews in Mineralogy and Geochemistry↗
USGS1992

Riparian vegetation recovery patterns following stream channelization: A geomorphic perspective

Hundreds of kilometres of West Tennessee streams have been channelized since the turn of the century. After a stream is straightened, dredged, or cleared, basinwide ecologic, hydrologic, and geomorphic processes bring about an integrated, characteristic recovery sequence. The rapid pace of channel responses to channelization provides an opportunity to document and interpret vegetation recovery patterns relative to otherwise long—term, concomitant evolution of river geomorphology. Nearly 150 sites along 15 streams were studied in the Obion, Forked Deer, Hatchie, and Wolf River basins. Channels of these streams, except that of the Hatchie River main stem, have undergone major modifications along all or parts of their courses. This paper presents the eco—geomorphic analyses and interpretation of a large multidisciplinary study, with special reference to their interrelated hydrogeomorphic aspects of channel recovery. Quantitative plant ecological analyses were conducted to infer relative bank stability, to identify indicator recovery species, and to determine patterns of vegetation development through the course of accelerated channel evolution. Binary—discriminant and ordination analyses show that distinctive riparian—species patterns reflect a six—stage model of channel evolution and can be used to infer channel stability and hydrogeomorphic conditions. Woody vegetation initially establishes on low— and mid—bank surfaces at the same location and time that bank accretion begins, and corresponds to the site of initial geomorphic restabilization. The linkage of channel bed aggradation, woody vegetation establishment, and bank accretion all lead to recovery of the channel. Pioneer species are hardy and fast growing, and can tolerate moderate amounts of slope instability and sediment deposition; these species include river birch (Betula nigra), black willow (Salix nigra), boxelder (Acer negundo), and silver maple (Acer saccharinum). High stem densities and root—mass development appear to enhance bank stability. Tree—ring analyses suggest that on average 65 yr may be required for recovery after channelization.

Ecology↗
USGS2017

Coastal bathymetry data collected in 2013 from the Chandeleur Islands, Louisiana

As part of the Barrier Island Evolution Research Project, scientists from the U.S. Geological Survey (USGS) St. Petersburg Coastal and Marine Science Center conducted nearshore geophysical surveys around the northern Chandeleur Islands, Louisiana, in July and August of 2013. The objective of the study is to better understand barrier-island geomorphic evolution, particularly storm-related depositional and erosional processes that shape the islands over annual to interannual timescales (1‒5 years). Collecting geophysical data will allow us to identify relationships between the geologic history of the island and its present day morphology and sediment distribution. This mapping effort was the third in a series of three planned surveys in this area. High resolution geophysical data collected in each of three consecutive years along this rapidly changing barrier island system will provide a unique time-series dataset that will significantly further the analyses and geomorphological interpretations of this and other coastal systems, improving our understanding of coastal response and evolution over short time scales (1‒5 years). This data series includes the geophysical data that were collected during two cruises (USGS Field Activity Numbers (FAN) 13BIM02, 13BIM03, and 13BIM04, in July 2013; and FANs 13BIM07 and 13BIM08 in August 2013) aboard the R/V Sallenger , the R/V Jabba Jaw , and the R/V Shark along the northern portion of the Chandeleur Islands, Breton National Wildlife Refuge, Louisiana. Primary data were acquired with the following equipment: (1) a Systems Engineering and Assessment, Ltd., SWATHplus interferometric sonar (468 kilohertz [kHz]), (2) an EdgeTech 424 (4‒24 kHz) chirp sub-bottom profiling system, and (3) two Odom Hydrographic Systems, Incorporated, Echotrach CV100 single beam echosounders. This data series report serves as an archive of processed interferometric swath and single-beam bathymetry data. Geographic information system data products include an interpolated digital elevation model, trackline maps, and point data files. Additional files include error analysis maps, Field Activity Collection System logs, and formal Federal Geographic Data Committee metadata.

Louisiana↗
USGS2018

Chirp subbottom profile data collected in 2015 from the northern Chandeleur Islands, Louisiana

As part of the Barrier Island Evolution Research project, scientists from the U.S. Geological Survey (USGS) St. Petersburg Coastal and Marine Science Center conducted a nearshore geophysical survey around the northern Chandeleur Islands, Louisiana, in September 2015. The objective of the project is to improve the understanding of barrier island geomorphic evolution, particularly storm-related depositional and erosional processes that shape the islands over annual to interannual time scales (1–5 years). Collecting geophysical data can help researchers identify relations between the geologic history of the islands and their present day morphology and sediment distribution. High-resolution geophysical data collected along this rapidly changing barrier island system can provide a unique time-series dataset to further the analyses and geomorphological interpretations of this and other coastal systems, improving our understanding of coastal response and evolution over medium-term time scales (months to years). Subbottom profile data were collected in September 2015 offshore of the northern Chandeleur Islands, during USGS Field Activity Number 2015-331-FA. Data products, including raw digital chirp subbottom data, processed subbottom profile images, survey trackline map, navigation files, geographic information system data files and formal Federal Geographic Data Committee metadata, and Field Activity Collection System and operation logs are available for download.

Louisiana↗
USGS2001

Coastal vulnerability to sea-level rise: a preliminary database for the U.S. Atlantic, Pacific, and Gulf of Mexico coasts

The prediction of coastal evolution is not straightforward. There is no standard methodology, and even the kind of data required to make such predictions are the subject of much scientific debate. Since a viable, quantitative predictive model for coastal evolution is not available. The relative susceptibility of the Nation's coastline to sea-level rise is quantified here at a regional to national scale using basic information on coastal geomorphology, rate of sea-level rise, past shoreline evolution and other factors. This approach combines the coastal system's susceptibility to change with its natural ability to adapt to changing environmental and conditions, and yields a relative measure of the system's natural vulnerability to the effects of sea-level rise. This information has immediate application to many of the decisions our society will be making regarding coastal development in both the short- and long-term.

Data Series↗
USGS2014

Coastal bathymetry and backscatter data collected in 2012 from the Chandeleur Islands, Louisiana

As part of the Barrier Island Evolution Research Project, scientists from the U.S. Geological Survey St. Petersburg Coastal and Marine Science Center conducted nearshore geophysical surveys off the northern Chandeleur Islands, Louisiana, in July and August of 2012. The objective of the study is to better understand barrier island geomorphic evolution, particularly storm-related depositional and erosional processes that shape the islands over annual to interannual timescales (1-5 years). Collecting geophysical data will allow us to identify relationships between the geologic history of the island and its present day morphology and sediment distribution. This mapping effort was the second in a series of three planned surveys in this area. High resolution geophysical data collected in each of 3 consecutive years along this rapidly changing barrier island system will provide a unique time-series dataset that will significantly further the analyses and geomorphological interpretations of this and other coastal systems, improving our understanding of coastal response and evolution over short time scales (1-5 years). This Data Series report includes the geophysical data that were collected during two cruises ( USGS Field Activity Numbers 12BIM03 and 12BIM04 ) aboard the RV Survey Cat and the RV Twin Vee along the northern portion of the Chandeleur Islands, Breton National Wildlife Refuge, Louisiana. Data were acquired with the following equipment: a Systems Engineering and Assessment, Ltd., SWATHplus interferometric sonar (468 kilohertz (kHz)), an EdgeTech 424 (4-24 kHz) chirp sub-bottom profiling system, and a Knudsen 320BP (210 kHz) echosounder. This report serves as an archive of processed interferometric swath and single-beam bathymetry data. Geographic information system data products include an interpolated digital elevation model, an acoustic backscatter mosaic, trackline maps, and point data files. Additional files include error analysis maps, Field Activity Collection System logs, and formal Federal Geographic Data Committee metadata. NOTE: These data are scientific in nature and are not to be used for navigation.

Louisiana↗
USGS2014

Coastal bathymetry data collected in 2011 from the Chandeleur Islands, Louisiana

As part of the Barrier Island Evolution Research project, scientists from the U.S. Geological Survey St. Petersburg Coastal and Marine Science Center conducted nearshore geophysical surveys off the northern Chandeleur Islands, Louisiana, in June of 2011. The overall objectives of the study are to better understand barrier-island geomorphic evolution, particularly storm-related depositional and erosional processes that shape the islands over annual to interannual timescales (1-5 years). Collection of geophysical data will allow us to identify relationships between the geologic history of the island and its present day morphology and sediment distribution. This mapping effort was the first in a series of three planned surveys in this area. High resolution geophysical data collected in each of three consecutive years along this rapidly changing barrier-island system will provide a unique time-series dataset that will significantly further the analyses and geomorphological interpretations of this and other coastal systems, improving our understanding of coastal response and evolution over short time scales (1-5 years). This data series includes the bathymetric data that were collected during two cruises ( USGS Field Activity Numbers 11BIM01 and 11BIM02 ) aboard the Research Vessel (R/V) SurveyCat and the R/V TwinVee along the northern portion of the Chandeleur Islands, Breton National Wildlife Refuge , Louisiana. Data were acquired with the following equipment: a Systems Engineering and Assessment, Ltd., SWATH plus interferometric sonar (234 kilohertz), an EdgeTech 424 (4-24 kHz) chirp sub-bottom profiling system, and a Marimatech E-SEA Sound 206 (200 kHz) echosounder. This report serves as an archive of processed interferometric swath and single-beam bathymetry data. Geographic Iinformation System data products include a 50-meter cell-size interpolated bathymetry grid surface, trackline maps, and point data files. Additional files include error analysis maps, Field Activity Collection System logs, and formal Federal Geographic Data Committee metadata.

Louisiana↗
USGS2014

Sediment data collected in 2012 from the northern Chandeleur Islands, Louisiana

As part of the Barrier Island Evolution Research project, scientists from the U.S. Geological Survey St. Petersburg Coastal and Marine Science Center collected sediment samples from the northern Chandeleur Islands in March and September 2012. The overall objective of this project, which integrates geophysical (bathymetric, seismic, and topographic) and sedimentologic data, is to better understand the depositional and erosional processes that drive the morphologic evolution of barrier islands over annual to interannual timescales (1 to 5 years). Between June 2010 and April 2011, in response to the Deepwater Horizon oil spill, the State of Louisiana constructed a sand berm extending more than 14 kilometers along the northern Chandeleur Islands platform. The construction of the berm provided a unique opportunity to investigate how this new sediment source will interact with and affect the morphologic evolution of the barrier-island system. Data collected from this study will be used to describe differences in the physical characteristics and spatial distribution of sediments both along the axis of the berm and also along transects across the berm and onto the adjacent barrier island. Comparison of these data with data from subsequent sampling efforts will provide information about sediment interactions and movement between the berm and the natural island platform, improving our understanding of short-term morphologic change and processes in this barrier-island system. This data series serves as an archive of sediment data collected in March and September 2012 from the Chandeleur Islands sand berm and adjacent barrier-island environments. Data products include descriptive core logs, core photographs and x-radiographs, results of sediment grain-size analyses, sample location maps, and Geographic Information System data files with accompanying formal Federal Geographic Data Committee metadata.

Louisiana↗
USGS2014

Sediment data collected in 2013 from the northern Chandeleur Islands, Louisiana

As part of the Barrier Island Evolution Research project, scientists from the U.S. Geological Survey St. Petersburg Coastal and Marine Science Center collected sediment samples from the northern Chandeleur Islands in July 2013. The overall objective of this project, which integrates geophysical (bathymetric, seismic, and topographic) and sedimentologic data, is to better understand the depositional and erosional processes that drive the morphologic evolution of barrier islands over annual to interannual timescales (1 to 5 years). Between June 2010 and April 2011, in response to the Deepwater Horizon oil spill, the State of Louisiana constructed a sand berm extending more than 14 kilometers along the northern Chandeleur Islands platform. The construction of the berm provided a unique opportunity to investigate how this new sediment source will interact with and affect the morphologic evolution of the barrier-island system. Data collected from this study will be used to describe differences in the physical characteristics and spatial distribution of sediments both along the axis of the berm and also along transects across the berm and onto the adjacent barrier island. Comparison of these data with data from previous sampling efforts will provide information about sediment interactions and movement between the berm and the natural island platform, improving our understanding of short-term morphologic change and processes in this barrier-island system. This data series serves as an archive of sediment data collected in July 2013 from the Chandeleur Islands sand berm and adjacent barrier-island environments. Data products include descriptive core logs, core photographs and x-radiographs, results of sediment grain-size analyses, sample location maps, and Geographic Information System data files with accompanying formal Federal Geographic Data Committee metadata.

Louisiana↗
USGS2001

Dynamic computer model for the metallogenesis and tectonics of the Circum-North Pacific

The digital files on this report consist of a dynamic computer model of the metallogenesis and tectonics of the Circum-North Pacific, and background articles, figures, and maps. The tectonic part of the dynamic computer model is derived from a major analysis of the tectonic evolution of the Circum-North Pacific which is also contained in directory tectevol. The dynamic computer model and associated materials on this CD-ROM are part of a project on the major mineral deposits, metallogenesis, and tectonics of the Russian Far East, Alaska, and the Canadian Cordillera. The project provides critical information on bedrock geology and geophysics, tectonics, major metalliferous mineral resources, metallogenic patterns, and crustal origin and evolution of mineralizing systems for this region. The major scientific goals and benefits of the project are to: (1) provide a comprehensive international data base on the mineral resources of the region that is the first, extensive knowledge available in English; (2) provide major new interpretations of the origin and crustal evolution of mineralizing systems and their host rocks, thereby enabling enhanced, broad-scale tectonic reconstructions and interpretations; and (3) promote trade and scientific and technical exchanges between North America and Eastern Asia.

Open-File Report↗
USGS1987

Rb-Sr isotopic studies of postorogenic granites from the eastern Arabian Shield, Kingdom of Saudi Arabia

Thirteen Rb-Sr whole-rock isochrons for postorogenic granites of the eastern Arabian Shield yield ages that range from 567 to 617 Ma, a similar range to that previously determined ages for leucocratic, evolved granites in that region. The dated plutons range widely in terms of degree of petrologic evolution from primitive (at Najran) to highly evolved (at Jabal al Caharra) and include several plutons that are anomalously enriched in tin and tungsten (Jabal Tarban, Jabal al Gaharra, Jabal Khinzir, and Jabal Minya). Although no uniform relationship was established between age or initial 87 Sr/ 86 Sr and degree of petrologic evolution, the more evolved plutons tend to be younger and to have slightly higher initial 87 Sr/ 86 Sr values. There is a tendency for metalliferous plutons to have elevated initial 87 Sr/ 86 Sr values, but not all plutons with elevated 87 Sr/ 86 Sr values are known to be metalliferous. Several of the dated plutons are situated within the Najd fault zone, and thus, some of the ages are useful in determining times of strike-slip fault activity. The youngest pluton cut by Najd faulting is at Jabal Tukhfah (573±13 Ma). Displacement at this locality is about 2 km, and if normal rates of strike-slip movement are assumed, this displacement suggests that movement for one strand of the Najd faults ceased by about 560 Ma. Available data indicate that postorogenic granites tend to be older in the southern part of the Arabian Shield. This suggests that plutonism started in the south and progressed to the north. Initial 87 Sr/ 86 Sr values also form a regional pattern. These ratios tend to be higher in the eastern part of the Arabian Shield, and suggest one source of continental affinity to the east and one of oceanic affinity to the west. The distribution of initial strontium isotope ratios does not clearly discriminate between the various models for Shield evolution; however, a sedimentary source region of mixed end members seems more compatible with the data pattern than models based on discrete boundaries between unrelated accreted blocks.

Open-File Report↗
USGS1993

A detailed taxonomy of Upper Cretaceous and lower Tertiary Crassatellidae in the eastern United States: An example of the nature of extinction at the boundary

Current theories on the causes of extinction at the Cretaceous-Tertiary boundary have been based on previously published data; however, few workers have stopped to ask the question, 'How good is the basic data set?' To test the accuracy of the published record, a quantitative and qualitative analysis of the Crassatellidae (Mollusca, Bivalvia) of the Gulf and Mid-Atlantic Coastal Plains of the United States for the Upper Cretaceous and lower Tertiary was conducted. Thirty-eight species names and four generic names are used in publications for the Crassatellidae within the geographic and stratigraphic constraints of this analysis. Fourteen of the 38 species names are represented by statistically valid numbers of specimens and were tested by using canonical discriminant analysis. All 38 names, with the exception of 1 invalid name and 4 names for which no representative specimen could be located, were evaluated qualitatively. The results show that the published fossil record is highly inaccurate. Only 8 valid, recognizable species exist in the Crassatellidae within the limits of this study, 14 names are synonymized, and 11 names are represented by indeterminate molds or poorly preserved specimens. Three of the four genera are well founded; the fourth is based on the juvenile of another genus and therefore synonymized. This detailed taxonomic analysis of the Crassatellidae illustrates that the published fossil record is not reliable. Calculations of evolutionary and paleobiologic significance based on poorly defined, overly split fossil groups, such as the Crassatellidae, are biased in the following ways: Rates of evolution and extinction are higher, Faunal turnover at mass extinctions appears more catastrophic, Species diversity is high, Average species durations are shortened, and Geographic ranges are restricted. The data on the taxonomically standardized Crassatellidae show evolutionary rates one-quarter to one-half that of the published fossil record; faunal change at the Cretaceous-Tertiary boundary that was not catastrophic; a constant number of species on each side of the Cretaceous-Tertiary boundary; a decrease in abundance in the Tertiary; and lower species diversity, longer average species durations, and expanded geographic ranges. Similar detailed taxonomic studies need to be conducted on other groups of organisms to test the patterns illustrated for the Crassatellidae and to determine the extent and direction of the bias in the published fossil record. Answers to our questions about evolutionary change cannot be found in the literature but rather with the fossils themselves. Evolution and extinction occur within small populations of species groups, and it is only through detailed analysis of these groups that we can achieve an understanding of the causes and effects of evolution and extinction.

Professional Paper↗