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At least 505 records · Page 28Linked to original sources
USGS1998

Carbon cycling in terrestrial environments: Chapter 17

This chapter reviews a number of applications of isotopic techniques for the investigation of carbon cycling processes. Carbon dioxide (C0 2 ) is an important greenhouse gas. Its concentration in the atmosphere has increased from an estimated 270 ppm at the beginning of the industrial revolution to ∼ 360 ppm at present. Climatic conditions and atmospheric C0 2 concentration also influence isotopic discrimination during photosynthesis. Natural and anthropogenically induced variations in the carbon isotopic abundance can be exploited to investigate carbon transformations between pools on various time scales. It also discusses one of the isotopes of carbon, the 14 C, that is produced in the atmosphere by interactions of cosmic-ray produced neutrons with stable isotopes of nitrogen (N), oxygen (O), and carbon (C), and has a natural abundance in the atmosphere of ∼1 atom 14 C per 10 12 atoms 12 C. The most important factor affecting the measured 14 C ages of soil organic matter is the rate of organic carbon cycling in soils. Differences in the dynamics of soil carbon among different soils or soil horizons will result in different soil organic 14 C signatures. As a result, the deviation of the measured 14 C age from the true age could differ significantly among different soils or soil horizons.

Book chapter↗
USGS2021

Profiling lunar dust dissolution in aqueous environments: The design concept

Published studies and internal NASA reports indicate that when native lunar dust is suspended in an aqueous solution a variety of metal and other ions are released. This release has implications for future lunar missions, ranging from effects on mission hardware, effects on life support systems, possible direct effects on human health, and effects on research experiments such as plant growth experiments, space biology experiments and any activities that may involve the use of water sourced from the lunar poles. Furthermore, such contaminants could become concentrated or chemically altered to a more hazardous form during a variety of lunar mission activities, including everything from space suit cleaning to lunar industrial materials extraction. The exact profile of the release of ions from lunar dust and the nature of the partially dissolved particles has not been explored. Any model of this dissolution must be based on an understanding of the unique micromorphology of lunar dust, including its glassy nature, agglutinate features, high surface area and the presence of small deposits of elemental iron (nanophase iron) located near the surface of the grain particles. Dust has a very high surface area available for interaction with water. For this reason, on first exposure to water, an immediate pulsed release of ions could occur, with more prolonged release taking place over months or years. The few studies that have been conducted previously have been limited in both the time scales examined and in the selection of ions that were measured. The proposed investigation is a comprehensive materials science investigation, using the most modern analytical tools to catalogue all metals given off from lunar dust in various aqueous solutions and their time profiles of release from the very short term to the very long term. The product of the proposed study will be a comprehensive database determined from NASA curated samples collected from the Apollo landing sites that can be applied to research in both living systems and non-living systems on the moon. The methods developed in the proposed study will also establish standards for analysis of lunar dust samples returned from future manned missions (Artemis and others) and future robotic missions. The knowledge gained from this basic materials science investigation will have broad impact on the design of engineered human safety and health systems.

Acta Astronautica↗
USGS2022

Late Holocene human-environment interactions on the central California coast, USA, inferred from Morro Bay salt marsh sediments

Coastal salt marshes and estuaries provide valuable ecosystem services, yet are susceptible to alteration from human activities. Records of past environmental change in these ecosystems can elucidate relationships between human activities, such as land-use practices, and physical and ecological processes, such as sediment accretion and vegetation changes. To reconstruct the environmental history of one such site, we present inferences based on analysis of sediment cores (including magnetic susceptibility, loss-on-ignition, and pollen) from the Morro Bay salt marsh, located in California’s central coast in the USA. Chronologic control for the sediments was established using radiocarbon dates, a spike in lead (Pb) sourced from gasoline combustion exhaust, and the first identified occurrences of the non-native taxa Erodium cf. cicutarium (filaree) and Eucalyptus . We demonstrate that the Morro Bay watershed was significantly altered following Spanish settlement in the region. Environmental changes associated with livestock grazing and agriculture become evident in the data starting after 1772 CE, when the Mission San Luis Obispo de Tolosa was established nearby. The most prominent changes observed are an increase in the accumulation rate of terrigenous sediment, organic matter, and carbonates, as well as a reduction in arboreal taxa concomitant with increased abundances of shrubs, herbs, and grasses. The expansion of Salicornia (pickleweed) in the 19th century suggests the salt marsh expanded at this time due to increased sediment accumulation and a resulting increase in local elevation. The timing and character of changes recorded in the Morro Bay salt marsh sediments are similar to those documented across California in estuaries, marshes, lakes, and meadows, demonstrating the magnitude of the impacts of European settlement and associated land-use practices in this region.

Anthropocene↗
USGS2009

The Drenchwater deposit, Alaska: An example of a natural low pH environment resulting from weathering of an undisturbed shale-hosted Zn-Pb-Ag deposit

The Drenchwater shale-hosted Zn-Pb-Ag deposit and the immediate vicinity, on the northern flank of the Brooks Range in north-central Alaska, is an ideal example of a naturally low pH system. The two drainages, Drenchwater and False Wager Creeks, which bound the deposit, differ in their acidity and metal contents. Moderately acidic waters with elevated concentrations of metals (pH ??? 4.3, Zn ??? 1400 ??g/L) in the Drenchwater Creek drainage basin are attributed to weathering of an exposed base-metal-rich massive sulfide occurrence. Stream sediment and water chemistry data collected from False Wager Creek suggest that an unexposed base-metal sulfide occurrence may account for the lower pH (2.7-3.1) and very metal-rich waters (up to 2600 ??g/L Zn, ??? 260 ??g/L Cu and ???89 ??g/L Tl) collected at least 2 km upstream of known mineralized exposures. These more acidic conditions produce jarosite, schwertmannite and Fe-hydroxides commonly associated with acid-mine drainage. The high metal concentrations in some water samples from both streams naturally exceed Alaska state regulatory limits for freshwater aquatic life, affirming the importance of establishing base-line conditions in the event of human land development. The studies at the Drenchwater deposit demonstrate that poor water quality can be generated through entirely natural weathering of base-metal occurrences, and, possibly unmineralized black shale.

Applied Geochemistry↗
USGS2017

Chemical elements in the environment: multi-element geochemical datasets from continental to national scale surveys on four continents

During the last 10-20 years, Geological Surveys around the world have undertaken a major effort towards delivering fully harmonized and tightly quality-controlled low-density multi-element soil geochemical maps and datasets of vast regions including up to whole continents. Concentrations of between 45 and 60 elements commonly have been determined in a variety of different regolith types (e.g., sediment, soil). The multi-element datasets are published as complete geochemical atlases and made available to the general public. Several other geochemical datasets covering smaller areas but generally at a higher spatial density are also available. These datasets may, however, not be found by superficial internet-based searches because the elements are not mentioned individually either in the title or in the keyword lists of the original references. This publication attempts to increase the visibility and discoverability of these fundamental background datasets covering large areas up to whole continents.

Applied Geochemistry↗
USGS2020

Natural attenuation can lead to environmental resilience in mine environment

Four streams flowing in the Iglesiente and Arburese mine districts (SW Sardinia, Italy), exploited for zinc (Zn) and lead (Pb) extraction from sulphides and secondary non-sulphide mineralization (calamine ores), have been studied combining investigations from the macroscale (hydrologic tracer techniques) to the microscale (X-ray powder diffraction, scanning electron microscopy, X-ray absorption spectroscopy). In the investigated area, concerns arise from release of metals to water during weathering of ore minerals and mine-waste. Specifically, Zn is observed at extremely high concentrations (10s of mg/L or more) in waters in some of the investigated catchments. The results from synoptic sampling campaigns showed marked differences of Zn loads, from 6.3 kg/day (Rio San Giorgio) to 2000 kg/day (Rio Irvi). Moreover, natural attenuation of metals was found to occur i) through precipitation of Fe compounds (Fe oxy/hydroxides and “green rust”), ii) by means of the authigenic formation of metal sulphides promoted by microbial sulphate reduction, iii) by metal intake in roots and stems of plants ( Phragmites australis and Juncus acutus ) and by immobilization in the rhizosphere, and iv) by cyanobacterial biomineralization processes that lead to formation of Zn-rich phases (hydrozincite and amorphous Zn-silicate) The biologically mediated natural processes that lead to significant abatement and/or reduction of metal loads, are the response of environmental systems to perturbations caused from mine activities, and can be considered part of the resilience of the system itself. The aim of this study is to understand the effect of these processes on the evolution of the studied systems towards more stable and, likely, resilient conditions, e.g. by limiting metal mobility and favoring the improvement of the overall quality of water. The understanding of how ecosystems adapt and respond to contamination, and which chemical and physical factors control these natural biogeochemical barriers, can help to plan effective remediation actions.

Sardinia↗
USGS2020

Keeping up with the times: Mapping range-wide habitat suitability for endangered species in a changing environment

Biologists and policy-makers have the difficult task of allocating limited resources to habitat conservation and management for endangered species in the face of changing environmental conditions. Satellite remote sensing can inform conservation because it is an efficient means to obtain environmental data over broad spatial and temporal extents. Yet, the challenges of accessing, processing, and analyzing remote sensing data hinder wider application of these techniques in conservation planning. We used Landsat data and hierarchical statistical models to link satellite-derived habitat measurements with abundance of endangered Yuma Ridgway's rails ( Rallus obsoletus yumanensis ) within the Lower Colorado River Basin and Salton Sink, USA. We addressed many of the challenges facing the application of remote sensing techniques by using the web-based, freely-available Google Earth Engine to process Landsat datasets, apply habitat models, and generate maps to predict habitat suitability at a fine spatial grain (30 m) across the range of the species. These maps are shareable, interactive, and easy to update annually as habitat conditions change using a Google Earth Engine App we developed. Thus, we provide a framework for building habitat suitability models and maps to help target adaptive habitat management over broad extents for sensitive species, enabling biologists to improve conservation and restoration efforts regularly as conditions change in highly variable ecosystems. We demonstrate this approach for Yuma Ridgway's rails, but our methods for merging hierarchical statistical models with open-source mapping software to describe spatial-temporal heterogeneity in habitat quality are applicable to any species, and are especially helpful to species inhabiting highly variable ecosystems.

Arizona, California, Nevada↗
USGS2013

The impact environment of the Hadean Earth

Impact bombardment in the first billion years of solar system history determined in large part the initial physical and chemical states of the inner planets and their potential to host biospheres. The range of physical states and thermal consequences of the impact epoch, however, are not well quantified. Here, we assess these effects on the young Earth's crust as well as the likelihood that a record of such effects could be preserved in the oldest terrestrial minerals and rocks. We place special emphasis on modeling the thermal effects of the late heavy bombardment (LHB) – a putative spike in the number of impacts at about 3.9 Gyr ago – using several different numerical modeling and analytical techniques. A comprehensive array of impact-produced heat sources was evaluated which includes shock heating, impact melt generation, uplift, and ejecta heating. Results indicate that ∼1.5–2.5 vol.% of the upper 20 km of Earth's crust was melted in the LHB, with only ∼0.3–1.5 vol.% in a molten state at any given time. The model predicts that approximately 5–10% of the planet's surface area was covered by >1 km deep impact melt sheets. A global average of ∼600–800 m of ejecta and ∼800–1000 m of condensed rock vapor is predicted to have been deposited in the LHB, with most of the condensed rock vapor produced by the largest (>100-km) projectiles. To explore for a record of such catastrophic events, we created two- and three-dimensional models of post-impact cooling of ejecta and craters, coupled to diffusion models of radiogenic Pb*-loss in zircons. We used this to estimate what the cumulative effects of putative LHB-induced age resetting would be of Hadean zircons on a global scale. Zircons entrained in ejecta are projected to have the following average global distribution after the end of the LHB: ∼59% with no impact-induced Pb*-loss, ∼26% with partial Pb*-loss and ∼15% with complete Pb*-loss or destruction of the grain. In addition to the relatively high erodibility of ejecta, our results show that if discordant ca. 3.9 Gyr old zones in the Jack Hills zircons are a signature of the LHB, they were most likely sourced from impact ejecta.

Chemie der Erde↗
USGS2005

Secondary sulfate minerals associated with acid drainage in the eastern US: Recycling of metals and acidity in surficial environments

Weathering of metal-sulfide minerals produces suites of variably soluble efflorescent sulfate salts at a number of localities in the eastern United States. The salts, which are present on mine wastes, tailings piles, and outcrops, include minerals that incorporate heavy metals in solid solution, primarily the highly soluble members of the melanterite, rozenite, epsomite, halotrichite, and copiapite groups. The minerals were identified by a combination of powder X-ray diffraction (XRD), scanning electron microscopy (SEM), and electron-microprobe. Base-metal salts are rare at these localities, and Cu, Zn, and Co are commonly sequestered as solid solutions within Fe- and Fe-Al sulfate minerals. Salt dissolution affects the surface-water chemistry at abandoned mines that exploited the massive sulfide deposits in the Vermont copper belt, the Mineral district of central Virginia, the Copper Basin (Ducktown) mining district of Tennessee, and where sulfide-bearing metamorphic rocks undisturbed by mining are exposed in Great Smoky Mountains National Park in North Carolina and Tennessee. Dissolution experiments on composite salt samples from three minesites and two outcrops of metamorphic rock showed that, in all cases, the pH of the leachates rapidly declined from 6.9 to <3.7, and specific conductance increased gradually over 24 h. Leachates analyzed after 24-h dissolution experiments indicated that all of the salts provided ready sources of dissolved Al (>30 mg L-1), Fe (>47 mg L-1), sulfate (>1000 mg L-1), and base metals (>1000 mg L-1 for minesites, and 2 mg L-1 for other sites). Geochemical modeling of surface waters, mine-waste leachates, and salt leachates using PHREEQC software predicted saturation in the observed ochre minerals, but significant concentration by evaporation would be needed to reach saturation in most of the sulfate salts. Periodic surface-water monitoring at Vermont minesites indicated peak annual metal loads during spring runoff. At the Virginia site, where no winter-long snowpack develops, metal loads were highest during summer months when salts were dissolved periodically by rainstorms following sustained evaporation during dry spells. Despite the relatively humid climate of the eastern United States, where precipitation typically exceeds evaporation, salts form intermittently in open areas, persist in protected areas when temperature and relative humidity are appropriate, and contribute to metal loadings and acidity in surface waters upon dissolution, thereby causing short-term perturbations in water quality.

Chemical Geology↗
USGS2012

Predictions and retrodictions of the hierarchical representation of habitat in heterogeneous environments

Interaction between habitat and species is central in ecology. Habitat structure may be conceived as being hierarchical, where larger, more diverse, portions or categories contain smaller, more homogeneous portions. When this conceptualization is combined with the observation that species have different abilities to relate to portions of the habitat that differ in their characteristics, a number of known patterns can be derived and new patterns hypothesized. We propose a quantitative form of this habitat&ndash;species relationship by considering species abundance to be a function of habitat specialization, habitat fragmentation, amount of habitat, and adult body mass. The model reproduces and explains patterns such as variation in rank&ndash;abundance curves, greater variation and extinction probabilities of habitat specialists, discontinuities in traits (abundance, ecological range, pattern of variation, body size) among species sharing a community or area, and triangular distribution of body sizes, among others. The model has affinities to Holling's textural discontinuity hypothesis and metacommunity theory but differs from both by offering a more general perspective. In support of the model, we illustrate its general potential to capture and explain several empirical observations that historically have been treated independently.

Ecological Modelling↗
USGS2014

Population age and initial density in a patchy environment affect the occurrence of abrupt transitions in a birth-and-death model of Taylor's law

Taylor's power law describes an empirical relationship between the mean and variance of population densities in field data, in which the variance varies as a power, b , of the mean. Most studies report values of b varying between 1 and 2. However, Cohen (2014a) showed recently that smooth changes in environmental conditions in a model can lead to an abrupt, infinite change in b . To understand what factors can influence the occurrence of an abrupt change in b , we used both mathematical analysis and Monte Carlo samples from a model in which populations of the same species settled on patches, and each population followed independently a stochastic linear birth-and-death process. We investigated how the power relationship responds to a smooth change of population growth rate, under different sampling strategies, initial population density, and population age. We showed analytically that, if the initial populations differ only in density, and samples are taken from all patches after the same time period following a major invasion event, Taylor's law holds with exponent b =1, regardless of the population growth rate. If samples are taken at different times from patches that have the same initial population densities, we calculate an abrupt shift of b , as predicted by Cohen (2014a). The loss of linearity between log variance and log mean is a leading indicator of the abrupt shift. If both initial population densities and population ages vary among patches, estimates of b lie between 1 and 2, as in most empirical studies. But the value of b declines to ~1 as the system approaches a critical point. Our results can inform empirical studies that might be designed to demonstrate an abrupt shift in Taylor's law.

Ecological Modelling↗
USGS2005

Landscape development in an hyperarid sandstone environment along the margins of the Dead Sea fault: Implications from dated rock falls

In this study, we explored the spatial and temporal relations between boulders and their original in-situ locations on sandstone bedrock cliffs. This was accomplished by combining field observations with dating methods using cosmogenic isotopes ( 10 Be and 14 C) and optically stimulated luminescence (OSL). Our conclusions bear both on the landscape evolution and cliff retreat process in the hyperarid region of Timna and on the methodology of estimating exposure ages using cosmogenic isotopes. We recognize three discrete rock fall events, at 31 ka, 15 ka, and 4 ka. In this hyperarid region, the most plausible triggering mechanism for rock fall events is strong ground acceleration caused by earthquakes generated by the nearby Dead Sea fault (DSF). Our record, however, under represents the regional earthquake record implying that ongoing development of detachment cracks prior to the triggering event might be slower than the earthquake cycle. Cliff retreat rates calculated using the timing of rock fall events and estimated thickness of rock removed in each event range between 0.14 m ky − 1 and 2 m ky − 1 . When only full cycles are considered, we derive a more realistic range of 0.4 m ky − 1 to 0.7 m ky − 1 . These rates are an order of magnitude faster than the calculated rate of surface lowering in the area. We conclude that sandstone cliffs at Timna retreat through episodic rock fall events that preserve the sharp, imposing, landscape characteristic to this region and that ongoing weathering of the cliff faces is minor. A 10%–20% difference in the 10 Be concentrations in samples from matching boulder and cliff faces that have identical exposure histories and are located only a few meters apart indicates that cosmogenic nuclide production rates are sensitive to shielding and vary spatially over short distances. However, uncertainties associated with age calculations yielded boulder and matching cliff face ages that are similar within 1 σ . The use of external constraints in the form of field relations and OSL dating helped to establish each pair's age. The agreement between calculated 14 C and 10 Be ages indicates that the accumulation of 10 Be at depth by the capture of slow deep-penetrating muons was properly accounted for in the study.

Arava Valley, Dead Sea fault, Timna↗
USGS2016

Deposition, accumulation, and alteration of Cl−, NO3−, ClO4− and ClO3− salts in a hyper-arid polar environment: Mass balance and isotopic constraints

The salt fraction in permafrost soils/sediments of the McMurdo Dry Valleys (MDV) of Antarctica can be used as a proxy for cold desert geochemical processes and paleoclimate reconstruction. Previous analyses of the salt fraction in MDV permafrost soils have largely been conducted in coastal regions where permafrost soils are variably affected by aqueous processes and mixed inputs from marine and stratospheric sources. We expand upon this work by evaluating permafrost soil/sediments in University Valley, located in the ultraxerous zone where both liquid water transport and marine influences are minimal. We determined the abundances of Cl − , NO 3 − , ClO 4 − and ClO 3 − in dry and ice-cemented soil/sediments, snow and glacier ice, and also characterized Cl − and NO 3 − isotopically. The data are not consistent with salt deposition in a sublimation till, nor with nuclear weapon testing fall-out, and instead point to a dominantly stratospheric source and to varying degrees of post depositional transformation depending on the substrate, from minimal alteration in bare soils to significant alteration (photodegradation and/or volatilization) in snow and glacier ice. Ionic abundances in the dry permafrost layer indicate limited vertical transport under the current climate conditions, likely due to percolation of snowmelt. Subtle changes in ClO 4 − /NO 3 − ratios and NO 3 − isotopic composition with depth and location may reflect both transport related fractionation and depositional history. Low molar ratios of ClO 3 − /ClO 4 − in surface soils compared to deposition and other arid systems suggest significant post depositional loss of ClO 3 − , possibly due to reduction by iron minerals, which may have important implications for oxy-chlorine species on Mars. Salt accumulation varies with distance along the valley and apparent accumulation times based on multiple methods range from ∼10 to 30 kyr near the glacier to 70–200 kyr near the valley mouth. The relatively young age of the salts and relatively low and homogeneous anion concentrations in the ice-cemented sediments point to either a mechanism of recent salt removal, or to relatively modern permafrost soils (<1 million years). Together, our results show that near surface salts in University Valley serve as an end-member of stratospheric sources not subject to biological processes or extensive remobilization.

Geochimica et Cosmochimica Acta↗
USGS2021

Long-term variation in polar bear body condition and maternal investment relative to a changing environment

In the Arctic, warming air and ocean temperatures have resulted in substantial changes to sea ice, which is primary habitat for polar bears ( Ursus maritimus ). Reductions in extent, duration, and thickness have altered sea ice dynamics, which influences the ability of polar bears to reliably access marine mammal prey. Because nutritional condition is closely linked to population vital rates, a progressive decline in access to prey or an increase in the energetic cost of accessing prey has the potential to adversely affect polar bear population dynamics. We examined long-term (1983–2015) patterns of spring body condition (indexed using residual body mass) and maternal investment (i.e., litter mass of cubs-of-the-year and yearlings; COY and YRL) of polar bears from Alaska’s southern Beaufort Sea to evaluate potential relationships with regional- and circumpolar-scale sea ice conditions and atmospheric patterns. The length of the summer open-water (OW) season (i.e., the period of time the sea ice is mostly absent from the continental shelf) increased at a rate of 18 days decade -1 over the study period. However, the OW season duration was not a strong determinant of spring residual body mass or litter mass. Residual body mass of independent (i.e., subadults and adults) female bears varied relative to age class, reproductive status, and the strength of the prior winter’s Arctic Oscillation (i.e., a circumpolar-scale mode of climate variability driven by long-term atmospheric patterns). Spring residual mass of independent males varied with age class and variation in wind speed (i.e., regional-scale short-term atmospheric patterns) during the winter of the year preceding capture. Over the study period, mean annual body mass of adult females unaccompanied by COY declined by 4 kg/ decade -1 , while no temporal trends were evident in the mean annual body mass of adult females with COY, adult males, and subadults. Litter mass of COY varied relative to capture date, maternal age class and mass, litter size, and year of capture. Litter mass of YRL varied with capture date, maternal age class and mass, litter size, variation in winter wind speed (the year of and year preceding capture), and the strength of the prior winter’s Arctic Oscillation. Mean annual litter mass of COY decreased at a rate of 2.6 kg decade -1 and declined 0.68 kg for every 10 kg reduction in maternal mass. No trend was evident in the mean annual litter mass of yearlings. These findings suggest a nuanced response of the southern Beaufort Sea polar bears to environmental change, where some demographic groups (e.g., adult males and subadults) are presently more resilient than others to changes in the Arctic marine ecosystem.

Alaska↗
USGS2010

Depositional environments and cyclo- and chronostratigraphy of uppermost Carboniferous-Lower Triassic -lacustrine deposits, southern Bogda Mountains, NW China - A terrestrfluvialial paleoclimatic record of mid-latitude NE Pangea

Two uppermost Carboniferous–Lower Triassic fluvial–lacustrine sections in the Tarlong–Taodonggou half-graben, southern Bogda Mountains, NW China, comprise a 1834 m-thick, relatively complete sedimentary and paleoclimatic record of the east coast of mid-latitude NE Pangea. Depositional environmental interpretations identified three orders (high, intermediate, and low) of sedimentary cycles. High-order cycles (HCs) have five basic types, including fluvial cycles recording repetitive changes of erosion and deposition and lacustrine cycles recording repetitive environmental changes associated with lake expansion and contraction. HCs are grouped into intermediate-order cycles (ICs) on the basis of systematic changes of thickness, type, and component lithofacies of HCs. Nine low-order cycles (LCs) are demarcated by graben-wide surfaces across which significant long-term environmental changes occurred. A preliminary cyclostratigraphic framework provides a foundation for future studies of terrestrial climate, tectonics, and paleontology in mid-latitude NE Pangea. Climate variabilities at the intra-HC, HC, IC, and LC scales were interpreted from sedimentary and paleosol evidence. Four prominent climatic shifts are present: 1) from the humid–subhumid to highly-variable subhumid–semiarid conditions at the beginning of Sakamarian; 2) from highly-variable subhumid–semiarid to humid–subhumid conditions across the Artinskian-Capitanian unconformity; 3) from humid–subhumid to highly-variable subhumid–semiarid conditions at early Induan; and 4) from the highly-variable subhumid–semiarid to humid–subhumid conditions across the Olenekian-Anisian unconformity. The stable humid–subhumid condition from Lopingian to early Induan implies that paleoclimate change may not have been the cause of the end-Permian terrestrial mass extinction. A close documentation of the pace and timing of the extinction and exploration of other causes are needed. In addition, the semiarid–subhumid conditions from Sakamarian to Artinskian–Kungurian (?) and from middle Induan to end of Olenekian are in conflict with modern mid-latitude east coast meso- and macrothermal humid climate. Extreme continentality, regional orographic effect, and/or abnormal circulation of Paleo-Tethys maybe are possible causes. Our work serves as a rare data point at mid-latitude NE Pangea for climate modeling to seek explanations on the origin(s) of climate variability in NE Pangea from latest Carboniferous to Early Triassic.

Global and Planetary Change↗
USGS2016

Comparing orbiter and rover image-based mapping of an ancient sedimentary environment, Aeolis Palus, Gale crater, Mars

This study provides the first systematic comparison of orbital facies maps with detailed ground-based geology observations from the Mars Science Laboratory (MSL) Curiosity rover to examine the validity of geologic interpretations derived from orbital image data. Orbital facies maps were constructed for the Darwin, Cooperstown, and Kimberley waypoints visited by the Curiosity rover using High Resolution Imaging Science Experiment (HiRISE) images. These maps, which represent the most detailed orbital analysis of these areas to date, were compared with rover image-based geologic maps and stratigraphic columns derived from Curiosity’s Mast Camera (Mastcam) and Mars Hand Lens Imager (MAHLI). Results show that bedrock outcrops can generally be distinguished from unconsolidated surficial deposits in high-resolution orbital images and that orbital facies mapping can be used to recognize geologic contacts between well-exposed bedrock units. However, process-based interpretations derived from orbital image mapping are difficult to infer without known regional context or observable paleogeomorphic indicators, and layer-cake models of stratigraphy derived from orbital maps oversimplify depositional relationships as revealed from a rover perspective. This study also shows that fine-scale orbital image-based mapping of current and future Mars landing sites is essential for optimizing the efficiency and science return of rover surface operations.

Icarus↗