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NASA NTRS2005

The Rio Tinto Basin, Spain: Mineralogy, Sedimentary Geobiology, and Implications for Interpretation of Outcrop Rocks at Meridiani Planum, Mars

Exploration by the NASA rover Opportunity has revealed sulfate- and hematite-rich sedimentary rocks exposed in craters and other surface features of Meridiani Planum, Mars. Modern, Holocene, and Plio-Pleistocene deposits of the Rio Tinto, southwestern Spain, provide at least a partial environmental analog to Meridiani Planum rocks, facilitating our understanding of Meridiani mineral precipitation and diagenesis, while informing considerations of martian astrobiology. Oxidation, thought to be biologically mediated, of pyritic ore bodies by groundwaters in the source area of the Rio Tinto generates headwaters enriched in sulfuric acid and ferric iron. Seasonal evaporation of river water drives precipitation of hydronium jarosite and schwertmannite, while (Mg,Al,Fe(sup 3+))-copiapite, coquimbite, gypsum, and other sulfate minerals precipitate nearby as efflorescences where locally variable source waters are brought to the surface by capillary action. During the wet season, hydrolysis of sulfate salts results in the precipitation of nanophase goethite. Holocene and Plio-Pleistocene terraces show increasing goethite crystallinity and then replacement of goethite with hematite through time. Hematite in Meridiani spherules also formed during diagenesis, although whether these replaced precursor goethite or precipitated directly from groundwaters is not known. The retention of jarosite and other soluble sulfate salts suggests that water limited the diagenesis of Meridiani rocks. Diverse prokaryotic and eukaryotic microorganisms inhabit acidic and seasonally dry Rio Tinto environments. Organic matter does not persist in Rio Tinto sediments, but biosignatures imparted to sedimentary rocks as macroscopic textures of coated microbial streamers, surface blisters formed by biogenic gas, and microfossils preserved as casts and molds in iron oxides help to shape strategies for astrobiological investigation of Meridiani outcrops.

Fernandez-Remolar, David C.↗

NASA NTRS2020

The Age of Surface-Exposed Ice Along the Northern Margin of the Greenland Ice Sheet

Each summer, surface melting of the margin of the Greenland Ice Sheet exposes a distinctive visible stratigraphy that is related to past variability in subaerial dust deposition across the accumulation zone and subsequent ice flow toward the margin. Here we map this surface stratigraphy along the northern margin of the ice sheet using mosaicked Sentinel-2 multispectral satellite imagery from the end of the 2019 melt season and finer-resolution WorldView-2/3 imagery for smaller regions of interest. We trace three distinct transitions in apparent dust concentration and the top of a darker basal layer. The three dust transitions have been identified previously as representing late-Pleistocene climatic transitions, allowing us to develop a coarse margin chronostratigraphy for northern Greenland. Substantial folding of late-Pleistocene stratigraphy is observed but uncommon. The oldest conformal surface-exposed ice in northern Greenland is likely located adjacent to Warming Land and maybe up to ~55 thousand years old. Basal ice is commonly exposed hundreds of meters from the ice margin and may indicate a widespread frozen basal thermal state. We conclude that the ice margin across northern Greenland offers multiple opportunities to recover paleoclimatically distinct ice relative to previously studied regions in southwestern Greenland.

Joseph A Macgregor↗

NASA NTRS2021

Landsat Derived Bathymetry of Lakes on the Arctic Coastal Plan of Northern Alaska

The Pleistocene sand sea on the Arctic Coastal Plain (ACP) of northern Alaska is underlain by anancient sand dune field, a geological feature that affects regional lake characteristics. Many of these lakes, whichcover approximately 20 % of the Pleistocene sand sea, are relatively deep (up to 25 m). In addition to the nat-ural importance of ACP sand sea lakes for water storage, energy balance, and ecological habitat, the need forwinter water for industrial development and exploration activities makes lakes in this region a valuable resource.However, ACP sand sea lakes have received little prior study. Here, we collect in situ bathymetric data to test12 model variants for predicting sand sea lake depth based on analysis of Landsat-8 Operational Land Imager(OLI) images. Lake depth gradients were measured at 17 lakes in midsummer 2017 using a Humminbird 798ciHD SI Combo automatic sonar system. The field-measured data points were compared to red–green–blue (RGB)bands of a Landsat-8 OLI image acquired on 8 August 2016 to select and calibrate the most accurate spectral-depth model for each study lake and map bathymetry. Exponential functions using a simple band ratio (withbands selected based on lake turbidity and bed substrate) yielded the most successful model variants. For eachlake, the most accurate model explained 81.8 % of the variation in depth, on average. Modeled lake bathymetrieswere integrated with remotely sensed lake surface area to quantify lake water storage volumes, which rangedfrom 1.056×10−3to 57.416×10−3km3. Due to variations in depth maxima, substrate, and turbidity betweenlakes, a regional model is currently infeasible, rendering necessary the acquisition of additional in situ datawith which to develop a regional model solution. Estimating lake water volumes using remote sensing will fa-cilitate better management of expanding development activities and serve as a baseline by which to evaluatefuture responses to ongoing and rapid climate change in the Arctic. All sonar depth data and modeled lakebathymetry rasters can be freely accessed at https://doi.org/10.18739/A2SN01440 (Simpson and Arp, 2018) andhttps://doi.org/10.18739/A2HT2GC6G (Simpson, 2019), respectively.

Claire E Simpson↗

NASA NTRS2022

A Late Paleocene Age for Greenland’s Hiawatha Impact Structure

The ~31-km-wide Hiawatha structure, located beneath Hiawatha Glacier in northwestern Greenland, has been proposed as an impact structure that may have formed after the Pleistocene inception of the Greenland Ice Sheet. To date the structure, we conducted Ar-40/Ar-39 analyses on glaciofluvial sand and U–Pb analyses on zircon separated from glaciofluvial pebbles of impact melt rock, all sampled immediately downstream of Hiawatha Glacier. Unshocked zircon in the impact melt rocks dates to ~1915 Ma, consistent with felsic intrusions found in local bedrock. The Ar-40/Ar-39 data indicate Late Paleocene resetting and shocked zircon dates to 57.99 ± 0.54 Ma, which we interpret as the impact age. Consequently, the Hiawatha impact structure significantly predates Pleistocene glaciation and is unrelated to either the Paleocene-Eocene Thermal Maximum or flood basalt volcanism in east Greenland. However, it was contemporaneous with the Paleocene Carbon Isotope Maximum, although the impact’s exact paleoenvironmental and climatic significance await further investigation.

Gavin G Kenny↗

NASA NTRS1994

Lessons from Popocatepetl Volcano (Mexico): Ancient Settlement Buried by Lavas, Mudflows, and Air-Fall Deposits

Popocatepetl volcano is 5452 m in altitude and capped by glaciers with a long Late Pleistocene-Holocene history. Volcanic activity has been intense during the last 10 000 years. Therefore, the valleys at the NE foothills of the volcano, covered by air-fall ejecta and drained by the runoff of the glaciers, became very attractive to ancient inhabitants of the Xalizintla Valley (XV) west of Puebla City, because of fertility of soils. The XV was occupied by humans about 2000 years ago who witnessed five events related to volcanic activity related to Popo. These events, described in this paper, are being taken into account for volcanic risk evaluation since several towns with a population of more than 23 000 people reoccupied again the Xalizintla Valley.

volcano Popocatepetl Mexico glacier mud flows huma↗

NASA NTRS2020

Measuring Multiple Cosmogenic Nuclides in Glacial Cobbles Sheds Light on Greenland Ice Sheet Processes

The extent and erosivity of the Greenland Ice Sheet during the Pleistocene remain uncertain due to the paucity of evidence predating the Last Glacial Maximum. Here, we employ a novel approach, cosmogenic nuclide analysis of individual subglacial cobbles, which allows us to infer the behavior of the ice sheet over time and space. From three locations in western Greenland, we collected 86 cobbles from the current ice sheet margin and nine cobbles exposed on the modern proglacial land surface. We measured the concentration of in situ 10Be in all cobbles (n= 95) and 26Al and 14C in a subset (n= 14). Cobbles deposited during Holocene retreat have 10Be exposure ages generally consistent with the timing of ice retreat determined by other means. Conversely, most of the 86 subglacial cobbles contain very low concentrations of 10Be (median 1.0 x 10^3 atoms g-1), although several have ~10^4 and one has ~10^5 atoms g-1. The low concentrations of 10Be in most subglacial cobbles imply that their source areas under the Greenland Ice Sheet are deeply eroded, preserving minimal evidence of surface or near-surface exposure. The presence of measurable 14C in ten of the cobbles requires that they experienced cosmogenic nuclide production within the past ~30 ka; however, 14C/10Be ratios of ~6 suggest that production occurred beneath thin overlying rock, sediment, and/or ice, where the muon component of 14C production dominates. Only two of the 86 subglacial cobbles definitively have cosmogenic nuclide concentrations consistent with prior surface exposure during times of reduced ice extent. Overall, isotopic analysis of subglacial cobbles indicates that western Greenland's subglacial landscape is characterized by deep erosion and minimal subaerial exposure.

Pliocene↗

NASA NTRS2020

Measuring multiple cosmogenic nuclides in glacial cobbles sheds light on Greenland Ice Sheet processes

The behavior of the Greenland Ice Sheet during the Pleistocene remains uncertain due to the paucity of evidence predating the Last Glacial Maximum. Here, we employ a novel approach, cosmogenic nuclide analysis of individual subglacially-derived cobbles, which allows us to make inferences about ice sheet processes and subglacial erosion. From three locations in western Greenland, we collected 86 cobbles from the current ice sheet margin and nine cobbles exposed on the modern proglacial land surface. We measured the concentration of in situ 10Be in all cobbles (n =95) and 26Al and 14C in a subset (n =14). Cobbles deposited during Holocene retreat have 10Be exposure ages generally consistent with the timing of ice retreat determined by other methods. Conversely, most of the 86 subglacial cobbles contain very low concentrations of 10Be (median 1.0×10^3atoms/g), although several have ∼104and one has ∼10^5atoms/g. The low concentrations of 10Be in most subglacial cobbles imply that their source areas under the Greenland Ice Sheet are deeply eroded, preserving minimal evidence of surface or near-surface exposure. The presence of measurable 14C in ten of the cobbles requires that they experienced cosmogenic nuclide production within the past ∼30 ka; however, 14C/10Be ratios of ∼6 suggest that nuclide production occurred during shielding by overlying material. Only two of the 86 subglacial cobbles definitively have cosmogenic nuclide concentrations consistent with prior surface exposure. Overall, isotopic analysis of subglacial cobbles indicates that much of western Greenland’s subglacial landscape is characterized by deep erosion and minimal subaerial exposure.

cosmogenic nuclides↗

NASA NTRS1971

Physical features of Icelandic lava flows

Analyzing subaerial flows of lava in eastern Iceland and recent and Pleistocene flows in neovolcanic zone of central Iceland for basalt composition

Lefebryre, R. H.↗

NASA NTRS1972

Space configuration as an explanation for lithology-related cross-polarized radar image anomalies

Three rock types are described that produce dark cross-polarized images on Ka-band imagery: lava flows dating from Pleistocene and Holocene, some Tertiary volcanics, and certain massive sandstones. Their planar surfaces are large with respect to the wavelength of the Ka-band system, yet are small in comparison to the resolution. It is found that only outcrops with proper faceted surface orientations produce significant radar returns showing the dominance of specular reflectors. The omnidirectional attitude of the facets and their wide distribution on the outcrops explains the independence of look-direction that the flat-lying anomalous outcrops exhibit in production of darker cross-polarized images.

Mccauley, J. R.↗

NASA NTRS1972

Highly differentiated subalkaline rhyolite from Glass Mountain, Mono County, California.

Available data on the partition of Sr between coexisting feldspar and melt phases re interpreted as an indication that a rhyolite from Glass Mountain represents about 25% of a hypothetical 'parent' magma of silicic composition having a norm ntent of 150 ppm. Available Sr and Pb isotope data on nearby Pleistocene rhyolite lavas suggest that the 'parent' magmas of volcanic rocks of the area came from mafic or ultramafic source marl.

Noble, D. C.↗

NASA NTRS1973

Evaluation of ERTS-1 imagery for mapping Quaternary deposits and landforms in the Great Plains and Midwest

The author has identified the following significant results. The main landform associations and larger landforms are readily identifiable on the better images and commonly the gross associations of surficial Quaternary deposits also can be differentiated, primarily by information on landforms and soils. Maps showing the Quaternary geologic-terrain units that can be differentiated from the ERTS-1 images are being prepared for 20-odd potential study areas in Illinois, Iowa, Missouri, Kansas, Nebraska, and South Dakota. Among the more distinct features are the major moraines and outwash channels of the last (Wisconsin) glaciation. Analysis of dissection/drainage patterns from the synoptic imagery is proving useful for detecting anomalies that may be caused by stream diversions and moraines of pre-Wisconsin glaciations, by variable loess deposition, by tectonism, and other factors. Numerous abandoned river valleys have been mapped. Trend-lines of several known pre-Wisconsin moraine systems have been identified in Iowa, Nebraska, and Kansas, and also several similar trend-lines, that may indicate previously unknown moraine systems of middle and possibly early Pleistocene age, have been found in Iowa and Missouri. The area inundated by a major flood in southwestern Iowa also has been delineated from ERTS-1 imagery.

Morrison, R. B.↗

NASA NTRS1973

Analysis of ERTS-1 imagery of Wyoming and its application to evaluation of Wyoming's natural resources

The author has identified the following significant results. The Wyoming investigation has progressed according to schedule during the Jan. - Feb., 1973 report period. A map of the maximum extent of Pleistocene glaciation was compiled for northwest Wyoming from interpretations of glacial features seen on ERTS-1 imagery. Using isodensitometry as a tool for image enhancement, techniques were developed which allowed accurate delineation of small urban areas and provided distinction of broad classifications within these small urban centers.

Marrs, R. W.↗

NASA NTRS1973

Mapping of the major structures of the African rift system

The author has identified the following significant results. ERTS-1 imagery of the African rift system has already proved of great value in structural geological studies. One of the interesting megastructures expressed on the imagery occurs some 40 km east of the eastern margin of the main Ethiopian rift, in Arussi province, and extending between latitude 71/2 and 81/4 deg N. The Badda-Encuolo ridge proves to have been a line of major Tertiary volcanism and probably supplied the thick Trap Series flood basalt sequence exposed farther east in the canyons of the Webi Shebeli drainage system. The ridge itself was built up by the waning activity of the Sagatu line of volcanism. Serendipitious has been the discovery on Mt. Badda of several deeply glaciated valleys, many of which show clearly on the ERTS-1 imagery. It seems that Mt. Badda was one of the most important glacial centers in eastern Africa during the Pleistocene. Three major late-Tertiary trachytic centers lie between the Badda-Encuolo ridge and the rift valley. The relationships of these three volcanoes to each other and to the rift faulting is revealed for the first time by the ERTS-1 imagery, as is the form of the cladera of Baltata and the crater of Chilalo.

Mohr, P. A.↗

NASA NTRS1973

Structural and lithologic study of northern coast ranges and Sacramento Valley, California

The author has identified the following significant results. The pattern of linear systems within the project area has been extended into the western foothill belt of the Sierra Nevada. The chief pattern of linear features in the western Sierran foothill belt trends about N. 10 - 15 deg W., but in the vicinity of the Feather River the trend of the features abruptly changes to about N. 50-60 deg W and appears to be contiguous across the Sacramento Valley with a similar system of linear features in the Coast Ranges. The linear features in the Modoc Plateau and Klamath Mt. areas appear unrelated to the systems detected in the Coast Ranges of Sierran foothill belt. Although the change in trend of the Sierran structural features has been previously suggested and the interrelationship of the Klamath Mt. region with the northern Sierra Nevadas has been postulated, the data obtained from the ERTS-1 imagery strengthens these notions and provides for the first time evidence of a direct connection of the structural trends within the alluviated part of the Sacramento Valley. In addition rocks of Pleistocene and Holocene age are offset by some of the linear features seen on ERTS-1 imagery and hence may record the latest episode of geologic deformation in north-central California.

Rich, E. I.↗

NASA NTRS1972

Calcified proteins in the sedimentary environment.

Amino acid diagenesis is considered in relatively young fossil mollusk shells which are capable of preserving some of their original organic constituents. The rate of change of amino acid content in fossils is related to time and diagenetic temperature. Thus, the amino acid content provides information relating to the approximate ages of shells. Pleistocene temperatures and sea level changes in Florida are discussed, along with stratification correlation.

Mitterer, R. M.↗

NASA NTRS1974

Structural lineaments in the southern Sierra Nevada, California

The author has identified the following significant results. Several lineaments observed in ERTS-1 MSS imagery over the southern Sierra Nevada of California have been studied in the field in an attempt to explain their geologic origins and significance. The lineaments are expressed topographically as alignments of linear valleys, elongate ridges, breaks in slope or combinations of these. Natural outcrop exposures along them are characteristically poor. Two lineaments were found to align with foliated metamorphic roof pendants and screens within granitic country rocks. Along other lineaments, the most consistant correlations were found to be alignments of diabase dikes of Cretaceous age, and younger cataclastic shear zones and minor faults. The location of several Pliocene and Pleistocene volcanic centers at or near lineament intersections suggests that the lineaments may represent zones of crustal weakness which have provided conduits for rising magma.

Liggett, M. A.↗

NASA NTRS1973

Evaluation of ERTS-1 imagery for mapping Quaternary deposits and landforms in the Great Plains and Midwest

The author has identified the following significant results. Maps at 1:1 million scale exemplifying the first phase of the investigation (which consists of the identification and mapping of landform and land use characteristics and surficial geologic materials directly from the ERTS-1 images without use of additional data) were prepared. For areas that have not been mapped at 1:500,000 or larger scales, maps will provide the first moderately detailed information on landform features and surficial materials. Much of the information mapped is significant for exploration and development of ground (and, locally, petroleum) and for applications in engineering and environmental geology, including land use planning. Analysis of drainage patterns, stream-divide relations and land use patterns has revealed several possible moraine-controlled divices of middle and early Pleistocene age. One is an extension of the Cedar Bluffs moraine of southeastern Nebraska. Another of these divides may correspond to the terminus of Nebraska drift in the Kansas City study area. The trends of parts of various ancient filled valleys also have been identified by analysis of charges in width of the present stream valleys. The alinements of certain segments of stream valleys in Kansas and Missouri appear to be controlled by regional faults or other structural features.

Morrison, R. B.↗

NASA NTRS1974

Summary of an integrated ERTS-1 project and its results at the Missouri Geological Survey

Use of the ERTS imagery involved the recognition and interpretation of various ground patterns. Analysis and application are tied to ongoing programs. Specific studies utilizing the imagery and NASA aircraft photography are: a statewide lake and dam inventory; assessment of flooding and floodprone areas along the Missouri portion of the Mississippi and Missouri Rivers; land-use classification for several counties; structural features in selected areas; and Pleistocene features in northern Missouri. Though it has been suggested that repetitive coverage is not necessary for geologic studies, it is this specific feature along with the synoptic view of large portions of the State that provided the potential for the utilization of the ERTS imagery in Missouri. Other State agencies, Departments of Conservation, Agriculture, and Community Affairs, have expressed interest in the potential application of ERTS data in their respective fields.

Martin, J. A.↗