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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
NASA NTRS1991

Geochemical stratigraphy of two regolith cores from the Central Highlands of the moon

High-resolution concentration profiles are presented for 20-22 chemical elements in the under 1-mm grain-size fractions of 60001-7 and 60009/10. Emphasis is placed on the stratigraphic features of the cores, and the fresh results are compared with those of previous petrographic and geochemical studies. For elements associated with major mineral phases, the variations in concentration in both cores exceed that observed in some 40 samples of surface and trench soils. Most of the variation in lithophile element concentrations at depths of 18 to 21 cm results from the mixing of two components - oil that is relatively mafic and rich in incompatible trace elements (ITEs), and coarse-grained anorthosite. The linearity of mixing lines on two-element concentration plots argues that the relative abundances of these various subcomponents are sufficiently uniform from sample to sample and from region to region in the core that the mixture behaves effectively as a single component. Soils at depths of 52-55 cm exhibit very low concentrations of ITEs.

Korotev, R. L.↗
NASA NTRS1991

Stratigraphy of the layered terrain in Valles Marineris, Mars

The layered terrain in Valles Marineris provides information about its origin and the geologic history of this canyon system. Whether the terrain is sedimentary material deposited in a dry or lacustrine environment, or volcanic material related to the tectonics of the canyon is still controversial. However, recent studies of Gangis Layered Terrain suggests a cyclic sequence of deposition and erosion under episodic lacustrine conditions. The stratigraphic studies are extended to four other occurrences of layered terrains in Valles Marineris in an attempt to correlate and distinguish between depositional environments. The Juvantae Chasma, Hebes Chasma, Ophir and Candor Chasmata, Melas Chasma, and Gangis Layered Terrain were examined. Although there are broad similarities among the layered terrains, no two deposits are exactly alike. This suggests that there was no synchronized regional depositional processes to form all the layered deposits. However, the similar erosional style of the lower massive weakly bedded unit in Hebes, Gangis, and Ophir-Candor suggests it may have been deposited under similar circumstances.

Komatsu, G.↗
NASA NTRS1991

Stratigraphy of the Perrine and Nun Sulci quadrangles (Jg-2 and Jg-5), Ganymede

Dark and light terrain materials in the Perrine and Nun Sulci quadrangles are divided into nine map units, four dark, and five light. These are placed in time-stratigraphic sequence primarily by means of embayment and cross-cutting relationships. Dark terrain is generally more heavily cratered and thus older that light terrain but, at least in these quadrangles, crater densities are not reliable indicators of relative ages among the four dark material units. The four mapped material units within dark terrain are: cratered dark materials (dc), grooved dark materials (dg), transitional dark materials (di), and dark materials, undivided (d). The five mapped units within light terrain are: intermediate light materials (li), grooved light materials (lg), irregularly grooved light materials (lgl), smooth light materials (ls), and light materials, undivided.

Mcgill, George E.↗
NASA NTRS1992

Latest Proterozoic stratigraphy and earth history

Novel biostratigraphic and chemostratigraphic data furnish an improved framework for stratigraphic correlation of the Proterozoic Eon as well as tools for a chronostratigraphic division of the late Proterozoic. It is argued that, in conjunction with geochronometric data, protistan microfossils and isotope geochemistry can furnish a means for an eventual integration of the latest Proterozoic Eon. Attention is given to the emerging methodologies of fossil protists and prokaryotes and of isotopic chemostratigraphy.

Knoll, Andrew H.↗
NASA NTRS1992

Lunar mare volcanism - Stratigraphy, eruption conditions, and the evolution of secondary crusts

Recent developments in the geological analysis of lunar mare volcanism are reviewed. Analysis of returned samples and photogeological and remote sensing studies shows that mare volcanism began prior to the end of heavy bombardment (the period of cryptomare formation), in pre-Nectarian times, and continued until the Copernical Period, the total duration approaching 3.5-4 Ga. Stratigraphic analysis shows that the flux was not constant, but peaked in early lunar history, during the Imbrian Period. Average volcanic output rate during this period was about 0.01 cu cm/a. Volcanic landforms indicate that many eruptions were of high volume and long duration. Some eruptions associated with sinuous rills may have lasted a year and emplaced 1000 cu km of lava, representing the equivalent in one year of about 70,000 yr at the average flux. The occurrence of farside maria within craters whose diameter is generally near to or less than the thickness of the crust may be accounted for by the difference between local and regional compensation.

Head, James W., III↗
NASA NTRS1993

Stratigraphy and sedimentology of the K/T boundary deposit in Haiti

The K/T boundary sequence is exposed in uplifted carbonate sediments of the southwest peninsula of Haiti. It is found at 15 localities within the Beloc formation, a sequence of limestone and marls interpreted as a monoclinal nappe structure thrust to the north. This tectonic deformation has affected the K/T boundary deposit to varying degrees. In some cases the less competent K/T deposit has acted as a slip plane leading to extensive shearing of the boundary layer, as well as duplication of the section. The presence of glassy tektites, shocked quartz, and an Ir anomaly directly link the deposit to a bolide impact. Stratigraphic and sedimentological features of the tripartite sequence indicate that it was formed by deposition from ballistic fallout of coarse tektites, emplacement of particle gravity flows and fine grained fallout of widely dispersed impact ejecta.

Carey, S.↗
NASA NTRS1995

Global stratigraphy of Venus: Analysis of a random sample of thirty-six test areas

The age relations between 36 impact craters with dark paraboloids and other geologic units and structures at these localities have been studied through photogeologic analysis of Magellan SAR images of the surface of Venus. Geologic settings in all 36 sites, about 1000 x 1000 km each, could be characterized using only 10 different terrain units and six types of structures. Mapping of such units and structures in 36 randomly distributed large regions shows evidence for a distinctive regional and global stratigraphic and geologic sequence. On the basis of this sequence we have developed a model that illustrates several major themes in the history of Venus. Most of the history of Venus (that of its first 80% or so) is not preserved in the surface geomorphological record. The major deformation associated with tessera formation in the period sometime between 0.5-1.0 b.y. ago (Ivanov and Basilevsky, 1993) is the earliest event detected. Our stratigraphic analyses suggest that following tessera formation, extensive volcanic flooding resurfaced at least 85% of the planet in the form of the presently-ridged and fractured plains. Several lines of evidence favor a high flux in the post-tessera period but we have no independent evidence for the absolute duration of ridged plains emplacement. During this time, the net state of stress in the lithosphere apparently changed from extensional to compressional, first in the form of extensive ridge belt development, followed by the formation of extensive wrinkle ridges on the flow units. Subsequently, there occurred local emplacement of smooth and lobate plains units which are presently essentially undeformed. The major events in the latest 10% of the presently preserved history of Venus are continued rifting and some associated volcanism, and the redistribution of eolian material largely derived from impact crater deposits. Detailed geologic mapping and stratigraphic synthesis are necessary to test this sequence and to address many of the outstanding problems raised by this analysis.

Basilevsky, Alexander T.↗
NASA NTRS1995

Global Stratigraphy of Venus: Analysis of a Random Sample of Thirty-Six Test Areas

The age relations between 36 impact craters with dark paraboloids and other geologic units and structures at these localities have been studied through photogeologic analysis of Magellan SAR images of the surface of Venus. Geologic settings in all 36 sites, about 1000 x 1000 km each, could be characterized using only 10 different terrain units and six types of structures. These units and structures form a major stratigraphic and geologic sequence (from oldest to youngest): (1) tessera terrain; (2) densely fractured terrains associated with coronae and in the form of remnants among plains; (3) fractured and ridged plains and ridge belts; (4) plains with wrinkle ridges; (5) ridges associated with coronae annulae and ridges of arachnoid annulae which are contemporary with wrinkle ridges of the ridged plains; (6) smooth and lobate plains; (7) fractures of coronae annulae, and fractures not related to coronae annulae, which disrupt ridged and smooth plains; (8) rift-associated fractures; and (9) craters with associated dark paraboloids, which represent the youngest 1O% of the Venus impact crater population (Campbell et al.), and are on top of all volcanic and tectonic units except the youngest episodes of rift-associated fracturing and volcanism; surficial streaks and patches are approximately contemporary with dark-paraboloid craters. Mapping of such units and structures in 36 randomly distributed large regions (each approximately 10(exp 6) sq km) shows evidence for a distinctive regional and global stratigraphic and geologic sequence. On the basis of this sequence we have developed a model that illustrates several major themes in the history of Venus. Most of the history of Venus (that of its first 80% or so) is not preserved in the surface geomorphological record. The major deformation associated with tessera formation in the period sometime between 0.5-1.0 b.y. ago (Ivanov and Basilevsky) is the earliest event detected. In the terminal stages of tessera fon-nation, extensive parallel linear graben swarms representing a change in the style of deformation from shortening to extension were formed on the tessera and on some volcanic plains that were emplaced just after, and perhaps also during the latter stages of the major compressional phase of tessera emplacement. Our stratigraphic analyses suggest that following tessera formation, extensive volcanic flooding resurfaced at least 85% of the planet in the form of the presently-ridged and fractured plains. Several lines of evidence favor a high flux in the post-tessera period but we have no independent evidence for the absolute duration of ridged plains emplacement. During this time, the net state of stress in the lithosphere apparently changed from extensional to compressional, first in the form of extensive ridge belt development, followed by the formation of extensive wrinkle ridges on the flow units. Subsequently, there occurred local emplacement of smooth and lobate plains units which are presently essentially undefortned. The major events in the latest 10% of the presently preserved history of Venus (less than 50 m.y. ago) are continued rifting and some associated volcanism, and the redistribution of eolian material largely derived from impact crater deposits.

Basilevsky, Alexander T.↗
NASA NTRS2001

The Keck "Mars 2000" Project: Using Mars Orbiter Laser Altimeter Data to Assess Geological Processes and Regional Stratigraphy Near Orcus Patera and Marte Vallis on Mars

During the Keck 'Mars 2000' summer project 10 undergraduates (rising juniors) used Mars Orbiter Laser Altimeter (MOLA) data to study a 19x14 degree region they identified as a potential Mars 2003 landing site. Here we introduce the project science and organization. Additional information is contained in the original extended abstract.

Grosfils, E. B.↗
NASA NTRS2004

Hydrocarbon Biomarker Stratigraphy of C-Isotopic Excursions Marking Chemical Changes in the Ocean with Contemporanious Biotic Extinction-Radiation Events

One paper recording progress in this topic has been accepted for publication. We report a method for the rigorous identification of biomarkers (crocetane and PMI) that may be specific for methanotrophic and methanogenic archaea and, perhaps, the process of anaerobic oxidation of methane. If catastrophic methane efflux from sub-sea methane hydrate is responsible for extinction events, as has been hypothesized by many workers, then we might expect to find biomarkers for methane oxidation in sediments marking some extinction boundaries. Unfortunately, identifying crocetane and PMI with certainty is not a trivial exercise and these biomarkers appear to have been mis-identified in a recent publication by workers from Curtin University. Barber et al. (2001) identified crocetane and PMI in sediments deposited in the basal Triassic of the Perth Basin, Australia. However, Barber et al. (2001) also found crocetane and PMI in many other sediments and oils in a way that was inconsistent with our knowledge of these systems.

Summons, Roger E.↗
NASA NTRS1998

A Vendian-Cambrian boundary succession from the northwestern margin of the Siberian Platform: stratigraphy, palaeontology, chemostratigraphy and correlation

Siberia contains several key reference sections for studies of biological and environmental evolution across the Proterozoic-Phanerozoic transition. The Platonovskaya Formation, exposed in the Turukhansk region of western Siberia, is an uppermost Proterozoic to Cambrian succession whose trace and body fossils place broad limits on the age of deposition, but do not permit detailed correlation with boundary successions elsewhere. In contrast, a striking negative carbon isotopic excursion in the lower part of the Platonovskaya Formation permits precise chemostratigraphic correlation with upper-most Yudomian successions in Siberia, and possibly worldwide. In addition to providing a tool for correlation, the isotopic excursion preserved in the Platonovskaya and contemporaneous successions documents a major biogeochemical event, likely involving the world ocean. The excursion coincides with the palaeontological breakpoint between Ediacaran- and Cambrian-style assemblages, suggesting a role for biogeochemical change in evolutionary events near the Proterozoic Cambrian boundary.

Non-NASA Center↗
NASA NTRS1995

Integrated approaches to terminal Proterozoic stratigraphy: an example from the Olenek Uplift, northeastern Siberia

In the Olenek Uplift of northeastern Siberia, the Khorbusuonka Group and overlying Kessyusa and Erkeket formations preserve a significant record of terminal Proterozoic and basal Cambrian Earth history. A composite section more than 350 m thick is reconstructed from numerous exposures along the Khorbusuonka River. The Khorbusuonka Group comprises three principal sedimentary sequences: peritidal dolomites of the Mastakh Formation, which are bounded above and below by red beds; the Khatyspyt and most of the overlying Turkut formations, which shallow upward from relatively deep-water carbonaceous micrites to cross-bedded dolomitic grainstones and stromatolites; and a thin upper Turkut sequence bounded by karst surfaces. The overlying Kessyusa Formation is bounded above and below by erosional surfaces and contains additional parasequence boundaries internally. Ediacaran metazoans, simple trace fossils, and vendotaenids occur in the Khatyspyt Formation; small shelly fossils, more complex trace fossils, and acritarchs all appear near the base of the Kessyusa Formation and diversify upward. The carbon-isotopic composition of carbonates varies stratigraphically in a pattern comparable to that determined for other terminal Proterozoic and basal Cambrian successions. In concert, litho-, bio-, and chemostratigraphic data indicate the importance of the Khorbusuonka Group in the global correlation of terminal Proterozoic sedimentary rocks. Stratigraphic data and a recently determined radiometric date on basal Kessyusa volcanic breccias further underscore the significance of the Olenek region in investigations of the Proterozoic-cambrian boundary.

Non-NASA Center↗
NASA NTRS2004

Distribution and stratigraphy of basaltic units in Maria Tranquillitatis and Fecunditatis: A Clementine perspective

Maria Tranquillitatis and Fecunditatis have been mapped based on Clementine image mosaics and derived iron and titanium maps. Impact craters served as stratigraphic probes enabling better delineation of compositionally different basaltic units, determining the distribution of subsurface basalts, and providing estimates of total basalt thickness and the thickness of the surface units. Collected data indicate that volcanism in these maria started with the eruption of low-Ti basalts and evolved toward medium- and high-Ti basalts. Some of the high-Ti basalts in Mare Tranquillitatis began erupting early and were contemporaneous with the low- and medium-Ti basalts; these units form the oldest units exposed on the mare surface. Mare Tranquillitatis is mostly covered with high- Ti basalts. In Mare Fecunditatis, the volume of erupting basalts clearly decreased as the Ti content increased, and the high-Ti basalts occur as a few patches on the mare surface. The basalt in both maria is on the order of several hundred meters thick and locally may be as thick as 1600 m. The new basalt thickness estimates generally fall within the range set by earlier studies, although locally differ. The medium- to high-Ti basalts exposed at the surfaces of both maria are meters to tens of meters thick.

Rajmon, D.↗