Mark Helper

This article describes the mineralogy and sources for a spectacular stone bead industry associated with the first pastoralists in eastern Africa ca. 5000-4000 CAL B.P. Around Lake Turkana, northwest Kenya, early pastoralists constructed at least seven mortuary monuments with platforms, pillars, cairns, and stone circles. Three sites-Lothagam North, Manemanya, and Jarigole-have yielded assemblages of stone and ostrich eggshell beads that adorned interred individuals. Mineralogical identification of the stone beads reveals patterns of material selection, including notable differences among the pillar sites. Geological sourcing indicates use of many local raw materials and two (amazonite and fluorite) whose known sources lie > 200 km away. The data suggest that bead-making represented a significant investment by early pastoralists in personal ornamentation. New sociopolitical factors emerged, such as access to grazing grounds and water, and definitions of self and society manifested in novel mortuary traditions as people coped with a drying, cooling climate.

textThe Condrey Mountain Schist (CMS) occupies a window through Late Triassic amphibolite facies melange in the north central Klamath Mountains in northern California and southwest Oregon. The schists owe their present level of exposure to a large structural dome centered on the Condrey Mountain Window. Transitional blueschist-greenschist facies assemblages are widespread in mafic schists in the structurally lowest levels of the window; structurally higher CMS near the window margins contains medium- to high-pressure greenschist facies parageneses. An ⁴⁰Ar/³⁹Ar crossite age indicates a late Middle Jurassic age of metamorphism. All subunits of the CMS contain evidence of progressive, polyphase deformational and metamorphic histories. The styles and geometries of minor structures in the central part of the window suggest that early folding and transposition was the result of noncoaxial deformation, and that rotational strains were replaced by irrotational flattening strains with time. Rotational strains were accompanied by the development of epidote-crossite assemblages and the growth of deerite in meta-ironstones; irrotational flattening strains were accompanied and followed by the growth of albite, actinolite, spessartine, and the Ba-silicate, cymrite. Pressure-temperature estimates, the relative ages of mineral growth and deformation, and strain geometries are consistent with, but not restricted to, a subduction zone environment. High shear strains may reflect descent and burial, whereas flattening and late, static mineral growth occur during uplift. Pressure-temperature estimates for the overlying CMS greenschists suggest temperatures similar to those in the central part of the window, but at slightly lower pressures. Thrusting of the overlying amphibolites at 150-156 Ma occurred while the amphibolites were above about 500°C. Stretching lineations indicate a movement vector of about N45W. Comparisons of the sequence and timing of metamorphic and structural events, radiometric ages, and movement directions during thrusting indicate the CMS does not represent an inlier of Klamath Western Jurassic Belt flysch but is instead an older, isolated thrust plate. Similarities with the age of metamorphism and plutonism in the overlying amphibolites suggest the two plates may be remnants of the same Middle Jurassic paired metamorphic belt.Geological Science

The effects of pyroclastic density currents (PDCs) can be devastating, so understanding their internal dynamics and evolution is important for hazard assessment. We use damaged trees located around Mount St. Helens (USA) as proxy for the dynamic pressure (Pdyn) of the PDC erupted on 18 May 1980. We recorded the location, distribution, and foliage preservation of damaged trees within the medial and distal parts of the devastated forest. Sub-meter resolution aerial photographs from a month after the eruption allow distinction between standing trees that retained foliage from those that were stripped. Heights of standing trees were estimated from the measured lengths of their shadows. The number of standing trees was counted within defined areas along the propagation paths of PDCs. From the measured tree heights, we estimated tree toppling stresses from Pdyn. Overall, Pdyn of the PDC head within the medial to distal portions of the blowdown zone ranged from 10 to 35 kPa. Pdyn likely wa...

Cohen, M. Deans, C. Evans, T. Graff, J. Head, M. Helper, K. Hodges, J. Hurtado, K. Klaus, D. Kring, H. Schmitt, J. Skinner, P. Spudis, B. Tewksbury, K. Young, A. Yingst. 1-Lunar & Planetary Institute, 3600 Bay Area Boulevard, Houston, TX, 77058, eppler@lpi.usra.edu; 2-Goddard Space Flight Center, Greenbelt, MD; 3University of Maryland; 4-NASA-Ames Research Center; 5-Johnson Space Center; 6-Brown University; 7University of Texas-Austin; 8-Arizona State University; 9-University of Texas-El Paso; 10-University of Wisconsin; 11-U.S.Geological Survey; 12-Hamilton College; 13-Planetary Science Institute.

The windward islands of the Lucayan Archipelago (Bahamas) form an Atlantic Ocean– facing transect spanning >950 km in length and 6° of latitude. The islands’ topography is largely constructed from carbonate wind-blown dunes (i.e., aeolianites) deposited during the interglacial phases of the Late Pleistocene and Holocene. New digital elevation data from satellite radar interferometry (TanDEM-X German Earth observation satellite) enables a step change in the ability to map and quantify Bahamian aeolian landforms across the archipelago. A semi-automated mapping approach that leverages object-based image analysis yields a total aeolianite area of ~1674 km2 across Great Abaco, Eleuthera, Cat, San Salvador, Long, Crooked, Acklins, and Mayaguana islands (Bahamas) and the Turks and Caicos Islands. Longitudinal axis measurements from 747 Pleistocene parabolic dunes record increasing consistency of east-west orientation with decreasing latitude. Three U.S. National Data Buoy Center data bu...

Much of the attraction, value and romance of gems lies in their beauty, rarity, and exotic origins. With ever increasing advances in techniques for gem synthesis and for improving the appearance of natural gems, traditional perceptions of gem rarity and uniqueness are changing. Using primarily ruby and emerald as examples, this lecture examines such questions as: Why are natural gems rare? What are the geologic processes that form them? Where are they found? Are natural gems different from man-made gems? What is done to improve the appearance of natural gems? Are such treatments permanent and do they affect gem values? Answers to these and other questions provides perspective on some of the many conflicting claims and confusion surrounding natural and man-made gems, and provide a stepping stone for understanding the unique processes and circumstances responsible for gem formation.

Monumental architecture is a prime indicator of social complexity, because it requires many people to build a conspicuous structure commemorating shared beliefs. Examining monumentality in different environmental and economic settings can reveal diverse reasons for people to form larger social units and express unity through architectural display. In multiple areas of Africa, monumentality developed as mobile herders created large cemeteries and practiced other forms of commemoration. The motives for such behavior in sparsely populated, unpredictable landscapes may differ from well-studied cases of monumentality in predictable environments with sedentary populations. Here we report excavations and ground-penetrating radar surveys at the earliest and most massive monumental site in eastern Africa. Lothagam North Pillar Site was a communal cemetery near Lake Turkana (northwest Kenya) constructed 5,000 years ago by eastern Africa's earliest pastoralists. Inside a platform ringed by...

1.07-1.13 Ga granites comprise almost half of the rocks in the Proterozoic (Grenvillian) Llano Uplift of central Texas and thus have contributed significantly to the evolution of basement along the southwestern margin of Laurentia. Intrusions of Town Mountain Granite in the Llano Uplift have previously been described as “anorogenic”, but recent work has shown that deformation accompanied and/or postdated intrusion of some granites.

Imagine yourself as a scientist visiting a research site on the moon for the first time, using new ways to understand the unexplored territory around you. Geologist Dr. Mark Helper will bring this scenario to life, presenting how his expertise in geological field research is assisting NASA develop new techniques for human planetary exploration. Dr. Helper will tell us of training astronauts to do geological field work, and of work with NASA roboticists at a large Canadian impact crater to test the use of robots as an aid to human planetary exploration. More info about Dr. Helper's research can be found in a short video from The University of Texas .

Human-robotic partnership should not be limited to side-by-side concurrent and coordinated activities. As advanced as robots have become, they are still slow compared to humans. Concurrent, interdependent operations risk creating situations where the human waits for the robot while it is executing or stuck. Robots that cause humans to waste precious resources such as time or life support consumables risk making human missions less productive rather than more. An alternative is to separate human and robotic activities in space and/or time but design and coordinate their activities to be complimentary. I.

MARS ANALOG STUDIES AT THE HAUGHTON-MARS PROJECT, DEVON ISLAND, HIGH ARCTIC. Pascal Lee, Stephen Braham, Matthew Deans, Terrence Fong, Essam Heggy, Mark Helper, Edward Hodgson, Stephen J. Hoffman, and John W. Schutt. Mars Institute, SETI Institute, NASA Ames Research Center, MS 245-3, Moffett Field, CA 94035-1000, USA, pascal.lee@marsinstitute.net. Simon Fraser University, Jet Propulsion Laboratory, University of Texas at Austin, Hamilton Sundstrand, Space Applications International Corp.

In this study, we investigated the geomorphic and incision history for an
~5 km reach of the northern Rio Grande gorge in New Mexico using field and
LiDAR-based geomorphic mapping and cosmogenic 3He surface exposure
dating. This wide (>1.5 km) and deep (~240 m) section of the gorge exhibits
Toreva blocks, incoherent landslides, rock falls, and slumps developed within
Servilleta Basalts and intercalated weakly consolidated Pliocene Santa
Fe Group gravels. Located deeper in the gorge topographically below the
landslides is a flight of six fill and fill-cut terraces (Qt6–Qt1) at 50, 40, 28, 21,
10, and 8 m above the modern river. 3He surface-exposure ages (1-sigma) of
multiple samples from each terrace indicate Qt6 was likely abandoned at
69.0 +8.4/−9.2 ka, Qt5 at 36.7 +13.4/−9.0 ka, Qt4 at 26.9 +5.5/−4.2 ka, Qt3 at
25.3 +3.1/−3.2 ka, and Qt2 at 24.3 +7.6/−6.7 ka. We interpret the terraces to
record three aggradation-incision cycles during the past ~70 k.y. The most
prominent terrace surface (Qt4) falls within MIS 2 and appears to closely
track incision associated with Pinedale ice retreat. Previous work suggests
that the initiation of gorge incision occurred between ca. 440–800 ka, which
suggests average incision rates prior to the formation of the highest terrace
(Qt6) of 260–512 m/m.y. Average incision from ca. 70 ka to present appears
faster, with maximum rates of ~752 m/m.y. Compared to incision rates for
nearby river systems, rates along the Rio Grande are nearly twice as fast
over both middle and late Pleistocene to Holocene timescales, suggesting
a persistent driving force for incision that is unique to this river system.
Rates of dynamic surface uplift and/or slip along basin-bounding normal
faults associated with the Rio Grande rift are over an order of magnitude
too small to explain the fast incision; thus we suggest the most probable
driver of incision is drainage basin (re-)integration and transient knickpoint
migration due to the capture of the northern San Luis Basin during the
middle Pleistocene, superimposed on a strong climatic signature in the
late Pleistocene.

Mid-Proterozoic Hondo Group metasediments in the western Picuris Mountains, New Mexico clearly display 3 generations of previously recognized penetrative, synmetamorphic structures and a previously undocumented forth generation of overprinting folds with an associated axial planar foliation. The earliest structures include: (1) a bedding-parallel S[sub 1] foliation and rare, rootless, intrafolial F[sub 1] folds; (2) north-verging, west-trending F[sub 2] folds and an axial planar metamorphic foliation (S[sub 2]); (3) a steeply dipping, N-S striking crenulation cleavage (S[sub 3]). In the Piedra Lumbre region, southwest-plunging, open, upright chevron and box folds (F[sub 4]) locally reorient F[sub 2], S[sub 2] and S[sub 3] crenulations. The largest F[sub 4] folds in the Piedra Lumbre region have half-wavelengths of 500 meters. An associated nearly vertical foliation (S[sub 4]) overprints the first three foliations. The S[sub 4] foliation is a crenulation cleavage in micaceous layers ...

... Lorenzo Flueckiger3, Linda Kobayashi1, Susan Lee2, David Lees3, Eric Park2, Estrellina Pacis4, Liam Pedersen3, Debbie Schreckenghost5, Trey ... Robot Driver (“Driver”) directly operates robot mobility, also commands ”real-time” science ops, such as panning cameras to look ...

... The other nongeologist would also be the primary medical officer of the crew, backed up by cross-training on the part of one of ... The cur-rent Space Shuttle EVA astronauts appear to be in much better condition, particularly relative to long-duration use of the EVA gloves, possibly ...

Chandrayaan-1 all suggest that the lunar subsurface contains traces of cometary ice in the permanently shadowed areas at the lunar poles. Although the presence of ice in the lunar subsurface is supported by an increasing set of remote sensing observations, its depth, composition, and concentration remain poorly quantified. Quantifying these parameters will increase our understanding of the ice transport to the lunar surface and are vital to future plans to use it as a potential resource for long-term human presence. Future EVAs and ...

Advanced planetary field geology, which will include the coordination of human and robotic missions of scientific exploration, will be greatly enhanced by the use of “smart tools” to provide heightened sensory awareness of the landscape. We can imagine an array of portable, multi-use tools that can be employed by astronaut explorers and their robotic counterparts to elucidate subtle distinctions among geologic map units or to “high-grade” samples for return to Earth laboratories. One smart tool that may be extremely useful for ...

We performed a simulated EVA experiment and a robotic follow-up using Lidar, GPR, Panoramic, and Micro-Imaging cameras and XRF to re-explore the sites with the main objective of providing metric observations to quantify in situ subsurface ice presence.