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David G. Howell

Publications and source records attributed to David G. Howell.

13 recordsLinked to original sources
USGS2010

Kalpin transpression tectonics, northwestern Tarim Basin, western China

The paper examines the relative importance of strike-slip faulting and lateral crustal deformations in the geologic structure of a portion of the western People's Republic of China. Deformed thrust sheets in the Kalpin area of the western PRC suggest large-scale sinistral strike-slip movement on the Aheqi fault zone along the northwestern margin of the Tarim basin. The total amount of the Cenozoic sinistral strike-slip displacement is estimated to be 311 km; this is the same magnitude of slip estimated along the Altyn Tagh fault, marking the southeastern boundary of the Tarim basin. Together, the Aheqi and Altyn Tagh faults outline the Aheqi- western Kunlun-southwestern basin-Altyn transpression tectonic system.

Aheqi Fault Zone, Tarim Basin↗
USGS2010

Paleozoic plate-tectonic evolution of the Tarim and western Tianshan Regions, western China

The plate-tectonic evolution of the Tarim basin and nearby western Tianshan region during Paleozoic time is reconstructed in an effort to further constrain the tectonic evolution of Central Asia, providing insights into the formation and distribution of oil and gas resources. The Tarim plate developed from continental rifting that progressed during early Paleozoic time into a passive continental margin. The Yili terrane (central Tianshan) broke away from the present eastern part of Tarim and became a microcontinent located somewhere between the Junggar ocean and the southern Tianshan ocean. The southern Tianshan ocean, between the Tarim craton and the Yili terrane, was subducting beneath the Yili terrane from Silurian to Devonian time. During the Late Devonian-Early Carboniferous, the Tarim plate collided with the Yili terrane by sinistral accretional docking that resulted in a late Paleozoic deformational episode. Intracontinental shortening (A-type subduction) continued through the Permian with the creation of a magmatic belt.

Tarim Region, Tianshan Region↗
USGS2010

Rejuvenation of the Kuqa Foreland Basin, northern flank of the Tarim Basin, northwest China

The Kuqa depression along the northern flank of the Tarim basin is filled with a thick sequence of Neogene and Quaternary coarse elastic continental sediments. This structural depression is part of a large foreland basin that lies south of the Tianshan—an orogenic belt of intracontinental convergence resulting from the northward propagation of stress following the collision of India with the southern margin of Eurasia.

Kuqa Foreland Basin, Tarim Basin↗
USGS2009

Basin development along the Late Mesozoic and Cainozoic California Margin: A plate tectonic margin of subduction, oblique subduction and transform tectonics

Along the Californian margin of the North American plate, the configuration and structural stability of late Mesozoic and Cainozoic basins are related to plate kinematics. Three tectonic regimes are recorded; orthogonal high-angle subduction, oblique low-angle subduction, and transform slip. During the first, regionally extensive forearc basins developed; during the second and third, borderland settings formed as a consequence of wrench faulting. In the forearc basins, sedimentological facies constitute regional belts that persist for hundreds of kilometres, with stratigraphic sequences that are 1–15 km thick. Shorelines are relatively straight, shelf facies are broad and well developed, and basin fill is composed of shallow marine, shelf and coalescing submarine-fan facies. Sediment transport in the deeper water facies commonly is parallel to the basin axis. Borderland basins reflect tectonic instability. A principal effect of wrench tectonics is the vertical reciprocation of crustal blocks. Shorelines are generally irregular, and narrow shelves pass abruptly into deep basins. Lithofacies change dramatically along strike, and stratigraphic thicknesses are variable from basin to basin, from tens of metres up to 6 km. Basin-margin facies are marked by unconformities, slump aprons, lithological pinch-outs and submarine canyon channels. Penecontemporaneous slip along the basin-margin faults complicates these lithofacies patterns. Borderland type palaeogeography is most extensively developed in the transform tectonic regime, and therefore the more seaward offshore basins are relatively depleted of terrigenous debris owing to transport barriers.

California↗
USGS2003

Rim Sim: A Role-Play Simulation

Rim Sim is a 6-hour, eight-party negotiation that focuses on creating a framework for the long-term disaster-recovery efforts. It involves a range of players from five countries affected by two natural disasters: a typhoon about a year ago and an earthquake about 6 months ago. The players are members of an International Disaster Working Group (IDWG) that has been created by an international commission. The IDWG has been charged with drawing up a framework for managing two issues: the reconstruction of regionally significant infrastructure and the design of a mechanism for allocating funding to each country for reconstruction of local infrastructure and ongoing humanitarian needs. The first issue will involve making choices among five options (two harbor options, two airport options, and one rail-line option), each of which will have three levels at which to rebuild. The second issue will involve five starting-point options. Participants are encouraged to invent other options for both issues. The goal of Rim Sim is to raise questions about traditional approaches to disaster-preparedness planning and reconstruction efforts in an international setting, in this case the Pacific Rim. Players must confront the reverberating effects of disasters and the problems of using science and technical information in decisionmaking, and are introduced to a consensus-building approach emphasizing face-to-face dialog and multinational cooperation in dealing with humanitarian concerns, as well as long-term efforts to reconstruct local and regional infrastructure. The Rim Sim simulation raises four key points: ripple effects of disasters, role of science, multiparty negotiation, and building personal relationships.

Bulletin↗
USGS2003

The North America tapestry of time and terrain

The North America Tapestry of Time and Terrain (1:8,000,000 scale) is a product of the US Geological Survey in the I-map series (I-2781). This map was prepared in collaboration with the Geological Survey of Canada and the Mexican Consejo Recursos de Minerales. This cartographic Tapestry is woven from a geologic map and a shaded relief image. This digital combination reveals the geologic history of North America through the interrelation of rock type, topography and time. Regional surface processes as well as continent-scale tectonic events are exposed in the three dimensions of space and the fourth dimension, geologic time. The large map shows the varying age of bedrock underlying North America, while four smaller maps show the distribution of four principal types of rock: sedimentary, volcanic, plutonic and metamorphic. This map expands the original concept of the 2000 Tapestry of Time and Terrain, by José F. Vigil, Richard J. Pike and David G. Howell, which covered the conterminous United States. The U.S. Tapestry poster and website have been popular in classrooms, homes, and even the Google office building, and we anticipate the North America Tapestry will have a similarly wide appeal, and to a larger audience.

IMAP↗
USGS2000

How useful is landslide hazard information? Lessons learned in the San Francisco Bay region

Landslides, worldwide and in the United States, are arguably the most costly natural hazard. Substantial landslide information is available, but much of it remains underutilized, as a disconnect exists among geologists, decision makers, and the public. The lack of a national landslide insurance policy exacerbates this situation and promotes litigation as the principal recourse for recouping landslide-damage losses. The U.S. Geological Survey's landslide investigation in the San Francisco Bay region of California provides a context for making suggestions on how Earth science information could be used more effectively.

California↗
USGS1998

Slope failure and shoreline retreat during northern California's latest El Nino

Surface processes accelerated by severe storms during the 1997–1998 El Niño event scoured hillsides and damaged property across coastal California. Technological advances such as digital mapping, exemplified here for the San Francisco Bay area but applicable elsewhere, have enabled government agencies to better describe, monitor, and predict the effects of shoreline erosion and slope failure.

California↗
USGS1989

How the growth and freeboard of continents may relate to geometric and kinematic parameters of mid-ocean spreading ridges

If the volume of continents has been growing since 4 Ga then the area of the ocean basins must have been shrinking. Therefore, by inferring a constant continental freeboard, in addition to constant continental crustal thicknesses and seawater volume, it is possible to calculate the necessary combinations of increased ridge lengths and spreading rates required to displace the seawater in the larger oceans of the past in order to maintain the constant freeboard. A reasonable choice from the various possibilities is that at 4 Ga ago, the ridge length and spreading rates were ca. 2.5 times greater than the averages of these parameters during the past 200 Ma. By 2.5 Ga ago the ridge length and spreading rate decreased to about 1.8 times the recent average and by 1 Ga ago these features became reduced to approximately 1.4 times recent averages.

Tectonophysics↗