Geosphere examines volcanic zones, the Sierra Nevada, and Utah's Confusion Range

January 15, 2014

Boulder, Colo., USA - New Geosphere papers posted online 14 Jan. cover the San Joaquin Basin in California, the Catalan Volcanic Zone in Spain, the Taupo Volcanic Zone of New Zealand, the Confusion Range of west-central Utah, and the southern U.S. Sierra Nevada. Two articles add to the "Geodynamics and Consequences of Lithospheric Removal in the Sierra Nevada, California" collection. The paper on the Confusion Range may provide a basis for new petroleum exploration in the region.

Abstracts for these and other Geosphere papers are available at http://geosphere.gsapubs.org/. Representatives of the media may obtain complimentary copies of Geosphere articles by contacting Kea Giles.

Please discuss articles of interest with the authors before publishing stories on their work, and please make reference to Geosphere in articles published. Contact Kea Giles for additional information or assistance.

Non-media requests for articles may be directed to GSA Sales and Service, gsaservice@geosociety.org.


Pliocene-Quaternary subsidence and exhumation of the southeastern San Joaquin Basin, California, in response to mantle lithosphere removal
M. Robinson Cecil et al., Tectonics Observatory at the California Institute of Technology, Pasadena, California 91125-2300, USA; robinson.cecil@csun.edu. Posted online 14 Jan. 2014, http://dx.doi.org/10.1130/GES00882.1. Special issue: Geodynamics and Consequences of Lithospheric Removal in the Sierra Nevada, California.

From the abstract: Thermomechanical models of mantle lithosphere removal from beneath the southern Sierra Nevada region, California, predict a complex spatiotemporal pattern of vertical surface displacements. M. Robison Cecil and colleagues evaluate these models by using (U-Th)/He thermochronometry, together with other paleothermometry estimates, to investigate such topographic transients. We target Tertiary strata from the Kern arch, a crescent-shaped active uplift located in the southeastern San Joaquin Basin, along the western flank of the southern Sierra Nevada.


Phreatomagmatic volcanism in complex hydrogeological environments: La Crosa de Sant Dalmai maar (Catalan Volcanic Zone, NE Spain)
Dario Pedrazzi et al., Institute of Earth Sciences Jaume Almera, ICTJA-CSIC, Group of Volcanology, SIMGEO (UB-CSIC) Lluis Sole i Sabaris s/n, 08028 Barcelona, Spain; dpedrazzi@ictja.csic.es. Posted online 14 Jan. 2014, http://dx.doi.org/10.1130/GES00959.1.

The volcano of La Crosa de Sant Dalmai (northeastern Iberian Peninsula) formed on the northern border of La Selva Basin. It is the result of a single eruptive episode characterized by four consecutive eruptive phase with alternating magma-water interaction. This volcano is an example of the way in which the edifice develops in a mixed setting characterized by a hard and soft basement with heterogeneities and differences in the hydrogeological structure of the area, and aquifer levels with different hydraulic properties and fracturing patterns. These differences clearly influenced the way in which the magma-water interaction occurred throughout the eruption and, consequently, the style of the eruption and the resulting deposits. The results obtained here can be extrapolated to other phreatomagmatic volcanoes of similar characteristics, determining the eruptive style and associated hazards in this type of volcanism.


Evolution of the intra-arc Taupo-Reporoa Basin within the Taupo Volcanic Zone of New Zealand
D.T. Downs et al., School of Environment, University of Auckland, Private Bag 92019, Auckland 1142, New Zealand; d.downs@auckland.ac.nz; ddowns84@hotmail.com. Posted online 14 Jan. 2014, http://dx.doi.org/10.1130/GES00965.1.

Our research highlights the variety of processes that are occurring in the world's most active volcanic arc: the Taupo Volcanic Zone. Some of the processes, such as tectonism, volcanism, and magmatism, are related in ways that are not fully understood, particularly as to how they affect basins that host economic and cultural assets. D.T. Downs and colleagues undertook field and laboratory studies to understand the rocks in the region and the rates at which the tectonic, volcanic, and magmatic processes occur. Their study shows that these arc processes have resulted in faster than normal basin development during eruptive episodes and slow evolution during non-volcanic episodes. Some parts of the basin also tend to undergo infilling and migration that are not uniform through time or across the entire region. This research shows that there is a lot that geoscientists still do not understand about the way that the Taupo Volcanic Zone operates or the rates at which basins may form.


The Confusion Range, west-central Utah: Fold-thrust deformation and a western Utah thrust belt in the Sevier hinterland
David C. Greene, Department of Geosciences, Denison University, Granville, Ohio 43023, USA; greened@denison.edu. Posted online 14 Jan. 2014, http://dx.doi.org/10.1130/GES00972.1.

A new study by David C. Greene of the Confusion Range in west-central Utah indicates that sedimentary rocks in the range are deformed in a zone of concentrated folding and thrust faulting that resulted in about six miles (10 km) of east-directed horizontal shortening. The Confusion Range is part of a newly recognized zone of deformation termed the western Utah thrust belt that is at least 80 miles (130 km) in length. The rock types and structures in the thrust belt are similar to areas of petroleum production in central Utah, and the new structural interpretations presented in this paper may provide a basis for new petroleum exploration in the region.


Internal deformation of the southern Sierra Nevada microplate associated with foundering lower lithosphere, California
Jeffrey Unruh et al., Lettis Consultants International, Inc., 1981 North Broadway, Suite 330, Walnut Creek, California 94596, USA; unruh.jeff@gmail.com. Posted online 14 Jan. 2014, http://dx.doi.org/10.1130/GES00936.1. Special issue: Geodynamics and Consequences of Lithospheric Removal in the Sierra Nevada, California.

From the abstract: Quaternary faulting and background seismicity in the southern Sierra Nevada microplate are concentrated east and south of the Isabella anomaly, a high-velocity body in the upper mantle interpreted to be lower Sierra lithosphere that is foundering into the asthenosphere. Jeffrey Unruh and colleagues analyze seismicity in this region to evaluate patterns of upper crustal deformation above and adjacent to the Isabella anomaly. Earthquakes in the southern Sierra and San Joaquin Valley were relocated using joint hypocentral inversion and double-difference techniques, and groups of focal mechanisms were inverted for the components of a reduced deformation rate tensor. The deformation field derived from this analysis reveals two distinct departures from horizontal plane strain associated with distributed northwest-directed dextral shear east of the Pacific plate: (1) heterogeneous extension and crustal thinning in the high Sierra and western foothills east of the Isabella anomaly; and (2) pronounced counterclockwise rotation of the principal strains from regional trends in the southwestern Sierra Nevada and across the Kern Arch. Based on comparison with a three-dimensional tomographic model, the extension in the southern Sierra is spatially associated with relatively thinner crust and anomalous low P-wave speeds in the upper mantle (40󈟆 km depth range) directly east of the Isabella anomaly. These relations suggest that seismogenic crustal thinning is localized above upwelling asthenosphere that is replacing foundering lithosphere.
-end-
http://www.geosociety.org

Geological Society of America

Related Sierra Nevada Articles from Brightsurf:

STOP THE BLEED training has saved lives from Sierra Leone to Connecticut
Two studies presented at the American College of Surgeons (ACS) Clinical Congress 2020 provide evidence that STOP THE BLEED® training is effective and has made a lifesaving difference around the world.

Families and communities are central to the recovery of Sierra Leone's former child soldiers
A study in the Journal of the American Academy of Child and Adolescent Psychiatry (JAACAP), published by Elsevier, reports that many of the former child soldiers of Sierra Leone have been accepted by their families and communities as they try to overcome their childhood trauma, according to a team led by Boston College School of Social Work Salem Professor in Global Practice, Theresa S.

Learning about reporting in a public health emergency from Sierra Leone's Ebola outbreak
In a paper publishing May 21 in PLOS Neglected Tropical Diseases, researchers have interviewed Sierra Leonean journalists about their experiences reporting during the 2014-2015 Ebola outbreak.

Prediction tool shows how forest thinning may increase Sierra Nevada snowpack
Thinning the Sierra Nevada forest by removing trees by hand or using heavy machinery is one of the few tools available to manage forests.

Latino voters in Nevada lean toward Sanders, Biden
Cornell University professor Sergio Garcia-Rios conducted polling of Latino voters in Nevada ahead of the Nevada Caucuses, indicating high levels of Latino voter support for Democrats, most notably for Bernie Sanders.

Marburg virus found in Sierra Leone bats
Scientists have detected Marburg virus in fruit bats in Sierra Leone, marking the first time the deadly virus has been found in West Africa.

Changing wildfires in the California's Sierra Nevada may threaten northern goshawks
Research in the journal Biological Conservation, published by Elsevier, suggests fire, as it becomes more frequent and severe, poses a substantial risk to goshawks in the Sierra Nevada region.

Sierra Nevada has oldest underground water recharge system in Europe
Scientists from the University of Granada, the IGME, and the Universities of Cologne and Lisbon have demonstrated that the careo irrigation channels of Sierra Nevada constitute the oldest underground aquifer recharge system on the continent.

Study explores how rock expands near soil surface in Southern Sierra Nevada
Weathering of subsurface rock in the Southern Sierra Nevada Mountains of California occurs due more to rocks expanding than from chemical decomposition.

Family and community central to recovery of Sierra Leone's former child soldiers
Many of Sierra Leone's former child soldiers have gradually earned greater acceptance from families and communities, according to a sweeping new study of their adult lives.

Read More: Sierra Nevada News and Sierra Nevada Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.