Showing papers in "Gsa Today in 2003"

Celestial driver of Phanerozoic climate

Abstract: Atmospheric levels of CO2 are commonly assumed to be a main driver of global climate. Independent empirical evidence suggests that the galactic cosmic ray flux (CRF) is linked to climate variability. Both drivers are presently discussed in the context of daily to millennial variations, although they should also operate over geological time scales. Here we analyze the reconstructed seawater paleotemperature record for the Phanerozoic (past 545 m.y.), and compare it with the variable CRF reaching Earth and with the reconstructed partial pressure of atmospheric CO2 (pCO2). We find that at least 66% of the variance in the paleotemperature trend could be attributed to CRF variations likely due to solar system passages through the spiral arms of the galaxy. Assuming that the entire residual variance in temperature is due solely to the CO2 greenhouse effect, we propose a tentative upper limit to the long-term “equilibrium” warming effect of CO2, one which is potentially lower than that based on general circulation models.

Initiation of the Himalayan Orogen as an Early Paleozoic Thin-skinned Thrust Belt

Abstract: Research by many workers in various regions of the Himalaya, combined with our recent geologic and geochronologic studies in Nepal, indicate that fundamental aspects of the Himalayan orogen originated in an early Paleozoic thrust belt and are unrelated to Tertiary IndiaAsia collision Manifestations of early Paleozoic tectonism include ductile deformation, regional moderate- to highgrade metamorphism, large-scale southvergent thrusting, crustal thickening and the generation of granitic crustal melts, uplift and erosion of garnet-grade rocks, and accumulation of thick sequences of synorogenic strata Determining the relative contributions of early Paleozoic versus Tertiary tectonism constitutes a significant challenge in understanding the Himalayan orogen

High-resolution lidar topography of the Puget Lowland, Washington - A bonanza for earth science

Abstract: More than 10,000 km2 of high-resolution, public-domain topography acquired by the Puget Sound Lidar Consortium is revolutionizing investigations of active faulting, continental glaciation, landslides, and surficial processes in the seismically active Puget Lowland. The Lowland—the population and economic center of the Pacific Northwest—presents special problems for hazards investigations, with its young glacial topography, dense forest cover, and urbanization. Lidar mapping during leaf-off conditions has led to a detailed digital model of the landscape beneath the forest canopy. The surface thus revealed contains a rich and diverse record of previously unknown surface-rupturing faults, deep-seated landslides, uplifted Holocene and Pleistocene beaches, and subglacial and periglacial features. More than half a dozen suspected postglacial fault scarps have been identified to date. Five scarps that have been trenched show evidence of large, Holocene, surfacerupturing earthquakes.

Magma transport and coupling between deformation and magmatism in the continental lithosphere

Abstract: JANUARY 2003, GSA TODAY ABSTRACT The mechanisms by which magma is generated and transported through continental crust and how these processes affect the chemical and mechanical evolution of the lithosphere are some of the least understood issues of continental dynamics. We report here on the evolution of an unusually well-exposed early Mesozoic arc that originally formed along the ancient margin of Gondwana and is now located in western New Zealand. The pre-Cenozoic configuration and deeply eroded character of this arc lead us to the following conclusions about magmatism and deformation at 10–50 km paleodepths: (1) The mafic-intermediate composition of the lower crust and the mineral reactions controlling melt production strongly influenced pathways of melt transfer and controlled the mechanical behavior of the lithosphere during orogenesis. (2) Evolving lithospheric strength profiles during magmatism and convergence produced transient periods of vertical coupling and decoupling of crustal layers. (3) Late orogenic extension was driven by plate interactions rather than by gravitational forces and a weak lower crust.

From Impact to Riches: Evolution of Geological Understanding as Seen at Sudbury, Canada

Abstract: investigation shows that it contains magnetic iron ore and magnetic iron pyrites generally disseminated throughout the rock, the former in very small grains: titaniferous iron was found associated with the magnetic ore, and a small quantity of nickel and copper with the pyrites. These remarks were not followed up. It was only after sulfides were revealed in a new railway cutting in 1883 as a result of the building of Canada’s first transcontinental railroad, the Canadian Pacific, that a prospecting and staking rush started in the area. The first production at Sudbury occurred in 1886 (Fig. 1). During the late nineteenth and early twentieth centuries, laterites in New Caledonia satisfied the majority of the world’s demand for nickel, but by 1905 the sulfide mines at Sudbury had overtaken New Caledonia as the

Mid-continental magnetic declination: A 200-year record starting with Lewis and Clark

Abstract: Compass and sextant observations by Meriwether Lewis and William Clark are combined to provide the oldest determinations of the magnetic declination in the continental interior of the United States. Over the past 200 years, the magnetic declination near St. Louis has changed from an azimuth of 7.7° east to 0° today. The 1803–1806 declinations are essential to interpreting the travel legs made by Lewis and Clark on their historic journey, and could be used to test and improve existing magnetic

Research and Education in Taiwan

Abstract: I found my seat in the DC-10, grateful to have collected enough air miles in the past year to qualify for the “Economy Plus” section and five more inches of legroom. The passenger in the seat next to me pulled out a few familiar items: a schedule, a stack of papers to grade. I turned to him and said, “Are you on your way to the Penrose Conference, by any chance?” He confirmed my suspicions. We introduced ourselves, and, not recognizing my name, he said, “You must be from the tectonics end of things.” “Well, sort of,” I replied. “I’m actually attending this meeting as an educator.” He looked surprised, so I elaborated. “I teach geology at a community college in New Mexico. I’m a structural geologist, too, but the interdisciplinary nature of this topic could provide some great educational opportunities.” “Oh,” he said. “Wow. Good luck.” We chatted occasionally over the next 13 hours or so until the plane touched down in Taipei, Taiwan. Then he took a cab and I took a bus to the hotel. My attendance at the “Tectonics, Climate, and Landscape Evolution” Penrose Conference in Taiwan in January 2003 was something of an experiment. Penrose Conferences, as most GSA members are aware, are typically subject-specific work sessions for researchers who share interests or, in this case, approach similar problems from a wide range of backgrounds. To explore the relationships between tectonics, climate, and landscape evolution, the conveners had accepted applications from meteorologists, geophysicists, structural geologists, geomorphologists, experimental sedimentologists, and GIS experts from all over the world. The topic immediately caught my eye—few things appeal to me more as a teacher than the chance to connect several concepts together into an interdisciplinary exploration. Many scientists and educators have made these broad connections before: plate tectonics built the Cascades, for example, which create a long rainshadow in eastern Oregon, where a daunting desert landscape looks more like Nevada than the Oregon coast. The chance to explore these interactions in more detail with experts was compelling. Having made a choice to teach at a community college rather than to pursue a research career, I had little to contribute to the conference. Community college instructors generally teach 15 credit hours per semester (four to five classes), leaving little time for research and often making it difficult to stay current within their discipline. There is no chance to teach higher level classes, as the students who would potentially take those courses have transferred to four-year colleges by that time. I thought I might be able to experience the excitement of

Anonymous Reviews—Are the Pros Worth the Cons?

Abstract: One of the practices that is said to have stimulated science in the western world is the open criticism of our work and free debate in the forum of refereed journals. It is this dialectical exchange of views that has ensured the accuracy of our observations and the logic of our conclusions. Today, however, we have a system in which little if any of this exchange appears in the pages of our journals. Instead, it takes place before publication in a review system that is designed to correct errors and clarify our writing before it appears in print. To do this, an editor, who may or may not be conversant with the subject of the paper, selects a set of reviewers whose identity is usually unknown to the author. On this basis, a judgment is reached, and an author may be told that his work is unacceptable or cannot be published unless certain parts are altered in accordance with the views of a secret reviewer.

Raymond Cecil Moore: A Great 20th Century Geological Synthesizer

Abstract: R.C. Moore (1892–1974), administrator, researcher, teacher, world-class stratigrapher and paleontologist, linguist, and artist—a man of many talents—was born 20 February 1892 in Roslyn, Washington, in the Wenatchee Mountains. The eldest of four children born to Bernard Harding Moore, a Baptist minister of Irish descent, and Winifred Denney of Elk Falls, Kansas, Moore was educated at Denison University (Ohio) and granted an A.B. degree with honors in the classics in 1913. At Denison, he was introduced to geology by the learned geologist Frank Carney and was such a good student that he was hired to teach geology his senior year while Carney was on leave. Moore continued his studies in geology at the University of Chicago and was awarded a doctorate (summa cum laude) three years later for his dissertation on the Early Mississippian formations of Missouri, supervised by Stuart Weller. His education at Chicago included instruction from the giants of the day—Weller, Thomas C. Chamberlain, Samuel W. Williston, and Rollin D. Salisbury. On completion of his studies at Chicago in 1916, he was hired as an assistant professor of geology at the University of Kansas and also state geologist and director of the State Geological Survey of Kansas. Moore replaced W.H. Twenhofel, who left for the University of Wisconsin after having been state geologist for just one year. Twenhofel had replaced the retiring Erasmus “Daddy” Haworth, although Haworth continued as chairman of the department (Merriam, 1975, 2002; Maples and Buchanan, 1989). Almost immediately, Moore turned his attention to refining the PermoPennsylvanian stratigraphy of the Midcontinent. His attention to detail allowed him to correlate individual beds as thin as 5 cm from Nebraska southward to Oklahoma; his measured sections are impeccable. From this detail, he was able to formulate his ideas on cyclic sedimentation and “genetic stratigraphy,” as he phrased it, a forerunner of what we know today as sequence stratigraphy. He was particularly interested in the succession of depositional environments and he defined them by unique fossil assemblages. Many of these studies were the basis for a series of Kansas Geological Society field conferences in the 1930s, a summary publication on the Pennsylvanian of Kansas in 1936, and the revised and updated geological map of Kansas, published in 1937 with co-author Kenneth K. Landes. His flair for organization and technicalities was evident with these activities as he coerced and cajoled his colleagues into a uniform stratigraphic code for the Midcontinent. (He later showed these same abilities as chairman of the U.S. Committee on Stratigraphic Nomenclature and the Committee on Zoological Nomenclature.) Moore envisioned individual cyclothems to consist of genetically related units, that is, a succession of sediment types deposited in a shallow epicontinental sea by a single advance and retreat of the sea. He extended the original concepts of J.A. Udden and J.M. Weller on cyclothems to a bundle of related cyclothems (usually five, each represented by the culminating marine limestone separated by thick nonmarine clastics), which he termed a “megacyclothem.” Moore noted testily: