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Full-Text Articles in Physical Sciences and Mathematics
Sedimentation In A Blast-Zone Lake At Mount St. Helens, Washington-Implications For Varve Formation, Roger Y. Anderson, Edward Nuhfer, Walter E. Dean
Sedimentation In A Blast-Zone Lake At Mount St. Helens, Washington-Implications For Varve Formation, Roger Y. Anderson, Edward Nuhfer, Walter E. Dean
United States Geological Survey: Staff Publications
Sediment collected in traps in a newly formed lake in the blast-impact area at Mount St. Helens recorded a sediment yield that is about two orders of magnitude greater than for comparable basins with vegetation and similar precipitation. Most sediment was mobilized by storms and run off at the onset of the wet season. The sedimentation response to strongly seasonal precipitation, in the absence of vegetation, produced turbidites and graded annual couplets. The style of sedimentation suggests an alternate mechanism for the formation of long sequences of graded clastic varves.
Magnetic Polarity Stratigraphy And Mammalian Fauna Of The Deseadan (Late Oligocene-Early Miocene) Salla Beds Of Northern Bolivia, Bruce J. Macfadden, Kenneth E. Campbell Jr., Richard L. Cifelli, Oscar Siles, Noye M. Johnson, Charles W. Naeser, Peter K. Zeitler
Magnetic Polarity Stratigraphy And Mammalian Fauna Of The Deseadan (Late Oligocene-Early Miocene) Salla Beds Of Northern Bolivia, Bruce J. Macfadden, Kenneth E. Campbell Jr., Richard L. Cifelli, Oscar Siles, Noye M. Johnson, Charles W. Naeser, Peter K. Zeitler
United States Geological Survey: Staff Publications
The Salla Beds contain a rich assemblage of Deseadan mammals that traditionally has been considered of early Oligocene age. These deposits, located 90-100 km SE of La Paz, Bolivia, consist of more than 540 m of principally fluviatile clays and silts with numerous interbedded tuffs. Paleomagnetic samples were collected from 104 sites spaced at stratigraphic intervals of about 6 m. As a result of thermal demagnetization (at 400°Co r greater), unambiguous polarities were determined for 76 of the 104 originally sampled ites. The pattern of reversals, stage of evolution of the fossils, and preliminary isotopic dates (including a K/Ar age …
Soils And The Location Of Cacao Orchards At A Maya Site In Western Belize, Daniel R. Muhs, Robert R. Kautz, J. Jefferson Mackinnon
Soils And The Location Of Cacao Orchards At A Maya Site In Western Belize, Daniel R. Muhs, Robert R. Kautz, J. Jefferson Mackinnon
United States Geological Survey: Staff Publications
Cacao was one of the most important crops of the lowland Maya. Ethnohistoric sources document that the Postclassic-Colonial Period Maya settlement of Tipu in western Belize was an important cacao-growing center, yet evidence of where the cacao was grown is not apparent. We analysed the suitability of floodplain, terrace, and bedrock soils for cacao cultivation. Our results indicate that the soils most likely to have been used for cacao growth were those on the modem floodplain of the Macal River, based on their suitable physical and chemical properties. In addition, buried stone walls of Late Classic or Postclassic age that …
An Evaluation Of Uranium-Series Dating Of Fossil Echinoids From Southern California Pleistocene Marine Terraces, Daniel R. Muhs, Los Angeles County Museum Of Natural History, Los Angeles, Ca
An Evaluation Of Uranium-Series Dating Of Fossil Echinoids From Southern California Pleistocene Marine Terraces, Daniel R. Muhs, Los Angeles County Museum Of Natural History, Los Angeles, Ca
United States Geological Survey: Staff Publications
Fossil sea urchins (Strongylocentrotus) from Pleistocene marine terraces on the southern California Channel Islands have been dated by the uranium-series method in order to test the suitability of echinoids for dating marine terraces. Results indicate that urchin plates and spines do not behave as closed systems with respect to both uranium and thorium. Calculated ages based on these data do not agree with uranium-series ages (120,000 and 127,000 yrs) obtained previously from corals from the same localities. Thus, fossil sea urchins (Strongylocentrotus) are not considered suitable for uranium-series dating of Pleistocene marine terrace deposits.
A Frotarsius Chatrathi, First Tarsiiform Primate (? Tarsiidae) From Africa, Elwyn L. Simons, Thomas M. Bown
A Frotarsius Chatrathi, First Tarsiiform Primate (? Tarsiidae) From Africa, Elwyn L. Simons, Thomas M. Bown
United States Geological Survey: Staff Publications
Tarsiiform primates have long been regarded as a Laurasian group, with an extensive fossil record in the Eocene of North America and EuropeI and two important but less well-known records from Asia.
In Situ Stress, Natural Fracture Distribution, And Borehole Elongation In The Auburn Geothermal Well, Auburn, New York, Stephen H. Hickman, John H. Healy, Mark D. Zoback
In Situ Stress, Natural Fracture Distribution, And Borehole Elongation In The Auburn Geothermal Well, Auburn, New York, Stephen H. Hickman, John H. Healy, Mark D. Zoback
United States Geological Survey: Staff Publications
Hydraulic fracturing stress measurements and a borehole televiewer survey were conducted in a 1.6-km-deep well at Auburn, New York. This well, which was drilled at the outer margin of the Appalachian Fold and Thrust Belt in the Appalachian Plateau, penetrates approximately 1540 m of lower Paleozoics edimentary rocks and terminates 60 m into the Precambrian marble basement. Analysis of the hydraulic fracturing tests indicates that the minimum horizontal principal stress increases in a nearly linear fashion from 9.9 ± 0.2 MPa at 593 m to 30.6 ± 0.4 MPa at 1482 m. The magnitude of the
maximum horizontal principal stress …
Hydraulic Fracturing Stress Measurements At Yucca Mountain, Nevada, And Relationship To The Regional Stress Field, J. M. Stock, J. H. Healy, S. H. Hickman, M. D. Zoback
Hydraulic Fracturing Stress Measurements At Yucca Mountain, Nevada, And Relationship To The Regional Stress Field, J. M. Stock, J. H. Healy, S. H. Hickman, M. D. Zoback
United States Geological Survey: Staff Publications
Hydraulic fracturing stress measurements and acoustic borehole televiewer logs were run in holes USW G-1 and USW G-2 at Yucca Mountain as part of the Nevada Nuclear Waste Storage Investigations for the U.S. Department of Energy. Eight tests in the saturated zone, at depths from 646 to 1288 m, yielded values of the least horizontal stress Sh that are considerably lower than the vertical principal stress Sv. In tests for which the greatest horizontal principal stress SH could be determined it, was found to be less than S ν, indicating a normal faulting stress regime. …
Permeability Versus Depth In The Upper Oceanic Crust' In Situ Measurements In Dsdp Hole 504b, Eastern Equatorial Pacific, Roger N. Anderson, Mark D. Zoback, Stephen H. Hickman, Robin L. Newmark
Permeability Versus Depth In The Upper Oceanic Crust' In Situ Measurements In Dsdp Hole 504b, Eastern Equatorial Pacific, Roger N. Anderson, Mark D. Zoback, Stephen H. Hickman, Robin L. Newmark
United States Geological Survey: Staff Publications
In situ permeabilities measured within the upper kilometer of oceanic crust in hole 504B on the south flank of the Costa Rica Rift decrease exponentially from 10-13 to 10-14 m2 in layer 2A (the upper 150m) to 10 -15 to 10-17 m2 in layer 2B (150-550 m into basement), and to 10-17 m2 and lower in layer 2C (deeper than 550 m). We estimate the permeability (k) versus depth (z) to vary as k(z)=0.11e(-z/50)x 10-12 m2. If this permeability versus depth function is representative of …
Well Bore Breakouts And In Situ Stress, Mark D. Zoback, Daniel Moos, Larry Mastin, Roger N. Anderson
Well Bore Breakouts And In Situ Stress, Mark D. Zoback, Daniel Moos, Larry Mastin, Roger N. Anderson
United States Geological Survey: Staff Publications
The detailed cross-sectional shape of stress induced well bore breakouts has been studied using specially processed ultrasonic borehole televiewer data. We show breakout shapes for a variety of rock types and introduce a simple elastic failure model which explains many features of the observations. Both the observations and calculations indicate that the breakouts define relatively broad and flat curvilinear surfaces which enlarge the borehole in the direction of minimum horizontal compression. This work supports the hypothesis that breakouts result from shear failure of the rock where the compressive stress concentration around the well bore is greatest and that breakouts can …
On The Classification Of The Early Tertiary Erinaceomorpha (Insectivora, Mammalia), Michael J. Novacek, Thomas M. Bown, David Schankler
On The Classification Of The Early Tertiary Erinaceomorpha (Insectivora, Mammalia), Michael J. Novacek, Thomas M. Bown, David Schankler
United States Geological Survey: Staff Publications
Definitions are provided for three Early Tertiary families of Erinaceomorpha. The family Dormaaliidae includes Dormaalius, Macrocranion, Scenopagus, Ankylodon, Crypholestes, Sespedectes, and Proterixoides.