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Sample records for southwestern neogene bland

  1. Structural lineaments and neogene volcanism in southwestern Luzon

    NASA Astrophysics Data System (ADS)

    Wolfe, John A.; Self, Stephen

    The Philippine Islands have at least 15 active composite volcanoes and as many more that are fumarolic or dormant. About 20 calderas of Pleistocene age are known so far. Southwestern Luzon, one of the major volcanic districts of the country, contains three young composite volcanoes, four in a fumarolic stage, and over 200 vents of Pliocene-Pleistocene age within 150 km of Manila. There are three large calderas in this zone with a fourth a short distance south on Mindoro Island, plus four summit calderas. One of the most striking features is the Bataan Lineament, a chain of 27 volcanic vents, only one at present active, which marks the western side of the district. The main segment extends from Naujan caldera in the south (on Mindoro Island) on a strike of N31°W through Batangas Bay caldera, Mataas Na Gulod (a summit caldera), Corregidor Island (a small caldera), to Mount Mariveles and Mount Natib on the Bataan peninsula. With a bend of 30° at Mount Natib, the lineament continues northward for another 100 km, giving a total length of 320 km. Here it includes Mount Pinatubo, which is active, and several other vents. The Bataan Lineament is a volcanic arc, with perhaps some extensional element, above the subduction zone of the Manila Trench, dipping eastward under Luzon. Another major volcanic element is the Verde Island transform, which forms a zone across southwest Luzon, including 10 or more volcanoes. Activity extended from the lower Miocene with periodic eruptions until the late Pleistocene. Two volcanoes may be in a waning (fumarolic) stage and have thermal areas. Near the western end of this lineament, recent rifting may have occurred, and presently it is a zone of intense seismic activity. In the zone between the Bataan and Verde Island lineaments, several major volcanoes have developed including Laguna de Bay and Taal volcano-tectonic depressions. Large volume ignimbrite-forming eruptions may have taken place from Laguna de Bay caldera approximately 1.0 m

  2. The Progreso Basin Province of Northwestern Peru and Southwestern Ecuador: Neogene and Cretaceous-Paleogene Total Petroleum Systems

    USGS Publications Warehouse

    Higley, Debra K.

    2004-01-01

    The Progreso Basin province (6083) in northwestern Peru and southwestern Ecuador consists of the Paleogene Santa Elena block and Peru Bank, and the Neogene Tumbes-Progreso subbasin. The Santa Elena block and Peru Bank are part of the Cretaceous-Paleogene Total Petroleum System (TPS)(608302), which contains the Cretaceous-Paleogene Santa Elena Block Assessment Unit (60830201). The Tumbes- Progreso subbasin includes the Neogene TPS (608301) and associated Neogene Pull-Apart Basin Assessment Unit (60830101). The complex tectonic history of the Progreso Basin province influenced depositional and erosional patterns across the region, and also the location, timing, and types of seals, traps, possible source and reservoir rocks, and hydrocarbon generation and migration. Marine shales that are interbedded with and overlie reservoir intervals are the probable hydrocarbon source rocks. Timing of hydrocarbon generation and migration was probably Miocene and younger, following creation of the Tumbes-Progreso subbasin by movement along the Dolores-Guayaquil megashear. More than 220 million barrels of oil (MMBO) and 255 billion cubic feet of gas (BCFG) have been produced from the Progreso Basin province. The means of estimated recoverable oil, gas, and natural gas liquids (NGL) resources from undiscovered fields in the province are 237 MMBO, 695 BCFG, and 32 MMB NGL, respectively. The means of estimated recoverable oil, gas, and NGL resources from undiscovered onshore fields are 45 MMBO, 113 BCFG, and 5 MMBNGL, and from undiscovered offshore fields are 192 BBO, 582 BCFG, and 27 MMBNGL. These are USGS grown undiscovered resources that were determined by using a minimum field size of 1 million barrels of oil equivalent.

  3. Neogene tectonic evolution of the southwestern Alboran Basin as inferred from seismic data off Morocco

    SciTech Connect

    Chalouan, A.; Saji, R.; Michard, A.; Bally, A.W.

    1997-07-01

    The southwestern part of the western Mediterranean Alboran Basin, including part of the Alboran ridge (Xaouen Bank), was investigated through the analysis of 28 intersecting multichannel seismic lines. The seismic stratigraphy is tied to the Amoco well El-Jebha 1. Five seismic units or subunits are described from the Quaternary to the middle (and lower?) Miocene. The acoustic basement is interpreted to be mainly Paleozoic and Triassic metamorphic rocks of the Alboran Domain nappes, and, in places, middle Miocene-Messinian calc-alkalic volcanics. In the depocenters, the thickness of the sedimentary infill (mostly clays and turbidites) exceeds 9 km. Normal faults of middle Miocene-Tortonian age are broadly parallel to the coast, and dip either seaward or landward. They were mostly inverted during pre- and post-Messinian episodes of compression, which formed a set of en echelon, north-verging faulted folds in the Alboran ridge area, in relation with sinistral movement along the offshore projection of the Jebha fault. After Pliocene subsidence, a final episode of compression reactivated the earlier folds and pushed the Alboran ridge onto the Moroccan slope. The complex structural history suggests many structural and stratigraphic potential hydrocarbon traps. A high-resolution seismic survey could lead to the definition of new exploration plays.

  4. Late Neogene and Early Quaternary Paleoenvironmental and Paleoclimatic Conditions in Southwestern Europe: Isotopic Analyses on Mammalian Taxa

    PubMed Central

    Domingo, Laura; Koch, Paul L.; Hernández Fernández, Manuel; Fox, David L.; Domingo, M. Soledad; Alberdi, María Teresa

    2013-01-01

    Climatic and environmental shifts have had profound impacts on faunal and floral assemblages globally since the end of the Miocene. We explore the regional expression of these fluctuations in southwestern Europe by constructing long-term records (from ∼11.1 to 0.8 Ma, late Miocene–middle Pleistocene) of carbon and oxygen isotope variations in tooth enamel of different large herbivorous mammals from Spain. Isotopic differences among taxa illuminate differences in ecological niches. The δ13C values (relative to VPDB, mean −10.3±1.1‰; range −13.0 to −7.4‰) are consistent with consumption of C3 vegetation; C4 plants did not contribute significantly to the diets of the selected taxa. When averaged by time interval to examine secular trends, δ13C values increase at ∼9.5 Ma (MN9–MN10), probably related to the Middle Vallesian Crisis when there was a replacement of vegetation adapted to more humid conditions by vegetation adapted to drier and more seasonal conditions, and resulting in the disappearance of forested mammalian fauna. The mean δ13C value drops significantly at ∼4.2−3.7 Ma (MN14–MN15) during the Pliocene Warm Period, which brought more humid conditions to Europe, and returns to higher δ13C values from ∼2.6 Ma onwards (MN16), most likely reflecting more arid conditions as a consequence of the onset of the Northern Hemisphere glaciation. The most notable feature in oxygen isotope records (and mean annual temperature reconstructed from these records) is a gradual drop between MN13 and the middle Pleistocene (∼6.3−0.8 Ma) most likely due to cooling associated with Northern Hemisphere glaciation. PMID:23717470

  5. Late neogene and early quaternary paleoenvironmental and paleoclimatic conditions in southwestern Europe: isotopic analyses on mammalian taxa.

    PubMed

    Domingo, Laura; Koch, Paul L; Hernández Fernández, Manuel; Fox, David L; Domingo, M Soledad; Alberdi, María Teresa

    2013-01-01

    Climatic and environmental shifts have had profound impacts on faunal and floral assemblages globally since the end of the Miocene. We explore the regional expression of these fluctuations in southwestern Europe by constructing long-term records (from ~11.1 to 0.8 Ma, late Miocene-middle Pleistocene) of carbon and oxygen isotope variations in tooth enamel of different large herbivorous mammals from Spain. Isotopic differences among taxa illuminate differences in ecological niches. The δ(13)C values (relative to VPDB, mean -10.3 ± 1.1‰; range -13.0 to -7.4‰) are consistent with consumption of C3 vegetation; C4 plants did not contribute significantly to the diets of the selected taxa. When averaged by time interval to examine secular trends, δ(13)C values increase at ~9.5 Ma (MN9-MN10), probably related to the Middle Vallesian Crisis when there was a replacement of vegetation adapted to more humid conditions by vegetation adapted to drier and more seasonal conditions, and resulting in the disappearance of forested mammalian fauna. The mean δ(13)C value drops significantly at ~4.2-3.7 Ma (MN14-MN15) during the Pliocene Warm Period, which brought more humid conditions to Europe, and returns to higher δ(13)C values from ~2.6 Ma onwards (MN16), most likely reflecting more arid conditions as a consequence of the onset of the Northern Hemisphere glaciation. The most notable feature in oxygen isotope records (and mean annual temperature reconstructed from these records) is a gradual drop between MN13 and the middle Pleistocene (~6.3-0.8 Ma) most likely due to cooling associated with Northern Hemisphere glaciation. PMID:23717470

  6. Neogene climate change and emergence of C 4 grasses in the Namib, southwestern Africa, as reflected in ratite 13C and 18O

    NASA Astrophysics Data System (ADS)

    Ségalen, Loïc; Renard, Maurice; Lee-Thorp, Julia A.; Emmanuel, Laurent; Le Callonnec, Laurence; de Rafélis, Marc; Senut, Brigitte; Pickford, Martin; Melice, Jean-Luc

    2006-04-01

    Stable light isotopes in ratite eggshells have been shown to be reliable indicators of shifts in climate and environmental conditions in the past. Here, we show that δ18O and δ13C values in fossil and modern ratite eggshells collected in the aeolianite deposits of the southern and central Namib Desert track regional distinctions and global climate shifts throughout the Neogene. δ18O values, although variable, are consistently higher in the central compared to the southern Namib throughout the record. δ18O trends during the Miocene differ for the two regions, but track each other post-Miocene. Throughout the Miocene, δ13C values for ratite eggshells from both the central and southern Namib regions are indistinguishable showing that the flora remained C 3 throughout. The overall negative (- 3‰) shift in mean values for Miocene biostratigraphic zones is consistent with the response of C 3 photosynthesis to pCO 2 shifts from 180 to 320 ppmv as estimated from marine alkenone studies and/or evolution of the δ13C of the atmospheric CO 2. Evidence for C 4 plants occurs post-Miocene, with the development of the southern, winter rainfall and central/northern, summer rainfall zonation apparent today. These data provide independent corroboration that the expansion of C 4-dominated ecosystems after ˜ 7 Ma cannot be attributed to a reduction of pCO 2 below a 500 ppmv threshold, as earlier proposed. Proliferation of C 4 plants in the Namib after ˜ 5 Ma and, elsewhere, may be related rather to energy budgets and rainfall seasonality shifts resulting from large-scale atmospheric and oceanic circulation reorganisation.

  7. Uranus - Beneath that bland exterior

    NASA Technical Reports Server (NTRS)

    Simpson, Richard A.; Miner, Ellis D.

    1989-01-01

    Findings made by the Voyager missions regarding the atmosphere, magnetic field, rings, and satellites of Uranus are reviewed. The reasons for the bland appearance of the planet are addressed, and the use of radio and infrared instruments to determine the rotational speeds of the planet and atmosphere, the equatorial radius, and the atmospheric temperature is discussed. The corkscrew magnetic field and the dark, almost dust-free rings are described. The most significant features of the largest Uranian moons are mentioned.

  8. Camp Blanding Lightning Mapping Array

    NASA Technical Reports Server (NTRS)

    Blakeslee,Richard; Christian, Hugh; Bailey, Jeffrey; Hall, John; Uman, Martin; Jordan, Doug; Krehbiel, Paul; Rison, William; Edens, Harald

    2011-01-01

    A seven station, short base-line Lightning Mapping Array was installed at the Camp Blanding International Center for Lightning Research and Testing (ICLRT) during April 2011. This network will support science investigations of Terrestrial Gamma-Ray Flashes (TGFs) and lightning initiation using rocket triggered lightning at the ICLRT. The network operations and data processing will be carried out through a close collaboration between several organizations, including the NASA Marshall Space Flight Center, University of Alabama in Huntsville, University of Florida, and New Mexico Tech. The deployment was sponsored by the Defense Advanced Research Projects Agency (DARPA). The network does not have real-time data dissemination. Description, status and plans will be discussed.

  9. Pacific neogene stratigraphy

    NASA Astrophysics Data System (ADS)

    Barron, John; Beu, Alan; Blueford, Joyce R.; Chinzei, Kiyotaka; Hornibrook, Norcutt; Ingle, James; Steininger, Fritz; Tsuchi, Ryuichi

    The Fourth International Congress of Pacific Neogene Stratigraphy, was held July 29-31, 1987, at the University of California, Berkeley. This very successful congress was organized by the Regional Committee on Pacific Neogene Stratigraphy (RCPNS) of the International Union of Geological Sciences (IUGS) and the International Geological Correlation Program (IGCP) Project 246 “Pacific Neogene Events in Time and Space.” The meeting was attended by 180 scientists from 16 different countries, and more than 90 presentations were made, on topics ranging from paleoclimatology, biostratigraphy, regional stratigraphy and geologic history, new techniques in stratigraphy, evolutionary studies, and modern biofacies and sediment relationships.A. R. Edwards of the New Zealand Geological Survey (Lower Hutt, New Zealand) spoke on climatic events that he recognizes in the late Neogene strata of New Zealand. The carbon isotope shift during chron 6 (6.3-6.5 Ma) is identified in the sequence at Blind River (Marlborough, New Zealand). The extinction of ˜25% of New Zealand molluscan genera during the latest Micoene (Kapitean Stage) accompanied the greatly accelerated diversification of planktonic foraminifera lineages at this time. The New Zealand events are also coeval with the Messinian “salinity crisis” in the Mediterranean. A series of events (extinctions of Mollusca, appearance of glacial rock types, foraminifera speciation, and nannofossil appearances) in New Zealand late Pliocene rocks reflect the climatic deterioration. One type of sub-Antarctic molluscan fauna abruptly appeared in central North Island at 2.4 m.y., coeval with the onset of major Northern Hemisphere glaciation.

  10. Neogene desertification of Africa

    NASA Astrophysics Data System (ADS)

    Senut, Brigitte; Pickford, Martin; Ségalen, Loïc

    2009-08-01

    Throughout the Neogene, the faunas and floras in Africa recorded global climatic changes. We present an overview of Neogene desertification in Africa by tracing stable isotopes in eggshells and mammalian enamel, by faunal (changes in hypsodonty, etc.) and floral changes in sequences at the latitudinal extremities of the continent and the equator. This work reveals that desertification started in the southwest ca 17-16 Ma, much earlier than the region of the present-day Sahara (ca 8-7 Ma) and long before the deserts in East Africa (Plio-Pleistocene). A consequence of this history is that animals and plants inhabiting the South of the continent had a long period of time in which to adapt to arid, unstable climatic conditions. When parts of East Africa became arid during the Late Miocene and Plio-Pleistocene, several of these lineages expanded northwards and occupied developing arid niches before local lineages could adapt. Several of the latter became extinct, while others withdrew westwards as the tropical forest diminished in extent. It is proposed that the history of desertification in Africa was related to that of the polar ice caps (Antarctic, Arctic).

  11. Ostracods from the Neogene Solimões Formation (Amazonas, Brazil)

    NASA Astrophysics Data System (ADS)

    Feijó Ramos, Maria Inês

    2006-03-01

    Ostracods from an outcrop of the Solimões Formation (southwestern Amazonas state, Brazil) are studied. One new species ( Cytheridella purperae sp. nov. ) is described, and six species endemic to the Neogene of western Amazonia ( Darwinula fragilis, Cyprideis pebasae, C. graciosa, C. longispina, C. lacrimata, and Cypria aqualica) are reported, together with one unidentified species ( Cytheridella sp.). The fauna suggest a low-energy fluviolacustrine depositional setting, possibly with very low salinity. Using facies and ostracod data, the studied outcrop is compared with other Miocene deposits of western Amazonia.

  12. Neogene sutures in eastern Indonesia

    NASA Astrophysics Data System (ADS)

    Hall, R.; Wilson, M. E. J.

    2000-12-01

    Five suture zones are described from the zone of collision between the Eurasian, Indian-Australian and Pacific-Philippine Sea plates within the eastern Indonesia region. These are the Molucca, Sorong, Sulawesi, Banda and Borneo sutures. Each of these sutures has a relatively short history compared to most pre-Neogene orogenic belts, but each preserves a record of major changes in tectonics including subduction polarity reversals, elimination of volcanic arcs, changing plate boundaries, and important extension within an overall contractional setting. Rapid tectonic changes have occurred within periods of less than 5 Ma. Many of these events, although important, would be overlooked in older orogenic belts because the age resolution required to identify them, even when the evidence is preserved, is simply not possible.

  13. Southwestern Sojourn.

    ERIC Educational Resources Information Center

    Horwood, Bert

    1983-01-01

    Discusses the common characteristics of experiential education programs and administration in public and private elementary, secondary, and alternative high schools in Colorado and New Mexico. Also discusses the attributes of an effective outdoor education leader and how those attributes are acquired, based on interviews with Southwestern outdoor…

  14. Transarterial chemoembolization and bland embolization for hepatocellular carcinoma.

    PubMed

    Tsochatzis, Emmanuel A; Fatourou, Evangelia; O'Beirne, James; Meyer, Tim; Burroughs, Andrew K

    2014-03-28

    Transarterial chemoembolization (TACE) is the first line treatment for patients with intermediate stage hepatocellular carcinoma but is also increasingly being used for patients on the transplant waiting list to prevent further tumor growth. Despite its widespread use, TACE remains an unstandardized procedure, with variation in type and size of embolizing particles, type and dose of chemotherapy and interval between therapies. Existing evidence from randomized controlled trials suggest that bland transarterial embolization (TAE) has the same efficacy with TACE. In the current article, we review the use of TACE and TAE for hepatocellular carcinoma and we focus on the evidence for their use. PMID:24695579

  15. Fossil diatoms and neogene paleolimnology

    USGS Publications Warehouse

    Platt, Bradbury J.

    1988-01-01

    Diatoms have played an important role in the development of Neogene continental biostratigraphy and paleolimnology since the mid-19th Century. The history of progress in Quaternary diatom biostratigraphy has developed as a result of improved coring techniques that enable sampling sediments beneath existing lakes coupled with improved chronological control (including radiometric dating and varve enumeration), improved statistical treatment of fossil diatom assemblages (from qualitative description to influx calculations of diatom numbers or volumes), and improved ecological information about analogous living diatom associations. The last factor, diatom ecology, is the most critical in many ways, but progresses slowly. Fortunately, statistical comparison of modern diatom assemblages and insightful studies of the nutrient requirements of some common freshwater species are enabling diatom paleolimnologists to make more detailed interpretations of the Quaternary record than had been possible earlier, and progress in the field of diatom biology and ecology will continue to refine paleolimnological studies. The greater age and geologic setting of Tertiary diatomaceous deposits has prompted their study in the contexts of geologic history, biochronology and evolution. The distribution of diatoms of marine affinities in continental deposits has given geologists insights about tectonism and sea-level change, and the distribution of distinctive (extinct?) diatoms has found utilization both in making stratigraphic correlations between outcrops of diatomaceous deposits and in various types of biochronological studies that involve dating deposits in different areas. A continental diatom biochronologic scheme will rely upon evolution, such as the appearance of new genera within a family, in combination with regional environmental changes that are responsible for the wide distribution of distinctive diatom species. The increased use of the scanning electron microscope for the

  16. The Neogene: Origin, adoption, evolution, and controversy

    NASA Astrophysics Data System (ADS)

    Walsh, Stephen L.

    2008-07-01

    Some stratigraphers have recently insisted that for historical reasons, the Neogene (Miocene + Pliocene) should be extended to the present. However, despite some ambiguity in its application by Moriz Hörnes in the 1850s, the "Neogene" was widely adopted by European geologists to refer to the Miocene and Pliocene of Lyell, but excluding the "Diluvium" (later to become the Pleistocene) and "Alluvium" (later to become the Holocene). During the late 19th and early 20th centuries, the ends of the Neogene, Tertiary and Pliocene evolved in response to the progressive lowering of the beginnings of the Quaternary and Pleistocene. This evolution was a logical result of the widespread views that the most recent "ice ages" were worthy of recognition as a formal unit of the standard geologic time scale, and that the structure of this time scale must be strictly hierarchical. Motivations for the extension of the Neogene to the present include the desire to establish a monopoly for marine biochronology in the definition of standard global chronostratigraphic boundaries. This agenda would also eliminate the Tertiary, Quaternary, and Holocene. These changes are unnecessary. There is every reason to retain the traditional hierarchical structure of the Cenozoic time scale.

  17. Bland Embolization of Hepatocellular Carcinoma Using Superabsorbent Polymer Microspheres

    SciTech Connect

    Osuga, Keigo; Hori, Shinichi; Hiraishi, Kumiko; Sugiura, Takashi; Hata, Yasuhiro; Higashihara, Hiroki; Maeda, Noboru; Tomoda, Kaname; Nakamura, Hironobu

    2008-11-15

    The purpose of this study was to investigate the clinical outcomes of bland embolization using superabsorbent polymer microspheres (SAP-TAE) as an initial therapeutic option for previously untreated hepatocellular carcinoma (HCC) ineligible for resection or ablation. Fifty-nine patients with previously untreated HCC unamenable to surgery or ablation underwent bland embolization using 100- to 200-{mu}m reconstituted SAP particles (SAP-TAE) as the initial treatment. SAP-TAE was repeated as needed based on tumor response but was switched to chemoembolization when necessary to control residual or progressive tumor. Early tumor response was assessed by contrast-enhanced CT according to RECIST and EASL criteria 1 month after the initial SAP-TAE. The overall survival was calculated using the Kaplan-Meier method. The overall mean follow-up period was 30.6 months (range, 7-59 months). A total of 121 sessions of SAP-TAE were performed, with 1-5 sessions per patient (mean, 2.1 sessions). The mean period of repeated SAP-TAE was 15.6 months (range, 1-51 months), and it exceeded 1 and 2 years in 32 (54%) and 15 (25%) patients, respectively. Thirteen (22%) patients underwent repeated SAP-TAE alone, and the remaining 46 (78%) patients underwent subsequent chemoembolization. No major complication was observed and postembolization syndrome was minimal after SAP-TAE in all patients. Response rate was 14% and 66% by RECIST and EASL criteria, respectively. Overall survival rates were 100% and 83% at 1 and 2 years, respectively, and median survival time was 30 months. In conclusion, SAP-TAE was a safe and repeatable option as the induction therapy for HCC unamenable to surgery or ablation, despite the high incidence of converting to TACE during the total course.

  18. Histologically-Proven Efficacy of Bland Embolization in a Patient with Net Liver Metastasis.

    PubMed

    Monfardini, Lorenzo; Varano, Gianluca Maria; Foà, Riccardo; Della Vigna, Paolo; Bonomo, Guido; Bertani, Emilio; Guerini-Rocco, Elena; Spada, Francesca; Orsi, Franco

    2016-06-01

    We present a case of 57-year-old patient with three liver metastases from a primary neuroendocrine duodenal tumor, who underwent bland embolization with excellent response to therapy, followed by surgical resection. The purpose of our case report is to describe the histological characteristics of tumoral response to therapy after bland embolization focusing on intralesional necrosis and microsphere distribution. PMID:26714693

  19. Evolution of Neogene Dynamic Topography in Madagascar

    NASA Astrophysics Data System (ADS)

    Paul, J. D.; Roberts, G.; White, N. J.

    2012-12-01

    Madagascar is located on the fringes of the African superswell. Its position and the existence of a +30 mGal long wavelength free-air gravity anomaly suggest that its present-day topography is maintained by convective circulation of the sub-lithospheric mantle. Residual depth anomalies of oceanic crust encompassing the island imply that Madagascar straddles a dynamic topographic gradient. In June-July 2012, we examined geologic evidence for Neogene uplift around the Malagasy coastline. Uplifted coral reef deposits, fossil beach rock, and terraces demonstrate that the northern and southern coasts are probably being uplifted at a rate of ~0.2 mm/yr. Rates of uplift clearly vary around the coastline. Inland, extensive peneplains occur at elevations of 1 - 2 km. These peneplains are underlain by 10 - 20 m thick laterite deposits, and there is abundant evidence for rapid erosion (e.g. lavaka). Basaltic volcanism also occurred during Neogene times. These field observations can be combined with an analysis of drainage networks to determine the spatial and temporal pattern of convectively driven uplift. ~100 longitudinal river profiles were extracted from a digital elevation model of Madagascar. An inverse model is then used to minimize the misfit between observed and calculated river profiles as a function of uplift rate history. During inversion, the residual misfit decreases from ~20 to ~4. Our results suggest that youthful and rapid uplift of 1-2 km occurred at rates of 0.2-0.4 mm/yr during the last ˜15 Myr. The algorithm resolves distinct phases of uplift which generate localized swells of high topography and relief (e.g. the Hauts Plateaux). Our field observations and modeling indicate that the evolution of drainage networks may contain useful information about mantle convective processes.

  20. Causes of Neogene intensification of the Benguela Upwelling System

    NASA Astrophysics Data System (ADS)

    Jung, Gerlinde; Prange, Matthias; Schulz, Michael

    2014-05-01

    Coastal upwelling off the West coast of southern Africa has, according to proxy evidence, progressively intensified during the past 12 million years. Contrasting hypotheses on the cause of this long-term change during the Miocene-Pliocene epoch have been proposed. These range from increasing Antarctic glaciation and global cooling to the northward movement of the African continent, and the closing of the Central American isthmus. Geological evidence also suggests phases of major uplift in the East African Rift system as well as in South and South-West Africa during the Late Miocene and Pliocene but their potential climatic impact remains to be quantified. We performed sensitivity experiments with the Community Climate System Model Version 3 (CCSM3) to test the effect of regional uplift of East and South Africa (in combination and separately) on the atmospheric and ocean circulation. The model is run with a resolution of T85 (~1.4°) for the atmosphere and land surface and a variable resolution for the computation of ocean and sea ice down to a meridional grid spacing of 0.3° around the equator. The model results for South and East African uplift clearly indicate a strengthening of the low-level southerly Benguela jet along the southwestern African coast due to mountain uplift from half to full present-day altitude. This induces increased Ekman pumping and upwelling in the Benguela region. Consequently simulated temperature regionally decreases by up to 3.5°C in the surface ocean. The sensitivity runs show that only considering uplift of South-West Africa can not explain the entire magnitude of change, which indicates that also East African topography impacts upwelling intensity in the Benguela region. Finally we analyzed two other model experiments regarding alternative hypotheses of 1) the closure of the Panama Isthmus and 2) Antarctic glaciation. The results indicate a minor impact of these processes on the strength of Benguela upwelling. We therefore conclude

  1. How synchronous are neogene marine plankton events?

    NASA Astrophysics Data System (ADS)

    Spencer-Cervato, Cinzia; Thierstein, Hans R.; Lazarus, David B.; Beckmann, Jean-Pierre

    1994-10-01

    An electronic supplement of this material may be obtained on adiskette or Anonymous FTP from KOSMOS.AGU.ORG. (LOGIN toAGU's FTP account using ANONYMOUS as the username andGUEST as the password. Go to the right directory by typing CDAPEND. Type LS to see what files are available. Type GET and thename of the file to get it. Finally, type EXIT to leave the system.)(Paper 94PA01456, How synchronous are Neogene marine planktonevents?, by C. Spencer-Cervato, H. R. Thierstein, D. B. Lazarus, andJ-P Beckmann). Diskette may be ordered from American GeophysicalUnion, 2000 Florida Avenue, N.W., Washington, DC 20009; $15.00.Payment must accompany order.We analyzed the synchrony and diachrony of commonly used Neogene biostratigraphic events from data published in the Initial Reports of the Deep Sea Drilling Project (DSDP) and in the Proceedings of the Ocean Drilling Program (ODP). On the basis of the combined biostratigraphic and magnetostratigraphic evidence, new Neogene age models were constructed for 35 globally distributed DSDP and ODP holes. Biostratigraphic events from the four major plankton groups (calcareous nannofossils, diatoms, planktonic foraminifera, and radiolarians) were compiled from DSDP and ODP reports. After the elimination of possible sources of error such as stratigraphic hiatuses and reworking of specimens, 124 biostratigraphic events that occurred in at least four holes were analyzed in detail: for each event a biochronologic age estimate was derived by projection of the depth of the event onto the line of correlation of each hole, and from these a global mean age for each event was calculated, together with its standard deviation. Average standard deviations for event ages by fossil group are: calcareous nannofossil first appearance datums (FADs): 0.57 m.y. (21 events), calcareous nannofossil last appearance datums (LADs): 0.60 m.y. (25 events), diatom FADs: 0.57 m.y. (7 events), diatom LADs: 0.85 m.y. (14 events), planktonic foraminifera FADs: 0.88 m

  2. Active evaporite tectonics and collapse in the Eagle River valley and the southwestern flank of the White River uplift, Colorado

    USGS Publications Warehouse

    Scott, R.B.; Lidke, D.J.; Hudson, M.R.; Perry, W.J., Jr.; Bryant, Bruce; Kunk, M.J.; Budahn, J.R.; Byers, F.M., Jr.

    1999-01-01

    This field trip presents field evidence for Neogene evaporite tectonism, dissolution of evaporates, and related collapse in Eagle River valley and along the southwestern flank of the White River uplift. In the Eagle collapse center, Pennsylvanian evaporite flowed to form anticlinal diapirs, dissolved, and disrupted a lower Miocene basaltic plateau originally at elevations as high as 3.35 km by tilting, faulting, and sagging to elevations as low as about 2.1 km. Also in the Eagle collapse center, the 30 x 10-km, homoclinal Hardscrabble Mountain sank into evaporite during Triassic and Permian collapse followed by Neogene(?) tilting and collapse, based on seismic reflection data. Along the southwestern flank of the White River uplift in the northwestern part of the Carbondale collapse center, parts of the Grand Hogback monocline have collapsed northeastward toward a series of strike-elongate extrusive diapirs. The volume of evaporite removed from the Eagle and Carbondale collapse centers during the Neogene (about 2,250 km3 from an area of roughly 4,500 km2) was calculated by measuring the departure of collapsed basalts from an assumed original basalt plateau. Regional Neogene uplift and incision of the Rocky Mountains, which locally began about 8-10 Ma, probably triggered dissolution and collapse. Presently the Colorado River removes a dissolved-solids load of about 1.4 x 109 kg per year from the two collapse centers.

  3. Geochemical evolution of Cenozoic-Cretaceous magmatism and its relation to tectonic setting, southwestern Idaho, U.S.A

    NASA Technical Reports Server (NTRS)

    Norman, Marc D.; Leeman, William P.

    1989-01-01

    The relationships between Cretaceous to Neogene magmatism and the tectonic setting of southwestern and central Idaho are evaluated. An overview of the tectonics and geology of the northwestern U.S. is presented. Major element, trace element, and Sr, Pb, and Nd isotopic data for the region are used to place constraints on magma source characteristics, the manner in which the magmatic sources evolved through time, and the nature of interactions among mantle and crustal domains in response to changing tectonic environment.

  4. Pliocene reversal of late Neogene aridification.

    PubMed

    Sniderman, J M Kale; Woodhead, Jon D; Hellstrom, John; Jordan, Gregory J; Drysdale, Russell N; Tyler, Jonathan J; Porch, Nicholas

    2016-02-23

    The Pliocene epoch (5.3-2.6 Ma) represents the most recent geological interval in which global temperatures were several degrees warmer than today and is therefore considered our best analog for a future anthropogenic greenhouse world. However, our understanding of Pliocene climates is limited by poor age control on existing terrestrial climate archives, especially in the Southern Hemisphere, and by persistent disagreement between paleo-data and models concerning the magnitude of regional warming and/or wetting that occurred in response to increased greenhouse forcing. To address these problems, here we document the evolution of Southern Hemisphere hydroclimate from the latest Miocene to the middle Pliocene using radiometrically-dated fossil pollen records preserved in speleothems from semiarid southern Australia. These data reveal an abrupt onset of warm and wet climates early within the Pliocene, driving complete biome turnover. Pliocene warmth thus clearly represents a discrete interval which reversed a long-term trend of late Neogene cooling and aridification, rather than being simply the most recent period of greater-than-modern warmth within a continuously cooling trajectory. These findings demonstrate the importance of high-resolution chronologies to accompany paleoclimate data and also highlight the question of what initiated the sustained interval of Pliocene warmth. PMID:26858429

  5. 10Be dating of Neogene halite

    NASA Astrophysics Data System (ADS)

    Belmaker, Reuven; Lazar, Boaz; Beer, Jürg; Christl, Marcus; Tepelyakov, Natalya; Stein, Mordechai

    2013-12-01

    Direct radioactive dating of ancient halite formations is difficult because this mineral typically lacks conventionally datable material. We describe an attempt to date Neogene halite using the cosmogenic isotope 10Be (T1/2 = 1.39 Ma). We dated marine-derived salt deposits from the Sedom and Amora (The Hebrew forms of Sodom and Gomorrah) Formations, Dead Sea basin, Israel. To verify whether Be is incorporated into marine halite we measured the stable isotope 9Be, 7Be (the short lived “cosmogenic brother” of 10Be having T1/2 = 53.3 d), and 10Be in evaporation pans of sea-salt production plants. The data suggest that seawater beryllium is incorporated into the halite with a halite-brine distribution coefficient, (KD) of about unity. A 10Be/9Be decay curve constructed for Sedom Formation halite yielded an age that lies in the range of ∼2-6 Ma. The 10Be decay curve constructed for Sedom Formation halite yielded an age that lies in the range of 3-5 Ma. This age is consistent with previous estimates of the Sedom Formation age. Furthermore, this age lies in the same range of 10Be in situ ages obtained on the lacustrine Erq El Ahmer Formation located in the northern Jordan Valley. This may imply that during the Mid Pliocene the Sedom Lagoon, the water-body that deposited the Sedom Formation, might have been already disconnected from the open sea.

  6. Pliocene reversal of late Neogene aridification

    PubMed Central

    Sniderman, J. M. Kale; Woodhead, Jon D.; Jordan, Gregory J.; Drysdale, Russell N.; Tyler, Jonathan J.; Porch, Nicholas

    2016-01-01

    The Pliocene epoch (5.3–2.6 Ma) represents the most recent geological interval in which global temperatures were several degrees warmer than today and is therefore considered our best analog for a future anthropogenic greenhouse world. However, our understanding of Pliocene climates is limited by poor age control on existing terrestrial climate archives, especially in the Southern Hemisphere, and by persistent disagreement between paleo-data and models concerning the magnitude of regional warming and/or wetting that occurred in response to increased greenhouse forcing. To address these problems, here we document the evolution of Southern Hemisphere hydroclimate from the latest Miocene to the middle Pliocene using radiometrically-dated fossil pollen records preserved in speleothems from semiarid southern Australia. These data reveal an abrupt onset of warm and wet climates early within the Pliocene, driving complete biome turnover. Pliocene warmth thus clearly represents a discrete interval which reversed a long-term trend of late Neogene cooling and aridification, rather than being simply the most recent period of greater-than-modern warmth within a continuously cooling trajectory. These findings demonstrate the importance of high-resolution chronologies to accompany paleoclimate data and also highlight the question of what initiated the sustained interval of Pliocene warmth. PMID:26858429

  7. Including the Tukey Mean-Difference (Bland-Altman) Plot in a Statistics Course

    ERIC Educational Resources Information Center

    Kozak, Marcin; Wnuk, Agnieszka

    2014-01-01

    The Tukey mean-difference plot, also called the Bland-Altman plot, is a recognized graphical tool in the exploration of biometrical data. We show that this technique deserves a place on an introductory statistics course by encouraging students to think about the kind of graph they wish to create, rather than just creating the default graph for the…

  8. Environmental Management Audit: Southwestern Power Administration (Southwestern)

    SciTech Connect

    Not Available

    1993-03-01

    This report documents the results of the Environmental Management Audit completed for the Southwestern Power Administration. During this Audit, activities and records were reviewed and personnel interviewed. The onsite portion of the Southwestern Audit was conducted from November 30 through December 11, 1992, by the US Department of Energy's Office of Environmental Audit (EH-24). EH-24 carries out independent assessments of Department of Energy (DOE) facilities and activities as part of the Assistant Secretary's Environmental Audit Program. This program is designed to evaluate the status of DOE facilities/activities regarding compliance with laws, regulations, DOE Orders, formal written procedures, compliance agreements, and Best Management Practices (BMPs). This internal oversight function plays an important role in improving the compliance status of DOE operations. The Environmental Management Audit stresses DOE's policy that it is the responsibility of line management to conduct operations in an environmentally sound and safe manner. The Environmental Management Audit focuses on management systems and programs, whereas the Environmental Baseline Audit conducted in March 1991 focused on specific compliance issues. The scope of the Southwestern Environmental Management Audit included a review of all systems and functions necessary for effective environmental management. Specific areas of review included: Organizational Structure; Environmental Commitment; Environmental Protection Programs; Formality of Environmental Programs; Internal and External Communication; Staff Resources, Training, and Development; and Program Evaluation, Reporting, and Corrective Action.

  9. Environmental Management Audit: Southwestern Power Administration (Southwestern)

    SciTech Connect

    Not Available

    1993-03-01

    This report documents the results of the Environmental Management Audit completed for the Southwestern Power Administration. During this Audit, activities and records were reviewed and personnel interviewed. The onsite portion of the Southwestern Audit was conducted from November 30 through December 11, 1992, by the US Department of Energy`s Office of Environmental Audit (EH-24). EH-24 carries out independent assessments of Department of Energy (DOE) facilities and activities as part of the Assistant Secretary`s Environmental Audit Program. This program is designed to evaluate the status of DOE facilities/activities regarding compliance with laws, regulations, DOE Orders, formal written procedures, compliance agreements, and Best Management Practices (BMPs). This internal oversight function plays an important role in improving the compliance status of DOE operations. The Environmental Management Audit stresses DOE`s policy that it is the responsibility of line management to conduct operations in an environmentally sound and safe manner. The Environmental Management Audit focuses on management systems and programs, whereas the Environmental Baseline Audit conducted in March 1991 focused on specific compliance issues. The scope of the Southwestern Environmental Management Audit included a review of all systems and functions necessary for effective environmental management. Specific areas of review included: Organizational Structure; Environmental Commitment; Environmental Protection Programs; Formality of Environmental Programs; Internal and External Communication; Staff Resources, Training, and Development; and Program Evaluation, Reporting, and Corrective Action.

  10. Mapping potential Blanding's turtle habitat using aerial orthophotographic imagery and object based classification

    NASA Astrophysics Data System (ADS)

    Barker, Rebecca

    Blanding's turtle (Emydoidea blandingii) is a threatened species in southern Quebec that is being inventoried to determine abundance and potential habitat by the Quebec Ministry of Natural Resources and Wildlife. In collaboration with that program and using spring leaf-off aerial orthophotos of Gatineau Park, attributes associated with known habitat criteria were analyzed: wetlands with open water, vegetation mounds for camouflage and thermoregulation, and logs for spring sun-basking. Pixel-based classification to separate wetlands from other land cover types was followed by object-based segmentation and rule-based classification of within--wetland vegetation and logs. Classifications integrated several image characteristics including texture, context, shape, area and spectral attributes. Field data and visual interpretation showed the accuracies of wetland and within wetland habitat feature classifications to be over 82.5%. The wetland classification results were used to develop a ranked potential habitat suitability map for Blanding's turtle that can be employed in conservation planning and management.

  11. Processing and interpretation of seismic reflection data near the Bane Dome in Bland County, Virginia

    SciTech Connect

    Domoracki, W.J.; Costain, J.K.; Coruh, C. . Dept. of Geological Sciences)

    1989-11-01

    The purpose if this study was to process and interpret a seismic reflection line from Bland County, Virginia, and to compare it to an earlier line in this location. A longer Vibroseis sweep with greater bandwidth was used for the new line, which provided a considerable improvement in signal to noise ratio and resulted in better residual statics. Additional processing steps, including crooked line CDP sort and predictive deconvolution, also led to improved resolution, particularly in the shallow section. The geologic section interpreted from the seismic profile represents a series of fault slices between the St. Clair Narrows thrust plates above autochthonous Lower Cambrian shelf strata. A previously interpreted Eocambrian rift basin is clearly defined on this line; the basin is bounded by a large normal fault at its north end. Seismicity in Bland and Giles counties may originate in reactivated Eocambrian faults which presumably formed during opening of the Proto-Atlantic Ocean. 23 refs., 13 figs.

  12. Neogene Extension and Exhumation in NW Sulawesi

    NASA Astrophysics Data System (ADS)

    Advokaat, E. L.; Hall, R.; White, L. T.; Armstrong, R. A.; Kohn, B. P.; BouDagher-Fadel, M. K.

    2014-12-01

    The unusual K-shaped island of Sulawesi, located in the convergent zone between the Eurasian, Australian and Pacific plates, has traditionally been interpreted as the consequence of collision and accretion. New data challenge this idea and indicate that crustal extension has played an important role in its Neogene development. In the north of the Sulawesi North Arm are Eocene-Lower Miocene basalts intercalated with radiolarian chert and volcaniclastic sediments, which were deformed during collision of the Sula Spur with the North Arm. Undeformed granitoids derived from lower crustal rocks intrude the sequence and preliminary LA-ICP-MS U-Pb zircon ages decrease from 9.44±0.43 Ma in the north to 8.19±0.20 Ma in the south. Structurally beneath all these rocks is the Malino Metamorphic Complex (MMC) which exposes dominantly quartzo-feldspathic muscovite schists to gneisses, with subordinate amphibolites and garnet schists. The MMC is a metamorphic core complex, surrounded by a discontinuous greenschist carapace and shear zones with opposite shear senses on the northern and southern sides of the complex. Metamorphic rocks from the MMC yield SHRIMP U-Pb ages on zircon rims of 15.42±0.62 Ma and 15.36±0.53 Ma. Locally these metamorphic rocks are intruded by undeformed granitoids with SHRIMP U-Pb zircon ages of 4.85 ± 0.07 to 3.78±0.04 Ma. Late stage exhumation accommodated by high angle oblique normal faults is indicated by apatite (U-Th)/He ages between 3.26±0.23 Ma and 1.43±0.24 Ma, at a rate of 0.27 mm/a based on age-elevation plots. Lower Pliocene-Lower Pleistocene syn-extensional shallow marine siliciclastic and carbonate sediments are crosscut by normal faults. The timing of faulting and lack of metamorphic detritus in these young sediments support rapid and recent regional uplift. We interpret two phases of extension in North Sulawesi, one during the Middle Miocene and another during the Late Pliocene-Pleistocene, exhuming the granitic and metamorphic rocks.

  13. The Bland-Altman Method Should Not Be Used in Regression Cross-Validation Studies

    ERIC Educational Resources Information Center

    O'Connor, Daniel P.; Mahar, Matthew T.; Laughlin, Mitzi S.; Jackson, Andrew S.

    2011-01-01

    The purpose of this study was to demonstrate the bias in the Bland-Altman (BA) limits of agreement method when it is used to validate regression models. Data from 1,158 men were used to develop three regression equations to estimate maximum oxygen uptake (R[superscript 2] = 0.40, 0.61, and 0.82, respectively). The equations were evaluated in a…

  14. Bland diet

    MedlinePlus

    ... gassy, such as broccoli, cabbage, cauliflower, cucumber, green peppers, and corn Fresh berries and other fresh fruits ... sauerkraut, and similar foods Spices, such as hot pepper and garlic Foods with a lot of sugar ...

  15. Bland diet

    MedlinePlus

    ... gassy, such as broccoli, cabbage, cauliflower, cucumber, green peppers, and corn Seedy fruits such as berries or ... sauerkraut, and similar foods Spices, such as hot pepper and garlic Foods with a lot of sugar ...

  16. Paleogene and Neogene reference sections of Eastern Kamchatka

    NASA Astrophysics Data System (ADS)

    Gladenkov, Yu. B.

    2016-01-01

    The available lithological and paleontological data are used to characterize key Cenozoic marine sections in two lithological-facies zones (Kamchatskii Mys Peninsula and southern Valaginskii Range) of the poorly investigated Eastern Kamchatka lithotectonic zone with their correlation and reconstruction of depositional environments at the ocean-continent transition during the Paleogene and Neogene.

  17. Neogene Extension of the Central North Arm of Sulawesi, Indonesia

    NASA Astrophysics Data System (ADS)

    Rudyawan, A.; Hall, R.; White, L. T.

    2014-12-01

    The peculiar K-shape of Sulawesi has been the subject of geological interest for many years. The east-west trend of the North Arm is commonly considered to have formed by crustal shortening of an intra-oceanic arc built on Eocene ocean crust. However, recent onshore and offshore geological studies suggest an important role for Neogene extension. Field mapping and dating of the pre-Neogene basement indicates that Sulawesi's North Arm constitutes more than a simple oceanic arc. Paleogene granites in this region suggest the basement includes either evolved arc crust or continental crust. LA-ICP-MS U-Pb dating of zircons shows that Paleogene granites have few inherited ages whereas Neogene granites contain Palaeozoic and Proterozoic inherited zircon cores, suggesting melting of Australian continental crust. Biostratigraphic dating of Neogene shallow marine sedimentary rocks on land indicates two distinct periods of sedimentation: Middle Miocene and Late Miocene-Pliocene. Field observations and remote sensing interpretation identify two major fault trends: E-W Neogene basin-bounding faults and young NW-SE strike-slip faults. Offshore seismic surveys show several major sequences separated by regional unconformities in Gorontalo Bay, south of the North Arm, where there was deposition of more than 6 km of sediments. We correlate the thickest package south of the central North Arm, up to 5 sec TWT, with thick marine reworked volcanic ash deposits of Pliocene age mapped on land in the North Arm, on the Togian Islands in Gorontalo Bay, and in the East Arm of Sulawesi. We interpret the land and offshore record to indicate arc-continent collision and underthrusting of Australian crust in the Early Miocene (c.22 Ma). There were several subsequent episodes of extension. A metamorphic core complex formed on land in the Middle Miocene (c.15 Ma), and later renewed extension was linked to initiation of southward subduction of the Celebes Sea in the Late Miocene-Early Pliocene (c.5 Ma).

  18. Neogene molluscan stages of the West Coast of North America

    USGS Publications Warehouse

    Marincovich, L., Jr.

    1984-01-01

    Neogene marine sediments of the West Coast of North America were deposited in a series of widely spaced basins that extended geographically from the western and northern Gulf of Alaska (60??N) to southern California (33??N). Rich molluscan faunas occur extensively throughout these deposits and form the basis for biostratigraphic schemes that are useful for correlating within and between individual basins. Early biostratigraphic work was concerned with faunas from particular horizons and with the stratigraphic range of diverse taxa, such as Pecten and Turritella, without reference to other fossil groups. Succeeding work increasingly dealt with the relationships of molluscan zones to benthic and, later, planktonic foraminiferal stages. In recent years the age limits of Neogene molluscan stages have become better documented by reference to planktonic microfossils from dated DSDP cores and onshore faunas. Neogene molluscan faunas from California, the Pacific Northwest states (Oregon and Washington), and southern Alaska have been treated separately due to differences in faunal composition and geographic isolation. As a result, a different biostratigraphic sequence has been described for each region. Pacific Northwest stages have been formally named and defined, and their names are also used informally for Alaskan faunas. California Neogene stages were proposed early in this century, are in need of redescription, and their usage is informal. Precise correlations between the three regional sequences have not yet been achieved, due to the low number of co-occurring species and the general lack of planktonic microfossils in these largely shallow-water faunas. The objectives of ongoing research include: fuller documentation of the faunas of California and Pacific Northwest stages; formal description of California stages; improved correlation between regional stage sequences; refinement of age estimates for stage boundaries; and, establishment of Neogene stages for Alaskan

  19. Coulomb excitation of exotic nuclei at the R3B-LAND setup

    NASA Astrophysics Data System (ADS)

    Rossi, D. M.; Adrich, P.; Aksouh, F.; Alvarez-Pol, H.; Aumann, T.; Benlliure, J.; Böhmer, M.; Boretzky, K.; Casarejos, E.; Chartier, M.; Chatillon, A.; Cortina-Gil, D.; Datta Pramanik, U.; Emling, H.; Ershova, O.; Fernandez-Dominguez, B.; Geissel, H.; Gorska, M.; Heil, M.; Johansson, H.; Junghans, A.; Kiselev, O.; Klimkiewicz, A.; Kratz, J. V.; Kurz, N.; Labiche, M.; Le Bleis, T.; Lemmon, R.; Litvinov, Yu A.; Mahata, K.; Maierbeck, P.; Movsesyan, A.; Nilsson, T.; Nociforo, C.; Palit, R.; Paschalis, S.; Plag, R.; Reifarth, R.; Simon, H.; Sümmerer, K.; Wagner, A.; Walus, W.; Weick, H.; Winkler, M.

    2013-03-01

    Exotic Ni isotopes have been measured at the R3B-LAND setup at GSI in Darmstadt, using Coulomb excitation in inverse kinematics at beam energies around 500 MeV/u. As the experimental setup allows kinematically complete measurements, the excitation energy was reconstructed using the invariant mass method. The GDR and additional low-lying strength have been observed in 68Ni, the latter exhausting 4.1(1.9)% of the E1 energy-weighted sum rule. Also, the branching ratio for the non-statistical decay of the excited 68Ni nuclei was measured and amounts to 24(4)%.

  20. Prospective Randomized Comparison of Chemoembolization with Doxorubicin-Eluting Beads and Bland Embolization with BeadBlock for Hepatocellular Carcinoma

    SciTech Connect

    Malagari, Katerina; Pomoni, Mary; Kelekis, Alexis; Pomoni, Anastasia; Dourakis, Spyros; Spyridopoulos, Themis; Moschouris, Hippokratis; Emmanouil, Emmanouil; Rizos, Spyros; Kelekis, Dimitrios

    2010-06-15

    The purpose of this study was to evaluate the added role of a chemotherapeutic in transarterial chemoembolization (TACE) of intermediate-stage hepatocellular carcinoma (HCC). The issue is of major importance since, as suggested by recent evidence, hypoxia or incomplete devascularization of the tumor is a potent stimulator of angiogenesis, and there are not many papers supplying level one evidence confirming the value of a chemotherapeutic. The hypothesis was that since drug-eluting bead (DEB)-TACE is standardized and reproducible, a comparison with bland TACE can readily reveal the potential value of the chemotherapeutic. Two groups were randomized in this prospective study: group A (n = 41) was treated with doxorubicin DEB-TACE, and group B (n = 43) with bland embolization. Patients were randomized for tumor diameter. Patients were embolized at set time intervals (2 months), with a maximum of three embolizations. Tumor response was evaluated using the EASL criteria and {alpha}-fetoprotein levels. At 6 months a complete response was seen in 11 patients (26.8%) in the DEB-TACE group and in 6 patients (14%) in the bland embolization group; a partial response was achieved in 19 patients (46.3%) and 18 (41.9%) patients in the DEB-TACE and bland embolization groups, respectively. Recurrences at 9 and 12 months were higher for bland embolization (78.3% vs. 45.7%) at 12 months. Time to progression (TTP) was longer for the DEB-TACE group (42.4 {+-} 9.5 and 36.2 {+-} 9.0 weeks), at a statistically significant level (p = 0.008). In conclusion, DEB-TACE presents a better local response, fewer recurrences, and a longer TTP than bland embolization with BeadBlock. However, survival benefit and bland embolization with smaller particles must be addressed in future papers to better assess the clinical value.

  1. Marine intervals in Neogene fluvial deposits of western Amazonia

    NASA Astrophysics Data System (ADS)

    Boonstra, Melanie; Troelstra, Simon; Lammertsma, Emmy; Hoorn, Carina

    2014-05-01

    Amazonia is one of the most species rich areas on Earth, but this high diversity is not homogeneous over the entire region. Highest mammal and tree-alpha diversity is found in the fluvio-lacustrine Pebas system, a Neogene wetland associated with rapid radiation of species. The estuarine to marine origin of various modern Amazonian fish, plants, and invertebrates has been associated with past marine ingressions into this freshwater Pebas system. The exact nature and age of these invasions is, however, debated. Here we present new evidence from fluvial and fluvio-lacustrine deposits of Neogene age in southeast Colombia, that point to periods of widespread marine conditions in western Amazonia. Our evidence is based on an analysis of marine palynomorphs, such as organic linings of foraminifera and dinoflagellate cysts, present in dark sandy clay sediments that outcrop along the Caqueta and Amazon rivers. Characteristically, the foraminiferal linings can be assigned to three benthic morphotypes only, e.g. Ammonia, Elphidium and Trochammina. This low diversity assemblage is associated with estuarine/marginal marine conditions. No distinct marine elements such as shelf or planktonic species were encountered. The observed foraminiferal linings and dinocyst assemblages are typical for a (eutrophic) shallow marine environment, suggesting that the Pebas freshwater wetland system occasionally changed to (marginal) marine. Although some reworked elements are found, a typical Neogene dinocyst taxon is commonly found supporting in situ deposition. Sedimentological features typical for tidal conditions that are reported for sites in Peru and northeastern Brazil likely relate to these marine ingressions. Sea level changes as well as foreland basin development related to Andes formation may have facilitated the entry of marine water during the Neogene.

  2. A Bivalve Proxy for Neogene Antarctic Shelf Marine Environments

    NASA Astrophysics Data System (ADS)

    Clark, N. A.; Williams, M.; Quilty, P. G.; Leng, M. J.; Zalasiewicz, J. A.; Smellie, J.; Dowsett, H. J.

    2012-12-01

    The Neogene shallow-marine successions of the Antarctic Peninsula and of the East Antarctic region preserve rich assemblages of bivalve molluscs. These bivalve molluscs provide a detailed record of palaeoseasonality in the chemical signature and morphology of their shells that can be used to assess sea temperatures and sea ice extent for the Antarctic shelf during the Pliocene. Analyses identify the following. 1) Neogene bivalves from James Ross Island, Antarctic Peninsula, comprise material of late Miocene through to late Pliocene age. Results identify warm (ca. 3-10 °C) early Pliocene sea temperatures, and cooler late Pliocene sea temperatures (ca. 0-4 °C), and flag a cooling trend which is consistent with the evolution of polar climate through this interval. 2) Neogene bivalves from the Larsemann Hills, East Antarctic, identify generally warmer than present sea temperatures (ca. 0-11 °C) in the early Pliocene consistent with data from other fossil groups of this age, including dolphins and silicoflagellates. The new data may provide significant ground truth for climate models assessing the Southern Ocean and Antarctic shelf climate.

  3. Relating annual increments of the endangered Blanding's turtle plastron growth to climate.

    PubMed

    Richard, Monik G; Laroque, Colin P; Herman, Thomas B

    2014-05-01

    This research is the first published study to report a relationship between climate variables and plastron growth increments of turtles, in this case the endangered Nova Scotia Blanding's turtle (Emydoidea blandingii). We used techniques and software common to the discipline of dendrochronology to successfully cross-date our growth increment data series, to detrend and average our series of 80 immature Blanding's turtles into one common chronology, and to seek correlations between the chronology and environmental temperature and precipitation variables. Our cross-dated chronology had a series intercorrelation of 0.441 (above 99% confidence interval), an average mean sensitivity of 0.293, and an average unfiltered autocorrelation of 0.377. Our master chronology represented increments from 1975 to 2007 (33 years), with index values ranging from a low of 0.688 in 2006 to a high of 1.303 in 1977. Univariate climate response function analysis on mean monthly air temperature and precipitation values revealed a positive correlation with the previous year's May temperature and current year's August temperature; a negative correlation with the previous year's October temperature; and no significant correlation with precipitation. These techniques for determining growth increment response to environmental variables should be applicable to other turtle species and merit further exploration. PMID:24963390

  4. Relating annual increments of the endangered Blanding's turtle plastron growth to climate

    PubMed Central

    Richard, Monik G; Laroque, Colin P; Herman, Thomas B

    2014-01-01

    This research is the first published study to report a relationship between climate variables and plastron growth increments of turtles, in this case the endangered Nova Scotia Blanding's turtle (Emydoidea blandingii). We used techniques and software common to the discipline of dendrochronology to successfully cross-date our growth increment data series, to detrend and average our series of 80 immature Blanding's turtles into one common chronology, and to seek correlations between the chronology and environmental temperature and precipitation variables. Our cross-dated chronology had a series intercorrelation of 0.441 (above 99% confidence interval), an average mean sensitivity of 0.293, and an average unfiltered autocorrelation of 0.377. Our master chronology represented increments from 1975 to 2007 (33 years), with index values ranging from a low of 0.688 in 2006 to a high of 1.303 in 1977. Univariate climate response function analysis on mean monthly air temperature and precipitation values revealed a positive correlation with the previous year's May temperature and current year's August temperature; a negative correlation with the previous year's October temperature; and no significant correlation with precipitation. These techniques for determining growth increment response to environmental variables should be applicable to other turtle species and merit further exploration. PMID:24963390

  5. Reconstructing Vegetation and Hydrological Changes from Biomarkers in Modern Soils and Late Neogene Paleosols, Meade Basin, KS, USA

    NASA Astrophysics Data System (ADS)

    Fischer-Femal, B.; Uno, K. T.; Polissar, P. J.; Fox-Dobbs, K.; Feinberg, J. M.; Fox, D. L.; Snell, K. E.; Martin, R.

    2014-12-01

    Paleoclimate and paleovegetation proxies can help us understand how C4 grasslands have expanded worldwide and responded to climate change during the late Neogene. The Miocene-Holocene deposits of the Meade Basin, southwestern Kansas preserve a record of C4 ecosystem expansion as well as a rich fossil record of small mammals. These records combined provide an excellent opportunity to study the cause(s) of the C4 ecosystem expansion and the consequences for faunal evolution. As part of an interdisciplinary project, we are investigating the organic geochemical record of vegetation and hydrological change in the Meade Basin. Preliminary findings from three modern soil pits suggest n-alkane δ¹³C values have similar trends to n-alkanoic acid δ¹³C values in each soil profile, but the absolute values of these two different types of plant-wax compounds are offset by up to 6.8‰. This result was unexpected because the absolute δ¹³C values of n-alkanes and n-alkanoic acids are assumed to be very similar in the plants themselves. Moreover, the δ¹³C values of the n-alkanoic acids more accurately reflect the modern vegetation at our sites. Few studies compare carbon isotope data in n-alkanes and n-alkanoic acids and it is important to constrain how these two types of plant-wax compounds reflect vegetation differently. We will use hydrogen isotope measurements on these same plant-wax samples to evaluate how the modern precipitation isotopic ratios are recorded in biomarkers, which in turn will be used to interpret hydrogen isotope data from paleosol biomarkers. Ongoing work will use plant-wax isotopic records from the modern soil profiles as a framework for interpreting the plant-wax isotopic records from Meade Basin paleosol and fluvial sediments to reconstruct the late Neogene C4 grassland expansion and hydroclimate change in this region.

  6. Southwestern Blotting Assay

    PubMed Central

    Jia, Yinshan; Nagore, Linda; Jarrett, Harry

    2016-01-01

    Southwestern blotting is a technique used to study DNA-protein interactions. This method detects specific DNA-binding proteins by incubating radiolabeled DNA with a gel blot, washing, and visualizing through autoradiography. A blot resulting from 1-dimensional SDS-PAGE reveals the molecular weight of the binding proteins. To increase separation and determine isoelectric point a 2-dimensional gel can be blotted. Additional dimensions of electrophoresis, such as a gel shift (EMSA), can precede isoelectric focusing and SDS-PAGE to further improve separation. Combined with other techniques, such as mass spectrometry, the DNA-binding protein can be identified. PMID:26404144

  7. Survey and monitoring of species at risk at Camp Blanding Training Site, northeastern Florida

    USGS Publications Warehouse

    Gregory, C.J.; Carthy, R.R.; Pearlstine, L.G.

    2006-01-01

    We studied the presence and distribution of 19 species at risk in northeastern Florida at the Camp Blanding Training Site (CBTS) during 2000-2001, seven years after the first major baseline surveys of CBTS were conducted. Much of the training conducted at CBTS deals with light infantry exercises, but the site is also used for mining, silviculture, hunting, fishing, emergency logistical support, and entertainment purposes. CBTS contains more than 2000 species of plants and animals in 14 natural communities, each impacted to various degrees by past and current land management. Adaptive management plans for species may be ineffective without continual feedback and the flexibility for change. Here we summarize and discuss the results of our surveys, compare these results with those of past surveys, identify differences between the surveys, and discuss the importance of systematic protocols and study design for CBTS environmental managers.

  8. Moving on from bland: the evolution of the law and minimally conscious patients.

    PubMed

    Heywood, Rob

    2014-01-01

    The decision in Bland centred on the withdrawal of artificial nutrition and hydration from a patient in a persistent vegetative state (PVS). Since then, a new medical condition has emerged, known as a minimally conscious state (MCS). In W v M, the Court of Protection was asked to authorise the withdrawal of artificial nutrition and hydration from a patient in a MCS. Baker J refused to grant the declaration. More recently, however, the courts were also asked to rule on the lawfulness of withholding treatment in a similar, albeit factually different, case. In the Court of Appeal decision in Aintree University Hospitals NHS Foundation Trust v David James and Others, Sir Alan Ward, with the agreement of Arden LJ and Laws LJ, granted a declaration that it would be lawful to withhold treatment. The Supreme Court then upheld this ruling, Lady Hale stating that the Court of Appeal reached the right result but for the wrong reasons. This article seeks to critically appraise the evolution of the law in regard to withdrawing treatment from MCS patients. The piece begins by explaining the differences between the two conditions of PVS and MCS and defines the law from the starting point of Bland. From here, the discussion progresses to focus on the challenges that the law has had to face in trying to keep pace with the advancing nature of medical understanding of conditions of the brain and explains how it has responded to these. The narrative then critiques the legal mechanism of best interests as it has been employed in the case law concerning MCS patients to date by analysing the various judicial perspectives on the concept. After addressing both the narrow and wide viewpoints, a conclusion is ventured as to how the balancing of best interests should be approached in respect of future MCS cases. PMID:24618294

  9. Biomarkers Reveal Late Neogene Changes in East African Vegetation

    NASA Astrophysics Data System (ADS)

    Ingram, S. J.; Demenocal, P. B.; Eglinton, T. I.

    2004-12-01

    Multiple paleoenvironmental records incorporating diverse proxies and sites are needed to build a complete picture of African environments during the late Neogene period of hominid evolution. Augmenting the picture of progressive aridification of Neogene environments indicated by the progressive enrichment of soil carbonates (Cerling and Hay, 1988; Cerling, 1992; Wynn, 2000), Hominid environment-evolution hypotheses have drawn on evidence for high frequency environmental variability to emphasize the potential importance of climate variability as an evolutionary selection factor (Potts, 1996). Dramatic evidence for Neogene climatic variability is seen in high benthic foraminiferal oxygen isotope records of high latitude climate (Shackleton, 1990, Mix et al., 1995). This `global' signal has also been detected in low latitudes as shown by orbital frequency climate variability in dust records from marine cores around the African continent (deMenocal, 1995). Terrestrial records may provide a more direct record of local habitat change than distal dust deposits, but are unable to resolve with continuity the orbital frequency climatic variability seen in marine records. We therefore turn to molecule-specific carbon isotopic analyses of plant biomarkers in marine sediments to indicate regionally integrative C3-C4 vegetation changes. The validity of this approach has already been demonstrated in marine cores off West Africa (Schefuss et al, 2003). In order to bridge the gap between large scale climatic conditions and local rift valley conditions, we select a marine core in close proximity to hominid sites in the East African rift valley to generate a high resolution, regional integrative record of vegetation change during the Neogene. We take the approach of high resolution (3ka) sampling, capable of resolving precessional variability, in `windows' downcore to provide a measure of the mean and variability of vegetation for timesclices during the last 10Ma. Our results show

  10. Giant evaporite belts of the Neogene central Andes

    NASA Astrophysics Data System (ADS)

    Alonso, Ricardo N.; Jordan, Teresa E.; Tabbutt, Kenneth T.; Vandervoort, Dirk S.

    1991-04-01

    Large volumes of continental evaporites accumulated within the central Andes during Neogene uplift of the Altiplano-Puna plateau and development of the Andean volcanic arc. Halite and gypsum are dominant minerals, along with local and economically important borates. Playa conditions have existed since ca. 15 Ma; halite and borate deposition has occurred for the past 7 to 8 m.y. Evaporites formed in salar environments (e.g., playa lakes) and are characterized by complex mineral assemblages, occurrence, zonation, and geochemistry. Evaporite deposition was controlled by volcanism, geothermal activity, closed drainage, and climate. These Andean deposits, and their controls, differ from evaporites in other continental and marine environments.

  11. Seismic fabric and 3-D structure of the southwestern intracontinental Palmyride fold belt, Syria

    SciTech Connect

    Chaimov, T.A.; Barazangi, M. ); Al-Saad, D.; Sawaf, T.; Khaddour, M. )

    1993-12-01

    The Palmyride fold belt, a 400 x 100 km transpressive belt in central Syria that is the northeastern arm of the Syrian arc, is the result of late Mesozoic and Cenozoic inversion of a late Paleozoic and Mesozoic, northeast-trending, linear intracontinental basin located within the northern Arabian platform. The southwestern Palmyrides, near the Dead Sea transform fault system and the Anti-Lebanon mountains, are characterized by short wavelength (5--10 km) en echelon folds separated by small intermontane basins that developed mainly in the Neogene to Holocene. A new three-dimensional data cube, 60 x 70 x 10 km, generated on a Landmark Graphics workstation and based on approximately 700 km of two-dimensional seismic reflection profiles, elucidates the structure of the upper 10 km of the crust in the southwestern Palmyrides. Visualization of the subsurface structure, which is represented by a prominent Upper Cretaceous reflection surface in the data cube, is augmented by topographical and Bouguer gravity data of the same region. Preexisting discontinuities, probable normal fault relicts of the Mesozoic Palmyride rift, likely controlled the development of individual Neogene thrusts. The new subsurface image shows important structural features not identified in outcrop. Short, west-northwest-trending transcurrent (or transfer) faults like the short, en echelon northeast-trending thrust faults and blind thrusts of the Palmyrides. A pervasive regional decollment is not observed, even though Triassic evaporites host local detachments. Unlike topographic relief, which only roughly resembles subsurface structures, the Bouguer gravity signature of the southwestern Palmyrides closely mimics underlying shallow geologic structures both on a large ([approximately]50 km wavelength) and a small ([approximately]5--10 km wavelength) scale. The structural analysis and many other recent studies of the region indicate minor right-lateral shear coupled with compression in the Palmyrides.

  12. Neogene paleoenvironments and tectonics of the Hongchun Peninsula, southern Taiwan

    SciTech Connect

    Chang, S. . Taiwan Petroleum Exploration Div.); Vondra, C.F. . Geological Atmospheric Sciences)

    1993-03-01

    Recent investigations in the Hongchun Peninsula in southern Taiwan provide new evidence concerning the paleoenvironmental and tectonic interpretation of the structurally complex Neogene sediments exposed there. The deposits of the peninsula have been divided into four distinct fault-bounded sequences each displaying a different lithology and style of structural development. The Mutanchi formation consists of feldspathic quartz arenites derived from a granitic provenance to the north that were deposited in a forearc basin. The lower part of the Mutanchi is dominated by thick proximal turbidities and interbedded highly contorted shales of submarine fan origin. These grade upward into shallow marine feldpathic quartz arenites and shales. The Shiman Formation consists of tuffaceous lithic arenites (proximal turbidities) and diamicites (debris flow deposits) with gravel-sized metamorphic and volcanic clasts in the lower part and interbedded lithic arenites and shales in the upper part. Although of contrasting lithology to the Mutanchi, the lower part of the Shiman Formation was also deposited on a submarine fan in a forearc tectonic setting while the upper part was deposited on a shallow marine shelf. The Kentin Formation is composed entirely of thick light green mudstones with contorted slump structures. Locally it contains very large exotic blocks (olistoliths) of variable lithology and is interpreted to be a melange -- the Kentin Melange. The above four fault-bounded units represent a forearc basin-accretionary wedge complex that developed during the late Neogene as a result of convergent interaction between the South China and Philippine plates.

  13. Strontium isotope geochronology of selected intervals within the Florida Neogene

    SciTech Connect

    Jones, D.S.; Mueller, P.A.; Hodell, D.A.; Stanley, L.A. . Dept. of Geology)

    1993-03-01

    The Neogene stratigraphic record of Florida reveals many richly fossiliferous (both invertebrate and vertebrate), shallow-marine deposits whose ages are poorly constrained, despite over a century of paleontological investigation. Chronostratigraphic analyses are frequently hampered by a general absence of age-diagnostic fossils (micro- or nannofossils in particular), laterally discontinuous sedimentary units, and an overall lack of natural exposure. Consequently, temporal correlations among many of Florida's Neogene units as well as with the global geomagnetic polarity timescale (GPTS) remain tenuous. Strontium isotope ([sup 87]Sr/[sup 86]Sr) geochronology offers considerable potential as an independent method for correlating these deposits with one another as well as with the GPTS. Portions of the Miocene and Pliocene as well as most of the Pleistocene were characterized by rapid increases in the global [sup 87]Sr/[sup 86]Sr of seawater. Marine carbonates formed within these intervals are therefore particularly amenable to investigation by Sr isotope techniques. Ratios ([sup 87]Sr/[sup 86]Sr) from mollusk shells collected throughout Florida within stratigraphic context ranged from 0.70785 which roughly correspond to the interval 30 Ma (late Oligocene) to 1 Ma (late Pleistocene). The data suggest that many accepted correlations based on lithologic and/or faunal similarities within Florida's Miocene and Plio-Pleistocene strata are improbable. While additional sampling is in order, improved correlation between vertebrate and invertebrate biochronologies has already resulted from the stratigraphic based upon this approach.

  14. Neogene Topography And Precipitation Patterns Of The Central Anatolian Plateau

    NASA Astrophysics Data System (ADS)

    Mulch, A.; Mikes, T.; Schemmel, F.; Rojay, B.

    2010-12-01

    Long-term stable isotope records of terrestrial environments represent increasingly important tools for tectonic, paleoaltimetric, and paleoclimatic reconstructions within continental interiors. A rapidly growing number of studies within the Earth’s major mountain ranges demonstrates that the growth of topography and orogenic plateaus profoundly influences local, regional, and hemispheric climate and hence precipitation patterns while regional surface uplift patterns are intimately linked to plate-scale geodynamic processes. In contrast, such records are almost absent for the Near East and the Turkish-Iranian plateau, an important topographic element in the Alpine-Himalayan chain and an area most likely to be strongly affected by future climate change and water scarcity. Our objective is to assess the role of orographic factors that have governed the distribution (and isotopic composition) of precipitation across the central Anatolian plateau (CAP, Turkey) from the Neogene to recent. Such data are fundamental for our understanding of the geodynamic and sedimentary history of orogenic plateaus in general and for the role of surface uplift along the plateau margins in the Pontide and Tauride mountains. We present oxygen, carbon, and hydrogen isotope data from Neogene-to-recent fluvio-lacustrine and pedogenic environments, stream and lake waters of the CAP with the ultimate aim of reconstructing past precipitation changes, plateau aridification and ideally Neogene surface uplift histories. Our approach is to cross-calibrate modern patterns of isotopes (oxygen and hydrogen) in precipitation with pedogenic carbonate oxygen and carbon isotope data across topographic barriers that today strongly control the distribution of rainfall along the plateau margins and within the plateau interior. We then compare these patterns with Miocene-to-Pleistocene lacustrine and pedogenic records to assess a) the role of late Neogene (ca. 8-0 Ma) surface uplift in the Taurus mountains

  15. Desert Voices: Southwestern Children's Literature.

    ERIC Educational Resources Information Center

    Polette, Keith

    1997-01-01

    Examines three books with different ways of writing about the desert. Discusses: "Here Is the Southwestern Desert" by Madeline Dunphy, "The Desert Is My Mother" by Pat Mora, and "The Desert Mermaid" by Alberto Blanco. (PA)

  16. Aneurysm of the Left Coronary Artery in Postoperative Bland-White-Garland Syndrome

    PubMed Central

    Bravo-Valenzuela, Nathalie Jeanne Magioli; Silva, Guilherme Ricardo Nunes

    2015-01-01

    We report a case of anomalous left coronary artery from the pulmonary artery (ALCAPA) or Bland-White-Garland syndrome, present the challenges of performing a differential diagnosis, and discuss the treatment of the syndrome. Although ALCAPA is a rare congenital heart disease, it is one of the most common causes of myocardial ischemia in childhood and presents a diagnostic challenge. A four-year-old girl was referred to a pediatric cardiologist for evaluation of mitral valve regurgitation murmur and heart failure. The transthoracic echocardiogram demonstrated the left coronary artery (LCA) not arising from the aorta, presence of coronary collateral circulation, and moderate mitral valve regurgitation. ALCAPA was confirmed using angiotomography. The LCA was surgically reimplanted into the aorta. After 3 years of postoperative follow-up, the patient developed an LCA aneurysm. Diagnosis of cardiac ischemia in childhood remains a challenge, and careful evaluation of coronary arteries on the echocardiogram is an important tool. In this report, we present a case of ALCAPA with an uncommon postoperative outcome. PMID:26770839

  17. Domal structure in Devonian rocks of Kimberling basin, Bland County, Virginia

    SciTech Connect

    McDowell, R.C.

    1988-08-01

    The Kimberling basin, which is floored with Middle Devonian clastic rocks, is a topographic and structural low in the Narrows fault block of the southern Appalachian Valley and Ridge province in Bland County, Virginia. The basin is bounded on the northwest and southeast by the southeast-dipping Narrows and Saltville thrust faults, respectively. Two doubly plunging anticlines lie along the strike of the basin. Lower Ordovician rocks are exposed in the Burkes Garden dome to the southwest, and Lower Cambrian rocks are present in the core of the Bane dome to the northeast. Previous workers have postulated continuity between the Burkes Garden and Bane domes through the Kimberling basin, as well as the presence in the basin of an anomalously thick Devonian clastic section, which has been ascribed by some authors to contemporaneous downwarp of a depositional syncline. Recent mapping has shown both of these postulates to be incorrect. The basin contains an anticline-syncline pair that is en echelon with the axes of the Burkes Garden and Bane anticlines and that trends about 20/degree/ more northerly than the regional strike of the bounding thrusts. Rediscovery of small outcrops of Lower and Middle Devonian Huntersville Chert and Rocky Gap Sandstone in the core of the Kimberling basin anticline, which were recorded by M.R. Campbell in 1896 but overlooked by later mappers, shows that the Devonian clastic sequence has a normal thickness and that the Kimberling basin contains a domal structure similar to the Burkes Garden and Bane domes.

  18. Aneurysm of the Left Coronary Artery in Postoperative Bland-White-Garland Syndrome.

    PubMed

    Bravo-Valenzuela, Nathalie Jeanne Magioli; Silva, Guilherme Ricardo Nunes

    2015-01-01

    We report a case of anomalous left coronary artery from the pulmonary artery (ALCAPA) or Bland-White-Garland syndrome, present the challenges of performing a differential diagnosis, and discuss the treatment of the syndrome. Although ALCAPA is a rare congenital heart disease, it is one of the most common causes of myocardial ischemia in childhood and presents a diagnostic challenge. A four-year-old girl was referred to a pediatric cardiologist for evaluation of mitral valve regurgitation murmur and heart failure. The transthoracic echocardiogram demonstrated the left coronary artery (LCA) not arising from the aorta, presence of coronary collateral circulation, and moderate mitral valve regurgitation. ALCAPA was confirmed using angiotomography. The LCA was surgically reimplanted into the aorta. After 3 years of postoperative follow-up, the patient developed an LCA aneurysm. Diagnosis of cardiac ischemia in childhood remains a challenge, and careful evaluation of coronary arteries on the echocardiogram is an important tool. In this report, we present a case of ALCAPA with an uncommon postoperative outcome. PMID:26770839

  19. Neogene and Quaternary coexisting in the geological time scale: The inclusive compromise

    NASA Astrophysics Data System (ADS)

    McGowran, Brian; Berggren, Bill; Hilgen, Frits; Steininger, Fritz; Aubry, Marie-Pierre; Lourens, Lucas; Van Couvering, John

    2009-11-01

    Removing the Tertiary and Quaternary Periods whilst conserving the Paleogene and Neogene Periods in The Geological Timescale 2004 caused a storm of protest. One response was to advocate restoring an enlarged Quaternary and consigning the Neogene to a minor role within the Tertiary. Amongst an array of practical, traditional, sentimental and anthropocentric reasons for this response, the one hard-core justification was that the rigidly nested hierarchy of the geological timescale must be preserved. The central objective of this paper is conserving the historically legitimate, Miocene-present, Neogene Period and System. There are two options for conserving the Quaternary concurrently with the Neogene: (i) an inclusive compromise in a flexible hierarchy, and (ii) an upgrading of Pliocene and Pleistocene divisions to the level of epoch. In the inclusive compromise there coexist alternative pathways through the hierarchical ranks. Thus geohistorians and biohistorians have two options for traversing the hierarchy from era to age, as in this example using the hierarchical positioning of the Calabrian Age and Stage: either Cenozoic [era]↔Neogene [period]↔Pleistocene [epoch]↔Calabrian [age], or Cenozoic [era]↔Quaternary [subera]↔Pleistocene [epoch]↔Calabrian [age]. We reaffirm that the inclusive compromise is entirely viable. In so doing we (i) challenge the necessity of the rigidly nested hierarchy, which should be capable of a little flexibility; (ii) reject all analogies of the arbitrary and conventional chronostratigraphic hierarchy with three natural biological hierarchies; (iii) reaffirm the integrity of the Neogene extending to the present; and (iv) see no reason to doubt the harmonious coexistence of the two options preserving the Quaternary and Neogene traditions in an orderly working and stable time scale. In the alternative schema conserving the Neogene, divisions of the Pliocene and Pleistocene are upgraded, so that the Late Pleistocene, Early

  20. Arctic-alpine blockfields in northern Sweden: Quaternary not Neogene

    NASA Astrophysics Data System (ADS)

    Goodfellow, B. W.; Stroeven, A. P.; Fabel, D.; Fredin, O.; Derron, M.-H.; Bintanja, R.; Caffee, M. W.

    2014-02-01

    Slowly-eroding, blockfield-mantled, non-glacial surface remnants may serve as markers against which to determine Quaternary glacial erosion volumes in high latitude mountain settings. To investigate this potential utility of these surfaces, chemical weathering, erosion rates, and origins of mountain blockfields are investigated in northern Sweden. This is done, firstly, by assessing the intensity of regolith chemical weathering along altitudinal transects descending from three blockfield-mantled summits. Clay/silt ratios, secondary mineral assemblages determined through X-ray diffraction, and the presence of chemically weathered grains visible on scanning electron microscopy, in fine matrix samples collected from pits excavated along the transects are each used for this purpose. Secondly, erosion rates and total surface histories of two of the summits are inferred from concentrations of in situ-produced cosmogenic 10Be and 26Al in quartz at the blockfield surface. An interpretative model is adopted that includes temporal variations in nuclide production rates through surface burial by glacial ice and glacial isostasy-induced elevation changes of the blockfield surfaces. Together, our data indicate that these blockfields are not derived from remnants of intensely weathered Neogene weathering profiles, as is commonly considered. Evidence for this interpretation includes minor chemical weathering in each of the three examined blockfields, despite some differences according to slope position. In addition, average erosion rates of ∼16.2 mm ka-1 and ∼6.7 mm ka-1, calculated for two blockfield-mantled summits, are low but of sufficient magnitude to remove present blockfield mantles, of up to a few meters in thickness, within a late-Quaternary timeframe. Hence, blockfield mantles appear to be replenished by regolith formation through, primarily physical, weathering processes that have operated during the Quaternary. Erosion rates remain low enough, however, for

  1. Neogene Development of the Terror Rift, western Ross Sea, Antarctica

    NASA Astrophysics Data System (ADS)

    Sauli, C.; Sorlien, C. C.; Busetti, M.; De Santis, L.; Wardell, N.; Henrys, S. A.; Geletti, R.; Wilson, T. J.; Luyendyk, B. P.

    2015-12-01

    Terror Rift is a >300 km-long, 50-70 km-wide, 14 km-deep sedimentary basin at the edge of the West Antarctic Rift System, adjacent to the Transantarctic Mountains. It is cut into the broader Victoria Land Basin (VLB). The VLB experienced 100 km of mid-Cenozoic extension associated with larger sea floor spreading farther north. The post-spreading (Neogene) development of Terror Rift is not well understood, in part because of past use of different stratigraphic age models. We use the new Rossmap seismic stratigraphy correlated to Cape Roberts and Andrill cores in the west and to DSDP cores in the distant East. This stratigraphy, and new fault interpretations, was developed using different resolutions of seismic reflection data included those available from the Seismic Data Library System. Depth conversion used a new 3D velocity model. A 29 Ma horizon is as deep as 8 km in the south, and a 19 Ma horizon is >5 km deep there and 4 km-deep 100 km farther north. There is a shallower northern part of Terror Rift misaligned with the southern basin across a 50 km right double bend. It is bounded by steep N-S faults down-dropping towards the basin axis. Between Cape Roberts and Ross Island, the Oligocene section is also progressively-tilted. This Oligocene section is not imaged within northern Terror Rift, but the simplest hypothesis is that some of the Terror Rift-bounding faults were active at least during Oligocene through Quaternary time. Many faults are normal separation, but some are locally vertical or even reverse-separation in the upper couple of km. However, much of the vertical relief of the strata is due to progressive tilting (horizontal axis rotation) and not by shallow faulting. Along the trend of the basin, the relief alternates between tilting and faulting, with a tilting margin facing a faulted margin across the Rift, forming asymmetric basins. Connecting faults across the basin form an accommodation zone similar to other oblique rifts. The Neogene basin is

  2. Pelagic crinoids (Roveacrinida, Crinoidea) discovered in the Neogene of Poland

    NASA Astrophysics Data System (ADS)

    Gorzelak, Przemysław; Salamon, Mariusz A.; Ferré, Bruno

    2011-10-01

    Until recently, it has been assumed that pelagic crinoids, the roveacrinids (Roveacrinida, Crinoidea), became extinct during the Cretaceous-Paleogene boundary event. Recent finds of well-preserved roveacrinidal remains (brachials and radials) in the Danian (Early Paleogene) of Poland showed that they survived into the earliest Cenozoic. This group was thus characterized as a "dead clade walking". Here, we present fossil evidence that these pelagic crinoids survived in Poland until at least the Middle Miocene (Badenian, ca. 14 Myr ago)—more than 50 Myr after their supposed extinction. These Miocene roveacrinids constitute the first documented evidence of Roveacrinida in strata of Neogene age, thus prolonging the stratigraphic range of pelagic crinoids. This find characterizes the order as a "Lazarus taxon" rather than a "dead clade walking" group.

  3. Europe's Neogene and Quaternary lake gastropod diversity - a statistical approach

    NASA Astrophysics Data System (ADS)

    Neubauer, Thomas A.; Georgopoulou, Elisavet; Harzhauser, Mathias; Mandic, Oleg; Kroh, Andreas

    2014-05-01

    During the Neogene Europe's geodynamic history gave rise to several long-lived lakes with conspicuous endemic radiations. However, such lacustrine systems are rare today as well as in the past compared to the enormous numbers of "normal" lakes. Most extant European lakes are mainly results of the Ice Ages and are due to their (geologically) temporary nature largely confined to the Pleistocene-Holocene. As glacial lakes are also geographically restricted to glacial regions (and their catchment areas) their preservation potential is fairly low. Also deposits of streams, springs, and groundwater, which today are inhabited by species-rich gastropod assemblages, are rarely preserved. Thus, the pre-Quaternary lacustrine record is biased towards long-lived systems, such as the Late Miocene Lake Pannon, the Early to Middle Miocene Dinaride Lake System, the Middle Miocene Lake Steinheim and several others. All these systems have been studied for more than 150 years concerning their mollusk inventories and the taxonomic literature is formidable. However, apart from few general overviews precise studies on the γ-diversities of the post-Oligocene European lake systems and the shifting biodiversity in European freshwater systems through space and time are entirely missing. Even for the modern faunas, literature on large-scale freshwater gastropod diversity in extant lakes is scarce and lacks a statistical approach. Our preliminary data suggest fundamental differences between modern and pre-Pleistocene freshwater biogeography in central Europe. A rather homogenous central European Pleistocene and Holocene lake fauna is contrasted by considerable provincialism during the early Middle Miocene. Aside from the ancient Dessaretes lakes of the Balkan Peninsula, Holocene lake faunas are dominated by planorbids and lymnaeids in species numbers. This composition differs considerably from many Miocene and Pliocene lake faunas, which comprise pyrgulid-, hydrobiid-, viviparid-, melanopsid

  4. Neogene biomarker record of vegetation change in eastern Africa

    PubMed Central

    Polissar, Pratigya J.; Jackson, Kevin E.; deMenocal, Peter B.

    2016-01-01

    The evolution of C4 grassland ecosystems in eastern Africa has been intensely studied because of the potential influence of vegetation on mammalian evolution, including that of our own lineage, hominins. Although a handful of sparse vegetation records exists from middle and early Miocene terrestrial fossil sites, there is no comprehensive record of vegetation through the Neogene. Here we present a vegetation record spanning the Neogene and Quaternary Periods that documents the appearance and subsequent expansion of C4 grasslands in eastern Africa. Carbon isotope ratios from terrestrial plant wax biomarkers deposited in marine sediments indicate constant C3 vegetation from ∼24 Ma to 10 Ma, when C4 grasses first appeared. From this time forward, C4 vegetation increases monotonically to present, with a coherent signal between marine core sites located in the Somali Basin and the Red Sea. The response of mammalian herbivores to the appearance of C4 grasses at 10 Ma is immediate, as evidenced from existing records of mammalian diets from isotopic analyses of tooth enamel. The expansion of C4 vegetation in eastern Africa is broadly mirrored by increasing proportions of C4-based foods in hominin diets, beginning at 3.8 Ma in Australopithecus and, slightly later, Kenyanthropus. This continues into the late Pleistocene in Paranthropus, whereas Homo maintains a flexible diet. The biomarker vegetation record suggests the increase in open, C4 grassland ecosystems over the last 10 Ma may have operated as a selection pressure for traits and behaviors in Homo such as bipedalism, flexible diets, and complex social structure. PMID:27274042

  5. Neogene biomarker record of vegetation change in eastern Africa.

    PubMed

    Uno, Kevin T; Polissar, Pratigya J; Jackson, Kevin E; deMenocal, Peter B

    2016-06-01

    The evolution of C4 grassland ecosystems in eastern Africa has been intensely studied because of the potential influence of vegetation on mammalian evolution, including that of our own lineage, hominins. Although a handful of sparse vegetation records exists from middle and early Miocene terrestrial fossil sites, there is no comprehensive record of vegetation through the Neogene. Here we present a vegetation record spanning the Neogene and Quaternary Periods that documents the appearance and subsequent expansion of C4 grasslands in eastern Africa. Carbon isotope ratios from terrestrial plant wax biomarkers deposited in marine sediments indicate constant C3 vegetation from ∼24 Ma to 10 Ma, when C4 grasses first appeared. From this time forward, C4 vegetation increases monotonically to present, with a coherent signal between marine core sites located in the Somali Basin and the Red Sea. The response of mammalian herbivores to the appearance of C4 grasses at 10 Ma is immediate, as evidenced from existing records of mammalian diets from isotopic analyses of tooth enamel. The expansion of C4 vegetation in eastern Africa is broadly mirrored by increasing proportions of C4-based foods in hominin diets, beginning at 3.8 Ma in Australopithecus and, slightly later, Kenyanthropus This continues into the late Pleistocene in Paranthropus, whereas Homo maintains a flexible diet. The biomarker vegetation record suggests the increase in open, C4 grassland ecosystems over the last 10 Ma may have operated as a selection pressure for traits and behaviors in Homo such as bipedalism, flexible diets, and complex social structure. PMID:27274042

  6. Paleohydrology of Southwestern Texas

    NASA Astrophysics Data System (ADS)

    Kochel, R. Craig; Baker, Victor R.; Patton, Peter C.

    1982-08-01

    Current statistical methods may be unable to accurately predict recurrence intervals of rare, large-magnitude floods, especially in semiarid regions having positively skewed annual flood distributions, great hydrologic variability, and widely spaced gaging stations. Current approaches rely on historical data, but catastrophic floods may have recurrence intervals far greater than the length of historical records. In the lower Pecos and Devils Rivers of southwestern Texas, paleoflood discharge and frequency estimates are extended over 10,000 years by the study of slack-water flood sediments. Slack-water deposits are typically fine-grained sand and silt that accumulate during floods in areas where current velocity is reduced, i.e., in back-flooded tributary mouths, channel expansions, downstream from bedrock spurs and/or slump blocks, and in shallow caves along bedrock walls. Radiocarbon dating of organic detritus in slack-water deposits establishes the flood chronology while paleoflood discharges can be estimated by slope-area techniques. Paleoflood information extracted from slack-water sediments can greatly extend flood records. These floods may be weighted like historical data in log Pearson type 3 calculations of flood frequency. Our morphostratigraphic approach combines recorded data with geomorphic evidence to derive estimates of flood frequency. This technique offers an inexpensive and rapid way to assess catastrophic flood risk.

  7. Lithofacies Associations and Depositional Environments of the Neogene Molasse succession, Pishin Belt, northwestern Pakistan

    NASA Astrophysics Data System (ADS)

    Kasi, A.; Kassi, A.; Friis, H.; Umar, M.

    2013-12-01

    The Pishin Belt is a NE-SW trending mixed flysch and molasse basin, situated at the northwestern part of Pakistan, bordered by Afghan Block of the Eurasian Plate in the west and Indian Plate in the east. Western boundary of the belt is marked by the well-known Chaman Transform Fault, whereas the Zhob Valley Thrust and Muslim Bagh-Zhob Ophiolite mark the eastern boundary. The Belt is divisible into six tectono-stratigraphic zones bounded by major thrusts. Muslim Bagh-Zhob Ophiolite is the base and Zone-I of this belt. Zone-II comprises shallow marine and flysch successions of the Eocene Nisai Formation and Oligocene Khojak Formation. The Early to Middle Miocene Dasht Murgha group comprises Zone-III, the Late Miocene-Pliocene Malthanai formation comprises Zone-IV, the Pleistocene Bostan Formation makes Zone-V, and the flat-laying Holocene deposits of the Zhob Valley comprise Zone-VI. The Neogene molasse successions of the Pishin Belt include the Dasht Murgha group, Malthanai formation and Bostan Formation; these are mostly composed of sandstone, claystone and conglomerate lithologies. Sandstones have been classified as lithic arenites and their QFL values suggest quartzolithic composition. Twelve distinct lithofacies have been recognized in the succession and thus grouped into four types of facies associations. Lithofacies include clast-supported massive gravel (Gcm), clast-supported crudely bedded gravel (Gh), cross-stratified conglomerate (Gt and Gp), trough cross-stratified sandstone (St), planar cross-stratified sandstone (Sp), ripple cross-laminated sandstone (Sr), horizontally stratified sandstone (Sh), low-angle cross-stratified sandstone (Sl), massive sandstones (Sm), massive mudstone and siltstone (Fm) and paleosol carbonate (P). The lithofacies associations include channel facies association (CHA), crevasse-splay facies association (CSA), natural-levee facies association (LVA) and floodplain facies association (FPA). The lithofacies associations suggest

  8. The geochemistry of the Neogene Halmahera Arc, eastern Indonesia

    NASA Astrophysics Data System (ADS)

    Forde, Emily Jane

    The Halmahera arc is a north-south linear intraoceanic arc cutting across the islands of Halmahera and Bacan in NE Indonesia. The arc is the result of the eastward subduction of the Molucca Sea Plate, accommodating the westward movement of the Pacific and Philippine Sea Plates (PSP) against the Eurasian margin. To the south of the Halmahera arc is a major left-lateral strike-slip fault system: the Sorong Fault Zone (SFZ), which separates the northward movement of Australia from the westward movement of the PSP. This plate boundary has been stable throughout the Neogene to the present day, and has been responsible for the transfer of continental fragments from the Australian margin into the southern Molucca Sea region. K/Ar dating has revealed the migration of volcanism along the length of the Halmahera arc from south to north. The oldest volcanics (ca. 11 Ma) are from Obi, the southernmost island in the region, where volcanism is now extinct. Moving north into Bacan, ages range from 7 Ma to the Quaternary, whereas in central Halmahera they range from 6 - 2 Ma. The present-day arc currently lies to the west of central Halmahera and stretches up the north-west arm of the island. On the basis of spatial, temporal and geochemical variations a possible seven Neogene volcanic centres can be distinguished along the length of the arc. Major element, trace element and Sr-Nd-Pb-O isotopic analyses reveal a wide diversity in geochemical characteristics between the centres. This is due to heterogeneity within the arc mantle wedge, the type of arc crust through which the volcanics were erupted and variations in contribution to the mantle wedge from a subducted component. Volcanic rocks from Obi, central Halmahera and north Bacan display geochemical characteristics typical of intraoceanic arc lavas. The lack of a continental component within these centres enables a greater understanding of the variety of processes and source components affecting arc magmatism in this region

  9. The Neogene Environment of the Beardmore Glacier, Transantarctic Mountains

    NASA Astrophysics Data System (ADS)

    Ashworth, A. C.; Cantrill, D. J.; Francis, J. E.; Roof, S. R.

    2004-12-01

    Discontinuous sequences of Neogene marine and non-marine glacigenic sequences, including the Meyer Desert Formation (MDF), occur throughout the Transantarctic Mountains. The upper 85m of the MDF, consisting of interbedded diamictites, conglomerates, sandstones and siltstones, outcrops in the Oliver Bluffs on the Beardmore Glacier at 85° 07'S, 166° 35'E. The location is about 170 km south of the confluence of the Beardmore Glacier with the Ross Ice Shelf and about 500 km north of the South Pole The glacial, fluvioglacial and glaciolacustrine facies of the MDF represent a dynamic glacial margin which advanced and retreated on at least four occasions. On at least one occasion, the retreat was sufficiently long for plants and animals to colonize the head of a major fjord which existed in the place of the existing Beardmore Glacier. From the fossils we have identified at least 18 species of plants, 3 species of insects, 2 species of freshwater mollusks, and a species of fish. The plant fossils consist of pollen, seeds, fruits, flowers, leaves, wood, and in situ plants. The plants include a cryptogamic flora of mosses and liverworts, conifers, and angiosperms in the families Gramineae, Cyperaceae, Nothofagaceae, Ranunculaceae, Hippuridaceae, ?Caryophyllaceae, and ?Chenopodiaceae or ?Myrtaceae. The plants grew in a weakly developed soil developed on a complex periglacial environment that included moraines, glacial outwash streams, well-drained gravel ridges, and poorly drained depressions in which peat and marl were being deposited. The fossil assemblage represents a mosaic tundra environment of well- and poorly-drained micro-sites, in which nutrient availability would have been patchily distributed. Antarctica has been essentially in a polar position since the Early Cretaceous and at 85° S receives no sunlight from the middle of March until the end of September. Today, the annual radiation received is about 42% that of Tierra del Fuego at 55° S. During the Neogene

  10. Late Neogene changes in diatom sedimentation in the North Pacific

    USGS Publications Warehouse

    Barron, J.A.

    1998-01-01

    During the late Neogene, North Pacific diatom sedimentation underwent major changes in response to high-latitude cooling and changes in surface and deep water circulation. At 9 Ma diatom mass accumulation rates (MARs) increased in the NW Pacific and off northeast Japan, possibly due to shoaling of the Isthmus of Panama, which lead to an enrichment of nutrients in North Pacific deep waters. During the latest Miocene, diatom MARs increased progressively off southern California (6.5 Ma), at high latitudes of the North Pacific (6.2 Ma), and off northeastern Japan (5.5 Ma), presumably in response to high latitude cooling. At about 4.5 Ma diatom sedimentation abruptly increased in the NW Pacific but declined off Japan and California, coincident with the onset of a prolonged period of high-latitude warmth. Enhanced upwelling of nutrient-rich deep waters in the NW Pacific probably stimulated diatom production there. A major step in high latitude cooling at 2.7 Ma caused a reversal of these mid Pliocene diatom sedimentation patterns. Upwelling of deep, nutrient-rich waters waned at higher latitudes, leading to a decline in diatom productivity; while wind-driven, coastal upwelling increased off southern California and stimulated diatom growth.

  11. Neogene biostratigraphy and paleoenvironments of Enewetak Atoll, equatorial Pacific Ocean

    USGS Publications Warehouse

    Cronin, T. M.; Bybell, L.M.; Brouwers, E.M.; Gibson, T.G.; Margerum, R.; Poore, R.Z.

    1991-01-01

    Micropaleontologic analyses of Neogene sediments from Enewetak Atoll, Marshall Islands, provide data on the age of lagoonal deposits, stratigraphic disconformities and the paleoenvironmental and subsidence history of the atoll. Benthic foraminifers, planktic foraminifers, calcareous nannofossils and ostracodes were studied from six boreholes, the deepest penetrating 1605 feet below the lagoon floor into upper Oligocene strata. The Oligocene-Miocene boundary occurs at about 1200 ft below the lagoon floor. The early and middle Miocene is characterized by brief periods of deposition and numerous hiatuses. Ostracodes and benthic foraminifers indicate a shallow-marine reefal environment with occasional brackish water conditions. Upper Miocene and lower Pliocene deposits placed in calcareous nannofossil Zones NN9-15 and in planktic foraminifer Zones N16-19 contain species-rich benthic microfaunas which indicate alternating reefal and brackish water mangrove environments. The upper Pliocene contains at least two major depositional hiatuses that coincide with a major faunal turnover in benthic foraminiferal and ostracode assemblages. The Quaternary is characterized by benthic microfaunas similar to those of modern atoll lagoons and is punctuated by at least 11 disconformities which signify periods of low sea level. Atoll subsidence rates during the last 10 Ma averaged 30 to 40 m/m.y. ?? 1991 Elsevier Science Publishers B.V. All rights reserved.

  12. Paleomagnetic studies on Neogene rocks from southern California

    SciTech Connect

    Luyendyk, B.P.

    1988-03-01

    For the past 13 years, the paleomagnetism of Neogene age volcanic and sedimentary rocks in southern California has been studied. Volcanic rocks studied are mostly early and middle Miocene. Sedimentary rocks studied are mostly middle and late Miocene dolostones from the Monterey Formation. Clockwise declination anomalies are prominent and are interpreted as indicators of clockwise tectonic rotation. West of the San Andreas fault in the western Transverse Ranges and Channel Islands, clockwise rotation began during the middle Miocene, paused in late Miocene, and resumed in the Pliocene. An exception is the San Gabriel Mountain region, which possibly has rotated counterclockwise since late Miocene. East of the San Andreas fault, clockwise rotations took place in the central Mojave Desert during the early Miocene. The Orocopia Mountains region may have rotated clockwise during the middle Miocene. The Eastern Transverse Ranges rotated clockwise mostly during post-Miocene time and some parts of the Mojave Desert rotated counterclockwise. Magnetic reversal stratigraphy has been studied for a few sections in the Monterey Formation. Control is dictated by the abundance of dolostone beds, as other lithologies do not possess a primary remanence. Five sections along the north coast of the Santa Barbara Channel have been correlated to the magnetic polarity time scale by J. S. Hornafius. Study of two thick sections of early Miocene flows from the Soledad basin by R.R. Terres yielded a detailed scheme of secular variation. Elsewhere, flow sequences are too short and discontinuous in time to yield a magnetic reversal stratigraphy.

  13. Late Neogene marine incursions and the ancestral Gulf of California

    USGS Publications Warehouse

    McDougall, K.

    2008-01-01

    The late Neogene section in the Salton Trough, California, and along the lower Colorado River in Arizona is composed of marine units bracketed by nonmarine units. Microfossils from the marine deposits indicate that a marine incursion inundated the Salton Trough during the late Miocene. Water depths increased rapidly in the Miocene and eventually flooded the region now occupied by the Colorado River as far north as Parker, Arizona. Marine conditions were restricted in the Pliocene as the Colorado River filled the Salton Trough with sediments and the Gulf of California assumed its present configuration. Microfossils from the early part of this incursion include a diverse assemblage of benthic foraminifers (Amphistegina gibbosa, Uvigerina peregrina, Cassidulina delicata, and Bolivina interjuncta), planktic foraminifers (Globigerinoides obliquus, G. extremus, and Globigerina nepenthes), and calcareous nannoplankton (Discoaster brouweri, Discoaster aff. Discoaster surculus, Sphenolithus abies, and S. neoabies), whereas microfossils in the final phase contain a less diverse assemblage of benthic foraminifers that are diagnostic of marginal shallow-marine conditions (Ammonia, Elphidium, Bolivina, Cibicides, and Quinqueloculina). Evidence of an earlier middle Miocene marine incursion comes from reworked microfossils found near Split Mountain Gorge in the Fish Creek Gypsum (Sphenolithus moriformis) and near San Gorgonio Pass (Cyclicargolithus floridanus and Sphenolithus heteromorphus and planktic foraminifers). The middle Miocene incursion may also be represented by the older marine sedimentary rocks encountered in the subsurface near Yuma, Arizona, where rare middle Miocene planktic foraminifers are found. ?? 2008 The Geological Society of America.

  14. Drought in Southwestern United States

    NASA Technical Reports Server (NTRS)

    2007-01-01

    The southwestern United States pined for water in late March and early April 2007. This image is based on data collected by the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA's Terra satellite from March 22 through April 6, 2007, and it shows the Normalized Difference Vegetation Index, or NDVI, for the period. In this NDVI color scale, green indicates areas of healthier-than-usual vegetation, and only small patches of green appear in this image, near the California-Nevada border and in Utah. Larger areas of below-normal vegetation are more common, especially throughout California. Pale yellow indicates areas with generally average vegetation. Gray areas appear where no data were available, likely due to persistent clouds or snow cover. According to the April 10, 2007, update from the U.S. Drought Monitor, most of the southwestern United Sates, including Utah, Nevada, California, and Arizona, experienced moderate to extreme drought. The hardest hit areas were southeastern California and southwestern Arizona. Writing for the Drought Monitor, David Miskus of the Joint Agricultural Weather Facility reported that March 2007 had been unusually dry for the southwestern United States. While California's and Utah's reservoir storage was only slightly below normal, reservoir storage was well below normal for New Mexico and Arizona. In early April, an international research team published an online paper in Science noting that droughts could become more common for the southwestern United States and northern Mexico, as these areas were already showing signs of drying. Relying on the same computer models used in the Intergovernmental Panel on Climate Change (IPCC) report released in early 2007, the researchers who published in Science concluded that global warming could make droughts more common, not just in the American Southwest, but also in semiarid regions of southern Europe, Mediterranean northern Africa, and the Middle East.

  15. Differences in habitat use by blanding's turtles, Emydoidea blandingii, and painted turtles, Chysemys picta, in the Nebraska sandhills

    USGS Publications Warehouse

    Bury, R. Bruce; Germano, David J.

    2003-01-01

    We sampled a variety of wetlands in the Nebraska sandhills at Valentine National Wildlife Refuge. Significantly more individuals of painted turtles (Chrysemys picta) occurred in lakes and open waters than in marshes or small ponds, and the opposite was true for Blanding's turtles (Emydoidea blandingii). Besides this marked difference in habitat use, 46% of the captured E. blandingii in pond/marsh habitat were juveniles, but only 31.6% in lakes and open water. Current information suggests that marshes and small ponds are important habitat for juvenile turtles, especially Emydoidea blandingii.

  16. Himalaya evolution at Paleogene-Neogene boundary unraveled by zircon age spectrum from Arabian Sea Sediments

    NASA Astrophysics Data System (ADS)

    Feng, Han; Lu, Huayu; Zhang, Hanzhi

    2016-04-01

    Although virtually all the intensive orogenic activities of Himalaya occurred in Neogene, the tectonic evolution of this high mountain range in Paleogene is poorly understood. Investigations of tectonic change pattern at Paleogene-Neogene boundary are important to better understand the interaction between mountain building and climate evolution. Here we present new U-Pb ages of zircon grains from Indus Fan sediments to constrain the orogenic history of Himalaya at Paleogene-Neogene boundary. 11 samples between late Oligocene and early Miocene from ODP 117 cores are dated by the zircon U-Pb technique. We calculate relative contributions of potential sources by counting zircon grains for each sample, and the quantized results indicate Himalaya contributed sediments to the coring site, and an extremely high input from Great and Tethyan Himalaya during late Oligocene-early Miocene. Four samples in Pleistocene are also dated for comparison, which indicates that high proportion of Lesser Himalaya has contributed to the sediment in Pleistocene. Our results suggest that the high contribution of Great and Tethyan Himalaya at Paleogene-Neogene boundary might correlate with the beginning of activity of MCT and extension of STD with leucogranite intrusion along Himalaya, which give rise to the extensive Great Himalaya exhumation. Our study demonstrates that zircon U-Pb dating technique is a good tool to reconstruct erosional history of mountain building on a tectonic timescale. Key words: ODP, Himalaya, Indus Fan, zircon U-Pb dating, Paleogene-Neogene boundary

  17. REGIONAL PARADOX FORMATION STRUCTURE AND ISOCHORE MAPS, BLANDING SUB-BASIN, UTAH

    SciTech Connect

    Kevin McClure; Craig D. Morgan; Thomas C. Chidsey Jr.; David E. Eby

    2003-12-01

    Over 400 million barrels (64 million m{sup 3}) of oil have been produced from the shallow-shelf carbonate reservoirs in the Pennsylvanian (Desmoinesian) Paradox Formation in the Paradox Basin, Utah and Colorado. With the exception of the giant Greater Aneth field, the other 100 plus oil fields in the basin typically contain 2 to 10 million barrels (0.3-1.6 million m{sup 3}) of original oil in place. Most of these fields are characterized by high initial production rates followed by a very short productive life (primary), and hence premature abandonment. Only 15 to 25 percent of the original oil in place is recoverable during primary production from conventional vertical wells. An extensive and successful horizontal drilling program has been conducted in the giant Greater Aneth field (figure 1). However, to date, only two horizontal wells have been drilled in small Ismay and Desert Creek fields. The results from these wells were disappointing due to poor understanding of the carbonate facies and diagenetic fabrics that create reservoir heterogeneity. These small fields, and similar fields in the basin, are at high risk of premature abandonment. At least 200 million barrels (31.8 million m{sup 3}) of oil will be left behind in these small fields because current development practices leave compartments of the heterogeneous reservoirs undrained. Through proper geological evaluation of the reservoirs, production may be increased by 20 to 50 percent through the drilling of low-cost single or multilateral horizontal legs from existing vertical development wells. In addition, horizontal drilling from existing wells minimizes surface disturbances and costs for field development, particularly in the environmentally sensitive areas of southeastern Utah and southwestern Colorado.

  18. Reef productivity and preservation during the Late Neogene

    NASA Astrophysics Data System (ADS)

    Husson, Laurent; Pastier, Anne-Morwenn; Schmitt, Anais; Sarr, Anta-Clarisse; Elliot, Mary; Pedoja, Kevin; Bezos, Antoine

    2016-04-01

    During the glacial-interglacials cycles that prevailed during Plio-Pleistocence times, the pace of sea level oscillations exerts a major control on coral reef growth and expansion. We designed a numerical model to quantify reef productivity and carbonate preservation that accounts for sea level oscillations, reef growth, erosion and subsequent geomorphological carving. We carried out a parametric study of a variety of processes (reef growth, erosion, local slope, uplift and subsidence, relative sea level, etc) towards a probabilistic analysis of reef productivity and carbonate production. We further test the effect of the frequency and amplitude of sea level oscillations using sea level curves derived from both the 18O isotope record of past sea level change and synthetic sinusoidal sea level curves. Over a typical climate cycle, our model simulations confirm that the rate of sea level change is the primary controlling factor of reef production, as it modifies the productivity by several orders of magnitude. Most importantly, reef productivity increases during periods of sea level rise, and decreases during sea level stands, while conversely, the morphology records the opposite in a misleading fashion: Reef terraces expand during sea level stands due to the joint effects of erosion and patient reef growth at a stationary level until the accommodation space is filled up. On the long-term, over the Plio-Pleistocene period, vertical ground motion also significantly alters the production: moderate uplift or subsidence can boost reef productivity up to tenfold with respect to a stationary coastline. Last, the amplitude and frequency of the sea level oscillations (typically 40 kyrs vs. 100 kyrs periods) moderately impact reef productivity. These results can be ultimately converted into estimates of carbonate production and carbon sequestration during the Late Neogene, provided relative sea level is documented in the tectonically agitated intertropical zone.

  19. Neogene rhyolites of the northern Jemez volcanic field, New Mexico

    SciTech Connect

    Loeffler, B.M.; Vaniman, D.T.; Baldridge, W.S.; Shafiqullah, M.

    1988-06-10

    Volcanic centers previously mapped as the 20 Ma El Rechuelos Rhyolite in the northern Jemez volcanic field, New Mexico, include three distinct episodes of rhyolitic volcanism. An early (7.5 Ma) extrusive dome of flow-banded biotite rhyolite and an intermediate (5.8 Ma) rhyolite, possibly a volcanic neck, correspond in age to rhyolites of the Keres Group in the southern Jemez volcanic field. Three other extrusive domes of aphyric, pumiceous rhyolite and obsidian comprise a late volcanic episode, dated at 2.0 Ma. We retain the name El Rechuelos Rhyolite only for these late centers. Another center, farther north than the others but previously mapped with the El Rechuelos Rhyolite, is a dacite pumice ring whose age (5.2 Ma), petrography, major- and trace-element chemistry, and Sr initial ratio all suggest it should be included with rocks of the Tschicoma Formation. Nd and Sr isotopic ratios of the Neogene rhyolites of the northern Jemez volcanic field suggest that these rhyolites were not produced by partial melting of either upper or lower crust. Rather, they may have been generated from a mantle-derived mafic magma, such as the nearby Lobato Basalt, by fractional crystallization with concomitant assimilation of small amounts (<6%) of lower crust. If the El Rechuelos is derived from a lower crust magma chamber, as seems likely, then it is not related to the bandelier magma system, even though it is part of a continuum of rhyolite volcanism ranging from 3.6 Ma to 130,000 years ago that includes the Bandelier and precursor rhyolitic units. copyright American Geophysical Union 1988

  20. The changing course of the Orinoco River during the neogene

    SciTech Connect

    Diaz de Gamero, M.L. )

    1993-02-01

    Recent studies have revealed that the varied fresh-water vertebrate fossil fauna of the Urumaco Formation in northwestern Falcon, of Late Miocene age, belongs biogeographically to the Orinoco River system. This makes possible to chart the changing course of the Orinoco River through the Neogene. The Misoa delta of Lake Maracaibo, of middle Eocene age, was probably constructed by a proto-Orinoco river that ran in a south-north direction, draining the Central Cordillera of Colombia and the Guayana Highlands. The late Eocene uplifting of western Venezuela changed the paleogeographic setting, with no evidence of delta-building during the Oligocene. In the earliest Miocene, the Falcon Basin was the site of marine shale sedimentation. In the second half of the Early Miocene, a deltaic sequence was initiated in northwestern Falcon that continued, except for a transgressive episode, until the end of the Middle Miocene, depositing a total thickness of over 2.5 km. The Urumaco overlies this sequence and its vertebrate fauna indicates that the river that built the previous delta was the proto-Orinoco. The initial uplifting of the northern part of the Andes and the western edge of the Caribbean Mountains can thus be dated to occur at the end of the Middle Miocene, causing the distal course of the river to move to a west-east direction. The sedimentary record of the Orinoco River delta appears in the Maturin Basin of eastern Venezuela at the end of the Miocene, and is especially evident in Trinidad and the Columbus Basin during the Pliocene and Pleistocene.

  1. Sequence stratigraphic framework of Neogene strata in offshore Nigeria

    SciTech Connect

    Pacht, J.A.; Bowen, B.E.; Hall, D.J.

    1996-08-01

    The western portion of the Nigerian continental margin (Dahomey Basin) exhibits stable to moderately unstable progradation. Systems tracts are similar to those described by Vail for stable progradational margins. In contrast, strata off the central and eastern portions of the Nigerian coast (Niger Delta Complex) exhibit highly unstable progradation, and systems tracts are similar to those in Neogene strata of the offshore Gulf of Mexico. Lowstand basin floor fans in both areas are defined by a well-developed upper reflection. This reflection downlaps along the sequence boundary or abuts against the downthrown side of a growth fault surface. Most lower lowstand (slope fan) strata exhibit discontinuous to semi-continuous subparallel reflections. However, this systems tract also contains channel complexes characterized by chaotic bedding with small bright spots and less common large channels, which exhibit concave-upward reflections. In the western portion of the study area, lower lowstand deposits commonly pinch out on the slope. Deposition occurred largely from point sources. In contrast, contemporaneous shallow-water facies are developed in lower lowstand systems tracts in the Niger Delta Complex. Deposition occurred along a line source. Large amplitude anomalies in the upper lowstand (prograding wedge) suggest well-developed sheet sands occur in shallow-water and deep-water in the Niger Delta complex. However, in the Dahomey Basin there is little evidence of deep-water sands in this interval. The transgressive and highstand systems tracts are usually very thin in outer shelf to basin floor strata in both areas. Both the Dahomey Basin and Niger Delta Complex exhibit different stratigraphic geometries, and therefore, require different exploration strategies.

  2. Neogene coupling between Kuqa Basin and Southern Tien Shan Orogen, Northwestern China.

    PubMed

    He, Guang-Yu; Chen, Han-Lin

    2004-08-01

    Based on the sedimentary and subsiding features of Kuqa foreland basin, this paper presents the following characteristics of Neogene coupling relationship between Kuqa Basin and Southern Tien Shan Orogen, Northwestern China: (1) The Southern Tien Shan Orogen underwent Neogene uplifting of 4 km in height and the Kuqa Basin underwent Neogene subsidence of 4-6 km in depth accordingly beginning in 25 Ma; (2) The Southern Tien Shan Orogen moved continuously toward the Kuqa Basin, with largest structural shortening rate of greater than 53.7%, and the north boundary of the Kuqa Basin retreated continuously southward accordingly since the Miocene; (3) There are two subsidence centers with high subsiding rates and large subsiding extent, located in the eastern and western Kuqa Basin respectively, with the subsiding maximizing in the deposition period of Kuqa Formation. PMID:15236483

  3. Southwestern Power Administration Update, October- December 2004

    SciTech Connect

    2004-12-01

    On October 29, 2004, Southwestern and Southwest Power Pool, Inc. (SPP) reached agreement on interim arrangements to be implemented after the October 31, 2004, expiration of the membership agreement between the two parties. According to Jim McDonald, Director of Southwestern’s Division of Customer Service, the interim agreement forged between Southwestern and SPP seeks to minimize impacts to SPP as well as to Southwestern and its customers while Southwestern and SPP work on a seams/coordination agreement to succeed the expired membership agreement.

  4. Reconstructing the cosmogenic 21Ne inventory of Neogene sedimentary sequences

    NASA Astrophysics Data System (ADS)

    Stuart, Finlay; Sinclair, Hugh; McCann, Louise

    2016-04-01

    Ne is ubiquitous. The data require minimum average pebble transport times of 150 kyr. A similar distribution of cosmogenic Ne concentrations is present in quartzite pebbles from gravels from the Pliocene Broadwater Formation and Miocene Ogallala Formation gravels indicates that the rates of transport and pebble recycling on flood plain have not changed over the Neogene. [1] Margerison et al. (2005) Earth Planet. Sci. Lett. 230, 163-175. [2] Codilean et al. (2008) Geology 36, 159-162.

  5. Silicic Magma Genesis in Neogene Central Volcanoes in Northeast Iceland

    NASA Astrophysics Data System (ADS)

    Berg, S. E.; Troll, V. R.; Riishuus, M. S.; Burchardt, S.; Krumbholz, M.

    2012-04-01

    We report on a geological expedition to NE Iceland in August 2011. A comprehensive sample suite of intrusive and extrusive rocks, ranging from basaltic to silicic compositions, was collected from the Neogene silicic central volcanic complexes in the region between Borgarfjörður eystri and Loðmundarfjörður. The area contains the second-most voluminous occurrence of silicic rocks in Iceland, including caldera structures, inclined sheet swarms, extensive ignimbrite sheets, sub-volcanic rhyolites and silicic lava flows. Yet it is one of Iceland's geologically least known areas (c.f. Gústafsson, 1992; Martin & Sigmarsson, 2010; Burchardt et al., 2011). The voluminous occurrence of evolved rocks in Iceland (10-12 %) is very unusual for an ocean island or a mid-oceanic ridge, with a typical signal of magmatic bimodality, often called "Bunsen-Daly" compositional gap (e.g. Bunsen, 1851; Daly, 1925; Barth et al., 1939). The Bunsen-Daly Gap is a long-standing fundamental issue in petrology and difficult to reconcile with continuous fractional crystallization as a dominant process in magmatic differentiation (Bowen, 1928), implying that hydrothermal alteration and crustal melting may play a significant role. Our aim is to contribute to a solution of this issue by unravelling the occurrence of voluminous evolved rhyolites in NE Iceland. We will use a combined petrological, textural, experimental and in-situ isotope approach. We plan to perform major, trace element and Sr-Nd-Hf-Pb-He-O isotope geochemistry, as well as U/Pb and Ar/Ar geochronology on rocks and mineral separates. In addition, high pressure-temperature partial melting experiments aim to reproduce and further constrain natural processes. Using the combined data set we intend to produce a comprehensive and quantitative analysis of rhyolite petrogenesis, and of the temporal, structural and geochemical evolution of the silicic volcanism in NE Iceland. The chosen field area serves as a good analogue for active

  6. 8. VIEW OF EL PASO AND SOUTHWESTERN RAILROAD BRIDGE, PIER ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    8. VIEW OF EL PASO AND SOUTHWESTERN RAILROAD BRIDGE, PIER BETWEEN EAST APPROACH AND RAILROAD, LOOKING NORTH. - El Paso & Southwestern Railroad Rio Grande Bridge, Spanning Rio Grande at Southwestern Railroad, El Paso, El Paso County, TX

  7. 7. VIEW OF EL PASO AND SOUTHWESTERN RAILROAD BRIDGE, PIER ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    7. VIEW OF EL PASO AND SOUTHWESTERN RAILROAD BRIDGE, PIER BETWEEN HIGHWAY AND RAILROAD, LOOKING NORTH. - El Paso & Southwestern Railroad Rio Grande Bridge, Spanning Rio Grande at Southwestern Railroad, El Paso, El Paso County, TX

  8. 4. GENERAL VIEW OF EL PASO AND SOUTHWESTERN RAILROAD BRIDGE, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    4. GENERAL VIEW OF EL PASO AND SOUTHWESTERN RAILROAD BRIDGE, RAILROAD SPAN, LOOKING NORTH. - El Paso & Southwestern Railroad Rio Grande Bridge, Spanning Rio Grande at Southwestern Railroad, El Paso, El Paso County, TX

  9. [Coronary artery bypass graft for Bland-White-Garland syndrome in an old age; report of a case].

    PubMed

    Komagamine, Masahide; Saito, Satoshi; Nishinaka, Tomohiro; Katsube, Ken; Yamazaki, Kenji

    2010-12-01

    We report a case of Bland-White-Garland syndrome with advanced age. The patient, a 67-year-old women, presented with a history of congestive heart failure. Coronary catheterization revealed an anomalous origin of the left coronary artery (LCA) from the trunk of the pulmonary artery and huge right coronary aneurysm. Myocardial single photon emission computed tomography (SPECT) showed previous myocardial infarction with reversible ischemia in left anterior descending (LAD) region. We performed LCA direct closure and coronary artery bypass graft. The patient recovered uneventfully without signs of ischemia. Although a bypass graft was patent, left ventricular function had not been improved immediately probably due to the coronary flow pattern changes. PMID:21174671

  10. Digital Database of Selected Aggregate and Related Resources in Ada, Boise, Canyon, Elmore, Gem, and Owyhee Counties, Southwestern Idaho

    USGS Publications Warehouse

    Moyle, Phillip R.; Wallis, John C.; Bliss, James D.; Bolm, Karen D.

    2004-01-01

    The U.S. Geological Survey (USGS) compiled a database of aggregate sites and geotechnical sample data for six counties - Ada, Boise, Canyon, Elmore, Gem, and Owyhee - in southwest Idaho as part of a series of studies in support of the Bureau of Land Management (BLM) planning process. Emphasis is placed on sand and gravel sites in deposits of the Boise River, Snake River, and other fluvial systems and in Neogene lacustrine deposits. Data were collected primarily from unpublished Idaho Transportation Department (ITD) records and BLM site descriptions, published Army Corps of Engineers (ACE) records, and USGS sampling data. The results of this study provides important information needed by land-use planners and resource managers, particularly in the BLM, to anticipate and plan for demand and development of sand and gravel and other mineral material resources on public lands in response to the urban growth in southwestern Idaho.

  11. Lithosphere-scale thrusting in the western US Cordillera as constrained by Sr and Nd isotopic transitions in Neogene volcanic rocks

    SciTech Connect

    Leeman, W.P.; Oldow, J.S. ); Hart, W.K. )

    1992-01-01

    The western Idaho suture zone juxtaposes continental and oceanic terranes with distinctive Sr and Nd isotopic signatures across a sharp isotopic transition coincident with the Mesozoic {sup 87}Sr/{sup 86}Sr = 0.706 line (MSL). Late Cretaceous to Eocene granitic plutons that define the MSL are allochthonous and were transported eastward by {approximately}150 km during late Mesozoic to Tertiary (ca. 100-55 Ma) thrusting. Sr and Nd isotopic compositions of Neogene rhyolites and basalts from southwestern Idaho, southeastern Oregon, and northern Nevada define isotopic transitions coincident with the MSL; there are continental affinities east of long 116{degree}30minutesW and oceanic affinities west of 119W. Between these longitudes, intermediate isotopic compositions imply derivation of magmas from both continental and oceanic mantle (basalts) and crustal (rhyolites) sources. It is inferred that the basal decollement of the Mesozoic and Tertiary contractional orogen dips westward below depths of segregation of basaltic magmas, and that oceanic lithospheric mantle was thrust eastward over a shelf of old, isotopically evolved continental lithospheric mantle that now protrudes {approximately}150 km west of the MSL.

  12. Integrated multidisciplinary biostratigraphic and paleoecologic study of southern California Neogene coastal sections

    SciTech Connect

    Blake, G.H.; Arends, R.G.; Filewicz, M.V.; Thornton, M.L.C.; Vork, D.R.

    1988-03-01

    This integrated biostratigraphic and paleoecologic study of several Neogene sections of coastal southern California is based on the use of diatoms, calcareous nannofossils, palynology, and benthic foraminifera. The study included the Naples Bluff, Topanga Canyon, and Newport Bay sections, and DSDP Site 468.

  13. As Old as the Hills: Montane Scorpions in Southwestern North America Reveal Ancient Associations between Biotic Diversification and Landscape History

    PubMed Central

    Bryson, Robert W.; Riddle, Brett R.; Graham, Matthew R.; Smith, Brian Tilston; Prendini, Lorenzo

    2013-01-01

    Background The age of lineages has become a fundamental datum in studies exploring the interaction between geological transformation and biotic diversification. However, phylogeographical studies are often biased towards lineages that are younger than the geological features of the landscapes they inhabit. A temporally deeper historical biogeography framework may be required to address episodes of biotic diversification associated with geologically older landscape changes. Signatures of such associations may be retained in the genomes of ecologically specialized (stenotopic) taxa with limited vagility. In the study presented here, genetic data from montane scorpions in the Vaejovis vorhiesi group, restricted to humid rocky habitats in mountains across southwestern North America, were used to explore the relationship between scorpion diversification and regional geological history. Results Strong phylogeographical signal was evident within the vorhiesi group, with 27 geographically cohesive lineages inferred from a mitochondrial phylogeny. A time-calibrated multilocus species tree revealed a pattern of Miocene and Pliocene (the Neogene period) lineage diversification. An estimated 21 out of 26 cladogenetic events probably occurred prior to the onset of the Pleistocene, 2.6 million years ago. The best-fit density-dependent model suggested diversification rate in the vorhiesi group gradually decreased through time. Conclusions Scorpions of the vorhiesi group have had a long history in the highlands of southwestern North America. Diversification among these stenotopic scorpions appears to have occurred almost entirely within the Neogene period, and is temporally consistent with the dynamic geological history of the Basin and Range, and Colorado Plateau physiographical provinces. The persistence of separate lineages at small spatial scales suggests that a combination of ecological stenotopy and limited vagility may make these scorpions particularly valuable indicators

  14. Magnetostratigraphy of the Neogene sediments of SW Uruguay

    NASA Astrophysics Data System (ADS)

    Sanchez Bettucci, L.; Orgeira, M. J.; Sanchez, G.; Bertoni-Machado, C.; Farina, R.

    2007-05-01

    Preliminary results on the magnetostratigraphy of three Neogene formations from SW Uruguay are presented: Camacho, Raigón and Libertad, and a relative age from the record of reversions in the Earth's magnetic field polarity is proposed. The sediments outcrop in the SW region of Uruguay,and have been received attention due to their fossil contents. The oldest is the late Miocene-Pliocene Camacho Fm, of Huayquerian to Montehermosan affinities. A Pliocene-early Pleistocene age has been assigned to Raigón Fm, of Chapadmalalan affinities. The overlying Libertad Fm has been considered early-middle Pleistocene in age, and to have Marplatan-Ensenadan affinities. The lithology of this facies of Camacho Fm is identified by the presence of fine to very fine sandstones and is composed of silty-sandy and bioturbed silty deposits. The marine facies of this formation is rich in fossil content, as several invertebrate and vertebrate taxa are found. The upper Raigón Fm is formed by sandstones of varied grain size and includes lenses and levels of claystones and conglomerates. It shows the sedimentological features of a deep, pebble-rich braided fluvial system. The 383 vertebrate specimens found in the sandy facies and studied in a taphonomically-oriented study belong to 19 genera and 13 higher taxa. The bones are disarticulated, with smooth fractures and little weathered or abraded, which is congruent with a short time of contact, as observed in strong and sudden flows. The elements belong to the three Voorhies groups and fractured specimens are found along with well preserved materials, implying different taphonomical histories and reworking. The consequent inferred time averaging urges caution at using these remains for defining precise ages. The Libertad Fm, top of the sequence, is conformed by greenish clays, clayey fine sandstones, medium sized sandstones and conglomeratic levels, corresponding to deposits of continental origin under a semiarid climate, which allowed the

  15. Neogene transtensional brittle tectonics in the Lepontine D

    NASA Astrophysics Data System (ADS)

    Allanic, C.; Sue, C.; Champagnac, J.-D.

    2009-04-01

    -parallel extensional phase, at least in the Lepontine Dome. We propose a kinematic model for the Central Alps in which the emplacement of the Lepontine Dome is driven by a pull-apart-like process controlled by the counterclockwise rotation of the Apulian indenter. This model refers to the paleostress field we documented and to kinetics of the main faults bounding the dome. Associated to these processes, lateral escape linked to the Apulia indentation/rotation would have enhanced the global extensional scheme of the Lepontine Dome. REFERENCES Allanic, C., et al. (2006), A paleo-seismogenic Lepontine dome? New insights from pseudotachylytes-generating faults, Geochimica et Cosmochimica Acta, Vol. 70 (18), Suppl. 1, p9 Goldschmidt conf. Melbourne. Bistacchi, A., and Massironi M. (2000), Post-nappe brittle tectonics and kinematic evolution of the north-western Alps: an integrated approach, Tectonophysics, 327, 267-292. Champagnac, J. D., Sue, C., Delacou, B., Burkhard, M. (2006), Miocene orogen-parallel extension in the inner Western Alps revealed by dynamical fault analyses, Tectonics, 25, 1-26. Ciancaleoni, L., and Marquer D. (2008), Late Oligocene to early Miocene lateral extrusion at the eastern borders of the Lepontine dome of the Central Alps (Bergell and Insubric areas, Eastern Central Alps), Tectonics, 27, TC4008, doi:10.1029/2007TC002196, 2008. Grosjean, G., Sue, C., Burkhard, M. (2004), Late Neogene brittle extension in the vicinity of the Simplon fault zone, central Alps, Switzerland., Eclogae Geologicae Helvetiae, 97, 33-46.

  16. How to regress and predict in a Bland-Altman plot? Review and contribution based on tolerance intervals and correlated-errors-in-variables models.

    PubMed

    Francq, Bernard G; Govaerts, Bernadette

    2016-06-30

    Two main methodologies for assessing equivalence in method-comparison studies are presented separately in the literature. The first one is the well-known and widely applied Bland-Altman approach with its agreement intervals, where two methods are considered interchangeable if their differences are not clinically significant. The second approach is based on errors-in-variables regression in a classical (X,Y) plot and focuses on confidence intervals, whereby two methods are considered equivalent when providing similar measures notwithstanding the random measurement errors. This paper reconciles these two methodologies and shows their similarities and differences using both real data and simulations. A new consistent correlated-errors-in-variables regression is introduced as the errors are shown to be correlated in the Bland-Altman plot. Indeed, the coverage probabilities collapse and the biases soar when this correlation is ignored. Novel tolerance intervals are compared with agreement intervals with or without replicated data, and novel predictive intervals are introduced to predict a single measure in an (X,Y) plot or in a Bland-Atman plot with excellent coverage probabilities. We conclude that the (correlated)-errors-in-variables regressions should not be avoided in method comparison studies, although the Bland-Altman approach is usually applied to avert their complexity. We argue that tolerance or predictive intervals are better alternatives than agreement intervals, and we provide guidelines for practitioners regarding method comparison studies. Copyright © 2016 John Wiley & Sons, Ltd. PMID:26822948

  17. Cenozoic geodynamic evolution of the western Mediterranean domain: A view from the Neogene peri-Tyrrhenian basins

    SciTech Connect

    Roure, F.; Montadert, L.; Mueller, C.

    1988-08-01

    Biostratigraphic and structural studies of synorogenic Neogene deposits in the southern Apennines, Calabria, and Cicily are compared to similar data from Sardinia and the Tyrrhenian Sea to trace the geodynamic evolution of the western Mediterranean domain.

  18. Southwestern Power Administration annual site environmental report CY 1997

    SciTech Connect

    1998-11-01

    This report provides a synopsis of Southwestern Power Administration`s (Southwestern`s) effectiveness in managing its operations in an environmentally responsible manner. In CY 1997, the Office of Environmental, Safety, and Health was reorganized and incorporated into the Division of Acquisition and Property. The Division of Acquisition, Property, and Environmental Management maintains responsibility for development, oversight, and implementation of environmental programs. Senior Management at Southwestern has taken actions to increase environmental awareness throughout the organization. During CY 1997, (Southwestern) was not involved in any known programs or activities that had adverse impacts on the environment. The 1997 Environmental Appraisal, a portion of Southwestern`s Self-Assessment and Appraisal Program, indicated approximately 90% compliance with Southwestern`s written environmental programs. Southwestern continued to function throughout CY 1997 in an operations and maintenance posture with minor substation projects.

  19. Effect of oceanographic and depositional events on Neogene benthic foraminiferal biostratigraphy of California

    SciTech Connect

    Blake, G.H.

    1986-05-01

    The relationships between Neogene environmental events and associated faunal distributional patterns of continental margin benthic foraminiferal faunas are affected or controlled by both local and regional events. These events are related to the complex evolution of the oceanic environment and the California continental margin. Evidence from Deep Sea Drilling Project sites drilled in the Pacific Ocean indicates that major changes in the oceanic environment have produced major faunal turnovers, migrations, and reorganizations of deep-sea benthic foraminiferal assemblages during the Neogene. DSDP Sites 467, 468, and 469, and the Naples Bluff section of southern California, the distributional patterns of continental margin benthic foraminiferal assemblages are strongly related to Neogene climatic-oceanic events. The faunal changes and responses described from the continental margin assemblages are similar in composition and timing to changes documented in the deep sea. The response of the benthic foraminiferal faunas is almost simultaneous across the continental margin in regard to the regional oceanic-climatic events. Several of these events were associated with changes in surface productivity and expansion of the oxygen minima. Local events involved the change in sedimentation and tectonic activity. The oceanic reorganization that occurred 15-13 Ma is responsible for a major change in the faunal patterns across the continental margin. Early Neogene faunas (the Saucesian, Relizian, and Luisian assemblages) were replaced by the Mohnian assemblage. The climatic-oceanic event at 9 to 8 Ma involved an increase in Antarctic glaciation and a resultant increase in upwelling and surface productivity. The associated faunal changes consist of a shift in the character of the Mohnian assemblage. At approximately 5.2 Ma, the Repettian assemblage increased considerably probably in relation to the Messinian event.

  20. Neogene tectonics and fault-related folds in the Gulf of Hammamet area, Tunisian offshore

    NASA Astrophysics Data System (ADS)

    Ben Brahim, Ghada; Ahmadi, Riadh; Brahim, Noureddine; Turki, Faiçal

    2014-09-01

    The western part of the Gulf of Hammamet area lies in the Pelagian Platform, eastward of the Atlas front. This region shows large changes in structural style compared to the Pelagian Platform. During the Neogene, the Gulf of Hammamet recorded the convergence of the Eurasia and Africa plates. During the Pliocene to early Quaternary, the area recorded an NW-SE shortening related to the Atlas contraction followed by an NNE-SSW extension linked to the Pantelleria-Malta graben opening. Subsurface geology of the Gulf of Hammamet area allows us to propose a tectonic sketch, where the Neogene deformation is characterized by (1) Cenozoic age detachment level that located in the Mio-Pliocene and Quaternary series; (2) the growth of fault-related folds (mainly fault-propagation folds) and (3) a total shortening of about 6 km. The thin-skinned thrusting is late Miocene age and is synchronous to the Africa-Europe collision. During the upper Miocene (Tortonian), fault-propagation folds developed above inherited normal faults. The Pliocene age was tectonically calm period. Finally, post-Villafranchian contraction reactivated these structures. Despite the large number of hydrocarbon discoveries, the Gulf of Hammamet remains under-explored. This new interpretation of Neogene tectonic events and folding models could lead to a new play idea for the hydrocarbon prospectively in this proven oil province.

  1. The intensification of the East Asian winter monsoon contributed to the disappearance of Cedrus (Pinaceae) in southwestern China

    NASA Astrophysics Data System (ADS)

    Su, Tao; Liu, Yu-Sheng (Christopher); Jacques, Frédéric M. B.; Huang, Yong-Jiang; Xing, Yao-Wu; Zhou, Zhe-Kun

    2013-09-01

    Climate change during the Quaternary played an important role in the distribution of extant plants. Herein, cone scales of Cedrus (Pinaceae) were uncovered from the Upper Pliocene Sanying Formation, Longmen Village, Yongping County of Yunnan Province in southwestern China. Detailed comparisons show that these fossils all belong to the genus Cedrus (Pinaceae), and a new species is proposed, Cedrus angusta sp. nov. This find expands the known distribution of Cedrus during the Late Pliocene to Yunnan, where the genus no longer exists in natural forests. Based on the analysis of reconstructed Neogene climate data, we suggest that the intensification of the East Asian winter monsoon during the Quaternary may have dramatically increased seasonality and given rise to a much drier winter in Yunnan. Combined with information on Cedrus fossil records and its seed physiology, we conclude that the intensification of a drier climate after the Late Pliocene may have prevented the survival of Cedrus seedlings, leading to the eventual disappearance of Cedrus in western Yunnan. This study indicates that the topography in southwestern China acted as a vital refuge for many plants during the Quaternary, but that other species gradually disappeared due to the intensification of the monsoonal climate.

  2. Southwestern Power Administration Annual Report 2010

    SciTech Connect

    2012-09-01

    Dear Secretary Chu: I am pleased to present the financial statements and operating data for Southwestern Power Administration (Southwestern) for Fiscal Year (FY) 2010. In FY 2010, Southwestern delivered nearly 7.6 billion kilowatt-hours of energy to its wholesale customers in Arkansas, Kansas, Louisiana, Missouri, Texas, and Oklahoma, generating $189 million in revenue. In fulfilling its mission to market and reliably deliver renewable Federal hydroelectric power, Southwestern maintains 1,380 miles of high-voltage transmission lines, substations, and communications sites, contributing to the reliability of the regional and National electric grid. Southwestern also actively partners with the Department of Energy, the U.S. Army Corps of Engineers, Southwestern’s customers, and other Federal power stakeholders to most effectively balance their diverse interests with Southwestern’s mission while continuing to maximize Federal assets to repay the Federal investment in the 24 hydropower facilities within Southwestern’s marketing region. Southwestern is proud of its past successes, and we look forward to continuing to serve the Nation’s energy needs in the future. Sincerely, Christopher M. Turner Administrator

  3. Southwestern Power Administration Annual Report 2012

    SciTech Connect

    2013-09-01

    Dear Secretary Moniz: I am pleased to present the financial statements and operating data for Southwestern Power Administration (Southwestern) for Fiscal Year (FY) 2012. In FY 2012, Southwestern delivered over 4.1 billion kilowatt-hours of energy to its wholesale customers in Arkansas, Kansas, Louisiana, Missouri, Oklahoma, and Texas, generating $195 million in revenue. In fulfilling its mission to market and reliably deliver renewable Federal hydroelectric power, Southwestern maintains 1,380 miles of high-voltage transmission lines, substations, and communications sites, contributing to the reliability of the regional and National electric grid. Southwestern also actively partners with the Department of Energy, the U.S. Army Corps of Engineers, Southwestern’s customers, and other Federal power stakeholders to most effectively balance their diverse interests with Southwestern’s mission while continuing to maximize Federal assets to repay the Federal investment in the 24 hydropower facilities within Southwestern’s marketing region. Southwestern is proud of its past successes, and we look forward to continuing to serve the Nation’s energy needs in the future. Sincerely, Christopher M. Turner Administrator

  4. Southwestern Power Administration Annual Report 2011

    SciTech Connect

    2013-04-01

    Dear Secretary Chu: I am pleased to present the financial statements and operating data for Southwestern Power Administration (Southwestern) for Fiscal Year (FY) 2011. In FY 2011, Southwestern delivered over 4.1 billion kilowatt-hours of energy to its wholesale customers in Arkansas, Kansas, Louisiana, Missouri, Oklahoma, and Texas, generating $167 million in revenue. In fulfilling its mission to market and reliably deliver renewable Federal hydroelectric power, Southwestern maintains 1,380 miles of high-voltage transmission lines, substations, and communications sites, contributing to the reliability of the regional and National electric grid. Southwestern also actively partners with the Department of Energy, the U.S. Army Corps of Engineers, Southwestern’s customers, and other Federal power stakeholders to most effectively balance their diverse interests with Southwestern’s mission while continuing to maximize Federal assets to repay the Federal investment in the 24 hydropower facilities within Southwestern’s marketing region. Southwestern is proud of its past successes, and we look forward to continuing to serve the Nation’s energy needs in the future. Sincerely, Christopher M. Turner Administrator

  5. Acoustic Velocity Of The Sediments Offshore Southwestern Taiwan

    NASA Astrophysics Data System (ADS)

    Tsai, C.; Liu, C.; Huang, P.

    2004-12-01

    Along the Manila Trench south of 21øXN, deep-sea sediments are being underthrusted beneath the Taiwan accretionary prism which is composed of the Kaoping Slope and Hengchun Ridge. Offshore southwestern Taiwan, foreland sediments and Late Miocene strata of the Tainan Basin are being accreted onto the fold-and thrust belt of the syn-collision accretionary wedge of the Kaoping Slope. The Kaoping Slope consists of thick Neogene to Recent siliciclastics deformed by fold-and-thrust structures and mud diapers. These Pliocene-Quaternary sediments deposited in the Kaoping Shelf and upper slope area are considered to be paleo-channel deposits confined by NNE-SSW trend mud diapiric structure. Seismic P-wave velocities of the sediment deposited in the Kaoping Shelf and Kaoping Slope area are derived from mutichannel seismic reflection data and wide-angle reflection and refraction profiles collected by sonobuoys. Sediment velocity structures constrained from mutichannel seismic reflection data using velocity spectrum analysis method and that derived from sonobuoy data using tau-sum inversion method are compared, and they both provide consistent velocity structures. Seismic velocities were analyzed along the seismic profile from the surface to maximum depths of about 2.0 km below the seafloor. Our model features a sediment layer1 with 400 ms in thickness and a sediment layer2 with 600 ms in thickness. For the shelf sediments, we observe a linear interval velocity trend of V=1.53+1.91T in layer1, and V=1.86+0.87T in layer2, where T is the one way travel time within the layer. For the slop sediment, the trend of V=1.47+1.93T in layer1, and V=1.70+1.55T in layer2. The layer1¡¦s velocities gradients are similar between the shelf (1.91 km/sec2) and the slope(1.93 km/sec2). It means layer1 distributes over the slope and shelf widely. The result of the sediment velocity gradients in this area are in good agreement with that reported for the south Atlantic continental margins.

  6. Midterm results of left coronary artery reimplantation through the transverse sinus of the pericardium in adult Bland-White-Garland syndrome.

    PubMed

    Kataoka, Go; Nakano, Kiyoharu; Asano, Ryota; Sato, Atsuhiko; Kodera, Kojiro; Tatsuishi, Wataru; Sudo, Shinji

    2015-12-01

    The anomalous origin of the left coronary artery from the pulmonary artery - known as Bland-White-Garland syndrome - is a rare congenital malformation that affects 1 in 300,000 live births. Most patients die in infancy without any surgical treatment. Some patients who survive past childhood often have varying symptoms such as myocardial ischemia, impaired left ventricular function, mitral regurgitation, and progressive heart failure, depending on the development collateral circulation. In the present report, we describe a procedure wherein the left coronary artery ostium was translocated through the transverse sinus of the pericardium in a 43-year-old mother with Bland-White-Garland syndrome and concomitant mitral regurgitation and report on the associated midterm results. PMID:26943392

  7. The Neogene of the Iceland Sea - Paleoenvironmental reconstructions using marine palynomorphs

    NASA Astrophysics Data System (ADS)

    Schreck, M.; Matthiessen, J.; Stein, R.

    2012-04-01

    ODP Hole 907A was drilled in the Iceland Sea as the mid-point of a paleoenvironmental transect across the Norwegian-Greenland Sea in order to investigate the response of the Arctic gateway region to the long-term global cooling that occurred after the Miocene Climate Optimum. However, owing to a generally low carbonate deposition/preservation and scarcity of calcareous microfossils in Neogene sediments of the Nordic Seas, the application of these traditionally used microfossils and deduced δ18O and Mg/Ca temperature proxies is strongly hampered. Hence, most previous studies have focussed on reconstructing the paleoceanographic and paleoclimatic history since the onset of large-scale Northern Hemisphere glaciations. On that account, the Miocene and parts of the Pliocene have been largely ignored and the Neogene paleoenvironmental history of the Nordic Seas still remains enigmatic. To bypass the absence of biogenic carbonates, organic-walled microfossils (e.g. dinoflagellate cysts, prasinophyte algae and acritarchs) are required for detailed paleoenvironmental reconstructions on pre-Quaternary timescales since they are continuously present and show relatively high abundance and diversity in the high northern latitudes hemipelagic sediments. ODP Hole 907A in the Iceland Sea, located close to the growing ice sheets, experienced the effects of sea-ice cover, migrating wind fronts and ocean currents, thus being a sensitive area with respect to global climate. In this context, Neogene climate deterioration and associated reorganisation of global ocean circulation must have led to alterations in the palynomorph association and may have affected turnover in species composition. Here we present a comparatively high-resolution palynomorph record from the almost continuous Middle Miocene to Late Pliocene sediment sequence of ODP Hole 907A in the Iceland Sea. Its pristine paleomagnetic record provides the unique opportunity for detailed investigations on how palynomorph

  8. Neogene Sequence Along the Eskişehir Fault Zone (EFZ), NW Turkey

    NASA Astrophysics Data System (ADS)

    Apaydın Poşluk, Elif; Koral, Hayrettin

    2015-04-01

    This study aims to explore the stratigraphy and structural features of Neogene units located in the Bozüyük (Bilecik) and Oklubalı (Eskişehir) area in southern Marmara, which lies on the collision zone between the Sakarya and Tauride-Anatolide blocks. Pre-Mesozoic marbles, schists and granodiorites, Mesozoic marbles, schists, ophiolitic units and limestones are basement rocks. Cover units include Neogene age formations. From the bottom to top, they are named the Porsuk Formation and the Akpınar Limestone, the İnönü Volcanics and the Ilıca Formation. Paleontological data which could yield a geological age have not been observed in fluvial sediments of the Porsuk Formation and lacustrine deposits of the Akpınar Limestone. The 40K/40Ar dating analyses on trachy-andesite of the overlying İnönü Volcanics have yielded middle Miocene ages (15.0-15.5 Ma), suggesting the underlying sedimentary units namely the Porsuk Formation and the Akpınar Limestone to be lower-middle Miocene in age. Fossils have been discovered in the lacustrine limestone of the Ilıca Formation in Oklubalı (İnönü-Eskişehir) village, and the age is determined to be lower Pliocene. The Eskişehir Fault Zone (EFZ) transects the Neogene formations and Quaternary sediments along an E-W'ly orientation. The Ormangüzle, Bozalan, Kandilli and İnönü Faults are segments observed from the west to east inside the Eskişehir Fault Zone. Some of these faults have NW-SE and others WNW-ESE orientations. The faults in NW-SE directions were effective for the formation of the Neogene sequence based on NE, SE and SW-oriented paleo-flow orientations and abrupt facies changes. The faults with WNW-ESE orientations, as noted in the Çukurhisar earthquake of February 2, 1956 (M=6.4), still keep their seismic activity and have a potential of producing earthquakes. Keywords: Neogene sediments, 40K/40Ar dating, the Eskişehir Fault Zone, active fault, Çukurhisar earthquake

  9. Crustal structure beneath Southwestern Mexico

    NASA Astrophysics Data System (ADS)

    Suhardja, S.; Grand, S.; Wilson, D.; Guzman Speziale, M.; Gomez Gonzalez, J.; Ni, J.; Dominguez Reyes, T.

    2007-12-01

    The MARS ( Mapping the Rivera Subduction zone ) project started in January 2006 deploying 50 broadband seismometers across southwestern Mexico for one and a half year duration. The stations were deployed in Jalisco, Michoacan and Colima states. The goal of the project is to understand the geometry of the Rivera and Cocos subducting plates and the effect of the subduction on the overriding plate. In this study, we employ the teleseismic receiver function technique to map out the lateral variation in Moho depth as well as the Vp/Vs ratio of the crust in this tectonically and magmatically active area. The ambiguity between the delay time of Ps and crustal Vp/Vs ratio is reduced by stacking later phases, the PpPs and PpSs + PsPs, for different values of Moho depth and Vp/Vs ratio (Zhu et al. ). An average crustal depth and crustal Vp/Vs ratio is obtained by finding the highest combination of parameters that give the largest amplitude stack. We find that the average Moho depth is 39 km but varies significantly from 25 to 45 km thick. The average crustal Vp/Vs ratio is 1.82 but is also variable ranging from 1.7 to 1.9. We will discuss correlations of crustal thickness and Vp/Vs ratio with crustal composition and magmatic activity.

  10. Neogene stratigraphy, foraminifera, diatoms, and depositional history of Maria Madre Island, Mexico: Evidence of early Neogene marine conditions in the southern Gulf of California

    USGS Publications Warehouse

    McCloy, C.; Ingle, J.C.; Barron, J.A.

    1988-01-01

    Foraminifera and diatoms have been analyzed from an upper Miocene through Pleistocene(?) sequence of marine sediments exposed on Maria Madre Island, largest of the Tre??s Marias Islands off the Pacific coast of Mexico. The Neogene stratigraphic sequence exposed on Maria Madre Island includes a mid-Miocene(?) non-marine and/or shallow marine sandstone unconformably overlain by a lower upper Miocene to uppermost Miocene upper to middle bathyal laminated and massive diatomite, mudstone, and siltstone unit. This unit is unconformably overlain by lower Pliocene middle to lower bathyal sandstones and siltstones which, in turn, are unconformably overlain by upper Pliocene through Pleistocene(?) upper bathyal to upper middle bathyal foraminiferal limestones and siltstones. These beds are unconformably capped by Pleistocene terrace deposits. Basement rocks on the island include Cretaceous granite and granodiorite, and Tertiary(?) andesites and rhyolites. The upper Miocene diatomaceous unit contains a low diversity foraminiferal fauna dominated by species of Bolivina indicating low oxygen conditions in the proto-Gulf Maria Madre basin. The diatomaceous unit grades into a mudstone that contains a latest Miocene upper to middle bathyal biofacies characterized by Baggina californica and Uvigerina hootsi along with displaced neritic taxa. An angular unconformity separates the upper Miocene middle bathyal sediments from overlying lower Pliocene siltstones and mudstones that contain a middle to lower bathyal biofacies and abundant planktonic species including Neogloboquadrina acostaensis and Pulleniatina primalis indicating an early Pliocene age. Significantly, this Pliocene unit contains common occurrences of benthic species restricted to Miocene sediments in California including Bulimina uvigerinaformis. Pliocene to Pleistocene(?) foraminiferal limestones and siltstones characterize submarine bank accumulations formed during uplift of the Tre??s Marias Island area, and include

  11. Northeastern Exterior, Northwestern Exterior, & Southwestern Exterior Elevations, Northeastern Interior, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Northeastern Exterior, Northwestern Exterior, & Southwestern Exterior Elevations, Northeastern Interior, Southeastern Interior, & Southwestern Interior Elevations, Floor Plan, and Eastern Corner Detail - Manatoc Reservation, Vale Edge Adirondack, 1075 Truxell Road, Peninsula, Summit County, OH

  12. Neogene transtensive faulting in the Rawil axial depression (SW Switzerland): preliminary results from field observations

    NASA Astrophysics Data System (ADS)

    Cardello, Giovanni Luca; Mancktelow, Neil

    2010-05-01

    The Helvetic nappe stack in the Rawil depression between the Aar and Mont Blanc massifs is affected by dominantly dextral transtensional faults developed or reactivated during the Neogene. This area shows the evolution of a fault system from partially ductile to brittle conditions and is currently one of the most seimogenically active zones in Switzerland. This field study aims to establish which fault sets have been activated during the Neogene and possibly Quaternary to Recent, to better constrain their relative age and kinematics, and to study the transition from ductile to brittle behaviour. The observed faults can be assigned to three general sets on the basis of their strike orientation. The first set (1) strikes NE-SW. Faults with distinctly different ages of initial activity are part of this set: Cretaceous normal faults with syn-sedimentary features; thrusts due to nappe-stacking; and later normal to oblique faults. All of these faults dip mainly to the SE. Paleo-tectonic features exposed in Plaine des Roses, les Audannes and Plaine Morte suggest that faults with this general orientation were already active during Cretaceous sedimentation. The post Aptian Cretaceous stratigraphic sequence is influenced by paleo-escarpments directly related to syn-sedimentary faults. These surfaces are marked in many places by karstification and silicification, sedimentary dykes and onlap of basinal younger formations. Some of these faults have been subsequently reactivated during Neogene syn- and post-collisional extension with normal to oblique kinematics. Transtensive reactivation of Cretaceous faults initially developed a ductile mylonitic fabric (expecially in limestones) that is overprinted by cataclasites and more discrete faults surfaces. Similarly oriented NE-striking veins were also developed under transitional brittle-ductile conditions in the limestones and, from relative age relationships, are the oldest veins developed in the area. The transtensive fault sets

  13. Cenozoic kinematic evolution of southwestern Central Iran: Strain partitioning and accommodation of Arabia-Eurasia convergence

    NASA Astrophysics Data System (ADS)

    Kargaranbafghi, Fariba; Neubauer, Franz; Genser, Johann

    2011-04-01

    The Yazd block of southwestern Central Iran is located in the back of the Zagros fold-thrust belt and monitors accommodation of Cenozoic shortening within the Arabia-Eurasia collision zone. The Saghand area within the Yazd block exposes a basin-and-range type morphology, which results from NE respectively E-W direction of shortening and a major tectonic change in structural trends within the southwestern Central Iranian block. The NNE-structural trend of various lithotectonic units including the Eocene Chapedony metamorphic core complex in the north is parallel to prominent Cenozoic NNE-trending Chapedony and Posht-e-Badam strike-slip faults. In the south the NNW-trending Anar, Kharanagh-Zarrin, Behabad and Kuhbanan faults are parallel to the Zagros fold-thrust belt and represent dextral strike-slip respectively NE-directed thrust faults, the thrust component representing a back-thrust component to the Zagros fold-thrust belt. Results of interpretation of satellite images, and structural and geomorphic field observations show a distributed deformation pattern covering a wide domain within southwestern Central Iran. Morphotectonic features like linear mountain ranges and intervening basins (kavirs) are interpreted to result from Neogene to Recent crustal-scale folding with uplifting mountain ranges and subsiding basins. Active thrust faults and evidence for block tilting are common on the eastern side of mountain blocks. Five distinct regional deformation phases respectively paleostress tensor groups have been recognized in the Central Iran from the major structures and through using paleostress inversion techniques for fault slip data. The first phase occurred in the Late Paleocene to Oligocene and is characterized by a subvertical σ1 and ca. N-S oriented σ3, which indicate N-S extension associated with late stages of normal faulting possibly due to post-orogenic collapse during exhumation of the Chapedony metamorphic complex. The second phase occurred from Late

  14. Geohistory analysis of Neogene Point Arena Basin, California: implications for its tectonic evolution

    SciTech Connect

    Loomis, K.B.; Ingle, J.C. Jr.

    1988-03-01

    The Neogene Point Arena basin of northwestern California is located west of the San Andreas fault system and south of the Mendocino triple junction. Key units of the Point Arena sequence are exposed from Iversen Landing north to Point Arena, California, including the Oligocene-Miocene Iversen Basalt (23.8 Ma), the lower Miocene Skooner Gulch and Gallaway Formations, and the lower to mid-Miocene Point Arena Formation. Lithologic and thickness data, together with evidence of age and paleobathymetry from both onshore and offshore sequences in the Point Arena basin, were used in a geohistory analysis of basin development. The resulting geohistory diagram tracks depths of specific stratigraphic zones, variations in paleobathymetry, and patterns of subsidence and uplift during late Paleogene through Neogene time. Geohistory analysis indicates that the late Paleogene margin was uplifted during approach of the Pacific-Farallon spreading ridge. Subsequently, a pulse of volcanism during latest Oligocene-Miocene signaled initial Neogene subsidence of the margin as marked by the Iversen Basalt. Subsidence likely involved both initial thermal subsidence as well as later transtensional deformation during the passage of the Mendocino triple junction and initiation of the San Andreas fault system. Rapid initial subsidence was accompanied by deposition of turbidites (Skooner Gulch and Gallaway Formation). The highly organic shales and petroliferous sands of the overlying Point Arena Formation indicate an abrupt cessation of turbidite deposition and a slower rate of basin subsidence during the middle Miocene. Episodes of warping from mid-Miocene through Holocene can be attributed to crustal flexing associated with wrench tectonism, with a major event bringing the Point Arena sequence above sea level during the late Pliocene-Pleistocene.

  15. Neogene tectono-stratigraphic events in Gulf of Suez rift area, Egypt

    SciTech Connect

    Evans, A.L.

    1987-05-01

    Micropaleontologic and sedimentologic studies of Miocene outcrop and borehole sections from the flanks and axial trough of the Suez rift have documented five major tectono-stratigraphic events, or hiatuses, during the Neogene. The first Neogene hiatus spans the late(.) Oligocene to earliest Miocene and separates Miocene from pre-Miocene strata throughout the Gulf of Suez. This erosional event resulted from both low global sea levels in the Oligocene and the initiation of Suez rifting. A second hiatus, from 21 to 19(.) Ma, separates the poorly dated shallow marine Nukhul formation from overlying middle Burdigalian and younger (NN3-NN5) upper bathyal shales of the Rudeis Formation. This hiatus resulted from both low early Burdigalian sea levels and increased rift-related tectonism. A third major event occurs within the Rudeis around 16 Ma (N7, NN4). This mid-Clysmic event of Garfunkel and Bartove is characterized by accelerated uplift of the rift margins and subsidence of the axial trough. Local unconformities are seen over paleohighs, while coarse clastics are deposited in more basinal areas in submarine fans and turbidites. A fourth hiatus at 14 to 13 Ma (N10-N11) separates the middle Miocene (N9) Kareem Formation from the overlying Belayim Formation evaporites. This hiatus may correlate with the initiation of rifting along the Dead Sea-Aqaba system. The fifth Neogene event is a tectonic pulse in the early (.) Pliocene that further rotated many tilted fault blocks. This event is roughly synchronous with the initiation of Red Sea sea-floor spreading and accelerated sinistral motion along the Dead Sea transform at approx. 5 Ma.

  16. Neogene and Quaternary geology of a stratigraphic test hole on Horn Island, Mississippi Sound

    USGS Publications Warehouse

    Gohn, Gregory S.; Brewster-Wingard, G. Lynn; Cronin, Thomas M.; Edwards, Lucy E.; Gibson, Thomas G.; Rubin, Meyer; Willard, Debra A.

    1996-01-01

    During April and May, 1991, the U.S. Geological Survey (USGS) drilled a 510-ft-deep, continuously cored, stratigraphic test hole on Horn Island, Mississippi Sound, as part of a field study of the Neogene and Quaternary geology of the Mississippi coastal area. The USGS drilled two new holes at the Horn Island site. The first hole was continuously cored to a depth of 510 ft; coring stopped at this depth due to mechanical problems. To facilitate geophysical logging, an unsampled second hole was drilled to a depth of 519 ft at the same location.

  17. Neogene vegetation and past climate change in the Thakkhola-Mustang Graben (central Nepal).

    NASA Astrophysics Data System (ADS)

    Adhikari, Basanta Raj; Wagreich, Michael; Draxler, Ilse; Paudayal, Khum N.

    2010-05-01

    The Thakkhola-Mustang Graben, which reflects Neogene extensional tectonics in the Tibetan Plateau and Himalaya, lies north of the Dhaulagiri-Annapurna ranges and south of the Yarlung-Tsangpo Suture Zone. The basement of Thakkhola-Mustang Graben is made up of Tibetan-Tethyan sedimentary rocks of Paleozoic and Mesozoic ages, which are unconformably overlain by continental debris (more than 850 m) of Neogene to Quaternary age. Stratigraphically, the Thakkhola-Mustang Graben sediments have been divided into five formations namely the Tetang Formation, the Thakkhola Formation, the Sammargaon Formation, the Marpha Formation and the Kaligandaki Formation. Different approaches have been made to study the Neogene sediments in this graben. In this study, we mainly focused on sedimentological and palynological studies of the Thakkhola-Mustang Graben, which provides a basis for discussing the paleo-environmental evolution of the southern continental margin of the Tibetan Plateau towards the end of the Miocene. Field mapping, profile logging, stable carbon and oxygen isotope analysis, and palynological studies were carried out to understand the depositional environment and the paleoclimate. The methodology developed by Zetter (1989) was followed for the pollen extraction. Pollen samples were processed in the laboratory and were studied under the light microscope (LM), which were later transferred to the scanning electron microscope (SEM). A variety of sedimentary environments are recognized including alluvial fan, lacustrine, braided river and glacio-fluvial. Neogene sediments are composed of braided fluvial deposits with lacustrine deposits in different level of the succession. Most of the pollens were found in the lacustrine layers of the Tetang and Thakkhola formations. Pollen analysis shows that the sediments contain dominant alpine trees like Abies, Pinus, Keteleeria, Picea Tsuga and Quercus with some steppe elements like Artemisia, Compositae, Chenopodiaceae, Plantago and

  18. Neogene marine climate trends: Implications for biogeography and evolution of the shallow-sea biota

    NASA Astrophysics Data System (ADS)

    Valentine, James W.

    1984-11-01

    A host of data on the biodistribution, diversity, and taxonomic age patterns of Neogene shallow-sea faunas can be accommodated within a climatic model which assumes that oceans in the late Paleogene were significantly cooler in low latitudes and wanner in high latitudes than at present. These climatic assumptions seem compatible with the state of the art in paleotemperature interpretation; if the model holds, it will effectively eliminate hypotheses of species diversity regulation that depend on the age of climates, and will explain the relative youth of genera and families in the tropics.

  19. Neogene-Quaternary tectonics along the North Caribbean transform fault, Cuba

    NASA Astrophysics Data System (ADS)

    Rojas-Agramonte, Y.; Neubauer, F.; Handler, R.; Garcia-Delgado, D. E.; Friedl, G.; Delgado-Damas, R.

    2003-04-01

    The Neogene to Recent North Caribbean (Oriente) Transform Fault (OTF) off the coast of southern Cuba is part of the northern Caribbean transform fault system. It has affected the southern Sierra Maestra mountain range, SE Cuba, and portrays the dynamics and tectonic evolution of the southern Cuban coast in the boundary zone between the Caribbean and North American plates. The region has been affected by historical earthquakes and shows many structures due to brittle deformation in Neogene to Pleistocene shallow-water limestones. Present-day structures vary along strike of the OTF, with dominant transpression in the east and transtension in the west. The focal mechanisms of historical earthquakes are in agreement with dominant ENE-WSW compression found onland. Neogene-Pleistocene limestones are deformed, faulted, fractured, and contains calcite- and karst-filled extension gashes. Type and orientation of the principal normal paleostresses vary along strike in accordance with observations of large-scale submarine structures at the southern Cuban continental margin. Deformation phase D1 comprises N-S extension, exemplified mainly by karst-filled extensional veins and normal faults. We correlate this deformation with the regional kinematics in the Caribbean realm, imposed by the opening of the Cayman trough and the disruption between Cuba and Hispaniola. D2 and D3 comprise NE-SW to nearly N-S and subsequent NW-SE-directed compression and generated conjugate Mohr shears that correlate with strike-slip movement along the main fault to the south. These phases are also associated with a transpressional tectonic regime in the submarine Santiago Deformed Belt and with deformation processes along the Oriente Deep, both located off the southern Cuban coast. D4 reflects ENE-WSW to E-W-directed compression and corresponds to reactivation of sinistral strike-slip faults and formation of Riedel shears, consistent with stress orientations deduced from earthquake focal mechanisms

  20. A pilot model for neogene and paleogene bivalve cenozones of the Northwestern Pacific

    NASA Astrophysics Data System (ADS)

    Kafanov, Alexander I.; Ogasawara, Kenshiro

    By means of taxonomically and geochronologically revised species lists (a total of 793 valid species of bivalve molluscs were considered) from 178 formations ('Suites') of Neogene and Paleogene deposits in the Russian Far East and characteristic and index species distinguished on this basis, the molluscan cenozones are established. These allow the construction of a preliminary stratigraphical scheme for the northwestern Pacific (western and eastern Kamchatka, south and north Sakhalin, Koryak 0Upland). The following cenozones are established: 1—extant species; 2— Fortipecten takahashii- Yoldia ( Cnesterium) kuluntunensis; 3— Acila ( Truncacila) marujamensis- Lucinoma acutilineata; 4— Mya cuneiformis- Acila ( Truncacila) gottschei; 5— Mytilus ( Tumidimytilus) tichanovitchi- Macoma osakaensis; 6— Megayoldia ( Hataiyoldia) tokunagai- Neilonella ( Borissia) sakhalinensis; 7— Periploma ( Aelga) besshoensis- Yoldia ( Yoldia) kovatschensis; 8— Papyridea ( Profulvia) harrimani- Ciliatocardium asagaiense; 9— Megayoldia ( Portlandella) watasei- Yoldia ( Nampiella) takaradaiensis; 10— Nuculana ( Saccella) gabbii- Corbula ( Cuneocorbula) formosa; 11— Lucina washingtonensis- Nuculana ( Saccella) alaeformis. On the basis of bivalve distribution patterns, it is assumed that the boundary between the Neogene and the Paleogene lies at the base of the Kuluven Horizon in western Kamchatka, the base of the lower Nevelisk sub-Horizon in south Sakhalin and at the lower part of the Pakhachin Horizon in eastern Kamchatka and Koryak Upland.

  1. Diatom biostratigraphy of chert intervals in Santa Maria and other Neogene basins, California

    SciTech Connect

    White, L.D.

    1988-03-01

    Chert is a common component of the Monterey Formation in many outer Neogene basins. Successful recovery of diatoms from dolomite beds and concretions, which are sufficiently abundant in chert-bearing sections, makes diatom biostratigraphic analyses possible in several poorly chronicled Neogene basins. At Ano Nuevo in the Outer Santa Cruz basin, where the section consists mainly of porcelanite and chert, diatom biostratigraphy yields an age duration from 14.7-13.4 Ma. Precise age control allows analysis of cyclical aspects of chert and dolomite to be carried out on the section. Frequency estimates of silica-carbonate cycles at Ano Nuevo suggest that the cycles may be related to early middle Miocene paleo-oceanographic events. In the Santa Maria basin, where black quartz cherts are widespread, diatom biostratigraphy has been successfully applied on the Mussel Rock, Lions Head, and Shell Beach sections. Preliminary data suggest black chert intervals are strongly age controlled and are possibly related to Miocene cooling events that affected the Santa Maria basin. Ongoing studies of the diatom biostratigraphy of dolomites promise improved age control in the Santa Maria basin. This will not only aid in paleo-oceanographic interpretations, but will also improve constraints on tectonic and depositional aspects of the basin.

  2. Tectonic Evolution of the Çayirhan Neogene Basin (Ankara), Central Turkey

    NASA Astrophysics Data System (ADS)

    Behzad, Bezhan; Koral, Hayrettin; İşb&idot; l, Duygu; Karaaǧa; ç, Serdal

    2016-04-01

    Çayırhan (Ankara) is located at crossroads of the Western Anatolian extensional region, analogous to the Basin and Range Province, and suture zone of the Neotethys-Ocean, which is locus of the North Anatolian Transform since the Late Miocene. To the north of Çayırhan (Ankara), a Neogene sedimentary basin comprises Lower-Middle Miocene and Upper Miocene age formations, characterized by swamp, fluvial and lacustrine settings respectively. This sequence is folded and transected by neotectonic faults. The Sekli thrust fault is older than the Lower-Middle Miocene age formations. The Davutoǧlan fault is younger than the Lower-Middle Miocene formations and is contemporaneous to the Upper Miocene formation. The Çatalkaya fault is younger than the Upper Miocene formation. The sedimentary and tectonic features provide information on mode, timing and evolution of this Neogene age sedimentary basin in Central Turkey. It is concluded that the region underwent a period of uplift and erosion under the influence of contractional tectonics prior to the Early-Middle Miocene, before becoming a semi-closed basin under influence of transtensional tectonics during the Early-Middle Miocene and under influence of predominantly extensional tectonics during the post-Late Miocene times. Keywords: Tectonics, Extension, Transtension, Stratigraphy, Neotectonic features.

  3. A Neogene calcareous nannofossil biozonation scheme for the deep offshore Niger Delta

    NASA Astrophysics Data System (ADS)

    Fadiya, Lawrence Suyi; Salami, Babajide Moshood

    2015-12-01

    A detailed calcareous nannofossil analysis was carried out on the deep-water offshore Niger Delta strata penetrated by eight wells in order to erect a basin-wide Neogene biozonation scheme for the region. Four of the wells penetrated Miocene to Early Pliocene strata while the others drilled through Miocene sediments. The recorded rich and diversified nannofossil suites enabled the subdivision of the Neogene sequences into 13 zones [NN1 (CN1a) - Early Miocene to NN13 (CN10c) - Early Pliocene] and 15 subzones. Five (NN1, NN2, NN4, NN5 and NN11) zones are divided into subzones based on First and Last occurrences plus relative abundance of marker species. Dearth of nannofossils in the Middle Miocene NN5-NN8 zones precludes a refined zonation construction for the interval. Several new criteria are suggested for delineating new and previously erected zones. The resulting refined scheme offers an improved stratigraphic framework for correlation of thin reservoir units within and across Niger Delta fields.

  4. Anatomy of a river drainage reversal in the Neogene Kivu Nile Rift

    NASA Astrophysics Data System (ADS)

    Holzförster, F.; Schmidt, U.

    2007-07-01

    The Neogene geological history of East Africa is characterised by the doming and extension in the course of development of the East African Rift System with its eastern and western branches. In the centre of the Western Rift Rise Rwanda is situated on Proterozoic basement rocks exposed in the strongly uplifted eastern rift shoulder of the Kivu-Nile Rift segment, where clastic sedimentation is largely restricted to the rift axis itself. A small, volcanically and tectonically controlled depository in northwestern Rwanda preserved the only Neogene sediments known from the extremely uplifted rift shoulder. Those (?)Pliocene to Pleistocene/Holocene fluvio-lacustrine muds and sands of the Palaeo-Nyabarongo River record the influence of Virunga volcanism on the major drainage reversal that affected East Africa in the Plio-/Pleistocene, when the originally rift-parallel upper Nile drainage system became diverted to the East in order to enter the Nile system via Lake Victoria. Sedimentary facies development, heavy mineral distributions and palaeobiological controls, including hominid artefacts, signal a short time interval of <300-350 ka to complete this major event for the sediment supply system of the Kivu-Nile Rift segment.

  5. Structure of a turbiditic system in Neogene of Guadalquivir basin (south Spain)

    SciTech Connect

    Suarez, J.; Martinez, W.; Serrano, A.; Leret, G. )

    1988-08-01

    The Guadalquivir basin constitutes the foreland basin for the Betic Ranges, filled with Neogene marine sediments in which turbidites have been identified. This basin presents a half-graben configuration: a northern passive margin formed by a flexure of the Hercynian basement and a southern active border, an olistostrome that slid northward from the Betics during the Neogene. Turbidites are confined to a narrow area between a nonsedimentation, or bypass, zone and the olistostrome. The interpretation of the seismic morphologies related to the top of the sand bodies allowed them to identify a sequence of seismofacies: channels, leveed channels, and lobes. The internal structure of each turbiditic sand body shows a gentle downlap to the west and an onlap to the north, interpreted as a progradation and an aggradation, respectively. Six different sand bodies can be individualized by erosive scars, lying one beside the other. The whole turbiditic system exhibits, instead of the classical vertical stacking, an extreme lateral juxtaposition bias with a westward progradation. The younger bodies lie to the north and west of the older ones. Juxtaposition is generated by lateral shifting to the only available area where deposition can progress: the northern bypass zone and the western frontal part of the former body. Neither a morphological paleotalus nor a preferential sediment supply zone has been observed. Field studies show these sediments to be high-energy deposits transported by turbiditic currents and grain-flow mechanisms related to low-efficiency systems.

  6. Neogene-holocene mixed carbonate-siliciclastic deposition in eastern Gulf of Mexico with earlier analogs

    SciTech Connect

    Doyle, L.J.; Locker, S.D.

    1988-01-01

    The Neogene to Holocene history of the eastern Gulf of Mexico reveals a complex interplay between carbonate and siliciclastic sedimentation that may help interpret and explain many ancient deposits. Well data from the Florida Panhandle have been correlated with over 1,900 mi of high-resolution seismic reflection profiles collected on a 2-mi grid as part of a major geophysical program sponsored by GECO Geophysical Company, Inc. Data show a shift from flat carbonate sequences to prograding sequences about a major Neogene unconformity. Below that unconformity, carbonate sedimentation was dominant; afterward sediments became progressively more siliciclastic, grading into the Apalachicola delta and a surficial quartz sand sheet. The quartz sand grades laterally into the west Florida carbonate margin, bounded on the east by fine quartz sand beaches and terrace deposits of the Florida peninsula and on the west by the massive siliciclastic Mississippi fan. Siliciclastic sediments must have advanced and retreated across the carbonate shelf with sea level rise and fall. DSDP Leg 9 cores and seismic profiles suggest that, periodically, portions of the west Florida and probably Yucatan margins have failed, injecting massive carbonate gravity deposits into the deep Gulf of Mexico. These deposits have become intercalated into the Mississippi fan. Examples of quartz sandfilled channels in carbonate rocks and carbonate gravity deposits within siliciclastic (e.g., south Pyrenean basin and some deposits of the Permian basin) are found in the ancient record where they provide excellent isochronous marker beds as well as good potential reservoirs for hydrocarbons.

  7. Variations in the strontium isotopic composition of seawater during the Neogene

    SciTech Connect

    Hodell, D.A.; Mueller, P.A.; Garrido, J.R. )

    1991-01-01

    The authors report 261 strontium isotopic analyses of well-preserved planktonic foraminifers from three Deep Sea Drilling Project Sites (519, 588, and 607). These samples cover the period from 24 Ma to present with an average of approximately one sample per 100 ka. The combination of high sample density and uniformity of analytical procedures has produced a well-defined record of changes in the {sup 87}Sr/{sup 86}Sr of seawater during the Neogene. The record can be viewed as a series of essentially linear segments with slopes ranging from as high as 6{times}10{sup {minus}5}/m.y. to as low as 0/m.y. The times associated with major inflections in the curve do not appear to correspond to simple geologic phenomena such as eustatic cycles, but are probably controlled by a combination of tectonic and climatic factors that influenced the abundance and isotopic composition of terrestrial strontium input to the oceans. The strontium isotopic data are consistent with a progressive increase in the chemical weathering rates of the continents during the Neogene, probably related to repeated glaciations, increased exposure of continents by lowered sea level, and increased continental relief resulting from high rates of tectonic uplift.

  8. Stratigraphic record of the Yellowstone hotspot track, Neogene Sixmile Creek Formation grabens, southwest Montana

    NASA Astrophysics Data System (ADS)

    Sears, James W.; Hendrix, Marc S.; Thomas, Robert C.; Fritz, William J.

    2009-11-01

    The Sixmile Creek Formation fills deep grabens in southwest Montana and preserves a stratigraphic record of the evolution of the Yellowstone hotspot track from ~ 17 Ma to ~ 2 Ma. The Ruby, Beaverhead, Big Hole, Deer Lodge, Medicine Lodge-Grasshopper, Three Forks, Canyon Ferry, Jefferson, Melrose, Wise River, and Paradise grabens were active during outbreak of the hotspot. They appear to be parts of a radial system of extensional structures that may have formed on a broad dome that was centered on the hotspot outbreak area in southwest Idaho and southeast Oregon. Early in the evolution of the grabens, massive debris flows surged down Paleogene paleovalleys from uplifted and tilted horst blocks and accumulated in the grabens. The grabens captured runoff from the hotspot dome with thick deposits of river gravel that appear to have been derived, in part, from east-central Idaho. As the hotspot track propagated along the eastern Snake River Plain, silicic ash fell into the graben drainage basins and was reworked into thick fluvial beds along graben axes. The grabens were cross-cut by northwest-trending late Neogene grabens that propagated on the flanks of silicic volcanic centers along the hotspot track. The late Neogene grabens diverted the Middle Miocene drainage patterns in southwest Montana.

  9. Neogene-Eopleistocene shelly limestones in the North Caucasus and Ciscaucasia regions

    NASA Astrophysics Data System (ADS)

    Beluzhenko, E. V.

    2014-07-01

    In the North Caucasus and Ciscaucasia, seven distribution zones of Middle-Upper Miocene, Pliocene, and Eopleistocene shell-detrital limestones are defined: Lower Don, Tsimlyansk-Manych, Western Ciscaucasia, Western Caucasus, Central Ciscaucasia, Kabarda-Chechen, and Eastern Dagestan. The shell-detrital limestones are present among sandy-clayey sediments in the form of intercalations of variable thickness traceable over different distances (up to a few kilometers). The maximum thicknesses of such limestones are characteristic of the Neogene sections in the northwestern pericline of the Greater Caucasus: Taman-Adagum area, where their distribution comprises the stratigraphic interval from the Chokrakian to early Cimmerian regional stages (approximately 10 m.y. long). Their most spacious distribution area is confined to the Central Ciscaucasia zone. The shell-detrital limestones in the Neogene sections mark shallowwater shelf areas (ancient coastal bars, banks, and shoals) with intermittently forming environments favorable for accumulation of significant volumes of shelly detritus. In such paleogeographic settings, the sediments were subjected to repeated erosion with subsequent formation of limestones. Now, they represent building material widely used in the region for different purposes.

  10. Variations in the strontium isotopic composition of seawater during the Neogene

    NASA Astrophysics Data System (ADS)

    Hodell, David A.; Mueller, Paul A.; Garrido, Jose R.

    1991-01-01

    We report 261 strontium isotopic analyses of well-preserved planktonic foraminifers from three Deep Sea Drilling Project Sites (519, 588, and 607). These samples cover the period from 24 Ma to present with an average of approximately one sample per 100 ka. The combination of high sample density and uniformity of analytical procedures has produced a well-defined record of changes in the 87Sr/86Sr of seawater during the Neogene. The record can be viewed as a series of essentially linear segments with slopes ranging from as high as 6 x 10-5/m.y. to as low as 0/m.y. The times associated with major inflections in the curve do not appear to correspond to simple geologic phenomena such as eustatic cycles, but are probably controlled by a combination of tectonic and climatic factors that influenced the abundance and isotopic composition of terrestrial strontium input to the oceans. The strontium isotopic data are consistent with a progressive increase in the chemical weathering rates of the continents during the Neogene, probably related to repeated glaciations, increased exposure of continents by lowered sea level, and increased continental relief resulting from high rates of tectonic uplift.

  11. The Neogene equatorial Pacific: A view from 2009 IODP drilling on Expedition 320/321. (Invited)

    NASA Astrophysics Data System (ADS)

    Lyle, M. W.; Shackford, J.; Holbourn, A. E.; Tian, J.; Raffi, I.; Pälike, H.; Nishi, H.

    2013-12-01

    The equatorial Pacific responds strongly to global climate and is a source of ENSO, the largest global decadal climate oscillation. Equatorial Pacific circulation and upwelling result from global atmospheric circulation patterns so it is unsurprising that oceanographic changes in the equatorial Pacific reverberate globally. IODP expedition 320/321 (Pacific Equatorial Age Transect) drilled 8 sites to reconstruct a 50-million-year record of ocean change for the equatorial Pacific. The resulting record, when spliced together, will resolve orbital variations through most of the Cenozoic. All sedimentary sequences have now been scanned by XRF, so that biogeochemical changes through the Cenozoic can be studied. Here we report data from IODP Sites U1335, U1336, U1337, and U1338, the Neogene part of the PEAT megasplice. Sediments of the Neogene equatorial Pacific are primarily biogenic carbonates, with about 15% biogenic silica tests and 5% assorted other components, including clays. Typically, highest sediment deposition occurs when plate tectonic movement carries a drill site underneath the equatorial zone, indicating that equatorial upwelling and high productivity have been consistent features of the Neogene equatorial Pacific. Sedimentation rates become significantly slower and dissolution of both biogenic carbonates and silica are more pronounced when sites are beyond 3° in latitude away from the equator, as biogenic sediment production drops but dissolution does not. The differences between equatorial and off-equator sites allow assessment of productivity vs dissolution as drivers of the sediment record. Carbonate dissolution can also be assessed by a ratio of XRF-estimated carbonate to dissolution resistant biogenic residue, like barite. There is a common stratigraphy of carbonate variation in the Neogene equatorial Pacific, as proposed by earlier work from DSDP Leg 85 and ODP Leg 138. The new Exp 320/321 drilling extends the high-resolution record from ~0-5 Ma

  12. The Neogene Ogallala Formation in Southwestern Kansas and Northeastern New Mexico: Preliminary Magnetostratigraphic Analyses for the High Plains-Ogallala Drilling Program

    NASA Astrophysics Data System (ADS)

    Zeigler, K. E.; Petronis, M. S.; Smith, J. J.; Ludvigson, G. A.; Doveton, J.

    2012-12-01

    A better understanding of the Ogallala Formation is critical in terms of refining groundwater flow models and management policies for communities relying on aquifers in heterolithic sequences around the globe. The High Plains aquifer remains under increasing stress with the growth of both urban and agricultural areas and therefore, developing the best groundwater management policies will depend on the most accurate characterization of the aquifer, the aquifer materials and their stratigraphic and geochronologic framework. Although mammalian faunal assemblages and volcanic ash bed tephrochronology provide a basic geochronologic framework for the Ogallala Formation, better precision in terms of correlation is needed in order to understand formative processes and depositional histories for the primary water-bearing units in the High Plains aquifer and confining strata. The High Plains-Ogallala Drilling Program (HPODP) was developed to advance understanding of sedimentary facies, stratigraphic framework, and chronostratigraphy of the Ogallala Formation and overlying units that comprise the central High Plains aquifer. The drilling program began in the early summer of 2011 in Haskell Co., western Kansas. By early fall 2011; the drill crew was at 92 m with about 32 m to go until they expect to hit bedrock. The final 32 meters of core was extracted during the summer 2012. Here we report the preliminary magnetostratigraphic and rock magnetic data from the first section of core. We scanned the entire 92 meters of core using an ASC Core Analysis System with a Bartington Instruments MS2C magnetic susceptibility coil allowing for bulk susceptibility measurements to be obtained along the length of the core. In addition, we collected 40 sub samples for paleomagnetic and rock magnetic. Bulk susceptibility data reveal depth dependent changes in rock magnetic properties that we interpret to reflect either climatic driven variations impacting the depositional system or a change in provenance of the sediments. Bulk susceptibility of the sediments decreases by an order of magnitude from the surface to the base of the measured core suggesting a change in detrital magnetic influx. Curie point estimates indicate that the dominant magnetic mineral in all samples is cubic, titanomagnetite phase of variable composition; whether a systemic change with depth exist is as of yet to be revealed. Preliminary paleomagnetic data are encouraging with many sub samples yielding a single component magnetization that decays near univectorally to the origin during both alternating field and thermal demagnetization.

  13. Fossil proxies of near-shore sea surface temperatures and seasonality from the late Neogene Antarctic shelf

    NASA Astrophysics Data System (ADS)

    Clark, Nicola A.; Williams, Mark; Hill, Daniel J.; Quilty, Patrick G.; Smellie, John L.; Zalasiewicz, Jan; Leng, Melanie J.; Ellis, Michael A.

    2013-08-01

    We evaluate the available palaeontological and geochemical proxy data from bivalves, bryozoans, silicoflagellates, diatoms and cetaceans for sea surface temperature (SST) regimes around the nearshore Antarctic coast during the late Neogene. These fossils can be found in a number of shallow marine sedimentary settings from three regions of the Antarctic continent, the northern Antarctic Peninsula, the Prydz Bay region and the western Ross Sea. Many of the proxies suggest maximum spring-summer SSTs that are warmer than present by up to 5 °C, which would result in reduced seasonal sea ice. The evidence suggests that the summers on the Antarctic shelf during the late Neogene experienced most of the warming, while winter SSTs were little changed from present. Feedbacks from changes in summer sea ice cover may have driven much of the late Neogene ocean warming seen in stratigraphic records. Synthesized late Neogene and earliest Quaternary Antarctic shelf proxy data are compared to the multi-model SST estimates of the Pliocene Model Intercomparison Project (PlioMIP) Experiment 2. Despite the fragmentary geographical and temporal context for the SST data, comparisons between the SST warming in each of the three regions represented in the marine palaeontological record of the Antarctic shelf and the PlioMIP climate simulations show a good concordance.

  14. Fossil proxies of near-shore sea surface temperatures and seasonality from the late Neogene Antarctic shelf.

    PubMed

    Clark, Nicola A; Williams, Mark; Hill, Daniel J; Quilty, Patrick G; Smellie, John L; Zalasiewicz, Jan; Leng, Melanie J; Ellis, Michael A

    2013-08-01

    We evaluate the available palaeontological and geochemical proxy data from bivalves, bryozoans, silicoflagellates, diatoms and cetaceans for sea surface temperature (SST) regimes around the nearshore Antarctic coast during the late Neogene. These fossils can be found in a number of shallow marine sedimentary settings from three regions of the Antarctic continent, the northern Antarctic Peninsula, the Prydz Bay region and the western Ross Sea. Many of the proxies suggest maximum spring-summer SSTs that are warmer than present by up to 5 °C, which would result in reduced seasonal sea ice. The evidence suggests that the summers on the Antarctic shelf during the late Neogene experienced most of the warming, while winter SSTs were little changed from present. Feedbacks from changes in summer sea ice cover may have driven much of the late Neogene ocean warming seen in stratigraphic records. Synthesized late Neogene and earliest Quaternary Antarctic shelf proxy data are compared to the multi-model SST estimates of the Pliocene Model Intercomparison Project (PlioMIP) Experiment 2. Despite the fragmentary geographical and temporal context for the SST data, comparisons between the SST warming in each of the three regions represented in the marine palaeontological record of the Antarctic shelf and the PlioMIP climate simulations show a good concordance. PMID:23828612

  15. The geochemical signature of Neogene Eastern Mediterranean sediment: evidence for temporal and spatial variations in provenance

    NASA Astrophysics Data System (ADS)

    Klaver, Martijn; Vroon, Pieter; Wijbrans, Jan

    2014-05-01

    Subducted sediment is one of the main geochemical components in arc magmas. Although an east-west gradient in Eastern Mediterranean Sea (EMS) sediment composition has been evoked to explain the along-arc geochemical variations in Aegean arc magmas [1], solid evidence for E-W changes in EMS sediment composition is lacking. The EMS sediment dataset is limited to Holocene samples, while the sediment currently underneath the volcanic arc has an age of at least 6 Ma. In order to characterise EMS sediment, we have used a combination of thermogravimetric and geochemical analyses of 45 Neogene DSDP and ODP drill core samples. Thermogravimetric dissociation curves provide a rapid way to determine carbonate-content and relative abundance of clay mineral groups in mixed sediment samples. Clear clay mineral distribution patterns are observed in the EMS: smectite is dominant in Nile sediment, aeolian dust consist mainly of kaolinite while illite is present in coarser (shelf) sediment. Four distinct provenance areas can be recognised on the basis of radiogenic isotope and trace element ratios of the EMS sediment samples. In line with previous studies [e.g. 2], we conclude that Sahara dust and Nile sediment are main constituents of EMS sediment. However, we recognize two additional source areas. Sediment derived from Cyprus and/or SW Turkey, characterised by high Ni/Nb ratios, is an important component in Quaternary EMS sediment. Sediment from the Aegean region has an arc signature (e.g. high La/Nb) and is distinguishable only in the Hellenic Trench. During the Neogene, an increase in aeolian dust input to the EMS is observed, which is consistent with the progressive aridification of the Sahara region. The geochemical characterisation of Neogene EMS sediment and the recognition of distinct provenance areas can be used to assess the contribution of subducted sediment to magmas in the Aeolian and Aegean volcanic arcs. In addition, it allows further high-resolution investigation of

  16. Neogene north American-Caribbean plate boundary across Northern Central America: Offset along the polochic fault

    NASA Astrophysics Data System (ADS)

    Burkart, Burke

    1983-12-01

    The Polochic fault was a segment of the North American-Caribbean plate boundary across Central America in the Neogene. Its 130 km of left slip was previously determined by matching structures and stratigraphie outcrop patterns of northwest and central Guatemala across the fault. Additional support for the model and the youthfulness of the recorded offset comes from an essentially perfect match of major geomorphic features across the fault. A reconstruction process which eliminates 123 km of left slip brings together rivers and drainage divides that existed before the Polochic became active. With the reconstruction carried across the isthmus on an east-west fault the regional structural geology assumes the coherent pattern of a continuous orogenic belt whose geometry is compatible with the model of collisional tectonics centered on the Motagua "suture zone". Confined within this belt, narrowed to some 60 km by the reconstruction, lie the major Laramide thrusts, folds and tectonically emplaced serpentinites of Guatemala. Crystalline rocks of Guatemala re-join the Chiapas Massif and Paleozoic sedimentary rocks, exposed in the core of an almost-continuous anticlinorium, extend from southern Chiapas to Lake Izabal. The Polochic does not bend in eastern Guatemala but continues eastward to the Motagua fault where it dies. Westward drift of the northern block resulted in rifting which extended from eastern Guatemala into the Caribbean along the Cayman trough. The Honduras depression may represent an element of a triple junction along with the Polochic and Izabal-Cayman rift. The Polochic continues westward into the Pacific Ocean and offsets the Middle America trench. The Polochic has offset the Miocene volcanic belt of northern Central America, confirming the previous estimate of a Neogene time of movement. About 300 km of relative east-west Neogene displacement has been recorded on the Mid-Cayman rise, only 130 km of which can be accounted for across the Polochic. It is

  17. Link between Neogene and modern sedimentary environments in the Zagros foreland basin

    NASA Astrophysics Data System (ADS)

    Pirouz, Mortaza; Simpson, Guy; Bahroudi, Abbas

    2010-05-01

    The Zagros mountain belt, with a length of 1800 km, is located in the south of Iran and was produced by collision between the Arabian plate and the Iran micro plate some time in the early Tertiary. After collision, the Zagros carbonate-dominated sedimentary basin has been replaced by a largely clastic system. The Neogene Zagros foreland basin comprises four main depositional environments which reflect the progressive southward migration of the deformation front with time. The oldest unit - the Gachsaran formation - is clastic in the northern part of the basin, but is dominated by evaporates in southern part, being deposited in a supratidal Sabkha-type environment. Overlying the Gachsaran is the Mishan formation, which is characterized by the Guri limestone member at the base, overlain by marine green marls. The thickness of the Guri member increases dramatically towards the southeast. The next youngest unit is the Aghajari Formation which consists of well sorted lenticular sandstone bodies in a red silty-mudstone. This formation is interpreted as representing the floodplain of dominantly meandering rivers. Finally, the Bakhtiari formation consists of mainly coarse-grained gravel sheets which are interpreted to represent braided river deposits. Each of these Neogene depositional environments has a modern day equivalent. For example, the braided rivers presently active in the Zagros mountains are modern analogues of the Bakhtiari. In the downstream direction, these braided rivers become meandering systems, which are equivalents of the Aghajari. Eventually, the meandering rivers meet the Persian gulf which is the site of the ‘modern day' Mishan shallow marine marls. Finally, the modern carbonate system on the southern margin of Persian Gulf represents the Guri member paleo-environment, behind which Sabkha-type deposits similar to the Gachsaran are presently being deposited. One important implication of this link between the Neogene foreland basin deposits and the

  18. Southwestern Power Administration Annual Report 2008

    SciTech Connect

    2010-12-01

    Dear Secretary Chu, I am pleased to present the financial statements and operating data for Southwestern Power Administration (Southwestern) for Fiscal Year (FY) 2008. In FY 2008, Southwestern delivered over 7.3 billion kilowatt-hours of energy to its wholesale customers – nearly 31% more than average due to numerous record rainfall amounts in the southwest region. These record amounts produced revenues which exceeded the average annual revenue requirement by nearly $20 million and resulted in over $200 million in economic benefits to the region. Yet even as Southwestern exceeded its goals of marketing and delivering Federal hydroelectric power to our customers, we stayed focused on safety, security, and reliability. For example, we maintained our nearly 1,400 miles of high-voltage transmission lines, substations, and communications sites while achieving a Recordable Accident Frequency Rate of 0.0, a record that reflects Southwestern’s safety achievement of no recordable injuries for every 200,000 hours worked. We kept our rights-of-way secure from vegetation and other obstacles, work that not only supports our mission but also promotes reliability of the regional and National grid. We exceeded all North American Electric Reliability Corporation (NERC) Control Performance Standards (CPS- 1 and CPS-2), and maintained regulation and reserve obligations and reactive reserve margins to ensure the reliability of the bulk electric system, even during extended periods of restricted hydro operations due to unusually high project inflows. Finally, we continued our partnerships with the Department of Energy, the U.S. Army Corps of Engineers, our customers, and other Federal power stakeholders, partnerships that are vital to our continued success in marketing and delivering carbon-free, renewable, and domestically produced energy to our customers and to the Nation. Sincerely, Jon Worthington Administrator

  19. Freshwater gastropods of Neogene and Quaternary lake systems of Europe - state of the art and outlook

    NASA Astrophysics Data System (ADS)

    Neubauer, Thomas A.; Harzhauser, Mathias; Mandic, Oleg; Kroh, Andreas

    2013-04-01

    Globally, about 4000 extant species of freshwater gastropod species have been described. In contrast, only 225 species are listed by MollBase2012 for North- and Central Europe. Many of these are rare species, limited to certain springs and in fact the typical diversity of gastropods in lakes of North and Central Europe is much lower. The high number is boosted by several highly speciose endemic radiations in long-lived ancient lakes, which are hotspots for biodiversity. These long-lived ancient lakes provide key examples for understanding evolutionary processes and therefore are intensively studied. During the Neogene, Europe's geodynamic history gave rise to several such long-lived lakes with conspicuous endemic radiations. However, these lacustrine systems are rare today as well as in the past compared to the enormous numbers of "normal" lakes. Most extant European lakes are mainly results of the Ice Ages and are due to their geologically temporary nature largely confined to the Pleistocene-Holocene. Also deposits of streams, springs, and groundwater, which today are inhabited by species-rich gastropod assemblages, are rarely preserved. Thus, the pre-Quaternary lacustrine record is biased towards long-lived systems. Apart from few general overviews precise studies on the γ-diversities of the post-Oligocene European lake systems and the shifting biodiversity in European freshwater systems through space and time are entirely missing. Even for the modern faunas, literature on large-scale freshwater gastropod diversity in extant lakes is scarce and lacks a statistical approach. Building upon a great amount of existing literature, a new project will provide the first detailed assessment of the composition of European freshwater gastropods during the Neogene and Quaternary at species, genus and family levels, with emphasis on lake faunas. The γ-diversity of several hundred modern and fossil European lakes will be evaluated. Data will be made available permanently for

  20. Implications of outcrop geology for reservoirs in the Neogene productive series: Apsheron peninsula, Azerbaijan

    SciTech Connect

    Reynolds, A.D.; Bowman, M.B.J.; Henton, J.

    1998-01-01

    The Neogene sediments of eastern Azerbaijan and western Turkmenistan contain significant hydrocarbon reserves in deltaic reservoirs. Sedimentary logging of these reservoirs at outcrop in Azerbaijan has outlined four facies associations that encompass a range of paleoenvironments, from alluvial braided river sandstones and conglomerates to delta-front siltstones and mudstones. The facies associations suggest a river-dominated braid delta and are arranged into an architecture controlled by base-level changes: parasequences, parasequence sets, and sequence boundaries are key elements. The facies associations and stratigraphic architecture, together with outcrop observations of cementation and faulting, are summarized in terms of four idealized reservoir models: fluvial, delta plain, proximal delta front, and distal delta front. Each reservoir model has distinctive grain-size and shale distributions. Comparison of nearby oil fields with the studied outcrops suggests that the outcrops form good analogs from which to model reservoir architecture, barriers and baffles to fluid flow, reservoir heterogeneity, and reservoir quality variations.

  1. Synopsis of valid species-group taxa for freshwater Gastropoda recorded from the European Neogene

    PubMed Central

    Neubauer, Thomas A.; Kroh, Andreas; Harzhauser, Mathias; Georgopoulou, Elisavet; Mandic, Oleg

    2014-01-01

    Abstract Here we present a complete list of all valid species-group taxa of freshwater gastropods reported from Miocene and Pliocene deposits in Europe. The last comparable work dates back to the 1920s and covered about 1,600 names. The extensive literature research underlying the present work revealed considerable changes in the taxonomic and systematic frameworks of Neogene freshwater gastropods and yielded a total number of 2,156 accepted taxa. Each taxon is accompanied by a full citation of its first description; where the information is available, page number and illustration reference are provided. First descriptions available as open-access full-text sources on the web were linked via hyperlink to the first page of the publication. PMID:25152683

  2. Late Cenozoic Colorado River Incision and Implications for Neogene Uplift of the Colorado Rockies

    NASA Astrophysics Data System (ADS)

    Aslan, A.; Karlstrom, K. E.; Kirby, E.; Heizler, M. T.

    2012-12-01

    Basalt flows and volcanic ashes serve as a datum for calculating post-10 Ma river incision rates in western Colorado. The main picture that emerges from the data is one of regional variability of incision rates, which we hypothesize to reflect differential uplift of the Colorado Rockies during the Neogene. Maximum rates (90-180 m/Ma) and magnitudes (750-1500 m) of river incision are recorded between Grand Mesa and Glenwood Canyon, and in the Flat Tops. Minimum rates (<30 m/Ma) and magnitudes (<250 m) of river incision are associated post-Laramide normal faults within the Browns Park-Sand Wash basin in northwestern Colorado and in Middle Park of north-central Colorado. Differential uplift of the Colorado Rockies during the late Cenozoic can be inferred by comparing incision rates and magnitudes at locations upstream and downstream of knickzones. Along the Colorado River, post-10 Ma incision rates and magnitudes incision remain fairly constant (rates >100 m/Ma; magnitudes >1000 m) from Grand Mesa upstream to Gore Canyon, and then decrease markedly in Middle Park (rates <10 m/Ma; magnitudes <100 m) across the Gore Canyon knickzone. Normal-faulting of ca. 10 Ma deposits in Middle Park shows that incision rate variations partly reflect late Cenozoic faulting. Along the Yampa River, post-10 Ma incision rates and magnitudes are low (rates 15-27 m/Ma; magnitudes < 230 m) immediately upstream of Yampa Canyon, and then increase significantly (rates 96-132 m/Ma; magnitudes ~1250 m) upstream near the headwaters. We interpret this upstream increase in river incision rate and magnitude to reflect Neogene uplift of the Yampa River headwaters relative to its lower reaches. Lastly, differential late Cenozoic uplift of the Colorado Rockies is suggested by differences in the timing of regional exhumation and river incision within different drainage basins. Colorado River incision and regional exhumation occurred between 9.8 and 7.8 Ma. In contrast, Yampa River incision began between

  3. Plate boundary segmentation in the northeastern Caribbean from geodetic measurements and Neogene geological observations

    NASA Astrophysics Data System (ADS)

    Calais, Éric; Symithe, Steeve; Mercier de Lépinay, Bernard; Prépetit, Claude

    2016-01-01

    The Caribbean-North America plate boundary in the northeastern Caribbean shows a remarkable example of along-strike transition from plate boundary-normal subduction in the Lesser Antilles, oblique subduction with no strain partitioning in Puerto Rico, and oblique subduction/collision with strain partitioning further west in Hispaniola. We show that this segmentation is well marked in the interseismic strain, as measured using space geodetic data, and in the Neogene deformation regime, as derived from geological observations. Hence, interseismic segmentation, which reproduces the geological segmentation persistent over a long time interval, is inherited from the geological history and long-term properties of the plate boundary. This result is relevant to the assessment of seismic hazard at convergent plate boundaries, where geodetic measurements often show interseismic segmentation between fully-and partially-coupled plate interface regions.

  4. Variations in sea surface temperature reconstructed by algal biomarker thermometry in the Neogene equatorial Pacific sediments

    NASA Astrophysics Data System (ADS)

    Sawada, K.; Nakamura, H.; Yamamoto, S.; Kobayashi, M.

    2012-12-01

    The eastern equatorial Pacific Ocean today sustains significant amounts of global marine productivity, and the region is one of the largest marine sources of CO2 to the atmosphere. However, geological time-scale variations of marine environment and ecological / biogeochemical systems in the equatorial Pacific have been still unclear. In this study, we reconstruct the variations of sea surface temperature (SST) by long chain alkenone and the newest long-chain diol thermometers from the equatorial Pacific sediments, and discuss fluctuations in paleoceanographic and paleoclimatic systems in this region during the Neogene. Integrated Ocean Drilling Program (IODP) Expeditions 320/321 (Pacific Equatorial Age Transect; PEAT) recovered a Cenozoic sediment record from the equatorial Pacific by coring above the palaeoposition of the Equator at successive crustal ages on the Pacific plate. We used a core U1337 in the present study. We identify C37 - C38 alkenones as well as saturated C28 and C30 1,13-diols, C28 and C30 1,14-diols, and C30 1,15-diol from almost all the Neogene sediments (23 - 0.23 Ma) in a core U1337. This indicates that diatom, haptophyte and eustigmatophyte algal productions were consistently significant in the equatorial Pacific throughout the Neogene. The UK'37 values were converted to temperatures by using the calibrations reported by Prahl et al. (1988) and Kienast et al. (2012). The alkenone-based SSTs in a core U1337 were nearly constant over the past 25 Ma, ranging from 26 to 28 C, although there were two much lower spikes of 15 - 20 C in 13.2 - 12.5 Ma and 6 Ma. The Long chain Diol Index (LDI; Rampen et al., 2012) values were converted to SSTs by using the calibrations reported by Rampen et al. (2012) and Sawada et al. (unpublished data). The LDI values were estimated to be 7 - 30 C and 12 - 27 C by the Rampen et al. and Sawada et al. calibrations, respectively. The decreasing spikes of SSTs in U1337 core are observed in the horizons of 12.5Ma, 11Ma

  5. A Neogene structural dome in the Klamath Mountains, California and Oregon

    NASA Astrophysics Data System (ADS)

    Mortimer, N.; Coleman, R. G.

    1985-04-01

    Regional structural doming of Neogene age has affected rocks of the Klamath and Cascade mountains near the California-Oregon border. Evidence for this is seen in (1) subannular outcrop patterns of pre-Cretaceous lithotectonic units, (2) a crude pattern of radially oriented high-angle faults, (3) tilted Jurassic plutons, (4) tilted Cretaceous to Miocene strata, and (5) various geomorphological features. The age of doming is constrained by a major middle Miocene to earliest Pliocene angular unconformity within the Cascade Mountains and uplifted upper Miocene marine beds on the western edge of the Klamath Mountains. Uplift and doming may be the result of shortening in the Cascade fore-arc region or, more speculatively, the recent accretion of subducted material to the North American plate beneath the Klamath Mountains. *Present addresses: Mortimer, Department of Geological Sciences, University of British Columbia, Vancouver, British Columbia V6T 2B4, Canada; Coleman, U.S. Geological Survey, Menlo Park, California 94025

  6. Linked basin sedimentation and orogenic uplift: The Neogene Barinas basin sediments derived from the Venezuelan Andes

    NASA Astrophysics Data System (ADS)

    Erikson, Johan P.; Kelley, Shari A.; Osmolovsky, Peter; Verosub, Kenneth L.

    2012-11-01

    The Venezuelan Andes are an asymmetric, doubly vergent orogen that is flanked on its southeastern side by the Barinas basin. Analyses of sedimentary facies, sandstone petrography, apatite fission-tracks, and magnetostratigraphy were completed on a 1750-m section of the syn-orogenic Neogene Parángula and Río Yuca formations in the Barinas side foothills of the Venezuelan Andes. Our sedimentary facies analyses record a progression of sedimentary environments from floodplain and floodplain channel deposits through the 560-m thick Parángula Formation transitioning to distal alluvial fan deposits in the lower Río Yuca Formation and finally to an alternation of distal alluvial fan and two, ˜100-m thick organic-rich lacustrine deposits in the upper third of the section. Major- and minor-mineral petrographic analysis reveals unroofing of the Venezuelan Andes, with quartz arenite composition low in the section succeeded by metamorphic and igneous clasts and potassium feldspar appearing near the base of the Río Yuca Formation. Apatite fission-track (AFT) analysis of sandstones and pebbles generated ages of 11.2 ± 1.3 - 13.8 ± 2.0 Ma over ˜1100 m of stratigraphic section. Thermal modeling of the detrital AFT and vitrinite data from the lower Río Yuca Formation indicates exhumation of the source area was occurring by 12-13 Ma, surface exposure at 10-9 Ma, maximum burial by 4-2 Ma and exhumation of the sedimentary package starting 3-2 Ma. Accumulation of the Río Yuca Formation is contemporaneous with a basinward migration of the deformation front. Regional considerations indicate that the Venezuelan Andes evolved from a primarily singly vergent orogen to its current double vergence over the interval of Neogene-Quaternary sedimentation.

  7. Neogene Fault and Feeder Dike Patterns in the Western Ross Sea

    NASA Astrophysics Data System (ADS)

    Magee, W. R.; Wilson, T. J.

    2010-12-01

    In Antarctica, where much of the continent is covered by water and ice, geophysical data from the Antarctic submarine continental shelf is a fundamental part of reconstructing geological history. Multibeam sonar from the western Ross Sea has revealed elongate volcanic edifices and fields of elongate submarine hills on the seafloor. Origin of the submarine hills as carbonate mounds and drumlins have been proposed. The hills are up to ~8000m long and ~3500m wide, and rise 50-100m above the seafloor. Morphometric analysis of the hills shows they are elongate, with axial ratios ranging from 1.2:1 to 2:1, and some hills are linked to form elongate ridges. Seismic profiles show significant pull-ups directly below the hills, consistent with narrow, higher-density magmatic bodies; thus we favor an origin as volcanic seamounts above subsurface feeder dikes. If this volcanic hypothesis is correct, feeder dikes below the hills and elongate volcanic ridges may document magmatically-forced extension within the Terror Rift. The seamount field forms part of a regional en echelon array of volcanic ridges extending NNW from Beaufort Island toward Drygalski Ice Tongue. The ridges and elongate seamount cluster trend NNE, subparallel to mapped fault trends in this sector of the Terror Rift. This geometry is compatible with right-lateral transtension along this zone, as previously proposed for the Terror Rift as a whole. Volcanic islands and dredged volcanic ridges within the en echelon array are dated at ~7-4 Ma, implying Neogene deformation. We are completing a detailed analysis of orientation patterns and cross-cutting relations between faults and volcanic hills and their feeder systems to test this model for Neogene rift kinematics.

  8. Neogene tectonic and crustal elements in the eastern part of the NORCAL transect

    SciTech Connect

    Grose, T.L.T. . Dept of Geology and Geological Engineering); Saucedo, G.J. . Div. of Mines and Geology); Wagner, D.L. . Div. of Mines and Geology)

    1993-04-01

    Distinctive first-order Neogene tectonic provinces defined geologically in the shallow crust may also be expressed geophysically in the deep crust. They include (1) N end of Sierra Nevada block, (2) SE end of Cascade Range, (3) S margin of Modoc Plateau, and (4) W margin of Basin and Range province. Prominent second-order tectonic features include the Honey Lake depression and the Walker Lane Belt which together compose a transitional NW-trending boundary between the Sierra-Cascade arc and the Basin and Range-Modoc back arc. A less obvious more complex zone of Neogene crustal contrast between areas to N and to S passes generally EW through the Susanville area. The Susanville zone internally includes (1) the northern fault margin of the Honey Lake depression, (2) the region's greatest volcanic center (Skedaddle Mts.), (3) a well-defined westward-evolving line of volcanoes, and (4) several active geothermal systems. South of the Susanville zone (1) faults dip E and blocks tilt W, (2) Walker Lane fault zone tends N60W, (3) hornblende-rich volcanics prevail and (4) Sierran granitic rocks crop out widely. North of the Susanville zone (1) faults dip W and blocks tilt E, (2) Walker Lane trends N35W, (3) olivine-rich volcanics prevail, and (4) Cascade-Modoc volcanic rocks are ubiquitous. The Susanville zone, the S end of active Cascade volcanism, the Battle Creek fault, the Klamath-Sierra gap, the N end of the Great Valley, the Mendocino triple junction, and other features define an EW zone of crustal contrast through the NORCAL transect.

  9. A closer look at the Neogene erosion and accumulation rate increase

    NASA Astrophysics Data System (ADS)

    Willenbring, J.; von Blanckenburg, F.

    2008-12-01

    Glacial erosion and Quaternary cold-stage warm-stage climate cycling have been cited as mechanisms to explain observations of increased Neogene marine sedimentation rates. Quantification of long-term glacial erosion rates from cosmogenic radionuclides from large areas mostly covered by cold-based ice during the Quaternary show very low erosion rates over several glacial cycles. In addition, isotope ratio proxies of dissolved metals in seawater, measured in chemical ocean sediments, lack clear evidence for an increase in terrigenous denudation. In particular, the stable isotope 9Be, derived from continental erosion, shows no change in its ratio to meteoric cosmogenic nuclide 10Be, derived from rain over the past 10 My. Radiogenic Pb and Nd isotopes, mainly show a change in the style of denudation from more chemical to more physical processes in the Quaternary. These data are at odds with a suggested increase in marine sedimentation rates during the late Cenozoic. In order to resolve this contradiction we have scrutinized these sedimentation rate calculations from ocean cores to identify whether they might show only apparent increases in the Neogene sections. Potential explanations are that in some cases, measured sediment thicknesses for different time intervals lack corrections for sediment compaction. Compaction of the lower portions of the cores drastically increases the apparent thickness of the more recent (Quaternary) sediment. In addition, sedimentation rates often only appear higher for recent sections in cores due to an artifact of an averaging timescale that decreases up-core. Such an averaging time scale decrease arises from better chronological resolution in recent times (Sadler et al., 1999). Cannibalization of older sediment might add to this effect. Together, these data question a clear, global-scale Quaternary climate-erosion connection that would be unique in Earth's history.

  10. Marine environmental changes at the Brazilian equatorial margin related to Amazon River evolution during the Neogene

    NASA Astrophysics Data System (ADS)

    Lammertsma, Emmy; Troelstra, Simon; Sangiorgi, Francesca; Chemale, Farid, Jr.; do Carmo, Dermeval A.; D'Avila, Roberto; Soares, Emilson; Hoorn, Carina

    2014-05-01

    Today, the nutrient-rich Amazon River outflow causes massive algal blooms in the western equatorial Atlantic Ocean, forming a considerable carbon sink as well as a primary food source in the otherwise oligotrophic surface water. However, the history of this high-productivity system is largely unknown, although a strong relation to the evolution of the Amazon River can be expected. The Amazon submarine fan provides direct evidence for the development of a transcontinental river system, of which the base of the primarily Andean-sourced siliciclastic deposits is dated as late Miocene. Ditch cuttings from Amazon Fan exploration 'Well 2' were made available by Petrobras for microfossil and lithological research. 'Well 2' is located on the uppermost fan at a water depth of 750 meters. Organic-walled dinoflagellate cyst and foraminifer assemblages were studied to reconstruct Neogene marine environmental changes in relation to the Amazon River development. Planktonic foraminifera are present throughout the studied section and largely confirm the already available biostratigraphic age determination based on nannofossils. Benthic foraminifer assemblages indicate that the paleo-water depth has not substantially deviated from current conditions. The ecological affinities of most observed dinocyst taxa are well known, which allows us to reconstruct changes in paleo-productivity based on the assemblages. Mineral composition suggests that local river systems already drained into the Amazon basin before the onset of the transcontinental system, but environmental conditions remained oligotrophic at this time. Decreased abundances of both dinocysts and planktonic foraminifera during the Pleistocene are related to highest sedimentation rates (dilution effect). Overall, a complex interplay of orogenesis, climatic and sea level variations during the Neogene are responsible for the fluvially-induced changes in the marine environment at the Atlantic margin.

  11. Biodiversity and paleobiogeography of the European freshwater Neogene: trends, hotspots and faunal turnovers

    NASA Astrophysics Data System (ADS)

    Neubauer, Thomas A.; Harzhauser, Mathias; Georgopoulou, Elisavet; Andreas, Kroh; Mandic, Oleg

    2015-04-01

    We present an outline of a paleobiogeographic framework for the European fresh- and brackish-water systems during the Neogene. Data basis is a presence-absence matrix of lacustrine gastropods from over 2,700 localities. Cluster analyses were separately carried out on the datasets of the four time slices Early Miocene, Middle Miocene, Late Miocene, and Pliocene. Based on the results of the cluster analyses, the degree of endemicity, and geographical coherence, we classified the lake systems of the four time intervals into biogeographic units. The increasing degree of provincialism throughout the Neogene supported more detailed breakdowns in younger intervals. This pattern reflects the ongoing continentalization of Europe linked to the Alpidic Orogenesis. Additionally, the retreat of the Paratethys Sea and its isolation from the Mediterranean promoted the evolution of endemic faunas in surrounding lacustrine systems. Direct descendants such as long-lived Lake Pannon, Lake Dacia or Lake Slavonia persisted over several millions of years and promoted the evolution of highly diverse and endemic faunas. Because of their extensive duration they crucially influenced family-level composition, differences of the relative species richnesses per biogeographic unit, and rising rate of endemicity. We show that the biogeographic classification as well as the existence of biodiversity hotspots are tightly linked to the formation and evolution of long-lived lacustrine environments and thus to Europe's geodynamic history. Heat maps are provided to visualize the shifting distributions of hotspots through time. The only physiographic factor that can be shown to be correlated with species richness is the size of a lake. Other factors such as latitude, longitude or temporal duration show weak relationships. Correlation of biodiversity trends to climatic parameters such as temperature and precipitation are feasible only for selected periods. Climate is considered to have only minor

  12. The Influence of North Atlantic Valves and Gateways on Neogene Climate Change

    NASA Astrophysics Data System (ADS)

    Wright, J. D.

    2015-12-01

    Our current proxies for pCO2 suggest Neogene levels were relatively constant (~300 ± 100 ppm) except for the middle Miocene Climatic Optimum with estimates approaching 400 ± 100 ppm. Yet, the East Antarctic Ice Sheet became a polar ice sheet and permanent feature on Earth while large-scale Northern Hemisphere ice sheets waxed and waned with scant differences in pCO2. Three possibilities to explain these observations are: 1) our pCO2 proxies are incorrect; 2) Earth's climate is far more sensitive than our current model simulations suggest; or 3) tectonic differences overprinted accepted climate sensitivity to pCO2. Two marine gateways that influenced Neogene deep-water circulation are the Greenland-Scotland Ridge and the Central American Isthmus (CAI). Driven by mantle plume variations under Iceland, the GSR acted as a regulator of Northern Component Water (NCW, analogous to NADW) by controlling access to the dense polar waters to the north. During the latest Miocene and early Pliocene, mean depths along the GSR and NCW production were at their greatest. By the late Pliocene (~3 Ma), mantle plume activity increased and NCW production waned. Most researchers have focused on surface water changes (e.g., salinity) in relating closure of the CAI to Pliocene climate change. However, I propose that its primary influence came with the elimination of low-latitude, deep-water connection between the Atlantic and Pacific. Combined with vigorous NCW production, closure of the CAI re-distributed nutrients between the oceans. Carbon isotope and Cd/Ca profiles indicate that "modern" basin-to-basin differences started during the latest Miocene and were fully developed in the Pliocene. The South Atlantic path for NCW also delivered heat to the Southern Ocean, facilitating sea ice changes, as indicated by biosiliceous patterns. These tectonic boundary changes and their affects on surface and deep water circulation contributed to the Pliocene pause in global cooling that began in

  13. Southwestern Willow Flycatcher Breeding Site and Territory Summary - 2006

    USGS Publications Warehouse

    Durst, Scott L.; Sogge, Mark K.; Stump, Shay D.; Williams, Sartor O.; Kus, Barbara E.; Sferra, Susan J.

    2007-01-01

    Introduction The Southwestern Willow Flycatcher (Empidonax traillii extimus) is an endangered bird that breeds only in dense riparian habitats in six southwestern states (southern California, extreme southern Nevada, southern Utah, southwestern Colorado, Arizona, and New Mexico). Since 1993, hundreds of Southwestern Willow Flycatcher surveys have been conducted each year, and many new flycatcher breeding sites located. This document synthesizes information on all known Southwestern Willow Flycatcher breeding sites. This rangewide data synthesis was designed to meet these objectives: * identify all known Southwestern Willow Flycatcher breeding sites, and * assemble data on population size, location, habitat, and other information for all breeding sites, for as many years as possible, from 1993 through 2006. This report provides data summaries in terms of the number of flycatcher sites and the number of territories.

  14. Southwestern Power Administration Annual Report 2007

    SciTech Connect

    2008-01-01

    “Renewable energy” isn’t just a catchphrase at Southwestern Power Administration (Southwestern). It describes the hydroelectric energy we market, and the energy that Southwestern’s employees bring to work every day, constantly challenging themselves to become more eff ective and effi cient in providing aff ordable, environmentally clean power to the American people. As Southwestern’s new Administrator, I have had the opportunity to view our operations from a fresh perspective, and I’m proud to share with you how a focus on continual improvement has been evident in accomplishments throughout the agency during fi scal year (FY) 2007. When the North American Electric Reliability Corporation (NERC) implemented new reliability standards, we met applicable implementation dates and exceeded NERC’s control performance standards throughout the year. When tasked with reducing the agency’s carbon footprint, we found ways to achieve an 8.7% reduction in energy intensity from last year without impacting our operational capabilities. And when faced with record-breaking infl ows into the reservoir projects from which we market power, we capitalized on the opportunity to provide customers with signifi cant quantities of supplemental energy. Our supplemental sales this year not only saved customers over $122 million, but increased Southwestern’s revenues -- a huge win-win for Southwestern’s ratepayers and the Nation’s taxpayers alike. Southwestern is proud of its role in protecting National and economic security by contributing to the diverse supply of domestically produced energy, operating and maintaining a safe and reliable transmission system, and ensuring good stewardship of our Nation’s water resources and environment. In FY 2007, Southwestern continued to repay all power costs to the American taxpayers by marketing and delivering approximately 5.6 billion kilowatthours of hydropower at cost-based rates to customers in our six-state region. This energy

  15. The radiologist's tragedy, or Bland-White-Garland syndrome (BWGS). On the 80th anniversary of the first clinical description of ALCAPA (anomalous left coronary artery from the pulmonary artery)

    PubMed Central

    Kusa, Jacek

    2014-01-01

    In 1933, three doctors from the Massachusetts General Hospital in Boston, Paul Dudley White, William Franklin Bland, and Joseph Garland, described a case of an anomalous origin of the left coronary artery arising from the pulmonary artery (ALCAPA) in a three-month-old boy. The infant died following two weeks of hospitalization. The child's father was Dr. Aubrey Hampton, a radiologist and colleague of White, Bland, and Garland. The paper presents a perspective view on the occasion of the 80th anniversary of the first clinical description of ALCAPA. PMID:26336427

  16. The uplift of the central High Atlas as deduced from neogene continental sediments of the Ouarzazate province, Morocco

    NASA Astrophysics Data System (ADS)

    Görler, Konrad; Helmdach, Friedrich-Franz; Gaemers, Pieter; Heißig, Kurt; Hinsch, Winfried; Mädler, Karl; Schwarzhans, Werner; Zucht, Monika

    South of the central High Atlas, continental Neogene sediments crop out in the following areas: in a palaeo-drainage system in the Anti-Atlas, in a southern foredeep of the central High Atlas (Ouarzazate basin), and in the intensively folded South Atlas Marginal Zone. The latter two are characterized at the base and the top of the Neogene by thick alluvial-fan sequences and gravitational-glide slabs. They are correlated to episodes of rapid uplift of the axial zone of the High Atlas during Oligocene/Early Miocene and Late Pliocene/Early Pleistocene time. The intermediate sedimentation comprises widespread lake deposits. Charophytes, mollusks, ostracodes, fishes and small mammals from the lacustrine sediments have been studied and their biostratigraphic position (Mellalian/Vallesian to Late Pliocene) has been established. Lithology and the faunas of ostracodes and fishes demonstrate a frequent change of salinity during the lacustrine sedimentation.

  17. (abstract) Geological Tour of Southwestern Mexico

    NASA Technical Reports Server (NTRS)

    Adams, Steven L.; Lang, Harold R.

    1993-01-01

    Nineteen Landsat Themic Mapper quarter scenes, coregistered at 28.5 m spatial resolution with three arc second digital topographic data, were used to create a movie, simulating a flight over the Guerrero and Mixteco terrains of southwestern Mexico. The flight path was chosen to elucidate important structural, stratigraphic, and geomorphic features. The video, available in VHS format, is a 360 second animation consisting of 10 800 total frames. The simulated velocity during three 120 second flight segments of the video is approximately 37 000 km per hour, traversing approximately 1 000 km on the ground.

  18. The instrumental climate history of southwestern Colorado

    SciTech Connect

    Doesken, N.J.; McKee, T.B.

    1995-09-01

    Instrumental observations of the climate of southwestern Colorado date back to about 1880. Climatic conditions since the late 19th century will be described with emphasis on temperatures, temperature ranges and observed precipitation. Typical seasonal patterns of temperature and precipitation will be shown, and variations and apparent trends over time will be discussed. Drought characteristics will be described based on a standardized precipitation index developed for Colorado. Finally, brief comments on the challenge of collecting accurate and consistent long-term data will be given.

  19. Monitoring Fires in Southwestern Amazonia Rain Forests

    NASA Astrophysics Data System (ADS)

    Brown, I. Foster; Schroeder, Wilfrid; Setzer, Alberto; de Los Rios Maldonado, Monica; Pantoja, Nara; Duarte, Alejandro; Marengo, Jose

    2006-06-01

    From mid-July to mid-October 2005, an environmental disaster unfolded in the trinational region of Madre de Dios, Peru; Acre, Brazil; and Pando, Bolivia (the MAP region), in southwestern Amazonia. A prolonged dry season and human-initiated fires resulted in smoke pollution affecting more than 400,000 persons, fire damage to over 300,000 hectares of rain forest, and over US$50 million of direct economic losses. Indicators suggest that anomalous drought conditions could occur again this year.

  20. 78 FR 64494 - Southwestern Power Administration; Notice of Filing

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-10-29

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF ENERGY Federal Energy Regulatory Commission Southwestern Power Administration; Notice of Filing Take notice that on...), confirmed, approved, and placed in effect on an interim basis in Rate Order SWPA- 66, Southwestern...

  1. 77 FR 65679 - Southwestern Power Administration; Notice of Filing

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-10-30

    ... Energy Regulatory Commission Southwestern Power Administration; Notice of Filing Take notice that on..., Southwestern Power Administration annual rate for the sale of power and energy from the Willis Project to the Sam Rayburn Municipal Power Agency. Any person desiring to intervene or to protest this filing...

  2. 77 FR 5247 - Southwestern Power Administration; Notice of Filing

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-02-02

    ... Energy Regulatory Commission Southwestern Power Administration; Notice of Filing Take notice that on... in Rate Order SWPA-63, Southwestern Power Administration Integrated System Rates, Rate Schedule P-11, Wholesale Rates for Hydro Peaking Power, Rate Schedule NFTS-11, Wholesale Rates for Non-Federal...

  3. 78 FR 64494 - Southwestern Power Administration; Notice of Filing

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-10-29

    ... Energy Regulatory Commission Southwestern Power Administration; Notice of Filing Take notice that on...), confirmed, approved, and placed in effect on an interim basis in Rate Order SWPA- 67, Southwestern Power Administration annual rate for the sale of power and energy from the Rayburn Project to the Sam Rayburn...

  4. 75 FR 52527 - Southwestern Power Administration; Notice of Filing

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-08-26

    .... 714, 73 FR 57515 (Oct. 3, 2008), FERC Stats. & Regs ] 31,276 (2008) (Order No. 714). \\2\\ 18 CFR 35.28... Federal Energy Regulatory Commission Southwestern Power Administration; Notice of Filing August 19, 2010. Take notice that on August 17, 2010, the Department of Energy, Southwestern Power...

  5. 75 FR 3223 - Southwestern Power Administration; Notice of Filing

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-01-20

    ... Federal Energy Regulatory Commission Southwestern Power Administration; Notice of Filing January 8, 2010... on an interim basis in Rate Order SWPA-62, Southwestern Power Administration Integrated System Rates, Rate Schedule P-09, Wholesale Rates for Hydro Peaking Power, Rate Schedule NFTS-09, Wholesale Rates...

  6. Transformational Leadership and Teacher Motivation in Southwestern Arizona High Schools

    ERIC Educational Resources Information Center

    Reynolds, Catherine L.

    2009-01-01

    The purpose of this study was to explore the relationship between transformational leadership and teacher motivation in Southwestern Arizona high schools. Teachers in a school district in Southwestern Arizona comprised of high schools were surveyed using two instruments, Leithwood and Jantzi's (1998) The Leadership and Management of Schools in…

  7. Provenance analysis of Neogene sediments in the Thakkhola-Mustang Graben (central Nepal)

    NASA Astrophysics Data System (ADS)

    Adhikari, B. R.; Wagreich, M.

    2009-04-01

    The Thakkhola-Mustang Graben, which reflects Neogene extensional tectonics in the Tibetan Plateau and Himalaya, lies north of the Dhaulagiri-Annapurna ranges and south of the Yarlung-Tsangpo Suture Zone. The regional geology of the basin is dominated by a basement of Tibetan-Tethys sedimentary rocks of Paleozoic and Mesozoic ages, unconformably overlain by continental debris (more than 850 m) of Neogene to Quaternary age (Fort et al., 1982; Yoshida et al., 1984). Stratigraphically, the graben sediments have been divided into four formations; the Miocene Tetang and Thakkhola formations, disconformably overlain by the Plio-Pleistocene Sammargaon and Marpha formations. In the present study, the sediment provenance and the nature of the source rocks have been investigated. Field mapping, logging of 22 profiles, measurement of pebble imbrication and lithology in all possible beds and heavy mineral sampling (50 samples) were carried out. Paleocurrent data from imbricated pebbles (no other palaeocurrent indicators were seen) in the western part of the graben shows SE-directed flow while in the eastern part it shows a SSW transport. Sandstone, mudstone, quartzite and granite clasts are dominant in the Ghiling, Chaile and Dhakmar sections on the western side while carbonate clasts are dominant in the Tetang and Dhinkyo Khola sections in the southeastern part of the basin. Tourmaline, staurolite, zircon, garnet and apatite constitute a significant proportion of the heavy-minerals whereas epidote, andalusite, kyanite, chloritoid, hornblende, chrome-spinel, rutile and amphibole are less common. Paleocurrent data of imbricated conglomerates in all formations of the basin show a southward flow direction of the Kaligandaki River. All the paleocurrent data and composition analysis of the conglomerates in the northwestern part of the basin (Dhi and Tange) of the Thakkhola Formation suggest that the clasts were derived from Mesozoic rocks to the east. Mostly Paleozoic clasts, with

  8. Neogene vegetation development in the Amazon Basin: evidence from marine well-2, Foz do Amazonas (Brazil)

    NASA Astrophysics Data System (ADS)

    Bogota-Angel, Raul; Chemale Junior, Farid; Davila, Roberto; Soares, Emilson; Pinto, Ricardo; Do Carmo, Dermeval; Hoorn, Carina

    2014-05-01

    Origen and development of the highly diverse Amazon tropical forest has mostly been inferred from continental sites. However, sediment records in the marine Foz do Amazonas Basin can provide important information to better understand the influence of the Andes uplift and climate change on its plant biomes evolution since the Neogene. Sediment analyses of samples from BP-Petrobras well 1 and 2, drilled in the Amazon Fan, allowed to infer the onset of the transcontinental Amazon river and the fan phase during the middle to late Miocene (c. 10.5 Ma). As part of the CLIMAMAZON research programme we performed pollen analysis on the 10.5 to 0.4 Ma time interval. 76 ditch cutting samples of the upper 4165 m sediments of well 2 permitted us to infer changes in floral composition in the Amazon Basin. The palynological spectra across this interval (nannofossil based age model) include pollen, fern spores, dinocysts and foram lignings. When possible pollen and fern spores were grouped in four vegetation types: estuarine, tropical, mountain forest and high mountain open treeless vegetation. Pollen is generally corroded and reflects the effects of sediment transportation while reworked material is also common. Good pollen producers such as Poaceae, Asteraceae and Cyperaceae are common and reflect indistinctive vegetation types particularly those associated to riverine systems. Rhizophora/Zonocostites spp. indicate "close-distance" mangrove development. Tropical forest biomes are represented by pollen that resemble Moraceae-Urticaceae, Melastomataceae-Combretaceae, Sapotaceae, Alchornea, Euphorbiaceae, Rubiaceae, Bignoniaceae, Mauritia and Arecaceae. Myrica, and particularly sporadic occurrences of fossil fern spores like Lophosoria, and Cyathea suggest the development of a moist Andean forest in areas above 1000 m. First indicators of high altitudes appear in the last part of late Miocene with taxa associated to current Valeriana and particularly Polylepis, a neotropical taxon

  9. Neogene Palynology of the Snake River Plain: Climate Change and Volcanic Effects.

    NASA Astrophysics Data System (ADS)

    Davis, O. K.; Ellis, B.; Link, P.; Wood, S.; Shervais, J. W.

    2006-12-01

    Preliminary palynological analyses of lake sediment and inter-flow samples reveal environmental and vegetation changes in response to climatic and volcanic events over the late Neogene. On the evolutionary timescale, sagebrush steppe has expanded and coniferous and deciduous forests have declined. In part this trend has followed the cooling and drying of the late Neogene, but volcanic impact may also be recorded in the effects of long-term subsidence and in periodic deposition of volcanic tephra. The most detailed palynological record yet published for the region (Thompson, 1992) records increasing pine and juniper percentages and decreasing sagebrush and Sarcobatus percentages spanning the Pliocene Glenns Ferry Formation and Pleistocene Bruneau Formation. Palynology of a well in Lake Idaho sediments (Canyon County, Davis, this abstract) shows the same decline of sagebrush and Sarcobatus, but records decreasing juniper percentages during the Pliocene. These Lake Idaho records are spanned by the palynology of the Great Salt Lake (Davis, 2002), which records a modern pollen flora from the late Miocene onward. Salt sage and sagebrush steppe developed progressively from the late Miocene through the Holocene, with peaks in sagebrush pollen percentages during the Mio- Pliocene transition and the late Pleistocene. The Great Salt Lake and Glenns Ferry records both include low percentages of the pollen of deciduous forest taxa such as oak and elm throughout the Pliocene and sporadically into the Pleistocene. Recent studies of soils associated with volcanic tephra reveal a Pliocene upland with abundant grass and high percentages of the pollen and spores of aquatic vegetation: a landscape with drainages choked by ash falls. Palynology above the Fossil Gulch Ash (Hagerman Valley) contains abundant charcoal and high percentages of the pollen of mountain conifers, suggesting devastation of the local vegetation and erosion into Lake Idaho from the surrounding mountains

  10. Cryptic Diversity of African Tigerfish (Genus Hydrocynus) Reveals Palaeogeographic Signatures of Linked Neogene Geotectonic Events

    PubMed Central

    Goodier, Sarah A. M.; Cotterill, Fenton P. D.; O'Ryan, Colleen; Skelton, Paul H.; de Wit, Maarten J.

    2011-01-01

    events modified Africa's Neogene drainage. Haplotypes shared amongst extant Hydrocynus populations across northern Africa testify to recent dispersals that were facilitated by late Neogene connections across the Nilo-Sahelian drainage. These events in tigerfish evolution concur broadly with available geological evidence and reveal prominent control by the African Rift System, evident in the formative events archived in phylogeographic records of tigerfish. PMID:22194910

  11. Cryptic diversity of African tigerfish (genus Hydrocynus) reveals palaeogeographic signatures of linked neogene geotectonic events.

    PubMed

    Goodier, Sarah A M; Cotterill, Fenton P D; O'Ryan, Colleen; Skelton, Paul H; de Wit, Maarten J

    2011-01-01

    modified Africa's Neogene drainage. Haplotypes shared amongst extant Hydrocynus populations across northern Africa testify to recent dispersals that were facilitated by late Neogene connections across the Nilo-Sahelian drainage. These events in tigerfish evolution concur broadly with available geological evidence and reveal prominent control by the African Rift System, evident in the formative events archived in phylogeographic records of tigerfish. PMID:22194910

  12. Arctic-alpine blockfields in the northern Swedish Scandes: late Quaternary - not Neogene

    NASA Astrophysics Data System (ADS)

    Goodfellow, B. W.; Stroeven, A. P.; Fabel, D.; Fredin, O.; Derron, M.-H.; Bintanja, R.; Caffee, M. W.

    2014-07-01

    Autochthonous blockfield mantles may indicate alpine surfaces that have not been glacially eroded. These surfaces may therefore serve as markers against which to determine Quaternary erosion volumes in adjacent glacially eroded sectors. To explore these potential utilities, chemical weathering features, erosion rates, and regolith residence durations of mountain blockfields are investigated in the northern Swedish Scandes. This is done, firstly, by assessing the intensity of regolith chemical weathering along altitudinal transects descending from three blockfield-mantled summits. Clay / silt ratios, secondary mineral assemblages, and imaging of chemical etching of primary mineral grains in fine matrix are each used for this purpose. Secondly, erosion rates and regolith residence durations of two of the summits are inferred from concentrations of in situ-produced cosmogenic 10Be and 26Al in quartz at the blockfield surfaces. An interpretative model is adopted that includes temporal variations in nuclide production rates through surface burial by glacial ice and glacial isostasy-induced elevation changes of the blockfield surfaces. Together, our data indicate that these blockfields are not derived from remnants of intensely weathered Neogene weathering profiles, as is commonly considered. Evidence for this interpretation includes minor chemical weathering in each of the three examined blockfields, despite consistent variability according to slope position. In addition, average erosion rates of ~16.2 and ~6.7 mm ka-1, calculated for the two blockfield-mantled summits, are low but of sufficient magnitude to remove present blockfield mantles, of up to a few metres in thickness, within a late Quaternary time frame. Hence, blockfield mantles appear to be replenished by regolith formation through, primarily physical, weathering processes that have operated during the Quaternary. The persistence of autochthonous blockfields over multiple glacial-interglacial cycles confirms

  13. Hinterland tectonics and drainage evolution recorded by foreland basin archives: the Neogene Siwaliks of the Himalaya

    NASA Astrophysics Data System (ADS)

    Huyghe, Pascale; van der Beek, Peter; Matthias, Bernet; Catherine, Chauvel; Jean-Louis, Mugnier; Laurent, Husson; François, Chirouze

    2014-05-01

    Provenance analysis and detrital thermochronology of detrital synorogenic sediments, derived from erosion of mountain belts and deposited in surrounding sedimentary basins, are well-established methods to examine the exhumation history of convergent zones, tectonic activity and the associated evolution of the drainage network. We have conducted multidisciplinary studies on magnetostratigraphically dated sections throughout the Neogene Siwalik foreland basin of the Himalayan belt since more than 10 years. Sr, Nd and Hf isotopes are used as provenance indicators, providing information on the nature and size of catchment basins and their evolution through time in response to tectonics. Detrital zircon and apatite thermochronology provides constraints on exhumation rates in the hinterland of the Himalaya and the deformation of the Sub-Himalayan foreland basin. Throughout the Himalaya, detrital zircons from the Siwaliks generally show three age peaks: two static peaks (i.e., displaying constant peak ages through time), and a moving peak. The latter shows a constant lag time of ~4 m.y. corresponding to source-area exhumation rates on the order of 1.8 km/my, while the two static peaks respectively reveal a major 15-20 Ma exhumation event in the belt, the significance of which is still debated, and inheritance of pre-Himalayan ages that indicate recycling of Tethyan sediments. Therefore, our ZFT results suggest that the exhumation dynamics are broadly similar throughout the Himalaya since at least 13 m.y, as also shown by the Bengal Fan detrital sediment record. We relate this switch in tectonic regime to the destabilization of the Himalayan wedge that is rendered overcritical as a response to the transience of dynamic topography caused by the deforming underlying Indian slab. Nonetheless, in detail, the timing of thrusting in the Siwalik domain is delayed by about 1 my eastward as demonstrated by both structural and apatite fission-track data, suggesting overall eastward

  14. Late Neogene oroclinal bending in the central Taurides: A record of terminal eastward subduction in southern Turkey?

    NASA Astrophysics Data System (ADS)

    Koç, Ayten; van Hinsbergen, Douwe J. J.; Kaymakci, Nuretdin; Langereis, Cornelis G.

    2016-01-01

    The Tauride fold-thrusts belt formed during ∼S-N convergence between Africa and Eurasia since Cretaceous time. The western end of the central Taurides strike NW-SE, highly obliquely to the overall convergence direction, and connect to the NE-SW Beydağları-Lycian Nappe flank of the western Taurides, forming the so-called 'Isparta Angle'. In Neogene time, the western and central Taurides and the inner part of the Isparta Angle became overlain by Neogene sedimentary basins including Manavgat, Köprüçay and Aksu, characterized by marine clastics and carbonates. The eastern limb of the Isparta Angle experienced multidirectional Miocene to Present extension, whereas E-W shortening affected the marine sedimentary basins in the heart of the Isparta Angle. To quantitatively reconstruct the Neogene kinematic evolution of the Taurides, towards restoring the subduction system accommodating Africa-Eurasia convergence, we paleomagnetically assess if and when vertical axis rotations affected the Manavgat, Köprüçay, and Aksu basins in Early Miocene to Pliocene times. We show that the northern Köprüçay Basin rotated ∼20-30° clockwise, the Manavgat Basin underwent ∼25-35° counterclockwise rotation, and the Aksu Basin underwent no rotation since the Early-Middle Miocene. It was previously shown that the Beydağları region underwent a post-Middle Miocene ∼20° counterclockwise rotation. These results show that the prominent oroclinal salient geometry of the western Taurides thus acquired, at least in part, since Miocene times, that the Köprüçay Basin rotated relative to the Aksu Basin along the Aksu thrust, and that the Beydağları platform rotated relative to the Aksu Basin along the Bucak thrust, which must have both been active until Late Neogene time. This synchronous E-W shortening in the heart of the Isparta Angle, and multidirectional extension in its eastern limb may be explained by relative westward retreat of an eastward dipping subducting Antalya

  15. Faunal turnover in Neogene to Recent Caribbean reef corals and region environmental change

    SciTech Connect

    Budd, A.F. . Geology Dept.); Johnson, K.G. . Palaeontology Dept.); Stemann, T.A. . Geologisches Inst.)

    1993-03-01

    Quantitative analyses of species richness and species extinction and origination rates in the Neogene to Recent Caribbean reef coral fauna show that a major episode of turnover occurred during middle to late Pliocene time (4--1 Ma). The data for the authors analyses consist of a new compilation of occurrences of 175 species and 49 genera in reef sequences in the Dominican Republic and Costa Rica and in 21 scattered sites ranging in age from 22 Ma to present. The results show that: (1) during turnover, more than 75% of all species living between 6--4 Ma (n = 82) became extinct; (2) during turnover, extinction and origination rates were equally and simultaneously high, and a relatively constant number of species was maintained in the fauna; (3) the taxonomic composition of Caribbean reefs remained relatively constant before (10--4 Ma) and after (1--0 Ma) turnover. Turnover therefore preceded the high frequency sea level oscillations of late Pleistocene time, and appears related to long-term, unidirectional changes in climate and/or ocean circulation across the Caribbean region in association with closure of the Isthmus of Panama. The observed correspondence between high origination and extinction rates indicates that the same environmental factors may have been associated with increases in both rates, and that local habitat differentiation and fragmentation may have been involved. Stability persisted in the region despite the severe environmental stresses associated with Pleistocene climate change.

  16. Neogene marine isotopic evolution and the erosion of Lesser Himalayan strata: Implications for Cenozoic tectonic history

    NASA Astrophysics Data System (ADS)

    Myrow, Paul M.; Hughes, Nigel C.; Derry, Louis A.; Ryan McKenzie, N.; Jiang, Ganqing; Webb, A. Alexander G.; Banerjee, Dhiraj M.; Paulsen, Timothy S.; Singh, Birendra P.

    2015-05-01

    An extensive, northward deepening blanket of Neoproterozoic and Cambrian sedimentary rocks once extended from the Himalayan margin far onto the Indian craton. Cambrian deposits of this "upper Lesser Himalayan" succession, which include deposits of the "outer" Lesser Himalaya tectonic unit, are enriched in radiogenic 187Os. They make up part of a proximal marine facies belt that extends onto the craton and along strike from India to Pakistan. By contrast, age-equivalent facies in the Tethyan Himalaya are more distal in nature. Neoproterozoic to Cambrian strata of the upper Lesser Himalayan succession are now missing in much of the Lesser Himalaya, with their erosion exposing older Precambrian Lesser Himalayan strata. We suggest that exhumation and weathering of the upper Lesser Himalaya and related strata caused dramatic changes in the 187Os/188Os and 87Sr/86Sr Neogene record of seawater starting at ∼ 16 Ma. First-order estimates for the volume of upper Himalayan strata, as well as the volume of all LH rock eroded since this time, and geochemical box modeling, support this idea. Exhumation at 16 Ma is a fundamental event in the evolution of the Himalayan orogeny and the geochemical evolution of the oceans, and will be a critical part of the construction of future models of Himalayan thrust belt evolution.

  17. The Qasr As Sahabi succession and the Neogene evolution of the Sirte Basin (Libya)

    NASA Astrophysics Data System (ADS)

    Carmignani, L.; Giammarino, S.; Giglia, G.; Pertusati, P. C.

    The Neogene succession in Libya is characterized by three main sedimentary cycles: 1) A Middle Miocene cycle, involving the whole coastal area of Libya, composed of platform limestones in Cyrenaica and Tripolitania and of deeper deposits in the central part of the Sirte Basin; 2) A Tortonian-Messinian cycle, composed of evaporitic, lagoonal and shallow oolitic deposits, well documented paleontologically in Sirtica between 30° and 31° lat. N. and above all near Qasr As Sahabi. These deposits are found westwards as far as A1 Khums, where they unconformably lie on the Cretaceous and older rocks. Northwards, they surround the structural high of Cyrenaica to beyond Benghazi. Along the western margin of Cyrenaica they lie on Middle Miocene limestones, and to the N-NW on the Eocene. They are bounded landwards by a scarp of marine erosion ("Upper Cyrenaica Escarpment") which models a system of normal faults; 3) A cycle composed of presumed Pliocene coastal or brackish deposits covering a paleomorphology cut during the Upper Messinian regression. South of Cyrenaica, the Pliocene transgression extends beyond the Upper Miocene coastline as far as the A1 Jaghbub oasis. Seawards, the Pliocene cycle deposits are cut by another scarp ("Lower Cyrenaica Escarpment"). The interval between this scarp and the sea is covered by a further transgressive cycle of Tyrrhenian age.

  18. Depositional environmental and geologic age of neogene rocks at Cape Aliaksin, Beaver Bay, Alaska Peninsula

    SciTech Connect

    Armentrout, J.M.

    1985-04-01

    Neogene sandstone and conglomerate cropping out along the eastern end of Beaver Bay at Cape Aliaksin have been assigned to the Unga Conglomerate Member of the Bear Lake formation. New data suggest that this correlation may be incorrect. The fossil assemblage includes gastropods, pelecypods, barnacles, and echionoids indicative of a shallow marine, cold-water biofacies. Taxa indicate a strong similarity to the fossil assemblage of the Tachilni Formation and the upper Bear Lake Formation, both assigned to the late Miocene Graysian Molluscan stage, approximately 12 Ma to 3 Ma. Teeth of the desmostylian (sea cows) Desmostylus sp. cf. D. hesperus have been collected from the Cape Aliaksin beds. D. Hesperus is known from North Pacific rocks assigned to the late early to early late Miocene, approximately 18 ma to 10 Ma. The Unga Conglomerate is in part typified by the middle Miocene pelecypod Mytilus gratacapi and an associated fauna unlike that of the Cape Aliaksin beds. It is suggested that the Cape Aliaksin beds are younger than the Unga Conglomerate, and are correlative to the upper Bear Lake Formation and Tachilni Formation rocks of early late Miocene age.

  19. Geochemical investigation and characterisation of Neogene sediments from Valjevo-Mionica Basin (Serbia)

    NASA Astrophysics Data System (ADS)

    Šajnović, Aleksandra; Stojanović, Ksenija; Jovančićević, Branimir; Golovko, Anatoly

    2009-02-01

    Sediments from the Valjevo-Mionica Basin of Neogene age were investigated in this study using different geochemical methods. The results of the inorganic part analyses suggest that during genesis of the sediments, the contents of Na2O, B and As changed the most, which indicates that genesis of the investigated sediments was followed by climate changes and volcanic activity. The quantity of other macro- and microelements did not vary significantly. Investigations of the organic substance showed that it is native organic matter, which has been preserved to a significant extent, formed predominantly of algal precursor organisms, which provided good quality, deposited under reducing conditions and that it is at a low maturity level. As it has been established that genesis of the investigated sediments was mostly affected by an arid climate with more intensive salinity, the aim of this study, was also to identify the processes which were the most affected by the change in salinity, as well as biomarkers which are the most sensitive to this change. The results led to the conclusion that the salinity increase in the depositional environment had a primary effect on the preservation of the organic substance and the formation of the mineral searlesite. In addition, it was noticed that besides the Sq/ nC26 ratio, the parameters nC17/ nC27, CPI and Ph/ nC18, are also significantly sensitive to salinity change in a depositional environment in case of immature organic substance deposited under reducing conditions.

  20. Neogene compressional deformation and possible thrust faulting in southwest Dominican Republic

    NASA Technical Reports Server (NTRS)

    Golombek, M. P.; Goreau, P.; Dixon, T. H.

    1985-01-01

    Analysis of regional and high resolution remote sensing data coupled with detailed field investigations indicates Neogene compressional deformation in the southwest Dominican Republic. Airborne synthetic aperture radar data and high resolution near infrared photography show folds in Tertiary sediments and possible thrust fault scarps implying NE to SW compression in the region. Large road cuts through the scarps allow study of otherwise poorly accessible, heavily vegetated karst terrain. Deformation increases toward scrap fronts where small bedding-plane thrust faults become more numerous. Analysis of mesoscopic faults with slickensides indicates compression oriented between N to S and E to W. The lowermost scarp has highly sheared fault breccia and undeformed frontal talus breccias implying it is the basal thrust into which the higher thrust faults sole. Thus, the scarps probably formed in a regional NE to SW compressional stress regime and are the toes of thrust sheets. Previous workers have suggested that these scarps are ancient shorelines. However, the gross morphology of the scarps differs substantially from well known erosional terraces on the north coast.

  1. Lower crustal zircons reveal Neogene metamorphism beneath the Pannonian Basin (Hungary)

    NASA Astrophysics Data System (ADS)

    Downes, Hilary; Carter, Andrew; Armstrong, Richard; Dobosi, Gabor; Embey-Isztin, Antal

    2015-08-01

    Neogene alkaline intraplate volcanic deposits in the Pannonian Basin (Hungary) contain many lower crustal granulite-facies xenoliths. U-Pb ages have been determined for zircons separated from a metasedimentary xenolith, using LA-ICPMS and SHRIMP techniques. The zircons show typical metamorphic characteristics and are not related to the hostmagmatism. The oldest age recorded is late Devonian, probably related to Variscan basement lithologies. Several grains yield Mesozoic dates for their cores, which may correspond to periods of orogenic activity. Most of the zircons show young ages, with some being Palaeocene-Eocene, but the majority being younger than 30Ma. The youngest zircons are Pliocene (5.1-4.2 Ma) and coincide with the age of eruptions of the host alkali basalts. Such young zircons, so close to the eruption age, are unusual in lower crustal xenoliths, and imply that the heat flow in the base of the Pannonian Basin was sufficiently high to keep many of them close to their blocking temperature. This suggests that metamorphism is continuing in the lower crust of the region at the present day.

  2. [Dicotyledons of cretaceous, palaeogene, and neogene. Adaptogenesis of the terminal phloem].

    PubMed

    Gamaleĭ, Iu V; Pakhomova, M V; Sheremet'ev, S N

    2008-01-01

    A database containing information on the trait complex for terminal phloem of dicots leaf having been created during the last thirty years was analyzed. The typology of terminal phloem was verified. The monotypy of plant taxa up to the family level was confirmed. For orders and subclasses, the wide distribution of structural parallelisms was demonstrated. The lists of plant families with similar structures of the phloem terminals was elaborated. As a result of comparative analysis of these lists and paleobotanic data on the age of plant families, the specificity of the types of terminal phloem and the associated morphological and functional characteristics of the groups of families of the same evolutionary, age were revealed. Ancestral type prevails among the families belonging to Prodicots, which were emerged during Cretaceous. Symplastic type is characteristic to the families of Eudicots and biomes appeared in Paleogene, while the apoplastic type is characteristic to the families and biomes of Neogene. For each group to taxa, plant stem and root parasitism is characteristic for the crown taxa completing the structural sequences of trees and herbs. All these data allow discussion of the questions of climatic adaptogenesis of the character complex studied here, the impossibility of structural iterations in morphological evolution, and the reasons of similarities and differences in the evolutionary and contemporary zonal series of the terminal phloem in Dicots. PMID:18677965

  3. Migration history of air-breathing fishes reveals Neogene atmospheric circulation patterns

    NASA Astrophysics Data System (ADS)

    Böhme, M.

    2004-05-01

    The migration history of an air-breathing fish group (Channidae; snakehead fishes) is used for reconstructing Neogene Eurasian precipitation and atmospheric circulation patterns. The study shows that snakeheads are sensitive indicators of summer precipitation maxima in subtropical and temperate regions, and are present regularly if the wettest month exceeds 150 mm precipitation and 20 °C mean temperature. The analysis of 515 fossil freshwater fish deposits of the past 50 m.y. from Africa and Eurasia shows two continental-scale migration events from the snakeheads' center of origin in the south Himalayan region, events that can be related to changes in the Northern Hemisphere circulation pattern. The first migration, ca. 17.5 Ma, into western and central Eurasia may have been caused by a northward shift of the Intertropical Convergence Zone that brought western Eurasia under the influence of trade winds that produced a zonal and meridional precipitation gradient in Europe. During the second migration, between 8 and 4 Ma, into Africa and East Asia, snakeheads reached their present-day distribution. This migration could have been related to the intensification of the Asian monsoon that brought summer precipitation to their migratory pathways in East Africa Arabia and East Asia.

  4. Neogene mammalian faunal change in southern Asia: Correlations with climatic, tectonic, and eustatic events

    NASA Astrophysics Data System (ADS)

    Barry, John C.; Johnson, Noye M.; Mahmood Raza, S.; Jacobs, Louis L.

    1985-09-01

    The fluvial Neogene Siwalik formations of northern Pakistan span long time intervals with only minor hiatuses and, being highly fossiliferous, are uniquely suited for studies of change in mammalian faunas. Magnetostratigraphic correlations of a critical stratigraphic section give dates for 45 middle and late Miocene biostratigraphic events. These mark either first appearances or extinctions in the mammal fauna and show that in the Siwaliks there were major fauna turnovers at between 20 and 16 Ma and at 9.5 and 7.4 Ma. Two minor faunal events are dated at 13.2 and about 12 Ma. Many species making their first appearance were immigrants from Europe or Africa and indicate when connections to those regions existed. Immigration and extinction were the dominant modes of faunal change; in situ evolution was much less important. The Siwalik biostratigraphic record correlates closely to climatic, oceanographic, and tectonic events, which probably controlled immigration into southern Asia. Abiotic events were therefore important factors affecting evolution of the mammal communities.

  5. Neogene structural characteristics of Louisiana shelf with emphasis on growth-fault interplay with salt tectonics

    SciTech Connect

    Xue, Fangjian, Xi, Jiebo )

    1996-01-01

    Growth faulting and salt tectonics are the most pronounced structural features in the offshore Louisiana. Regional examination of seismic data(4 mile x 4 mile grid) of OCS area Suggests that polyphase halokinesis happened along the whole shelf area during the Neogene sedimentation but with different type of salt movement and faulting in time and space. The sublinear and regularly basinward-dipping lower and middle Miocene faults predominate beneath the present inner shelf region with scarcity of shallow salt features. These fault trends detached on bottom Miocene decollement related ductile shale and salt welds. The shorter and more arcuate-shaped upper Miocene and Pliocene faults complicated by abundant near-surface salt bodies characterize the farther offshore beneath the outer-shelf region. Most of these fault root into or related to salt diapirs, but at the West Cameron and at the South Timberlier, families of growth-faults were developed on the upper Miocene allochthonous salt sheet detachment and played an important role in segmenting salt sheet in this salt raft regime. The more irregularly oriented Pleistocene faults with combination of shallow basinward-dipping and counter-basinward-dipping detachment on top of large and thick upper Pliocene allochthonous salt mass occurred in the present shelf edge and slope region. This study suggest at least three episodes of salt movement occurred at early Miocene, late Miocene-early Pliocene and early Pleistocene and the existence and possible position of large right-slip transfer faults.

  6. Accretion in the wake of terrane collision: The Neogene accretionary wedge off Kenai Peninsula, Alaska

    USGS Publications Warehouse

    Fruehn, J.; Von Huene, R.; Fisher, M.A.

    1999-01-01

    Subduction accretion and repeated terrane collision shaped the Alaskan convergent margin. The Yakutat Terrane is currently colliding with the continental margin below the central Gulf of Alaska. During the Neogene the terrane's western part was subducted after which a sediment wedge accreted along the northeast Aleutian Trench. This wedge incorporates sediment eroded from the continental margin and marine sediments carried into the subduction zone on the Pacific plate. Prestack depth migration was performed on six seismic reflection lines to resolve the structure within this accretionary wedge and its backstop. The lateral extent of the structures is constrained by high-resolution swath bathymetry and seismic lines collected along strike. Accretionary structure consists of variably sized thrust slices that were deformed against a backstop during frontal accretion and underplating. Toward the northeast the lower slope steepens, the wedge narrows, and the accreted volume decreases notwith-standing a doubling of sediments thickness in the trench. In the northeasternmost transect, near the area where the terrane's trailing edge subducts, no frontal accretion is observed and the slope is eroded. The structures imaged along the seismic lines discussed here most likely result from progressive evolution from erosion to accretion, as the trailing edge of the Yakutat Terrane is subducting.

  7. Importance of Neogene siliceous rocks as the source of petroleum in Japan

    SciTech Connect

    Aoyagi, K. ); Omokawa, M. )

    1989-01-01

    Major oil and gas fields in Japan are located in the area from the central Hokkaido through northeast Honshu. Most productive horizons are generally found in formations of the late Middle Miocene (approximately 12-10 Ma) Onnagawa provincial stage of Japan. These formations are composed mainly of hard mudstone, siliceous shale, diatomaceous mudstone, marlite, and acidic pyroclastic rocks. Source rock potentials in argillaceous rocks of the Miocene Ohdoji Formation in Aomori, the Onnagawa Formation in Akita, and the Lower Teradomari Formation in Niigata show the highest values as compared with other formations in these areas. Average contents of organic carbon and hydrocarbons of siliceous sediments such as diatomite, siliceous shale, and chert in the Aomori basin indicate the higher values as compared with other argillaceous sediments. Diatoms, which appeared in the later Cretaceous, are the principal primary producers of organic matter in the marine environment during the Cenozoic. Organic components and biological productivity show that diatoms have been the most important source of petroleum during the Neogene in Japan.

  8. Geological Studies in eastern Venezuela and Trinidad from Cretaceous passive margin to Neogene transpressional thrust belt

    SciTech Connect

    Algar, S.T.; Erikson, J.E.; Pindell, J.L. )

    1991-03-01

    Sedimentological and structural analyses of Trinidad's Northern and Central ranges and Venezuela's Serrania del Interior have led to new interpretations of northeastern. South America's tectonic evolution within the Southern Caribbean Plate Boundary Zone. Medial ( ) Jurassic through early Cenozoic passive margin sediments make up the majority of these areas and were deposited somewhat to the WNW (between 80 and 130 km for Northern Range of Trinidad) of their present positions prior to structural shortening. Neogene southeastward displacement of Jurassic-Cretaceous passive slope and rise sediments (Northern Range) drove propagation of thrusts southward into the Serrania and Central ranges. Displacements were driven by migration of the Caribbean Plate relative to South America. Thus, the Serrania and Central ranges are the western hemisphere's only exposed Mesozoic-Cenozoic passive Atlantic margin stratigraphic section. As such, they provide a Cretaceous-Paleogene record of passive margin sedimentation at a thermally subsiding margin where the complicating effects of tectonism are absent. This makes these sections especially suited for studies of eustatic sea level behavior. Preliminary assessments are shown which suggest that sea level changes for Cretaceous to Paleogene time are not as pronounced as the frequent large and rapid sea level falls and rises that are promoted by some.

  9. The Central American Seaway and the Late Neogene ocean conveyor belt

    NASA Astrophysics Data System (ADS)

    Schneider, Birgit; Krebs-Kanzow, Uta; Park, Wonsun

    2013-04-01

    'The great ocean conveyor belt' depicts the large scale exchange of water mass properties between today's oceans. Over the past million years the tectonic evolution of ocean passages altered this pan-oceanic communication. The last such tectonic transformation was the closure of the Central American Seaway (CAS) which represented a low latitude gateway between Pacific and Atlantic prior to 4 million years ago. We use a coupled general circulation model and configure the topography for the past. The Central American Seaway modifies the global ocean circulation and the ocean conveyor belt which implies drastic changes in water mass properties and inter basin heat and freshwater transports. Compared to an experiment with modern basin geometry, a 1000-meter deep passage at the location of today's Isthmus of Panama results in a fundamental change in the warm water route of the conveyor belt while the cold path remains qualitatively unchanged. A transport of 10 Sv from Pacific to Atlantic is associated with the meridional transport in the South Atlantic changing from 10Sv northward to 2 Sv southward. Both Indonesian throughflow and export of warm water from the Indian Ocean across 30S are reduced by about 7 Sv. Analysing transports in density classes we are able to propose a sketch of the late Neogene conveyor belt.

  10. Newfoundland Neogene sediment drifts: transition from the Paleogene greenhouse to the modern icehouse

    NASA Astrophysics Data System (ADS)

    Friedrich, O.; Norris, R. D.; Wilson, P. A.; Opdyke, B. N.

    2015-05-01

    This workshop brought together specialists from various fields to develop a drilling proposal to fill the "Oligo-Miocene Gap" that exists in our understanding of the functions of Earth's systems. We propose to establish the first continuous high-deposition record of the Oligo-Miocene through new International Ocean Discovery Program (IODP) drilling in the North Atlantic to allow the development of a continuous Neogene cyclostratigraphy and to enhance our knowledge of Oligo-Miocene ocean-ice-climate dynamics. The workshop was held in Heidelberg from 15 to 17 September 2014 funded by ESF (EARTHTIME EU), NSF, and the ECORD MagellanPlus Workshop Series Program. A total of 24 participants from six different countries (Australia, France, Germany, the Netherlands, United Kingdom, and United States) attended the workshop, including several early career stage researchers. We discussed certain aspects of Cenozoic paleoceanography and paleoclimate and how the gaps in the Oligo-Miocene could be filled using scientific drilling. The ultimate goal of the workshop (to submit a pre-proposal to IODP) was achieved (IODP Proposal 874-pre was submitted 1 October 2014). Our workshop consisted of overview presentations followed by self-selected breakout groups that discussed different topics and produced text and figures for the proposal. Here, we give a short overview of the major topics discussed during the workshop and the scientific goals presented in the resulting IODP pre-proposal.

  11. Low permeability Neogene lithofacies in Northern Croatia as potential unconventional hydrocarbon reservoirs

    NASA Astrophysics Data System (ADS)

    Malvić, Tomislav; Sučić, Antonija; Cvetković, Marko; Resanović, Filip; Velić, Josipa

    2014-06-01

    We present two examples of describing low permeability Neogene clastic lithofacies to outline unconventional hydrocarbon lithofacies. Both examples were selected from the Drava Depression, the largest macrostructure of the Pannonian Basin System located in Croatia. The first example is the Beničanci Field, the largest Croatian hydrocarbon reservoir discovered in Badenian coarse-grained clastics that consists mostly of breccia. The definition of low permeability lithofacies is related to the margins of the existing reservoir, where the reservoir lithology changed into a transitional one, which is mainly depicted by the marlitic sandstones. However, calculation of the POS (probability of success of new hydrocarbons) shows critical geological categories where probabilities are lower than those in the viable reservoir with proven reserves. Potential new hydrocarbon volumes are located in the structural margins, along the oil-water contact, with a POS of 9.375%. These potential reserves in those areas can be classified as probable. A second example was the Cremušina Structure, where a hydrocarbon reservoir was not proven, but where the entire structure has been transferred onto regional migration pathways. The Lower Pontian lithology is described from well logs as fine-grained sandstones with large sections of silty or marly clastics. As a result, the average porosity is low for conventional reservoir classification (10.57%). However, it is still an interesting case for consideration as a potentially unconventional reservoir, such as the "tight" sandstones.

  12. Cancer mortality and radioactive fallout in southwestern Utah.

    PubMed

    Machado, S G; Land, C E; McKay, F W

    1987-01-01

    Cancer mortality was compared between a three-county region in southwestern Utah and the remainder of Utah in an investigation of reported excess cancer risks associated with residence in southwestern Utah during the period of above-ground nuclear tests at the Nevada Test Site. Because most of the fallout in southwestern Utah was deposited during 1953-1957, comparisons were limited to persons born before 1958, and deaths from leukemia and bone cancer during 1955-1980 and from other cancers during 1964-1980. There was no excess risk of cancer mortality in southwestern Utah, for single or grouped sites, with the single exception of leukemia which showed statistically significant odds ratios of 1.45 based on 62 deaths at all ages, and 2.84 based on nine deaths at ages 0-14. The finding for childhood leukemia was based on different time periods and geographic comparisons from those of two earlier studies in which no such excess was found. Mortality from all cancer sites combined was significantly lower in southwestern Utah than in the remainder of the state, even after adjustment for the higher proportion of (lower risk) Mormons in southwestern Utah. The present results, including the positive association for leukemia, are inconsistent with the high excess risks reported by Johnson (JAMA 1984;251:230-6) based on an interview survey of cancer incidence among long-term Mormon residents of southwestern Utah. PMID:3788954

  13. Regional tectonics and seismicity of southwestern Iowa

    NASA Astrophysics Data System (ADS)

    Vaneck, O. J.; Anderson, R. R.; Cumerlato, C. L.; Faller, T. H.; Logel, J. D.

    1982-11-01

    Utilizing gravity and aeromagnetic data, a series of geophysical profiles were constructed across the Midcontinent Geophysical Anomaly (MGA) which extends across the southwestern Iowa study area. By combining the information provided by modeling techniques with limited deep well data, a map of the Precambrian basement was generated. The interpretation that emerged includes a central horst of igneous intrusives and extrusives, extensively faulted, and overlain in some areas by Keweenawan clastics. The horst is flanked by a series of high angle faults, with the majority of the faults displaying vertical displacement along two structural zones, the Thurman-Redfield Structural Zone, along with flanks the northwestern boundary. The total vertical displacement present along these fault zones is estimated to be a maximum of 9 km. Two clastic-filled basins flank the horst, one of which has an interpreted depth of 10 km.

  14. Environmental Assessment for power marketing policy for Southwestern Power Administration

    SciTech Connect

    Not Available

    1993-12-01

    Southwestern Power Administration (Southwestern) needs to renew expiring power sales contracts with new term (10 year) sales contracts. The existing contracts have been in place for several years and many will expire over the next ten years. Southwestern completed an Environmental Assessment on the existing power allocation in June, 1979 (a copy of the EA is attached), and there are no proposed additions of any major new generation resources, service to discrete major new loads, or major changes in operating parameters, beyond those included in the existing power allocation. Impacts from a no action plan, proposed alternative, and market power for less than 10 years are described.

  15. Ground Level Observations of a Possible Downward-Beamed TGF during a Rocket-Triggered Lightning Flash at Camp Blanding, Florida in August 2014

    NASA Astrophysics Data System (ADS)

    Bozarth, A.; Dwyer, J. R.; Cramer, E. S.; Rassoul, H.; Uman, M. A.; Jordan, D.; Grove, J. E.

    2015-12-01

    Ground level high-energy observations of an August 2014 rocket-triggered lightning event at the International Center for Lightning Research and Testing (ICLRT) in Camp Blanding, Florida show a 180 µs burst of multiple-MeV photons during the latter part of the Upward Positive Leader (UPL) phase of an altitude-triggered lightning flash, following the first, truncated return stroke. The timing and waveform profile being atypical from x-ray emissions from lightning leaders, our observations suggest the occurrence of a downward beamed terrestrial gamma ray flash (TGF). Instrumentation operating during this event include a set of 16 NaI(TI)/PMT detectors plus 7 1-m2 plastic scintillation detectors spread across the 1 km2 facility, with 38 additional Na(TI)/PMT detectors located inside the 1"-thick Pb-shielded x-ray camera and an x-ray spectrometer. Comparing the location and energy data from these detectors to Monte Carlo simulations of TGFs from the REAM code developed by Dwyer [2003], our analysis investigates possible TGF production regions and determines the likelihood of the observed high-energy emissions being produced by a TGF inside the thunderstorm.

  16. Seismic architecture and morphology of Neogenic sediment waves and drifts, offshore West Africa

    NASA Astrophysics Data System (ADS)

    Baglioni, Luca; Bonamini, Enrico

    2013-04-01

    The three dimension visualisation softwares of seismic data and the recent development of semi-automatic interpretation tools allow to define the 3D morphology of ancient depositional systems at a resolution never achieved before. This study analyses a Neogenic stratigraphic interval in the deep water of the West African margin. The purpose of the work is the understanding of the sedimentary architectures and the link with the genetic depositional processes. The study is mainly based on the interpretation of seismic geometries and amplitude/isochron maps derived from newly-interpreted seismic horizons. The seismic stratigraphy reveals abrupt changes in depositional styles and sedimentary processes. Transitions between Sediment Drifts (SD), Sediment Waves (SWs) and Mass Transport Complexes (MTCs) are here frequently observed, suggesting that cyclically either bottom-current intensity decreased or gravity-flow input overwhelmed the bottom-current signal. The lower studied interval corresponds to a SD sequence, made up of stacked individual packages and having a maximum thickness of 300 ms. The landward drift morphology is characterized by convex-upward, mounded seismic reflections. Each drift onlaps on a seaward-dipping reflection interpreted as paleo-slope. These contouritic deposits are concentrated near the base of slope, and fade out downdip. The drift appears to be grown from the deeper part of the basin and backstepped up the slope. It is inferred that the deposition of the drifts took place under the influence of a marine current, subparallel to the southern margin of West African coast. The backstepping of the onlapping architecture may have resulted from bottom current acceleration across the ramp. The intermediate studied interval represents a transitional sequence in which SW are alternated with MTDs of minor size (up to 60 ms thick). In this transition interval, onlap relationships and thickness variations suggest that gravity flow deposits preferentially

  17. Chemical and Isotope Compositions of Neogene Hippopotamidae Teeth From Lake Albert (Uganda): Implications for Environmental Change

    NASA Astrophysics Data System (ADS)

    Brugmann, G. E.; Brachert, T. C.; Ssemmanda, I.; Mertz, D. F.

    2008-12-01

    The Neogene was a period of long-term global cooling and increasing climatic variability on astronomical time scales. Lake systems strongly depend on rainfall patterns and size or geographical distribution of river networks. To unravel environmental change and watershed dynamics in the western branch of the East African Rift (Lake Albert, Uganda) during the Late Neogene, we use proxy data (trace elements, O, C and Sr isotopes) from Hippopotamidae teeth. Laser ablation ICPMS profiles in enamel measured from the outside rim towards the dentin show an asymmetric trace element distribution in that the concentrations continuously decrease by up to 5 orders of magnitude within a distance of about 1 mm until a minimum is reached (<10 ppb for REE, Y, U). From thereon concentrations stay rather constant or even increase until about 100 μm in front of the dentin where concentrations rise sharply. This concentration minimum represents the least altered part of the enamel and it probably represents a primary biological fingerprint which has the potential to monitor migration pathways and palaeoenvironmental changes. On geological time scales δ13C compositions reflect a transition from pure C3 browsers (-11 per mil PDB) at 5 to 6 Ma towards C4 dominated grazers (0 per mil PDB) at 2.0 to 2.5 Ma. The oxygen stable isotope (δ18O) composition of enamel rises from 26 per mil at 5 to 6 Ma to a maximum of 32 per mil SMOW at 2.3 Ma. Increasing δ18O values suggest enhanced evaporation of the lake due to rising aridity. This is in agreement with a synchronous spread of C4 vegetation in the reach of Hippopotamid populations. The Sr isotopic composition of enamel displays a large variation and 87Sr/86Sr is 0.714 about 5 Ma ago, reaches a maximum of 0.717 at about 2.3 Ma and decreases from there on to about 0.708. Thus, Sr and O isotopic compositions correlate with each other on the geological time scale. This is plausible if the Sr isotopic composition of Hippopotamid enamel dominantly

  18. Tephrochronolgical Studies of Late Neogene Sediments in Interior Alaska and the Yukon Territory

    NASA Astrophysics Data System (ADS)

    Westgate, J. A.; Preece, S. J.; Froese, D. G.; Schweger, C. E.

    2004-12-01

    Our tephra studies of Late Neogene sediments in interior Alaska and Yukon are motivated by the need to provide a reliable time-stratigraphic framework for on-going palaeoenvironmental projects. Key sites are located in the Fairbanks, Chicken (Alaska) and Klondike (Yukon) goldfields, Old Crow Basin (Yukon), and the numerous bluffs along the Yukon River in Canada and eastern Alaska. Tephra beds are characterized by their field setting, petrography, geochemical composition of glass (majors and traces) and mineral phases (especially FeTi oxides), palaeomagnetic properties, and age (determined mostly by glass-fission-track methods). Two compositional groups are recognized. Type I beds have abundant bubble-wall glass shards and a small crop of crystals with pyroxene > hornblende. Its glass has a rhyolitic to dacitic composition with relatively high FeOt, Cs, Hf and low Al2O3, CaO, and Sr. REE profiles have a well-developed Eu anomaly with La/Yb < 13. Volcanics with this chemical signature are common throughout the Aleutian Alaska Peninsula arc (AAPA), which is, therefore, the presumed source of the type I distal beds. In contrast, type II beds have more abundant crystals (hornblende > > pyroxene) and the rhyolitic glass is mainly in the form of highly inflated pumice with high Al2O3, CaO, and Sr. REE profiles are steep with low heavy REE content along with a very weakly developed Eu anomaly, if present. The type II beds are unusual and have many of the characteristics of adakites, known to occur at Mount Drum and Mount Churchill in the Wrangell volcanic field (WVF), and at Hayes volcano at the northeastern end of the Alaska Peninsula arc. It is likely, therefore, that the source vents for the type II beds in interior Alaska and Yukon are located in or near the WVF. Twenty-five distinctive tephra beds have been recognized in the Gold Hill Loess at Fairbanks and a comparable number have been discovered in the Klondike goldfields, although few beds are common to both

  19. Neogene exhumation of the Internal Rif units (Northern Morocco) evidenced by low- temperature thermochronology

    NASA Astrophysics Data System (ADS)

    Romagny, Adrien; Munch, Philippe; Corsini, Michel; Azdimoussa, Ali; Arnaud, Nicolas; Monié, Patrick; Bonno, Michael; Vazquez, Mercedes

    2013-04-01

    The Rif Chain (Northern Morocco) belongs, with the Betic Cordillera (Southern Spain) to the westernmost part of the Alpine belt. There, the Beni Bousera peridotite massif is exhumed and corresponds to one of the deepest exhumed lithospheric rocks of the chain. Tectono-metamorphic studies showed that the internal units were subjected to very fast exhumation during the late Oligocene - early Miocene interval in relation with a crustal thinning and the Alboran sea rifting (synthesis in Chalouan et al., 2008). However, no data are available for the subsequent period despite that Neogene uplift sediments are well known in the internal domain since the work of Wildi and Wernli (1977) and predicted during the Messinian by thermomecanical modelling (Duggen et al., 2003). We present here for the first time a low temperature thermochronologic study (apatite (U-Th)/He and fission tracks; AHe and AFT) of these rocks in order to date and quantify the Neogene exhumation history of internal units of the Rif Chain. Most AHe ages are comprised between 14.25 ± 0.21 and 21.32 ± 0.31 Ma however some are younger (e.g. 6.92 ± 0.14 Ma). AHe ages are closed to fission tracks ages, indicating a very rapid cooling. Moreover they do not show any clear age-elevation relationship that is consistent with a very rapid cooling. Youngest ages correspond to apatite with low eU concentration and thus are interpreted in terms of lower closure temperatures. We performed thermal modelling with HeFTy software (Ehlers et al., 2005; Ketcham et al., 2007) on fission tracks lengths and He diffusion data as they provide a statistical but more complete temperature-time history for the samples. We also used available 40Ar/39Ar data on biotite and field data to better constrain thermal modelling. Exhumation occurred in two main steps: i) a very rapid cooling between 22 and 17 Ma until rocks reached the top of the PAZ (80 to 60°C) at a rate of ~70 to 120°C/Ma) and ii) a very slow cooling between 17 and 4 Ma

  20. Analysis of Neogene deformation between Beaver, Utah, and Barstow, California: suggestions for altering the extensional paradigm

    USGS Publications Warehouse

    Anderson, R. Ernest; Beard, L. Sue; Mankinen, Edward A.; Hillhouse, John W.

    2013-01-01

    For more than two decades, the paradigm of large-magnitude (~250 km), northwest-directed (~N70°W) Neogene extensional lengthening between the Colorado Plateau and Sierra Nevada at the approximate latitude of Las Vegas has remained largely unchallenged, as has the notion that the strain integrates with coeval strains in adjacent regions and with plate-boundary strain. The paradigm depends on poorly constrained interconnectedness of extreme-case lengthening estimated at scattered localities within the region. Here we evaluate the soundness of the inferred strain interconnectedness over an area reaching 600 km southwest from Beaver, Utah, to Barstow, California, and conclude that lengthening is overestimated in most areas and, even if the estimates are valid, lengthening is not interconnected in a way that allows for published versions of province-wide summations. We summarize Neogene strike slip in 13 areas distributed from central Utah to Lake Mead. In general, left-sense shear and associated structures define a broad zone of translation approximately parallel to the eastern boundary of the Basin and Range against the Colorado Plateau, a zone we refer to as the Hingeline shear zone. Areas of steep-axis rotation (ranging to 2500 km2) record N-S shortening rather than unevenly distributed lengthening. In most cases, the rotational shortening and extension-parallel folds and thrusts are coupled to, or absorb, strike slip, thus providing valuable insight into how the discontinuous strike-slip faults are simply parts of a broad zone of continuous strain. The discontinuous nature of strike slip and the complex mixture of extensional, contractional, and steep-axis rotational structures in the Hingeline shear zone are similar to those in the Walker Lane belt in the west part of the Basin and Range, and, together, the two record southward displacement of the central and northern Basin and Range relative to the adjacent Colorado Plateau. Understanding this province

  1. Neogene and Quaternary ignimbrites in the area of Arequipa, Southern Peru: Stratigraphical and petrological correlations

    NASA Astrophysics Data System (ADS)

    Lebti, Perrine Paquereau; Thouret, Jean-Claude; Wörner, Gerhard; Fornari, Michel

    2006-06-01

    This study focuses on the correlation of four newly identified rhyolitic ignimbrites located around Arequipa, which were previously described as a single ignimbrite sheet: (1) The Río Chili Ignimbrite (ca. 13.33 Ma) crops out in the Río Chili canyon and consists of a cooling unit of non-welded to partially welded, massive, crystal-rich lapilli tuff. This ignimbrite represents the base of the Neogene ignimbrite succession in the Arequipa area and may be stratigraphically equivalent to the 14-13 Ma Huaylillas Ignimbrites in southern Peru. (2) The second voluminous (˜ 20 km 3) and widespread La Joya Ignimbrite sheet (ca. 4.87 Ma) filled the Arequipa depression. Its probable source is now buried underneath the Chachani volcanic complex. The La Joya Ignimbrite covers both the Arequipa Batholith toward the Río Vitor piedmont and also part of the Altiplano to the East and North of the Chachani complex. (3) The Arequipa Airport Ignimbrite (AAI) sheet (ca. 1.6 Ma, ˜18 km 3), the third and latest infill of the Arequipa basin, consists of a lower white, columnar jointed, massive lapilli tuff, indurated by vapor-phase recrystallization, and is overlain by an upper, pink, lithic-rich, non-welded, massive lapilli-tuff. The source of this ignimbrite is also buried underneath the Chachani complex, as indicated by anisotropy of magnetic susceptibility measurements and component lithology. (4) The Yura non-welded pumice-flow deposits (ca. 1.02 Ma, 1.5 km 3) are restricted to the northern and western flanks of the Chachani complex and may correlate with tuffs of the Capillune Formation on the Altiplano. All ignimbrites are high-K calc-alkaline to alkaline rhyolites, which contain variable amounts of plagioclase, biotite, quartz, sanidine, and Fe-Ti oxides. The modal composition of mineral phases and chemistry of amphiboles and biotites are useful for distinguishing the ignimbrites. Specific geochemical fingerprints, such as Sr, Y, Rb, Ba, Cs, REE, and Sr isotopes were effective

  2. Flexural controls on late Neogene basin evolution in southern McMurdo Sound, Antarctica

    NASA Astrophysics Data System (ADS)

    Aitken, Alan R. A.; Wilson, Gary S.; Jordan, Thomas; Tinto, Kirsty; Blakemore, Hamish

    2012-01-01

    The basins of southern McMurdo Sound have evolved under the influence of lithospheric flexure induced by the loads of the Erebus Volcanic Province. To characterise these basins, it is important to investigate the lithosphere's flexural properties, and estimate their influence on basin architecture and evolution. Seismic and gravity data are used to constrain 3D forward modelling of the progressive development of accommodation space within the flexural basins. Elastic plate flexure was calculated for a range of effective elastic thicknesses (T e) from 0.5 to 25 km using a spectral method. Models with low, but nonzero, T e values (2 km < T e < 5 km) produce the best fit to the gravity data, although uncertainty is high due to inaccuracies in the Digital Elevation Model. The slopes of flexural horizons revealed in seismic reflection lines are consistent with this, indicating a T e of 2 km to 5 km, although the depths to these horizons are not consistent, perhaps due to a northwards slope, or step, in the pre-flexural surface. These results indicate that the lithospheric strength of southern McMurdo Sound is significantly less than estimates of the regional average (T e ~ 20 km). This low strength may reflect the weakening effects of the Terror Rift, and perhaps also the Discovery Accommodation Zone, a region of major transverse faulting. A low T e model (T e = 3) for southern McMurdo Sound predicts the development of two discrete flexural depressions, each 2-2.5 km deep. The predicted stratigraphy of the northern basin reflects flexure due to Ross Island, predominantly erupted since ca. 1.8 Ma. The predicted stratigraphy of the southern basin reflects more gradual flexure from ca. 10 Ma to ca. 2 Ma, due to the more dispersed volcanoes of the Discovery subprovince. Collectively, these two basins have the potential to preserve a remarkable stratigraphic record of Antarctic climate change through the late Neogene.

  3. Reprint of: Flexural controls on late Neogene basin evolution in southern McMurdo Sound, Antarctica

    NASA Astrophysics Data System (ADS)

    Aitken, Alan R. A.; Wilson, Gary S.; Jordan, Tom; Tinto, Kirsty; Blakemore, Hamish

    2012-10-01

    The basins of southern McMurdo Sound have evolved under the influence of lithospheric flexure induced by the loads of the Erebus Volcanic Province. To characterise these basins, it is important to investigate the lithosphere's flexural properties, and estimate their influence on basin architecture and evolution. Seismic and gravity data are used to constrain 3D forward modelling of the progressive development of accommodation space within the flexural basins. Elastic plate flexure was calculated for a range of effective elastic thicknesses (Te) from 0.5 to 25 km using a spectral method. Models with low, but nonzero, Te values (2 km < Te < 5 km) produce the best fit to the gravity data, although uncertainty is high due to inaccuracies in the Digital Elevation Model. The slopes of flexural horizons revealed in seismic reflection lines are consistent with this, indicating a Te of 2 km to 5 km, although the depths to these horizons are not consistent, perhaps due to a northwards slope, or step, in the pre-flexural surface. These results indicate that the lithospheric strength of southern McMurdo Sound is significantly less than estimates of the regional average (Te ~ 20 km). This low strength may reflect the weakening effects of the Terror Rift, and perhaps also the Discovery Accommodation Zone, a region of major transverse faulting. A low Te model (Te = 3) for southern McMurdo Sound predicts the development of two discrete flexural depressions, each 2-2.5 km deep. The predicted stratigraphy of the northern basin reflects flexure due to Ross Island, predominantly erupted since ca. 1.8 Ma. The predicted stratigraphy of the southern basin reflects more gradual flexure from ca. 10 Ma to ca. 2 Ma, due to the more dispersed volcanoes of the Discovery subprovince. Collectively, these two basins have the potential to preserve a remarkable stratigraphic record of Antarctic climate change through the late Neogene.

  4. Dated Plant Phylogenies Resolve Neogene Climate and Landscape Evolution in the Cape Floristic Region

    PubMed Central

    2015-01-01

    In the context of molecularly-dated phylogenies, inferences informed by ancestral habitat reconstruction can yield valuable insights into the origins of biomes, palaeoenvironments and landforms. In this paper, we use dated phylogenies of 12 plant clades from the Cape Floristic Region (CFR) in southern Africa to test hypotheses of Neogene climatic and geomorphic evolution. Our combined dataset for the CFR strengthens and refines previous palaeoenvironmental reconstructions based on a sparse, mostly offshore fossil record. Our reconstructions show remarkable consistency across all 12 clades with regard to both the types of environments identified as ancestral, and the timing of shifts to alternative conditions. They reveal that Early Miocene land surfaces of the CFR were wetter than at present and were dominated by quartzitic substrata. These conditions continue to characterize the higher-elevation settings of the Cape Fold Belt, where they have fostered the persistence of ancient fynbos lineages. The Middle Miocene (13–17 Ma) saw the development of perennial to weakly-seasonal arid conditions, with the strongly seasonal rainfall regime of the west coast arising ~6.5–8 Ma. Although the Late Miocene may have seen some exposure of the underlying shale substrata, the present-day substrate diversity of the CFR lowlands was shaped by Pliocene-Pleistocene events. Particularly important was renewed erosion, following the post-African II uplift episode, and the reworking of sediments on the coastal platform as a consequence of marine transgressions and tectonic uplift. These changes facilitated adaptive radiations in some, but not all, lineages studied. PMID:26422465

  5. Superposed Neogene extension, contraction, and salt canopy emplacement in the Yemeni Red Sea

    SciTech Connect

    Heaton, R.C.; Jackson, M.P.A.; Bamahmoud, M.; Nani, A.S.O.

    1996-12-31

    Although the Neogene Red Sea basin has been intensively examined as the type example of a young, narrow ocean, salt tectonics there has been neglected. The Yemeni part of the Red Sea exhibits a wide array of salt tectonic features within a small area. Above the rift section, a middle Miocene evaporite layer, originally 1.5-2 km thick, is the source for autochthonous and allochthonous salt structures. In the middle-late Miocene, evaporite-clastic overburden, halite, and anhydrite layers 50-350 m thick assisted deformation by providing several levels for decollement. Four southward-narrowing tectonics zones trend subparallel to the basin axis. Areas of extension in the easternmost Roller Zone, severe shortening in the central Canopy Zone, and mild shortening in the western Anticline Zone all narrow then pinch out at roughly the same latitude. This convergence suggests that extension and contraction are linked by various salt layers and by transfer structures transecting the tectonic zones. Extension, contraction, and coeval salt canopy emplacement were superposed, mostly between 8 and 5 Ma. The presence of allochthonous salt sheets casts doubt on previous estimates of salt 5 km thick in the southern Red Sea. Fault scarp asperities in the basin floor may have acted as buttresses against which contraction was initiated. The wide variety of salt structures may be due to the weakness and anisotropy of the partially evaporitic overburden and to high geothermal gradients (up to 77{degrees}C/km). These factors enhanced the deformation driven by gravity spreading and sedimentary differential loading.

  6. Compositional Variations of Paleogene and Neogene Tephra From the Northern Izu-Bonin-Mariana Arc

    NASA Astrophysics Data System (ADS)

    Tepley, F. J., III; Barth, A. P.; Brandl, P. A.; Hickey-Vargas, R.; Jiang, F.; Kanayama, K.; Kusano, Y.; Li, H.; Marsaglia, K. M.; McCarthy, A.; Meffre, S.; Savov, I. P.; Yogodzinski, G. M.

    2014-12-01

    A primary objective of IODP Expedition 351 was to evaluate arc initiation processes of the Izu-Bonin-Mariana (IBM) volcanic arc and its compositional evolution through time. To this end, a single thick section of sediment overlying oceanic crust was cored in the Amami Sankaku Basin where a complete sediment record of arc inception and evolution is preserved. This sediment record includes ash and pyroclasts, deposited in fore-arc, arc, and back-arc settings, likely associated with both the ~49-25 Ma emergent IBM volcanic arc and the evolving Ryukyu-Kyushu volcanic arc. Our goal was to assess the major element evolution of the nascent and evolving IBM system using the temporally constrained record of the early and developing system. In all, more than 100 ash and tuff layers, and pyroclastic fragments were selected from temporally resolved portions of the core, and from representative fractions of the overall core ("core catcher"). The samples were prepared to determine major and minor element compositions via electron microprobe analyses. This ash and pyroclast record will allow us to 1) resolve the Paleogene evolutionary history of the northern IBM arc in greater detail; 2) determine compositional variations of this portion of the IBM arc through time; 3) compare the acquired data to an extensive whole rock and tephra dataset from other segments of the IBM arc; 4) test hypotheses of northern IBM arc evolution and the involvement of different source reservoirs; and 5) mark important stratigraphic markers associated with the Neogene volcanic history of the adjacent evolving Ryukyu-Kyushu arc.

  7. The Role of Vapor Recycling on Paleoclimate Records: An Example of the Neogene Expansion of Grasslands

    NASA Astrophysics Data System (ADS)

    Chamberlain, C.; Winnick, M.; Mix, H.; Chamberlain, S. D.; Maher, K.

    2013-12-01

    Vapor recycling by evaporation and transpiration represents a large component of total terrestrial precipitation. Because ET fluxes can change as a result of climate, land use, and ecological changes it is important to assess how these effects influence paleoclimate records. Here we show that the ecological shift from forests to grasslands in the Neogene had a profound affect on the isotopic composition of precipitation on mid-latitude continents. The late Cenozoic was a time of global cooling, increased aridity, and expansion of grasslands. In the last two decades numerous records of oxygen isotopes have been collected to assess plant ecological changes, understand terrestrial paleoclimate, and to determine the surface history of mountain belts. The majority of these δ18O records increase from the mid-Miocene to the Recent. Although this increase has been attributed to multiple causes, we suggest that these records instead record, in part, an increase in aridity and expansion of grasslands in mid-latitude continental regions. We use a non-dimensional isotopic vapor transport model coupled with a soil water isotope model to evaluate the role of vapor recycling and transpiration by different plant functional types. This analysis shows that increased vapor recycling associated with grassland expansion along with bio-mechanistic changes in transpiration by grasses themselves conspire to lower the horizontal gradient in the δ18O of atmospheric vapor as an air mass moves into continental interiors. The resulting signal at a given inland site is an increase in δ18O of precipitation with the expansion of grasslands and increasing aridity, matching the general observed trend in terrestrial Cenozoic δ18O records. Furthermore, this analysis shows that there are limits, a 'hydrostat', to the amount of vapor recycling relative to runoff that will induce this isotopic effect. In the modern climate, this hydrostatic limit occurs at approximately the boundary between forest

  8. Late Neogene paleoceanography of the Sea of Japan based upon diatoms

    SciTech Connect

    Burkle, L.H. )

    1990-06-01

    The authors identified several time intervals apparent late Neogene stepwise paleoenvironmental change in the southern Sea of Japan. The paleoenvironment of the middle Pliocene and older sediments cannot be characterized because the diatom assemblage is made up of a near monospecific ooze (Coscinodiscus marginatus). The middle Pliocene, prior to 2.4 Ma but after the deposition of the C. marginatus ooze, is characterized by warm water diatoms while the late Pliocene (between approximately 2.4 my and the Pliocene/Pleistocene boundary) is characterized by cool water diatoms belonging to an upwelling assemblage. The Tsushima Strait became emergent at approximately 2.4 Ma owing to sea level drop caused by initiation of continental ice build-up on Greenland and by ongoing tectonic uplift across the southern part of Honshu. Diatoms deposited above the Pliocene/Pleistocene boundary suggest that the Tsushima Strait was again submergent and that a branch of the Kuroshio Current flowed into the Sea of Japan. The early Quaternary is characterized by variable preservation and abundance of diatoms with warm water species predominating. They observed changes in both diatom abundance and preservation in upper Quaternary sediments, probably reflecting changes in productivity induced by major glacial/interglacial oscillations. They found no evidence of the complete isolation of the Sea of Japan from the Pacific but their data do suggest, at least, constriction of the Tsushima Strait during maximum glacial episodes. The late Pliocene-Pleistocene interval is characterized by alternating intervals of laminated/homogenous sediments. There are some 30 laminated intervals within the last 300 kyr suggesting that this signal may be the second harmonic of precession. The laminated layers may reflect salinity changes in the southern Sea of Japan.

  9. Neogene-recent sedimentation and development of the Anada-Cilician basin

    SciTech Connect

    Evans, G.; Goeruer, N.; Alavi, N.

    1988-08-01

    The Adana-Cilician basin formed by interaction between the African, Arabian, and Anatolian plates. The basin has been filled asymmetrically from the north and northeast with the northeastern extremity having been completely filled to form the Adana basin beneath the plain of the Seyhan delta. There is no direct borehole evidence from the submarine areas, but coastal boreholes have revealed the presence of at least 6 km of Neogene sediment. The Burdigalian-Serravalian interval is dominated by turbidites and deep-water shales in the center of the Adana basin, with shallow-water clastics and carbonates around the margins. A layer of Messinian evaporite appears to underlie much of the basin. The Serravalian-Pleistocene sedimentation was dominated by shallow marine and terrestrial sedimentation in the Adana basin, the only part known. Today, the Turkish rivers have built up several deltaic complexes. Quaternary sea level and climatic changes and the movement of river mouths have complicated the pattern of shelf sediments. Away from the immediate vicinity of river mouths, the sediments are rich in the remains of macrobenthos and microbenthos, and on tectonically controlled highs coralline algal mounds occur. The sediments of the deeper water areas (/approx/ 1,000 m) show evidence of downslope movement of shelf sediments and anoxic periods, and they contain an impoverished molluscan and foraminiferal fauna. Sediment dispersal appears to have been confined by submarine tectonic barriers. Continuous uplift and faulting along some margins together with flow of evaporites away from the depocenters on the Turkish coast appear to be actively affecting the most recently deposited sediments.

  10. Late Neogene Paleosols and Paleoclimate, Mweiga Area, Mount Kenya, East Africa

    NASA Astrophysics Data System (ADS)

    Mahaney, W. C.; Barendregt, R. W.; Villeneuve, M.; Dostal, J.; Hamilton, T.; Milner, M. W.; Kapran, B.

    2009-05-01

    A sequence of lavas, principally trachyandesites and tephrites of Pliocene age, forming the underpinning of the Mt. Kenya Volcanic Series and long considered to have a Pliocene/Miocene age, were recently dated by Ar/Ar, and from oldest to youngest, gave ages of 5.48, 5.38 and 5.19 Ma. All dated lavas are reversely magnetized. Outcrops of two flows, both with interbedded paleosols, and overlain with loess occur near the Amboni River north of Mweiga, Kenya, along the Nyeri/Thompson Falls Road at 0 degrees 18 minutes S; 37 degrees 48 minutes E. Mineralogy of lavas was determined using microprobe and whole rock chemistry, while sediments and paleosols were analyzed using X-ray diffraction and Energy-Dispersive Spectrometry. Sediments and paleosols were studied for lithologic uniformity, weathering characteristics, and clay mineralogy. Ages of lavas and sediments were determined by Ar/Ar dating and paleomagnetism. The compound paleosols of Late Neogene age depict a long and complex weathering history of rock alteration, leading in part to the formation of claystone and later saw the addition of loessic sediments. The paleosols appear to have been episodically deflated, initially in phase with outpourings of lavas, and later with periods of climatic deterioration when wind systems intensified. Such disjunct weathering histories within multi- component paleosol profiles are similar to those documented on nearby Mount Kenya, where well-weathered lower paleosol horizons developed on Matuyama-age till are overlain by much younger, less weathered paleosols developed on Brunhes-age loess. These first-reported Ar/Ar ages, and paleomagnetism of lavas within the very Late Miocene/Early Pliocene, provide maximum ages for initial weathering rates in a xeric tropical highland climate. Clay mineral analyses of both the weathered bedrock and surface loessic sediments indicate an initial prolonged dry climate during the Lower Pliocene, followed by more humid conditions during the Upper

  11. Dated Plant Phylogenies Resolve Neogene Climate and Landscape Evolution in the Cape Floristic Region.

    PubMed

    Hoffmann, Vera; Verboom, G Anthony; Cotterill, Fenton P D

    2015-01-01

    In the context of molecularly-dated phylogenies, inferences informed by ancestral habitat reconstruction can yield valuable insights into the origins of biomes, palaeoenvironments and landforms. In this paper, we use dated phylogenies of 12 plant clades from the Cape Floristic Region (CFR) in southern Africa to test hypotheses of Neogene climatic and geomorphic evolution. Our combined dataset for the CFR strengthens and refines previous palaeoenvironmental reconstructions based on a sparse, mostly offshore fossil record. Our reconstructions show remarkable consistency across all 12 clades with regard to both the types of environments identified as ancestral, and the timing of shifts to alternative conditions. They reveal that Early Miocene land surfaces of the CFR were wetter than at present and were dominated by quartzitic substrata. These conditions continue to characterize the higher-elevation settings of the Cape Fold Belt, where they have fostered the persistence of ancient fynbos lineages. The Middle Miocene (13-17 Ma) saw the development of perennial to weakly-seasonal arid conditions, with the strongly seasonal rainfall regime of the west coast arising ~6.5-8 Ma. Although the Late Miocene may have seen some exposure of the underlying shale substrata, the present-day substrate diversity of the CFR lowlands was shaped by Pliocene-Pleistocene events. Particularly important was renewed erosion, following the post-African II uplift episode, and the reworking of sediments on the coastal platform as a consequence of marine transgressions and tectonic uplift. These changes facilitated adaptive radiations in some, but not all, lineages studied. PMID:26422465

  12. Stratigraphy of the Neogene Sahabi units in the Sirt Basin, northeast Libya

    NASA Astrophysics Data System (ADS)

    El-Shawaihdi, M. H.; Mozley, P. S.; Boaz, N. T.; Salloum, F.; Pavlakis, P.; Muftah, A.; Triantaphyllou, M.

    2016-06-01

    A revision of the nomenclature of lithostratigraphic units of Neogene strata at As Sahabi, northeast Libya, is presented, based on new fieldwork conducted during 2006-2008. The Sahabi units are correlated across the Ajdabya Sheet (NH 34-6) in northeastern Libya. Major conclusions are: (1) Miocene (Langhian through Messinian) strata are predominantly carbonate and should be referred to as formation "M"; (2) A local unconformity of Miocene (early Messinian) age overlies strata of the formation "M"; (3) This unconformity is overlain by Messinian gypsiferous sand and mud (formerly formation "P" and partially member "T"), which are designated as the "lower member" (gypsiferous) of the Sahabi Formation; (4) The "lower member" is overlain by sand and mud of late Messinian age (formerly partially member "T" and members "U1", "UD", and "U2") in a generally fining-upwards sequence, and are designated as the "upper member" (non-gypsiferous) of the Sahabi Formation; (5) The latest Miocene sand and mud of the "upper member" are capped by an unconformity that is correlated with the regression and desiccation of the Mediterranean Sea during the Messinian Salinity Crisis and with Eosahabi Channel cutting; (6) The unconformity is overlain by Pliocene medium, coarse, and pebbly sands, which are referred to as the Qarat Weddah Formation (formerly Garet Uedda Formation); (7) The Pliocene sands of Qarat Weddah Formation are overlain by carbonate soil (calcrete) of Late Pliocene age, which is referred to as formation "Z" (formerly member "Z"). The major outcome of this study is a revised stratigraphic description and nomenclature of the Sahabi units that helps to provide a formal and unified context for understanding paleontological discoveries in northeastern Libya, which will serve to facilitate a broader correlation of the Sahabi units with their equivalents elsewhere in Africa and in Europe and Asia.

  13. Neogene sinistral transtension along the Hickman fault zone, southeastern Colorado Plateau, New Mexico

    SciTech Connect

    Chamberlin, R.M. )

    1993-04-01

    A north-northeast-trending crustal flaw known as the Hickman fault zone (HFZ) transects the southeastern margin of the Colorado Plateau from Mangas to Grants, New Mexico, a distance of 140 km. Recent reconnaissance mapping of the eastern half of the Quemado 1:100,000 sheet by the author indicates that the southern half of the HFZ is a Neogene oblique-slip zone that displays a normal-sinistral sense of shear. The vertical slip component is 150--200 m and the apparent horizontal component is as much as 120 m. Basaltic debris flows and fluvial deposits of the Miocene Fence Lake Formation are preferentially preserved on the downthrown western side of the HFZ. West of Pietown, Fence Lake strata define an asymmetric synclinal basin. Older northwest-striking Late Oligocene basaltic dikes are locally concealed where they pass under the shallow (200 m) northeast--trending basin. Within the 5-km-wide HFZ, north-trending segments appear to form releasing bends and east-northeast-trending segments appear to form weakly constraining bends, a pattern that implies distributed sinistral shear. Small alluvial basins (incipient half grabens) in the Mangas Mountains are associated with north-striking bends. An east-northeast-trending bend near Pietown is locally defined by an asymmetric anticline; also the Late Oligocene dike trend here bends westerly (counterclockwise) where it crosses the anticlinal axis. Near Hickman (a.k.a. Lehew), the HFZ shows two sinistral offsets of another Late Oligocene dike; cumulative offset is about 120 m.

  14. Neogene paleoelevation of intermontane basins in a narrow, compressional mountain range, southern Central Andes of Argentina

    NASA Astrophysics Data System (ADS)

    Hoke, Gregory D.; Giambiagi, Laura B.; Garzione, Carmala N.; Mahoney, J. Brian; Strecker, Manfred R.

    2014-11-01

    The topographic growth of mountain ranges at convergent margins results from the complex interaction between the motion of lithospheric plates, crustal shortening, rock uplift and exhumation. Constraints on the timing and magnitude of elevation change gleaned from isotopic archives preserved in sedimentary sequences provide insight into how these processes interact over different timescales to create topography and potentially decipher the impact of topography on atmospheric circulation and superposed exhumation. This study uses stable isotope data from pedogenic carbonates collected from seven different stratigraphic sections spanning different tectonic and topographic positions in the range today, to examine the middle to late Miocene history of elevation change in the central Andes thrust belt, which is located immediately to the south of the Altiplano-Puna Plateau, the world's second largest orogenic plateau. Paleoelevations are calculated using previously published local isotope-elevation gradients observed in modern rainfall and carbonate-formation temperatures determined from clumped isotope studies in modern soils. Calculated Neogene basin paleoelevations are between 1 km and 1.9 km for basins that today are located between 1500 and 3400 m elevation. Considering the modern elevation and δ18O values of precipitation at the sampling sites, three of the intermontane basins experienced surface uplift between the end of deposition during the late Miocene and present. The timing of elevation change cannot be linked to any documented episodes of large-magnitude crustal shortening. Paradoxically, the maximum inferred surface uplift in the core of the range is greatest where the crust is thinnest. The spatial pattern of surface uplift is best explained by eastward migration of a crustal root via ductile deformation in the lower crust and is not related to flat-slab subduction.

  15. Gulf of Alaska Cryosphere and Paleoceanography in the Neogene: IODP Expedition 341 Southern Alaska

    NASA Astrophysics Data System (ADS)

    Jaeger, J. M.; Gulick, S. P. S.

    2014-12-01

    Neogene climate reflects the transition into a colder, more variable world dominated by the onset and intensification of major Northern Hemisphere glaciations. Integrated Ocean Drilling Program Expedition 341 recovered a cross-margin transect of pelagic facies from this subarctic, high-nutrient, low-chlorophyll modern setting to glacigenic material from the exhuming coastal mountains. The recovered sedimentary record extends from the late Miocene through the Pleistocene/Holocene. Shipboard results indicate a ~doubling in sediment accumulation rates at ~2.56 Ma at the deep-water distal Site U1417, which is interpreted as the onset of significant glacial coverage in the St. Elias Range after the Pliocene-Pleistocene transition, resulting in the start of deposition in the Surveyor Fan. At all sites, clast-rich mud and/or diamict are prevalent in the Pleistocene, indicating the persistent transport of glacigenic sediment by ice, iceberg or sea-ice rafting. An unanticipated observation is the often sharp transitions between these ice-dominated facies and more biogenic-rich, often bioturbated, muddy lithologies that might be related to increased biological productivity, enhanced nutrient supply, and/or decreased input of terrigenous sediments. All sites contained variable preservation of biosiliceous and calcareous microfossils that indicate dynamic water column productivity and/or variable sediment geochemistry from the late Miocene to the present. At deep-water sites, strong variations in environmentally sensitive planktic foraminifera, radiolarians, and diatoms record alternating warming and cooling intervals during the last 1.2 Ma. At Site U1417, planktic foraminifera and radiolarian taxa abundances indicate cooler conditions in the Pleistocene relative to the Pliocene/late Miocene. Especially high sedimentation rates during the late Pleistocene hold promise for future studies related to suborbital-scale variability in paleoproductivity and glacigenic sedimentation.

  16. Extended stratigraphy, palynology and depositional environments record the initiation of the Himalayan Gyirong Basin (Neogene China)

    NASA Astrophysics Data System (ADS)

    Xu, Ya-Dong; Zhang, Ke-Xin; Wang, Guo-Can; Jiang, Shang-Song; Chen, Fen-Ning; Xiang, Shu-Yuan; Dupont-Nivet, Guillaume; Hoorn, Carina

    2012-01-01

    Here we report new sedimentological and paleontological data from a 603.5 m thick Neogene sequence (Woma section) in the Gyirong Basin, a basin induced by east-west extension in the Himalayas of southern Tibet. We document the conglomeratic Danzengzhukang Formation, at the base of the section, and the overlying finer grained Woma Formation that includes a Hipparion fauna. Based on stratigraphic correlations and earlier thermochronology and magnetostratigraphic results, we bracket the depositional age of this section between 10.8 Ma and 1.7 Ma. Lithology, paleo-current directions and provenance analysis, together with palynological and paleontological data, have revealed three depositional environments for the deposition of the studied section. (1) Alluvial-fan to braided river environments with ESE transport directions (Danzengzhukang Formation, <10.8 to ˜7.2 Ma) were associated with a warm and humid coniferous- and broad-leaved mixed forest. (2) Lacustrine dominated conditions (Lower Woma Formation, ˜7.2 to 3.2 Ma) with WSW transport directions were associated with locally warm and humid environments in the low-lying areas while input from a new source area suggests the presence of a high-altitude, cold and arid deciduous coniferous-leaved forests. (3) A fan delta dominated environment (Upper Woma Formation, 3.2 to >1.7 Ma) with increased denudation and WSW paleo-currents was associated with a deciduous coniferous and broad-leaved mixed forest that suggests an increase in climate variability. Our data indicate that the Gyirong Basin was under overall warm and humid conditions throughout most of its history, in agreement with high-resolution oxygen and carbon isotope data collected from the same section (this issue). We interpret our warm climate in the Gyirong Basin to reflect the prevalence of the monsoonal influence and the distal pollen sources to result from orographic effects.

  17. Gastropoda-Bivalvia Fauna And Neogene-Quaternary Stratigraphy of the Southwest of Dardanelles (Çanakkale-NWAnatolia)

    NASA Astrophysics Data System (ADS)

    Kapan, Sevinç; Kabasakal, Sinem

    2016-04-01

    Gastropoda-Bivalvia Fauna And Neogene-Quaternary Stratigraphy of the Southwest of Dardanelles (Çanakkale-NWAnatolia) Sevinç KAPAN, Sinem KABASAKAL, Çanakkale Onsekiz Mart University, Engineering Faculty, Geological Engineering Department sevinckapan_yesilyurt@hotmail.com In this study, paleontology and stratigraphy of Neogene and Quaternary units around south of the Dardanelles have been examined using Gastropoda and Bivalvia fauna. In the investigation area, the base of the sediments that belongs to Neogene, consist of the volcanics which are formed with basalts, andesites and tuff. Neogene begins unconformity with basal conglomerate which are formed with basalt and tuff gravels. The measurable thickness of the Neogene sediments is approximately 200meters in total. First fossiliferius level which consist of Lymnocardium (Euxinicardium) nobile Sabba has showed similarities with the Pontian (Late Miocene) fauna of the Eastern Paratethys. The existence of Melanopsis and Psidium species indicate that the basin has been brackish water feeding by fresh water in the Early Pliocene. Theodoxus fluviatilis (Linne), Theodoxus (Calvertia) aff. imbricata Brusina, Theodoxus (Calvertia) licherdopoli scriptus (Stefanescu), Viviparus mammatus (Stefanescu), Valvata (Valavata) sulekiana Brusina, Valvata (Cincinna) crusitensis Fontannes, Hydrobia cf grandis Cobalcescu, Hydrobia ventrosa Monfort, Melanopsis (Melanopsis) cf. bergeroni Stefanescu, , Melanopsis (Melanopsis) sandbergeri rumana Tournouer, Melanopsis (Canthidomus) hybostoma anili Taner, Melanopsis (Canthidomus) hybostoma amaradica Fontannes, Melanopsis (Canthidomus) lanceolata Neumayr, Amphimelania fossariformis (Tournouer), Melanoides tuberculata monolithica (Bukowski), Radix (Radix) peregra (Müller), Planorbarius thiollierei (Michaud), Potamida (Potamida) craiovensis craiovensis (Tournouer), Potamida (Potamida) berbestiensis (Fontannes), Unio pristinus davilai Porumbaru, Unio subexquisitus Jatzko, Anadonta zmaji

  18. 3. VIEW OF SOUTHWESTERN APPROACH TO GEORGIA DOT BRIDGE NO. ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    3. VIEW OF SOUTHWESTERN APPROACH TO GEORGIA DOT BRIDGE NO. 111-00060P-00020N - Georgia DOT Bridge No. 111-00060P-00020N, Georgia State Route 60 spur spanning Hempton Creek, Mineral Bluff, Fannin County, GA

  19. 13. REINFORCED CONCRETE SLAB ROOF FROM SOUTHWESTERN EDGE, VIEW TOWARDS ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    13. REINFORCED CONCRETE SLAB ROOF FROM SOUTHWESTERN EDGE, VIEW TOWARDS NORTHEAST. - Glenn L. Martin Company, Titan Missile Test Facilities, Captive Test Stand D-1, Waterton Canyon Road & Colorado Highway 121, Lakewood, Jefferson County, CO

  20. Sequence stratigraphy and systems tract analysis of the Neogene-Quaternary continental margin off the Zambezi delta, Mozambique

    SciTech Connect

    Kolla, V. ); Macurda, D.B. Jr. ); Nelson, H.R. Jr. )

    1991-03-01

    During the Neogene and Quaternary, the Zambezi River built a broad delta-platform from 75 to over 100 km into the Indian Ocean. A regional seismic grid shows numerous discontinuities in the delta platform, slope, and deeper basinal areas. Based on downward shifts of reflection terminations and onlaps at or below shelf edge, more than 25 sequences have been identified. Within the gross Neogene package, the basal section is characterized by aggradation, followed by rapid and significant (oblique) progradation, which is then followed by numerous aggradational-progradation and progradation packages in the upper, younger sections. From recognition of aggradation-progradation patterns and from well information, it appears that the first, significant, and rapid progradation occurred since mid-Miocene. The earliest of the Neogene sequence appears thicker towards south and thinner towards north, opposite of the younger sequences. The number of sequences, their modes of stacking, and thickness distributions reflect relative sea-level changes and the points of sediment input as the Zambezi River shifted in position from south to north in time. The Zambezi passive continental margin, located in the Indian Ocean basin, is a stable platform as opposed to the unstable continental margins off the Mississippi, McKenzie, and Niger deltas and is far from the stable margins that were the basis of the Haq et al. cycle-chart (1987). Thus the Zambezi continental margin provides an independent test case for verification of eustatic cycles and for the evaluation of allogenic (eustatic) versus autogenic (subsidence and delta switching) effects on depositional systems and systems tracts.

  1. The characteristics of neogene sediments and structures in the Siberuang Area (Central Sumatra, Indonesia) based on gravity data

    SciTech Connect

    Santoso, D. )

    1994-07-01

    Neogene sediments in the Siberuang area consist of the Sihapas, Telisa, and Petani formations. The Sihapas Formation is a friable, white to brown sandstone with intercalated claystones, siltstones, and some coal layers. It was deposited in channels or bars of a braided-stream system during early Miocene N4-N8 times. The Telisa Formation, which unconformably overlies the Sihapas Formation, is a calcareous claystone with intercalated glauconitic sands and limestone lenses deposited in a middle to outer neritic environment during middle Miocene N8-N10 times. The Petani Formation is a claystone containing clasts of terrestrial material with some coal lenses and tuffs in the upper part of the section. It is a regressive sequence deposited in an outer neritic environment. These Neogene sediments lie unconformably above the Paleogene Pematang Formation, which is mainly composed of brown conglomerate and conglomeratic sandstones. The Pematang Formation lies unconformably above pre-Tertiary rocks. A Bouguer gravity map processed using a density value of 1.9 gm/cc reveals anomalies with wavelengths of 10 and 15 km. Moving average filtering has been applied to make a regional-residual separation. Map interpretation and modeling along a profile run northeast across the structural trend of the region and indicate a graben-type structure with Neogene sediment thickness increasing from 600 m in the northeast to 2800 m in the southwest. Greatest sediment thickness is attained in the center of the graben, which is delineated by northeast-dipping faults southwest of the area and southwest-dipping faults northeast of the area.

  2. On the Paleogene-Neogene boundary and age of the Alkun Formation in the North Caucasus and Ciscaucasia

    NASA Astrophysics Data System (ADS)

    Filippova, N. Yu.; Beluzhenko, E. V.; Golovina, L. A.

    2015-11-01

    The problems related to age of the lower part of the Caucasian regional stage (Alkun Formation) and Paleogene-Neogene boundary in the North Caucasus and Ciscaucasia are discussed with analysis and generalization of the data on nannoplankton and dinocyst assemblages from Alkun sediments in their different areas. The new data obtained from the section of the Alkun Formation in the stratotypical area of the Caucasian regional stage (valley of the Kuban River middle reaches, Karamurzinskii village), including finds of the index species Triquetrorhabdulus carinatus and typical species of the zonal nannoplankton assemblage, confirm the belonging of Alkun sediments to Zone NN1. The composition and peculiar features of the Karamurzinskii nannoflora and dinocyst assemblages indicate their Neogene age. It is established that the Alkun sediments in the Kuban, North Ossetia, and Belorechensk areas are characterized by similar nannoplankton and dinocyst assemblages, which implies their synchronism in these localities. The dinocyst assemblages from the Alkun Formation exhibit significant similarity with their counterparts from the uppermost part of the "lower Krosno Subformation" and lower part of the "upper Menilite Subformation" of the Ukrainian Carpathians and from lower layers of the "Chernobaevka Formation" of the northern Black Sea region. The analysis of available data reveals that the Paleogene-Neogene boundary in the North Caucasus and Ciscaucasia corresponds to a narrow interval spanning from the upper layers of the Batalpasha Formation and its analogs to the lower layers of the Alkun Formation. Thus, it is shown that the Caucasian regional stage belongs practically in its entire volume, probably except for its basal layers, the age of which needs to be specified, to the lower Miocene. New data on hydrology and bionomy of the basin, vegetation, and climate of the Alkunian time are also considered.

  3. Integrated magnetobiostratigraphy at the Oligocene/Miocene transition in the southwestern Atlantic Ocean (DSDP Leg 72, Hole 516F)

    NASA Astrophysics Data System (ADS)

    Gennari, Rocco; Persico, Davide; Florindo, Fabio; Turco, Elena; Villa, Giuliana

    2014-05-01

    , Paleoceanography, 15, 486-496. Plancq, J., Grossi, V., Henderiks, J., Simon, L. and Mattioli E., 2012. Alkenone producers during late Oligocene-early Miocene revisited, Paleoceanography, 27, PA1202. Pujol, C. and Duprat, J., 1983. Quaternary planktonic foraminifers of the southwestern Atlantic (Rio Grande Rise) Deep Sea Drilling Project Leg 72. In: Barker, P.F., Carlson, R.L., Johnson, D.A., et al. (Eds.), Initial Reports of the Deep Sea Drilling Project, 72, 601-615. Spezzaferri, S., 1994. Planktonic foraminifers biostratigraphy of the Oligocene and lower Miocene in the oceanic record. An overview. Palaeontographia Italica 81, 1-187. Steininger, F.F., Aubry, M.P., Berggren, W.A., Biolzi, M., Borsetti, A.M., Cartlidge, J., Cati, F., Corfield, R., Gelati, R., Iaccarino, S., Napoleone, C., Ottner, F., Rogl, R., Spezzaferri, S., Tateo, F., Villa, G. and Zevenboom, D. 1997. The Global Stratotype Section and Point (GSSP) for the base of the Neogene. Episodes vol. 20, 23-28.

  4. New allocyclic dimensions in a prograding carbonate bank: Evidence for eustatic, tectonic, and paleoceanographic control (late Neogene, Bahamas)

    USGS Publications Warehouse

    Lidz, B.H.; McNeill, D.F.

    1997-01-01

    The deep-sea record, examined recently for the first time in a shallow-depocenter setting, has unveiled remarkable evidence for new sedimentary components and allocyclic complexity in a large, well-studied carbonate bank, the western Great Bahama Bank. The evidence is a composite foraminiferal signature - Paleocene to early Miocene (allogenic or reworked) and late Miocene to late Pliocene (host) planktic taxa, and redeposited middle Miocene shallow benthic faunas. Ages of the oldest and youngest planktic groups range from ??? 66 to ??? 2 Ma. The reworked and redeposited taxa are a proxy for significant sediment components that otherwise have no lithofacies or seismic resolution. The composite signature, reinforced by a distinctive distribution of the reworked and redeposited faunas, documents a much more complex late Neogene depositional system than previously known. The system is more than progradational. The source sequences that supplied the constituent bank-margin grains formed at different water depths and over hundreds of kilometers and tens of millions of years apart. New evidence from the literature and from data obtained during Ocean Drilling Program (OOP) Leg 166 in the Santaren Channel (Bahamas) support early interpretations based on the composite fossil record and provide valuable new dimensions to regional allocyclicity. The middle Miocene taxa were confined to the lower part of the section by the latest Miocene-earliest Pliocene(?) lowstand of sea level. An orderly occurrence of the allogenic taxa is unique to the global reworked geologic record and appears to have been controlled by a combination of Paleogene-early Neogene tectonics at the source, eustatic changes, and late Neogene current activity at the source and across the bank. The allogenic taxa expand the spatial and temporal range of information in the northern Bahamas by nearly an order of magnitude. In essence, some of the major processes active in the region during ??? 64 m.y. of the

  5. Evolution of a trench-slope basin within the Cascadia subduction margin: the Neogene Humboldt Basin, California

    USGS Publications Warehouse

    McCrory, P.A.

    1995-01-01

    The Neogene Humboldt (Eel River) Basin is located along the north-eastern margin of the Pacific Ocean within the Cascadia subduction zone. This sedimentary basin originated near the base of the accretionary prism in post-Eocene time. Subduction processes since that time have elevated strata in the south-eastern portion of the basin above sea level. High-resolution chronostratigraphic data from the onshore portion of the Humboldt Basin enable correlation of time-equivalent lithofacies across the palaeomargin, reconstruction of slope-basin evolution, and preliminary delineation of climatic and tectonic influence on lithological variation. -from Author

  6. Crustal structure of southwestern Saudi Arabia

    USGS Publications Warehouse

    Gettings, M.E.; Blank, H.R.; Mooney, W.D.; Healy, J.H.

    1983-01-01

    The southwestern Arabian Shield is composed of uplifted Proterozoic metamorphic and plutonic rocks. The Shield is bordered on the southwest by Cenozoic sedimentary and igneous rocks of the Red Sea paar and on the east by the Arabian Platform, an area of basin sedimentation throughout Phanerozoic time. The Shield appears to have been formed by successive episodes of island arc volcanism and sea-floor spreading, followed by several cycles of compressive tectonism and metamorphism. An interpretation and synthesis of a deep-refraction seismic profile from the Riyadh area to the Farasan Islands, and regional gravity, aeromagnetic, heat flow, and surface geologic data have yielded a self-consistent regional-scale model of the crust and upper mantle for this area. The model consists of two 20 km-thick layers of crust with an average compressional wave velocity in the upper crust of about 6.3 km/s and an average velocity in the lower. crust of about 7.0 km/s. This crust thins abruptly to less than 20 km near the southwestern end of the profile where Precambrian outcrops abut the Cenozoic rocks and to 8 km beneath the Farasan Islands. The data over the coastal plain and Red Sea shelf areas are fit satisfactorily by an oceanic crustal model. A major lateral velocity inhomogeneity in the crust is inferred about 25 km northeast of Sabhah and is supported by surface geologic evidence. The major velocity discontinuities occur at about the same depth across the entire Shield and are interpreted to indicate horizontal metamorphic stratification of the Precambrian crust. Several lateral inhomogenities in both the upper and lower .crust of the . Shield are interpreted, to indicate bulk compositional variations. The subcrustal portion of the model is composed of a hot, low-density lithosphere beneath the Red Sea which is systematically cooler and denser to the northeast. This model provides a mechanism which explains the observed topographic uplift, regional gravity pattern, heat

  7. Paleocene sequence stratigraphy of southwestern Alabama

    SciTech Connect

    Mancini, E.A.; Tew, B.H.

    1988-09-01

    In southwestern Alabama, the Paleocene consists of about 1300 ft (396 m) of marginal marine and marine terrigenous and carbonate sediments. Based on regional stratigraphic, sedimentologic, and paleontologic data, up to seven unconformity-bounded depositional sequences resulting from relative changes in coastal onlap during the Paleocene are recognized in these strata. These sequences are, in ascending order, the TP1.1a, comprised of the Pine Barren Member of the Clayton Formation; the TP1.1b, comprised of the Turritella rock beds of the Pine Barren and the McBryde Limestone Member of the Clayton Formation, and the clays and marls of the lower member of the Porters Creek Formation; the TP1.2, comprised of the cross-bedded sands of the lower member and the Matthews Landing Marl Member of the Porters Creek Formation, and Oak Hill Member of the Naheola Formation; the TP1.3, comprised of the Coal Bluff Marl Member of the Naheola Formation; the TP2.1, comprised of the Gravel Creek Sand, Ostrea thirsae beds, and Grampian Hills Members of the Nanafalia Formation, and the lower beds of the Tuscahoma Sand; the TP2.2, comprised of the Greggs Landing Marl Member and the middle beds of the Tuscahoma Sand; and the TP2.3, comprised of the Bells Landing Marl Member and the upper beds of the Tuscahoma Sand.

  8. Early Cambrian hydrocarbon potential in Southwestern Ohio

    SciTech Connect

    Sfara, R.M.; Benjamin, H.R.; Wolfe, P.J.

    1995-09-01

    A sedimentary basin, inferred to be of Early Cambrian age, has been recently identified in southwestern Ohio. A well drilled into this basin in 1926 penetrated 404 m of sedimentary rocks below the Middle Cambrian Mount Simon Sandstone. This is the only well in Ohio to have penetrated limestone below the Mt. Simon Sandstone. Since 1992 Wright State University has gathered about 35 km of seismic data in this area. The seismic data suggest that these strata dip south into a large basin. The seismic character of the limestone interval at the well extends to a thickness of at least 1000 m. In addition, material underlying the limestone has reflection characteristics similar to the Late Proterozoic Middle Run Sandstone that exists about 40 km to the southwest. The surface on which Mount Simon Sandstone was deposited appears to be a mature karst surface and there was a natural gas show at this horizon. An oil show existed in an 8 m thick arkose within the limestone. All of the limestone encountered in the well was rich in organic material. Since there were gas and oil shows in the old well and the material appears younger than the Middle Run Sandstone, we feel this basin has hydrocarbon production potential.

  9. Southwestern USA Drought over Multiple Millennia

    NASA Astrophysics Data System (ADS)

    Salzer, M. W.; Kipfmueller, K. F.

    2014-12-01

    Severe to extreme drought conditions currently exist across much of the American West. There is increasing concern that climate change may be worsening droughts in the West and particularly the Southwest. Thus, it is important to understand the role of natural variability and to place current conditions in a long-term context. We present a tree-ring derived reconstruction of regional-scale precipitation for the Southwestern USA over several millennia. A network of 48 tree-ring chronologies from California, Nevada, Utah, Arizona, New Mexico, and Colorado was used. All of the chronologies are at least 1,000 years long. The network was subjected to data reduction through PCA and a "nested" multiple linear regression reconstruction approach. The regression model was able to capture 72% of the variance in September-August precipitation over the last 1,000 years and 53% of the variance over the first millennium of the Common Era. Variance captured and spatial coverage further declined back in time as the shorter chronologies dropped out of the model, eventually reaching 24% of variance captured at 3250 BC. Results show regional droughts on decadal- to multi-decadal scales have been prominent and persistent phenomena in the region over the last several millennia. Anthropogenic warming is likely to exacerbate the effects of future droughts on human and other biotic populations.

  10. Southwestern Pine Forests Likely to Disappear

    SciTech Connect

    McDowell, Nathan

    2015-12-21

    A new study, led by Los Alamos National Laboratory's Nathan McDowell, suggests that widespread loss of a major forest type, the pine-juniper woodlands of the Southwestern U.S., could be wiped out by the end of this century due to climate change, and that conifers throughout much of the Northern Hemisphere may be on a similar trajectory. New results, reported in the journal Nature Climate Change, suggest that global models may underestimate predictions of forest death. McDowell and his large international team strove to provide the missing pieces of understanding tree death at three levels: plant, regional and global. The team rigorously developed and evaluated multiple process-based and empirical models against experimental results, and then compared these models to results from global vegetation models to examine independent simulations. They discovered that the global models simulated mortality throughout the Northern Hemisphere that was of similar magnitude, but much broader spatial scale, as the evaluated ecosystem models predicted for in the Southwest.

  11. Southwestern Pine Forests Likely to Disappear

    ScienceCinema

    McDowell, Nathan

    2016-06-29

    A new study, led by Los Alamos National Laboratory's Nathan McDowell, suggests that widespread loss of a major forest type, the pine-juniper woodlands of the Southwestern U.S., could be wiped out by the end of this century due to climate change, and that conifers throughout much of the Northern Hemisphere may be on a similar trajectory. New results, reported in the journal Nature Climate Change, suggest that global models may underestimate predictions of forest death. McDowell and his large international team strove to provide the missing pieces of understanding tree death at three levels: plant, regional and global. The team rigorously developed and evaluated multiple process-based and empirical models against experimental results, and then compared these models to results from global vegetation models to examine independent simulations. They discovered that the global models simulated mortality throughout the Northern Hemisphere that was of similar magnitude, but much broader spatial scale, as the evaluated ecosystem models predicted for in the Southwest.

  12. Neogene magnetostratigraphy and rock magnetic study of the Kashi Depression, NW China: significance for Neotectonic deformation in SW Tianshan Mountains

    NASA Astrophysics Data System (ADS)

    Huang, B.; Qiao, Q.

    2014-12-01

    The Chinese Southwest Tianshan Mountains lies in the actively deforming part of the India-Asia collision system. To better understand its sedimentation, denudation, and mountain building history; we conduct a detailed magnetostratigraphic study on the Dashankou section in the Kashi Depression of the Tarim Basin. Paleomagnetic samples were collected from 985 sites of a 3187m-thick section from the exposed Neogene sediments. Magnetostratigraphy is correlating with polarity chrons C5r.3r to C2An.1n dated between ~12.4 and ~3.0 Ma on the GTS2012 geomagnetic polarity time scale. The substantial increase in accumulation rate in the Dashankou section at ~6.7 Ma may be the signature of a pulse of rapid uplift comparable to that observed in the northern Chinese Tianshan Mountains. We argue that climatic changes may have modulated the sedimentary record during the Neogene times, but they don't appear to be a dominant control on sediment accumulation between ~7.0 and ~2.58 Ma. On the other hand, the basal age of the Xiyu Conglomerates studied here is ~3.2 Ma, and the accumulation rate of the Late Pliocene conglomerates was mostly controlled by both tectonics and climatic cooling. Our results indicate that the present high relief of the Tianshan Mountains is the result of dominant phases of uplift at ~6.7 Ma and the Early Pleistocene.

  13. Detailed record of the Neogene Sr isotopic evolution of seawater from DSDP Site 590B. [Deep Sea Drilling Project

    SciTech Connect

    DePaolo, D.J.

    1986-02-01

    A detailed study of strontium isotope variations in Neogene marine carbonate sediments from Deep Sea Drilling Project Site 590B, using techniques that allow the /sup 87/Sr//sup 86/Sr ratio to be determined to better than +/- 0.000 01, gives a high-resolution record of the Sr isotopic evolution of seawater. The data show that the rate of change of the marine /sup 87/Sr//sup 86/Sr ratio has varied significantly even on time scales as short as 1 m.y. Periods of particularly rapid growth appear to follow major marine regressions and probably reflect an increase in the delivery of radiogenic Sr from the continents coupled with a decreased submarine carbonate dissolution rate (greater carbonate compensation depth). Periods of relatively slowly changing /sup 97/Sr//sup 86/Sr follow major marine transgressions. On the basis of correlations with the marine oxygen isotope record and the times of major continental glacier growth, it is inferred that the effects of sea-level variations are modified by climatic factors that affect the intensity of continental weathering and runoff. The effects of sea-floor generation rate variations are not discernible for the Neogene. The maximum attainable stratigraphic resolution using Sr isotopes is between 0.1 and 2 m.y. for this time period. 24 references.

  14. Seismic evidence for Neogene and active shortening offshore of Lebanon (Shalimar cruise)

    NASA Astrophysics Data System (ADS)

    Carton, H.; Singh, S. C.; Tapponnier, P.; Elias, A.; Briais, A.; Sursock, A.; Jomaa, R.; King, G. C. P.; DaëRon, M.; Jacques, E.; Barrier, L.

    2009-07-01

    Lebanon, located on a 160-km-long transpressional bend of the left-lateral Levant (Dead Sea) fault system (LFS), has been the site of infrequent but large earthquakes, including one submarine, tsunamigenic event. The main objective of the Shalimar marine survey was to characterize and map active deformation offshore of Lebanon using a range of geophysical techniques, particularly seismic reflection profiling. The cruise results clearly establish the presence of young submarine thrust faults and folds and clarify the structure of this part of the Levant margin. A submarine fold belt, bounded by thrusts and lateral ramps and extending up to 30 km from the shoreline, is interpreted as the foreland thrust system of the actively growing Mount Lebanon range. There is no large fault extending into the Levant basin toward Cyprus, which indicates that thrusting only absorbs local transpression resulting from the Lebanese restraining bend. Both the Miocene and Plio-Quaternary sedimentary sequences are affected by shortening, with landward dipping blind thrusts and associated growth strata. The presence of the Messinian evaporites creates complex deformation patterns, including normal faults due both to folding accommodation and to gravity spreading, all well imaged in the seismic reflection profiles. Because the evaporite layer acts as a décollement level, shortening extends farther out seaward through a series of thrust imbricates or duplexes. The strongest shortening, observed between Beirut and Batroun, decreases toward the south between Saida and Tyre. North of Tripoli, the passive margin is not affected by Neogene deformation and is well preserved. We propose that since the Miocene, the northward propagating LFS interacted with margin structures inherited from the Mesozoic rifting phase and was deviated along the more rigid oceanic crust flooring the Levant basin, a process which led to the formation of the Lebanese restraining bend of the LFS and consequently to the

  15. Neogene extension and volcanism in the Kunlun fault zone Northern Tibet

    NASA Astrophysics Data System (ADS)

    Jolivet, M.; Brunel, M.; Seward, D.; Malavieille, J.; Roger, F.; Leyreloup, A.; Arnaud, N.

    2003-04-01

    basin. Yin A., Kapp P.A., Murphy M.A., Manning C.E., Harrison T.M., Grove M., Lin D., Xi-Guang D., Cun-Ming W., 1999, Significant late Neogene east-west extension in northern Tibet. Geology, Vol.27, N°9, pp. 787-790. Kidd W.S.F., and Molnar P., 1988, Quaternary and active faulting observed on the 1985 Academia Sinica Royal Society Geotraverse of Tibet. Phil. Trans. R. Soc. Lond., Vol. A 327, pp. 337-363.

  16. Neogene deformation of thrust-top Rzeszów Basin (Outer Carpathians, Poland)

    NASA Astrophysics Data System (ADS)

    Uroda, Joanna

    2015-04-01

    The Rzeszów Basin is a 220 km2 basin located in the frontal part of Polish Outer Carpathians fold-and-thrust belt. Its sedimentary succession consist of ca. 600 m- thick Miocene evaporates, litoral and marine sediments. This basin developed between Babica-Kąkolówka anticline and frontal thrust of Carpathian Orogen. Rzeszów thrust-top basin is a part of Carpathian foreland basin system- wedge-top depozone. The sediments of wedge -top depozone were syntectonic deformed, what is valuable tool to understand kinematic history of the orogen. Analysis of field and 3D seismic reflection data showed the internal structure of the basin. Seismic data reveal the presence of fault-bend-folds in the basement of Rzeszów basin. The architecture of the basin - the presence of fault-releated folds - suggest that the sediments were deformed in last compressing phase of Carpathian Orogen deformation. Evolution of Rzeszów Basin is compared with Bonini et.al. (1999) model of thrust-top basin whose development is controlled by the kinematics of two competing thrust anticlines. Analysis of seismic and well data in Rzeszów basin suggest that growth sediments are thicker in south part of the basin. During the thrusting the passive rotation of the internal thrust had taken place, what influence the basin fill architecture and depocentre migration opposite to thrust propagation. Acknowledgments This study was supported by grant No 2012/07/N/ST10/03221 of the Polish National Centre of Science "Tectonic activity of the Skole Nappe based on analysis of changes in the vertical profile and depocentre migration of Neogene sediments in Rzeszów-Strzyżów area (Outer Carpathians)". Seismic data by courtesy of the Polish Gas and Oil Company. References Bonini M., Moratti G., Sani F., 1999, Evolution and depocentre migration in thrust-top basins: inferences from the Messinian Velona Basin (Northern Apennines, Italy), Tectonophysics 304, 95-108.

  17. Late Neogene exhumation patterns in Taranaki Basin (New Zealand): Evidence from offset porosity-depth trends

    NASA Astrophysics Data System (ADS)

    Armstrong, Phillip A.; Allis, Richard G.; Funnell, Robert H.; Chapman, David S.

    1998-12-01

    Taranaki Basin, New Zealand, is located adjacent to the Australian-Pacific Plate boundary where the tectonic regime changes from dominantly subduction-related to the north to transpression-related along the Alpine Fault to the south. During the Neogene, burial and exhumation varied extensively, in both time and space, in response to subsidence and uplift along this evolving plate boundary zone. The basin can be divided into two regions: (1) the Western Platform outside the plate boundary deformation zone where no uplift nor exhumation has occurred and (2) the Eastern Mobile Belt, which lies inside the deformation zone and has been variably uplifted and exhumed. Exhumation magnitudes for sedimentary deposits of the basin are estimated from offset porosity-depth trends. The analysis is based on correlating sonic log travel times with compensated density logs, permitting sonic travel time to be used as a proxy for porosity. Twelve Western Platform wells are used to define a standard exponential porosity-depth trend with an extrapolated surface porosity of 50% and an exponential decay factor of 2265 m, valid for mudstone/shale sections spanning a depth range of 300-3000 m. This curve is a calibration curve against which offset porosity-depth trends from wells in exhumed regions can be compared to determine apparent exhumation amounts. Porosity-depth trends for 43 Eastern Mobile Belt wells are offset 0-2800 m shallower relative to the Western Platform trend but generally are parallel to it. In the southern region of the Eastern Mobile Belt, net exhumation amounts, which are the sum of the porosity-depth trend offset and depth to unconformity, range from 850 to 3000 m; most of this exhumation occurred on discrete contractional structures in late Miocene to early Pliocene time, probably associated with an increased rate of convergence across the Alpine Fault system to the south. In the eastern region of the Eastern Mobile Belt, net exhumation progressively increases from

  18. Early Neogene unroofing of the Sierra Nevada de Santa Marta along the Bucaramanga -Santa Marta Fault

    NASA Astrophysics Data System (ADS)

    Piraquive Bermúdez, Alejandro; Pinzón, Edna; Bernet, Matthias; Kammer, Andreas; Von Quadt, Albrecht; Sarmiento, Gustavo

    2016-04-01

    Plate interaction between Caribbean and Nazca plates with Southamerica gave rise to an intricate pattern of tectonic blocks in the Northandean realm. Among these microblocks the Sierra Nevada de Santa Marta (SNSM) represents a fault-bounded triangular massif composed of a representative crustal section of the Northandean margin, in which a Precambrian to Late Paleozoic metamorphic belt is overlain by a Triassic to Jurassic magmatic arc and collateral volcanic suites. Its western border fault belongs to the composite Bucaramanga - Santa Marta fault with a combined left lateral-normal displacement. SE of Santa Marta it exposes remnants of an Oligocene marginal basin, which attests to a first Cenoizoic activation of this crustal-scale lineament. The basin fill consists of a sequence of coarse-grained cobble-pebble conglomerates > 1000 m thick that unconformably overlay the Triassic-Jurassic magmatic arc. Its lower sequence is composed of interbedded siltstones; topwards the sequence becomes dominated by coarser fractions. These sedimentary sequences yields valuable information about exhumation and coeval sedimentation processes that affected the massif's western border since the Upper Eocene. In order to analyse uplifting processes associated with tectonics during early Neogene we performed detrital zircon U-Pb geochronology, detrital thermochronology of zircon and apatites coupled with the description of a stratigraphic section and its facies composition. We compared samples from the Aracataca basin with analog sequences found at an equivalent basin at the Oca Fault at the northern margin of the SNSM. Our results show that sediments of both basins were sourced from Precambrian gneisses, along with Mesozoic acid to intermediate plutons; sedimentation started in the Upper Eocene-Oligocene according to palynomorphs, subsequently in the Upper Oligocene a completion of Jurassic to Cretaceous sources was followed by an increase of Precambrian input that became the dominant

  19. The Neogene Redbeds of Iceland - a High-Latitude Terrestrial Paleoclimate Monitor Driven by Chemical Weathering

    NASA Astrophysics Data System (ADS)

    Riishuus, M. S.; Bird, D. K.

    2012-12-01

    Chemical weathering of tephra and aeolian dust of basaltic composition produces clays and iron oxide/hydroxide minerals preserved in reddened layers referred to as redbeds, boles or paleosols. We propose that the extent of weathering of Neogene redbeds in Iceland and the isotopic composition of structurally bound water in associated weathering clay preserve records of high-latitude paleoclimatic and hydrologic conditions. In support we present whole-rock geochemistry and smectite D/H compositions of redbed horizons from Iceland for comparative analysis with global paleoclimate trends and local independent proxy data. Smectite δD values of 35 basaltic tephras in Iceland (~15-2 Ma) display a general decrease in δD compositions from -110 to -105 ‰ at ~15-13 Ma to -115 to -118 ‰ at ~3-2 Ma which correlates well with the global cooling trend from the Middle Miocene Climatic Optimum (17-15 Ma) to present day. Furthermore, the extent of weathering expressed by the Chemical Index of Weathering increases from 40-50 at 2-3 Ma to 80-90 at 15-16 Ma suggesting enhanced chemical weathering rates during the warmer climate conditions. The weathering extent of modern andosols in Iceland is temperature-dependant and allows construction of a paleo-climate proxy [1]. Application of this proxy suggests that mean annual temperatures (MATs) increased from ~0°C at ~2 Ma to ~9°C at 15-16 Ma in general agreement with independent local proxy data. The δD values of paleo meteoric waters in Iceland, estimated using a smectite-water fractionation factor and model MATs, decrease from -41 ‰ at 15-16 Ma (9°C) to -45 ‰ at 2 Ma (0°C). The paleo meteoric water compositions are increasingly enriched in deuterium relative to present day meteoric water in Iceland (δD ≤ -50 ‰). This is in agreement with global cooling since Middle Miocene toward ice-dominated conditions with greater equator-to-pole temperature contrasts, affecting the distillation process between ocean, atmosphere and

  20. Emergence of the Namib Desert During the Neogene, and Correlations With Global Palaeoclimate Changes

    NASA Astrophysics Data System (ADS)

    Segalen, L.; Renard, M.; Lee-Thorp, J. A.; Senut, B.; Pickford, M.

    2004-12-01

    The Namib is one of the oldest known desert systems, hence its formation and maintenance are of considerable regional and global importance. Fluctuations in Atlantic climate and oceanic circulation patterns directly affect the ecology of the Namibian desert, and the entire South African west coast area, on a variety of timescales. The discovery of mammalian fossils and ratite eggshells has provided a biochronology, while the ratite eggshells have allowed stable oxygen and carbon isotope studies of this material to pinpoint the plant dietary base of these birds and to provide clues about changing environments through time. The results of the existing multidisciplinary study provide a sequence showing that during the lower Miocene, prior to 17 Ma, (fluviatile environments, terraces of the Proto-Orange river) a tropical/subtropical climate existed. The onset of aridification is correlated with appearance of the first aeolianites in the basal middle Miocene period. In the Southern Namib, cross-stratification in aeolianites represent the lower slipface of crescent dunes. The predominant northeast-northwest azimuths of the cross-bedded strata indicate deposition under a prevailing southerly wind regime. This regime remained in place throughout the Neogene. The aeolianites of the Northern Namib present different lithologies from those in the south: sand sheet deposits rich in cemented roots (stabilization phase of the arid system), cross-stratification of complex dunes and deflation surfaces related to water flowing from nearby inselbergs. The azimuths of these cross-bedded strata indicate deposition under westerly/southerly winds and also easterly and northeasterly winds during the Late Miocene (at present the bergwinds produce similar conditions). Isotopic data from the ratite eggshells shows advance of C4 grasses in this region at the end of the Miocene, and emergent differences in the plant cover of the southern versus northern sectors. Eggshell carbon isotope

  1. Chemical and isotopic characteristics of hot springs along the along the Neogene Malawi rift.

    NASA Astrophysics Data System (ADS)

    Atekwana, E. A.; Tsokonombwe, G. W.; Elsenbeck, J.; Wanless, V. D.; Atekwana, E. A.

    2015-12-01

    We measured the concentrations of major ions and dissolved inorganic carbon (DIC) and the stable isotopes of carbon (δ13CDIC), hydrogen (δD) and oxygen (δ18O) of hot springs along the Neogene Malawi rift. We compared the results with those of streams and a cold spring. We aimed to assess the hot springs for evidence of addition of mantle mass, specifically water and carbon and (2) determine the processes that control the chemical and isotopic evolution of the hot springs. Understanding the source(s) of heat for the springs and if the chemical and isotopic characteristics show evidence of mantle processes is an important goal of the Project for Rift Initiation, Development and Evolution (PRIDE). The temperature of the hot springs ranged from 35 to 80 ºC. High temperature anomalies are observed between latitudes 10 to 11, 12 to 13 and 15 to 16 degrees south along the rift axis. The δD and δ18O for the cold spring, hot springs and streams had a similar range, were positively correlated and lie on the trend of the local meteoric water line. We suggest negligible contribution of water from a connate or magmatic source and limited oxygen exchange from water-rock interaction or CO2 exchange from deep sedimentary carbonates. The DIC concentrations of the hot springs are higher (5 to 61 mg C/L) than those of streams (2 to 28 mg C/L) indicating addition of carbon to the DIC pool during the circulation of some springs. The range in the δ13CDIC of the hot springs (-17 to -8‰) is broader and lower compared to streams (-12 to -5‰) due to addition of carbon with a δ13CDIC of -15‰ to the spring water during circulation. Our results indicate that (1) the source of water for the hot springs is meteoric, (2) the hot springs have not experienced extensive water-rock interaction due to fast circulation suggesting highly permeable fault zones, (3) the source of carbon in the DIC of the hot springs is mostly CO2(g) from the soil zone and (4) the springs are heated by normal

  2. Miocene Evaporites in the Intermountain Tuzluca -Iǧdir Neogene Basin, Eastern Turkey

    NASA Astrophysics Data System (ADS)

    Ayyıldız, T.; Varol, B.; Sözeri, K.; Karakaş, Z.

    2012-04-01

    The study area, which continues into Armenia south of Yerevan as Aras/Araxes or Hoktemberian Basin, is located within the Eastern Turkish High Plateau lying east of the intersection point of the North and East Anatolian faults at Karlıova, where folds, thrust and strike-slip faults, and large-scale extensional fractures related to a shortening regime have been developing as a result of continent-continent collision during the Neotectonic episode. Simultaneously with the shortening phase, structural basins developed such as intermountane. Detailed mapping of the Neogene deposits (Early Oligocene - Middle to early Late Miocene) in the eastern part of this basin studied allowed the recognition of four successive sedimentary units composed of fluvial, fluvio-deltaic, lake and saline pan. The depositional units were ended by intensive volcanic activity started in the Late Miocene epoch. Pre-evaporitic stage, some levels with siliciclastic and carbonate might be important for petroleum potential, which consists of bituminous mudstone (TOC: % 0.67 - 6.14; Tmax: 422 - 4620C; HI: 37-54). Evaporites are mainly represented by bedded/banded halite that were formed as four separate layers (10-40 m thick) intersected by red siliciclastic deposits with single selenitic gypsum and cubic halite crystals. Bedded gypsum was formed as marginal evaporites, laterally interfingering with the halite layers. On the other hand, it was precipitated as final evaporite deposits on the top of the halite-dominated succession, indicating upward increasing value of SO4 to Cl, probably resulted from a climatic changing leading to transition from saline pan to sulphate lake. As based on the different kinds of precipitation, the evaporite succession includes following 1) evaporitic red mudstone inner-sabkha mud flats; 2) bedded/banded halite and mudstone with organic matter in inner-sabkha salt pan; 3) interdigitated gypsum in marginal sabkha; 4) sealed gypsum in sulphate lake / floodwater sabkha

  3. Heterogeneous sources of marlstone in a piggy-back basin: the Neogene Lopare basin in Dinarides

    NASA Astrophysics Data System (ADS)

    Grba, Nenad; Neubauer, Franz; Šajnović, Aleksandra; Jovančićević, Branimir

    2014-05-01

    The chemical composition of marlstones is commonly not used to investigate to provenance of the sedimentary basin fill because of variable dilution by authigenic carbonate and the assumed uniformity of the clay fraction. Here, we report geochemical compositions of marlstone from the Neogene Lopare basin in Internal Dinarides, which have an unusual chemical composition reflecting at least two different sources. The Lopare basin formed as a piggy-back basin on top of the growing Dinaric orogenic wedge. Much of its Miocene evolution, this basin represented a partly hypersaline lake in a warm climate likely formed during the Miocene Climatic Optimum during Early Miocene. Several lithofacies of marlstone reflect basin center deposits and the chemical composition could be considered as well mixed from external siliciclastic input (clay fraction) and internal carbonate precipitation. Sandstone layers are very thin and are not considered here. A total of 46 samples from two boreholes POT-3 (depth to 344 m) and POT-1 (depth to 193 m) were selected for geochemical investigation. The contents of major, minor and trace including rare earth elements were determined by inductively coupled plasma atomic emission spectrometry (ICP-AES). The qualitative composition of the mineral part was determined by means of X-ray diffractometry. The main chemical features of the Lopare basin marlstone are variable but high contents of most metals like Fe (5.36 ± 1.05 wt%), Cr (215 ± 34 ppm), Ni (183 ± 36 ppm), Pb (173 ± 43 ppm), but also of some alkalies like Li (340 ± 123 ppm). Particularly the heavy metal contents like Cr, Ni, Fe are much higher than for average continental mudstones (e.g., Taylor and McLennan, 1985). These contrasting compositions may result from two geochemically different sources: (1) Ophiolites (oceanic source) occurring in the neighborhood are responsible for high Cr, Ni, Fe contents, while (2) the increased alkali contents (e.g., Li; continental source) likely

  4. Preliminary stratigraphic and paleomagnetic results from Neogene basins across the Anatolian Plateau (Turkey).

    NASA Astrophysics Data System (ADS)

    Lucifora, Stella; Cifelli, Francesca; Mazzini, Ilaria; Cosentino, Domenico; Mattei, Massimo; Cipollari, Paola; Gliozzi, Elsa; Palolo Cavinato, Gian

    2010-05-01

    An integrated paleomagnetic and stratigraphic study on Neogene basins across the Anatolian Plateau was carried out. This study is developed within the VAMP (Vertical Anatolian Movement Project), an interdisciplinary project aimed to the recent tectonic evolution of the central Anatolian Plateau. The studied areas are located in southern Turkey (Adana, Mut and Ermenek basins) and in northern Turkey (Kazan, Çankiri, Kastamonu, Boyabat and Sinop basins). For paleomagnetic analyses we sampled 1062 standard cylindrical samples from 13 stratigraphic sections, and 746 samples for paleontological analysis were taken from the same sections. AMS (Anisotropy of Magnetic Susceptibility), magnetic mineralogy and paleomagnetic polarity data are presented together with the results of the integrated stratigraphic analyses. In the Southern Turkey basins preliminary results show the diffuse presence of authigenic iron sulphides, together with magnetite, as main magnetic carriers. In these sections the iron-sulphides Characteristic Natural Magnetization (ChRM) component is characterized by inconsistent polarity record, suggesting that iron-sulphides have a late diagenetic origin. Conversely, magnetite bearing sediments show more reliable results in term of magnetic polarity interpretations. Preliminary stratigraphic and paleomagnetic results from the southern margin of the plateau allow us both to refine the stratigraphy for the late Miocene of the Adana Basin and to better constrain the age of the youngest marine deposits of the Mut and Ermenek basins. In the late Miocene of the Adana Basin evidence of the Messinian salinity crisis led to a new stratigraphic framework specially for the Messinian-Pliocene interval. Thick fluvial conglomerates from the uppermost Messinian deposits of the Adana Basin, which could be linked to the activation of the southern margin of the plateau, allow us to constrain at about 5.4 Ma the uplift of the central Anatolian Plateau. On the other hand, the

  5. Late Neogene to Quaternary environmental changes in the Antarctic Peninsula region: evidence from drift sediments

    NASA Astrophysics Data System (ADS)

    Hillenbrand, Claus-Dieter; Ehrmann, Werner

    2005-02-01

    Clay-mineral composition and biogenic opal content in upper Miocene to Quaternary drift sediments recovered at two Ocean Drilling Program (ODP) sites from the continental rise in the Bellingshausen Sea had been analyzed in order to reconstruct the climatic and glacial history of the Antarctic Peninsula. The clay mineral composition at both sites is dominated by smectite, illite, and chlorite, and alternates between a smectite-enriched and a chlorite-enriched assemblage throughout the last 9.3 my. The spatial distribution of clay minerals in Holocene sediments west of the Antarctic Peninsula facilitates the identification of particular source areas, and thus the reconstruction of transport pathways. The similarity to clay mineral variations reported from upper Quaternary sequences suggests that the short-term clay-mineralogical fluctuations in the ODP cores reflect glacial-interglacial cyclicity. Thus, repeated ice advances and retreats in response to a varying size of the Antarctic Peninsula ice cap are likely to have occurred throughout the late Neogene and Quaternary. The clay minerals in the drift sediments exhibit only slight long-term variations, which are caused by local changes in glacial erosion and in supply of source rocks, rather than by major climatic changes. The opal records at the ODP sites are dominated by long-term variations since the late Miocene. We infer that the opal content in the drift sediments, although it is influenced by dissolution in the water column and the sediment column and by the burial with lithogenic detritus, provides a signal of paleoproductivity. Because the annual sea-ice coverage is regarded as the main factor controlling biological productivity, the opal signal helps to reconstruct paleoceanographic changes in the Bellingshausen Sea. Slightly enhanced opal deposition during the late Miocene indicates slightly warmer climatic conditions in the Antarctic Peninsula area than at present. During the early Pliocene, enhanced

  6. Air permeametry on outcrop analogues: a composite image of the Neogene aquifer, Belgium.

    NASA Astrophysics Data System (ADS)

    Rogiers, B.; Beerten, K.; Smekens, T.; Huysmans, M.; Gedeon, M.; Mallants, D.; Batelaan, O.; Dassargues, A.

    2012-04-01

    Saturated hydraulic conductivity (Ks) is one of the most important parameters determining groundwater flow and contaminant transport in both unsaturated and saturated porous media. While several well-established laboratory methods exist for determining Ks, in-situ measurements of this parameter remain very complex. Since the 50's, and increasingly from the late 80's, air permeameters are being used effectively as an indirect method to determine Ks on outcrop sediments. In this paper, the heterogeneity within outcrop sediments that are analogues for the Neogene aquifer hydrostratigraphic units in northern Belgium is studied with a hand-held air permeameter. This aquifer, representing a major groundwater source, consists of several sandy geological units from Miocene to Pleistocene age with a marine to continental origin. Moreover, it plays an important role in the Belgian deep geological radwaste disposal studies, and is the subject of a safety assessment for a future low-level radwaste surface repository. To characterise the variability between and within the different lithostratigraphical aquifer units, 804 air permeability measurements at cm-scale were performed on several outcrops that are analogues for the sandy aquifer sediments and a highly heterogeneous aquitard. Equivalent meter-scale Ks tensors were calculated numerically through the law of flow conservation to obtain the vertical anisotropy factor. The off-diagonal tensor components were shown to be negligible. To validate the air permeametry data, 18 additional constant head permeameter tests on 100 cm3 cores and 27 grain size analyses based Ks assessments were performed on outcrop material. The comparison indicates that hand-held air permeameters are very effective and useful tools to characterise the magnitude of hydraulic conductivity, as well as it's small-scale variability and anisotropy, on a broad range of sediment types. However, a comparison with data from a previous borehole campaign on similar

  7. Neogene kinematic history of Nazca-Antarctic-Phoenix slab windows beneath Patagonia and the Antarctic Peninsula

    NASA Astrophysics Data System (ADS)

    Breitsprecher, Katrin; Thorkelson, Derek J.

    2009-01-01

    The Patagonian slab window is a subsurface tectonic feature resulting from subduction of the Nazca-Antarctic spreading-ridge system (Chile Rise) beneath southern South America. The geometry of the slab window had not been rigorously defined, in part because of the complex nature of the history of ridge subduction in the southeast Pacific region, which includes four interrelated spreading-ridge systems since 20 Ma: first, the Nazca-Phoenix ridge beneath South America, then simultaneous subduction of the Nazca-Antarctic and the northern Phoenix-Antarctic spreading-ridge systems beneath South America, and the southern Phoenix-Antarctic spreading-ridge system beneath Antarctica. Spreading-ridge paleo-geographies and rotation poles for all relevant plate pairs (Nazca, Phoenix, Antarctic, South America) are available from 20 Ma onward, and form the mathematical basis of our kinematic reconstruction of the geometry of the Patagonia and Antarctic slab windows through Neogene time. At approximately 18 Ma, the Nazca-Phoenix-Antarctic oceanic (ridge-ridge-ridge) triple junction enters the South American trench; we recognize this condition as an unstable quadruple junction. Heat flow at this junction and for some distance beneath the forearc would be considerably higher than is generally recognized in cases of ridge subduction. From 16 Ma onward, the geometry of the Patagonia slab window developed from the subduction of the trailing arms of the former oceanic triple junction. The majority of the slab window's areal extent and geometry is controlled by the highly oblique (near-parallel) subduction angle of the Nazca-Antarctic ridge system, and by the high contrast in relative convergence rates between these two plates relative to South America. The very slow convergence rate of the Antarctic slab is manifested by the shallow levels achieved by the slab edge (< 45 km); thus no point on the Antarctic slab is sufficiently deep to generate "normal" mantle-derived arc-type magmas

  8. Evaporite deposition and coeval volcanism in the Fortuna Basin (Neogene, Murcia, Spain)

    NASA Astrophysics Data System (ADS)

    Playà, Elisabet; Gimeno, Domingo

    2006-06-01

    The Neogene basins of the Eastern Betic Mountains were placed in a marginal position with respect to the deep Mediterranean basin during the Tortonian to the Messinian. They contain thick gypsum-anhydrite formations resulting from the Upper Miocene salinity crisis. The evaporitic sedimentation reached its maximum extension and stratigraphic complexity in the Fortuna basin, which belongs to this geological setting. Five stratigraphic units are distinguished in the Fortuna basin: (1) Lower Gypsum, (2) Chicamo Gypsum, (3) Chicamo diatomitic-evaporitic cycles, (4) Ribera Gypsum and (5) Rambla Salada Gypsum units. Some of these units occur locally, whereas others can be laterally correlated with those of the Archena-Mula, Guadalentín corridor and Lorca basins. Most of the gypsum units consist of nodular-laminated secondary gypsum, however, primary selenitic, laminated gypsarenites and fine-grained microlenticular burrowed gypsum lithofacies are also present. The evaporite units can also be characterized by the geochemical composition of the gypsum (the sulphur and oxygen of the sulphate and the strontium isotopes), which display a wide range of values. The extreme values indicate precipitation from Tertiary marine brines, or from meteoric waters that recycled Triassic sulphate anion and additional non-marine contributions from country rocks and hydrothermal solutions. The intermediate values are attributed to mixing between seawater and non-marine parent brines. The Fortuna basin contains several outcrops of volcanic to subvolcanic igneous lamproites (Cabezos Negros, Derramadores, El Tale). These lamproites, the so-called fortunites, crop out as individual domic volcanoes with lava flows (Cabezos Negros) or as intrusive subvertical dikes (Derramadores, El Tale). There is good evidence of several magma-sediment interactions that produced macro and microglobular peperitic lithofacies in the Fortuna basin. A peperite is produced when two liquids (a hot magma and a

  9. Genesis of economic relevant fresh groundwater resources in Pleistocene/ Neogene aquifers in Nam Dinh (Red River Delta, Vietnam).

    NASA Astrophysics Data System (ADS)

    Wagner, F.; Ludwig, R. R.; Noell, U.; Hoang, H. V.; Pham, N. Q.; Larsen, F.; Lindenmaier, F.

    2012-04-01

    In the Southern Red River Delta (Nam Dinh Province, Vietnam), a local lens of low saline pore water of high quality has been identified in unconsolidated Pleistocene and Neogene aquifers, which are regionally known to contain brackish and saline pore waters. Since the 1990ies, ongoing overexploitation of the fresh groundwater results in decreasing GW heads up to 0.6 m/a and the development of a regional abstraction cone. The presented study focuses on distribution and genesis of fresh and saline pore waters and reflects the results in frame of the regional hydrogeological context. Observations of the geological structure and groundwater dynamics combined with hydrochemical and isotopic studies suggest adjacent Triassic hard rock aquifers as the major source for fresh Pleistocene and Neogene groundwater. Salinization status in the economically most relevant Pleistocene aquifer has been studied based on archive and new hydrochemical and geophysical data. Own hydrochemical field studies as well as laboratory measurements of the specific resistivity of dry sediment samples allow the translation of induction logging data from existing monitoring wells into vertical pore water salinity profiles. This approach suggests the regional occurrence of saline pore water in shallow Holocene sediments in the working area, as confirmed by pore water studies in Hoan et al. (2010). Interpretation of induction logging and stable isotope data suggest vertical diffusion of saline pore water in shallow Holocene sediments as a source for high saline pore water in deeper aquifers. Analytical diffusion modeling for a period of 3000 years confirms that vertical diffusion of Holocene paleo-sea water can explain saline pore water in Pleistocene and Neogene aquifers in a stagnant environment. The constant influx of fresh groundwater from adjacent Triassic hard rocks results in flushing of the primary Pleistocene and Neogene pore water and inhibits the infiltration of saline water from marine

  10. Wrench tectonics control on Neogene-Quaternary sedimentation along the Mid-Hungarian Mobile Belt

    NASA Astrophysics Data System (ADS)

    Pogacsas, Gyorgy; Juhász, Györgyi; Mádl-Szőnyi, Judit; Simon, Szilvia; Lukács, Szilveszter; Csizmeg, János

    2010-05-01

    The Neogene Pannonian basin is underlain by a large orogenic collage which is built up by several tectonostratigraphic terrains. The basement of the Pannonian Basin became imbricate nappes during the Cretaceous Alpine collision. Nappes of Late Cretaceous in age have been proven below the Great Hungarian Plain (Grow et al 1994). The boundary of the two main terrains, the northwestern ALCAPA (Alpine-Carpathian-Pannonian) and the southeastern TISZA, is the Mid-Hungarian Mobile Belt. It is the most significant neotectonic zone of the Pannonian Basin. The structural analysis of the middle section of the Mid-Hungarian Mobile Belt was carried out on a 120km x 50km area, between the Danube and the Tisza river, on the basis of interpretation of seismic data. The structural analysis of the Neogene-Quaternary sediments was supported by sequence stratigraphic interpretation of seismic, well log and core-sample data. Regional seismic profiles were both oriented in the dip direction, which highlights sediment supply routes into the basin, and strike-oriented. The studied segment of the Mid-Hungarian Mobile Belt consists of several long (some ten kilometres long) strike slip fault zones. The offset lengths of the individual strike slipe faults varies between a few and a dozens of kilometres. Activity along the Mid-Hungarian Mobile Belt can be characterised by four periods, the size and shape of facies zones of each development period were controlled by tectonics: 1. During the early Miocene, the ALPACA moved eastward, bounded by sinistral strike-slipe system along its northern side and dextral strike-slipe fault system along its contact with the Southern Alps and the TISZA terrain. The largest movement took part during the Ottnangian-Karpatian (19-16.5 Ma). The TISZA unit moved northeastward over the remnant Carpathian Flysch Basin (Nemcok et al 2006). These terrains movements resulted in right lateral, convergent wide wrench along the Mid-Hungarian Mobile Belt. The ALPACA