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Sample records for active tectonic setting

  1. Active tectonics

    SciTech Connect

    Not Available

    1986-01-01

    This study is part of a series of Studies in Geophysics that have been undertaken for the Geophysics Research Forum by the Geophysics Study Committee. One purpose of each study is to provide assessments from the scientific community to aid policymakers in decisions on societal problems that involve geophysics. An important part of such assessments is an evaluation of the adequacy of current geophysical knowledge and the appropriateness of current research programs as a source of information required for those decisions. The study addresses our current scientific understanding of active tectonics --- particularly the patterns and rates of ongoing tectonic processes. Many of these processes cannot be described reasonably using the limited instrumental or historical records; however, most can be described adequately for practical purposes using the geologic record of the past 500,000 years. A program of fundamental research focusing especially on Quaternary tectonic geology and geomorphology, paleoseismology, neotectonics, and geodesy is recommended to better understand ongoing, active tectonic processes. This volume contains 16 papers. Individual papers are indexed separately on the Energy Database.

  2. Coseismic landslides reveal near-surface rock strength in a high-relief tectonically active setting

    USGS Publications Warehouse

    Gallen, Sean F; Clark, Marin K; Godt, Jonathan W.

    2014-01-01

    We present quantitative estimates of near-surface rock strength relevant to landscape evolution and landslide hazard assessment for 15 geologic map units of the Longmen Shan, China. Strength estimates are derived from a novel method that inverts earthquake peak ground acceleration models and coseismic landslide inventories to obtain material proper- ties and landslide thickness. Aggregate rock strength is determined by prescribing a friction angle of 30° and solving for effective cohesion. Effective cohesion ranges are from 70 kPa to 107 kPa for 15 geologic map units, and are approximately an order of magnitude less than typical laboratory measurements, probably because laboratory tests on hand-sized specimens do not incorporate the effects of heterogeneity and fracturing that likely control near-surface strength at the hillslope scale. We find that strength among the geologic map units studied varies by less than a factor of two. However, increased weakening of units with proximity to the range front, where precipitation and active fault density are the greatest, suggests that cli- matic and tectonic factors overwhelm lithologic differences in rock strength in this high-relief tectonically active setting.

  3. The Central-Western Mediterranean: Anomalous igneous activity in an anomalous collisional tectonic setting

    NASA Astrophysics Data System (ADS)

    Lustrino, Michele; Duggen, Svend; Rosenberg, Claudio L.

    2011-01-01

    plate (Sardinia, Corsica, Balearic Islands, Kabylies, Calabria, Peloritani Mountains). The bulk of igneous activity in the central-western Mediterranean is believed to have tapped mantle 'wedge' regions, metasomatized by pressure-related dehydration of the subducting slabs. The presence of subduction-related igneous rocks with a wide range of chemical composition has been related to the interplay of several factors among which the pre-metasomatic composition of the mantle wedges (i.e., fertile vs. refractory mineralogy), the composition of the subducting plate (i.e., the type and amount of sediment cover and the alteration state of the crust), the variable thermo-baric conditions of magma formation, coupled with variable molar concentrations of CO 2 and H 2O in the fluid phase released by the subducting plates are the most important. Compared to classic collisional settings (e.g., Himalayas), the central-western Mediterranean area shows a range of unusual geological and magmatological features. These include: a) the rapid formation of extensional basins in an overall compressional setting related to Africa-Europe convergence; b) centrifugal wave of both compressive and extensional tectonics starting from a 'pivotal' region around the Gulf of Lyon; c) the development of concomitant Cenozoic subduction zones with different subduction and tectonic transport directions; d) subduction 'inversion' events (e.g., currently along the Maghrebian coast and in northern Sicily, previously at the southern paleo-European margin); e) a repeated temporal pattern whereby subduction-related magmatic activity gives way to magmas of intraplate geochemical type; f) the late-stage appearance of magmas with collision-related 'exotic' (potassic to ultrapotassic) compositions, generally absent from simple subduction settings; g) the relative scarcity of typical calcalkaline magmas along the Italian peninsula; h) the absence of igneous activity where it might well be expected (e.g., above the

  4. The Physics of a Volcanic System: What is the Actual Role Played by Tectonic Setting in Controlling Volcanic Activity?

    NASA Astrophysics Data System (ADS)

    Canon-Tapia, E.

    2005-12-01

    Modern text-books commonly explain volcanic activity as a direct consequence of plate tectonics, overlooking the different scales characteristic of both types of processes. By acknowledging such differences, however, it is possible to envisage a model of a volcanic system that is based in the same principles of hydrostatics established by Blaise Pascal over 300 yrs ago. Such principles allow us to estimate the local conditions required for the occurrence of volcanism at a given location highlighting the importance of the rock strength and the density difference between melt and its surroundings. This model shows that the minimum thickness of the zone of partial melting in the mantle (or seismically defined Low Velocity Zone) that is required to feed volcanic activity might range from 5 to over 100 km, but also that under certain circumstances a rock strength < 200 MPa may suffice to keep magma trapped at depth whereas in other cases a strength > 600 MPa will not suffice to stop magma ascent resulting in volcanic activity at the surface. Consequently, the model of volcanism developed here explains why is that a given LVZ may lead to volcanic activity in some places whereas a completely identical LVZ may not result in volcanic activity in a different location. Consequently, this model provides a general framework that allows us to better understand the actual role played by tectonic setting in controlling volcanism at a planetary scale.

  5. Earth's glacial record and its tectonic setting

    NASA Astrophysics Data System (ADS)

    Eyles, N.

    1993-09-01

    Glaciations have occurred episodically at different time intervals and for different durations in Earth's history. Ice covers have formed in a wide range of plate tectonic and structural settings but the bulk of Earth's glacial record can be shown to have been deposited and preserved in basins within extensional settings. In such basins, source area uplift and basin subsidence fulfill the tectonic preconditions for the initiation of glaciation and the accomodation and preservation of glaciclastic sediments. Tectonic setting, in particular subsidence rates, also dictates the type of glaciclastic facies and facies successions that are deposited. Many pre-Pleistocene glaciated basins commonly contain well-defined tectonostratigraphic successions recording the interplay of tectonics and sedimentation; traditional climatostratigraphic approaches involving interpretation in terms of either ice advance/retreat cycles or glacio-eustatic sea-level change require revision. The direct record of continental glaciation in Earth history, in the form of classically-recognised continental glacial landforms and "tillites", is meagre; it is probable that more than 95% of the volume of preserved "glacial" strata are glacially-influenced marine deposits that record delivery of large amounts of glaciclastic sediment to offshore basins. This flux has been partially or completely reworked by "normal" sedimentary processes such that the record of glaciation and climate change is recorded in marine successions and is difficult to decipher. The dominant "glacial" facies in the rock record are subaqueous debris flow diamictites and turbidites recording the selective preservation of poorly-sorted glaciclastic sediment deposited in deep water basins by sediment gravity flows. However, these facies are also typical of many non-glacial settings, especially volcanically-influenced environments; numerous Archean and Proterozoic diamictites, described in the older literature as tillites, have no

  6. Hydrothermal fluids circulation and travertine deposition in an active tectonic setting: Insights from the Kamara geothermal area (western Anatolia, Turkey)

    NASA Astrophysics Data System (ADS)

    Brogi, Andrea; Alçiçek, M. Cihat; Yalçıner, Cahit Çağlar; Capezzuoli, Enrico; Liotta, Domenico; Meccheri, Marco; Rimondi, Valentina; Ruggieri, Giovanni; Gandin, Anna; Boschi, Chiara; Büyüksaraç, Aydin; Alçiçek, Hülya; Bülbül, Ali; Baykara, Mehmet Oruç; Shen, Chuan-Chou

    2016-06-01

    Coexistence of thermal springs, travertine deposits and tectonic activity is a recurring feature for most geothermal areas. Although such a certainty, their relationships are debated mainly addressing on the role of the tectonic activity in triggering and controlling fluids flow and travertine deposition. In this paper, we present the results of an integrated study carried out in a geothermal area located in western Anatolia (Turkey), nearby the well-known Pamukkale area (Denizli Basin). Our study focused on the relationships among hydrothermal fluids circulation, travertine deposition and tectonic activity, with particular emphasis on the role of faults in controlling fluids upwelling, thermal springs location and deposition of travertine masses. New field mapping and structural/kinematics analyses allowed us to recognize two main faults systems (NW- and NE-trending), framed in the Neogene-Quaternary extensional tectonic evolution of western Anatolia. A geo-radar (GPR) prospection was also provided in a key-area, permitting us to reconstruct a buried fault zone and its relationships with the development of a fissure-ridge travertine deposit (Kamara fissure-ridge). The integration among structural and geophysical studies, fluids inclusion, geochemical, isotopic data and 230 Th/238 U radiometric age determination on travertine deposits, depict the characteristics of the geothermal fluids and their pathway, up to the surface. Hydrological and seismological data have been also taken in account to investigate the relation between local seismicity and fluid upwelling. As a main conclusion we found strict relationships among tectonic activity, earthquakes occurrence, and variation of the physical/chemical features of the hydrothermal fluids, presently exploited at depth, or flowing out in thermal springs. In the same way, we underline the tectonic role in controlling the travertine deposition, making travertine (mainly banded travertine) a useful proxy to reconstruct the

  7. Studies in geophysics: Active tectonics

    NASA Technical Reports Server (NTRS)

    1986-01-01

    Active tectonics is defined within the study as tectonic movements that are expected to occur within a future time span of concern to society. Such movements and their associated hazards include earthquakes, volcanic eruptions, and land subsidence and emergence. The entire range of geology, geophysics, and geodesy is, to some extent, pertinent to this topic. The needs for useful forecasts of tectonic activity, so that actions may be taken to mitigate hazards, call for special attention to ongoing tectonic activity. Further progress in understanding active tectonics depends on continued research. Particularly important is improvement in the accuracy of dating techniques for recent geologic materials.

  8. Denudation rates of tropical mountain regions : What is the proportion of chemical weathering vs. mechanical denudation in a tectonically active settings?

    NASA Astrophysics Data System (ADS)

    Roelandt, C.; Vanacker, V.; Goddéris, Y.; Kaplan, J. O.

    2009-04-01

    Denudation rates of tropical mountain regions in tectonically active settings, such as the northern Andes, are known to be high. Rivers draining the northern Andes are important sources of sediment and nutrients to the low-lying basins and oceans. The largest part of the total denudation rates in these environments is often considered to be mechanical denudation, given their steep topography, young geology and humid and warm climate. In this study, we try to better understand the linkage between physical denudation and chemical weathering for degraded catchments with shallow, eroded soils. We selected a limited number of case-studies from the Ecuadorian Andes being characterized by humid climate, steep topography, and intensive land use. For these catchments, the total denudation rates are derived from cosmogenic isotope concentrations in riverborne quartz (Vanacker et al, 2007, Geology). The B-WITCH model (Roelandt et al. submitted, GBC) is used to quantify chemical weathering rates. The results of this study will allow us to get a better insight in the linkage between chemical and physical denudation rates for an active tectonic setting. Besides, the data will give the opportunity to explore the effect of land use change on chemical weathering rates.

  9. Africa's Megafans and Their Tectonic Setting

    NASA Technical Reports Server (NTRS)

    Wilkinson, M. J.; Burke, K.

    2016-01-01

    Megafans are a really extensive continental sediment bodies, fluvially derived, and fan-shaped in planform. Only those >80 km long were included in this study. Africa's megafans were mapped for purposes of both comprehensive geomorphic description and as a method of mapping by remote sensing large probable fluvial sediment bodies (we exclude sediment bodies deposited in well defined, modern floodplains and coastal deltas). Our criteria included a length dimension of >80 km and maximum width >40 km, partial cone morphology, and a radial drainage pattern. Visible and especially IR imagery were used to identify the features, combined with topographic SRTM data. We identified 99 megafans most of which are unstudied thus far. Their feeder rivers responsible for depositing megafan sediments rise on, and are consequent drainages oriented down the slopes of the swells that have dominated African landscapes since approximately 34 Ma (the high points in Africa's so-called basin-and-swell topography [1]). Most megafans (66%) have developed along these consequent rivers relatively near the swell cores, oriented radially away from the swells. The vast basins between the swells provide accommodation for megafan sediment wedges. Although clearly visible remotely, most megafans are inactive as a result of incision by the feeder river (which then no longer operates on the fan surface). Two tectonic settings control the location of Africa's megafans, 66% on swell flanks, and 33% related to rifts. (i) Swell flanks Most megafans are apexed relatively near the core of the parent swell, and are often clustered in groups: e.g., six on the west and north flanks of the Hoggar Swell (Algeria), seven on the north and south flanks of the Tibesti Swell (Libya-Chad borderlands), twelve on the west flank of the Ethiopian Swell, four on the east flank of the East African Swell (Kenya), Africa's largest, and eight around Angola's Bié Swell (western Zambia, northern Namibia). A cluster of possible

  10. Red Sea Kinematics in Relation to the Regional Tectonics Setting

    NASA Astrophysics Data System (ADS)

    Alotaibi, T.; Furlong, K. P.

    2015-12-01

    The Red sSea extensional system started approximately 22+3 Ma. Although, there is evidence that lithospheric weakening and associated incipient extension may have taken place since 30 Ma. There is oceanic crust found in the southern part of the rift, while the northern-most part still involves continental stretching. Meantime magnetic anomalies have been observed for the southern rift, the northern rift is characterized by several deeps where magnetic anomalies have been observed as well as an indication of the transition from continental to oceanic rifting. GPS stations along the Red Sea are consistent with kinematics implied from the magnetic anomalies - an opening rate in the southern part of ~ 15 mm/yr relative to Eurasia fixed while the opening rate in the is ~8 mm/yr. This significant decreasing of the opening rate towards the north implies complexity within the Red Sea extensional system.Our purpose here is to place the Red Sea extensional kinematics within the regional tectonics context by combining constraints on the rate or style of extension within the Red Sea with tectonic activities on the adjacent continental regions. To accomplish this, we will model the extensional kinematics through time by comparing recent kinematics based on the geophysical observations with ones that based on geological observations. In terms of present-day geophysical observations, we have GPS and magnetic anomalies data, and crustal and lithospheric thickness. Geological observations primarily come from stratigraphic and structural data sets.Our overall target is to construct a tectonic model that links the timing of the change in the style and extensional rate with the tectonic activities in Afar, Gulf of Aden, Zagros, Dead Sea fault and Anatolian region.

  11. Active tectonics of the Andes

    NASA Astrophysics Data System (ADS)

    Dewey, J. F.; Lamb, S. H.

    1992-04-01

    Nearly 90 mm a -1 of relative plate convergence is absorbed in the Andean plate-boundary zone. The pattern of active tectonics shows remarkable variations in the way in which the plate slip vector is partitioned into displacement and strain and the ways in which compatibility between different segments is solved. Along any traverse across the plate-boundary zone, the sum of relative velocities between points must equal the relative plate motion. We have developed a kinematic synthesis of displacement and strain partitioning in the Andes from 47°S to 5°N relevant for the last 5 Ma based upon: (1) relative plate motion deduced from oceanic circuits giving a roughly constant azimuth between 075 and 080; (2) moment tensor solutions for over 120 crustal earthquakes since 1960; (3) structural studies of deformed Plio-Pleistocene rocks; (4) topographic/geomorphic studies; (5) palaeomagnetic data; and (6) geodetic data. We recognize four neotectonic zones, with subzones and boundary transfer zones, that are partitioned in different ways. These zones are not coincident with the 'classic' zones defined by the presence or absence of a volcanic chain or differences in finite displacements and strains and tectonic form; the long-term segmentation and finite evolution of the Andes may not occur in constantly defined segments in space and time. In Segment 1 (47°-39°S), the slip vector is partitioned into roughly orthogonal Benioff Zone slip with large magnitude/large slip-surface earthquakes and both distributed dextral shear giving clockwise rotations of up to 50° and dextral slip in the curved Liquine-Ofqui Fault System giving 5°-10° of anticlockwise fore-arc rotation. In Segment 2 (39°-20°S), the slip vector is partitioned into Benioff Zone slip roughly parallel with the slip vector, Andean crustal shortening and a very small component of dextral slip, including that on the Atacama Fault System. Between 39° and 34°S, a cross-strike dextral transfer, which deflects

  12. Tectonic setting of the Windermere Supergroup revisited

    SciTech Connect

    Ross, G.M. )

    1991-11-01

    Neo-Proterozoic (< 780 Ma) rocks in western North America compose a regionally persistent stratigraphic succession that contains basal sedimentary and volcanic rocks that accumulated during active faulting. In the Canadian Cordillera, the synrift component is overlain by a thick succession that includes shelf, shelf-edge, and basinal strata and implies substantial postrift subsidence. Although fragmentary in nature due to the effects of sub-cambrian erosion, when reconstructed the Canadian stratigraphic record is similar in thickness, facies, and lateral persistence to the overlying Cambrian-Ordovician passive margin. The neo-Proterozoic record of western North America is thus interpreted as a passive-margin succession, rather than a simple rift, which predates a younger rift that resulted in widespread early Paleozoic passive-margin sedimentation. If correct, this may imply that break-up of western Laurentia was a neo-Proterozoic phenomenon rather than early Paleozoic.

  13. Late Pleistocene-Holocene uplift driven terrace formation and climate-tectonic interplay from a seismically active intraplate setting: An example from Kachchh, Western India

    NASA Astrophysics Data System (ADS)

    Prizomwala, S. P.; Das, Archana; Chauhan, G.; Solanki, T.; Basavaiah, N.; Bhatt, Nilesh; Thakkar, M. G.; Rastogi, B. K.

    2016-07-01

    terrace, we reported a minimum uplift rate of 1.04 mm/a for the eastern KMF during the Late Pleistocene-Holocene period, hinting seismically active nature of the KMF during this period. The terrace formation in the eastern Northern Hill Range is mostly regulated by tectonic uplifts along the KMF.

  14. Active tectonics and human survival strategies

    NASA Astrophysics Data System (ADS)

    King, Geoffrey; Bailey, Geoffrey; Sturdy, Derek

    1994-10-01

    Tectonic movements continuously remould the surface of Earth in response to plate motion. Yet such deformation is rarely taken into account when assessing landscape change and its impact on human land use, except perhaps as an occasional hazard to human life or a temporary disruption in the longer term patterns of human history. However, active tectonics also create and sustain landscapes that can be beneficial to human survival, forming a complex topography of potentially fertile sedimentary basins enclosed by mountain barriers that can facilitate the control and explotation of food resources, especially animal prey. We discuss the tectonic history of northwest Greece and show how the Paleolithic sites of the region are located to take advantage of tectonically created features at both a local and a regional scale. We suggest that the association of significant concentrations of early Paleolithic sites with tectonically acitve regions is not coincidental and that on the longer time spans of human biological evolution, active tectonics has been an important selective agent contributing to the development of the human species as an intelligent predator.

  15. Tectonic signatures on active margins

    NASA Astrophysics Data System (ADS)

    Hogarth, Leah Jolynn

    High-resolution Compressed High-Intensity Radar Pulse (CHIRP) surveys offshore of La Jolla in southern California and the Eel River in northern California provide the opportunity to investigate the role of tectonics in the formation of stratigraphic architecture and margin morphology. Both study sites are characterized by shore-parallel tectonic deformation, which is largely observed in the structure of the prominent angular unconformity interpreted as the transgressive surface. Based on stratal geometry and acoustic character, we identify three sedimentary sequences offshore of La Jolla: an acoustically laminated estuarine unit deposited during early transgression, an infilling or "healing-phase" unit formed during the transgression, and an upper transparent unit. The estuarine unit is confined to the canyon edges in what may have been embayments during the last sea-level rise. The healing-phase unit appears to infill rough areas on the transgressive surface that may be related to relict fault structures. The upper transparent unit is largely controlled by long-wavelength tectonic deformation due to the Rose Canyon Fault. This unit is also characterized by a mid-shelf (˜40 m water depth) thickness high, which is likely a result of hydrodynamic forces and sediment grain size. On the Eel margin, we observe three distinct facies: a seaward-thinning unit truncated by the transgressive surface, a healing-phase unit confined to the edges of a broad structural high, and a highly laminated upper unit. The seaward-thinning wedge of sediment below the transgressive surface is marked by a number of channels that we interpret as distributary channels based on their morphology. Regional divergence of the sequence boundary and transgressive surface with up to ˜8 m of sediment preserved across the interfluves suggests the formation of subaerial accommodation during the lowstand. The healing-phase, much like that in southern California, appears to infill rough areas in the

  16. Using earthquake-triggered landslides as a hillslope-scale shear strength test: Insights into rock strength properties at geomorphically relevant spatial scales in high-relief, tectonically active settings

    NASA Astrophysics Data System (ADS)

    Gallen, Sean; Clark, Marin; Godt, Jonathan; Lowe, Katherine

    2016-04-01

    The material strength of rock is known to be a fundamental property in setting landscape form and geomorphic process rates as it acts to modulate feedbacks between earth surface processes, tectonics, and climate. Despite the long recognition of its importance in landscape evolution, a quantitative understanding of the role of rock strength in affecting geomorphic processes lags our knowledge of the influence of tectonics and climate. This gap stems largely from the fact that it remains challenging to quantify rock strength at the hillslope scale. Rock strength is strongly scale dependent because the number, size, spacing, and aperture of fractures sets the upper limit on rock strength, making it difficult to extrapolate laboratory measurements to landscape-scale interpretations. Here we present a method to determine near-surface rock strength at the hillslope-scale, relying on earthquake-triggered landslides as a regional-scale "shear strength" test. We define near-surface strength as the average strength of rock sample by the landslides, which is typically < 10 m. Based on a Newmark sliding block model, which approximates slope stability during an earthquake assuming a material with frictional and cohesive strength, we developed a coseismic landslide model that is capable of reproducing statistical characteristics of the distribution of earthquake-triggered landslides. We present results from two well-documented case-studies of earthquakes that caused widespread mass-wasting; the 2008 Mw 7.9 Wenchuan Earthquake, Sichuan Province, China and the 1994 Mw. 6.8 Northridge Earthquake, CA, USA. We show how this model can be used to determine near-surface rock strength and reproduce mapped landslide patterns provided the spatial distribution of local hillslope gradient, earthquake peak ground acceleration (PGA), and coseismic landsliding are well constrained. Results suggest that near-surface rock strength in these tectonically active settings is much lower than that

  17. Ancient Tectonic and Volcanic Activity in the Tharsis Region

    NASA Astrophysics Data System (ADS)

    Werner, S. C.; Kronberg, P.; Hauber, E.; Grott, M.; Steinberger, B.; Torsvik, T. H.; Neukum, G.

    The two topographically dominating volcanic provinces on Mars are the Tharsis and the Elysium regions, situated close to the equator on the dichotomy boundary between the heavily cratered (older) highlands and the northern lowlands (about 100 degrees apart). The regions are characterized by volcanoes whose morphologies are analogous to volcanic landforms on Earth, and the huge volcanoes in the Tharsis region (Olympus Mons and Tharsis Montes) are prime examples resembling many characteristics of Hawaiian shield volcanoes. The main difference between the Martian and terrestrial volcanoes are their size and the length of the flows, possibly due to higher eruption rates, the "stationary" character of the source (no plate tectonics) and the lower gravity. The Tharsis plateau is the topographically most prominent region on Mars, and associated with an areoid high. On Earth, large geoid highs are related to longlived heterogeneities near the core-mantle boundary that are sources for large igneous provinces. The Tharsis' volcanic vent structures were active at least episodically over the past 4 billion years (based on crater count statistics), which indicates long-lived volcanic and magmatic activity. Two major groups of tectonic features are related to the Tharsis bulge: a concentric set of wrinkle ridges indicating compression radial to Tharsis,and several sets of extensional structures that radiate outward from different centers within Tharsis, indicating tension circumferential to Tharsis. No landforms imply ancient plate tectonics. Here, we present surface ages associated with volcanic and tectonic landforms with a special focus on the ancient magma-tectonic environment (see Grott et al. 2006, this volume). We will examine the long-lived volcanism and tectonic surface expressions and discuss whether Mars volcanism could represent deep mantle plumes.

  18. Exploring Active Tectonics in the Dominican Republic

    NASA Astrophysics Data System (ADS)

    Carbó-Gorosabel, A.; Córdoba-Barba, D.; Martín-Dívila, J.; Granja-Bruña, J. L.; Llanes Estrada, P.; Muñoz-Martín, A.; ten Brink, U. S.

    2010-07-01

    The devastating 12 January 2010 Haiti earthquake (M = 7.0), which killed an estimated 230,000 people and caused extensive damage to homes and buildings, drew attention to the crucial need for improved knowledge of the active tectonics of the Caribbean region. But even before this disastrous event, interest in understanding the active and complex northeastern Caribbean plate boundary had been increasing, because this region has experienced significant seismic activity during the past century and has an extensively documented record of historical seismicity and tsunamis. Moreover, this is an easily accessible region in which to study the continuity of seismic faults offshore and to try to understand the transitions between strike-slip and convergent tectonic regimes. Interest in the region has led to several studies that have improved scientists' knowledge of subduction zone tectonics and earthquake and tsunami hazard assessments 005BMann et al., 2002; ten Brink et al., 2006, 2009; Grindlay et al., 2005; Manaker et al., 2008; Granja Bruña et al., 2009; Mondziel et al., 2010].

  19. Geomorphic Indices in the Assessment of Tectonic Activity in Forearc of the Active Mexican Subduction Zone

    NASA Astrophysics Data System (ADS)

    Gaidzik, K.; Ramirez-Herrera, M. T.

    2015-12-01

    Rapid development of GIS techniques and constant advancement of digital elevation models significantly improved the accuracy of extraction of information on active tectonics from landscape features. Numerous attempts were made to quantitatively evaluate recent tectonic activity using GIS and DEMs, and a set of geomorphic indices (GI), however these studies focused mainly on sub-basins or small-scale areal units. In forearc regions where crustal deformation is usually large-scale and do not concentrate only along one specific fault, an assessment of the complete basin is more accurate. We present here the first attempt to implement thirteen GI in the assessment of active tectonics of a forearc region of an active convergent margin using the entire river basins. The GIs were divided into groups: BTAI - basin geomorphic indices (reflecting areal erosion vs. tectonics) and STAI - stream geomorphic indices (reflecting vertical erosion vs. tectonics). We calculated selected indices for 9 large (> 450 km2) drainage basins. Then we categorized the obtained results of each index into three classes of relative tectonic activity: 1 - high, 2 - moderate, and 3 - low. Finally we averaged these classes for each basin to determine the tectonic activity level (TAI). The analysis for the case study area, the Guerrero sector at the Mexican subduction zone, revealed high tectonic activity in this area, particularly in its central and, to a lesser degree, eastern part. This pattern agrees with and is supported by interpretation of satellite images and DEM, and field observations. The results proved that the proposed approach indeed allows identification and recognition of areas witnessing recent tectonic deformation. Moreover, our results indicated that, even though no large earthquake has been recorded in this sector for more than 100 years, the area is highly active and may represent a seismic hazard for the region.

  20. The Cenozoic volcanism in the Kivu rift: Assessment of the tectonic setting, geochemistry, and geochronology of the volcanic activity in the South-Kivu and Virunga regions

    NASA Astrophysics Data System (ADS)

    Pouclet, A.; Bellon, H.; Bram, K.

    2016-09-01

    The Kivu rift is part of the western branch of the East African Rift system. From Lake Tanganyika to Lake Albert, the Kivu rift is set in a succession of Precambrian zones of weakness trending NW-SE, NNE-SSW and NE-SW. At the NW to NNE turn of the rift direction in the Lake Kivu area, the inherited faults are crosscut by newly born N-S fractures which developed during the late Cenozoic rifting and controlled the volcanic activity. From Lake Kivu to Lake Edward, the N-S faults show a right-lateral en echelon pattern. Development of tension gashes in the Virunga area indicates a clockwise rotation of the constraint linked to dextral oblique motion of crustal blocks. The extensional direction was W-E in the Mio-Pliocene and ENE-WSW in the Pleistocene to present time. The volcanic rocks are assigned to three groups: (1) tholeiites and sodic alkali basalts in the South-Kivu, (2) sodic basalts and nephelinites in the northern Lake Kivu and western Virunga, and (3) potassic basanites and potassic nephelinites in the Virunga area. South-Kivu magmas were generated by melting of spinel + garnet lherzolite from two sources: an enriched lithospheric source and a less enriched mixed lithospheric and asthenospheric source. The latter source was implied in the genesis of the tholeiitic lavas at the beginning of the South-Kivu tectono-volcanic activity, in relationships with asthenosphere upwelling. The ensuing outpouring of alkaline basaltic lavas from the lithospheric source attests for the abortion of the asthenospheric contribution and a change of the rifting process. The sodic nephelinites of the northern Lake Kivu originated from low partial melting of garnet peridotite of the sub-continental mantle due to pressure release during swell initiation. The Virunga potassic magmas resulted from the melting of garnet peridotite with an increasing degree of melting from nephelinite to basanite. They originated from a lithospheric source enriched in both K and Rb, suggesting the

  1. Marine-to-lacustrine transition, mud volcanism, and slope instability in an active tectonic setting: the MIS 5 to 4 transition in the Sea of Marmara, Turkey

    NASA Astrophysics Data System (ADS)

    Grall, Céline; Henry, Pierre; Kendé, Julia; Namık Çaǧatay, M.; Kadir Eriş, K.; Paillès, Christine; Sorlien, Christopher; Shillington, Donna; McHugh, Cecilia; Steckler, Michael; Çifçi, Günay; Géli, Louis

    2016-04-01

    In the Sea of Marmara, glacio-eustatic cycles set the tempo of a complex history of disconnection and reconnection with the Black Sea and with the global ocean through the Mediterranean Sea. As a result, the sedimentary record consists of alternating high stand marine sediments and lowstand sea or lake sediments. The Sea of Marmara is also an active transtensional basin along the Northern branch of the North Anatolian Fault (NNAF), which accommodates most (~3/4) of the 21-27 mm/a dextral slip between Eurasia and Anatolia. This peculiar setting makes the Sea of Marmara an exceptional site to study the interplay of paleo-environmental factors and seismotectonic processes. Notably, Mass Transport Deposits (MTDs) crossing the faults provide offset markers although their age remains uncertain. A high resolution seismic stratigraphic model has been proposed for 100 ka glacial cycles, based on onlap sequences within basins, and paleo-deltas at shorelines. The sedimentation rate in basins decreases during episodes of sea-level rise and reach maximum values during low stands. Remarkably, seismic reflector sequences display nearly identical character for locations with similar sedimentation rate. The uppermost sequence boundary reflector (Red-H1) has been recently cored at several locations during MARSITECRUISE (Ifremer R/V Pourquoi Pas?, Oct-Nov. 2014), enabled us to correlate high resolution seismic data with core data. The Red-H1 reflector is regionally characterized by a high amplitude and a reverse polarity. Correlations between seismic data and piston core logs indicate that the reverse polarity of this reflector may be explained by a negative density contrast between lacustrine sediments above and a greenish sapropellic layer of several meters thickness below. On shelves, Red-H1 is on top of the low stand wedge. On slopes and topographic highs, Red-H1 appears as an erosional surface laterally correlative with an onlapping unit in basins and is frequently overlain by

  2. Tectonic setting of the Kolar Schist Belt, Karnataka, India

    NASA Technical Reports Server (NTRS)

    Hanson, G. N.; Krogstad, E. J.; Rajamani, V.

    1988-01-01

    The tectonic setting of the Kolar Schist Belt and why the belt may represent a late Archean suture was discussed. The isotopic and chronological evidence that suggest diverse origins of the various packages of supracrustal rocks within the schist belt and the two gneiss terrains adjoining the belt were summarized. The eastern and western amphibolites were derived from sources at similar depths in the mantle (probably at similar ages, ca. 2.7 Ga), but these sources had distinct trace element compositions and histories. A distinctive feature of these differences was shown by the differences between the east and west amphibolites on a Ce vs. Nd diagram. In the gneisses the age and isotopic evidence suggest that the two terranes had distinct histories until after 2520 Ma and by 2420 Ma (Ar-40/Ar-39 age of muscovite in the sheared margin of the schist belt). Based on these data, the schist belt probably represents the site of accretion of diverse fragments (terrains) to the margin of the craton in the latest Archean, possibly as an Archean analog to the Phanerozoic North American Cordillera.

  3. Mobilization of evaporites in tectonically active terrains

    NASA Astrophysics Data System (ADS)

    Stiros, Stathis C.

    2015-04-01

    The role of evaporites, mostly halite, during seismic sequences is investigated using evidence from certain earthquakes with magnitude between approximately 6.0 and 7.2 which occurred in the last 60 years in the Zagros Mts. (Iran) and the Ionian Sea (Greece); i.e. two seismically active areas, characterized by evaporite-associated decollements and more shallow decollements combined with mature, along-thrusts intrusions. Studied earthquakes produced either large scale surface deformation, or were covered by high-resolution and accuracy GPS and INSAR data, permitting to fully recognize the deformation pattern. In all cases an "atypical", tectonic deformation pattern was observed, ranging from apparently "impossible" patterns (thrust and normal faults, sub-parallel and homothetic; 1953 Cephalonia earthquake, Greece) to rather diffuse tectonic patterns, even to "phantom" earthquakes (Zagros). Careful analysis and modeling of the surface deformation data, in combination with the available geological, geophysical and seismological data permits to recognize, and even to quantify differences between deformation observed, and that expected in ordinary environments. In particular, it was found that during earthquakes evaporites were mobilized, and this led either to a secondary deformation of the overburden, fully detached from the basement, or to significant aseismic (post-seismic) deformation. Anomalies in the distribution of seismic intensities due to evaporitic intrusions along faults were also observed. Apart from seismological implications (unpredictable post-seismic deformation, possibly also in the far-field), these results deriving from regions at different levels of evaporitic evolution, may prove useful to understand patterns of mobilization of evaporites during periods of tectonic activity.

  4. Transdomes: Emplacement of Migmatite Domes in Oblique Tectonic Settings

    NASA Astrophysics Data System (ADS)

    Teyssier, C. P.; Rey, P. F.; Whitney, D. L.; Mondy, L. S.; Roger, F.

    2014-12-01

    Many migmatite domes are emplaced within wrench corridors in which a combination of strike-slip and extensional detachment zones (pull-apart, extensional relay, or transfer zones) focus deep-crust exhumation. The Montagne Noire dome (France, Variscan Massif Central) exemplifies wrench-related dome formation and displays the following structural, metamorphic, and geochronologic characteristics of a 'transdome': the dome is elongate in the direction of extension; foliation outlines a double dome separated by a high-strain zone; lineation is shallowly plunging with a fairly uniform trend that parallels the strike of the high-strain zone; subdomes contain recumbent structures overprinted by upright folds that affected upward by flat shear zones associated with detachment tectonics; domes display a large syn-deformation metamorphic gradient from core (upper amphibolite facies migmatite) to margin (down to greenschist facies mylonite); some rocks in the dome core experienced isothermal decompression revealed by disequilibrium reaction textures, particularly in mafic rocks (including eclogite); and results of U-Pb geochrononology indicate a narrow range of metamorphic crystallization from core to mantling schist spanning ~10 Myr. 3D numerical modeling of transdomes show that the dome solicits a larger source region of partially molten lower crust compared to 2D models; this flowing crust creates a double-dome architecture as in 2D models but there are differences in the predicted thermal history and flow paths. In a transtension setting, flow lines converge at depth (radial-centripetal flow) toward the zone of extension and diverge at shallow levels in a more uniform direction that is imposed by upper crust motion and deformation. This evolution produces a characteristic pattern of strain history, progressive fabric overprint, and P-T paths that are comparable to observed dome rocks.

  5. Tectonic setting of the Mendocino triple junction region

    SciTech Connect

    Clarke, S.H. Jr.; McLaughlin, R.J. ); Carver, G.A.; Burke, R.M.; McPherson, R.C. )

    1993-04-01

    Onshore and offshore geologic mapping coupled with topical investigations constrain the tectonic relations and geometry of active plate boundaries in the Mendocino triple junction region. Along the northern California coast and offshore, Gorda-North American plate convergence is reflected by youthful west- to northwest-verging thrust fault systems that extend to or near the plate interface at depth. Interplate coupling across a minimum breadth of 70--80 km is indicated by late Quaternary uplift and shortening rates, the nature and distribution of upper and lower plate seismicity, divergent trends in upper plate structures, and a history of large late Holocene earthquakes. Offshore seismic-reflection and seismicity data from the vicinity of the Mendocino fault (MF) show that the fault dips steeply to the north, and that the older, relatively rigid Pacific plate acts as a buttress against which the southern Gorda plate is being deformed. Onshore investigations show that the San Andreas fault zone (SAF) extends on land southeast of Point Delgada (at Whale Gulch), and is manifested along the north and northeast side of the King Range (KR) by north-northeast-vergent thrust faults. This thrust fault system may root into the steeply dipping offshore San Andreas fault. Faults of this system may include active, blind northeast-vergent thrusts that extend from a root zone beneath the King Range northward and upward into Franciscan Complex (Coastal belt) rocks along the north flank of the range. The southern Cascadia subduction zone megathrust intersects the Mendocino and San Andreas transform faults in the Mendocino triple junction. The upper crustal location of this intersection lies nearshore and/or landward along the north flank of the King Range. An area of focused rapid uplift and repeated coseismic growth (Mendocino Uplift) straddles the triple junction.

  6. Trace element characteristics of graywackes and tectonic setting discrimination of sedimentary basins

    NASA Astrophysics Data System (ADS)

    Bhatia, Mukul R.; Crook, Keith A. W.

    1986-02-01

    The graywackes of Paleozoic turbidite sequences of eastern Australia show a large variation in their trace element characteristics, which reflect distinct provenance types and tectonic settings for various suites. The tectonic settings recognised are oceanic island arc, continental island arc, active continental margin, and passive margins. Immobile trace elements, e.g. La, Ce, Nd, Th, Zr, Nb, Y, Sc and Co are very useful in tectonic setting discrimination. In general, there is a systematic increase in light rare earth elements (La, Ce, Nd), Th, Nb and the Ba/Sr, Rb/Sr, La/Y and Ni/Co ratios and a decrease in V, Sc and the Ba/Rb, K/Th and K/U ratios in graywackes from oceanic island arc to continental island arc to active continental margin to passive margin settings. On the basis of graywacke geochemistry, the optimum discrimination of the tectonic settings of sedimentary basins is achieved by La-Th, La-Th-Sc, Ti/Zr-La/Sc, La/Y-Sc/Cr, Th-Sc-Zr/10 and Th-Co-Zr/10 plots. The analysed oceanic island arc graywackes are characterised by extremely low abundances of La, Th, U, Zr, Nb; low Th/U and high La/Sc, La/Th, Ti/Zr, Zr/Th ratios. The studied graywackes of the continental island arc type setting are characterised by increased abundances of La, Th, U, Zr and Nb, and can be identified by the La-Th-Sc and La/Sc versus Ti/Zr plots. Active continental margin and passive margin graywackes are discriminated by the Th-Sc-Zr/10 and Th-Co-Zr/10 plots and associated parameters (e.g. Th/Zr, Th/Sc). The most important characteristic of the analysed passive margin type graywackes is the increased abundance of Zr, high Zr/Th and lower Ba, Rb, Sr and Ti/Zr ratio compared to the active continental margin graywackes.

  7. Convective Structure and Tectonic Setting for Synchronously Rotating Super-Earth Exoplanets

    NASA Astrophysics Data System (ADS)

    van Summeren, J.; Conrad, C. P.; Gaidos, E.

    2010-12-01

    We investigated mantle convective structures and tectonic settings for synchronously rotating exoplanets on close-in orbits around their parent stars. Our study is motivated by the possibility that extreme variations in surface temperature affect these planets' interior dynamics and related surface expressions. Exoplanets on orbits ≤0.1 astronomical units are expected to be tidally-locked to their parent star and this can induce strong (>1000K) temperature differences between the planet's permanent day and night sides, in the absence of a significant atmosphere. To examine the influence of such extreme conditions on planetary mantle convection and tectonics, we performed a series of numerical simulations of an incompressible fluid at infinite Prandtl number with imposed asymmetric surface temperature conditions. Plate-like behavior is approximated in our models by applying a temperature-dependent viscous/pseudo-plastic rheology. To investigate a diversity of possible exoplanets, we studied a range of surface temperature contrasts, Rayleigh numbers, and internal heating rates. Our preliminary modeling results show that an imposed asymmetric surface temperature distribution promotes mantle-wide asymmetries in convective overturn. On the permanent night-side, a large-scale downwelling develops below an immobile thick crust. Towards the permanent day-side, the crust thins and this allows for greater lithospheric mobility. Such planet-wide variations in tectonic settings could be expressed in the planet's geology, habitability, volcanic activity, atmospheric outgassing, and climate, some of which have the potential to be astronomically discoverable in the future.

  8. 3D fold growth rates in transpressional tectonic settings

    NASA Astrophysics Data System (ADS)

    Frehner, Marcel

    2015-04-01

    Geological folds are inherently three-dimensional (3D) structures; hence, they also grow in 3D. In this study, fold growth in all three dimensions is quantified numerically using a finite-element algorithm for simulating deformation of Newtonian media in 3D. The presented study is an extension and generalization of the work presented in Frehner (2014), which only considered unidirectional layer-parallel compression. In contrast, the full range from strike slip settings (i.e., simple shear) to unidirectional layer-parallel compression is considered here by varying the convergence angle of the boundary conditions; hence the results are applicable to general transpressional tectonic settings. Only upright symmetrical single-layer fold structures are considered. The horizontal higher-viscous layer exhibits an initial point-like perturbation. Due to the mixed pure- and simple shear boundary conditions a mechanical buckling instability grows from this perturbation in all three dimensions, described by: Fold amplification (vertical growth): Fold amplification describes the growth from a fold shape with low limb-dip angle to a shape with higher limb-dip angle. Fold elongation (growth parallel to fold axis): Fold elongation describes the growth from a dome-shaped (3D) structure to a more cylindrical fold (2D). Sequential fold growth (growth perpendicular to fold axial plane): Sequential fold growth describes the growth of secondary (and further) folds adjacent to the initial isolated fold. The term 'lateral fold growth' is used as an umbrella term for both fold elongation and sequential fold growth. In addition, the orientation of the fold axis is tracked as a function of the convergence angle. Even though the absolute values of all three growth rates are markedly reduced with increasing simple-shear component at the boundaries, the general pattern of the quantified fold growth under the studied general-shear boundary conditions is surprisingly similar to the end

  9. Active Tectonics in crossroads of an evolving orogen and morphological consequences: Anatolia

    NASA Astrophysics Data System (ADS)

    Koral, Hayrettin

    2016-04-01

    Anatolia lies in a curved setting of the active Alpine Mountain Range and is located in crossroads of the European and Asian terrains. It is one of the fastest deforming land in the world, manifested by seismicity, characteristic landforms and GPS measurements. Active tectonics in Anatolia provides not only a comparable geological model for the past orogens, but also a laboratory case for morphological consequences of an orogenic processes. Anatolia comprise different tectonic subsettings with its own characteristics. Northern part is influenced by tectonic characteristics of the Black Sea Basin, the Pontides and the Caucasian Range; northwestern part by the Balkanides; eastern-southeastern part by the Bitlis-Zagros suture; and south-southwestern part by the eastern Mediterranean subduction setting. Much of its present tectonic complexity was inherited from the convergence dominant plate tectonic setting of the platelets prior to the Middle-Neogene. Beginning about 11 Ma ago, the deformed and uplifted landmass unable to accommodate further deformation in Anatolia and ongoing tectonic activity gave rise to rearrangement of tectonic forces and westerly translational movements. Formation of major strike-slip faults in Anatolia including the North and East Anatolian Faults and a new platelet called the Anatolian Plate are the consequences of this episode. Such change in the tectonic regime has led to modification of previously-formed landscape, modification and sometimes termination of previously-formed basins. Evidence is present in the Plio-Quaternary stratigraphy, tectonic characteristics and morphology of the well-studied areas. This presentation will discuss active tectonic features of the northwestern, southwestern and eastern Anatolian subsettings and their influence on morphology that is closely related to sites of pre-historical human settlement.

  10. Geochemistry of the Ediacaran-Early Cambrian transition in Central Iberia: Tectonic setting and isotopic sources

    NASA Astrophysics Data System (ADS)

    Fuenlabrada, José Manuel; Pieren, Agustín P.; Díez Fernández, Rubén; Sánchez Martínez, Sonia; Arenas, Ricardo

    2016-06-01

    A complete Ediacaran-Early Cambrian stratigraphic transition can be observed in the southern part of the Central Iberian Zone (Iberian Massif). Two different stratigraphic units, underlying Ordovician series, display geochemical and Sm-Nd isotopic features in agreement with an evolving geodynamic setting. Pusa Shales (Early Cambrian) rest unconformably on greywackes of the Lower Alcudian Formation (Late Ediacaran). Both sequences present minor compositional variations for major and trace element contents and similar REE patterns, close to those of PAAS (Post Archean Australian Shale). Trace element contents and element ratios suggest mixed sources, with intermediate to felsic igneous contributions for both units. Tectonic setting discrimination diagrams for the Ediacaran greywackes indicate that these turbiditic series were deposited in a sedimentary basin associated with a mature active margin (volcanic arc). However, the compositions of the Cambrian shales fit better with a more stable context, a back-arc or retro-arc setting. εNd(T) and TDM ages are compatible with dominance of a similar cratonic source for both sequences, probably the West Africa Craton. εNd565 values for the Ediacaran greywackes (- 3.0 to - 1.4) along with TDM ages (1256-1334 Ma) imply a significant contribution of juvenile material, probably derived from the erosion of the volcanic arc. However, εNd530 values in the Cambrian shales (- 5.2 to - 4.0) together with older TDM ages (1444-1657 Ma), suggest a higher contribution of cratonic isotopic sources, probably derived from erosion of the adjacent mainland. Coeval with the progressive cessation of arc volcanism along the peri-Gondwanan realm during the Cambrian, there was a period of more tectonic stability and increasing arrival of sediments from cratonic areas. The geochemistry of the Ediacaran-Cambrian transition in Central Iberia documents a tectonic switch in the periphery of Gondwana, from an active margin to a more stable context

  11. Active tectonics in the Moroccan High Atlas

    NASA Astrophysics Data System (ADS)

    Sébrier, Michel; Siame, Lionel; Zouine, El Mostafa; Winter, Thierry; Missenard, Yves; Leturmy, Pascale

    2006-01-01

    Review of seismological and structural data coupled with new data on topographical, geomorphology, and Quaternary geology allows delineating the major active faults of the High Atlas. These are the North and South border faults of which fault segmentations correspond to Mw ranging between 6.1 and 6.4. Detail active tectonics analyses were performed on the South Atlas Fault Zone in the Souss and Ouarzazate basins, where deformed Quaternary levels permit to estimate slip rates on individual faults in the order of 0.1 mm yr -1. Such low slip rates imply that large observational time-window is needed to analyze active deformation in low-seismicity regions. However, the complex 3D geometry of reverse or thrust faults may cause difficulty to relate surface observations with the deeper faults that have the potential to nucleate big earthquakes. Further studies are necessary to interpret the Anti Atlas seismicity. To cite this article: M. Sebrier et al., C. R. Geoscience 338 (2006).

  12. Experimental modelling of tectonics-erosion-sedimentation interactions in compressional, extensional, and strike-slip settings

    NASA Astrophysics Data System (ADS)

    Graveleau, Fabien; Strak, Vincent; Dominguez, Stéphane; Malavieille, Jacques; Chatton, Marina; Manighetti, Isabelle; Petit, Carole

    2015-09-01

    Tectonically controlled landforms develop morphologic features that provide useful markers to investigate crustal deformation and relief growth dynamics. In this paper, we present results of morphotectonic experiments obtained with an innovative approach combining tectonic and surface processes (erosion, transport, and sedimentation), coupled with accurate model monitoring techniques. This approach allows for a qualitative and quantitative analysis of landscape evolution in response to active deformation in the three end-member geological settings: compression, extension, and strike-slip. Experimental results outline first that experimental morphologies evolve significantly at a short time scale. Numerous morphologic markers form continuously, but their lifetime is generally short because erosion and sedimentation processes tend to destroy or bury them. For the compressional setting, the formation of terraces above an active thrust appears mainly controlled by narrowing and incision of the main channel through the uplifting hanging-wall and by avulsion of deposits on fan-like bodies. Terrace formation is irregular even under steady tectonic rates and erosional conditions. Terrace deformation analysis allows retrieving the growth history of the structure and the fault slip rate evolution. For the extensional setting, the dynamics of hanging-wall sedimentary filling appears to control the position of the base level, which in turn controls footwall erosion. Two phases of relief evolution can be evidenced: the first is a phase of relief growth, and the second is a phase of upstream propagation of topographic equilibrium that is reached first in the sedimentary basin. During the phase of relief growth, the formation of triangular facets occurs by degradation of the fault scarp, and their geometry (height) becomes stationary during the phase of upstream propagation of the topographic equilibrium. For the strike-slip setting, the complex morphology of the wrench zone

  13. Introduction to Special Section on the Geological, Geophysical, and Tectonic Setting of the Cascade Range

    NASA Astrophysics Data System (ADS)

    Muffler, L. J. Patrick

    1990-11-01

    The Cascade Range is an active volcanic arc that is formed by the subduction of the Juan de Fuca plate system beneath North America [Riddihough, 1978]. Knowledge of the Cascade Range, its volcanic rocks, and its tectonic setting is not only of broad scientific interest but also bears directly upon the estimation of geothermal resources and the evaluation of volcanic and seismic hazards. An understanding of the regional aspects of the Cascade Range is at the present time particularly important to the assessment of geothermal resources. Although identified geothermal resources in the Cascade Range are modest [Brook et al., 1979], substantial undiscovered geothermal resources have been inferred [e.g., Brook et al., 1979; Black et al., 1983; Bloomquist et al., 1985], primarily from the favorable volcanic and tectonic setting but also from high regional heat flow along the Cascade Range [Blackwell et al., 1982]. Consequently, a multiyear, multidisciplinary program of studies to refine the geothermal resource estimates of the Cascade Range is a major objective of the U.S. Geological Survey (USGS) Geothermal Research Program [Muffler, 1987]. The smallest and easiest part of this effort is an updated inventory of known hydrothermal convection systems. A much larger and far more difficult task is the estimation of the undiscovered geothermal resources. Existing drill hole information in the Cascade Range is sparse, and under the foreseeable economic climate, direct evaluation of the thermal regime by numerous deep holes is unlikely. However, the magnitude of the undiscovered geothermal resources can be addressed indirectly by an analysis of the tectonic, geophysical, volcanic, and hydrologie setting of the Cascade Range, thus allowing extrapolation of available drill hole data.

  14. Tectonic Setting of the Wooded Island Earthquake Swarm, Eastern Washington

    SciTech Connect

    Blakely, R. J.; Sherrod, B. L.; Weaver, C. S.; Rohay, A. C.; Wells, R. E.

    2012-08-01

    Magnetic anomalies provide insights into the tectonic implications of a swarm of ~1500 shallow (~1 km deep) earthquakes that occurred in 2009 on the Hanford site, Washington. Epicenters were concentrated in a 2 km2 area near Wooded Island in the Columbia River. The largest earthquake (M 3.0) had first motions consistent with slip on a northwest-striking reverse fault. The swarm was accompanied by 35 mm of vertical surface deformation, seen in satellite interferometry (InSAR), interpreted to be caused by ~50 mm of slip on a northwest-striking reverse fault and associated bedding-plane fault in the underlying Columbia River Basalt Group (CRBG). A magnetic anomaly over exposed CRBG at Yakima Ridge 40 km northwest of Wooded Island extends southeastward beyond the ridge to the Columbia River, suggesting that the Yakima Ridge anticline and its associated thrust fault extend southeastward in the subsurface. In map view, the concealed anticline passes through the earthquake swarm and lies parallel to reverse faults determined from first motions and InSAR data. A forward model of the magnetic anomaly near Wooded Island is consistent with uplift of concealed CRBG, with the top surface <200 m below the surface. The earthquake swarm and the thrust and bedding-plane faults modeled from interferometry all fall within the northeastern limb of the faulted anticline. Finally, although fluids may be responsible for triggering the Wooded Island earthquake swarm, the seismic and aseismic deformation are consistent with regional-scale tectonic compression across the concealed Yakima Ridge anticline.

  15. Tectonics

    NASA Astrophysics Data System (ADS)

    John Dewey will complete his term as editor-in-chief of Tectonics at the end of 1984. Clark Burchfiel's term as North American Editor will also end. Tectonics is published jointly with the European Geophysical Society. This newest of AGU's journals has already established itself as an important journal bridging the concerns of geophysics and geology.James A. Van Allen, president of AGU, has appointed a committee to recommend candidates for both editor-in-chief and North American editor for the 1985-1987 term.

  16. Tectonic setting of the 1. 73 Ga Payson ophiolite

    SciTech Connect

    Dann, J.C.

    1993-04-01

    The Early Proterozoic orogenic belt of central Arizona is divided by north- to northeast-trending shear zones into a collage of crustal blocks assembled during three periods of convergent tectonism. Whether any of the crustal blocks are allochthonous with respect to one another is an outstanding question. The sheeted dike complex of the Payson ophiolite forms a pseudostratigraphic layer that connects underlying gabbro to an overlying sequence of submarine volcanic rocks. The ophiolite intruded and erupted upon an older basement complex that includes 1.75 Ga granitoids, the oldest rocks known in central Arizona. The 1.73 Ga ophiolite is overlain by dacitic and andesitic volcanic and volcaniclastic rocks and a sequence of turbidites with 1.72 Ga ash beds and is intruded by 1.71 Ga granodiorite. In addition to a distinct arc geochemical signature, the fact that the Payson ophiolite intrudes older arc crust, is intruded by arc plutons, and is overlain by arc-derived rocks in consistent with in situ development within an arc. The northwest boundary of the Mazatzal block, the Moore Gulch fault, separates the Mazatzal block from the 1.74--1.735 Ga arc volcanic and plutonic rocks of the Ash Creek block. If the northeast-trending 1.70 Ga deformational structures are parallel to the paleo-convergent plate boundary, then the northwest-trending dikes of the ophiolite suggest arc-parallel extension. This geometry is more consistent with an intra-arc basin formed as a pull-apart structure along an arc-parallel, strike-slip fault than with a back-arc basin.

  17. Tectonic setting and origin of the Black Warrior basin

    SciTech Connect

    Thomas, W.A.; Whiting, B.M. . Dept. of Geological Sciences)

    1994-03-01

    The Black Warrior basin has a triangular outline that is framed by the Ouachita thrust belt on the southwest, the Appalachian thrust belt on the southeast, and the North American craton on the north. The stratigraphy of the Black Warrior basin includes two distinct parts: a Cambrian-Mississippian passive-margin carbonate-shelf succession, and a Mississippian-Pennsylvanian clastic succession, the lower (Mississippian) part of which grades northeastward into a carbonate-shelf facies. The provenance and dispersal system of the Mississippian-Pennsylvanian clastic deposits have been interpreted in four different ways, each of which has significantly different implications for origin of the basin: (1) Ouachita orogenic source and northeastward prograding; (2) Alabama Appalachian orogenic source and northwestward prograding; (3) Georgia-tennessee Appalachian orogenic source and westward prograding; and (4) cratonic source and southward prograding. Subsidence history determined from calculations of decompacted thickness indicates that (1) the Black Warrior basin is an orogenic foreland basin related primarily to the Ouachita thrust load on the southwest; (2) later emplacement of the Alabama Appalachian thrust belt modified the southeastern side of the Ouachita-related Black Warrior foreland basin; and (3) a separate foreland basin, representing the southern end of the Appalachian foreland basin, formed in response to the Georgia-Tennessee Appalachian thrust load. The previously used criteria do not necessarily support a unique interpretation, but synthesizing these data with subsidence history leads to the conclusion that the Black Warrior basin is a tectonically driven, orogenic foreland basin dominated by Ouachita thrusting and modified by Appalachian thrusting.

  18. Global tectonic activity map with orbital photographic supplement

    SciTech Connect

    Lowman, P.D. Jr.

    1981-01-01

    A three part map showing equatorial and polar regions was compiled showing tectonic and volcanic activity of the past one million years, including the present. Features shown include actively spreading ridges, spreading rates, major active faults, subduction zones, well defined plates, and volcanic areas active within the past one million years. Activity within this period was inferred from seismicity (instrumental and historic), physiography, and published literature. The tectonic activity map was used for planning global geodetic programs of satellite laser ranging and very long base line interferometry and for geologic education.

  19. A global tectonic activity map with orbital photographic supplement

    NASA Technical Reports Server (NTRS)

    Lowman, P. D., Jr.

    1981-01-01

    A three part map showing equatorial and polar regions was compiled showing tectonic and volcanic activity of the past one million years, including the present. Features shown include actively spreading ridges, spreading rates, major active faults, subduction zones, well defined plates, and volcanic areas active within the past one million years. Activity within this period was inferred from seismicity (instrumental and historic), physiography, and published literature. The tectonic activity map was used for planning global geodetic programs of satellite laser ranging and very long base line interferometry and for geologic education.

  20. The Karoo igneous province — A problem area for inferring tectonic setting from basalt geochemistry

    NASA Astrophysics Data System (ADS)

    Duncan, Andrew R.

    1987-06-01

    Tholeiitic basalts and associated intrusives are the major component of the Karoo igneous province. They are of Mesozoic age and constitute one of the world's classic continental flood basalt (CFB) provinces. It has been argued that most Karoo basalts have not undergone significant contamination with continental crust and that their lithospheric mantle source areas were enriched in incompatible minor and trace elements during the Proterozoic. The only exceptions to this are late-stage MORB-like dolerites near the present-day continental margins which are considered to be of asthenospheric origin. When data for the "southern" Karoo basalts are plotted on many of the geochemical discriminant diagrams which have been used to infer tectonic setting, essentially all of them would be classified as calc-alkali basalts (CAB's) or low-K tholeiites. Virtually none of them plot in the compositional fields designated as characteristic of "within-plate" basalts. There is little likelihood that the compositions of the Karoo basalts can be controlled by active subduction at the time of their eruption and no convincing evidence that a "subduction component" has been added to the subcontinental lithospheric mantle under the entire area in which the basalts crop out. It must be concluded that the mantle source areas for CAB's and the southern Karoo basalts have marked similarities. In contrast, the data for "northern" Karoo basalts largely plot in the "within-plate" field on geochemical discriminant diagrams. Available data suggest that the source composition and/or the restite mineralogy and degree of partial melting are different for southern and northern Karoo basalts. There is no evidence for any difference in tectonic setting between the southern and northern Karoo basalts at the time they were erupted. This appears to be clear evidence that specific mantle source characteristics and/or magmatic processes can vary within a single CFB province to an extent that renders at least

  1. Tectonic Activity during the Harappan Civilization

    NASA Astrophysics Data System (ADS)

    Prasad, M.; Nur, A.

    2001-12-01

    The Harappan civilization in South Asia existed between 3,300 and 1,900 BC. Extensive remnants from this era are found in Pakistan and northwestern India. The region is far from plate boundaries and, until recently, has been considered tectonically inactive. A combination of data from current and historic seismicity, marine seismic surveys, and prevalent geologic and tectonic features with archeological findings, historical and scriptural records, and GIS mapping of large scale areas shows: \\begin{enumerate} Occurrence of earthquakes starting from the 26th January, 2001 event to as far back as 2500 BC Existence of an ancient river, Saraswati corroborated with historical records, GIS mapping, marine seismic surveys Sea level changes from archeological excavations of variations in fauna. We show how a cross-disciplinary study can provide ways of filling information gaps and providing new insights. A comparison between isoseismal lines from the Magnitude 8 event of 26th January, 2001 with location of Harappan cities shows that most cities would have been obliterated by such an event. >http://pangea.stanford.edu/ ~manika/harappa.html

  2. Digital images of combined oceanic and continental data sets and their use in tectonic studies

    NASA Technical Reports Server (NTRS)

    Haxby, W. F.; Labrecque, J. L.; Weissel, J. K.; Karner, G. D.

    1983-01-01

    It is shown how crustal and lithospheric studies can benefit when continental and oceanic data sets are combined. It is also shown how digital imaging techniques provide an effective means for displaying the information contained in these combined data sets. The region of Australia, New Zealand, and the surrounding ocean is chosen for illustrating the advantages of combining continental and oceanic data sets. Here, the tectonic setting of Australia, a relatively stable continent in an intraplate environment, can be contrasted with New Zealand, which is traversed by one of the world's major plate boundaries. Simultaneous display and analysis of complementary data sets make possible a rapid geologic and tectonic interpretation of regional areas. It is shown, by way of example, that the relationship between topography and gravity anomalies in central Australia gives important new information concerning the state of isostasy of thrust terrains and their related sedimentary basins and hence provides a means of understanding the mechanical properties of the continental lithosphere.

  3. Tectonic and paleogeographic settings of northeast Asian hydrocarbon systems

    SciTech Connect

    Lindemann, W.L.; Stanley, K.O. )

    1990-05-01

    Most of China and Soviet Asia were formed by the welding of microcontinents and accretionary wedge assemblages from the Devonian through the Late Cretaceous. The first hydrocarbon systems developed in late Precambrian to middle Paleozoic basins on continental platform blocks prior to the Hercynian welding of plates. Later hydrocarbon systems developed in both extensional and compressional successor basins associated with plate collisions from the late Paleozoic to the Cenozoic. Basins with cratonic tectono-stratigraphic assemblages, which formed on Archean-early Paleozoic microcontinent plates, feature hydrocarbon systems that are sourced by marine rocks and reservoired in weathered crusts and/or clastic/carbonate platform rocks. The upper Precambrian and Paleozoic of east Siberia, the middle Paleozoic of west Siberia, and the lower Paleozoic of the Tarim basin are examples of this hydrocarbon system. The rift-sag successor basins, which developed on these welded microplates and accretionary wedges after collision, feature hydrocarbon systems produced from mostly nonmarine rocks in China and mostly marine rocks in Russia. Example successor basins include the marine Jurassic-Cretaceous West Siberian interior sag basin formed over several microplates; the nonmarine Cretaceous-Tertiary rift-sag Songliao and north China basins; and the Neogene extensional strike-slip North Sakhalin basin. The compressional basins formed as a result of late Paleozoic to Cenozoic plate collisions. These basins feature hydrocarbon systems in marine and/or nonmarine rocks depending on the paleogeographic setting. The best example is the late Paleozoic-Mesozoic nonmarine Junggar basin in northwest China.

  4. Quaternary tectonic setting of South-Central coastal California

    USGS Publications Warehouse

    Lettis, William R.; Hanson, Kathryn L.; Unruh, Jeffrey R.; McLaren, Marcia; Savage, William U.; Keller, Margaret A.

    2004-01-01

    Recent geodetic, geologic, and seismologic studies show that the south-central coast of California is a region of active Quaternary deformation. Northeast-directed crustal shortening is occurring in a triangular-shaped region between the Hosgri-San Simeon fault system on the west, the Southern Coast Ranges on the northeast, and the western Transverse Ranges on the south. We informally call this region the Los Osos domain. In this study, we conducted detailed geological, seismological, and geophysical investigations to characterize the nature and rates of deformation in the domain. Locations of active and potentially active faults and folds are compiled at a scale of 1:250,000 for the entire domain based primarily on onshore geologic data and offshore geophysical data. Crustal shortening in the domain is accommodated by a series of prominent northwest-trending reverse faults and localized folding. The reverse faults separate distinct structural blocks that have little or no internal deformation. Hangingwall blocks are being uplifted at rates of up to 0.2 mm/yr. Footwall blocks are either static or slowly subsiding at rates of 0.1 mm/yr or less, except for localized areas of concentrated subsidence directly adjacent to some faults. The cumulative rate of crustal shortening is about 1 to 2 mm/yr across the northern part of the domain based on observed geologic deformation. Cumulative shortening across the central and southern parts of the domain is poorly constrained by geologic data and may approach 2 to 3 mm/yr. Historical and instrumental seismicity generally are spatially associated with the uplifted blocks and bordering reverse faults to depths of about 10 km. Together with near-surface geological data and deeper crustal geophysical imaging that show high-angle faulting, the seismicity data indicate that the reverse faults probably extend to the base of the seismogenic crust. The base of the seismogenic crust may correspond with a mid-crustal detachment or

  5. Tectonic setting of Talladega belt olistostromal sequences, Alabama appalachians

    SciTech Connect

    Tull, J.F.; Telle, W.R.

    1985-01-01

    Olistostromal sequences are common in parts of the Lay Dam Formation (LDF) in the Alabama Talladega slate belt. The LDF occurs in low-angle unconformable contact above metamorphic equivalents of the Cambrian-Ordovician carbonate bank facies, and is Silurian (.) to early Devonian in age. Units above and below the LDF can be stratigraphically linked to cratonal North America. Olistostromal deposits form an arcuate belt 40-50 km in length and are found within a thick (up to 3 km) sequence of lower greenschist facies metaclastic rocks. Single deposits range up to 500 m in thickness and consist of unsorted, unbedded polymictic diamictites containing clasts (up to 2m) of carbonate, pelite, quartzite, chert, felsic plutonic and high-grade metamorphic rocks; mafic and ultramafic clasts are absent. Olistrostromal units are interbedded with metagraywacke and feldspathic metasandstone, rhythmically layered and graded metasiltstone, and massive metapelite. Lithologies, lithologic associations and unit geometries indicate derivation of olistostromal sequences through gravity flow in a submarine fan/delta complex. Distribution of diamictites and clast sizes and types indicate major nearby Grenville basement-cored uplifts on the SE. with deposition of the LDF fan/delta complex upon a tilted and rapidly foundering shelf block. Shelf uplift, collapse, and LDF deposition were followed rapidly by volcanism and major Acadian dynamothermal activity, and are interpreted to be a response to initial subduction along the shelf margin during the middle Paleozoic.

  6. Tectonic control on the drainage system in a piedmont region in tectonically active eastern Himalayas

    NASA Astrophysics Data System (ADS)

    Goswami, Chandreyee; Mukhopadhyay, Dhruba; Poddar, Bikash Chandra

    2012-03-01

    The impact of neotectonic activity on drainage system has been studied in a large alluvial fan in the eastern Himalayan piedmont area between the Mal River and the Murti River. Two distinct E-Wlineaments passing through this area had been identified by Nakata (1972, 1989) as active faults. The northern lineament manifested as Matiali scarp and the southern one manifested as Chalsa scarp represent the ramp anticlines over two blind faults, probably the Main Boundary Thrust (MBT) and the Himalayan Frontal Thrust (HFT), respectively. The fan surface is folded into two antiforms with a synform in between. These folds are interpreted as fault propagation folds over the two north dipping blind thrusts. Two lineaments trending NNE-SSW and nearly N-S, respectively, are identified, and parts of present day courses of the Murti and Neora Rivers follow them. These lineaments are named as Murti and Neora lineaments and are interpreted to represent a conjugate set of normal faults. The rivers have changed their courses by the influence of these normal faults along the Murti and Neora lineaments and their profiles show knick points where they cross E-W thrusts. The overall drainage pattern is changed from radial pattern in north of the Matiali scarp to a subparallel one in south due to these conjugate normal faults. The interfluve area between these two rivers is uplifted as a result of vertical movements on the above mentioned faults. Four major terraces and some minor terraces are present along the major river valleys and these are formed due to episodic upliftment of the ground and subsequent down-cutting of the rivers. The uppermost terrace shows a northerly slope north of the Chalsa scarp as a result of folding mentioned above. But rivers on this terrace form incised channels keeping their flow southerly suggesting that they are antecedent to the folding and their downcutting kept pace with the tectonism.

  7. Three sets of crystallographic sub-planar structures in quartz formed by tectonic deformation

    NASA Astrophysics Data System (ADS)

    Derez, Tine; Pennock, Gill; Drury, Martyn; Sintubin, Manuel

    2016-05-01

    In quartz, multiple sets of fine planar deformation microstructures that have specific crystallographic orientations parallel to planes with low Miller-Bravais indices are commonly considered as shock-induced planar deformation features (PDFs) diagnostic of shock metamorphism. Using polarized light microscopy, we demonstrate that up to three sets of tectonically induced sub-planar fine extinction bands (FEBs), sub-parallel to the basal, γ, ω, and π crystallographic planes, are common in vein quartz in low-grade tectonometamorphic settings. We conclude that the observation of multiple (2-3) sets of fine scale, closely spaced, crystallographically controlled, sub-planar microstructures is not sufficient to unambiguously distinguish PDFs from tectonic FEBs.

  8. Using Google Earth to Explore Multiple Data Sets and Plate Tectonic Concepts

    NASA Astrophysics Data System (ADS)

    Goodell, L. P.

    2015-12-01

    Google Earth (GE) offers an engaging and dynamic environment for exploration of earth science data. While GIS software offers higher-level analytical capability, it comes with a steep learning curve and complex interface that is not easy for the novice, and in many cases the instructor, to negotiate. In contrast, the intuitive interface of GE makes it easy for students to quickly become proficient in manipulating the globe and independently exploring relationships between multiple data sets at a wide range of scales. Inquiry-based, data-rich exercises have been developed for both introductory and upper-level activities including: exploration of plate boundary characteristics and relative motion across plate boundaries; determination and comparison of short-term and long-term average plate velocities; crustal strain analysis (modeled after the UNAVCO activity); and determining earthquake epicenters, body-wave magnitudes, and focal plane solutions. Used successfully in undergraduate course settings, for TA training and for professional development programs for middle and high school teachers, the exercises use the following GE data sets (with sources) that have been collected/compiled by the author and are freely available for non-commercial use: 1) tectonic plate boundaries and plate names (Bird, 2003 model); 2) real-time earthquakes (USGS); 3) 30 years of M>=5.0 earthquakes, plotted by depth (USGS); 4) seafloor age (Mueller et al., 1997, 2008); 5) location and age data for hot spot tracks (published literature); 6) Holocene volcanoes (Smithsonian Global Volcanism Program); 7) GPS station locations with links to times series (JPL, NASA, UNAVCO); 8) short-term motion vectors derived from GPS times series; 9) long-term average motion vectors derived from plate motion models (UNAVCO plate motion calculator); 10) earthquake data sets consisting of seismic station locations and links to relevant seismograms (Rapid Earthquake Viewer, USC/IRIS/DELESE).

  9. Climate dominated topography in a tectonically active mountain range

    NASA Astrophysics Data System (ADS)

    Adams, B. A.; Ehlers, T. A.

    2015-12-01

    Tests of the interactions between tectonic and climate forcing on Earth's topography often focus on the concept of steady-state whereby processes of rock deformation and erosion are opposing and equal. However, when conditions change such as the climate or tectonic rock uplift, then surface processes act to restore the balance between rock deformation and erosion by adjusting topography. Most examples of canonical steady-state mountain ranges lie within the northern hemisphere, which underwent a radical change in the Quaternary due to the onset of widespread glaciation. The activity of glaciers changed erosion rates and topography in many of these mountain ranges, which likely violates steady-state assumptions. With new topographic analysis, and existing patterns of climate and rock uplift, we explore a mountain range previously considered to be in steady-state, the Olympic Mountains, USA. The broad spatial trend in channel steepness values suggests that the locus of high rock uplift rates is coincident with the rugged range core, in a similar position as high temperature and pressure lithologies, but not in the low lying foothills as has been previously suggested by low-temperature thermochronometry. The details of our analysis suggest the dominant topographic signal in the Olympic Mountains is a spatial, and likely temporal, variation in erosional efficiency dictated by orographic precipitation, and Pleistocene glacier ELA patterns. We demonstrate the same topographic effects are recorded in the basin hypsometries of other Cenozoic mountain ranges around the world. The significant glacial overprint on topography makes the argument of mountain range steadiness untenable in significantly glaciated settings. Furthermore, our results suggest that most glaciated Cenozoic ranges are likely still in a mode of readjustment as fluvial systems change topography and erosion rates to equilibrate with rock uplift rates.

  10. Glacial reorganization of topography in a tectonically active mountain range

    NASA Astrophysics Data System (ADS)

    Adams, Byron; Ehlers, Todd

    2016-04-01

    Tests of the interactions between tectonic and climate forcing on Earth's topography often focus on the concept of steady-state whereby processes of rock deformation and erosion are opposing and equal. However, when conditions change such as the climate or tectonic rock uplift, then surface processes act to restore the balance between rock deformation and erosion by adjusting topography. Most examples of canonical steady-state mountain ranges lie within the northern hemisphere, which underwent a radical change in the Quaternary due to the onset of widespread glaciation. The activity of glaciers changed erosion rates and topography in many of these mountain ranges, which likely violates steady-state assumptions. With new topographic analysis, and existing patterns of climate and rock uplift, we explore a mountain range previously considered to be in steady-state, the Olympic Mountains, USA. The details of our analysis suggest the dominant topographic signal in the Olympic Mountains is a spatial, and likely temporal, variation in erosional efficiency dictated by orographic precipitation, and Pleistocene glacier ELA patterns, and not tectonic rock uplift rates. Alpine glaciers drastically altered the relief structure of the Olympic Mountains. The details of these relief changes are recorded in channel profiles as overdeepenings, reduced slopes, and associated knickpoints. We find the position of these relief changes within the orogen is dependent on the position of the Pleistocene ELA. While alpine glaciers overdeepened valleys in regions near the Pleistocene ELA (which has a tendency to increase relief), headward erosion of west and north flowing glacier systems captured significant area from opposing systems and caused drainage divide lowering. This divide lowering reduced relief throughout the range. We demonstrate similar topographic effects recorded in the basin hypsometries of other Cenozoic mountain ranges around the world. The significant glacial overprint on

  11. Relief Evolution in Tectonically Active Mountain Ranges

    NASA Technical Reports Server (NTRS)

    Whipple, Kelin X.

    2004-01-01

    The overall aims of this 3-yr project, as originally proposed were to: (1) investigate quantitatively the roles of fluvial and glacial erosion in the evolution of relief in mountainous regions, and (2) test rigorously the quality and accuracy of SRTM topographic data in areas of rugged relief - both the most challenging and of greatest interest to geomorphic, neotectonic, and hazards applications. Natural laboratories in both the western US and the Southern Alps of New Zealand were identified as most promising. The project has been both successful and productive, despite the fact that no SRTM data for our primary field sites in New Zealand were released on the time frame of the work effort. Given the delayed release of SRTM data, we pursued the scientific questions of the roles of fluvial and, especially, glacial erosion in the evolution of relief in mountainous regions using available digital elevation models (DEMs) for the Southern Alps of New Zealand (available at both 25m and 50m pixel sizes), and USGS 10m and 30m DEMs within the Western US. As emphasized in the original proposal, we chose the emphasis on the role of glacial modification of topographic relief because there has been little quantitative investigation of glacial erosion processes at landscape scale. This is particularly surprising considering the dramatic sculpting of most mid- and high-latitude mountain ranges, the prodigious quantities of glacially-derived sediment in terrestrial and marine basins, and the current cross-disciplinary interest in the role of denudational processes in orogenesis and the evolution of topography in general. Moreover, the evolution of glaciated landscapes is not only a fundamental problem in geomorphology in its own right, but also is at the heart of the debate over Late Cenozoic linkages between climate and tectonics.

  12. 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.

  13. Lithosphere-asthenosphere Structure and Active Tectonics In Central Italy

    NASA Astrophysics Data System (ADS)

    Chimera, G.; Aoudia, A.; Saraò, A.; Panza, G. F.

    We investigate the lithosphere-asthenosphere structure and the active tectonics along a stripe from the Tyrrhenian to the Adriatic with emphasis on the Umbria-Marche area by means of surface-wave tomography, and inversion studies for structure and seismic moment tensor retrieval. The data include seismic waveforms, a large compilation of local group velocities (0.8-4s) and regional phase and group velocity (10-100s) measurements. The local group velocity maps cover the area reactivated by the 1997 Umbria-Marche earthquake sequence. These maps suggest a relation between the lat- eral heterogeneity and distribution of the active faults and related basins. Such relation is confirmed by the non-linear inversion of the local dispersion curves. To image the deeper structure from the Tyrrhenian to the Adriatic coast, we fix the uppermost part of the crust using the Umbria-Marche models along with the CROP03 profile and related shear wave velocity, and invert the additional long period dispersion measure- ments. The results of the inversion show the geometry and lateral heterogeneity of the lithosphere-asthenosphere system. The retrieved models for the Umbria-Marche up- per crust reveal the importance of the inherited compression on the ongoing extension and related seismic activity. The reactivated 1997 normal fault zone displays a thrust fault geometry as evidenced by the lateral extent of the faulted Late Triassic evap- orites that did not yet balance the cumulative normal faulting deformation attesting therefore recent extensional tectonics within the thrust belt. Our data are in favor of a listric geometry of faulting at depth. Source inversion studies of the two main crustal events of September 26 and October 14, 1997 show the dominance of normal faulting mechanisms, whereas selected aftershocks between the reactivated fault segments re- veal that the prevailing deformation at the step-over is of strike-slip faulting type. The rupture of the three distinct and

  14. Provenance analysis and tectonic setting of late Neoproterozoic metasedimentary successions in NW Argentina

    NASA Astrophysics Data System (ADS)

    Do Campo, M.; Guevara, S. Ribeiro

    2005-06-01

    Major, trace, and rare-earth element data for Puncoviscana Formation metasediments were used to constrain their provenance and tectonic setting. This unit, which crops out in northwest Argentina, consists mainly of pelite-greywacke turbidite sequences. Incipient regional metamorphism and a polyphase deformation, with a main deformation during the latest Proterozoic-earliest Cambrian Braziliano orogeny, affected the sedimentary sequences. The enrichment in light rare-earth and other incompatible trace elements over compatible ones, as well as the high and uniform Th/Sc ratios, indicate a predominance of upper-crust acid rocks as parental material. Some chemical characteristics of these rocks, such as their high Th/U, Rb/Sr, and Zr/Sc ratios, imply sedimentary recycling. On the basis of tectonic discriminant diagrams that employ trace elements considered relatively immobile during low-grade metamorphism, a passive margin setting can be inferred. Moreover, the comparison of the trace element contents of Puncoviscana metapelites with those of mudstones deposited in known tectonic settings shows the closest matching with passive margin shales.

  15. New insights into Wellington Harbours' tectonic settings from marine geophysical and sedimentological data

    NASA Astrophysics Data System (ADS)

    Woelz, Susi; Nodder, Scott; Barnes, Philip; Orpin, Alan

    2015-04-01

    After the experience of several damaging coastal earthquakes in New Zealand in the last three years, the importance of locating and characterising the earthquake potential of active faults close to urban areas has become more obvious, especially when cities lie in complex tectonic settings as it is the case for Wellington. To assess the earthquake and tsunami potential and the associated hazard posed by such faults, it is necessary to characterise fault geometry, slip rate, earthquake history and earthquake potential. In the marine environment, we have the advantage that faults can be assessed cross-sectionally through the application of high-resolution geophysical data without having to excavate trenches across the active fault trace. We present new marine data from Wellington Harbour that helps to characterise three faults; the Wellington Fault at Kaiwharawhara, the Evans Bay Fault, and a newly discovered fault off Oriental Bay, informally referred to as the Mount Victoria Fault. New marine geophysical data has better delineated the location and characteristics of these faults. High-resolution multi-beam bathymetric data (50 cm grid-cell size), covering the entire Wellington Harbour, were also used to determine the occurrence of seafloor scarps associated with surface ruptures on the faults. Sediment cores from either side of the Wellington Fault off Kaiwharawhara Stream, in about 17.5 m water depth, provide insight into the late Quaternary-Holocene stratigraphy and age of sediments that have been deformed by activity on the faults delineated in Wellington Harbour. The stratigraphy reveals details of the post-glacial marine flooding of the harbour that occurred about 10,000 years ago.

  16. Surface deformation and tectonic setting of Taiwan inferred from a GPS velocity field

    NASA Astrophysics Data System (ADS)

    Bos, Annemarie G.; Spakman, Wim; Nyst, Marleen C. J.

    2003-10-01

    We have determined the present-day surface deformation of Taiwan by computing the velocity gradient field and fault slip from 143 GPS velocity vectors. In southern Taiwan the derived strain and rotation rates and fault slips are indicative of lateral extrusion toward the south. In northern Taiwan we infer the onset of gravitational collapse which is induced by the on-land extension of the Okinawa Trough. In the eastern Central Range the observed inverted NW-SE extension is consistent with geological observations and high heat flow measurements. This could be the result of exhumation of crustal material. The model further shows a significant decrease in slip rate northward along the Longitudinal Valley fault at 23.7°N. The northern Coastal Range shows high strain rates and two oppositely rotating blocks. By combining the surface deformation model with seismicity data and seismic tomography we are able to propose a coherent model for the present-day tectonic activity. Both seismicity and tomography show further evidence for active, southward propagating exhumation of a crustal slice in the eastern Central Range. Offshore east Taiwan we deduce strong evidence of a southward propagating crustal tear fault, accommodating most of the Philippine Sea Plate-Eurasian Plate convergence. The tear is the crustal response to incipient northwestward subduction of the Philippine Sea Plate. Thus the Ryukyu Trench is bending southward becoming almost perpendicular to the convergence direction, while subduction of the Philippine Sea Plate continues. In this setting a sudden rapid southward propagation of the afore mentioned tear is conceivable.

  17. The seismicity of Ethiopia; active plate tectonics

    USGS Publications Warehouse

    Mohr, P.

    1981-01-01

    Ethiopia, descended from the semimythical Kingdom of Punt, lies at the strategic intersection of Schmidt's jigsaw puzzle where the Red Sea, Gulf of Aden, and the African Rift System meet. Because of geologically recent uplift combined with rapid downcutting erosion by rivers, notably the Blue Nile (Abbay), Ethiopia is the most mountainous country in Africa. It is also the most volcanically active, while its historical seismicity matches that of the midocean ridges. And, in a sense, Ethiopia is host to an evoloving ocean ridge system. 

  18. Active tectonic studies in the United States, 1987-1990

    SciTech Connect

    Weldon, R.J., II )

    1991-01-01

    The techniques and instrumentation used in active tectonic studies are discussed, and recent results are reviewed. It is suggested that a critical mass of data on several particular regions has been accumulated, making possible critical debates and attempts to assess earthquake hazards. Particular attention is given to studies of the Pacific Northwest region, basin and range deformation studies, and distributed deformation and hidden earthquake sources. Also included is a comprehensive bibliography for the period.

  19. Northeast Basin and Range province active tectonics: An alternative view

    SciTech Connect

    Westaway, R. )

    1989-09-01

    Slip rates and slip vector azimuths on major active oblique normal faults are used to investigate whether circulation associated with the Yellowstone upwelling plume is driving tectonic deformation in the northeast Basin and Range province. Observed deformation is consistent with this suggestion; the plume is sheared to the southwest by motion of the North American plate. Testable predictions are made for structure and evolution of the region.

  20. A Digital Tectonic Activity Map of the Earth

    NASA Technical Reports Server (NTRS)

    Lowman, Paul; Masuoka, Penny; Montgomery, Brian; OLeary, Jay; Salisbury, Demetra; Yates, Jacob

    1999-01-01

    The subject of neotectonics, covering the structures and structural activity of the last 5 million years (i.e., post-Miocene) is a well-recognized field, including "active tectonics," focussed on the last 500,000 years in a 1986 National Research Council report of that title. However, there is a cartographic gap between tectonic maps, generally showing all features regardless of age, and maps of current seismic or volcanic activity. We have compiled a map intended to bridge this gap, using modern data bases and computer-aided cartographic techniques. The maps presented here are conceptually descended from an earlier map showing tectonic and volcanic activity of the last one million years. Drawn by hand with the National Geographic Society's 1975 "The Physical World" map as a base, the 1981 map in various revisions has been widely reproduced in textbooks and various technical publications. However, two decades of progress call for a completely new map that can take advantage of new knowledge and cartographic techniques. The digital tectonic activity map (DTM), presented in shaded relief (Fig. 1) and schematic (Fig. 2) versions, is the result. The DTM is intended to show tectonism and volcanism of the last one million years, a period long enough to be representative of global activity, but short enough that features such as fault scarps and volcanos are still geomorphically recognizable. Data Sources and Cartographic Methods The DTM is based on a wide range of sources, summarized in Table 1. The most important is the digital elevation model, used to construct a shaded relief map. The bathymetry is largely from satellite altimetry, specifically the marine gravity compilations by Smith and Sandwell (1996). The shaded relief map was designed to match the new National Geographic Society world physical map (1992), although drawn independently, from the digital elevation model. The Robinson Projection is used instead of the earlier Van der Grinten one. Although neither

  1. Mid-Cenozoic tectonic and paleoenvironmental setting of the central Arctic Ocean

    NASA Astrophysics Data System (ADS)

    O'Regan, Matthew; Moran, Kathryn; Backman, Jan; Jakobsson, Martin; Sangiorgi, Francesca; Brinkhuis, Henk; Pockalny, Rob; Skelton, Alasdair; Stickley, Catherine; Koç, Nalan; Brumsack, Hans-Jürgen; Willard, Debra

    2008-03-01

    Drilling results from the Integrated Ocean Drilling Program's Arctic Coring Expedition (ACEX) to the Lomonosov Ridge (LR) document a 26 million year hiatus that separates freshwater-influenced biosilica-rich deposits of the middle Eocene from fossil-poor glaciomarine silty clays of the early Miocene. Detailed micropaleontological and sedimentological data from sediments surrounding this mid-Cenozoic hiatus describe a shallow water setting for the LR, a finding that conflicts with predrilling seismic predictions and an initial postcruise assessment of its subsidence history that assumed smooth thermally controlled subsidence following rifting. A review of Cenozoic tectonic processes affecting the geodynamic evolution of the central Arctic Ocean highlights a prolonged phase of basin-wide compression that ended in the early Miocene. The coincidence in timing between the end of compression and the start of rapid early Miocene subsidence provides a compelling link between these observations and similarly accounts for the shallow water setting that persisted more than 30 million years after rifting ended. However, for much of the late Paleogene and early Neogene, tectonic reconstructions of the Arctic Ocean describe a landlocked basin, adding additional uncertainty to reconstructions of paleodepth estimates as the magnitude of regional sea level variations remains unknown.

  2. Mid-Cenozoic tectonic and paleoenvironmental setting of the central Arctic Ocean

    USGS Publications Warehouse

    O'Regan, M.; Moran, K.; Backman, J.; Jakobsson, M.; Sangiorgi, F.; Brinkhuis, Henk; Pockalny, Rob; Skelton, Alasdair; Stickley, Catherine E.; Koc, N.; Brumsack, Hans-Juergen; Willard, Debra A.

    2008-01-01

    Drilling results from the Integrated Ocean Drilling Program's Arctic Coring Expedition (ACEX) to the Lomonosov Ridge (LR) document a 26 million year hiatus that separates freshwater-influenced biosilica-rich deposits of the middle Eocene from fossil-poor glaciomarine silty clays of the early Miocene. Detailed micropaleontological and sedimentological data from sediments surrounding this mid-Cenozoic hiatus describe a shallow water setting for the LR, a finding that conflicts with predrilling seismic predictions and an initial postcruise assessment of its subsidence history that assumed smooth thermally controlled subsidence following rifting. A review of Cenozoic tectonic processes affecting the geodynamic evolution of the central Arctic Ocean highlights a prolonged phase of basin-wide compression that ended in the early Miocene. The coincidence in timing between the end of compression and the start of rapid early Miocene subsidence provides a compelling link between these observations and similarly accounts for the shallow water setting that persisted more than 30 million years after rifting ended. However, for much of the late Paleogene and early Neogene, tectonic reconstructions of the Arctic Ocean describe a landlocked basin, adding additional uncertainty to reconstructions of paleodepth estimates as the magnitude of regional sea level variations remains unknown.

  3. Tectonic activity and the evolution of submarine canyons: The Cook Strait Canyon system, New Zealand

    NASA Astrophysics Data System (ADS)

    Micallef, Aaron; Mountjoy, Joshu; Barnes, Philip; Canals, Miquel; Lastras, Galderic

    2016-04-01

    Submarine canyons are Earth's most dramatic erosional features, comprising steep-walled valleys that originate in the continental shelf and slope. They play a key role in the evolution of continental margins by transferring sediments into deep water settings and are considered important biodiversity hotspots, pathways for nutrients and pollutants, and analogues of hydrocarbon reservoirs. Although comprising only one third of continental margins worldwide, active margins host more than half of global submarine canyons. We still lack of thorough understanding of the coupling between active tectonics and submarine canyon processes, which is necessary to improve the modelling of canyon evolution in active margins and derive tectonic information from canyon morphology. The objectives of this study are to: (i) understand how tectonic activity influences submarine canyon morphology, processes, and evolution in an active margin, and (2) formulate a generalised model of canyon development in response to tectonic forcing based on morphometric parameters. We fulfil these objectives by analysing high resolution geophysical data and imagery from Cook Strait Canyon system, offshore New Zealand. Using these data, we demonstrate that tectonic activity, in the form of major faults and structurally-generated tectonic ridges, leaves a clear topographic signature on submarine canyon location and morphology, in particular their dendritic and sinuous planform shapes, steep and linear longitudinal profiles, and cross-sectional asymmetry and width. We also report breaks/changes in canyon longitudinal slope gradient, relief and slope-area regression models at the intersection with faults. Tectonic activity gives rise to two types of knickpoints in the Cook Strait Canyon. The first type consists of low slope gradient, rounded and diffusive knickpoints forming as a result of short wavelength folds or fault break outs and being restored to an equilibrium profile by upstream erosion and

  4. Quantative determination of geological and tectonic development under complex geological settings - Thrace Area, Turkey

    SciTech Connect

    Erdogan, L.T. ); Yuekler, M.A.

    1990-05-01

    Thrace area is composed of several subbasins, formed during the middle Eocene, overlying the metamorphic and granitic rocks of the Istranca Massif. Syndepositional fault patterns and variations in sedimentary thicknesses indicate that the subbasins evolved tectonically by northeast-southwest extension from the middle Eocene to early Paleocene. From the early Paleocene to early Miocene, the northern part of the area underwent northeast-southwest extension, whereas in the middle Miocene, northwest-southeast wrench-fault assemblage resulted in a clockwise rotation of the extension axes. Consequently, the right-lateral motion of the transform faults resulted in a north-south extension which prevailed until the late Pleistocene. During the last 1 m.y., the area was subjected to a major compression leading to rapid erosion in the central part of the area. A deterministic three-dimensional basin analysis model has been applied to quantify the geological and tectonic evolution of the subbasins. A total of 72 wells were simulated to determine compaction pressure, and temperature histories of the sedimentary sequences to set up the conceptual model. The validity of the conceptual model was then checked with the simulation of six seismic profiles before the full three-dimensional simulation of the area. The trends from the computed subsidence and uplift heat flow, and compaction maps as a function of time were checked against the observed stratigraphic and sedimentological data. The excellent match between the computed trends and observed isopachs, and erosions as determined from seismic data and depositional environments, aided in the quantification of the regional stratigraphy and tectonics. The combination of the computed heat flow and uncompacted isopach maps was used in determining stress-strain relationships in the subbasins as a function of time.

  5. Thin-skinned salt tectonics as a response to crustal movements in a recent convergent setting

    NASA Astrophysics Data System (ADS)

    Vendeville, Bruno; Gaullier, Virginie; Deverchere, Jacques; Sage, Françoise

    2014-05-01

    Published data from the seismic survey "MARADJA 1" conducted in August and September 2003 offshore the Algerian coast have imaged the Messinian salt response to tectonic activity within the basement. This helps to understand how the vertical movements of basement blocks have been recorded by thin-skinned salt tectonics. The area is undergoing crustal convergence, as attested by the Boumerdes earthquake (magnitude 6.8), which happened in 2003. The seismic data have revealed the presence of an elevated plateau, forming a 3D promontory restricted to the area offshore Algiers and is absent west and east of that area. The promontory is likely related to the contractional reactivation of the margin, as was recorded by subsalt thrusts mapped by Domzig et al. (2006). The data provided additional information on the deformation of the Messinian mobile evaporite unit and its Plio-Quaternary overburden. Margin-perpendicular profiles show mostly compressional features (anticlines and synclines) that had little or no activity during Messinian times. By contrast, margin-parallel profiles clearly show that extensional, reactive salt diapiric ridges formed early, as early as the time of deposition of the Messinian Upper Unit, as recorded by fan-shaped strata. These ridges have recorded E-W, thin-skinned gravity gliding above the Messinian salt, as a response to the rise of the basement plateau. We tested this hypothesis using analogue models. Indeed, the rise of the plateau generated preferential E-W extension above the salt, rather than N-S, which was prevented by the compressional regional tectonic stresses related to the convergence of the African and European plates.

  6. Crustal structure and active tectonics in the Eastern Alps

    NASA Astrophysics Data System (ADS)

    Brückl, E.; Behm, M.; Decker, K.; Grad, M.; Guterch, A.; Keller, G. R.; Thybo, H.

    2010-04-01

    During the last decade, a series of controlled source seismic experiments brought new insight into the crustal and lithospheric structure of the Eastern Alps and their adjacent tectonic provinces. A fragmentation of the lithosphere into three blocks, Europe (EU), Adria (AD), and the new Pannonian fragment (PA), was interpreted and a triple junction was inferred. The goal of this study has been to relate these deep crustal structures to active tectonics. We used elastic plate modeling to reconsider the Moho fragmentation. We interpret subduction of EU below AD and PA from north to south and underthusting of AD mantle below PA from southwest to northeast. The Moho fragmentation correlates well with major upper crustal structures and is supported by gravity, seismic, and geodetic data. An analysis of crustal thickening suggests that active convergence is associated with continued thrusting and lateral extrusion in the central Eastern Alps and thickening of the Adriatic indenter under the Southern Alps. According to the velocity relations at the triple junction, PA moves relative to EU and AD along ENE and SE striking faults, mainly by strike slip. An eastward directed extensional component is compensated by the lateral extrusion of the central Eastern Alps. The Periadriatic (Insubric) line east of the triple junction and the mid-Hungarian fault zone have relatively recently lost their role as first-order active structures. We favor the idea that the Pannonian fragment and the TISZA block merged to a "soft" microplate surrounded by the Eastern and Southern Alpine, Carpathian, and Dinaric orogens.

  7. Tectonic setting of the low-grade metamorphic rocks of the Dabie Orogen, central eastern China

    NASA Astrophysics Data System (ADS)

    Xu, Shutong; Wu, Weiping; Lu, Yiqun; Wang, Dehua

    2012-04-01

    The tectonic setting on both the northern and southern sides of the Dabie Mountains reveals that low-grade metamorphic rocks are important constituents produced by the subduction of the oceanic crust prior to collision between the Sino-Korean and Yangtze cratons. The Zhangbaling Group/Mulanshan schist is a pre-Ordovician oceanic crust. The Sujiahe and Xinyang/Foziling Groups are trench sediments of the Ordovician-Devonian age, and constitute an accretionary prism associated with subduction. The Yangshan coal measures/Meishan Group was a forearc basin sediment of Carboniferous age, and was overthrust by the accretionary prism during collision. The Susong Group is composed of passive continental margin sediments of the Yangtze craton. Backarc basin sediments are postulated to be concealed by Mesozoic-Cenozoic sediments to the north of the Dabie Mountains. High-ultrahigh pressure terrains are exotic tectonic slices exhumed from depths, located between low-grade metamorphic rocks, and disturb the integrity of the earlier subduction orogen. Subduction occurred during the Ordovician to Devonian periods, and collision initiated at the beginning of the Permian.

  8. Geochemical indicators of provenance and tectonic setting of Mississippian pelites of the Ouachita fold belt

    SciTech Connect

    Totten, M.W. ); Blatt, H.; Weaver, B.L. )

    1992-01-01

    Plate tectonic reconstructions of the southern continental margin of North America during the Paleozoic are inconclusive. Numerous conflicting models have been proposed for the opening and closing of the Iapetus Ocean and the subsequent deposition and deformation of the Ouachita System. Considerable confusion also exists concerning the provenance of the Carboniferous flysch deposits of the Ouachitas. Trace element geochemistry of shales from the Stanley Group constrain both the provenance of the sediments and the plate tectonic setting during the Mississippian evolution of the southern continental margin. Th/Sc and Cr/Th ratios support a cratonic source for the majority of samples analyzed. However, in several samples the Th/Sc ratio decreases and the Cr/Th ratio increases, suggesting a contribution from a more mafic source. Using element ratio-ratio diagrams, all of the samples plot along a curve consistent with a two-component mixing model between a felsic and a mafic source. Both a tantalum-niobium trough and a strongly negative strontium anomaly are seen in upper-crust-normalized trace element spiderdiagrams. These anomalies are also present in interbedded volcaniclastics within the Stanley. The Stanley shales also exhibit a positive vanadium-chromium-nickel anomaly. The pervasive occurrence of these anomalies is interpreted as inherited from their source, and not from diagenetic alteration or sedimentary processes.

  9. Tectonic activity evolution of the Scotia-Antarctic Plate boundary from mass transport deposit analysis

    NASA Astrophysics Data System (ADS)

    Pérez, Lara F.; Bohoyo, Fernando; Hernández-Molina, F. Javier; Casas, David; Galindo-Zaldívar, Jesús; Ruano, Patricia; Maldonado, Andrés.

    2016-04-01

    The spatial distribution and temporal occurrence of mass transport deposits (MTDs) in the sedimentary infill of basins and submerged banks near the Scotia-Antarctic plate boundary allowed us to decode the evolution of the tectonic activity of the relevant structures in the region from the Oligocene to present day. The 1020 MTDs identified in the available data set of multichannel seismic reflection profiles in the region are subdivided according to the geographic and chronological distributions of these features. Their spatial distribution reveals a preferential location along the eastern margins of the eastern basins. This reflects local deformation due to the evolution of the Scotia-Antarctic transcurrent plate boundary and the impact of oceanic spreading along the East Scotia Ridge (ESR). The vertical distribution of the MTDs in the sedimentary record evidences intensified regional tectonic deformation from the middle Miocene to Quaternary. Intensified deformation started at about 15 Ma, when the ESR progressively replaces the West Scotia Ridge (WSR) as the main oceanic spreading center in the Scotia Sea. Coevally with the WSR demise at about 6.5 Ma, increased spreading rates of the ESR and numerous MTDs were formed. The high frequency of MTDs during the Pliocene, mainly along the western basins, is also related to greater tectonic activity due to uplift of the Shackleton Fracture Zone by tectonic inversion and extinction of the Antarctic-Phoenix Ridge and involved changes at late Pliocene. The presence of MTDs in the southern Scotia Sea basins is a relevant indicator of the interplay between sedimentary instability and regional tectonics.

  10. Variations in magma supply and magma partitioning: the role of tectonic settings

    NASA Astrophysics Data System (ADS)

    Takada, Akira

    1999-11-01

    Magma supply rates for 200 years at Krafla and Lakagigar, Iceland, and those for 150 years at Kilauea and Mauna Loa, Hawaii, are estimated roughly, based on their geophysical and geological observations. A diagram that relates erupted volumes to eruption intervals at volcanoes under various tectonic settings is represented. These results lead to a new model that a large volume (1-10 km 3) of magma is supplied intermittently at a long interval (10 2-10 4 years) beneath volcanoes in rift zones, while magma is supplied continuously with oscillations or fluctuations beneath intraplate volcanoes. Chemical data such as the MgO wt.% of lava may be one indicator in evaluating the magma supply rates of Hawaiian volcanoes. Systematic variation with time in magma partitioning within a volcano or to the surface is obtained in comparisons between among migration patterns of eruption sites, cumulative supplied volumes, and the volume ratios of erupted to supplied magma at Krafla and Kilauea. The variations suggest that a magma plumbing system may act under self-control (regulating) system through stress as one system. In response to a change in magma supply rate, the system partitions magma horizontally into dikes or vertically toward the surface. A large magma supply rate promotes the vertical extent of a crack to result in an eruption with a large volume ratio of erupted to supplied magma. This tendency is supported by field observations of flood basalts. The partitioned magma as dike intrusions suppresses magma supply partially in the shallow crust. Using analog experiments on liquid-filled cracks in gelatin, this paper demonstrates fundamental processes for magma partitioning on the effect of magma supply and stress change by the partitioned magma. A dynamical system of two differential equations on magma supply rate and stress around a magma plumbing system is proposed, to understand the qualitative variations in magma supply rate imposed by tectonic settings.

  11. The Moho in extensional tectonic settings: insights from thermo-mechanical models

    NASA Astrophysics Data System (ADS)

    Cloetingh, Sierd; Burov, Evgenii; Liviu, Matenco

    2013-04-01

    We review consequences for the crustal and lithospheric configuration of different models for the thermo-mechanical evolution of continental lithosphere in extensional tectonic settings. The lithospheric memory is key for the interplay of lithospheric stresses and rheological structure of the extending lithosphere and for its later tectonic reactivation. Other important factors are the temporal and spatial migration of extension and the interplay of rifting and surface processes. The mode of extension and the duration of the rifting phase required to lead to continental break-up is to a large extent controlled by the interaction of the extending plate with slab dynamics. We compare predictions from numerical models with observational constraints from a number of rifted back-arc basin settings and intraplate domains at large distance from convergent plate boundaries. We discuss the record of vertical motions during and after rifting in the context of stretching models developed to quantify rifted basin formation. The finite strength of the lithosphere has an important effect on the formation of extensional basins. This applies both to the geometry of the basin shape as well as to the record of vertical motions during and after rifting. We demonstrate a strong connection between the bulk rheological properties of Europe's lithosphere and the evolution of some of Europe's main rifts and back-arc system. The thermomechanical structure of the lithosphere has a major impact on continental breakup and associated basin migration processes, with direct relationships between rift duration and extension velocities, thermal evolution, and the role of mantle plumes. Compressional reactivation has important consequences for post-rift inversion, borderland uplift, and denudation, as illustrated by polyphase deformation of extensional back-arc basins in the Black Sea and the Pannonian Basin.

  12. Drilling to investigate processes in active tectonics and magmatism

    NASA Astrophysics Data System (ADS)

    Shervais, J.; Evans, J.; Toy, V.; Kirkpatrick, J.; Clarke, A.; Eichelberger, J.

    2014-12-01

    Coordinated drilling efforts are an important method to investigate active tectonics and magmatic processes related to faults and volcanoes. The US National Science Foundation (NSF) recently sponsored a series of workshops to define the nature of future continental drilling efforts. As part of this series, we convened a workshop to explore how continental scientific drilling can be used to better understand active tectonic and magmatic processes. The workshop, held in Park City, Utah, in May 2013, was attended by 41 investigators from seven countries. Participants were asked to define compelling scientific justifications for examining problems that can be addressed by coordinated programs of continental scientific drilling and related site investigations. They were also asked to evaluate a wide range of proposed drilling projects, based on white papers submitted prior to the workshop. Participants working on faults and fault zone processes highlighted two overarching topics with exciting potential for future scientific drilling research: (1) the seismic cycle and (2) the mechanics and architecture of fault zones. Recommended projects target fundamental mechanical processes and controls on faulting, and range from induced earthquakes and earthquake initiation to investigations of detachment fault mechanics and fluid flow in fault zones. Participants working on active volcanism identified five themes: the volcano eruption cycle; eruption sustainability, near-field stresses, and system recovery; eruption hazards; verification of geophysical models; and interactions with other Earth systems. Recommended projects address problems that are transferrable to other volcanic systems, such as improved methods for identifying eruption history and constraining the rheological structure of shallow caldera regions. Participants working on chemical geodynamics identified four major themes: large igneous provinces (LIPs), ocean islands, continental hotspot tracks and rifts, and

  13. Areas of Unsolved Problems in Caribbean Active Tectonics

    NASA Astrophysics Data System (ADS)

    Mann, P.

    2015-12-01

    I review some unsolved problems in Caribbean active tectonics. At the regional and plate scale: 1) confirm the existence of intraplate deformation zones of the central Caribbean plate that are within the margin of error of ongoing GPS measurements; 2) carry out field studies to evaluate block models versus models for distributed fault shear on the densely populated islands of Jamaica, Hispaniola, Puerto Rico, and the Virgin Islands; 3) carry out paleoseismological research of key plate boundary faults that may have accumulated large strains but have not been previously studied in detail; 4) determine the age of onset and far-field effects of the Cocos ridge and the Central America forearc sliver; 4) investigate the origin and earthquake-potential of obliquely-sheared rift basins along the northern coast of Venezuela; 5) determine the age of onset and regional active, tectonic effects of the Panama-South America collision including the continued activation of the Maracaibo block; and 6) validate longterm rates on active subduction zones with improving, tomographic maps of subducted slabs. At the individual fault scale: 1) determine the mode of termination of large and active strike -slip faults and application of the STEP model (Septentrional, Polochic, El Pilar, Bocono, Santa Marta-Bucaramanaga); 2) improve the understanding of the earthquake potential on the Enriquillo-Plantain Garden fault zone given "off-fault" events such as the 2010 Haiti earthquake; how widespread is this behavior?; and 3) estimate size of future tsunamis from studies of historic or prehistoric slump scars and mass transport deposits; what potential runups can be predicted from this information?; and 4) devise ways to keep rapidly growing, circum-Caribbean urban populations better informed and safer in the face of inevitable and future, large earthquakes.

  14. Active Tectonics And Modern Geodynamics Of Sub-Yerevan Region

    NASA Astrophysics Data System (ADS)

    Avanesyan, M.

    2004-05-01

    The given work is dedicated to active tectonics and modern geodynamics of Sub-Yerevan region. This region is interesting as a one of regions with maximal seismic activity in Armenia. The high level of seismic risk of this region is conditioned by high level of seismic hazard, high density of the population, as well as presence of objects of special importance and industrial capacities. The modern structure of Sub-Yerevan region and the adjacent area, as well as the Caucasus entirely, has mosaic-block appearance, typical for collision zone of Arabian and Eurasian plates. Distinctively oriented active faults of various ranges and morphological types are distinguished. These faults, in their turn, form various-scale active blocks of the Earth's crust and their movement defines seismic activity of the region. The researches show, that all strong earthquakes in the region were caused by movements by newest and activated ancient faults. In order to reveal the character of Earth's crust active blocks movement, separation of high gradients of horizontal and vertical movements and definition of stress fields highest concentration regions by GPS observations, high-accuracy leveling and study of earthquake focal mechanisms a new seismotectonic model is developed, which represents a combination of tectonic structure, seismic data, newest and modern movements. On the basis of comparison and analysis of these data zones with potential maximal seismic hazard are separated. The zone of joint of Azat-Sevan active and Yerevan abysmal faults is the most active on the territory of Sub-Yerevan region. The directions relatively the Earth's crust movement in the zones of horizontal and vertical movement gradients lead to conclusion, that Aragats-Tsakhkunian and Gegam active blocks undergo clockwise rotation. This means, that additional concentration of stress must be observed in block corners, that is confirmed by location of strong earthquakes sources. Thus, on the North 1988 Spitak (M

  15. Active Tectonics in the Ohrid Basin (Macedonia/Albania)

    NASA Astrophysics Data System (ADS)

    Reicherter, K.; Hoffmann, N.; Fernández-Steeger, T.

    2009-04-01

    The Ohrid Basin is a major N-S trending graben structure located on the border of Macedonia and Albania, associated with other basins (Korce basin) in the Dinaride mountain belt. Within the basin an "ancient lake" developed since the Late Miocene/Pliocene with almost 290 m water depth. Since the beginning of basin formation around 700 m of sediment accumulated in the lake, the initial stage of subsidence is triggered either by extension or strike-slip movements. The general geodynamic setting of the Lake Ohrid area can be described with a "basin and range" situation. The multidisciplinary ICDP-SCOPSCO initiative is currently investigating Lake Ohrid and its environs. The central mountain chain, especially the intramontane basins of Late Neogene age, form one of the most active seismic zones in Albania/Macedonia with several moderate earthquakes reported during the last few centuries (Muço 1998; NEIC database, USGS). Major earthquakes occurred during historical times. Lychnidos (the ancient city of Ohrid) was destroyed completely by an earthquake in 526 AD. It was rebuilt by Emperor Justinian (527-565), who was born in the vicinity, and was called by him Justiniana Prima, i.e. the most important of the several new cities that bore his name. The last prominent earthquake took place in on 18th February 1911 at 21.35 close to Lake Ohrid Basin, (M 6.7, corresponding to EMS X; 15 km depth, N 40.9°, E 20,8°). The last earthquake occurred on Jan 8th 2009 with a magnitude of 4.9 close to the lake. Hypocenter depths scatter between 10 and 25 km but some deeper earthquakes occur between 25 and 50 km depth. Very rarely intermediate earthquakes around 100 km depth are observed. Small and moderate earthquakes (< M 5.5) take place predominantly along major fault zones, and are concentrated along the margins of the Ohrid Basin. The Ohrid-Korça Zone is considered to be the region of the highest seismic hazard in the Albanian-Macedonian Corridor based on present-day seismicity

  16. Mid-Pleistocene to present stratigraphic responses in a tectonically-driven depositional setting: Eel River Basin, Northern California

    NASA Astrophysics Data System (ADS)

    Burger, Robert Lawrence

    The Eel River Basin of northern California is an actively deforming forearc basin, affected today by Gorda-North America Plate convergence, northward migration of the Mendocino Triple Junction, glacioeustatic sea-level fluctuations that periodically exposed the continental shelf, and high rates of sediment input. A high-resolution multichannel seismic reflection survey of the shelf and upper slope has been conducted as part of the Office of Naval Research STRATAFORM initiative, with the goal of understanding processes affecting sediment dispersal and preservation in this complex continental margin setting. Interpretations of the seismic images indicate that, although tectonism strongly overprints preserved sequence morphologies, glacioeustacy is of primary importance in the distribution and preservation of sediments along this margin. On the shelf, stacked sequences dominated by interpreted highstand marine sediment are separated by prominent ravinement surfaces formed during sea-level transgressions. Folding and faulting locally modify sequence morphologies. At the south end of the seismic grid, localized uplift attributed to Mendocino Triple Junction encroachment overrides the glacioeustatic stacking pattern dominant over the rest of the shelf, inducing shelf incision and preferential preservation of vertically stacked channel-fills. An abrupt shift in shelf sequence morphology ˜500 ka suggests that the triple junction began to affect the southern basin at that time, by decreasing accommodation space marginwide. On the adjacent slope, effects of tectonism and glacioeustacy can also be discerned. In the south, the Humboldt Slide is identified as a long-lived masswasting feature, likely triggered by triple junction-related uplift and associated seismicity ˜450--500 ka. However, a cyclical succession of contrasting lithologies is also apparent in the deformed slide sequences, which I attribute to glacioeustatic cyclicity. To the north, effects of regional

  17. The Circum-Rhodope Belt, northern Greece: Age, provenance, and tectonic setting

    NASA Astrophysics Data System (ADS)

    Meinhold, Guido; Kostopoulos, Dimitrios K.

    2013-06-01

    The Circum-Rhodope Belt (CRB) sensu stricto comprises low-grade metamorphosed Triassic and Jurassic sedimentary rocks fringing the high-grade metamorphic rocks of the Serbo-Macedonian and Rhodope massifs in northern Greece. Main outcrops occur in the easternmost part of the Vardar suture zone in the Chalkidiki peninsula (Melissochori Formation; formerly Svoula flysch) and in Thrace (Makri unit and Melia Formation). The tectonostratigraphic relationship between the CRB and the high-grade metamorphics has been the subject of long discussions. Older interpretations maintain that the CRB represents the original Mesozoic stratigraphic cover of the Serbo-Macedonian crystalline basement, whereas later revisions propose the existence of two distinct greenschist-facies Mesozoic metasedimentary units: an eastern unit related to the development of a Jurassic black shale basin north of the Rhodope, and a western unit related to the development of an olistostromic flysch in the Cretaceous. Here we present a critical re-evaluation of the CRB with regard to its age, provenance, and tectonic setting based on novel geochemical and isotopic data. The Makri unit and the Melissochori Formation belong to the CRB proper and were deposited in proximity to Carboniferous-Early Permian igneous basement rocks (Pelagonia / Strandja / Thracia Terrane) in latest Triassic and Jurassic times, as shown by a prominent detrital zircon age population of 350-290 Ma. By contrast, the Melia Formation is unrelated to the CRB and was deposited in a foreland basin in front of a metamorphic nappe pile with Rhodopean affinities in the early Cretaceous, as shown by a prominent detrital zircon age population of 315-285 Ma and xenocrysts of ~ 550 Ma and ~ 450 Ma. Thus, the commonly accepted CRB concepts have to be revisited. All units have been tectonically juxtaposed to their present location during Balkan and Alpine orogenic processes.

  18. Seismicity studies and tectonic settings of the Caucasus; The past and the Future

    NASA Astrophysics Data System (ADS)

    Javakishvili, Z.; Karakhanyan, A.; Yetirmishli, G.

    2012-12-01

    The Caucasus as a part of continent-continent collision of Arabian and Eurasian plates is tectonically complicated region, containing many structural formations: thrusts, tectonic nappes, buried folds, normal, reverse, and strike-slip faults and other seismically active structures. This complexity is most likely to be responsible for the widespread diffuse character of seismicity. The Caucasus suffered from several devastating earthquakes in the past: such as Shemakha earthquake of 1668, M=7.5, I0 =10 (MSK scale), Alaverdi earthquake of 1742, Ms=6.8, I0=9 and the Lechkhumi-Svaneti earthquake of 1350, Ms=7.0, I0 =9 …; during instrumental period the strongest earthquakes occurred in 1988 in Armenia - Spitak earthquake 1988, M=7.0, I0=9-10(MSK scale) and in Georgia-Racha earthquake 1991, Ms=7.0, I0 =9. The earthquakes have dramatically demonstrated that future earthquakes can cause tremendous loss of human life and property. Insufficient or inadequate awareness of the population and governments regarding the actual hazard and risk in their own and neighboring countries is one of the factors that complicate mutual understanding between the countries of the region. Protection of the environment, natural hazard assessment and reduction requires developing infrastructure, capability and regionally coordinated planning for response to disasters. The proper assessment of a natural hazard should be based on an optimally selected monitoring network. In the case of a strong earthquake that affects also neighboring countries. It is necessary to use similar sensors, systems, data collection and processing methodology as well as have an agreed upon strategy for response. To investigate the problem of seismicity; tectonics and seismic hazard analysis it is necessary to establish a modern regional monitoring network comprised of high-sensitivity digital seismographs. During the last years, after a decade of collapse in the field of seismic monitoring, all countries of the

  19. Early Miocene Tectonic Activity in the western Ross Sea (Antarctica)

    NASA Astrophysics Data System (ADS)

    Sauli, C.; Sorlien, C. C.; Busetti, M.; Geletti, R.; De Santis, L.

    2012-12-01

    In the framework of the Rossmap Italian PNRA work objectives to compile extended and revised digital maps of the main unconformities in Ross Sea, Antarctica, much additional seismic reflection data, that were not available to previous ANTOSTRAT compilation, were incorporated into a new ROSSMAP interpretation. The correlation across almost all of Ross Sea, from DSDP Site 270 and Site 272 in Eastern Basin to northern Victoria Land Basin, of additional early Miocene and late Oligocene horizons that were not part of ANTOSTRAT allows interpretations to be made of fault activity and glacial erosion or deposition at a finer time resolution. New conclusions include that extensional or transtensional fault activity within the zone between Victoria Land Basin and Northern Basin, initiated by 23 Ma or earlier, and continued after 18 Ma. Steep parallel-striking faults in southern Victoria Land Basin display both reverse and normal separation of 17.5 Ma (from Cape Roberts Program-core 1) and post-16 Ma horizons, suggesting an important strike-slip component. This result may be compared with published papers that proposed post-17 Ma extension in southern Victoria Land Basin, 16-17 Ma extension in the AdareTrough, north of the Ross Sea continental shelf, but no Miocene extension affecting the Northern Basin (Granot et al., 2010). Thus, our evidence for extension through the early Miocene is significant to post-spreading tectonic models. Reference Granot R., Cande S. C., Stock J. M., Davey F. J. and Clayton R. W. (2010) Postspreading rifting in the Adare Basin, Antarctica: Regional tectonic consequences. Geochem. Geophys. Geosyst., 8, Q08005, doi:10.1029/2010GC003105.

  20. The tectonic development of south-central Asia and the paleogeographic setting of its hydrocarbon resources

    SciTech Connect

    Scotese, C.R. ); Tyrell, W.W. Jr. ); Maher, K.A. )

    1990-05-01

    The countries of south-central Asia (Afghanistan to Thailand) are made up of fragments of Gondwana that collided with the southern margin of Eurasia during the Mesozoic and Cenozoic. The Cimmerian terranes (Turkey, Iran, Afghanistan, Qiang Tang, and Burma-Malaya) rifted away from Gondwana beginning in the Late Carboniferous and were accreted to Asia during the Late Triassic-Jurassic. The Lhasa terrane, presumably also derived from Gondwana, was accreted during the Late Jurassic. By the Early Cretaceous, India-Madagascar had separated from Africa and from Australia-Antarctica. In the middle Cretaceous, India rapidly rifted away from Madagascar, and during the early Eocene collided with Asia giving rise to the Tibetam Plateau and the mountain belts from Afghanistan through Burma. The sedimentary basins and petroleum provinces adjacent to and south of these collision zones are best understood when viewed in the context of their tectonic history and paleogeographic setting. About 7 billion bbl of oil and 50 tcf of gas have been discovered in south-central Asia, mostly in Cenozoic deltaic sandstones or marine carbonate reservoirs in rift (Cambay), passive margin (Bombay shelf), and foreland basins (Assam, Indux, Potwar, Bengal) in India, Pakistan, and Bangladesh, and in a fore-arc setting in Burma. Source rocks are mostly Paleogene shale, but some Paleozoic and Mesozoic sources be present in Pakistan. New exploration is underway or will begin soon in India, Bangladesh, Nepal, and Burma.

  1. Discussions on the sedimentary-tectonic event and tectonic setting of the North Tarim Basin in Cryogenian-Cambrian

    NASA Astrophysics Data System (ADS)

    Zhou, X. B.; Li, J. H.; Li, W. S.

    2012-04-01

    Across the Tarim Basin, limited surface outcrops of Cryogenian to Cambrian sedimentary succession are completely exposed in the vicinity of Aksu area(Northwest Tarim), Kuruktag(Northeast Tarim)and Southwest Tarim, thus provides a unique, well preserved and accessible means by which to study the early development of the north Tarim Basin. Based on the field geological investigation in the northwestern and northeastern of Tarim Basin, with the referencing of paleomagnetism mapping and previous research, basin evolution process in Cryogenian-Cambrian is discussed according to sedimentary-tectonic event and other evidences. The major lithological types of Cryogenian-Cambrian system in Northeast Tarim are: tillite, clastic rocks(rich in organic matter) and carbonate ,with interbeds of volcanic rocks while in Northwest Tarim, the calstic rocks and carbonate are the common rock type, with tillite and volcanic interbeds in a small amount. The north margin of Tarim Block, which was a part of Rodinia supercontinent, neighboring the northwestern margin of Australia, was deeply rifted in Cryogenian-Ediacaran and developed into two rifts in the northwestern and northeastern margin, while formed a thick layer of the rift-passive margin deposits and the layer in the northwestern rift was not completely developed as the northeastern. The deepest rift-passive magin sediment which can be observed is Cryogenian-Middle Ordovician strata, and the period can be divided into Cryogenian faulted period (supercontinent rifting stage) and Ediacaran-Middle Ordovician subsidence period (plate drifting stage).

  2. Age and tectonic setting of the Mesozoic McCoy Mountains Formation in western Arizona, USA

    USGS Publications Warehouse

    Spencer, J.E.; Richard, S.M.; Gehrels, G.E.; Gleason, J.D.; Dickinson, W.R.

    2011-01-01

    The McCoy Mountains Formation consists of Upper Jurassic to Upper Cretaceous siltstone, sandstone, and conglomerate exposed in an east-west-trending belt in southwestern Arizona and southeastern California. At least three different tectonic settings have been proposed for McCoy deposition, and multiple tectonic settings are likely over the ~80 m.y. age range of deposition. U-Pb isotopic analysis of 396 zircon sand grains from at or near the top of McCoy sections in the southern Little Harquahala, Granite Wash, New Water, and southern Plomosa Mountains, all in western Arizona, identifi ed only Jurassic or older zircons. A basaltic lava fl ow near the top of the section in the New Water Mountains yielded a U-Pb zircon date of 154.4 ?? 2.1 Ma. Geochemically similar lava fl ows and sills in the Granite Wash and southern Plomosa Mountains are inferred to be approximately the same age. We interpret these new analyses to indicate that Mesozoic clastic strata in these areas are Upper Jurassic and are broadly correlative with the lowermost McCoy Mountains Formation in the Dome Rock, McCoy, and Palen Mountains farther west. Six samples of numerous Upper Jurassic basaltic sills and lava fl ows in the McCoy Mountains Formation in the Granite Wash, New Water, and southern Plomosa Mountains yielded initial ??Nd values (at t = 150 Ma) of between +4 and +6. The geochemistry and geochronology of this igneous suite, and detrital-zircon geochronology of the sandstones, support the interpretation that the lower McCoy Mountains Formation was deposited during rifting within the western extension of the Sabinas-Chihuahua-Bisbee rift belt. Abundant 190-240 Ma zircon sand grains were derived from nearby, unidentifi ed Triassic magmatic-arc rocks in areas that were unaffected by younger Jurassic magmatism. A sandstone from the upper McCoy Mountains Formation in the Dome Rock Mountains (Arizona) yielded numerous 80-108 Ma zircon grains and almost no 190-240 Ma grains, revealing a major

  3. Hydrothermal and tectonic activity in northern Yellowstone Lake, Wyoming

    USGS Publications Warehouse

    Johnson, S.Y.; Stephenson, W.J.; Morgan, L.A.; Shanks, Wayne C.; Pierce, K.L.

    2003-01-01

    Yellowstone National Park is the site of one of the world's largest calderas. The abundance of geothermal and tectonic activity in and around the caldera, including historic uplift and subsidence, makes it necessary to understand active geologic processes and their associated hazards. To that end, we here use an extensive grid of high-resolution seismic reflection profiles (???450 km) to document hydrothermal and tectonic features and deposits in northern Yellowstone Lake. Sublacustrine geothermal features in northern Yellowstone Lake include two of the largest known hydrothermal explosion craters, Mary Bay and Elliott's. Mary Bay explosion breccia is distributed uniformly around the crater, whereas Elliott's crater breccia has an asymmetric distribution and forms a distinctive, ???2-km-long, hummocky lobe on the lake floor. Hydrothermal vents and low-relief domes are abundant on the lake floor; their greatest abundance is in and near explosion craters and along linear fissures. Domed areas on the lake floor that are relatively unbreached (by vents) are considered the most likely sites of future large hydrothermal explosions. Four submerged shoreline terraces along the margins of northern Yellowstone Lake add to the Holocene record or postglacial lake-level fluctuations attributed to "heavy breathing" of the Yellowstone magma reservoir and associated geothermal system. The Lake Hotel fault cuts through northwestern Yellowstone Lake and represents part of a 25-km-long distributed extensional deformation zone. Three postglacial ruptures indicate a slip rate of ???0.27 to 0.34 mm/yr. The largest (3.0 m slip) and most recent event occurred in the past ???2100 yr. Although high heat flow in the crust limits the rupture area of this fault zone, future earthquakes of magnitude ???5.3 to 6.5 are possible. Earthquakes and hydrothermal explosions have probably triggered landslides, common features around the lake margins. Few high-resolution seismic reflection surveys have

  4. Tectonic and structural setting of the northeastern central Gulf of Suez area using aeromagnetic data

    NASA Astrophysics Data System (ADS)

    Zahra, Hesham Shaker; Nakhla, Adel Mokhles

    2016-03-01

    Cumulative qualitative and quantitative analysis of the filtered regional and residual magnetic components of the northeastern central area of the Gulf of Suez, as well as images of the second vertical derivatives of the reduced to the northern magnetic pole map of the total magnetic intensity field images, supplemented with the available geologic information, enabled the precise delineation of the detailed structural configuration of the basement complex, which consequently illustrated the structural deformational pattern of the overlying sedimentary succession. The basement tectonic map reflects a series of N-S to NNW-SSE oriented belts of high and low basement structures. These structures are interrupted by a set of NE-SW crossing diagonal faults having varying throws and creating promising blocks for exploration. An often remarkable correlation between the reduced to the magnetic pole map and the basement relief map is noted, in particular the outline of various oil fields. A larger number of the tilted fault blocks and basement culminations have been outlined and numerous interesting exploration prospects are indicated, which appear to warrant further follow up investigation.

  5. Aftershock seismicity and Tectonic Setting of the 16 September 2015 Mw 8.3 Illapel earthquake

    NASA Astrophysics Data System (ADS)

    Lange, Dietrich; Geersen, Jacob; Barrientos, Sergio; Moreno, Marcos; Grevemeyer, Ingo; Contreras-Reyes, Eduardo; Kopp, Heidrun

    2016-04-01

    Powerful subduction zone earthquakes rupture thousands of square kilometers along continental margins but at certain locations earthquake rupture terminates. On 16 September 2015 the Mw. 8.3 Illapel earthquake ruptured a 200 km long stretch of the Central Chilean subduction zone, triggering a tsunami and causing significant damage. Here we analyze the spatial pattern of coseismic rupture and the temporal and spatial pattern of local seismicity for aftershocks and foreshocks in relation to the tectonic setting in the earthquake area. Aftershock seismicity surrounds the rupture area in lateral and downdip direction. For the first 24 hours following the mainshock we observe aftershock migration to both lateral directions with velocities of approximately 2.5 and 5 km/h. At the southern earthquake boundary aftershocks cluster around individual subducted seamounts located on the prolongation of the downthrusting Juan Fernández Ridge indicating stress transfer from the main rupture area. In the northern part of the rupture area a deeper band of local seismicity is observed indicating an alternation of seismic to aseismic behavior of the plate interface in downdip direction. This aseismic region at ~30 km depth that is also observed before the Illapel 2015 earthquake is likely controlled by the intersection of the continental Moho with the subducting slab.

  6. Geomorphic signature of active tectonics in the southern Abruzzi Periadriatic hilly belt (Central Italy)

    NASA Astrophysics Data System (ADS)

    Racano, Simone; Fubelli, Giandomenico; Centamore, Ernesto; Dramis, Francesco

    2016-04-01

    The geo-structural setting of the southern Abruzzi hilly belt that stretches from the northeastern front of the Maiella Massif to the Adriatic coast is characterized by deep-seated northeast verging thrusts masked by a thick cover of Late Pliocene-Middle Pleistocene marine deposits. Most authors consider this area tectonically inactive while only few of them support the hypothesis of its recent activity from the analysis of the river network pattern. Geological and geomorphological investigations carried out in the area have clearly shown the occurrence of surface deformations resulting from the continued activity of compressive tectonics up to recent times. The analysis of the study area by of a 10 m resolution DTM (using the open-source QGIS software) confirmed and supplemented field observations. Particularly significant in this context is the topographic setting of the alluvial strath terraces in the river valleys that develop transversally to the buried thrusts. In correspondence of these structures, topographic highs have grown up displacing the middle-Pleistocene planation surface developed on top of the hilly belt, from the Maiella piedmont to the coastal zone, and diverting laterally the river courses uphill. In the same places, as along the Alento and Foro rivers that cross by antecedence the grown up topographic highs, the long profiles of terraces bend eastward and the height difference between the terrace orders, essentially related all around the area to the Quaternary regional uplift, strongly increases. In some cases, surficial faults have lowered the terraces into graben troughs or have displaced them until assuming an uphill trend. This recent tectonic activity should be taken in account in assessing the seismic hazard of the study area.

  7. Tectonic Setting of the Lyra Basin, west of the Ontong Java Plateau

    NASA Astrophysics Data System (ADS)

    Nakanishi, M.; Sano, T.; Shimizu, K.

    2007-12-01

    We present the preliminary results of the geophysical investigation and rock sampling in the Lyra Basin, the deep ocean basin west of the Ontong Java Plateau. The Ontong Java Plateau (OJP) is one of the most voluminous large igneous provinces. The evidences from drilling samples indicate that most of the OJP formed rapidly about 120 Ma at mid-southern latitude in the Pacific Basin. Deep ocean basins are contiguous with the OJP. For settlement of the argument about the origin of the OJP, the tectonic setting of the deep ocean basins around the OJP must be revealed. Tectonic histories of the Nauru, East Mariana, and Pigafetta basins, were revealed using the Mesozoic magnetic anomaly lineations. That of Lyra basin is, however, still unknown because of lack of magnetic anomaly lineations. The depth of the seafloor in the Lyra Basin deepens west, from 4000 to 5000 m. The Lyra Trough, crossing the Lyra Basin, is a broad and deep graben. In December 2006, we conducted the geophysical investigation and rock sampling in the Lyra Basin using R/V KAIREI, Japan Agency for Marine-Earth Science and Technology. Our bathymetric measurement revealed the topographic expression of the Lyra Trough. The depth of the trough is around 5500 m. The bottom of the trench as a whole is very smooth except for several lineated ridges. The height of the lineated ridges is about 500 m. The length of the lineated ridges is around 20 km. The strike of some ridges is N35°W and parallel to the trough strike. That of others is N50°W and oblique to the trough strike. Seamounts are located in the eastern rim of the Lyra Trough south of 1°30'N. The height of the seamounts is more than 2500 m. We obtained volcanic samples from the lineated ridge in the Lyra Trough and the seamount in the eastern rim of the trough. Most of igneous rocks are volcanic breccia, being coated by thick Mn crust. Although many volcanoclastic rocks are highly altered, some fresh samples were recovered. They are olivine

  8. A review of tectonics and sedimentation in a forearc setting: Hellenic Thrace Basin, North Aegean Sea and Northern Greece

    NASA Astrophysics Data System (ADS)

    Maravelis, A. G.; Boutelier, D.; Catuneanu, O.; Seymour, K. St.; Zelilidis, A.

    2016-04-01

    Exposure of the forearc region of the North Aegean Sea, Greece, offers insight into evolving convergent margins. The sedimentary fill of the Thrace Basin during the Late Eocene to Oligocene time provides a record of subduction-driven processes, such as growth of magmatic arcs and construction of accretionary complexes. This large sediment repository received sediment from two sources. The southern (outboard) basin margin reflects the active influence of the exhumed accretionary prism (e.g. Pindic Cordillera or Biga peninsula), while the northern (inboard) margin records the effect of the magmatic arc in the Rhodope region. The forearc basin sedimentary fills shoal upward into shallow-marine strata but are dominated mainly by deep-marine facies. The depositional trend and stacking pattern are dominated by progradational patterns. This trend, which is observed in both basin margins, is related to tectonic deformation rather than sea-level fluctuations. Additional evidence for this tectonic uplift comes from the backstripping analysis. The accretionary complex provided material into the forearc basin. This material was transported northeast and formed a sand-rich turbidity system that evolved upslope into shallow-marine deposits. Stratigraphic data indicate that this turbidity system exhibits a successive landward (inboard) migration of the depocenter. Provenance data utilizing sandstone petrography, conglomerate clast composition, and bulk-rock geochemistry suggest that this system reflects an increased influx of mafic material into the basin. Volcanic arc-derived material was transported south and east and accumulated in deep-marine settings. Both stratigraphic and provenance data indicate a seaward (outboard) migration of the basin depocenter and a significant increase in felsic detritus into the forearc.

  9. Tectonic stress inversion of large multi-phase fracture data sets: application of Win-Tensor to reveal the brittle tectonic history of the Lufilan Arc, DRC

    NASA Astrophysics Data System (ADS)

    Delvaux, Damien; Kipata, Louis; Sintubin, Manuel

    2013-04-01

    Large fault-slip data sets from multiphase orogenic regions present a particular challenge in paleostress reconstructions. The Lufilian Arc is an arcuate fold-and-thrust belt that formed during the late Pan-African times as the result of combined N-S and E-W amalgamation of Gondwana in SE-DRCongo and N-Zambia. We studied more than 22 sites in the Lufilian Arc, and its foreland and correlated the results obtained with existing result in the Ubende belt of W-Tanzania. Most studied sites are characterized by multiphase brittle deformation in which the observed brittle structures are the result of progressive saturation of the host rock by neoformed fractures and the reactivation of early formed fractures. They correspond to large mining exploitations with multiple large and continuous outcrops that allow obtaining datasets sufficiently large to be of statistical significance and often corresponding to several successive brittle events. In this context, the reconstruction of tectonic stress necessitates an initial field-base separation of data, completed by a dynamic separation of the original data set into subsets. In the largest sites, several parts of the deposits have been measured independently and are considered as sub-sites that are be processed separately in an initial stage. The procedure used for interactive fault-slip data separation and stress inversion will be illustrated by field examples (Luiswishi and Manono mining sites). This principle has been applied to all result in the reconstruction of the brittle tectonic history of the region, starting with two major phases of orogenic compression, followed by late orogenic extension and extensional collapse. A regional tectonic inversion during the early Mesozoic, as a result of far- field stresses mark the transition towards rift-related extension. More details in Kipata, Delvaux et al.(2013), Geologica Belgica 16/1-2: 001-017 Win-Tensor can be downloaded at: http://users.skynet.be/damien.delvaux/Tensor/tensor-index.html

  10. The geochemical fingerprint of serpentinite- and crust-dominated plate-interface settings: some tectonic implications

    NASA Astrophysics Data System (ADS)

    Cannaò, Enrico; Scambelluri, Marco; Agostini, Samuele; Tonarini, Sonia

    2014-05-01

    The interface between converging plates is made of kilometre-thick domains where slab and upper plate mantle materials are tectonically slicied within a matrix dominated either by (meta)sedimentary/crustal rocks or by serpentinite. The latter may correspond to supra-subduction mantle altered by uprising slab fluids. Once formed, these plate-interface domains act as hydrated low-viscosity layers where tectonic stress and fluid-mediated mass transfer are strongly focussed. Here we present the geochemical study of two plate-interface environments: (1) serpentinite-rich, represented by the high-pressure serpentinites of the Ligurian Alps (Erro-Tobbio and Voltri Units); (2) sediment-dominated top slab mélange, represented by de-serpentinized garnet peridotite and chlorite harzburgite bodies (hosting eclogite and metarodingite) embedded in paragneiss and micaschist from Cima di Gagnone (Adula Unit, Central Alps). The Ligurian serpentinites derive from oceanic and wedge mantle tectonically coupled and dragged to depth during Alpine subduction: they may represent the hydrated precursors of the Cima di Gagnone peridotites. The B, Pb and Sr isotopic composition of the above sets of rocks helps defining tectonic and mass transfer processes during accretion of slab and suprasubduction mantle rocks in plate-interface domains, and to retrieve the imprint of fluids from these settings, which that ultimately affect arc magmatism. The serpentinized peridotites from Erro-Tobbio (ET) show high B (10-30 ppm), delta11B (10-25 per mil), B/Nb ratio (>380) and limited enrichment in 206Pb/204Pb (18.17-18,51) and 87Sr/86Sr (0.7046- 0.7060). Scambelluri & Tonarini (2012) interpreted the B and Sr isotopic imprint of ET as representative of upper plate mantle altered by slab-fluids. The B contents (up to 30 ppm), delta11B (18-30 per mil), B/Nb ratio (>900) and 206Pb/204Pb (18.09-18.22) of the Voltri serpentinites are similar to ET. Their 87Sr/86Sr (0.7079 to 0.7105) is higher than ET. The

  11. Dynamic Digital Maps: On-line Publication of Representative "Local" Geology in a Plate Tectonic Setting

    NASA Astrophysics Data System (ADS)

    Condit, C. D.

    2002-12-01

    The use of Dynamic Digital Maps (DDMs) offers the geologic community a combination of attributes which allow the on-line publication of spatially related, highly quantitative data, to be set in a local or regional environment which lets both professional and students make inquiry based observations, and makes these data easily available for analyses. The DDM does this by displaying analytical data, images and movies from links at sample site locations on maps or images in a friendly user interface. Macintosh-only prototypes of two of these DDMs [Springerville Volcanic Field (DDM-SVF) and Tatara-San Pedro volcanic complex (DDM-TSP)] have been used in university petrology classes; the latter program has been converted to a template from which other DDMs can be made. This DDM.Template is presently being ported to a cross-platform web-enabled programming environment (MetaCard - Revolution). An example of a map produced in the process of creating this port, the DDM of New England (DDM-NE) includes six geologic field trips and the State Geologic Map of Massachusetts, and can be obtained from the URL http://ddm.geo.umass.edu. The use of these three maps allows what is essentially access to representative "local" geology in three global plate tectonic settings: a subduction zone (the Andes, DDM-TSP), a continental interior monogenetic volcanic field (DDM-SVF) and a failed rift valley (the Deerfield Basin within the DDM.NE). Because the DDM.Template provides locations for text and captions to be inserted for use at several user levels (e.g. the professional geologist, the beginning geoscientist, and the layman or perhaps middle-school student) the use of DDMs also provides a much needed outreach mechanism for the geosciences.

  12. Applications of Morphochronology to the Active Tectonics of Tibet

    SciTech Connect

    Ryerson, F J; Tapponnier, P; Finkel, R C; Meriaux, A; der Woerd, J V; Lasserre, C; Chevalier, M; Xiwei, X; Haibing, L; King, G P

    2005-01-28

    The Himalayas and the Tibetan Plateau were formed as a result of the collision of India and Asia, and provide an excellent opportunity to study the mechanical response of the continental lithosphere to tectonic stress. Geophysicists are divided in their views on the nature of this response advocating either (1) homogeneously distributed deformation with the lithosphere deforming as a fluid continuum or (2) deformation is highly localized with the lithosphere that deforms as a system of blocks. The resolution of this issue has broad implications for understanding the tectonic response of continental lithosphere in general. Homogeneous deformation is supported by relatively low decadal, geodetic slip-rate estimates for the Altyn Tagh and Karakorum Faults. Localized deformation is supported by high millennial, geomorphic slip-rates constrained by both cosmogenic and radiocarbon dating on these faults. Based upon the agreement of rates determined by radiocarbon and cosmogenic dating, the overall linearity of offset versus age correlations, and on the plateau-wide correlation of landscape evolution and climate history, the disparity between geomorphic and geodetic slip-rate determinations is unlikely to be due to the effects of surface erosion on the cosmogenic age determinations. Similarly, based upon the consistency of slip-rates over various observation intervals, secular variations in slip-rate appear to persist no longer than 2000 years and are unlikely to provide reconciliation. Conversely, geodetic and geomorphic slip-rate estimates on the Kunlun fault, which does not have significant splays or associated thrust faults, are in good agreement, indicating that there is no fundamental reason why these complementary geodetic and geomorphic methods should disagree. Similarly, the geodetic and geomorphic estimates of shortening rates across the northeastern edge of the plateau are in reasonable agreement, and the geomorphic rates on individual thrust faults demonstrate

  13. Three sets of fine extinction bands in a tectonically deformed vein-quartz single crystal

    NASA Astrophysics Data System (ADS)

    Derez, Tine; Van der Donck, Tom; Pennock, Gill; Drury, Martyn; Sintubin, Manuel

    2014-05-01

    Intracrystalline fine extinction bands (FEBs) in quartz, are narrow (less than 5µm thick), planar microstructures with a misorientation up to 5° with respect to the host crystal, occurring in closely spaced sets (spacing of 4-5μm). FEBs have been commonly attributed to a large range of brittle and/or crystal-plastic mechanisms, revealing considerable disagreement on the responsible crystal-plastic slip systems and the ambient conditions. Another question that arises, is whether or not the FEBs rotate from a basal plane orientation to orientations ranging between the basal and prism planes. Usually only one set of FEBs occurs in a single crystal, though two sets are observed, in particular with increasing strain. Tentatively, a maximum of two sets of sub-basal FEBs has been postulated to develop in a single quartz crystal in a tectonic context. However, we identified several crystals in naturally deformed vein-quartz containing three sets of FEBs. The vein-quartz has been deformed under sub-greenschist metamorphic conditions, during the late Palaeozoic Variscan orogeny, in the High-Ardenne slate belt (Belgium). The vein-quartz has been subjected to bulging dynamic recrystallisation and shows a high degree of undulatory extinction, abundant subgrains and wide extinction bands sub-parallel to the c-axis. We attempted to characterise these three sets of FEBs by means of light microscopy, EBSD-OIM and universal stage microscopy. In both cases studied the c-axis is inclined less than 8° with respect to the thin-section plane. The different sets of FEBs show a consistent orientation with respect to the c-axis. One set of FEBs deviates maximum 10° from the basal plane. The other two sets deviate between 15 and 35° from a basal plane orientation. Corresponding FEBs, at the same angle with respect to the c-axis, have similar morphologies. In relative EBSD orientation maps FEBs show a maximum misorientation of 3°, and have a lower pattern quality than the host crystal

  14. Structural setting and tectonic evolution of the Apennine Units of northern Calabria

    NASA Astrophysics Data System (ADS)

    Iannace, Alessandro; Bonardi, Glauco; D'Errico, Marco; Mazzoli, Stefano; Perrone, Vincenzo; Vitale, Stefano

    2005-12-01

    A new structural-stratigraphic synthesis of the Apennine units of northern Calabria is presented. The Meso-Cenozoic successions are grouped into two tectonic units, named Pollino-Ciagola Unit (PCU) and Lungro-Verbicaro Unit (LVU), comprising terrains formerly attributed to five different tectonic units. Fe sbnd Mg carpholite and blue amphibole record HP-LT metamorphism in the LVU, followed by progressive decompression leading to final greenschist facies re-equilibration during dominantly extensional deformation. Final tectonic emplacement of the LVU over the PCU post-dated the metamorphism of the LVU and was accompanied by intense ductile deformation along zones of strain localisation in footwall rocks. All of the units were later affected by folding and minor thrusting during subsequent Apennine tectonics. To cite this article: A. Iannace et al., C. R. Geoscience 337 (2005).

  15. Formation and tectonic evolution of the Cretaceous Jurassic Muslim Bagh ophiolitic complex, Pakistan: Implications for the composite tectonic setting of ophiolites

    NASA Astrophysics Data System (ADS)

    Khan, Mehrab; Kerr, Andrew C.; Mahmood, Khalid

    2007-10-01

    The Muslim Bagh ophiolitic complex Balochistan, Pakistan is comprised of an upper and lower nappe and represents one of a number of ophiolites in this region which mark the boundary between the Indian and Eurasian plates. These ophiolites were obducted onto the Indian continental margin around the Late Cretaceous, prior to the main collision between the Indian and Eurasian plates. The upper nappe contains mantle sequence rocks with numerous isolated gabbro plutons which we show are fed by dolerite dykes. Each pluton has a transitional dunite-rich zone at its base, and new geochemical data suggest a similar mantle source region for both the plutons and dykes. In contrast, the lower nappe consists of pillow basalts, deep-marine sediments and a mélange of ophiolitic rocks. The rocks of the upper nappe have a geochemical signature consistent with formation in an island arc environment whereas the basalts of the lower nappe contain no subduction component and are most likely to have formed at a mid-ocean ridge. The basalts and sediments of the lower nappe have been intruded by oceanic alkaline igneous rocks during the northward drift of the Indian plate. The two nappes of the Muslim Bagh ophiolitic complex are thus distinctively different in terms of their age, lithology and tectonic setting. The recognition of composite ophiolites such as this has an important bearing on the identification and interpretation of ophiolites where the plate tectonic setting is less well resolved.

  16. Topographyc metrics in the southern sector of the Marche foothills: implication for active tectonic analysis

    NASA Astrophysics Data System (ADS)

    Materazzi, Marco; Aringoli, Domenico; Carducci, Tamara; Cavitolo, Paolo; Farabollini, Piero; Giacopetti, Marco; Pambianchi, Gilberto; Tondi, Emanuele; Troiani, Francesco

    2016-04-01

    Quantitative geomorphic analysis can be provided a useful contribution to the study of recent tectonics. Some parameters, that quantify the channels morphology, as the Stream Length-Gradient (SL) Index (Hack, 1973) and the Steepness (Ks) Index (Flint, 1974), are generally used to detect anomalies on the expected concave-up equilibrium stream-profile, which can result in local abrupt changes in stream gradient (i.e., knickpoints) and/or broad convexities on stream long-profiles extending for tens of kilometres (i.e., knickzones). The main goal of this work is the study of the morphological and morphometrical features in the southern sector of the Marche Region, with the aim to gain new knowledge on the influences of rock resistance and rock uplift on the fluvial and topographic system. The investigated area is situated in central Italy and it extends from the axial zone of the Umbria-Marche Apennines to the Adriatic Sea, including the southern sector of the Marche Region and belongs to the foredeep domain of the Apennines orogenic system, which has affected by tectonic activity up to very recent times. The rheology of outcropping deposits doesn't allow the strain to be easily recorded at the outcrop scale. The analyses have been aimed at to test the sensitivity of both SL and Ks for evaluating active crustal deformations, acting at different wavelengths on land surface, within a low tectonically active thrust-and-fold belt. Additional purpose was the understanding of the pattern of regional differential crustal activity in the topographic arrangement of the study area In this research project two sets of analysis were conducted. References Hack J.T. 1973. Stream-profile analysis and stream-gradient index. Journal of Research of the U.S. Geological Survey, 1, 421-429. Flint J.J. 1974. Stream gradient as a function of order, magnitude and discharge. Water Resources Research, 10, 969-973.

  17. Structural control of geothermal reservoirs in extensional tectonic settings: An example from the Upper Rhine Graben

    NASA Astrophysics Data System (ADS)

    Meixner, Jörg; Schill, Eva; Grimmer, Jens C.; Gaucher, Emmanuel; Kohl, Thomas; Klingler, Philip

    2016-01-01

    In extensional tectonic settings major structural elements such as graben boundary faults are typically oriented subparallel to the maximum horizontal stress component SHmax. They are often structurally accompanied by transfer zones that trend subparallel to the extension direction. In the Upper Rhine Graben, such transfer faults are typically characterized by strike-slip or oblique-slip kinematics. A major re-orientation of the regional stress field by up to 90° of the Upper Rhine Graben in the Early Miocene led to the present-day normal and strike-slip faulting regimes in the North and South of the Upper Rhine Graben, respectively, and a transition zone in-between. Consequently, conditions for fault frictional failure changed significantly. Moreover, it has been observed during tracer and stimulation experiments that such transfer faults may be of major importance for the hydraulic field of geothermal reservoirs under the present stress condition, especially, when located between production and injection well. In this context we have investigated slip and dilation tendencies (TS and TD) of major structural elements at reservoir scale for two representative geothermal sites, Bruchsal (Germany) and Riehen (Switzerland), located close to the Eastern Main Boundary Fault of the Upper Rhine Graben. We have evaluated the quality and uncertainty range of both tendencies with respect to potential variation in SHmax orientation. Despite significant differences in orientation of the structures and the stress regimes, the resulting variation of TS and TD reveal major similarities concerning the reactivation potential of both, the graben-parallel structures and the transfer faults. The conditions of criticality for tensile failure and non-criticality for shear failure suggest that transfer faults are most likely naturally permeable structures with low stimulation potential. This is in agreement with the absence of both immediate tracer recovery and seismicity in the studied

  18. The tectonic setting of the Seychelles, Mascarene and Amirante Plateaus in the Western Equatorial Indian Ocean

    NASA Technical Reports Server (NTRS)

    Mart, Y.

    1988-01-01

    A system of marine plateaus occurs in the western equatorial Indian Ocean, forming an arcuate series of wide and shallow banks with small islands in places. The oceanic basins that surround the Seychelles - Amirante region are of various ages and reflect a complex seafloor spreading pattern. The structural analysis of the Seychelle - Amirante - Mascarene region reflects the tectonic evolution of the western equatorial Indian Ocean. It is suggested that due to the seafloor spreading during a tectonic stage, the Seychelles continental block drifted southwestwards to collide with the oceanic crust of the Mascarene Basin, forming an elongated folded structure at first, and then a subduction zone. The morphological similarity, the lithological variability and the different origin of the Seychelles Bank, the Mascarene Plateau and the Amirante Arc emphasizes the significant convergent effects of various plate tectonic processes on the development of marine plateaus.

  19. Emeralds in the Eastern Cordillera of Colombia: Two tectonic settings for one mineralization

    NASA Astrophysics Data System (ADS)

    Branquet, Yannick; Laumonier, Bernard; Cheilletz, Alain; Giuliani, Gaston

    1999-07-01

    Colombian emeralds are formed through a hydrothermal-sedimentary process. On the western side of the Eastern Cordillera, the deposits are linked by tear faults and associated thrusts developed during a compressive tectonic phase that occurred at the time of the Eocene-Oligocene boundary, prior to the major uplift of the Cordillera during the Andean phase (middle Miocene). On the eastern side of the Cordillera, emerald mineralization occurred earlier, at the time of the Cretaceous-Tertiary boundary, during a thin-skinned extensional tectonic event linked to evaporite dissolution. This event predates the Andean phase, during which this part of the chain was folded and thrust over the Llanos foreland.

  20. Mapping Active Faults and Tectonic Geomorphology offshore central California

    NASA Astrophysics Data System (ADS)

    Johnson, S. Y.; Watt, J. T.; Hart, P. E.; Sliter, R. W.; Wong, F. L.

    2009-12-01

    In June 2008, and July 2009, the USGS conducted two high-resolution, marine, seismic-reflection surveys across the continental shelf and upper slope between Piedras Blancas and Point Sal, central California, in order to better characterize regional earthquake sources. More than 1,300 km of single-channel seismic data were acquired aboard the USGS R/V Parke Snavely using a 500-joule mini-sparker source fired at a 0.5-second shot interval and recorded with a 15-meter streamer. Most tracklines were run perpendicular to the coast at 800-meter spacing, extending from the nearshore (~ 10-15 m water depth) to as far as 20 km offshore. Sub-bottom imaging varies with substrate, ranging from outstanding (100 to 150 m of penetration) in inferred Quaternary shallow marine, shelf and upper slope deposits to poor (0 to 10 m) in the Mesozoic basement rocks. Marine magnetic data were collected simultaneously on this survey, and both data sets are being integrated with new aeromagnetic data, publicly available industry seismic-reflection data, onshore geology, seismicity, and high-resolution bathymetry. Goals of the study are to map geology, structure, and sediment distribution; to document fault location, length, segmentation, shallow geometry and structure; and to identify possible sampling targets for constraining fault slip rates, earthquake recurrence, and tsunami hazard potential. The structure and tectonic geomorphology of the >100-km-long, right-lateral, Hosgri fault zone and its connections to the Los Osos, Pecho, Oceano and other northwest-trending inboard faults are the focus of this ongoing work. The Hosgri fault forms the eastern margin of the offshore Santa Maria basin and coincides in places with the outer edge of the narrow (5- to 15-km-wide), structurally complex continental shelf. The Hosgri is imaged as a relatively continuous, vertical fault zone that extends upward to the seafloor; varies significantly and rapidly along strike; and incorporates numerous

  1. Threshold bedrock channels in tectonically active mountains with frequent mass wasting

    NASA Astrophysics Data System (ADS)

    Korup, O.; Hayakawa, Y. S.; Codilean, A.; Oguchi, T.

    2013-12-01

    Models of how mountain belts grow and erode through time largely rely on the paradigm of fluvial bedrock incision as the main motor of response to differences in rock uplift, thus setting base levels of erosion in tectonically active landscapes. Dynamic feedbacks between rock uplift, bedrock river geometry, and mass wasting have been encapsulated within the concept of threshold hillslopes that attain a mechanically critical inclination capable of adjusting to fluvial incision rates via decreased stability and commensurately more frequent landsliding. Here we provide data that challenge the widely held view that channel steepness records tectonic forcing more faithfully than hillslope inclination despite much robust empirical evidence of such links between bedrock-river geometry and hillslope mass wasting. We show that the volume mobilized by mass wasting depends more on local topographic relief and the sinuosity of bedrock rivers than their mean normalized channel steepness. We derive this counterintuitive observation from an unprecedented inventory of ~300,000 landslides covering the tectonically active Japanese archipelago with substantial differences in seismicity, lithology, vertical surface deformation, topography, and precipitation variability. Both total landslide number and volumes increase nonlinearly with mean local relief even in areas where the fraction of steepest channel segments attains a constant threshold well below the maximum topographic relief. Our data document for the first time that mass wasting increases systematically with preferential steepening of flatter channel segments. Yet concomitant changes in mean channel steepness are negligible such that it remains a largely insensitive predictor of landslide denudation. Further, minute increases in bedrock-river sinuosity lead to substantial reduction in landslide abundance and volumes. Our results underline that sinuosity (together with mean local relief) is a key morphometric variable for

  2. The ages and tectonic setting of the Faja Eruptiva de la Puna Oriental, Ordovician, NW Argentina

    NASA Astrophysics Data System (ADS)

    Bahlburg, Heinrich; Berndt, Jasper; Gerdes, Axel

    2016-07-01

    The Ordovician Faja Eruptiva de la Puna Oriental is a magmatic, predominantly intrusive belt in the Puna of northwestern Argentina with a N-S extension of ca. 400 km. Scarce isotope geochemical ages and biostratigraphic data on some of the folded Faja Eruptiva country rocks assign the magmatism either to the Lower and lower Middle Ordovician, or to the latest Ordovician. Interpretations of origin and tectonic framework of the Faja Eruptiva are controversial and vary between arc, back-arc and collisional-orogenic settings. We present high-resolution La-ICP-MS U-Pb age and Hf isotope data on zircons from 10 plutonic samples covering the magmatic belt along a length of 200 km in the northern Argentinian Puna. The xenocrystic and magmatic zircon age data have a wide spread between 2700 Ma and 440 Ma. Concordia and weighted mean age data document protracted magmatism in two phases between 480 and 460 Ma, and between 453 and 444 Ma, and constrain the time of the last intrusions at 444 ± 3 Ma and at 445 ± 2 Ma thus defining this last and main phase of intrusion at 444 Ma. εHf(t) values define a main vertical trend centered at 500 Ma with εHf(t) values between + 3 and - 16 indicating significant mixing of juvenile early Paleozoic melts with Paleoproterozoic crustal components. A second trend is formed by zircons with ages between 1.1 Ga and c. 500 Ma and predominantly positive εHf values between + 8 and - 3 and originates in juvenile mantle compositions between 1.6 and 1.1 Ga. The spread of the zircon and Hf data document that the Faja Eruptiva intrusives have experienced large-scale contamination by the hosting crustal basement. It follows that the basement of the Puna is formed either by the upper Proterozoic-lower Cambrian Puncoviscana Formation as an erosional product of the Proterozoic orogenic belts of SW Amazonia or that the Puna including its Puncoviscana basement is underlain by a crust shaped by these orogenies. The main intrusive event at 444 Ma has been

  3. Tectonic setting of Cretaceous basins on the NE Tibetan Plateau: Insights from the Jungong basin

    USGS Publications Warehouse

    Craddock, W.H.; Kirby, E.; Dewen, Z.; Jianhui, L.

    2012-01-01

    Quantifying the Cenozoic growth of high topography in the Indo-Asian collision zone remains challenging, due in part to significant shortening that occurred within Eurasia before collision. A growing body of evidence suggests that regions far removed from the suture zone experienced deformation before and during the early phases of Himalayan orogenesis. In the present-day north-eastern Tibetan Plateau, widespread deposits of Cretaceous sediment attest to significant basin formation; however, the tectonic setting of these basins remains enigmatic. We present a study of a regionally extensive network of sedimentary basins that are spatially associated with a system of SE-vergent thrust faults and are now exposed in the high ranges of the north-eastern corner of the Tibetan Plateau. We focus on a particularly well-exposed basin, located ~20km north of the Kunlun fault in the Anyemaqen Shan. The basin is filled by ~900m of alluvial sediments that become finer-grained away from the basin-bounding fault. Additionally, beds in the proximal footwall of the basin-bounding fault exhibit progressive, up-section shallowing and several intraformational unconformities which can be traced into correlative conformities in the distal part of the basin. The observations show sediment accumulated in the basin during fault motion. Regional constraints on the timing of sediment deposition are provided by both fossil assemblages from the Early Cretaceous, and by K-Ar dating of volcanic rocks that floor and cross-cut sedimentary fill. We argue that during the Cretaceous, the interior NE Tibetan Plateau experienced NW-SE contractional deformation similar to that documented throughout the Qinling-Dabie orogen to the east. The Songpan-Ganzi terrane apparently marked the southern limit of this deformation, such that it may have been a relatively rigid block in the Tibetan lithosphere, separating regions experiencing deformation north of the convergent Tethyan margin from regions deforming

  4. Delivery of volatiles to terrestrial planets during accretion: Setting the stage for plate tectonics

    NASA Astrophysics Data System (ADS)

    Elkins-Tanton, L.; Tikoo, S.

    2012-04-01

    A persistent problem in planetary science is how and when plate tectonics can begin in planetary evolution. On Earth, plate tectonics is thought to be facilitated by the low-viscosity asthenosphere, which obtains its low viscosity partly through low pressure, and partly through a water content on the order of hundreds of parts per million, likely trapped in the crystal structure of nominally anhydrous silicate minerals. Subduction zones introduce water contents of that magnitude to the mantle that circulates above the sinking oceanic plate, and subduction zones are sometimes cited as the process that hydrates an originally dry planetary interior. Thus there is a chicken-and-egg problem: If a damp asthenosphere is needed for plate tectonics, but plate tectonics itself creates the damp asthenosphere, how does the process initiate? Despite the existence of a metallic (reduced) core, both the compositions of meteorites and the certainty of radial mixing during accretion suggest that the Earth and other rocky planets accreted with some non-zero water content. Tracking water partitioning between magma ocean fluids and solidifying mantle minerals suggests that the planetary interior could begin with a non-zero water content. Here we present models for the interior water content of the Earth following accretion, and hypothesize about a dynamic processes that may have sped the development of plate tectonics. On an Earth-sized planet a magma ocean would solidify to produce very dense near-surface solids that also contain the bulk of the water held in the solid state, and the bulk of the incompatible elements. During gravitationally-driven overturn shallow, dense, damp solids carry their water as they sink into the perovskite stability zone and transform the bulk of their mineralogy into perovskite. The last solids that form near the surface exceed the likely water saturation levels of perovskite and will be forced to dewater as they cross the boundary into the lower mantle

  5. Stratigraphy, geochronology, geochemistry and tectonic setting of the Mesozoic Nazas Formation, north-central Mexico

    NASA Astrophysics Data System (ADS)

    Bartolini, Claudio

    Late Triassic to Middle Jurassic volcanic-sedimentary sequences that were part of the Mesozoic continental-margin of western North America are exposed in northern and central Mexico. These sequences have been grouped into the Nazas Formation and crop out in the states of Durango, Coahuila, Zacatecas, and San Luis Potosi. The Nazas Formation consists of 2,500 m or more of volcanic and pyroclastic rocks and interbedded clastic sedimentary rocks that were deposited in alluvial fan and fluvial depositional systems that developed in intra-arc basins, mainly fault-bound grabens and topographic depressions within an extending Mesozoic volcanic arc. Major and trace element geochemistry of volcanic rocks suggests that the volcanic suite is calc-alkaline and includes rhyolite, dacite, rhyodacite, andesite, trachyandesite and rare basalt. Pyroclastic rocks are basically air-fall tuffs and volcanic breccias. The sedimentary strata include conglomerate, sandstone, shale, and siltstone, locally red in color. Geochronology (Ar-Ar, K-Ar and Rb-Sr) and field evidence indicate that the age of the Nazas Formation ranges from Late Triassic to Middle Jurassic, but the peak of arc volcanism appears to be Early and Middle Jurassic. The Mesozoic magmatic arc in Mexico has a northwest trend and extends from Sonora to Chiapas. The arc structure is more than 2,000 km long, and possibly up to 150 km wide. The width of the arc is uncertain due to the limited number of surface outcrops, however, it did not extend east into the Gulf of Mexico. Arc-related magmatism began in latest Triassic time, but the peak of arc evolution occurred during the Early and Middle Jurassic. By Oxfordian time, the arc was deeply dissected and eroded, and magmatic activity had ceased. A marine transgression from the Gulf of Mexico covered most of the Nazas arc, depositing the initial sediments of the Oxfordian Zuloaga Limestone in the Mexican Geosyncline. Jurassic crustal extension in the Gulf of Mexico was

  6. Archaeological evidences of the tectonic activity of Shueib Structure (NW Jordan)

    NASA Astrophysics Data System (ADS)

    Al-Awabdeh, Mohammad; Azañón, J. Miguel; Pérez-Peña, J. Vicente; Booth-Rea, Gillermo

    2014-05-01

    Archaeological damage in buried ruins often offers an excellent record of recent tectonic activity. The lower Jordan valley has experienced a continuous occupation in the last 5000 year, being frequent archaeological remains of human settlements along the valley. In this work we studied the Early Neolithic-to-Middle Islamic Periods archaeological site of Tall al-Hammam (Arabic name, ¨Hill of Baths¨). This ruin is located 27 km southwest of Amman city and it constitutes the largest Bronze Age archaeological site in Jordan. It consists of two main parts; the Upper Tall and the Lower Tall. This ruin lies within the southwestern termination of the Shueib structure (SHS); a Cretaceous fold-bend fault structure thought inactive through the entire Cenozoic. The relics, in the lower Tall, show clear fault-related damage in some walls. Two Middle Bronze Age (MBA) walls are displaced 26 and 20 cm respectively, according with a NNE-SSW fault plane. Apart of wall displacements, hundreds of joints and cracks in boulders of the walls are present. They strike generally NW-SE and NE-SW. Both archaeological evidences, boulder fractures and walls distortion, are coherent with the present-day tectonic setting of the Dead Sea Transform Fault in the region, and suggest a Quaternary reactivation of the SHS.

  7. Drainage response to active tectonics and evolution of tectonic geomorphology across the Himalayan Frontal Thrust, Kumaun Himalaya

    NASA Astrophysics Data System (ADS)

    Luirei, Khayingshing; Bhakuni, Surendra S.; Kothyari, Girish Ch.

    2015-06-01

    We present the results of integrated studies of geomorphic indices of drainage networks and landforms developed across the mountain front along the Himalayan Frontal Thrust (HFT) between the Dabka and Baur rivers, Kumaun Himalaya. The HFT is a morphogenic structure in nature, creating a 100-m-high E-W trending escarpment that extends ~ 21 km. Geomorphological evidence indicates ~ 10.5 km westward migration of the Dabka River and ~ 5.2 km eastward migration of the Baur River. These migrations are a result of uplift of the hanging wall along the HFT. The HFT is offset by a transverse fault, which suggests that the latter postdates the reactivation of the HFT between 500 and 100 ka. Presence of different levels of strath terraces along the mountain front suggests the active nature of the HFT. To assess the relative tectonic activity, morphometric indices such as stream-gradient (SL) index, mountain front sinuosity (Smf) index, and ratio of valley floor width to valley height (Vf) have been analyzed. Results of the former two are consistent with the tectonic landforms developed in thrust zones. Paleochannels of the Dabka and Baur rivers are characterized by high Vf values while other valleys show low Vf values. Quaternary alluvial sediments have been deformed along the Pawalgarth Thrust, a splay of the HFT. Deformation has resulted in the formation of the Pawalgarh Anticline, a thrust-related asymmetric fold.

  8. Significant Centers of Tectonic Activity as Identified by Wrinkle Ridges for the Western Hemisphere of Mars

    NASA Technical Reports Server (NTRS)

    Anderson, R.C.; Haldemann, A. F. C.; Golombek, M. P.; Franklin, B. J.; Dohm, J. M.; Lias, J.

    2000-01-01

    The western hemisphere region of Mars has been the site of numerous scientific investigations regarding its tectonic evolution. For this region of Mars, the dominant tectonic region is the Tharsis province. Tharsis is characterized by an enormous system of radiating grabens and a circumferential system of wrinkle ridges. Past investigations of grabens associated with Tharsis have identified specific centers of tectonic activity. A recent structural analysis of the western hemisphere region of Mars which includes the Tharsis region, utilized 25,000 structures to determine the history of local and regional centers of tectonic activity based primarily on the spatial and temporal relationships of extensional features. This investigation revealed that Tharsis is more structurally complex (heterogeneous) than has been previously identified: it consists of numerous regional and local centers of tectonic activity (some are more dominant and/or more long lived than others). Here we use the same approach as Anderson et al. to determine whether the centers of tectonic activity that formed the extensional features also contributed to wrinkle ridge (compressional) formation.

  9. Geodetic component of the monitoring of tectonic and hydrogeological activities in Kopacki Rit Nature Park

    NASA Astrophysics Data System (ADS)

    Dapo, Almin; Pribicevic, Bosko

    2013-04-01

    Based on the European and global experience, the amplitude change in the structural arrangement caused by recent tectonic movements, can be most accurately determined by repeated precise GPS measurements on specially stabilized geodetic and geodynamic points. Because of these reasons, the GPS method to determine the movements on specially stabilized points in the Nature park Kopacki rit is also applied in this project. Kopacki rit Nature Park is the biggest preserved natural flooded area on the Danube. It is spread over 23 000 hectares between the rivers Danube and Drava and is one of the biggest fluvial wetland valleys in Europe. In 1993 it was listed as one of internationally valuable wetlands according to the Ramsar Convention. By now in Kopacki rit there have been sights of about 295 bird species, more than 400 species of invertebrates and 44 types of fish. Many of them are globally endangered species like, white tailed eagle, black stork and prairie hawk. It's not rare to come across some deer herds, wild boars or others. Today's geological and geomorphological relations in the Nature park Kopacki rit are largely the result of climate, sedimentary, tectonic and anthropogenic activity in the last 10,000 years. Unfortunately the phenomenon of the Kopacki rit Nature park is in danger to be over in the near future due to those and of course man made activities on the Danube river. It is trough scientific investigations of tectonic and hydrogeological activities that scientist from University of Zagreb are trying to contribute to wider knowledge and possible solutions to this problem. In the year 2009 the first GPS campaign was conducted, and the first set of coordinates of stabilized points was determined which can be considered zero-series measurements. In 2010 a second GPS campaign was conducted and the first set of movements on the Geodynamic Network of Kopacki Rit Nature Park was determined. Processing GPS measurements from 2009 and 2010 was carried out in a

  10. Geochemistry of Neogene sedimentary rocks from Borneo Basin, Malaysia: implications on paleo-weathering, provenance and tectonic setting

    NASA Astrophysics Data System (ADS)

    Ramasmay, N.; Roy, P.; MP, J.; Rufino, L.; Franz, L. K.; Viswanathan, P. M.

    2013-05-01

    Multi-element geochemistry and mineralogy are used to characterize the chemical composition, degree of paleo-weathering, provenance and tectonic settingsof the Neogene sedimentary rocks of Borneo Basin from east Malaysia. The sedimentary rocks are classified as extremely weathered sandstones (i.e. wacke, arkose, litharenite, Fe-sandstone and quartz arenite). Higher values of both weathering indices of alteration (i.e. CIA>83 and PIA>89) suggest that the sandstones have undergone extreme chemical weathering. Absence of any feldspar in the mineralogical analysis indicates its degradation during the weathering. Except for the quartz arenite, all other sandstones are characterized by post-depositional K-metasomatism and zircon enrichment through sediment recycling. The geochemical characteristics suggest a mixed-nature provenance for the sandstones with contribution coming from both felsic and mafic igneous rocks. Enriched Cr in quartz arenite and Fe-sandstone are related to contribution from ophiolite or fractionation of Cr-bearing minerals. The inferred tectonic settings are variable and suggest a complex nature of tectonic environment in the basin.

  11. Active landsliding and landscape denudation in response to transient tectonic uplift, Northern California.

    NASA Astrophysics Data System (ADS)

    Bennett, G. L.; Roering, J. J.; Miller, S. R.; Kirby, E.; Schmidt, D. A.

    2014-12-01

    The northern Californian Coast ranges present a unique area to study landscape response to transient tectonic uplift. Studies have shown that an increase in uplift may be balanced by the rate of landsliding in settings of steady uplift. However, the landsliding response to transient tectonic uplift remains to be elucidated. The Californian Coast ranges are shaped by the northward migration of the Mendocino Triple Junction (MTJ), which geodynamic modeling suggests produces a transient double-humped uplift field. A major research question is whether we can detect a signature of this transient tectonic uplift in landslide activity and document how the channel network communicates this signal to hillslopes. Using air photos and Worldview imagery, we manually mapped more than 2000 earthflows and debris slides in the Eel and surrounding catchments that span the ~400 km-long region. The velocities of active earthflows were estimated by visually tracking features between images spanning 1993 to 2013. We mapped channel steepness from 10m NED DEMs in Topotoolbox 2 and developed a new tool to automatically define knickpoints along the channel network. Earthflows occur almost exclusively in a band of Franciscan mélange oriented along the MTJ transect whilst debris slides are more evenly distributed by lithology. Both earthflows and debris slides are clustered in the Eel catchment around the proposed uplift peaks and are largely absent outside of these zones. Within these areas of high landslide densities, we observe peaks in active earthflows adjacent to peaks in dormant earthflows to the south, suggesting that the signature of earthflow activity remains for a period of time once the uplift peak has passed. Landslide density, mean landslide area, and earthflow velocity all increase rapidly above threshold values of channel steepness and local relief. In the Eel catchment, where the zone of rapid uplift is commencing, landslides, particularly earth flows, are concentrated

  12. Application of multi-dimensional discrimination diagrams and probability calculations to Paleoproterozoic acid rocks from Brazilian cratons and provinces to infer tectonic settings

    NASA Astrophysics Data System (ADS)

    Verma, Sanjeet K.; Oliveira, Elson P.

    2013-08-01

    studies on Cassiterita-Tabuões, Ritápolis, São Tiago-Rezende Costa (south of São Francisco craton, Minas Gerais) showed a collision setting, which agrees fairly reasonably with a syn-collision tectonic setting indicated in the literature. A within-plate setting is suggested for the Serrinha magmatic suite, Mineiro belt (south of São Francisco craton, Minas Gerais), contrasting markedly with the arc setting suggested in the literature. The ninth case study on Rio Itapicuru granites and Rio Capim dacites (north of São Francisco craton, Serrinha block, Bahia) showed a continental arc setting. The tenth case study indicated within-plate setting for Rio dos Remédios volcanic rocks (São Francisco craton, Bahia), which is compatible with these rocks being the initial, rift-related igneous activity associated with the Chapada Diamantina cratonic cover. The eleventh, twelfth and thirteenth case studies on Bom Jesus-Areal granites, Rio Diamante-Rosilha dacite-rhyolite and Timbozal-Cantão granites (São Luís craton) showed continental arc, within-plate and collision settings, respectively. Finally, the last two case studies, fourteenth and fifteenth showed a collision setting for Caicó Complex and continental arc setting for Algodões (Borborema province).

  13. Modern Tectonic Deformation in the Active Basin-And Province Northwest of Beijing, China

    NASA Astrophysics Data System (ADS)

    Mi, S.; Wen, X.

    2012-12-01

    Our study region is the northwest of Beijing, northern north China. The most typical extensional active tectonic area of the China continent, called the active basin-and-range province northwest of Beijing, exist there. This active tectonic province is made up of several NE-trending Quaternary graben basins and horst ranges between basins. An about 1500-year-long written historical record has suggested that there have been no major earthquakes with magnitude 7 or greater occurred in most of the study region since AD 512. So, the characteristic of modern tectonic deformation of the study region and its implication for the future seismic potential of major earthquakes are important scientific issues. In this study, based on data of regional GPS station velocities and active tectonics, combining relocated earthquake distribution, we make a preliminary analysis on the characteristic of the modern tectonic deformation of the study region. We design three zones across deferent segments of the active basin-and-range province to analyze both the present tectonic deformation from the GPS velocity profiles and the major fault's downward-extents from the relocated hypocenters. Our analyses reveal that: (1) Significant NNW-ward and SSE-ward horizontal extension exists on different segments of the active basin-and-range province northwest of Beijing at rates of 2 to 3mm /yr, accompanied with right-lateral shear deformation at 1 to 2mm/yr. (2) On the present tectonic deformation, the southeastern margin of the Datong-Yangyuan basin, the biggest graben basin of the active tectonic province, shows as a turning belt of the extensional rates, suggesting that relatively high tensile strain accumulation could exist there. (3)On the northeastern segment of the studied active basin-and-range province, both the Zhangjiakou-Yanhui graben basin and the Beijing graben basin have also been being in significant extensional and shear deformation. (4) The relocated hypocenter distribution have

  14. The Riviere des Plante ophiolitic Melange; tectonic setting and melange formation in the Quebec Appalachians

    SciTech Connect

    Cousineau, P.A. )

    1991-01-01

    The Riviere des Plante ophiolitic Melange (RPOM) is the largest and best exposed of the three known ophiolitic melanges that contain blocks of Chain Lakes Massif (CLM). All three lie along the Baie Verte-Brompton line, which marks the suture between the continental rocks of the Humber zone and the oceanic rocks of the Dunnage zone. The ophiolitic melange is composed of: serpentinized ultramafic rocks, some of which are sheared and/or carbonatized; blocks of amphibolitized gabbro; basalt; volcanogenic breccia; and conglomerates. It also contains continental K-rich granitoid rocks and high-grade metamorphic (upper amphibolite facies) rocks. The RPOM is part of the Saint-Daniel Melange, an accretionary prism onto which the RPOM has been tectonically emplaced. The CLM was part of a terrane accreted to the Laurentian margin during the Taconian orogeny. Blocks of the CLM along the Baie Verte-Brompton line are interpreted as fragments of this terrane caught within the suture zone. It is proposed that the CLM could be the equivalent of Grenville-derived greywacke originally laid down during the phase of continental rifting that led to the formation of the Iapetus Ocean and was later tectonized and metamorphosed during the Taconian and Acadian orogenies. The RPOM would represent the relic of a serpentinite diapir that rose within a deep oceanic fault. The presence of continental rocks like the CLM suggest that a continental magmatic arc was put in contact with an oceanic crust along this fault.

  15. The Geomorphological Evolution of a Landscape in a Tectonically Active Region: the Sennwald Landslide

    NASA Astrophysics Data System (ADS)

    Aksay, Selçuk; Ivy-Ochs, Susan; Hippe, Kristina; Graemiger, Lorenz; Vockenhuber, Christof

    2016-04-01

    The Säntis nappe is a fold-and-thrust structure in eastern Switzerland consisting of numerous tectonic discontinuities that make rocks vulnerable to rock failure. The Sennwald landslide is one of those events that occurred due to the failure of Lower Cretaceous Helvetic limestones. This study reveals the surface exposure age of the event in relation to geological and tectonic setting, earthquake frequency of the Central Alps, and regional scale climate/weather influence. Our study comprises detailed mapping of landform features, thin section analysis of landslide boulder lithologies, landslide volume estimation, numerical DAN-3D run-out modelling, and the spatial and temporal relationship of the event. In the Sennwald landslide, 92 million m3 of limestones detached from the south-eastern wall of the Säntis nappe and slid with a maximum travel distance of ~4'500 m and a "fahrboeschung" angle of 15° along the SE-dipping sliding plane almost parallel to the orientation of the bedding plane. Numerical run-out modelling results match the extent and the thickness of landslide deposits as observed in the field. The original bedrock stratigraphy was preserved as geologically the top layer in the bedrock package travelled the farthest and the bottom layer came to rest closest to the release bedrock wall during the landslide. Velocities of maximum 90 m/s were obtained from the numerical run-out modelling. Total Cl and 36Cl were determined at ETH AMS facility with isotope dilution methods defined in the literature (Ivy-Ochs et al., 2004). Surface exposure ages of landslide deposits in the accumulation area are revealed from twelve boulders. The distribution of limestone boulders in the accumulation area, the exposure ages, and the numerical run-out modelling support the hypothesis that the Sennwald landslide was a single catastrophic event. The event is likely to have been triggered by at least light to moderate earthquakes (Mw=4.0-6.0). The historical and the last 40-year

  16. Late Pliocene-Quaternary evolution of outermost hinterland basins of the Northern Apennines (Italy), and their relevance to active tectonics

    NASA Astrophysics Data System (ADS)

    Sani, Federico; Bonini, Marco; Piccardi, Luigi; Vannucci, Gianfranco; Delle Donne, Dario; Benvenuti, Marco; Moratti, Giovanna; Corti, Giacomo; Montanari, Domenico; Sedda, Lorenzo; Tanini, Chiara

    2009-10-01

    We examine the tectonic evolution and structural characteristics of the Quaternary intermontane Mugello, Casentino, and Sansepolcro basins, in the Northern Apennines fold-and-thrust belt. These basins have been classically interpreted to have developed under an extensional regime, and to mark the extension-compression transition. The results of our study have instead allowed framing the formation of these basins into a compressive setting tied to the activity of backthrust faults at their northeastern margin. Syndepositional activity of these structures is manifested by consistent architecture of sediments and outcrop-scale deformation. After this phase, the Mugello and Sansepolcro basins experienced a phase of normal faulting extending from the middle Pleistocene until Present. Basin evolution can be thus basically framed into a two-phase history, with extensional tectonics superposed onto compressional structures. Analysis of morphologic features has revealed the occurrence of fresh fault scarps and interaction of faulting with drainage systems, which have been interpreted as evidence for potential ongoing activity of normal faults. Extensional tectonics is also manifested by recent seismicity, and likely caused the strong historical earthquakes affecting the Mugello and Sansepolcro basins. Qualitative comparison of surface information with depth-converted seismic data suggests the basins to represent discrete subsiding areas within the seismic belt extending along the axial zone of the Apennines. The inferred chronology of deformation and the timing of activity of normal faults have an obvious impact on the elaboration of seismic hazard models.

  17. Tectonic setting of basic igneous and metaigneous rocks of Borborema Province, Brazil using multi-dimensional geochemical discrimination diagrams

    NASA Astrophysics Data System (ADS)

    Verma, Sanjeet K.; Oliveira, Elson P.

    2015-03-01

    Fifteen multi-dimensional diagrams for basic and ultrabasic rocks, based on log-ratio transformations, were used to infer tectonic setting for eight case studies of Borborema Province, NE Brazil. The applications of these diagrams indicated the following results: (1) a mid-ocean ridge setting for Forquilha eclogites (Central Ceará domain) during the Mesoproterozoic; (2) an oceanic plateau setting for Algodões amphibolites (Central Ceará domain) during the Paleoproterozoic; (3) an island arc setting for Brejo Seco amphibolites (Riacho do Pontal belt) during the Proterozoic; (4) an island arc to mid-ocean ridge setting for greenschists of the Monte Orebe Complex (Riacho do Pontal belt) during the Neoproterozoic; (5) within-plate (continental) setting for Vaza Barris domain mafic rocks (Sergipano belt) during the Neoproterozoic; (6) a less precise arc to continental rift for the Gentileza unit metadiorite/gabbro (Sergipano belt) during the Neoproterozoic; (7) an island arc setting for the Novo Gosto unit metabasalts (Sergipano belt) during Neoproterozoic; (8) continental rift setting for Rio Grande do Norte basic rocks during Miocene.

  18. Petrographic and geochemical characteristics of the Paleogene sedimentary rocks from the North Jiangsu Basin, Eastern China: implications for provenance and tectonic setting

    NASA Astrophysics Data System (ADS)

    Zhang, Ni; Lin, Chun-Ming; Zhang, Xia

    2014-08-01

    The petrography and geochemistry (major, trace, and rare earth elements) of clastic sedimentary rocks from the Paleogene Dainan Formation (E2 d) in the North Jiangsu Basin, eastern China, are investigated to trace their provenance and to constrain their tectonic setting. The studied samples are characterized by LREE enrichment, flat HREE, and negative Eu anomaly similar to the upper continental crust composed chiefly of felsic components in the source area. Petrographic observation indicates that the sandstones contain predominant metamorphic and sedimentary clasts that were derived from peripheral recycled orogen and intrabasinal materials. The trace element ratios (Co/Th, La/Sc, La/Th, and Th/U) and the La-Th-Sc ternary plot further confirm that the sandstones are derived from granitic gneiss sources from recycled orogen and the intrabasinal mixed sedimentary provenance. The granitic gneiss source rocks may have derived from the Proterozoic granitic gneiss denuded in the eastern Dabie-Sulu orogen; and the intrabasinal provenance may come from the underlying strata during the Late Paleocene Wubao movement. The chemical index of alteration (CIA) and A-CN-K plot show that these source rocks may have experienced weak to medium chemical weathering. Analysis on tectonic setting of the source area suggests an active continental margin, which is intimate with tectonic feature of the Dabie-sulu orogen and the Yangtze block. In summary, we suggest that the North Jiangsu Basin is an ideal site for the study of the coupling between the uplift of the orogen and the subsidence of the foreland basin.

  19. Geodynamically unusual settings of sedimentary rock and ore formation due to tectonic-decompression effects

    SciTech Connect

    Goryainov, P.M.

    1984-05-01

    The traditional views of terrigenous rocks as products of classical sedimentary cycle, ''mobilization-transport-deposition,'' are not universal. Detrital rocks are sometimes formed due to flaking and fracturation of rocks of rising blocks. The process is produced by tectonic-decompression mechanisms - the origination of a gradient of excessive stress and its discharge. It is incorrect to classify rocks created by this phenomenon with weathering crusts. The origins of certain terrigenous rocks, as well as products of low-temperature chemical processing, are connected with deep-volume decompression (brecciation, stockwork formation, formation of pipes and columns of igneous rocks, and chamber pegmatite and karst formation). The ore concentrations associated with such entities and appearing as stratiform deposits are most likely not exogenous, but they complete the endogenous history of the block concerned. The means and methods tested on typical endogenous deposits may therefore prove valuable in predicting certain varieties of stratiform deposits.

  20. Tectonic and geodynamic setting of oil and gas basins of the Soviet Union

    SciTech Connect

    Khain, V.E.; Sokolov, B.A. ); Kleshchev, K.A.; Shein, V.S. )

    1991-02-01

    Within the territory of the Soviet Union and its off-shore economic zone are about 70 sedimentary basins containing oil and gas. The basins include almost all basin types described in present-day plate-tectonic classifications, namely (1) intracontinental and pericontinental rifts, suprarift syneclises, and zones of pericratonic downwarps; (2) ancient passive margins of continents with adjacent overthrust fold system; (3) modern passive margins of continents; (4) zones of convergence of lithospheric plates (i.e., zones of subduction of oceanic plates below continental plates); and (5) zones of collision of continental lithospheric plates. So, far, the only type of basin not identified within the territory of the Soviet Union is the pull-apart basin. The location and distribution of oil and gas deposits in the section of a basin, prevailing types of traps, and scale of potential resources are all features influenced by the geodynamic type of the basin.

  1. K-T magmatism of western Rajasthan, India: Manifestation of Reunion plume activity or extensional lithospheric tectonics?

    NASA Astrophysics Data System (ADS)

    Sharma, K.

    2004-12-01

    Seychelles microcontinent from India, sedimentary basin development in western Rajasthan and the alkaline magmatism of Mundwara, Sarnu-Dandali and elsewhere are considered to be the products of Reunion plume activity in western India. However, basin development began in western Rajasthan in the Jurassic period and no plume has been suggested for this. The continual extensional tectonic regime caused deep fractures in the continental and oceanic lithosphere. The Cambay-Sanchor-Barmer rift developed in continental lithosphere. The Mundwara, Sarnu-Dandali and Barmer magmatism with nephelinite-carbonatite affinity at the basin margin represents a typical rift-tectonic setting. The tectonic setting and crustal development during the K-T period in western Rajasthan represents an extensional tectonic regime rather than the manifestation of Reunion plume activity.

  2. Geochemical, geochronological characterization and tectonic setting of the metamorphic rocks from the Biga Peninsula, NW Turkey

    NASA Astrophysics Data System (ADS)

    Şengün, F.; Tunç, Ä.°. O.; Yiǧitbaş, E.

    2012-04-01

    The Biga Peninsula in the northwest Turkey is one of the world's important natural laboratories to study geochronology due to having complex geology. The Biga Peninsula has different metamorphic basements including Kazdağ Massif, Çamlıca metamorphics, Kemer metamorphics and Karadağ Massif under cover of the Cenozoic volcano-sedimentary association. The Çamlıca metamorphic assemblage are one of the most critical regions for understanding of the geology of northwestern Turkey. The Çamlıca metamorphic association located on the westernmost part of Turkey is mainly composed of the Andıktası formation, the Dedetepe formation and the Salihler formation, from bottom to top. Metasedimentary rocks of the Çamlıca metamorphics have high SiO2 and medium Al2O3 and TiO2 values. The protolith of these metasediments is arkose-subarkose and greywacke. However, whole-rock geochemistry for the HP eclogite/blueschist within the Çamlıca metamorphics suggests that their protolith was basalt with high TiO2 and K2O-Na2O content and Nb/Y ratios. REE pattern and trace element contents of the HP eclogite/blueschist similar to typical MORB based on tectonic discrimination diagrams. The metavolcanic rocks occurring on the lowest part of the Çamlıca metamorphicassociation has andesitic composition with calc-alkaline character. All metavolcanic rocks in this unit cluster within the volcanic arc field. Zircon grains from metavolcanic rocks and HP eclogite/blueschists were dated by LA-ICPMS. Zircon ages of two metavolcanic samples yielded 328.6 ± 3.5 Ma and 343.2 ± 2.6 Ma, respectively. These ages are interpreted as the time of protolith crystallization of metavolcanic rocks. Moreover, zircon ages from HP eclogite/blueschist yielded 338 ± 1.8 Ma (Early Carboniferous) which is interpreted as the age of protolith crystallization of HP eclogite/blueschist. Geochemical and isotopic data indicate that Early Carboniferous Variscan ages within the Sakarya Zone may form the eastern

  3. Fast Episodes of West-Mediterranean-Tyrrhenian Oceanic Opening and Revisited Relations with Tectonic Setting.

    PubMed

    Savelli, Carlo

    2015-01-01

    Extension and calc-alkaline volcanism of the submerged orogen of alpine age (OAA) initiated in Early Oligocene (~33/32 Ma) and reached the stage of oceanic opening in Early-Miocene (Burdigalian), Late-Miocene and Late-Pliocene. In the Burdigalian (~20-16 Ma) period of widespread volcanism of calcalkaline type on the margins of oceanic domain, seafloor spreading originated the deep basins of north Algeria (western part of OAA) and Sardinia/Provence (European margin). Conversely, when conjugate margins' volcanism has been absent or scarce seafloor spreading formed the plains Vavilov (7.5-6.3 Ma) and Marsili (1.87-1.67 Ma) within OAA eastern part (Tyrrhenian Sea). The contrast between occurrence and lack of margin's igneous activity probably implies the diversity of the geotectonic setting at the times of oceanization. It appears that the Burdigalian calcalkaline volcanism on the continental margins developed in the absence of subduction. The WNW-directed subduction of African plate probably commenced at ~16/15 Ma (waning Burdigalian seafloor spreading) after ~18/16 Ma of rifting. Space-time features indicate that calcalkaline volcanism is not linked only to subduction. From this view, temporal gap would exist between the steep subduction beneath the Apennines and the previous, flat-type plunge of European plate with opposite direction producing the OAA accretion and double vergence. PMID:26391973

  4. Fast Episodes of West-Mediterranean-Tyrrhenian Oceanic Opening and Revisited Relations with Tectonic Setting

    PubMed Central

    Savelli, Carlo

    2015-01-01

    Extension and calc-alkaline volcanism of the submerged orogen of alpine age (OAA) initiated in Early Oligocene (~33/32 Ma) and reached the stage of oceanic opening in Early-Miocene (Burdigalian), Late-Miocene and Late-Pliocene. In the Burdigalian (~20–16 Ma) period of widespread volcanism of calcalkaline type on the margins of oceanic domain, seafloor spreading originated the deep basins of north Algeria (western part of OAA) and Sardinia/Provence (European margin). Conversely, when conjugate margins’ volcanism has been absent or scarce seafloor spreading formed the plains Vavilov (7.5–6.3 Ma) and Marsili (1.87–1.67 Ma) within OAA eastern part (Tyrrhenian Sea). The contrast between occurrence and lack of margin’s igneous activity probably implies the diversity of the geotectonic setting at the times of oceanization. It appears that the Burdigalian calcalkaline volcanism on the continental margins developed in the absence of subduction. The WNW-directed subduction of African plate probably commenced at ~16/15 Ma (waning Burdigalian seafloor spreading) after ~18/16 Ma of rifting. Space-time features indicate that calcalkaline volcanism is not linked only to subduction. From this view, temporal gap would exist between the steep subduction beneath the Apennines and the previous, flat-type plunge of European plate with opposite direction producing the OAA accretion and double vergence. PMID:26391973

  5. Fast Episodes of West-Mediterranean-Tyrrhenian Oceanic Opening and Revisited Relations with Tectonic Setting

    NASA Astrophysics Data System (ADS)

    Savelli, Carlo

    2015-09-01

    Extension and calc-alkaline volcanism of the submerged orogen of alpine age (OAA) initiated in Early Oligocene (~33/32 Ma) and reached the stage of oceanic opening in Early-Miocene (Burdigalian), Late-Miocene and Late-Pliocene. In the Burdigalian (~20-16 Ma) period of widespread volcanism of calcalkaline type on the margins of oceanic domain, seafloor spreading originated the deep basins of north Algeria (western part of OAA) and Sardinia/Provence (European margin). Conversely, when conjugate margins’ volcanism has been absent or scarce seafloor spreading formed the plains Vavilov (7.5-6.3 Ma) and Marsili (1.87-1.67 Ma) within OAA eastern part (Tyrrhenian Sea). The contrast between occurrence and lack of margin’s igneous activity probably implies the diversity of the geotectonic setting at the times of oceanization. It appears that the Burdigalian calcalkaline volcanism on the continental margins developed in the absence of subduction. The WNW-directed subduction of African plate probably commenced at ~16/15 Ma (waning Burdigalian seafloor spreading) after ~18/16 Ma of rifting. Space-time features indicate that calcalkaline volcanism is not linked only to subduction. From this view, temporal gap would exist between the steep subduction beneath the Apennines and the previous, flat-type plunge of European plate with opposite direction producing the OAA accretion and double vergence.

  6. The Tak Batholith, Thailand: the evolution of contrasting granite types and implications for tectonic setting

    NASA Astrophysics Data System (ADS)

    Mahawat, C.; Atherton, M. P.; Brotherton, M. S.

    The Tak Batholith, Thailand, is made up of four zoned plutons, the youngest of which is 210 Ma old. The composition of the plutons changes from granodioritic in the oldest, through monzonitic and monzogranitic to syenogranitic in the youngest. The earliest pluton (Eastern) shows an extended compositional range and is calc-alkaline-granodioritic, medium K in the sense of Lameyre and Bowden. It is similar to classic Andean Cordilleran Batholith plutons. The three later plutons (Western, Mae Salit and Tak), the first of which also shows an extended compositional range, are all calc-alkaline- monzonitic, high K plutons characterised by the early precipitation of U, Th, REE rich accessory minerals and K-feldspar. In this sense they are very different from the Eastern pluton, in which the dominant early felsic phase crystallising is plagioclase and accessory mineral precipitation tends to be late. The changes in major and trace element composition of the plutons with time are similar to that seen in an increasing K volcanic series at an active continental margin. Indeed, the final member is chemically similar to shoshonitic volcanic rocks and by analogy the plutonic sequence is considered to be due to a change from subduction to strike-slip and then uplift, which brought mantle of different composition into the source region beneath the Tak Batholith. In such situations simple classifications relating a batholith to end-member source and geotectonic setting may be misleading.

  7. Geochemical and isotopic constraints on the tectonic setting of Serra dos Carajas belt, eastern Para, Brazil

    NASA Technical Reports Server (NTRS)

    Olszewski, W. J., Jr.; Gibbs, A. K.; Wirth, K. R.

    1986-01-01

    The lower part of the Serra dos Carajas belt is the metavolcanic and metasedimentary Grao para Group (GPG). The GPG is thought to unconformably overlie the older (but undated) Xingu Complex, composed of medium and high-grade gneisses and amphibolite and greenstone belts. The geochemical data indicate that the GPG has many features in common with ancient and modern volcanic suites erupted through continental crust. The mafic rocks clearly differ from those of most Archean greenstone belts, and modern MORB, IAB, and hot-spot basalts. The geological, geochemical, and isotopic data are all consistent with deposition on continental crust, presumably in a marine basin formed by crustal extension. The isotopic data also suggest the existence of depleted mantle as a source for the parent magmas of the GPG. The overall results suggest a tectonic environment, igneous sources, and petrogenesis similar to many modern continental extensional basins, in contrast to most Archean greenstone belts. The Hammersley basin in Australia and the circum-Superior belts in Canada may be suitable Archean and Proterozoic analogues, respectively.

  8. Recent tectonic activity on Pluto driven by phase changes in the ice shell

    NASA Astrophysics Data System (ADS)

    Hammond, Noah P.; Barr, Amy C.; Parmentier, Edgar M.

    2016-07-01

    The New Horizons spacecraft has found evidence for geologic activity on the surface of Pluto, including extensional tectonic deformation of its water ice bedrock see Moore et al. (2016). One mechanism that could drive extensional tectonic activity is global surface expansion due to the partial freezing of an ocean. We use updated physical properties for Pluto and simulate its thermal evolution to understand the survival of a possible subsurface ocean. For thermal conductivities of rock less than 3 W m-1 K-1, an ocean forms and at least partially freezes, leading to recent extensional stresses in the ice shell. In scenarios where the ocean freezes and the ice shell is thicker than 260 km, ice II forms and causes global volume contraction. Since there is no evidence for recent compressional tectonic features, we argue that ice II has not formed and that Pluto's ocean has likely survived to present day.

  9. Using vertical electrical soundings for characterizing hydrogeological and tectonic settings in Deir El-Adas area, Yarmouk Basin, Syria

    NASA Astrophysics Data System (ADS)

    Al-Fares, Walid

    2016-06-01

    The present study is aimed at characterizing the subsurface geological and tectonic structure in Deir El-Adas area, by using Vertical Electrical Sounding survey (VES) and hydrogeological investigations, in order to determine the causes of the failure for the majority of the wells drilled in the area. The survey data was treated in three different approaches including direct VES inversion, pseudo-2D method and horizontal profiling, in order to maximize the reliability of the data interpretation. The results revealed the presence of a local faulted anticline structure at the top of the Paleogene formation, underneath the basaltic outcrops where Deir El-Adas village is situated. The appearance of this subsurface anticline structure has complicated the local hydrogeological situation, and most likely led to limitation of the groundwater recharge in the area. Moreover, the performed piezometric and discharge maps indicated the presence of a notable groundwater watershed, in addition to feeble water productivity of the wells drilled adjacent to Deir El-Adas, mostly related to the subsurface geological and tectonic settings in the area.

  10. Copernican tectonic activities in the northwestern Imbrium region of the Moon

    NASA Astrophysics Data System (ADS)

    Daket, Yuko; Yamaji, Atsushi; Sato, Katsushi

    2015-04-01

    Mare ridges and lobate scarps are the manifestations of horizontal compression in the shallow part of the Moon. Conventionally, tectonism within mascon basins has been thought to originate from mascon loading which is syndepositional tectonics (e.g., Solomon and Head, 1980). However, Ono et al. (2009) have pointed out that the subsurface tectonic structures beneath some mare ridges in Serenitatis appeared to be formed after the deposition of mare strata. Watters et al. (2010) also reported Copernican lobate scarps. Those young deformations cannot be explained by the mascon loading and are possibly ascribed to global cooling, orbital evolution and/or regional factors. Since mare ridges are topographically larger than lobate scarps, they might have large contribution to the recent contraction. In this study, we estimated until when the tectonic activities of mare ridges lasted in the northwestern Imbrium region. In order to infer the timing of the latest ages of tectonic activities, we used craters dislocated by the thrust faults that run along to the mare ridges in the study area. The ages of dislocated craters indicate the oldest estimate of the latest tectonic activity of the faults, because those craters must have existed during the tectonic activities. The ages of craters are inferred by the degradation levels classified by Trask (1971). We found ~450 dislocated craters in the study area. About 40 of them are smaller than 100 meter in diameter. Sub-hundred-meter-sized craters that still maintain their morphology sharp are classified into Copernican Period. Those small dislocated craters are interspersed all over the region, indicating that the most of the mare ridges in the study area were tectonically active in Copernican Period. In addition, we also found two sub-hundred-meter-sized craters dislocated by a graben at the west of Promontorium Laplace, indicating horizontal extension existed at Copernican Period. Consequently, tectonic activities in the study

  11. Salts as indicators of tectonic activity along Nesson anticline, North Dakota

    SciTech Connect

    Lefever, J.A.; Lefever, R.D.; Anderson, S.B.

    1988-07-01

    The Nesson anticline is the major north-south-trending structure in the North Dakota portion of the Williston basin. The trace of the anticline is marked by nearly continuous production for 110 mi (175 km) from the Canadian border south to Dunn County; production is from 13 different stratigraphic zones. Previous studies have shown that the central and southern parts of the anticline, from Beaver Lodge field south to Rattlesnake Point field, consist of at least nine structurally independent areas, each of which has an individual tectonic history. Isopach patterns indicate that most of the areas underwent their greatest tectonic activity during the Devonian and Early Mississippian, although a few areas were active during the early Mesozoic as well. Ten traceable salts are present along the anticline in the Prairie (Devonian), Charles (Mississippian), Opeche (Permian), Spearfish (Triassic), and Pipe Formations (Jurassic). The isopach patterns of the individual salts indicate contemporaneous tectonic activity through thickening or thinning of the salt. Postdepositional activity is indicated by the absence of a salt; the timing of the activity may be estimated from the presence of compensating section above the level of the salt. Their results indicate that, in addition to the times given above, significant tectonic activity took place along the anticline during the Late Mississippian, late Jurassic, and Early Cretaceous.

  12. Preliminary study on hydrogeology in tectonically active areas.

    SciTech Connect

    Lowry, Thomas Stephen; Lappin, Allen R.; Gettemy, Glen L.; Jensen, Richard Pearson; Arnold, Bill Walter; James, Scott Carlton; Lee, Moo Yul; Meier, Diane A.

    2006-09-01

    This report represents the final product of a background literature review conducted for the Nuclear Waste Management Organization of Japan (NUMO) by Sandia National Laboratories, Albuquerque, New Mexico, USA. Internationally, research of hydrological and transport processes in the context of high level waste (HLW) repository performance, has been extensive. However, most of these studies have been conducted for sites that are within tectonically stable regions. Therefore, in support of NUMO's goal of selecting a site for a HLW repository, this literature review has been conducted to assess the applicability of the output from some of these studies to the geological environment in Japan. Specifically, this review consists of two main tasks. The first was to review the major documents of the main HLW repository programs around the world to identify the most important hydrologic and transport parameters and processes relevant in each of these programs. The review was to assess the relative importance of processes and measured parameters to site characterization by interpretation of existing sensitivity analyses and expert judgment in these documents. The second task was to convene a workshop to discuss the findings of Task 1 and to prioritize hydrologic and transport parameters in the context of the geology of Japan. This report details the results and conclusions of both of these Tasks.

  13. Reservoir Characterization and Tectonic Settings of Ahwaz Sandstone Member of the Asmari Formation in the Zagros Mountain, SW of Iran

    NASA Astrophysics Data System (ADS)

    Adabi, M. H.; Sadeghi, A. D.; Hosseini, M.; Moalemi, A.; Lotfpour, A.; Khatibi Mehr, M.; Salehi, M.; Zohdi, A.; Jafarzadeh, M.

    2009-04-01

    The Ahwaz Sandstone Member of the Asmari Formation, the major oil reservoir in Zagros mountain, have been studied to understand the distribution, provenance, tectonic setting and reservoir characteristic of Ahwaz Sandstone intervals as an exploration target. This study was based on petrographic and geochemical analysis of 16 core samples from 13 oilfields in the Dezful Embayment zone, and 2 surface sections (Katula and Khami) in Izeh zone. Petrographic studies of 400 thin sections and geochemical analysis indicated that sandstones consist of quartzarenite (Khami surface section), sublitharenite ( Katula surface section) and subarkose (subsurface sections). The modal analysis of medium size and well sorted samples show a recycled orogen (Katula outcrop) and craton (Khami and subsurface sections) tectonic setting. The parent rocks for Ahwaz Sandstone, based on petrographic point counting suggest a low to medium grade metamorphic and plutonic source. Petrographic and grain size analysis indicate a shallow shoreline to barrier bar environments. Heavy minerals in sandstones have mostly plutonic source and abundance of stable heavy mineral, along with well rounded and high sphericity, support stable cratonic source for subsurface sections and Khami surface section. However, in Katula section, heavy minerals have metamorphic source. Facies map illustrated that siliciclastic sediments in Asmari Formation during Rupelian time comes from south-west and north west of the study area. During Chattian, sand distribution reaches to the maximum level and sediments arrived from south-west, north-west and also north-east of the study area. In Aquitanian, sandstones sourced from two areas of south-west and north-west. In Burdigalian stage, sandstone sourced only from south and south-west. These sandstones have limited distributions. Tectonic settings based on geochemical analysis, plotted on discrimination diagrams, suggest that passive continental margin. These sandstones were

  14. Sedimentary development of the Oligocene Karsantı Basin, southern Turkey, in its regional tectonic setting

    NASA Astrophysics Data System (ADS)

    Ünlügenç, Ulvi Can; Akıncı, Ahmet Can

    2015-06-01

    Following Late Cretaceous ophiolite and melange emplacement within the Tauride belt several Neogene sedimentary basins of variable size were formed along the southern flank of the Taurus continent in southern Turkey. These include the Pozantı and Karsantı Basins and the regional scale Çukurova Basin Complex, extending southwestwards into the Cilicia-Kyrenia Basin. The Karsantı Basin is bounded by the regional scale sinistral Ecemiş Fault Zone to the west, the East Anatolian Fault Zone to the southeast and the Negoene Adana Basin to the south. Deformed Palaeozoic and Mesozoic rock units that display an irregular palaeotopography form the basement of the Karsantı Basin. These units are overlain by an allochthonous Kızıldağ melange and by thrust slices of basic/ultrabasic ophiolitic rocks (Faraşa ophiolites) that were emplaced in this region during the Late Maastrichtian. The Karsantı Basin was formed during the Oligocene above the thrust sheets. The Karsantı Basin disconformably overlies the ophiolitic nappes and is interpreted as a N-S trending half graben which was probably most active following the deposition of lacustrine sediments during the late Oligocene. The main Karsantı Basin infill is represented by four lithological units: 1. Alluvial fan deposits (A1), 2. shallow-marine deposits (A2), 3. lacustrine deposits (A3), and 4. fluvial deposits (A4). These sediments were deposited during the Oligocene, prior to the initiation of the main Adana Basin, which formed in a separate intermontane setting. The Karsantı Basin fill is unconformably overlain by early Miocene sediments of the Neogene Adana basin.

  15. Plate-Tectonic Analysis of Shallow Seismicity: Apparent Boundary Width, beta-Value, Corner Magnitude, Coupled Lithosphere Thickness, and Coupling in 7 Tectonic Settings

    NASA Astrophysics Data System (ADS)

    Bird, P.; Kagan, Y. Y.

    2003-12-01

    A new plate model [Bird, 2003, G3, 10.1029/2001GC000252] is used to analyze the mean seismicities of 7 types of plate boundary (CRB continental rift boundary, CTF continental transform fault, CCB continental convergent boundary, OSR oceanic spreading ridge, OTF oceanic transform fault, OCB oceanic convergent boundary, SUB subduction zone). We compare the plate-like (non-orogen) regions of model PB2002 with the CMT catalog to select apparent boundary half-widths, and then assign 95% of shallow earthquakes to one of these settings. A tapered Gutenberg-Richter model of the frequency/moment relation is fit to the subcatalog for each setting by maximum-likelihood. Best-fitting β values range from 0.53 to 0.92, but all 95%-confidence ranges are consistent with a common value of 0.61-0.66. To better determine some corner magnitudes we expand the subcatalogs by: (1) inclusion of orogens; and (2) inclusion of years 1900-1975 from the catalog of Pacheco and Sykes [1992]. Combining both earthquake statistics and the plate-tectonic constraint on moment rate, corner magnitudes include: CRB 7.64-.26+.76, CTF 8.01-.21+.45, CCB 8.46-.39+.21, OCB 8.04-.22+.52, and SUB 9.58-.46+.48. Coupled lithosphere thicknesses are found to be: CRB 3.0-1.4+7.0 km; CTF 8.6-4.1+11 km; CCB 18-11+? km; OSR 0.13-0.09+.13 km for normal-faulting and 0.40-.21+? km for strike-slip; OTF 12-7.1+?, 1.6-0.5+1.4, and 1.5-0.6+1.2 km at low, medium, and high velocities; OCB 3.8-2.3+13.7 km, and SUB 18.0-10.8+? km. Generally high coupling of subduction and continental plate boundaries suggests that here all seismic gaps are dangerous unless proven to be creeping. Generally low coupling within oceanic lithosphere suggests a different model of isolated seismic asperities surrounded by large seismic gaps which may be permanent.

  16. The River Network, Active Tectonics and the Mexican Subduction Zone, Southwest Mexico

    NASA Astrophysics Data System (ADS)

    Gaidzik, K.; Ramirez-Herrera, M. T.; Kostoglodov, V.; Basili, R.

    2014-12-01

    Rivers, their profiles and network reflect the integration of multiple processes and forces that are part of the fundamental controls on the relief structure of mountain belts. The motivation of this study is to understand active tectonic processes in the forearc region of subduction zones, by distinguishing evidence of active deformation using the river network and topography. To this end, morphotectonic and structural studies have been conducted on fifteen drainage basins on the mountain front, parallel to the Mexican subduction zone, where the Cocos plate underthrusts the North American plate. The southwest - northeast Cocos plate subduction stress regime initiated ca. 20 MA. NE-SW to NNE-SSW normal faults as well as sub-latitudinal to NW-SE strike-slip faults (both dextral and sinistral) constitute the majority of mesofaults recorded in the field within the studied drainage basins. Occasionally dextral N-S strike-slip faults also occur. The stress tensor reconstruction suggests two main evolution stages of these faults: 1) the older is dominated by a NW-SE to WNW-ESE extensional regime and 2) the younger is a transcurrent regime, with NNE-SSW σ1 axis. The drainage pattern is strongly controlled by tectonic features, whereas lithology is only a subordinate factor, with only one exception (Petatlán river). Generally, major rivers flow from north to south mainly through NE-SW and NNE-SSW normal faults, and/or sub-longitudinal dextral (also locally sinistral) strike-slip faults. In the central and eastern part of the studied area, rivers also follow NW-SE structures, which are generally normal or sinistral strike-slip faults (rarely reverse). In most cases, local deflections of the river main courses are related to sub-latitudinal strike-slip faults, both dextral and sinistral. Within the current stress field related to the active Cocos subduction, both normal and strike-slip fault sets could be reactivated. Our analysis suggests that strike-slip faults, mainly

  17. Promoting Physical Activity through Goal Setting Strategies

    ERIC Educational Resources Information Center

    Martinez, Ray

    2004-01-01

    Physical educators are used to setting specific goals for students within a given unit. Here, the author emphasizes that they should also encourage students to set their own goals. Goal setting engages students in the learning process and allows them to develop the skills that support an active lifestyle. The author presents goal setting…

  18. Tectonic activity and structural features of active intracontinental normal faults in the Weihe Graben, central China

    NASA Astrophysics Data System (ADS)

    Rao, Gang; Lin, Aiming; Yan, Bing; Jia, Dong; Wu, Xiaojun

    2014-12-01

    This study examines the tectonic activity and structural features of active normal faults in the Weihe Graben, central China. The Weihe Graben is an area with a high level of historic seismicity, and it is one of the intracontinental systems that developed since Tertiary in the extensional environment around the Ordos Block. Analysis of high-resolution remote-sensing imagery data, field observations, and radiocarbon dating results reveal the following: i) active normal faults are mainly developed within a zone < 500 m wide along the southern border of the eastern part of the Weihe Graben; ii) the active faults that have been identified are characterized by stepwise fault scarps dipping into the graben at angles of 40°-71°; iii) there are numerous discontinuous individual fault traces, ranging in length from a few tens of meters to 450 m (generally < 200 m); iv) fault zone structures, topographic features, and fault striations on the main fault planes indicate almost pure normal-slip; and v) late Pleistocene-Holocene terrace risers, loess, and alluvial deposits have been vertically offset by up to ~ 80 m, with a non-uniform dip-slip rate (throw-rates) ranging from ~ 2.1 to 5.7 mm/yr, mostly 2-3 mm/yr. Our results reveal that active normal faults have been developing in the Weihe Graben under an ongoing extensional environment, probably associated with the pre-existing graben and spreading of the continental crust, and this is in contrast with the Ordos Block and neighboring orogenic regions. These results provide new insights into the nature of extensional tectonic deformation in intracontinental graben systems.

  19. Modern Tectonic Deformation in the Active Basin-and-Range Province Northwest of Beijing, China

    NASA Astrophysics Data System (ADS)

    Mi, Suting; Wen, Xueze

    2013-04-01

    Our study region is the northwest of Beijing, northern north China. The most typical extensional active tectonic area of the China continent, called the active basin-and-range province northwest of Beijing, exist there. This active tectonic province is made up of several NE-trending Quaternary graben basins and horst ranges between basins. An about 1500-year-long written historical record has suggested that there have been no major earthquakes with magnitude 7 or greater occurred in most of the study region since AD 512. So, the characteristic of modern tectonic deformation of the study region and its implication for the future seismic potential of major earthquakes are important scientific issues. In this study, based on data of regional GPS station velocities and active tectonics, combining relocated earthquake distribution, we make a preliminary analysis on the characteristic of the modern tectonic deformation of the study region. We design three zones across deferent segments of the active basin-and-range province to analyze both the present tectonic deformation from the GPS velocity profiles and the major fault's downward-extents from the relocated hypocenters. Our analyses reveal that: (1) Significant NNW-ward and SSE-ward horizontal extension exists on different segments of the active basin-and-range province northwest of Beijing at rates of 2 to 3mm /yr, accompanied with right-lateral shear deformation at 1 to 2mm/yr. (2) On the western and middle segments of the active basin and range province, most of the total horizontal extension and shear deformation happen in the width from the Huangqihai basin to the Datong-Yanggao basin , suggesting that some major faults in this width could have had relatively-high strain build-up. (3) It is possible that one or more basement detachment belts exist under the active basins, and it or they possibly dip(s) southeastern-ward. (4) The modern tectonic extensional rate is up to 2 to 3mm /yr in the study region. However

  20. Large historical earthquakes and tsunamis in a very active tectonic rift: the Gulf of Corinth, Greece

    NASA Astrophysics Data System (ADS)

    Triantafyllou, Ioanna; Papadopoulos, Gerassimos

    2014-05-01

    The Gulf of Corinth is an active tectonic rift controlled by E-W trending normal faults with an uplifted footwall in the south and a subsiding hangingwall with antithetic faulting in the north. Regional geodetic extension rates up to about 1.5 cm/yr have been measured, which is one of the highest for tectonic rifts in the entire Earth, while seismic slip rates up to about 1 cm/yr were estimated. Large earthquakes with magnitudes, M, up to about 7 were historically documented and instrumentally recorded. In this paper we have compiled historical documentation of earthquake and tsunami events occurring in the Corinth Gulf from the antiquity up to the present. The completeness of the events reported improves with time particularly after the 15th century. The majority of tsunamis were caused by earthquake activity although the aseismic landsliding is a relatively frequent agent for tsunami generation in Corinth Gulf. We focus to better understand the process of tsunami generation from earthquakes. To this aim we have considered the elliptical rupture zones of all the strong (M≥ 6.0) historical and instrumental earthquakes known in the Corinth Gulf. We have taken into account rupture zones determined by previous authors. However, magnitudes, M, of historical earthquakes were recalculated from a set of empirical relationships between M and seismic intensity established for earthquakes occurring in Greece during the instrumental era of seismicity. For this application the macroseismic field of each one of the earthquakes was identified and seismic intensities were assigned. Another set of empirical relationships M/L and M/W for instrumentally recorded earthquakes in the Mediterranean region was applied to calculate rupture zone dimensions; where L=rupture zone length, W=rupture zone width. The rupture zones positions were decided on the basis of the localities of the highest seismic intensities and co-seismic ground failures, if any, while the orientation of the maximum

  1. Palaeoproterozoic Volcanic Massive Sulphides (VMS) in the Lithuanian crystalline basement: evidences for a back-arc tectonic setting

    NASA Astrophysics Data System (ADS)

    Skridlaite, Grazina; Siliauskas, Laurynas

    2014-05-01

    which there are amphibolites with layers or lenses of skarns formed in marbles. Some amphibolites resemble porphyritic basalts. These might be dikes of basalts, which are common for back arc VMS surroundings. The volcano-clastic rock from the Lz13 yielded c. 1.83 Ga and c. 1.80 Ga ages. The whole rock Sm-Nd isotopic composition points towards juvenile origin of the rock (TDM=2.08 Ga, ɛNd (1.9) +1.8). After the comparison of the obtained data set with VMS deposits formed in different environments, it is most likely that the volcano-sedimentary sequence of Lz13 was formed in a back arc tectonic setting. The volcano-sedimentary sequence can be correlated with the 1.83 Ga Oskarshamn-Jönköping Belt (Mansfeld et al., 2005) and the volcano-sedimentary Vetlanda formation (Makowsky and Mansfeld, 2013) in southeastern Sweden. The c. 1.83-1.80 Ga volcanic arc and back-arc system continues from southeastern Sweden through the Baltic Sea to Lithuania. This is a contribution to the Open Access Centre activities Mansfeld, J., Beunk, F.F. and Barling, J., 2005. GFF, 127: 149-157 Makowsky, F., Mansfeld, J., 2013. 31st Nordic Geological Winter Meeting, Lund, Sweden, 89-90.

  2. Assessment of relative tectonic activity in the Trichonis Lake graben (Western Greece) using geomorphometry

    NASA Astrophysics Data System (ADS)

    Karymbalis, Efthimios; Valkanou, Kanella; Fubelli, Giandomenico; Ferentinou, Maria; Giles, Philip; Papanastassiou, Dimitris; Gaki-Papanastassiou, Kalliopi; Tsanakas, Konstantinos

    2016-04-01

    In tectonically active areas fluvial systems and mountain fronts are controlled by the type, geometry, and recent activity of faults. The aim of this study is to investigate the contribution of neotectonics to the development of the fluvial landscape of the broader Trichonis Lake area (located in western continental Greece) through quantitative geomorphological analysis. The Trichonis Lake graben is a well-known tectonic depression of Quaternary age, which cuts across the early Tertiary NW-SE fold and thrust structures of the Pindos Mountain belt. It strikes WNW-ESE for a distance of 32 km and has a width of 10 km. The graben at the north and south flanks of the lake is bounded by E-W and NW-SE trending faults. Recent seismic activity (a shallow earthquake sequence in 1975 and a 2007 earthquake swarm) showed the existence of a NNW-SSE normal fault that dips to the NE and bounds the south-eastern shore of the lake. The studied catchments are developed on the hanging walls of these active normal faults. To evaluate the relative tectonic activity in the study area, various morphometric indices were measured for 35 catchments (slope of the valley sides of the catchment, hypsometric integral, catchment asymmetry factor, relief ratio, Melton's ruggedness number, stream-gradient index, ratio of valley floor width to valley height, and catchment shape) and 20 mountain fronts (mountain-front sinuosity index) around the lake. For the measurement of the geomorphometric variables a digital elevation model (DEM) with 2-m spatial resolution was derived from topographic maps at 1:5000 scale with 4-m contour lines, and a series of maps showing the spatial distribution of the variables were produced in a GIS environment. For each morphometric variable the catchments were classified into three classes. The combination of these morphometric variables allowed us to yield two new indices of relative tectonic activity (named IRTA - Index of Relative Tectonic Activity and IAT - Index of

  3. Importance of active tectonics during karst formation. A Middle Eocene to Pleistocene example of the Lina Moutains (Irian Jaya, Indonesia)

    NASA Astrophysics Data System (ADS)

    Thery, J.-M.; Pubellier, M.; Thery, B.; Butterlin, J.; Blondeau, A.; Adams, C. G.

    1999-05-01

    The Lina Moutains show a typical example of karst formation associated to recent and active tectonics. The limestone samples were collected from giant potholes present beneath the heavy rainforest, during speleological expeditions to the Bird's Head of Irian-Jaya. Micropalaeontological data allow us to give a Middle Pleistocene age for the most recent karst formation. A detailed stratigraphy between the Upper Lutetian and the Middle Pleistocene was recorded, with tectonic events during the Oligocene and Pleistocene. The edge of the resurgence layer was also dated. We also conclude the probable existence of a subterraneous network downhill of the karst within the most recent levels of the Kais Limestone formation. We replace this formation within the tectonic evolution of this area between the Eocene and the Middle Pleistocene, in conjunction with the oblique convergence of the Pacific plate carrying volcanic arc fragments and the Australian margin, which resulted in folding, normal faulting associated with local extension, and wrench motion, which are settings capable of creating uplift of the carbonated platform.

  4. New correlations and tectonic setting of the Kalahari Copperbelt in Namibia and Botswana

    NASA Astrophysics Data System (ADS)

    Lehmann, Jeremie; Master, Sharad; Rankin, William; Kinnaird, Judith A.

    2014-05-01

    magnetic response with the 2 km-thick Kgwebe Formation in Botswana where it constitutes the first well-dated post-Palaeoproterozoic event on the Kalahari Craton. Above a major regional unconformity, the following stratigraphic sequence is remarkably similar in both countries, albeit thicker in Namibia (10 km vs. 6 km for the Ghanzi Group). Indeed, sedimentological investigations suggest an open shelf marine depositional environment that deepens from basal marginal mesotidal to deeper water and reduced conditions which are capped by near shore sediments in Botswana only. This sequence was deposited in between ~1100 Ma and the Sturtian glaciation event (~710 Ma), based on a lack of glacial strata. The Cu-Ag deposits are localized within and just below the reduced horizons formed in the deepest environment where rocks in both countries record the ~780-800 Ma global Bitter-Spring negative carbon excursion. This age therefore provides the maximum age of the mineralisation while its upper age is not constrained as in some places the mineralisation is described in literature as post-Damara Orogeny. The important lithostratigraphic control on the aeromagnetic signature enabled detailed indirect mapping of the Kalahari Copperbelt lithotectonic domains. Together with the new paleogeographic and chronological correlations, the continuity of these lithotectonic domains from Namibia to northern Botswana across the Namibia-Botswana border allow revision of existing tectonic models for the formation of the Meso- to Neoproterozoic belt that hosts the Kalahari Copperbelt.

  5. Earthquake mechanisms and active tectonics of the Hellenic subduction zone

    NASA Astrophysics Data System (ADS)

    Shaw, Beth; Jackson, James

    2010-05-01

    We use improved focal mechanisms and centroid depth estimates of earthquakes, combined with GPS velocities, to examine the tectonics of the Hellenic subduction zone, and in particular the processes occurring at both ends of the Hellenic Arc. Nubia-Aegean convergence is accommodated by shallowly dipping thrust-faulting along the subduction-zone interface, as well as by steeper splay faults in the overriding material. From a comparison of observed and expected seismic moment release over the last 100 yr, combined with existing knowledge of the longer-term documented historical record, we confirm earlier suggestions that most (80 per cent) of this convergence is accommodated aseismically, that is, that the subduction zone is uncoupled. This conclusion is robust, even allowing for rare very large earthquakes on splay faults, such as that of AD 365, and also allowing for the contribution of small earthquakes. The downgoing Nubian plate deforms by arc-parallel contraction at all depths, from 200 km seaward of Crete to at least 100 km within the subducting slab. Extensional (T) axes of earthquakes are aligned downdip within the descending slab suggesting that, even if the aseismic prolongation of the slab has reached the 670 km mantle discontinuity, it does not transmit stresses to shallower depths. Shallow thrust-faulting earthquakes on the subduction interface show a divergence of slip vectors round the arc, and GPS measurements show that this is accommodated mainly by E-W extension on normal faults in the overriding Aegean material. The eastern end of the subduction zone, south of Rhodes, displays distributed deformation in the overriding material, including a mixture of strike-slip and splay-thrust faulting, and probably involves rotations about a vertical axes. Here slip on the interface itself is by thrust faulting with slip vectors oblique to the arc but parallel to the overall Nubia-Aegean convergence: there is no evidence for slip-partitioning in the traditional

  6. Tectonic Geomorphology in the Laboratory: Evolution of landscape along an active thrust, normal and strike-slip fault

    NASA Astrophysics Data System (ADS)

    Graveleau, Fabien; Strak, Vincent; Dominguez, Stéphane; Malavieille, Jacques; Chatton, Marina; Manighetti, Isabelle; Petit, Carole

    2015-04-01

    Tectonically controlled landforms develop morphologic features that provide useful markers to investigate crustal deformation and relief growth dynamics. We present here results of morphotectonic experiments obtained with an innovative approach combining tectonic and surface processes (erosion, transport and sedimentation), coupled with accurate model monitoring techniques. This approach allows for a qualitative and quantitative analysis of landscape evolution in response to active deformation in the three end-member geological settings: compression, extension and strike-slip. Experimental results outline first that experimental morphologies evolve significantly at a short timescale. Numerous morphologic markers form continuously, but their lifetime is generally short because erosion and sedimentation processes tend to destroy or bury them. For the compressional setting, the formation of terraces above an active thrust appears mainly controlled by narrowing and incision of the main channel through the uplifting hanging-wall and by avulsion of deposits on fan-like bodies. Terrace formation is irregular even under steady tectonic rates and erosional conditions. Terrace deformation analysis allows retrieving the growth history of the structure and the fault slip rate evolution. For the extensional setting, the dynamics of hanging-wall sedimentary filling appears to control the position of the base level, which in turn controls footwall erosion. Two phases of relief evolution can be evidenced: the first is a phase of relief growth and the second is a phase of upstream propagation of topographic equilibrium that is reached first in the sedimentary basin. During the phase of relief growth, the formation of triangular facets occurs by degradation of the fault scarp and their geometry (height) becomes stationary during the phase of upstream propagation of the topographic equilibrium. For the strike-slip setting, the complex morphology of the wrench zone, composed of

  7. Intraoceanic Arc Tectonic and Sedimentary Processes: Translation from Modern Activity to Ancient Records

    NASA Astrophysics Data System (ADS)

    Draut, A. E.; Clift, P. D.

    2013-12-01

    Records of ancient intraoceanic arc activity, now preserved in continental suture zones, are used to reconstruct paleogeography, plate motion, collision and accretion events, and to understand how continental crust is formed, recycled, and maintained through time. However, interpreting tectonic and sedimentary records after arc-continent collision is complicated by preservation of evidence for some processes and loss of evidence for others. We examine what is lost, and what is preserved, in the translation from modern processes to the ancient record of oceanic subduction zones. Composition of accreted arc terranes differs as a function of arc-continent collision geometry. ';Forward-facing' collision can accrete an oceanic arc onto either a passive or an active continental margin, with the arc facing the continent and colliding trench- and forearc-side first. In ';backward-facing' collision, involving two subduction zones with similar polarity, the arc collides backarc-first with an active continental margin. The preservation of evidence for contemporary sedimentary and tectonic arc processes in the geologic record depends greatly on how well the various parts of the arc survive collision and orogeny in each case. Preservation of arc terranes likely is biased towards those that were in tectonic accretion for tens of millions of years before collision, rather than tectonic erosion. The prevalence of tectonic erosion in modern oceanic subduction zones implies that valuable records of arc processes are commonly destroyed even before collision with a continent. Arc systems are most likely to undergo tectonic accretion shortly before forward-facing collision with a continent, and thus most forearc and accretionary-prism material in ancient arc terranes likely is temporally biased toward the final stages of arc activity, when sediment flux to the trench was greatest. Collision geometry and tectonic erosion vs. accretion are important controls on the ultimate survival of

  8. Coherence between geodetic and seismic deformation in a context of slow tectonic activity (SW Alps, France)

    NASA Astrophysics Data System (ADS)

    Walpersdorf, A.; Sue, C.; Baize, S.; Cotte, N.; Bascou, P.; Beauval, C.; Collard, P.; Daniel, G.; Dyer, H.; Grasso, J.-R.; Hautecoeur, O.; Helmstetter, A.; Hok, S.; Langlais, M.; Menard, G.; Mousavi, Z.; Ponton, F.; Rizza, M.; Rolland, L.; Souami, D.; Thirard, L.; Vaudey, P.; Voisin, C.; Martinod, J.

    2015-04-01

    A dense, local network of 30 geodetic markers covering a 50 × 60 km2 area in the southwestern European Alps (Briançon region) has been temporarily surveyed in 1996, 2006 and 2011 by GPS. The aim is to measure the current deformation in this seismically active area. The study zone is characterized by a majority of extensional and dextral focal mechanisms, along north-south to N160 oriented faults. The combined analysis of the three measurement campaigns over 15 years and up to 16 years of permanent GPS data from the French RENAG network now enables to assess horizontal velocities below 1 mm/year within the local network. The long observation interval and the redundancy of the dense campaign network measurement help to constrain a significant local deformation pattern in the Briançon region, yielding an average E-W extension of 16 ± 11 nanostrain/year. We compare the geodetic deformation field to the seismic deformation rate cumulated over 37 years, and obtain good coherencies both in amplitude and direction. Moreover, the horizontal deformation localized in the Briançon region represents a major part of the Adriatic-European relative plate motion. However, the average uplift of the network in an extensional setting needs the presence of buoyancy forces in addition to plate tectonics.

  9. Evaluating influence of active tectonics on spatial distribution pattern of floods along eastern Tamil Nadu, India

    NASA Astrophysics Data System (ADS)

    Selvakumar, R.; Ramasamy, SM.

    2014-12-01

    Flooding is a naturally recurrent phenomenon that causes severe damage to lives and property. Predictions on flood-prone zones are made based on intensity-duration of rainfall, carrying capacity of drainage, and natural or man-made obstructions. Particularly, the lower part of the drainage system and its adjacent geomorphic landforms like floodplains and deltaic plains are considered for analysis, but stagnation in parts of basins that are far away from major riverine systems is less unveiled. Similarly, uncharacteristic flooding in the upper and middle parts of drainage, especially in zones of an anomalous drainage pattern, is also least understood. Even though topographic differences are attributed for such anomalous spatial occurrence of floods, its genetic cause has to be identified for effective management practice. Added to structural and lithological variations, tectonic movements too impart micro-scale terrain undulations. Because active tectonic movements are slow-occurring, long-term geological processes, its resultant topographical variations and drainage anomalies are least correlated with floods. The recent floods of Tamil Nadu also exhibit a unique distribution pattern emphasizing the role of tectonics over it. Hence a detailed geoinformatics-based analysis was carried out to envisage the relationship between spatial distribution of flood and active tectonic elements such as regional arches and deeps, block faults, and graben and drainage anomalies such as deflected drainage, compressed meander, and eyed drainages. The analysis reveals that micro-scale topographic highs and lows imparted by active tectonic movements and its further induced drainage anomalies have substantially controlled the distribution pattern of flood.

  10. Active tectonics of the Oran (Algeria) Quaternary plain

    NASA Astrophysics Data System (ADS)

    youcef, Bouhadad; rabah, Bensalem; e-hadi, oubaiche

    2016-04-01

    The Oran region, in north-western Algeria, has been hit several times in the past by destructive moderate-sized and strong earthquakes. The Oran October 9th , 1790 (I0= X) was among the strongest seismic events in the western Mediterranean area comparable, if we consider the described effects, to the El- Asnam (1980, Ms=7.3) and Zemmouri (2003, Mw=6.8) earthquakes. Such strong seismic events requires the presence of major active geological structures that are re-activated several times in the past. In this work we present results of a multi- disciplinary study combining geomorphic analysis, field earthquake geological investigations and geophysical methods, undertaken to study the southern border of the Oran Quaternary plain. A 50 km long, SW-dipping and NE-SW trending active fault has been identified that showing clear quaternary deformation. Keywords: earthquake geology, active fault, geomorphic, geophysics, Algeria.

  11. Change in biochemical and morphological characteristics of Lonicera caerulea in tectonically active zone of the Dzhazator River Valley (Altai Mountains)

    NASA Astrophysics Data System (ADS)

    Boyarskikh, I. G.; Khudyaev, S. A.; Platonova, S. G.; Kolotukhin, S. P.; Shitov, A. V.; Kukushkina, T. A.; Chankina, O. V.

    2012-12-01

    Local geophysical and geochemical anomalies affect the polymorphism of taste variations, berry shape, and content of some biologically active substances in Lonicera caerulea leaves in the tectonically active Altai Mountains (Dzhazator River basin).

  12. Geology, age, and tectonic setting of the Cretaceous Sliderock Mountain Volcano, Montana

    USGS Publications Warehouse

    Du Bray, E.A.; Harlan, Stephen S.

    1998-01-01

    The Sliderock Mountain stratovolcano, part of the Upper Cretaceous continental magmatic arc in southwestern Montana, consists of volcaniclastic strata and basaltic andesite lava flows. An intrusive complex represents the volcano's solidified magma chamber. Compositional diversity within components of the volcano appears to reflect evolution via about 50 percent fractional crystallization involving clinopyroxene and plagioclase. 40Ar/39Ar indicate that the volcano was active about 78?1 Ma.

  13. Igneous petrogenesis and tectonic setting of granitic rocks from the eastern Blue Ridge, Alabama Appalachians

    SciTech Connect

    Drummond, M.S. . Geology Dept.); Allison, D.T. . Geology Dept.); Tull, J.F. . Geology Dept.); Bieler, D.B. . Geology Dept.)

    1994-03-01

    A span of 150 my of orogenic activity is recorded within the granitic rocks of the eastern Blue Ridge of Alabama (EBR). Four discrete episodes of plutonism can be differentiated, each event exhibiting distinct field relations and geochemical signatures. (1) Penobscotian stage: this initial stage of plutonic activity is represented by the Elkahatchee Quartz Diorite (EQD), a premetamorphic (495 Ma) batholith and the largest intrusive complex (880 km[sup 2]) exposed in the Blue Ridge. Calc-alkaline I-type tonalite-granodiorite are the principal lithologies, with subordinate cumulate hbl-bt diorite, metadacite, granite and trondhjemite. The parental tonalitic magmas are interpreted to have been derived from a subducted MORB source under eclogite to get amphibolite conditions. (2) Taconic stage: the Kowaliga augen gneiss (KAG) and the Zana granite gneiss (ZG) are 460 Ma granitic bodies that reside in the SE extremity and structurally highest portion of the EBR. Both of these bodies are pre-metamorphic with strongly elongate sill- and pod-like shapes concordant with S[sub 1] foliation. Granite and granodiorite comprise the bulk of the KAG. (3) Acadian stage: Rockford Granite (RG), Bluff springs Granite (BSG, 366 Ma), and Almond Trondhjemite represent a suite of pre- to syn-metamorphic granitic intrusions. (4) late-Acadian stage: The Blakes Ferry pluton (BFP) is a post-kinematic pluton displaying spectacular by schlieren igneous flow structures, but no metamorphic fabric. The pluton's age can be bracketed between a 366 Ma age on the BSG and a 324 Ma K-Ar muscovite age on the BFP. BFP's petrogenesis has involved partial melting a MORB source followed by assimilation of metasedimentary host rock.

  14. Depositional and tectonic setting of the Archean Moodies Group, Barberton Greenstone Belt, South Africa.

    PubMed

    Heubeck, C; Lowe, D R

    1994-01-01

    The 3.22-3.10 Ga old Moodies Group, uppermost unit of the Swaziland Supergroup in the Barberton Greenstone Belt (BGB), is the oldest exposed, well-preserved quartz-rich sedimentary sequence on earth. It is preserved in structurally separate blocks in a heavily deformed fold-and-thrust belt. North of the Inyoka Fault, Moodies strata reach up to 3700 m in thickness. Detailed mapping, correlation of measured sections, and systematic analysis of paleocurrents show that the lower Moodies Group north of the Inyoka Fault forms a deepening- and fining-upward sequence from a basal alluvial conglomerate through braided fluvial, tidal, and deltaic sandstones to offshore sandy shelf deposits. The basal conglomerate and overlying fluvial facies were derived from the north and include abundant detritus eroded from underlying Fig Tree Group dacitic volcanic rocks. Shoreline-parallel transport and extensive reworking dominate overlying deltaic, tidal, and marine facies. The lithologies and arrangement of Moodies Group facies, sandstone petrology, the unconformable relationship between Moodies strata and older deformed rocks, presence of at least one syndepositional normal fault, and presence of basaltic flow rocks and airfall fall tuffs interbedded with the terrestrial strata collectively suggest that the lower Moodies Group was deposited in one or more intramontane basins in an extensional setting. Thinner Moodies sections south of the Inyoka Fault, generally less than 1000 m thick, may be correlative with the basal Moodies Group north of the Inyoka Fault and were probably deposited in separate basins. A northerly derived, southward-thinning fan-delta conglomerate in the upper part of the Moodies Group in the central BGB overlies lower strata with an angular unconformity. This and associated upper Moodies conglomerates mark the beginning of basin shortening by south- to southeast-directed thrust faulting along the northern margin of the BGB and suggest that the upper Moodies

  15. Depositional and tectonic setting of the Archean Moodies Group, Barberton Greenstone Belt, South Africa

    NASA Technical Reports Server (NTRS)

    Heubeck, C.; Lowe, D. R.

    1994-01-01

    The 3.22-3.10 Ga old Moodies Group, uppermost unit of the Swaziland Supergroup in the Barberton Greenstone Belt (BGB), is the oldest exposed, well-preserved quartz-rich sedimentary sequence on earth. It is preserved in structurally separate blocks in a heavily deformed fold-and-thrust belt. North of the Inyoka Fault, Moodies strata reach up to 3700 m in thickness. Detailed mapping, correlation of measured sections, and systematic analysis of paleocurrents show that the lower Moodies Group north of the Inyoka Fault forms a deepening- and fining-upward sequence from a basal alluvial conglomerate through braided fluvial, tidal, and deltaic sandstones to offshore sandy shelf deposits. The basal conglomerate and overlying fluvial facies were derived from the north and include abundant detritus eroded from underlying Fig Tree Group dacitic volcanic rocks. Shoreline-parallel transport and extensive reworking dominate overlying deltaic, tidal, and marine facies. The lithologies and arrangement of Moodies Group facies, sandstone petrology, the unconformable relationship between Moodies strata and older deformed rocks, presence of at least one syndepositional normal fault, and presence of basaltic flow rocks and airfall fall tuffs interbedded with the terrestrial strata collectively suggest that the lower Moodies Group was deposited in one or more intramontane basins in an extensional setting. Thinner Moodies sections south of the Inyoka Fault, generally less than 1000 m thick, may be correlative with the basal Moodies Group north of the Inyoka Fault and were probably deposited in separate basins. A northerly derived, southward-thinning fan-delta conglomerate in the upper part of the Moodies Group in the central BGB overlies lower strata with an angular unconformity. This and associated upper Moodies conglomerates mark the beginning of basin shortening by south- to southeast-directed thrust faulting along the northern margin of the BGB and suggest that the upper Moodies

  16. Linking Europa's plume activity to tides, tectonics, and liquid water

    NASA Astrophysics Data System (ADS)

    Rhoden, Alyssa Rose; Hurford, Terry A.; Roth, Lorenz; Retherford, Kurt

    2015-06-01

    Much of the geologic activity preserved on Europa's icy surface has been attributed to tidal deformation, mainly due to Europa's eccentric orbit. Although the surface is geologically young (30-80 Myr), there is little information as to whether tidally-driven surface processes are ongoing. However, a recent detection of water vapor near Europa's south pole suggests that it may be geologically active. Initial observations indicated that Europa's plume eruptions are time-variable and may be linked to its tidal cycle. Saturn's moon, Enceladus, which shares many similar traits with Europa, displays tidally-modulated plume eruptions, which bolstered this interpretation. However, additional observations of Europa at the same time in its orbit failed to yield a plume detection, casting doubt on the tidal control hypothesis. The purpose of this study is to analyze the timing of plume eruptions within the context of Europa's tidal cycle to determine whether such a link exists and examine the inferred similarities and differences between plume activity on Europa and Enceladus. To do this, we determine the locations and orientations of hypothetical tidally-driven fractures that best match the temporal variability of the plumes observed at Europa. Specifically, we identify model faults that are in tension at the time in Europa's orbit when a plume was detected and in compression at times when the plume was not detected. We find that tidal stress driven solely by eccentricity is incompatible with the observations unless additional mechanisms are controlling the eruption timing or restricting the longevity of the plumes. The addition of obliquity tides, and corresponding precession of the spin pole, can generate a number of model faults that are consistent with the pattern of plume detections. The locations and orientations of these hypothetical source fractures are robust across a broad range of precession rates and spin pole directions. Analysis of the stress variations across

  17. Tectonic setting and hydrocarbon habitat of external Carpathian basins in Romania

    SciTech Connect

    Dicea, O. ); Morariu, D.C.

    1993-09-01

    During the Alpine evolution of Romania, two distinct depositional areas evolved in the external zones of the Carpathians: the Paleogene flysch and Neogene Molasse basin of the eastern Carpathians, and the Paleogene and Neogene Molasse basin of the southern Carpathians. Both basins were compressionally deformed during the Neogene, giving rise to the development of a succession of nappes and thrust sheets. The internal elements of the external Carpathians corresponding to the Tarcau and marginal folds nappes and the external elements forming the sub-carpathian nappe and foredeep were thrusted over significant distances onto the European platform. Intense exploration of the external Carpathian thrustbelt has led to the discovery of more than 100 oil and gas pools. Reservoirs are provided by Oligocene, Burdigalian, Sarmatian, and Pliocene clastic rocks. A prolific hydrocarbon charge is derived from regionally distributed Oligocene oil source rocks. Traps are mainly of the structural type and involve faulted anticlines, [open quotes]scale folds,[close quotes] and compressional structures modified by salt; stratigraphic pinch-out and unconformity related traps play a secondary role. On the basis of selected examples, the development and distribution of hydrocarbon pools will be discussed in terms of thrust kinematics and the structure of different platform blocks. The philosophy of past exploration activities will be reviewed, and both success cases and failures will be discussed. Remaining oil and gas plays, aimed at shallow as well as at deep objectives, will be highlighted.

  18. Magnetic fields over active tectonic zones in ocean

    USGS Publications Warehouse

    Kopytenko, Yu. A.; Serebrianaya, P.M.; Nikitina, L.V.; Green, A.W.

    2002-01-01

    The aim of our work is to estimate the electromagnetic effects that can be detected in the submarine zones with hydrothermal activity. It is known that meso-scale flows appear in the regions over underwater volcanoes or hot rocks. Their origin is connected with heat flux and hot jets released from underwater volcanoes or faults in a sea bottom. Values of mean velocities and turbulent velocities in plumes were estimated. Quasiconstant magnetic fields induced by a hot jet and a vortex over a plume top are about 1-40 nT. Variable magnetic fields are about 0.1-1 nT. These magnetic disturbances in the sea medium create an additional natural electromagnetic background that must be considered when making detailed magnetic surveys. ?? 2002 Elsevier Science Ltd. All rights reserved.

  19. Tectonic Setting of Explosive Volcanic Eruptions in the UPPER Ordovician of the Siberian Platform

    NASA Astrophysics Data System (ADS)

    Huff, W. D.; Dronov, A.; Sell, B. K.; Kanygin, A. V.

    2014-12-01

    In recent years 8 K-bentonite beds have been discovered in the Upper Ordovician of the Tungus basin on the Siberian Platform. All the beds were identified in the outcrops of the Baksian, Dolborian and Burian regional stages, which correspond roughly to the Upper Sandbian, Katian and probably lowermost Hirnantian Global Stages. The 4 lowermost beds from the Baksian and Dolborian Regional Stages were studied in detail. They are represented by thin beds (1-2 cm) of soapy light gray or yellowish plastic clays and usually easily identifiable in the outcrops. The beds were traced in the outcrops over a distance of more than 60 km along the Podkamennaya Tunguska River valley. All K-bentonite beds have been found within the Upper Ordovician cool-water carbonate succession. The four lowermost K-bentonite beds, which were sampled, have been studied by powder X-ray diffraction and scanning electron microscopy together with energy dispersive X-ray analysis. The low percent of smectite in mixed-layer phases reflects a high degree of burial metamorphism since the time of their origin. The K-bentonites provide evidence of intensive explosive volcanism on or near the western margin of the Siberian craton in Late Ordovician time. The K-bentonite beds from the Baksian and Dolborian regional stages (Katian) of the southwestern part of the Tungus basin in Siberia are thus derived from the alteration of volcanic ash falls. All four beds contain volcanogenic euhedral zircon and apatite phenocrysts. Zircon crystals from the uppermost K-bentonite bed within the Baksian regional stage provide a 206Pb/238U age of 450.58±0.27 Ma. The timing of volcanism is surprisingly close to the period of volcanic activity of the Taconic arc near the eastern margin of Laurentia. The Yenisei arc had its continuation along the western continental margin of Siberia and both of them constitute a single Taconic-Yenisei volcanic arc. Field studies of the Upper Ordovician succession along the Moyero River in

  20. Tectonic setting of the Sandia pluton: An orogenic 1.4 Ga granite in New Mexico

    NASA Astrophysics Data System (ADS)

    Kirby, Eric; Karlstrom, Karl E.; Andronicos, Chris L.; Dallmeyer, R. David

    1995-02-01

    east to SE shortening (or least extension) directions in the pluton proper are documented by the intersections of orthogonal dikes. Thus emplacement of the Sandia pluton is interpreted to record a snapshot of regional strains inboard of an active plate margin, rather than local strains generated by emplacement.

  1. Aftershock seismicity and tectonic setting of the 16 September 2015 Mw 8.3 Illapel earthquake, Central Chile

    NASA Astrophysics Data System (ADS)

    Lange, Dietrich; Geersen, Jacob; Barrientos, Sergio; Moreno, Marcos; Grevemeyer, Ingo; Contreras-Reyes, Eduardo; Kopp, Heidrun

    2016-06-01

    Powerful subduction zone earthquakes rupture thousands of square kilometers along continental margins but at certain locations earthquake rupture terminates. To date detailed knowledge of the parameters that govern seismic rupture and aftershocks is still incomplete. On 16 September 2015 the Mw. 8.3 Illapel earthquake ruptured a 200 km long stretch of the Central Chilean subduction zone, triggering a tsunami and causing significant damage. Here we analyze the temporal and spatial pattern of the co-seismic rupture and aftershocks in relation to the tectonic setting in the earthquake area. Aftershocks cluster around the area of maximum coseismic slip, in particular in lateral and downdip direction. During the first 24 hours after the mainshock, aftershocks migrated in both lateral directions with velocities of approximately 2.5 and 5 km/h. At the southern rupture boundary aftershocks cluster around individual subducted seamounts that are related to the downthrusting Juan Fernández Ridge. In the northern part of the rupture area aftershocks separate into an upper cluster (above 25 km depth) and a lower cluster (below 35 km depth). This dual seismic-aseismic transition in downdip direction is also observed in the interseismic period suggesting that it may represent a persistent feature for the Central Chilean subduction zone.

  2. Aftershock seismicity and tectonic setting of the 2015 September 16 Mw 8.3 Illapel earthquake, Central Chile

    NASA Astrophysics Data System (ADS)

    Lange, Dietrich; Geersen, Jacob; Barrientos, Sergio; Moreno, Marcos; Grevemeyer, Ingo; Contreras-Reyes, Eduardo; Kopp, Heidrun

    2016-08-01

    Powerful subduction zone earthquakes rupture thousands of square kilometres along continental margins but at certain locations earthquake rupture terminates. To date, detailed knowledge of the parameters that govern seismic rupture and aftershocks is still incomplete. On 2015 September 16, the Mw 8.3 Illapel earthquake ruptured a 200 km long stretch of the Central Chilean subduction zone, triggering a tsunami and causing significant damage. Here, we analyse the temporal and spatial pattern of the coseismic rupture and aftershocks in relation to the tectonic setting in the earthquake area. Aftershocks cluster around the area of maximum coseismic slip, in particular in lateral and downdip direction. During the first 24 hr after the main shock, aftershocks migrated in both lateral directions with velocities of approximately 2.5 and 5 km hr-1. At the southern rupture boundary, aftershocks cluster around individual subducted seamounts that are related to the downthrusting Juan Fernández Ridge. In the northern part of the rupture area, aftershocks separate into an upper cluster (above 25 km depth) and a lower cluster (below 35 km depth). This dual seismic-aseismic transition in downdip direction is also observed in the interseismic period suggesting that it may represent a persistent feature for the Central Chilean subduction zone.

  3. Study provides data on active plate tectonics in southeast Asia region

    NASA Astrophysics Data System (ADS)

    Wilson, P.; Rais, J.; Reigber, Ch.; Reinhart, E.; Ambrosius, B. A. C.; Le Pichon, X.; Kasser, M.; Suharto, P.; Majid, Dato'Abdul; Yaakub, Dato'Paduka Awang Haji Othman Bin Haji; Almeda, R.; Boonphakdee, C.

    A major geodynamic study has provided significant new information about the location of active plate boundaries in and around Southeast Asia, as well as deformation processes in the Sulawesi region of Indonesia and tectonic activity in the Philippine archipelago. Results also have confirmed the existence of the so-called Sunda Block, which appears to be rotating with respect to adjacent plates.The study, known as the Geodynamics of South and South-East Asia (GEODYSSEA) project, has been a joint venture of the European Commission and the Association of South- East Asian Nations. It began in 1991 and involved a large team of European and Asian scientists and technicians studying the complex geodynamic processes and natural hazards of the region from the Southeast Asia mainland to the Philippines to northern Australia. Earthquakes, volcanic eruptions, tsunamis, and tectonically induced landslides endanger the lives of millions of people in the region, and the tectonic activity behind these natural hazards results from the convergence and collision of the Eurasian, Philippine, and Indo-Australian Plates at relative velocities of up to 10 cm per year.

  4. Supra-subduction zone tectonic setting of the Muslim Bagh Ophiolite, northwestern Pakistan: Insights from geochemistry and petrology

    NASA Astrophysics Data System (ADS)

    Kakar, Mohammad Ishaq; Kerr, Andrew C.; Mahmood, Khalid; Collins, Alan S.; Khan, Mehrab; McDonald, Iain

    2014-08-01

    The geology of the Muslim Bagh area comprises the Indian passive continental margin and suture zone, which is overlain by the Muslim Bagh Ophiolite, Bagh Complex and a Flysch Zone of marine-fluvial successions. The Muslim Bagh Ophiolite has a nearly-complete ophiolite stratigraphy. The mantle sequence of foliated peridotite is mainly harzburgite with minor dunite and contains podiform chromite deposits that grade upwards into transition zone dunite. The mantle rocks (harzburgite/dunite) resulted from large degrees of partial melting of lherzolite and have also been affected by melt-peridotite reaction. The Muslim Bagh crustal section has a cyclic succession of ultramafic-mafic cumulate with dunite at the base, that grades into wehrlite/pyroxenite with gabbros (olivine gabbro, norite and hornblende gabbro) at the top. The sheeted dykes are immature in nature and are rooted in crustal gabbros. The dykes are mainly metamorphosed dolerites, with minor intrusions of plagiogranites. The configuration of the crustal section indicates that the crustal rocks were formed over variable time periods, in pulses, by a low magma supply rate. The whole rock geochemistry of the gabbros, sheeted dykes and the mafic dyke swarm suggests that they formed in a supra-subduction zone tectonic setting in Neo-Tethys during the Late Cretaceous. The dykes of the mafic swarm crosscut both the ophiolite and the metamorphic sole rocks and have a less-marked subduction signature than the other mafic rocks. These dykes were possibly emplaced off-axis and can be interpreted to have been generated in the spinel peridotite stability zone i.e., < 50-60 km, and to have risen through a slab window. The Bagh Complex is an assemblage of Triassic-Cretaceous igneous and sedimentary rocks, containing tholeiitic, N-MORB-like basalts and alkali basalts with OIB-type signatures. Nb-Ta depletion in both basalt types suggests possible contamination from continental fragments incorporated into the opening Tethyan

  5. Chemical and Physical Weathering in a Hot-arid, Tectonically Active Alluvial System (Anza-Borrego Desert, CA)

    NASA Astrophysics Data System (ADS)

    Joo, Y. J.; Elwood Madden, M.; Soreghan, G. S.

    2014-12-01

    Climate and tectonics are primary controls on bedrock erosion, and sediment production, transport, and deposition. Additionally, silicate weathering in tectonically active regions is known to play a significant role in global climate owing to the high rates of physical erosion and exposure of unweathered bedrock to chemical weathering, which removes CO2 from the atmosphere. Therefore, the feedback between weathering and climate is key to understanding climate change through Earth history. This study investigates chemical and physical weathering of alluvial sediments in the Anza-Borrego Desert, California, located in the southern part of the San Andreas Fault System. This setting provides an ideal opportunity to study weathering in a hot and arid climate with mean annual temperatures of ~23 °C and mean annual precipitation of ~160 mm in the basin. Samples were collected along a proximal-to-distal transect of an alluvial-fan system sourced exclusively from Cretaceous tonalite of the Peninsular Range. The single bedrock lithology enables exploration of the effects of other variables — climate, transport distance, drainage area, and tectonics— on the physical and chemical properties of the sediments. Although minimal overall (CIA = 56-61), the degree of chemical weathering increases down transect, dominated by plagioclase dissolution. BET surface area of the mud (<63µm) fraction decreases distally, which is consistent with coarsening grain-size. Chemical alteration and BET surface area both increase in a distal region, within the active Elsinore Fault zone. Extensive fracturing here, together with a more-humid Pleistocene climate likely facilitated in-situ bedrock weathering; specifically, dissolution of primary minerals (e.g. plagioclase), preceding the arid alluvial erosion, transport, and deposition in the Holocene. This study further seeks to disentangle the complex record of the climate and tectonic signals imprinted in these sediments.

  6. UAV's for active tectonics : case example from the Longitudinal Valley and the Chishan Faults (Southern Taiwan)

    NASA Astrophysics Data System (ADS)

    Deffontaines, Benoit; Chang, Kuo-Jen; Chan, Yu-Chang; Chen, Rou-Fei; Hsieh, Yu-Chung

    2015-04-01

    Taiwan is a case example to study active tectonics due to the active NW-SE collision of the Philippine and Eurasian Sea Plates as the whole convergence reaches 10cm/y. In order to decipher the structural active tectonics geometry, we used herein UAV's to get high resolution Digital Terrain Model (DTM) in local active tectonics key areas. Classical photo-interpretation where then developped in order to structurally interprete these data, confirmed by field studies. Two location had first been choosen in order to highlight the contribution of such high resolution DTM in SW Taiwan on the Longitudinal Valley Fault (SE Taiwan) on its southern branch from Pinting to Luyeh terraces (Pinanshan) where UAV's lead to better interprete the location of the outcropping active deformations. Combined with available GPS data and PALSAR interferometry (Deffontaines et Champenois et al., submitted) it is then possible to reconstruct the way of the present deformation in this local area. In the Pinting terraces, If the western branch of the fault correspond to an outcroping thrust fault, the eastern branch act as a a growing active anticline that may be characterized and quantified independantly. The interpretation of the UAV's high resolution DTM data on the Chishan Fault (SW Taiwan) reveals also the geometry of the outcropping active faults complex structural behaviour. If the Chishan Fault act as a thrusting in its northern tip (close to Chishan city), it acts as a right lateral strike-slip fault north of Chaoshan (Kaohsiung city) as described by Deffontaines et al. 2014. Therefore UAV's are a so useful tool to get very high resolution topographic data in Taiwan that are of great help to get the geometry of the active neotectonic structures in Taiwan.

  7. New Insights into the Active Tectonics of Eastern Indonesia from GPS Measurements

    NASA Astrophysics Data System (ADS)

    Susilo, S.; Koulali Idrissi, A.; McClusky, S.; Meilano, I.; Cummins, P. R.; Tregoning, P.; Syafii, A.

    2014-12-01

    The Indonesian archipelago encompasses a wide range of tectonic environments, including island arc volcanism, subduction zones, and arc-continent collision. Many of the details of this tectonic activity are still poorly understood, especially where the Australian continent collides with Indonesia, separating the Sunda Arc in west from that at the Banda Arc in the east. While it seems clear that the Australian plate is subducted under both the Sunda and Banda Arcs, it is not clear what happens along the 1000 km -long stretch in between. The question of just where the plate motion is accommodated is of major importance to assessments of earthquake and tsunami hazard in the region. To help resolve these questions the Geospatial Information Agency of Indonesia has collaborated with the Australian National University and the Bandung Institute of Technology in a GPS campaign spanning much of eastern Indonesia, from Lombok in the west to Alor in the east. We have combined these data with those from previous campaigns, resulting in over 27 campaign and 18 continuous GPS sites being used in the analysis. The improvement in site density allowed us to develop of a more complete description of tectonic activity in this region than has been obtained in previous studies. Our preliminary results suggests that there is a relatively simple transition from subduction at the Java Trench off east Java, to a partitioned convergence along both the Timor Trough and the Flores Thrust in the Nusa Tenggara region.

  8. Tectonic setting of the North Gondwana margin during the Early Ordovician: A comparison of the Ollo de Sapo and Famatina magmatic events

    NASA Astrophysics Data System (ADS)

    Del Greco, Kassandra; Johnston, Stephen T.; Shaw, Jessica

    2016-06-01

    This paper presents a comparison of compiled geochronological and geochemical data from the Ollo de Sapo and Famatina magmatic events. The Ollo de Sapo magmatic sequence is located in northwest Iberia and was emplaced during the early-Ordovician from 495 to 474 Ma. The Famatina Complex is a magmatic sequence located in Northern Argentina that was emplaced during the early- to mid-Ordovician from 483 to 463 Ma. These magmatic events are currently interpreted to have been emplaced in different tectonic settings despite both having occurred along the North Gondwana margin. Geochronological data indicates that these magmatic events occurred contemporaneously over at least 9 m.y. and therefore can provide a snapshot of the northern Gondwana margin during the mid-Ordovician. Major element data indicates that both magmatic suites are calc-alkaline to alkali-calcic and trace element and REE data show magmatic signatures that are indistinguishable. This study highlights the similarity between the Ollo de Sapo and the Famatina magmatic suites and discusses alternative models for their emplacement based on paleomagnetic and paleobiogeographical data. These data indicate that the Ollo de Sapo was likely emplaced in a subduction zone setting, while the Famatina magmatic suite may be of parautochthonous origin to Gondwana, implying that the Pampeanan margin may not have been active during the early- to mid-Ordovician.

  9. Seismicity and active tectonic processes in the ultra-slow spreading Lena Trough, Arctic Ocean

    NASA Astrophysics Data System (ADS)

    Läderach, C.; Schlindwein, V.; Schenke, H.-W.; Jokat, W.

    2011-03-01

    With its remote location in the ice-covered Fram Strait, Lena Trough is a poorly known segment of the global mid-ocean ridge system. It is a prominent member of the ultra-slow spreading mid-ocean ridges but its spreading mechanisms are not well understood. We relocalized teleseismically recorded earthquakes from the past five decades to identify tectonic processes in Lena Trough and the adjacent Spitsbergen Fracture Zone (FZ). During two cruises with RV Polarstern in 2008 and 2009 we deployed seismic arrays on ice floes to record the local seismicity of Lena Trough. We could identify and localize microseismic events which we assume to be present in the entire rift valley. In contrast, our relocalization of teleseismically recorded earthquakes shows an asymmetric epicentre distribution along Lena Trough with earthquakes occurring predominately along the western valley flanks of Lena Trough. In 2009 February/March, several high-magnitude earthquakes peaking in an Mb 6.6 event occurred in an outside-corner setting of the Spitsbergen FZ. This is the strongest earthquake which has ever been recorded in Fram Strait and its location at the outside-corner high of the ultra-slow spreading ridge is exceptional. Comparing the seismicity with the magnetic anomalies and high-resolution multibeam bathymetry, we divide Lena Trough in a symmetrically spreading northern part and an asymmetrically spreading southern part south of the South Lena FZ. We propose that a complex interaction between the former De Geer Megashear zone, which separated Greenland from Svalbard starting at Late Mesozoic/Early Cenozoic times, and the developing rift in the southern Lena Trough resulted an increasing eastward dislocation towards the Spitsbergen FZ between older spreading axes and the recent active spreading axis which we believe to be located west of the bathymetric rift valley flanks in a wide extensional plain.

  10. Sedimentary petrology and geochemistry of siliciclastic rocks from the upper Jurassic Tordillo Formation (Neuquén Basin, western Argentina): Implications for provenance and tectonic setting

    NASA Astrophysics Data System (ADS)

    Spalletti, Luis A.; Queralt, Ignasi; Matheos, Sergio D.; Colombo, Ferrán; Maggi, Jorge

    2008-06-01

    calcalkaline felsic and intermediate composition. However, major element geochemistry is not useful for interpreting the tectonic setting. Discrimination plots based on immobile trace elements, such as Ti, Zr, La, Sc, and Th, show that most data lie in the active continental margin field. Geochemical information is not sufficiently sensitive to differentiate the two different source areas recognized by petrographic and modal analyses of conglomerates and sandstones.

  11. Formation and metasomatism of continental lithospheric mantle in intra-plate and subduction-related tectonic settings

    NASA Astrophysics Data System (ADS)

    Ionov, Dmitri

    2010-05-01

    Our knowledge of the origin and evolution of the continental lithospheric mantle (CLM) remains fragmentary and partly controversial in spite of recent advances in petrologic, geochemical and geophysical studies of the deep Earth and experimental work. Debate continues on a number of essential topics, like relative contributions of partial melting, metasomatism and ‘re-fertilisation' as well as the timing, conditions and tectonic settings of those processes. These topics can be addressed by studies of ultramafic xenoliths in volcanic rocks which arguably provide the least altered samples of modern and ancient CLM. The subcontinental lithosphere is thought to be a mantle region from which melts have been extracted, thus making the lithosphere more refractory. Melting degrees can be estimated from Al contents while the depth of melt extraction can be assessed from Al-Fe (Mg#) relations in unmetasomatized melting residues in comparison with experimental data, e.g. [1]. High silica and opx in the residues may indicate melting in water-rich conditions. High-precision Mg# and Mn for olivine may constrain degrees and conditions of partial melting and/or metasomatism, tectonic settings, modal compositions (e.g. presence of garnet) and equilibration conditions of mantle peridotites [2]. These estimates require both adequate sampling and high-quality major element and modal data; sampling and analytical uncertainties in published work may contribute substantially to chemical heterogeneities (and different origins) inferred for CLM domains [3]. Very fertile peridotite xenolith suites are rare worldwide [3]. They were initially viewed as representing mantle domains that experienced only very small degrees of melt extraction but are attributed by some workers to ‘refertilization' of refractory mantle by percolating asthenospheric melts. Such alternative mechanisms might be valid for some rare hybrid and Fe-enriched peridotites but they fail to comprehensively explain modal

  12. Provenance, diagenesis, tectonic setting and geochemistry of Rudies sandstone (Lower Miocene), Warda Field, Gulf of Suez, Egypt

    NASA Astrophysics Data System (ADS)

    Zaid, Samir M.

    2012-05-01

    The Lower Miocene Rudies sandstones are important oil reservoirs in the southeastern part, Gulf of Suez basin, Egypt. However, their provenance and diagenesis and their impact in reservoir quality, are virtually unknown. Samples from the Warda field, representing the Lower and Middle Rudies, were studied using a combination of petrographic, mineralogical and geochemical techniques. The Lower Rudies sandstones have an average framework composition of Q85F7.2R7.8, and 83% of the quartz grains are monocrystalline. By contrast, the Middle Rudies sandstones are only slightly more quartzose with an average framework composition of Q90F7R3 and 86% of the quartz grains are monocrystalline. Rudies sandstones are mostly quartz arenite with subordinate subarkose and sublithic arenites and their bulk-rock geochemistry support the petrographic results. The modal analysis data of studied samples suggest influence of granitic and metamorphic terrains as the main source rock with a subordinate quartzose recycled sedimentary rocks. The geochemical data interpretation on the basis of discriminate function diagrams reveal the source material was deposited on a passive margin. Textural attributes possibly suggest long-distance transport of grains from the source region and indicates a cratonic or a recycled source. Tectonic setting of Rudies Formation reveals that the lower Rudies sandstones are typically rift sandstone and their deposition constrained the beginning of the faulting, while the middle Rudies sandstones were transported from the far along the rift. Diagenetic features include compaction; dolomite, silica and anhydrite cementation with minor iron-oxide, illite, kaolinite and pyrite cements; dissolution of feldspars, rock fragments. Silica dissolution, grain replacement and carbonate dissolution greatly enhance the petrophysical properties of many sandstone samples.

  13. Cambrian to Lower Ordovician complexes of the Kokchetav Massif and its fringing (Northern Kazakhstan): Structure, age, and tectonic settings

    NASA Astrophysics Data System (ADS)

    Degtyarev, K. E.; Tolmacheva, T. Yu.; Tretyakov, A. A.; Kotov, A. B.; Shatagin, K. N.

    2016-01-01

    A comprehensive study of the Lower Palaeozoic complexes of the Kokchetav Massif and its fringing has been carried out. It has allowed for the first time to discover and investigate in detail the stratified and intrusive complexes of the Cambrian-Early Ordovician. Fossil findings and isotope geochronology permitted the determination of their ages. The tectonic position and internal structures of those complexes have also been defined and their chemical features have been analyzed as well. The obtained data allowed us to put forward a model of the geodynamic evolution of Northern Kazakhstan in the Late Ediacaran-Earliest Ordovician. The accumulation of the oldest Ediacaran to Earliest Cambrian siliciclastics and carbonates confined to the Kokchetav Massif and its fringing occurred in a shallow shelf environment prior to its collision with the Neoproterozoic Daut island arc: complexes of the latter have been found in the northeast of the studied area. The Early Cambrian subduction of the Kokchetav Massif under the Daut island arc, their following collision and exhumation of HP complexes led to the formation of rugged ground topography, promoting deposition of siliceous-clastic and coarse clastic units during the Middle to early Late Cambrian. Those sediments were mainly sourced from eroded metamorphic complexes of the Kokchetav Massif basement. At the end of the Late Cambrian to the Early Ordovician within the boundaries of the massif with the Precambrian crust, volcanogenic and volcano-sedimentary units along with gabbros and granites with intraplate affinities were formed. Simultaneously in the surrounding zones, which represent relics of basins with oceanic crust, N-MORB- and E-MORB-type ophiolites were developed. These complexes originated under extensional settings occurred in the majority of the Caledonides of Kazakhstan and Northern Tian Shan. In the Early Floian Stage (Early Ordovician) older heterogeneous complexes were overlain by relatively monotonous

  14. Rates and Mechanisms of Solidification in Large Magma Bodies: Implications for Melt Extraction in all Tectonic Settings

    NASA Astrophysics Data System (ADS)

    VanTongeren, J. A.

    2013-12-01

    As is observed in both experiment and theory, in the absence of hydrothermal convection, the majority of magma chamber heat loss occurs via conduction through the roof of the intrusion and into the cold country rock above. The formation of an upper solidification front (or Upper Border Series, UBS), recorded in the rocks both geochemically and texturally, is a natural outcome of the progression of the solidification front from the cold roof to the hot center of the magma chamber. There are, however, a few unique layered mafic intrusions for which little or no UBS exists. In this study, I examine the thermal evolution and crystallization rates of several classic layered intrusions as it is recorded in the extent of the preserved UBS. For those intrusions that have experienced crystallization at the roof, such as the Skaergaard Intrusion, the development of a UBS reduces the temperature gradient at the roof and effectively slows the rate of heat loss from the main magma body. However, for those intrusions that do not have an UBS, such as the Bushveld Complex, the cooling rate is controlled only by the maximum rate of conductive heat loss through the overlying roof rocks, which decreases with time. The implications are two-fold: (1) The relative thickness of the UBS in large intrusions may be the key to quantifying their cooling and solidification rates; and (2) The nature of the magma mush zone near the roof of an intrusion may depend principally on the long-term thermal evolution of the magma body. Particularly at the end stages of crystallization, when the liquids are likely to be highly evolved and high viscosities may inhibit convection, intrusions lacking a well-defined UBS may provide important insights into the mechanics of crystal-liquid separation, melt extraction, and compaction in felsic plutons as well as mafic intrusions. These results are important for long-lived (>500 kyr) or repeatedly replenished magma chambers in all tectonic settings.

  15. Geomorphic signatures of active tectonics in the Trans-Yamuna segment of the western Doon valley, northwest Himalaya, India

    NASA Astrophysics Data System (ADS)

    Philip, George; Sah, Madho P.

    Being involved in the late orogenic movements of the sub-Himalaya, the Doon valley and its Quaternary formations have received considerable attention from Earth scientists in the study of active tectonics and paleoseismic events. Study of aerial photographs and satellite data, and selected field checks not only confirmed neotectonic features already reported by various authors but also revealed the presence of more such features. In response to active tectonics, these features have affected very young terraces and Quaternary sediments in the Trans-Yamuna segment of the Doon valley in the western sub-Himalaya. In the present study, an attempt has been made to understand the neotectonic implications of these movements on landforms in and around Sataun-Sirmuri Tal. Ground evidence indicates that the area has experienced at least three major tectonic impulses since the generation of the Main Boundary Thrust. The major tectonic disturbances are most likely due to co-seismic activity along the ongoing Himalayan tectonic processes. In this paper, we discuss some of the strong geomorphic signatures, such as lineament and active fault traces, pressure ridges, sag ponds, alluvial fans, river terraces and finally landslides, which are indicative of active tectonics in this area. On the basis of the present-day geomorphic configuration of this sub-Himalayan basin, a possible evolutionary history is also presented.

  16. Late cretaceous extensional tectonics and associated igneous activity on the northern margin of the Gulf of Mexico Basin

    NASA Technical Reports Server (NTRS)

    Bowen, R. L.; Sundeen, D. A.

    1985-01-01

    Major, dominantly compressional, orogenic episodes (Taconic, Acadian, Alleghenian) affected eastern North America during the Paleozoic. During the Mesozoic, in contrast, this same region was principally affected by epeirogenic and extensional tectonism; one episode of comparatively more intense tectonic activity involving extensive faulting, uplift, sedimentation, intrusion and effusion produced the Newark Series of eposits and fault block phenomena. This event, termed the Palisades Disturbance, took place during the Late Triassic - Earliest Jurassic. The authors document a comparable extensional tectonic-igneous event occurring during the Late Cretaceous (Early Gulfian; Cenomanian-Santonian) along the southern margin of the cratonic platform from Arkansas to Georgia.

  17. Spatial analysis of Budovar stream catchment (Srem Loess Plateau, Serbia) in a tectonically active region

    NASA Astrophysics Data System (ADS)

    Jovanovic, Mladjen; Rvovic, Ivan; Sorak, Rada; Petrovic, Milos

    2016-04-01

    Budovar is the far longest stream on Srem Loess Plateau, with a length of a 52 km, and catchment area of 245 km2. Budovar stream drains a quite complex landscape in terms of generally flat loess plateau, with elevations decreasing gradually southeastward - from 213 m at slopes of Fru\\vska Gora Mountain to 70,9 m at the confluence with Danube river. The youngest (Pleistocene/Holocene) sedimentary formations in the catchment vary from slope loess on Fru\\vska Gora Mtn. in upper part, through typical plateau loess in middle part, and the finest bog-sediments in tectonic depressions in lower part. These deposits lie over the bog-lake-terrestrial sediments with thickness over 100 m. According the geodetic measurements, uplift of Fru\\vska Gora Mtn., which has been the strongest during the Middle Pleistocene, is still present, with rates of up to 1 mm/y in contrast of general uplift of the area, subsidence is recorded in two distinct parts of the catchment. Spatial analysis is done using a DEM, generated in ArcGIS 10.0 from the elevation points, 10 m contours and stream coverage available in 1:25.000 topographical maps. Both longitudinal and cross-section profiles of the valley reflect the influence of tectonic distortions and climatic fluctuations. Valleys in Budovar catchment have composite character - the valleys cross-sections vary from deep incised V-shape, reversed trapezoid shape and completely flat valleys in tectonic depressions. Moreover, there is almost no correlation between the shape of cross-sectional profiles and the direction of curvature of the main valley's long axis (left/right or straight), suggesting that the tectonic activity has the key role in shaping. The width of valleys in Budovar catchment area is in sharp contrast with present stream discharge, which suggests strong climate fluctuations since Upper Pleistocene. The longitudinal profiles also shows signs of kickpoints and some short reaches with increasing elevation in the flow direction. Key

  18. The fold-and-thrust tectonic setting of the Mesozoic carbonate units of Eastern Sardinia: insights from 3D (2D + t) modelling

    NASA Astrophysics Data System (ADS)

    Arragoni, Simone; Cianfarra, Paola; Maggi, Matteo; Salvini, Francesco

    2015-04-01

    Present-day Eastern Sardinia structural setting was mainly determined by Cenozoic strike-slip-to-oblique faulting in the Tacchi and Golfo di Orosei regions, where Mesozoic shallow water carbonates crop out (Costamagna and Barca, 2004 and references therein). These structures are interpreted as the effects of the rotation of the Sardinia-Corsica block during Oligocene and the successive opening of the Tyrrhenian sea starting from lower Miocene (Oggiano et al., 2009 and references therein). New structural data indicate the presence of dip-slip compressive tectonics and thrusting affecting the Mesozoic carbonates and involving the underlying Paleozoic basement. This event shows a westward vergence (top-to-the-W) and is cut by later strike-slip faults. The age of this tectonics is constrained between Eocene (Lutetian rocks involved) and Oligo-Miocene (post-dated by the strike-slip tectonic event). The integration between these new structural observations and the available geological and geophysical datasets allowed to construct a balanced and admissible geological cross section in order to study the tectonic evolution of eastern Sardinia before the opening of the Tyrrhenian basin. The orientation of the section is parallel to the direction of the tectonic transport, that is WSW-ENE. The balanced cross-section has been modelled with the "Forctre" software in order to get a 3D (2D + t) evolutionary model and check its admissibility through time. The final section shows a thin-skin geometry (flats sectors prevailing over ramps) and is composed of two main tectonic slices deeply involving the Paleozoic basement and secondary thrusting affecting the Mesozoic carbonate units. These are characterized by "younger-on-older" flat-over-flat tectonics evidenced by Cretaceous-over-Jurassic thrusting. Similar geometries have been described also in the Latium-Abruzzi sector of the Southern Apennines. Costamagna L.G. & Barca S. 2004. Stratigrafia, analisi di facies, paleogeografia ed

  19. Paleoseismic and geomorphologic evidence of recent tectonic activity of the Pozohondo Fault (Betic Cordillera, SE Spain)

    USGS Publications Warehouse

    Rodríguez-Pascua, M.A.; Pérez-López, R.; Garduño-Monroy, V.H.; Giner-Robles, J.L.; Silva, P.G.; Perucha-Atienza, M.A.; Hernández-Madrigal, V.M.; Bischoff, J.

    2012-01-01

    Instrumental and historical seismicity in the Albacete province (External Prebetic Zone) has been scarcely recorded. However, major strike-slip faults showing NW-SE trending provide geomorphologic and paleoseismic evidence of recent tectonic activity (Late Pleistocene to Present). Moreover, these faults are consistently well oriented under the present stress tensor and therefore, they can trigger earthquakes of magnitude greater than M6, according to the lengths of surface ruptures and active segments recognized in fieldwork. Present landscape nearby the village of Hellin (SE of Albacete) is determined by the recent activity of the Pozohondo Fault (FPH), a NW-SE right-lateral fault with 90 km in length. In this study, we have calculated the Late Quaternary tectonic sliprate of the FPH from geomorphological, sedimentological, archaeoseimological, and paleoseismological approaches. All of these data suggest that the FPH runs with a minimum slip-rate of 0.1 mm/yr during the last 100 kyrs (Upper Pleistocene-Holocene). In addition, we have recognized the last two major paleoearthquakes associated to this fault. Magnitudes of these paleoearthquakes were gretarer than M6 and their recurrence intervals ranged from 6600 to 8600 yrs for the seismic cycle of FPH. The last earthquake was dated between the 1st and 6th centuries, though two earthquakes could be interpreted in this wide time interval, one at the FPH and other from a far field source. Results obtained here, suggest an increasing of the tectonic activity of the Pozohondo Fault during the last 10,000 yrs.

  20. Sediment composition of big Chinese and Indochinese rivers reflects geology of their source, not tectonic setting of their sink.

    NASA Astrophysics Data System (ADS)

    Garzanti, Eduardo; Andò, Sergio; Limonta, Mara; Nie, Junsheng; Resentini, Alberto; Vezzoli, Giovanni; Wang, Jiangang; Yang, Shouye

    2016-04-01

    There are several reasons why the tectonic setting of a sedimentary basin cannot be inferred from the composition of its sedimentary fill. One is that sediments can, and quite often are transported for thousands of kilometers from sources uplifted by certain tectonic processes to subsident basins created by totally different tectonic processes. A classical case is the Amazon River, carrying detritus from the Andean Cordillera to the Atlantic passive margin on the opposite side of South America (Franzinelli and Potter, 1983; Dickinson, 1988). Similar is the case of major rivers in China and Indochina, sourced in Tibetan orogenic highlands and reaching the Chinese passive margin or the back-arc/pull-apart Andaman Sea. The Huang He (Yellow River), the most sediment-laden river in the world, delivers annually to the Bohai Sea 1 billion tons of litho-feldspatho-quartzose sedimentaclastic/metamorphiclastic sediments with moderately rich, amphibole-epidote-garnet suites including apatite and zircon (Nie et al., 2015). The Changjiang (Yangtze) River, the fourth longest on Earth and the largest in Eurasia, carries to the East China Sea litho-feldspatho-quartzose sedimentaclastic/metamorphiclastic sand with moderately poor, amphibole-epidote suites including clinopyroxene and garnet (Vezzoli et al., 2016). The Ayeyarwadi (Irrawaddy) River, ranking among the five major rivers in the world for its annual load of 0.4 billion tons, carries to the Andaman Sea litho-feldspatho-quartzose metamorphiclastic/sedimentaclastic sand with moderately rich, amphibole-epidote suites including garnet and clinopyroxene (Garzanti et al., 2013). Detrital modes in these three very big river basins are thus similar, and would plot in the "Recycled Orogen" field of Dickinson (1985) rather than in the "Continental Block" or "Magmatic Arc" fields. The orogenic signature acquired in mountainous headwaters is carried all the way to the mouth, and even after long-distance transport across wide

  1. Magma-tectonic interactions in an area of active extension; a review of recent observations, models and interpretations from Iceland

    NASA Astrophysics Data System (ADS)

    Pedersen, Rikke; Sigmundsson, Freysteinn; Drouin, Vincent; Rafn Heimisson, Elías; Parks, Michelle; Dumont, Stéphanie; Árnadóttir, Þóra; Masterlark, Timothy; Ófeigsson, Benedíkt G.; Jónsdóttir, Kristín; Hooper, Andrew

    2016-04-01

    The geological setting of Iceland provides rich opportunities of studying magma-tectonic interactions, as it constitutes Earth's largest part of the mid-oceanic ridge system exposed above sea level. A series of volcanic and seismic zones accommodate the ~2 cm/year spreading between the North-American and Eurasian plates, and the Icelandic hot-spot conveniently provides the means of exposing this oceanic crust-forming setting above sea-level. Both extinct and active plumbing system structures can be studied in Iceland, as the deeply eroded tertiary areas provide views into the structures of extinct volcanic systems, and active processes can be inferred on in the many active volcanic systems. A variety of volcanic and tectonic processes cause the Icelandic crust to deform continuously, and the availability of contemporaneous measurements of crustal deformation and seismicity provide a powerful data set, when trying to obtain insight into the processes working at depth, such as magma migration through the uppermost lithosphere, magma induced host rock deformation and volcanic eruption locations and styles. The inferences geodetic and seismic datasets allow on the active plate spreading processes and subsurface magma movements in Iceland will be reviewed, in particular in relation to the Northern Volcanic Zone (NVZ). There the three phases of a rifting cycle (rifting, post-rifting, inter-rifting) have been observed. The NVZ is an extensional rift segment, bounded to the south by the Icelandic mantle plume, and to the north by the Tjörnes transform zone. The NVZ has typically been divided into five partly overlapping en-echelon fissure swarms, each with a central main volcanic production area. Most recently, additional insight into controlling factors during active rifting has been provided by the Bárðarbunga activity in 2014-2015 that included a major rifting event, the largest effusive eruption in Iceland since 1783, and a gradual caldera collapse. It is evident

  2. Soil radon measurements as a potential tracer of tectonic and volcanic activity

    NASA Astrophysics Data System (ADS)

    Neri, Marco; Ferrera, Elisabetta; Giammanco, Salvatore; Currenti, Gilda; Cirrincione, Rosolino; Patanè, Giuseppe; Zanon, Vittorio

    2016-04-01

    In Earth Sciences there is a growing interest in studies concerning soil-radon activity, due to its potential as a tracer of numerous natural phenomena. Our work marks an advance in the comprehension of the interplay between tectonic activity, volcanic eruptions and gas release through faults. Soil-radon measurements, acquired on Mt. Etna volcano in 2009–2011, were analyzed. Our radon probe is sensitive to changes in both volcanic and seismic activity. Radon data were reviewed in light of the meteorological parameters. Soil samples were analyzed to characterize their uranium content. All data have been summarized in a physical model which identifies the radon sources, highlights the mechanism of radon transport and envisages how such a mechanism may change as a consequence of seismicity and volcanic events. In the NE of Etna, radon is released mainly from a depth of <1400 m, with an ascent speed of >50 m/day. Three periods of anomalous gas release were found (February 2010, January and February 2011). The trigger of the first anomaly was tectonic, while the second and third had a volcanic origin. These results mark a significant step towards a better understanding of the endogenous mechanisms that cause changes in soil-radon emission at active volcanoes.

  3. Soil radon measurements as a potential tracer of tectonic and volcanic activity.

    PubMed

    Neri, Marco; Ferrera, Elisabetta; Giammanco, Salvatore; Currenti, Gilda; Cirrincione, Rosolino; Patanè, Giuseppe; Zanon, Vittorio

    2016-01-01

    In Earth Sciences there is a growing interest in studies concerning soil-radon activity, due to its potential as a tracer of numerous natural phenomena. Our work marks an advance in the comprehension of the interplay between tectonic activity, volcanic eruptions and gas release through faults. Soil-radon measurements, acquired on Mt. Etna volcano in 2009-2011, were analyzed. Our radon probe is sensitive to changes in both volcanic and seismic activity. Radon data were reviewed in light of the meteorological parameters. Soil samples were analyzed to characterize their uranium content. All data have been summarized in a physical model which identifies the radon sources, highlights the mechanism of radon transport and envisages how such a mechanism may change as a consequence of seismicity and volcanic events. In the NE of Etna, radon is released mainly from a depth of <1400 m, with an ascent speed of >50 m/day. Three periods of anomalous gas release were found (February 2010, January and February 2011). The trigger of the first anomaly was tectonic, while the second and third had a volcanic origin. These results mark a significant step towards a better understanding of the endogenous mechanisms that cause changes in soil-radon emission at active volcanoes. PMID:27079264

  4. Soil radon measurements as a potential tracer of tectonic and volcanic activity

    PubMed Central

    Neri, Marco; Ferrera, Elisabetta; Giammanco, Salvatore; Currenti, Gilda; Cirrincione, Rosolino; Patanè, Giuseppe; Zanon, Vittorio

    2016-01-01

    In Earth Sciences there is a growing interest in studies concerning soil-radon activity, due to its potential as a tracer of numerous natural phenomena. Our work marks an advance in the comprehension of the interplay between tectonic activity, volcanic eruptions and gas release through faults. Soil-radon measurements, acquired on Mt. Etna volcano in 2009–2011, were analyzed. Our radon probe is sensitive to changes in both volcanic and seismic activity. Radon data were reviewed in light of the meteorological parameters. Soil samples were analyzed to characterize their uranium content. All data have been summarized in a physical model which identifies the radon sources, highlights the mechanism of radon transport and envisages how such a mechanism may change as a consequence of seismicity and volcanic events. In the NE of Etna, radon is released mainly from a depth of <1400 m, with an ascent speed of >50 m/day. Three periods of anomalous gas release were found (February 2010, January and February 2011). The trigger of the first anomaly was tectonic, while the second and third had a volcanic origin. These results mark a significant step towards a better understanding of the endogenous mechanisms that cause changes in soil-radon emission at active volcanoes. PMID:27079264

  5. Provenance and tectonic setting of Late Carboniferous clastic rocks in West Junggar, Xinjiang, China: A case from the Hala-alat Mountains

    NASA Astrophysics Data System (ADS)

    Tao, Huifei; Wang, Qingchen; Yang, Xiaofa; Jiang, Lin

    2013-03-01

    The Late Carboniferous palaeo-tectonic setting of the West Junggar region is comprised of arcs alternating with basins. Geochemical analysis of the sedimentary rocks associated with these arc-related basins was conducted to better constrain the provenance and tectonic setting.Major and trace element geochemistry data of Late Carboniferous mudstones and sandstones in the Hala-alat Mountains suggest that these sedimentary rocks and their source areas are characterized by the following four features: (1) sediments experienced a simple recycling process; (2) a low degree weathering conditions in the source areas; (3) compositional immature of the sedimentary rocks; (4) dominated by intermediate to felsic provenance, with a few intermediate to mafic sediments. Integrated with the palaeo-flow data and previous authors' works, a fore-arc basin model is proposed for the tectonic setting of the sedimentary rocks. The Sawur arc is the primary provenance and supplies the major intermediate to felsic detrital fragments. The Bozchekul-Chingiz arc and Kexia oceanic island arc are the other two secondary sources.

  6. Analogue experiments applied to active tectonics studies: the case of seismogenic normal faults

    NASA Astrophysics Data System (ADS)

    Seno, S.; Bonini, L.; Toscani, G.

    2010-12-01

    Lithosphere can be divided into three main zones as a function of increasing depth: an aseismic updip zone, the seismogenic zone and a deep aseismic zone. Identifying the location of these zones is a key goal to understand how a specific seismogenic fault works. The evaluation of the seismogenic structures potential in tectonically active regions needs an accurate knowledge of the geometries and kinematic of the faults. In many cases, large seismogenic faults are not clearly and unambiguously expressed at the surface, whereas in other regions with higher deformation rates a clear geological surface evidence is often associated with large earthquakes. Therefore, the characterization of the seismogenic faults and of their mutual interactions it is not always straightforward; in this case, analogue modeling can provide an independent and useful tool for the interpretation of the surface geological data. Analogue modeling applied to earthquake geology is a quite innovative technique: when combined with other datasets (e.g.: seismic tomography, seismic profiles, well-logging data, field geology, morphotectonic and palaeo-seismological data) it can provide significant insights on the long term (i.e. Quaternary) evolution of a seismogenic fault. We carried out a set of analogue models at 1 : 100,000 scale that reproduce in 2D a normal fault with a relatively low dip angle (45°-50°). In our experimental approach different materials have been used to simulate the three main zones in which the lithosphere is separated. Dry sand and wet clay simulate different mechanical behaviour of rocks during seismic cycle. The dry sand, with its negligible cohesion and ductility, represents brittle rocks that deformed by localized faulting during earthquakes. Wet clay, with its slightly greater cohesion and ductility, mimics aseismic updip zone. Glass microbeads simulate aseismic plastic zone. Preliminary results are highlighting a mutual control among the three analogue materials

  7. Relationship between observed upper mantle structures and recent tectonic activity across the Southeastern United States

    NASA Astrophysics Data System (ADS)

    Biryol, C. Berk; Wagner, Lara S.; Fischer, Karen M.; Hawman, Robert B.

    2016-05-01

    The lithospheric structure of the Southeastern United States is a product of earlier episodes of continental collision and breakup. The region is located in the interior of the North American Plate, away from active plate margins. However, there is ongoing tectonism in the region with multiple zones of seismicity, uplifting arches, and Cenozoic intraplate volcanism. The mechanisms controlling this activity and the state of stress remain enigmatic. Two important factors are plate strength and preexisting, inherited structures. Here we present new tomographic images of the upper mantle beneath the Southeastern United States, revealing large-scale structural variations in the upper mantle. Examples include the relatively thick lithospheric mantle of stable North America that abruptly thins beneath the Paleozoic Appalachian orogeny, and the slow upper mantle of the Proterozoic Reelfoot rift. Our results also indicate fast seismic velocity patterns that can be interpreted as ongoing lithospheric foundering. This provides a viable explanation for seismicity, uplifting, and young intraplate volcanism. We postulate that not only tectonic inheritance but also continuing lithospheric foundering may control the ongoing activity of the region long after it became a passive margin. Based on distinct variations in the geometry and thickness of the lithospheric mantle and foundered lithosphere, we propose that piecemeal delamination has occurred beneath the region throughout the Cenozoic, removing a significant amount of reworked/deformed mantle lithosphere. Ongoing lithospheric foundering beneath the eastern margin of stable North America explains significant variations in thickness of lithospheric mantle across the former Grenville deformation front.

  8. Active tectonics and Quaternary landscape evolution across the western Panama block, Costa Rica, Central America

    NASA Astrophysics Data System (ADS)

    Marshall, Jeffrey Scott

    Three aspects of active tectonism are examined across central Costa Rica: (1) fault kinematics; (2) volcanic arc retreat; and (3) spatially variable coastal uplift. Diffuse faulting along the Central Costa Rica Deformed Belt (CCRDB) defines the western margin of the Panama block and aligns with the rough-smooth boundary (RSB) on the subducting Cocos plate. Sub-horizontal subduction of rough, hotspot thickened crust (Cocos Ridge and seamounts) shifts active shortening into the volcanic arc along the CCRDB. Mesoscale faults express variable kinematics across three domains: transtension in the forearc, transcurrent motion across the volcanic arc, and transpression in the back arc. Fault kinematics agree with seismicity and GPS data, and isotopic ages confirm that faulting postdates the late Neogene onset of shallow subduction. Stratigraphic correlation augmented by 40Ar/39Ar dating constrain the timing of Quaternary arc migration from the Neogene Aguacate range to the modern Cordillera Central. The Valle Central basin, between the cordilleras, filled with thick sequences of lavas, pyroclastic flows, and lahars. Middle Pleistocene drainage capture across the Aguacate arc linked the Valle Central with the Pacific slope and ash flows descended onto the coastal Orotina debris fan. Arc retreat reflects slab shallowing and enhanced tectonic erosion as rough crust entered the subduction zone. Differing subduction parameters across the RSB (crustal age, slab dip, roughness) produce marked contrasts in coastal tectonism. Varying uplift rates across coastal faults reflect sub-horizontal subduction of seamount roughness. Three groups (I--III) of fluvial terraces are correlated along the coast by isotopic ages and geomorphic characteristics. Base level fluctuations and terrace genesis reflect interaction between eustatic sea level and spatially variable rock uplift. Low uplift rates (north of RSB), yield one surface per terrace group, whereas moderate rates (south of RSB

  9. Tectonic and Structural Controls of Geothermal Activity in the Great Basin Region, Western USA

    NASA Astrophysics Data System (ADS)

    Faulds, J. E.; Hinz, N.; Kreemer, C. W.

    2012-12-01

    We are conducting a thorough inventory of structural settings of geothermal systems (>400 total) in the extensional to transtensional Great Basin region of the western USA. Most of the geothermal systems in this region are not related to upper crustal magmatism and thus regional tectonic and local structural controls are the most critical factors controlling the locations of the geothermal activity. A system of NW-striking dextral faults known as the Walker Lane accommodates ~20% of the North American-Pacific plate motion in the western Great Basin and is intimately linked to N- to NNE-striking normal fault systems throughout the region. Overall, geothermal systems are concentrated in areas with the highest strain rates within or proximal to the eastern and western margins of the Great Basin, with the high temperature systems clustering in transtensional areas of highest strain rate in the northwestern Great Basin. Enhanced extension in the northwestern Great Basin probably results from the northwestward termination of the Walker Lane and the concomitant transfer of dextral shear into west-northwest directed extension, thus producing a broad transtensional region. The capacity of geothermal power plants also correlates with strain rates, with the largest (hundreds of megawatts) along the Walker Lane or San Andreas fault system, where strain rates range from 10-100 nanostrain/yr to 1,000 nanostrain/yr, respectively. Lesser systems (tens of megawatts) reside in the Basin and Range (outside the Walker Lane), where local strain rates are typically < 10 nanostrain/yr. Of the 250+ geothermal fields catalogued, step-overs or relay ramps in normal fault zones serve as the most favorable setting, hosting ~32% of the systems. Such areas have multiple, overlapping fault strands, increased fracture density, and thus enhanced permeability. Other common settings include a) intersections between normal faults and strike-slip or oblique-slip faults (27%), where multiple minor

  10. An Integrated Geospatial System for earthquake precursors assessment in Vrancea tectonic active zone in Romania

    NASA Astrophysics Data System (ADS)

    Zoran, Maria A.; Savastru, Roxana S.; Savastru, Dan M.

    2015-10-01

    With the development of space-based technologies to measure surface geophysical parameters and deformation at the boundaries of tectonic plates and large faults, earthquake science has entered a new era. Using time series satellite data for earthquake prediction, it is possible to pursue the behaviors of earthquake precursors in the future and to announce early warnings when the differences between the predicted value and the observed value exceed the pre-define threshold value. Starting with almost one week prior to a moderate or strong earthquake a transient thermal infrared rise in LST of several Celsius degrees (oC) and the increased OLR values higher than the normal have been recorded around epicentral areas, function of the magnitude and focal depth, which disappeared after the main shock. Also are recorded associated geomagnetic and ionospheric distrurbances. Vrancea tectonic active zone in Romania is characterized by a high seismic hazard in European- Mediterranean region, being responsible of strong or moderate intermediate depth and normal earthquakes generation on a confined epicentral area. Based on recorded geophysical parameters anomalies was developed an integrated geospatial system for earthquake precursors assessment in Vrancea active seismic zone. This system integrates derived from time series MODIS Terra/Aqua, NOAA-AVHRR, ASTER, Landsat TM/ETM satellite data multi geophysical parameters (land surface temperature -LST, outgoing long-wave radiation- OLR, and mean air temperature- AT as well as geomagnetic and ionospheric data in synergy with in-situ data for surveillance and forecasting of seismic events.

  11. Linkages of Erosion, Tectonics, and Climate in a Glacial Setting: Lessons Learned in Alaska's St. Elias Orogen

    NASA Astrophysics Data System (ADS)

    Spotila, J. A.; Berger, A. L.

    2009-12-01

    A microplate collision in the southern Alaskan syntaxis provides useful analogies and lessons for the erosive-tectonic coupling that occur at Earth’s other great orogens. The St. Elias orogen is a relatively small collision produced by impingement of the Yakutat terrane in the transform-subduction crook of the northernmost Pacific-North America plate boundary. Due to convergence rates comparable to those in the Himalaya and a severe maritime glacial climate, deformation and rock uplift in this orogen rival Earth’s most extreme tectonic environments. Ongoing multidisciplinary investigations have documented several key phenomena that are relevant to orogenic processes worldwide. Previously obtained bedrock thermochronometry has revealed that glaciers exert an important control on tectonic crustal efflux. Long-term denudation is focused where mean Quaternary glacial ELA intersects the windward flank of the orogen. Quaternary enhancement of glaciation also appears to have dramatically accelerated denudation and forced a reorganization of orogenic wedge architecture. These results imply that glaciers are more significant to orogenic belts than implied by the topographic “buzz saw” hypothesis, in that they actually dictate long-term patterns of strain and mass transfer at the orogen-scale. New data refine the spatial and temporal patterns of exhumation in the orogen and enable more robust assessment of flux steady-state, or how exhumation has kept pace with tectonic crustal influx. Results suggest that, despite the presence of such an efficient erosive system, a component of tectonic influx is likely accommodated by subduction or lateral advection via intraplate transform faults. We suggest that a continuous dextral fault connects the mapped Totschunda-Denali and Fairweather faults, enabling a significant component of plate convergence to bypass the orogen. Finally, the refined pattern of exhumation sheds light onto the possible existence of tectonic

  12. Relationship between the regional tectonic activity and crustal structure in the eastern Tibetan plateau discovered by gravity anomaly

    NASA Astrophysics Data System (ADS)

    Xu, Xiao; Gao, Rui; Guo, Xiaoyu

    2016-04-01

    The eastern Tibetan plateau has been getting more and more attention because it combines active faults, uplifting, and large earthquakes together in a high-population region. Based on the previous researches, the most of Cenozoic tectonic activities were related to the regional structure of the local blocks within the crustal scale. Thus, a better understanding of the crustal structure of the regional tectonic blocks is an important topic for further study. In this paper, we combined the simple Bouguer gravity anomaly with the Moho depths from previous studies to investigate the crustal structure in this area. To highlight the crustal structures, the gravity anomaly caused by the Moho relief has been reduced by forward modeling calculations. A total horizontal derivative (THD) had been applied on the gravity residuals. The results indicated that the crustal gravity residual is compatible with the topography and the geological settings of the regional blocks, including the Sichuan basin, the Chuxiong basin, the Xiaojiang fault, and the Jinhe fault, as well as the Longmenshan fault zone. The THD emphasized the west margin of Yangtze block, i.e., the Longriba fault zone and the Xiaojiang fault cut through the Yangtze block. The checkboard pattern of the gravity residual in the Songpan-Garze fold belt and Chuandian fragment shows that the crust is undergoing a southward and SE-directed extrusion, which is coincident with the flowing direction indicated from the GPS measurements. By integrating the interpretations, the stepwise extensional mechanism of the eastern Tibetan plateau is supported by the southeastward crustal deformation, and the extrusion of Chuandian fragment is achieved by Xianshuihe fault.

  13. Micro-plate tectonics and kinematics in Northeast Asia inferred from a dense set of GPS observations

    NASA Astrophysics Data System (ADS)

    Jin, Shuanggen; Park, Pil-Ho; Zhu, Wenyao

    2007-05-01

    The plate tectonics of Northeast Asia are very complex with diffuse and sparse seismicity in the broad plate deformation zones embedded by a number of micro-plates, particularly the controversial Amurian plate. Now the increasingly dense GPS networks in this area provide an important tool to investigate plate tectonic kinematics and to identify the approximate plate tectonic geometries. In this paper, we have processed GPS data (1998-2005) collected by an extensive GPS network (China and South Korea) with more than 85 continuous sites and about 1000 campaign GPS stations. The kinematics of Northeast Asia is studied by modeling GPS-derived velocities with rigid block rotations and elastic deformation. We find that the deformation in Northeast Asia can be well described by a number of rotating blocks, which are independent of the Eurasian plate motion with statistical significance above the 99% confidence level. The tectonic boundary between the North China and Amuria plates is the Yin Shan-Yan Shan Mountain belts with about 2.4 mm/yr extension. Along the boundary between North China and South China, the Qinling-Dabie fault is moving left laterally at about 3.1 mm/yr. The Amuria and South Korea blocks are extending at about 1.8 mm/yr. The Baikal Rift between the Amurian and Eurasian plates is spreading at about 3.0 mm/yr. The 9-17 mm/yr relative motion between the Amuria and Okhotsk blocks is accommodated at the East Sea-Japan trench zone. Localized deformation near the Qinling-Dabie fault and Yin Shan-Yan Shan Mountain belts may be elastic strain accumulation due to interseismic locking of faults.

  14. Banded iron-formations of late Proterozoic age in the central eastern desert, Egypt: geology and tectonic setting.

    USGS Publications Warehouse

    Sims, P.K.; James, H.L.

    1984-01-01

    Iron-formation occurs as stratigraphic units within a layered andesite-basalt sequence. The sequence is metamorphosed to greenschist facies, intruded by syntectonic granodiorite and post-tectonic granite, and complexly deformed and grossly fragmented; the rocks are allochthonous along thrust faults. The iron deposits are chemical precipitates, accumulated during lulls in volcanism, apparently in an intraoceanic island-arc environment. The deposits are of the Algoma type of iron-formation.-G.J.N.

  15. Simulation of active tectonic processes for a convecting mantle with moving continents

    USGS Publications Warehouse

    Trubitsyn, V.; Kaban, M.; Mooney, W.; Reigber, C.; Schwintzer, P.

    2006-01-01

    Numerical models are presented that simulate several active tectonic processes. These models include a continent that is thermally and mechanically coupled with viscous mantle flow. The assumption of rigid continents allows use of solid body equations to describe the continents' motion and to calculate their velocities. The starting point is a quasi-steady state model of mantle convection with temperature/ pressure-dependent viscosity. After placing a continent on top of the mantle, the convection pattern changes. The mantle flow subsequently passes through several stages, eventually resembling the mantle structure under present-day continents: (a) Extension tectonics and marginal basins form on boundary of a continent approaching to subduction zone, roll back of subduction takes place in front of moving continent; (b) The continent reaches the subduction zone, the extension regime at the continental edge is replaced by strong compression. The roll back of the subduction zone still continues after closure of the marginal basin and the continent moves towards the upwelling. As a result the ocean becomes non-symmetric and (c) The continent overrides the upwelling and subduction in its classical form stops. The third stage appears only in the upper mantle model with localized upwellings. ?? 2006 The Authors Journal compilation ?? 2006 RAS.

  16. Beyond surface heat flow: An example from a tectonically active sedimentary basin

    NASA Astrophysics Data System (ADS)

    Armstrong, Phillip A.; Chapman, David S.

    1998-02-01

    Thermal anomalies that have important geodynamic implications may not always be recognizable in present-day surface heat-flow patterns. The masking occurs because surface heat flow responds to mantle heat, crustal radioactivity, magmatism, crustal deformation, burial and/or exhumation, and fluid movement, any of which may offset the thermal effects of the others. Sedimentary basins are particularly suited to partitioning heat flow into its various components. We use Taranaki basin, New Zealand, as an example. It has a relatively undeformed (since the Miocene) western region that is used as a control against which the tectonically active eastern region can be compared. Although surface heat flow is roughly constant across Taranaki basin, basal heat flow modeled at lower crustal upper mantle depths varies by a factor of two or more. A combination of low heat-producing crust and the heat sink effects of crustal thickening in the eastern region can account for the basal heat-flow anomalies. The tectonic thermal anomaly would have gone unnoticed without the aid of detailed basin analysis and thermal modeling.

  17. Tectonic history and thrust-fold deformation style of seismically active structures near Coalinga

    SciTech Connect

    Namson, J.S. ); Davis, T.L.; Lagoe, M.B.

    1990-01-01

    The stratigraphy of the Coalinga region can be divided into tectostratigraphic facies whose boundaries delineate two major tectonic events - one in the mid-Cenozoic (38-17 Ma) and one in the late Cenozoic (less than 3 Ma). The succession of these tectostratigraphic facies, and an integration of geology, subsurface well data, a seismic-reflection profile, and earthquake seismicity on a retrodeformable cross section, yield a model for the tectonic evolution of the Coalinga region. This model suggests that the structural style of both deformational events is characteristic of fold and thrust belts. The model also indicates that the causative fault of the May 2 earthquake is a ramped thrust. The results of this study, in combination with regional geologic relations, suggest that the Coalinga region is part of an active fold and thrust belt which borders the west and south sides of the San Joaquin Valley. The potential for future earthquakes due to movement of other blind thrust faults within this belt should be evaluated.

  18. Active tectonics of the southeastern Upper Rhine Graben, Freiburg area (Germany)

    NASA Astrophysics Data System (ADS)

    Nivière, B.; Bruestle, A.; Bertrand, G.; Carretier, S.; Behrmann, J.; Gourry, J.-C.

    2008-03-01

    The Upper Rhine Graben has two Plio-Quaternary depocentres usually interpreted as resulting from tectonic reactivation. The southern basin, near Freiburg im Breisgau (Germany), contains up to 250 m of sediments. Beneath the younger alluvial deposits related to the current drainage system, a former river network deeply entrenched in the substratum reveals a very low regional base level of early Pleistocene age. The offset of channels at faults allows us to infer a Pleistocene reactivation of the syn-rift fault pattern and the estimation of slip rates. Maximum vertical movements along the faults have not exceeded 0.1 mm/yr since the middle Pleistocene. Current activity is concentrated along the westernmost faults. Morphologic markers indicate late Pleistocene reactivation of the Rhine River fault, and geophysical prospecting suggests a near-surface offset of young sedimentary deposits. The size of the fault segments potentially reactivated suggests that earthquakes with magnitude larger than Mw=6.3 could be expected in the area with a return interval of about 8000 years. Extrapolated to the duration of the Plio-Pleistocene, the strain rate estimates reveal that the tectonic forcing may account for only one-third to one-half of the whole thickness of the Plio-Pleistocene sediments of the basin fill. Thus other processes must be invoked to understand the growth of the Plio-Pleistocene basin. Especially the piracy of the Rhine River to the north during the early Pleistocene could explain these effects.

  19. Control of tectonic setting and large-scale faults on the basin-scale distribution of deformation bands in porous sandstone (Provence, France)

    NASA Astrophysics Data System (ADS)

    Ballas, G.; Soliva, R.; Benedicto, A.; Sizun, J.

    2013-12-01

    From outcrops located in Provence (South-East France), we describe the distribution, the microstructures, and the petrophysical properties of deformation bands networks related to different tectonic events. In contractional setting, pervasively distributed networks of reverse-sense compactional-shear bands are observed in all the folded-sand units of the foreland, whereas localized networks of clustered reverse-sense shear bands are only observed close to a large-scale thrust. In extensional setting, networks of clustered normal-sense shear bands are generally observed adjacent to large-scale faults, although few and randomly distributed bands are also observed between these faults. Normal-sense cataclastic faults are also observed restricted to sand units, suggesting that faults can initiate in the sands in extension, which is not observed in contraction. Shear bands and faults show cataclastic microstructures of low-permeability whereas compactional-shear bands show crush microbreccia or protocataclastic microstructures of moderate permeability. This basin-scale analysis underlines the major role of tectonic settings (thrust-fault versus normal-fault andersonian-stress regime) and the influence of inherited large-scale faults on the formation of low-permeability shear bands. We also provide a geometrical analysis of the band network properties (spacing, thickness, shear/compaction ratio, degree of cataclasis, petrophysical properties) with respect to the host sand granulometry. This analysis suggests that granulometry, although less important than tectonic setting and the presence of large-scale faults, has however a non-negligible effect on the band networks geometry.

  20. Geomorphological features of active tectonics and ongoing seismicity of northeastern Kumaun Himalaya, Uttarakhand, India

    NASA Astrophysics Data System (ADS)

    Pathak, Vivekanand; Pant, Charu C.; Darmwal, Gopal Singh

    2015-08-01

    The northeastern part of Kumaun Lesser Himalaya, Uttarakhand, India, lying between the rupture zones of 1905, Kangra and 1934, Bihar-Nepal earthquakes and known as `central seismic gap' is a segment of an active fault known to produce significant earthquakes and has not slipped in an unusually long time when compared to other segments. The studied section forms a part of this seismic gap and is seismically an active segment of the Himalayan arc, as compared to the remaining part of the Kumaun Lesser Himalaya and it is evident by active geomorphological features and seismicity data. The geomorphological features of various river valley transects suggest that the region had a history of tectonic rejuvenation which is testified by the deposition of various levels of terraces and their relative uplift, shifting and ponding of river channels, uplifted potholes, triangular facets on fault planes, fault scarps, etc. Further, the seismic data of five-station digital telemetered seismic network along with two stand alone systems show the distribution of earthquakes in or along the analyzed fault transects. It is observed that the microseismic earthquakes (magnitude 1.0-3.0) frequently occur in the region and hypocenters of these earthquakes are confined to shallow depths (10-20 km), with low stress drop values (1.0-10 bar) and higher peak ground velocity (PGV). The cluster of events is observed in the region, sandwiched between the Berinag Thrust (BT) in south and Main Central Thrust (MCT) in north. The occurrences of shallow focus earthquakes and the surface deformational features in the different river valley transect indicates that the region is undergoing neotectonic rejuvenation. In absence of chronology of the deposits it is difficult to relate it with extant seismicity, but from the geomorphic and seismic observations it may be concluded that the region is still tectonically active. The information would be very important in identifying the areas of hazard prone and

  1. Using Digital Topography to Differentiate Erosionally Exhumed and Tectonically Active Mountains Fronts

    NASA Astrophysics Data System (ADS)

    Frankel, K. L.; Pazzaglia, F. J.

    2003-12-01

    Mountain ranges in the southern Rocky Mountains have departed on unique landscape evolutionary pathways in the late Cenozoic that are directly dependent upon the degree of post-orogenic tectonic activity they have experienced. The topography of Sierra Nacimiento, a Laramide uplift in west-central New Mexico lacking an active range-front fault, is shaped primarily by erosional exhumation that is continuous, but not steady, being driven by distal base level fall from Rio Grande incision and resultant south to north knickpoint migration. In contrast, the topography of the Taos Range, a rift flank uplift in north-central New Mexico is shaped by contrasting active stream incision and aggradation astride an active range front normal fault. The distinction between exhumation-dominated and tectonically-dominated mountain fronts is best quantified by analyses of a new metric we call the drainage basin volume to drainage basin area ratio (V-A ratio) as well as the gradients of first-order streams. Drainage basin volume and area are calculated by constructing topographic envelope maps from 10 m resolution digital elevation models (DEM). The envelope maps are pinned by the watershed divide and cover the maximum elevations in each drainage basin. Subtracting the original DEM from the maximum elevation envelope map produces a topographic residual map from which area and volume data can be obtained. The erosionally exhumed Sierra Nacimiento has a mean V-A ratio of 88 m while the tectonically active Taos Range has a mean V-A ratio of 140 m. Similarly, there are systematic differences in the gradients of first order streams measured both in the range block and approximately 5 km of adjacent piedmont. Streams were defined and subsequently Strahler ordered by a flow accumulation threshold of 250 water-equivalent grid cell units. First order stream channel long profiles were extracted from the DEM at 30 meter increments and gradients were calculated by a FORTRAN program. Gradients of

  2. Tectonic activity revealed by morphostructural analysis: Development of the Sierra de la Candelaria range, northwestern Argentina

    NASA Astrophysics Data System (ADS)

    Barcelona, H.; Peri, G.; Tobal, J.; Sagripanti, L.; Favetto, A.

    2014-12-01

    The tectonically active broken foreland of NW Argentina is a recent analog of the eastern margin of the Puna plateau during Mio-Pliocene times and likely of other broken forelands worldwide. In order to evaluate active tectonism in the broken foreland of the NW Argentine Andes, we examined the complex geomorphology in the vicinity of the basement-cored Sierra de la Candelaria range at ˜26°S and deciphered multiple episodes of crustal deformation spanning the Pliocene to the Quaternary. Digital elevation models, satellite images and geological data within a GIS environment allowed us to analyze the terrain, drainage networks, river dynamics and structure, as well as to obtain detailed geomorphological mapping, active tectonic indices, longitudinal river profiles and structural sections. Three morphostructural segments were defined based on the structural features, the differential vertical dissection pattern over the basement, the faulted Pliocene to recent deposits, the stepwise propagation of anticlines and the distortion over the fluvial system. By combining the several lines of evidence, we concluded that the Sierra de la Candelaria range was subjected to a multi-stage development. The first stage uplifted the central segment concomitant with the formation of the surrounding ranges and with the main partition phase of the foreland. After a significant time lapse, the mountain range was subjected to southward thick-skinned growth and northward growth via stepwise thin-skinned deformation and exerted control over the dynamics of the Río Rosario. Taking into account the surrounding basins and ranges of the Sierra de la Candelaria, the southern Santa Bárbara System is characterized by partially isolated intramontane basins (Choromoro and Rosario) limited by shielded ranges that caused moisture block and shows continuous deformation. These features were related to early stages of a broken foreland evolution model and modern analogs were found at the northern

  3. Sedimentology of seismo-turbidites off the Cascadia and northern California active tectonic continental margins, Pacific Ocean

    NASA Astrophysics Data System (ADS)

    Gutierrez Pastor, Julia; Nelson, Hans; Goldfinger, Chris; Escutia, Carlota

    2013-04-01

    Holocene turbidites from turbidite channel systems along the active tectonic continental margins of the Cascadia subduction zone (offshore Vancouver Island to Mendocino Triple Junction) and the northern San Andreas Transform Fault (the Triple Junction to San Francisco Bay), have been analyzed for sedimentologic features related to their seismic origin. Centimeter thick silt/sand beds (turbidite base) capped by mud layers (turbidite tail) and interbedded with hemipelagic silty clay intervals with high biogenic content have been characterized by visual core descriptions, grain-size analysis, X-ray radiographs and physical properties. Along the northern California margin in upstream single tributary canyons and channels, most turbidites are uni-pulsed (classic fining up) whereas downstream below multiple tributary canyon and channel confluences, most deposits are stacked turbidites. Because each set of stacked turbidites has no hemipelagic sediment between each turbidite unit and each unit has a distinct mineralogy from a different tributary canyon, we interpret that a stacked turbidite is deposited by several coeval turbidity currents fed by multiple tributary canyons and channels with synchronous triggering from a single San Andreas Fault earthquake. The Cascadia margin is characterized by individual multi-pulsed turbidites that contain multiple coarse-grained sub-units without hemipelagic sediment between pulses. Because the number and character of multiple coarse-grained pulses for each correlative multi-pulsed turbidite is almost always constant both upstream and downstream in different channel systems for 600 km along the margin,we interpret that the earthquake shaking or aftershock signature is usually preserved, for the much stronger Cascadia (≥9 Mw) compared to weaker California (≥8Mw) earthquakes, which result in upstream uni-pulsed turbidites and downstream stacked turbidites. Consequently, both the strongest (≥9 Mw) great earthquakes and downstream

  4. Tectonic earthquakes of anthropogenic origin

    NASA Astrophysics Data System (ADS)

    Adushkin, V. V.

    2016-03-01

    The enhancement of seismicity induced by industrial activity in Russia in the conditions of present-day anthropization is noted. In particular, the growth in the intensity and number of strong tectonic earthquakes with magnitudes M ≥ 3 (seismic energy 109 J) due to human activity is revealed. These man-made tectonic earthquakes have started to occur in the regions of the East European Platform which were previously aseismic. The development of such seismicity is noted in the areas of intense long-term mineral extraction due to the increasing production depth and extended mining and production. The mechanisms and generation conditions of man-made tectonic earthquakes in the anthropogenically disturbed medium with the changed geodynamical and fluid regime is discussed. The source zones of these shallow-focus tectonic earthquakes of anthropogenic origin are formed in the setting of stress state rearrangement under anthropogenic loading both near these zones and at a significant distance from them. This distance is determined by the tectonic structure of the rock mass and the character of its energy saturation, in particular, by the level of the formation pressure or pore pressure. These earthquakes occur at any time of the day, have a triggered character, and are frequently accompanied by catastrophic phenomena in the underground mines and on the surface due to the closeness to the source zones.

  5. Primary centers and secondary concentrations of tectonic activity through time in the western hemisphere of Mars

    USGS Publications Warehouse

    Anderson, R.C.; Dohm, J.M.; Golombek, M.P.; Haldemann, A.F.C.; Franklin, B.J.; Tanaka, K.L.; Lias, J.; Peer, B.

    2001-01-01

    Five main stages of radial and concentric structures formed around Tharsis from the Noachian through the Amazonian as determined by geologic mapping of 24,452 structures within the stratigraphic framework of Mars and by testing their radial and concentric orientations. Tectonic activity peaked in the Noachian (stage 1) around the largest center, Claritas, an elongate center extending more than 20?? in latitude and defined by about half of the total grabens which are concentrated in the Syria Planum, Thaumasia, and Tempe Terra regions. During the Late Noachian and Early Hesperian (stage 2), extensional structures formed along the length of present-day Valles Marineris and in Thaumasia (with a secondary concentration near Warrego Vallis) radial to a region just to the south of the central margin of Valles Marineris. Early Hesperian (stage 3) radial grabens in Pavonis, Syria, Ulysses, and Tempe Terra and somewhat concentric wrinkle ridges in Lunae and Solis Plana and in Thaumasia, Sirenum, Memnonia, and Amazonis are centered northwest of Syria with secondary centers at Thaumasia, Tempe Terra, Ulysses Fossae, and western Valles Marineris. Late Hesperian/Early Amazonian (stage 4) structures around Alba Patera, the northeast trending alignment of Tharsis Montes, and Olympus Mons appears centered on Alba Patera. Stage 5 structures (Middle-Late Amazonian) represent the last pulse of Tharsis-related activity and are found around the large shield volcanoes and are centered near Pavonis Mons. Tectonic activity around Tharsis began in the Noachian and generally decreased through geologic time to the Amazonian. Statistically significant radial distributions of structures formed during each stage, centered at different locations within the higher elevations of Tharsis. Secondary centers of radial structures during many of the stages appear related to previously identified local magmatic centers that formed at different times and locations throughout Tharsis. Copyright 2001 by

  6. Geochemistry of sandstones from the Pliocene Gabir Formation, north Marsa Alam, Red Sea, Egypt: Implication for provenance, weathering and tectonic setting

    NASA Astrophysics Data System (ADS)

    Zaid, Samir M.

    2015-02-01

    Petrographic, major and trace element compositions of sandstones from the Pliocene Gabir Formation, Central Eastern Desert, Egypt have been investigated to determine their provenance, intensity of paleo-weathering of the source rocks and their depositional tectonic setting. Gabir Formation is composed mainly of sandstones alternating with limestone and shale beds. The Gabir sandstone is yellowish gray to yellowish brown color, calcareous and fossiliferous. The composition of this formation refers to shallow warm agitated marine conditions. Texturally, Gabir sandstones are immature, poorly sorted and grain supported. Abundance of feldspars indicates rapid deposition of sediments from a nearby source rocks. Their average modal composition (Q71.35F16.6L12.05), classifies them as sublitharenite and arkose with subordinate litharenite and subarkose, which is also supported by geochemical study. Chemical analyses revealed that sandstones have high SiO2, K2O > Na2O, and low Fe2O3 values, which are consistent with the modal data. Also, sandstone samples are enriched in most trace elements such as Ba, Sr, Ni, Cr and Zr and depleted in U and Th. The petrography and geochemistry suggest that Gabir sandstones were deposited in an active continental margin basin. They were mainly derived from granitic and low grade metamorphic sources. The CIA values (41.69-74.84) of the Gabir sandstones indicate low to moderate degree of chemical weathering, which may reflect cold and/or arid climate conditions in the source area. The source rocks are probably identified to be Proterozoic granites, metagabbros and metavolcanics, which must have been exposed during rifting, initiated during Oligocene and continued till post Miocene.

  7. The dehydration, rehydration and tectonic setting of greenstone belts in a portion of the northern Kaapvaal Craton, South Africa

    NASA Technical Reports Server (NTRS)

    Vanreenen, D. D.; Barton, J. M., Jr.; Roering, C.; Vanschalkwyk, J. C.; Smit, C. A.; Debeer, J. D.; Stettler, E. H.

    1986-01-01

    High-grade gneiss terranes and low-grade granite-greenstone terranes are well known in several Archaean domains. The geological relationship between these different crustal regions, however, is still controversial. One school of thought favors fundamental genetic differences between high-grade and low-grade terranes while others argue for a depth-controlled crustal evolution. The detailed examination of well-exposed Archaean terranes at different metamorphic grades, therefore, is not only an important source of information about the crustal levels exposed, but also is critical to the understanding of the possible tectonic and metamorphic evolution of greenstone belts with time. Three South African greenstone belts are compared.

  8. An attempt to monitor tectonic forces in the Vrancea active geodynamic zone: The Baspunar experiment

    NASA Astrophysics Data System (ADS)

    Besutiu, Lucian; Zlagnean, Luminita; Plopeanu, Marin

    2013-04-01

    (sparsely) run in the area, have provided inconsistent results on the PCF current dynamics. The Baspunar Geodynamic Observatory (BGO) has been designed and implemented by the Solid Earth Dynamics Department in the Institute of Geodynamics of the Romanian Academy in order to reveal and monitor eventual motions along PCF in the attempt to correlate variations in the slip rate with changes in the seismicity released within Vrancea zone. The first BGO records were strongly affected by changes in the atmospheric parameters. Consequently, technical measures and special corrections for the removal or at least mitigation of the effects created by changes in temperature, air pressure and humidity have been applied to the observations. In order to improve the signal to noise ratio, some mathematical filters have been applied too. The paper is aimed at revealing results of the geodetic observations along with preliminary geodynamic considerations. On the overall, after about two years of monitoring, PCF appears as an active tectonic contact. It mainly behaves as a left-lateral fault, but some short episodes with a reverse slip (dextral) were also pointed out. Correlations with crustal and intermediate-depth earthquakes occurring in both cases within the bending zone of East Carpathians are illustrated and discussed.

  9. Identifying induced seismicity in active tectonic regions: A case study of the San Joaquin Basin, California

    NASA Astrophysics Data System (ADS)

    Aminzadeh, F.; Göbel, T.

    2013-12-01

    Understanding the connection between petroleum-industry activities, and seismic event occurrences is essential to monitor, quantify, and mitigate seismic risk. While many studies identified anthropogenically-induced seismicity in intraplate regions where background seismicity rates are generally low, little is known about how to distinguish naturally occurring from induced seismicity in active tectonic regions. Further, it is not clear how different oil and gas operational parameters impact the frequency and magnitude of the induced seismic events. Here, we examine variations in frequency-size and spatial distributions of seismicity within the Southern Joaquin basin, an area of both active petroleum production and active fault systems. We analyze a newly available, high-quality, relocated earthquake catalog (Hauksson et al. 2012). This catalog includes many seismic events with magnitudes up to M = 4.5 within the study area. We start by analyzing the overall quality and consistence of the seismic catalog, focusing on temporal variations in seismicity rates and catalog completeness which could indicate variations in network sensitivity. This catalog provides relatively homogeneous earthquake recordings after 1981, enabling us to compare seismicity rates before and after the beginning of more pervasive petroleum-industry activities, for example, hydraulic-fracturing and waste-water disposals. We conduct a limited study of waste-water disposal wells to establish a correlation between seismicity statistics (i.e. rate changes, fractal dimension, b-value) within specific regions and anthropogenic influences. We then perform a regional study, to investigate spatial variations in seismicity statistics which are then correlated to oil field locations and well densities. In order to distinguish, predominantly natural seismicity from induced seismicity, we perform a spatial mapping of b-values and fractal dimensions of earthquake hypocenters. Seismic events in the proximity to

  10. Holocene canyon activity under a combination of tidal and tectonic forcing

    NASA Astrophysics Data System (ADS)

    Mountjoy, Joshu; Micallef, Aaron; Stevens, Craig; Stirling, Mark

    2013-04-01

    The majority of submarine canyon systems that are active during sea level highstands are coupled to terrestrial or littoral sediment transport systems (e.g. high sediment-yield rivers, wave-base sediment disturbance). However, non-coupled canyon systems can also exhibit sedimentary activity. Characterising the nature, origin, and spatial and temporal influence of the processes responsible for this sedimentary activity is important to understand the extent of sediment and carbon transfer to the deep sea, the impact of sedimentary flows on biological colonisation and diversity, and the control of recent seafloor processes on canyon morphology. The Cook Strait canyon system, between the North and South islands of New Zealand, is a large (1800 km2), multi-branching, shelf-indenting canyon on an active subduction margin. The canyon comes within 1 km of the coast, but does not intercept fluvial or littoral sediment systems and is therefore defined as a non-terrestrially-coupled system. Sediment transport on the continental shelf, associated with a strong tidal stream, and seafloor disturbance related to numerous high-activity faults is known from previous studies. Little is known, however, about the rates of sedimentary activity in the canyon and the processes driving it. The canyon system therefore provides an excellent study area for understanding sediment transport in a non-coupled submarine canyon system. Analysis of EM300 multibeam bathymetry, gravity cores, 3.5 kHz seismic reflection profiles, camera and video transects and current meter data reveals a system where oceanographic (tidal) and tectonic (earthquake) processes are moving sediment from the continental shelf, through the upper canyon, and finally to the deep ocean. Sediment accumulation rates may reach several mm/yr in the upper canyons, with data suggesting minimum rates of 0.5 mm/yr. We demonstrate that tidal currents are sufficient to mobilise fine to medium sand around and within the upper canyon

  11. Active tectonics along the Nebrodi-Peloritani boundary in northeastern Sicily (Southern Italy)

    NASA Astrophysics Data System (ADS)

    Pavano, F.; Romagnoli, G.; Tortorici, G.; Catalano, S.

    2015-09-01

    In the epicentral area of the seismic swarm of the June-September 2011, at southern edge of the Calabrian arc in NE Sicily, very recent extensional motions remobilised two main NW-SE dextral faults. The extensional reactivation of strike-slip faults responded to a new regional dynamic, also evidenced by GPS and seismological data. The inverted structures are aligned at the margin of a wide crustal block that is moving apart from the rest of the island and is uplifting faster than the adjacent regions. The active faults terminate to the northwest at the intersection with a prominent NNE trending fault that represents the western boundary of the mobile block. The vertical displacement along this border exactly matches the difference in elevation of the marine terraces resting inside and outside the block, respectively. On the contrary, only part of differential displacement of the marine terraces was actually accommodated as cumulative motion along the two NW oriented inverted faults, across the southwestern boundary of the block. Amounts of the vertical displacement were distributed on distinct fault planes of the previous dextral shear belts. The widespread fracturing is also the best explanation for the seismic swarm of the 2011, whose epicenters spread on a discrete rock volume rather than concentrated along a single fault plane. The diffuse fracturing seems to represent a peculiar style of deformation, connected to the tectonic inversion of previous strike-slip shear zones. Seismic swarm also affects the northern termination of the Calabrian arc where active extensional deformation reactivated previous strike-slip faults. The similarity of the two regions suggests that seismic swarm can be peculiar of extensional belts developed on previous strike-slip shear zones, along which the pre-existing geometry favours the dispersion of the tectonic motion on a network of small linked fault planes.

  12. Active tectonic characteristics of river terraces along the Tianquan River, Sichuan, China

    NASA Astrophysics Data System (ADS)

    Cai, Y. M.; Shyu, J. B. H.; Chang, C. P.

    2015-12-01

    The Longmenshan fold-and-thrust belt at the western edge of the Sichuan Basin has long been identified as an active tectonic belt. This has been clearly illustrated by the disastrous Wenchuan and Lushan earthquakes in the recent decade. The two earthquakes, however, have distinctive characters. In the north, the Wenchuan event occurred on major fault zones identified previously. But in the south, the Lushan event was not accompanied by surface ruptures, and the seismogenic structure is still under debate. In order to further understand the neotectonic characteristics of the Lushan earthquake region, we analyzed fluvial terraces, in the hope that such geomorphic features would provide information of active structures of the area. Along the Tianquan River, river terraces are particularly well developed near two cities, Tianquan and Shiyang. Since the terraces appear to be very wide and limited in these two basin-like areas, we suspected that they formed as filled-up lakes. However, after detailed field investigations, we found that underneath these terraces, early Tertiary bedrocks crop out below river sediments that are only several meters thick. This indicates that the Tianquan River has incised into bedrocks. The slope of the terrace surfaces is similar to that of the present-day riverbed, and the river sediments in the terrace outcrops have similar grain size distribution as current riverbed sediments. Therefore, we suggest that the terraces along the Tianquan River are not related to dammed lake, but were produced by tectonic uplift. Combining the age of terrace sediments dated by optically stimulated luminescence (OSL) and detailed topography of the terrace surfaces, we aim to establish a model for the formation mechanism of these two terrace groups. We hope the results of this study would provide more information of neotectonic characteristics of the southwestern Sichuan Basin, as well as future earthquake hazards in this densely populated region.

  13. Provenance and fate of arsenic and other solutes in the Chaco-Pampean Plain of the Andean foreland, Argentina: From perspectives of hydrogeochemical modeling and regional tectonic setting

    NASA Astrophysics Data System (ADS)

    Raychowdhury, Nilasree; Mukherjee, Abhijit; Bhattacharya, Prosun; Johannesson, Karen; Bundschuh, Jochen; Sifuentes, Gabriela Bejarano; Nordberg, Erika; Martin, Raúl A.; Storniolo, Angel del Rosario

    2014-10-01

    Extensive arsenic (As) enriched groundwater is known to occur in the aquifers of the Chaco-Pampean Plain of Argentina. Previous studies speculated that the As mobilization in these groundwaters was a direct result of their elevated pH and oxidative conditions. The volcanic glass layers present in the aquifer matrix were hypothesized as one of the possible sources of As to the groundwaters. Here, we examine the groundwater chemistry of the Santiago del Estero province of Chaco-Pampean Plains of Argentina, and test these hypotheses by using hydrogeochemical modeling within the framework of the regional geologic-tectonic setting. The study area is located in the active foreland of the Andean orogenic belt, which forms a continental arc setting, and is dotted with several hot springs. Rhyolitic volcanic glass fragments derived from arc volcanism are abundant within the aeolian-fluvial aquifer sediments, and are related to the paleo-igneous extrusion in the vicinity. Hydrogeochemical analyses show that the groundwater is in predominantly oxidative condition. In addition, some of the groundwaters exhibit very high Na, Cl- and SO42- concentrations. It is hypothesized in this study that the groundwater chemistry has largely evolved by dissolution of rhyolitic volcanic glass fragments contained within the aquifer sediments along with mixing with saline surface waters from, adjoining salinas, which are thought to be partially evaporated remnants of a paleo inland sea. Flow path modeling, stability diagrams, and thermodynamic analyses undertaken in this study indicate that the dominant evolutionary processes include ion exchange reactions, chemical weathering of silicate and evaporites, in monosialitization-dominated weathering. Geochemical modeling predicts that plagioclase feldspar and volcanic glass are the major solids phases that contribute metal cations and dissolved silica to the local groundwaters. Co-influxed oxyanions, with similar ionic radii and structure (e.g. Mo

  14. Active tectonic deformation along rejuvenated faults in tropical Borneo: Inferences obtained from tectono-geomorphic evaluation

    NASA Astrophysics Data System (ADS)

    Mathew, Manoj Joseph; Menier, David; Siddiqui, Numair; Kumar, Shashi Gaurav; Authemayou, Christine

    2016-08-01

    The island of Borneo is enveloped by tropical rainforests and hostile terrain characterized by high denudation rates. Owing to such conditions, studies pertaining to neotectonics and consequent geomorphic expressions with regard to surface processes and landscape evolution are inadequately constrained. Here we demonstrate the first systematic tectono-geomorphic evaluation of north Borneo through quantitative and qualitative morphotectonic analysis at sub-catchment scale, for two large drainage basins located in Sarawak: the Rajang and Baram basins. The extraction of morphometric parameters utilizing digital elevation models arranged within a GIS environment focuses on hypsometric curve analysis, distribution of hypsometric integrals through spatial autocorrelation statistics, relative uplift values, the asymmetry factor and the normalized channel steepness index. Hypsometric analysis suggests a young topography adjusting to changes in tectonic boundary conditions. Autocorrelation statistics show clusters of high values of hypsometric integrals as prominent hotspots that are associated with less eroded, young topography situated in the fold and thrust belts of the Interior Highlands of Borneo. High channel steepness and gradients (> 200 m0.9) are observed in zones corresponding to the hotspots. Relative uplift values reveal the presence of tectonically uplifted blocks together with relatively subsided or lesser uplifted zones along known faults. Sub-catchments of both basins display asymmetry indicating tectonic tilting. Stream longitudinal profiles demonstrate the presence of anomalies in the form of knickzones without apparent lithological controls along their channel reaches. Surfaces represented by cold spots of low HI values and low channel gradients observed in the high elevation headwaters of both basins are linked to isolated erosional planation surfaces that could be remnants of piracy processes. The implication of our results is that Borneo experiences

  15. Two-dimensional numerical modeling of tectonic and metamorphic histories at active continental margins

    NASA Astrophysics Data System (ADS)

    Gerya, Taras; Stöckhert, Bernhard

    2006-04-01

    The evolution of an active continental margin is simulated in two dimensions, using a finite difference thermomechanical code with half-staggered grid and marker-in-cell technique. The effect of mechanical properties, changing as a function of P and T, assigned to different crustal layers and mantle materials in the simple starting structure is discussed for a set of numerical models. For each model, representative P T paths are displayed for selected markers. Both the intensity of subduction erosion and the size of the frontal accretionary wedge are strongly dependent on the rheology chosen for the overriding continental crust. Tectonically eroded upper and lower continental crust is carried down to form a broad orogenic wedge, intermingling with detached oceanic crust and sediments from the subducted plate and hydrated mantle material from the overriding plate. A small portion of the continental crust and trench sediments is carried further down into a narrow subduction channel, intermingling with oceanic crust and hydrated mantle material, and to some extent extruded to the rear of the orogenic wedge underplating the overriding continental crust. The exhumation rates for (ultra)high pressure rocks can exceed subduction and burial rates by a factor of 1.5 3, when forced return flow in the hanging wall portion of the self-organizing subduction channel is focused. The simulations suggest that a minimum rate of subduction is required for the formation of a subduction channel, because buoyancy forces may outweigh drag forces for slow subduction. For a weak upper continental crust, simulated by a high pore pressure coefficient in the brittle regime, the orogenic wedge and megascale melange reach a mid- to upper-crustal position within 10 20 Myr (after 400 600 km of subduction). For a strong upper crust, a continental lid persists over the entire time span covered by the simulation. The structural pattern is similar in all cases, with four zones from trench toward arc

  16. Comparison of submarine gully morphologies in passive and active margin settings

    NASA Astrophysics Data System (ADS)

    Jackson, C.; Shumaker, L.; Johnstone, S.; Graham, S. A.

    2015-12-01

    Passive and active tectonic margins have inherently different hypsometry, due to local patterns of deformation and subsequent impacts on the style of sedimentation. One way we can analyze and compare the two settings is through observation of submarine gullies, which are small channel features that form along the continental slope as it descends to the ocean floor. By documenting the geometries of gullies that have formed on passive margins and gullies that have formed on active margins, we attempt to distinguish differences in gully morphologies in these two settings. We manually mapped over 600 gullies and interfluves from shaded relief and contour maps generated from bathymetric data across the globe, including the coast of California, the Beaufort Sea, and the Black Sea. We extrapolated and plotted elevation profiles of the gullies along their downslope distance, and compared a range of gully properties, such as length, spacing, and slope, to look at the correlations among those elements of gullies and their tectonic setting. We find that gullies forming on active margins show the greatest variability in their slopes, exhibiting both the steepest and the shallowest slopes of the dataset. The slopes of the passive margin gullies fall within the range of the active margin gully slopes, but interestingly, we note patterns in the ranges of gully steepness at different localities. These results differ from our our anticipation that active margin gullies are steeper than passive margin gullies, but suggest that gullies in all settings display a variety of morphologies. Additional mapping of active margin gullies will better determine if there are morphological differences between the two settings.

  17. Geodetic evidence for tectonic activity on the Strymon Fault System (NE Greece)

    NASA Astrophysics Data System (ADS)

    Mouslopoulou, Vasiliki; Gianniou, Michail; Saltogianni, Vasso; Stiros, Stathis

    2014-05-01

    Geological, seismological and geodetic data have provided so far limited evidence of crustal deformation in northeast Greece (Thrace and East Macedonia); hence, the active tectonics of this area remains largely unknown. Here, we use monthly GPS solutions from 21 permanent stations of the Hellenic GPS Network (HEPOS) to shed light in the kinematics of NE Greece. Analysis of our dataset, that collectively spans a period of five years, shows that displacement vectors that derive from either side of the natural depression of the Strymon (Struma) Valley differ significantly in orientation and magnitude. The latter testify to a clear left-lateral displacement along the Strymon Fault System (SFS) with a mean fault displacement rate of ~3.7 mm/yr, while the area west of it behaves like a quasi-rigid tectonic block. The polarity of shear along the SFS appears to have changed, from right-lateral to left-lateral, during the last ~5 Ma, a period that coincides with the onset of faulting along the prolongation of the fast-moving (>20 mm/yr) North Anatolian Fault into the north Aegean. Thus, left-lateral slip along the SFS may occur in conjunction with, and in response to, right-lateral oblique slip along the North Aegean Trough, indicating that faulting in north Aegean is intimately linked in space and time. If the interseismic strain stored currently across the SFS (~3.7 mm/yr) is released seismically through large magnitude earthquakes, it may have serious implications in the seismic hazard of this densely populated region, which also accommodates important civil infrastructure.

  18. Relative tectonic activity assessment along the East Anatolian strike-slip fault, Eastern Turkey

    NASA Astrophysics Data System (ADS)

    Khalifa, Abdelrahman

    2016-04-01

    The East Anatolian transform fault is a morphologically distinct and seismically active left-lateral strike-slip fault that extends for ~ 500 km from Karlıova to the Maraş defining the boundary between the Anatolian Block and Syrian Foreland. Deformed landforms along the East Anatolian fault provide important insights into the nature of landscape development within an intra-continental strike-slip fault system. Geomorphic analysis of the East Anatolian fault using geomorphic indices including mountain front sinuosity, stream length-gradient index, drainage density, hypsometric integral, and the valley-width to valley height ratio helped differentiate the faulting into segments of differing degrees of the tectonic and geomorphic activity. Watershed maps for the East Anatolian fault showing the relative relief, incision, and maturity of basins along the fault zone help define segments of the higher seismic risk and help evaluate the regional seismic hazard. The results of the geomorphic indices show a high degree of activity, reveal each segment along the fault is active and represent a higher seismic hazard along the entire fault.

  19. Tectonic?palaeoenvironmental forcing of clay-mineral assemblages in nonmarine settings: the Oligocene?Miocene As Pontes Basin (Spain)

    NASA Astrophysics Data System (ADS)

    Sáez, A.; Inglès, M.; Cabrera, L.; de las Heras, A.

    2003-07-01

    rather diverse clay compositions. This clearly reflects the influence on clay assemblages of palaeoenvironmental changes forced by the morphological and tectonic evolution of the catchment-basin system. The interplay between climate and tectonic processes in the source areas did not result in major variations of the clay minerals fed into the basin. Conversely, this tectonic-sedimentation interplay influenced the evolution of the drainage and the water balance in the depositional zones, causing a complex environmental-hydrochemical evolution to occur. As a consequence, drastic early diagenetic changes affected the original clay mineral assemblages and resulted in a variety of early diagenetic assemblages. The As Pontes case study emphasises the major influence of palaeogeographical and tectonosedimentary evolution on the clay mineral record in nonmarine depositional systems. The depositional record in As Pontes Basin demonstrates that morphological and tectonically forced environmental and hydrochemical changes can result in variations similar to those forced by low-order climatic changes and that, in some cases, the role of climate can be negligible.

  20. Interpretation of tectonic setting in the Phetchabun Volcanic Terrane, Northern Thailand: Evidence from enhanced airborne geophysical data

    NASA Astrophysics Data System (ADS)

    Sangsomphong, Arak; Thitimakorn, Thanop; Charusiri, Punya

    2015-08-01

    Re-processed aeromagnetic data with enhancement approaches of reduction to the pole, high pass filtering and shaded relief have been used to interpret complex subsurface structures of the Carboniferous to Triassic Phetchabun Volcanic Terrane (PVT) which is largely covered by thick Cenozoic sediment deposits. Interpretation of the enhanced aeromagnetic data reveals four distinct structural domains in the PVT, viz. Northern, Eastern, Central, and Western domains. Within these domains, high magnetic units are recognized, namely elongate, ring, circular, and dipolar spot units. The elongate unit in the Central domain is characterized by a deformation zone with northwest-southeast trending, sinistral shearing. East-west trending and the northeast-southwest trending faults cross-cut several magnetic units in the Central domain, with sinistral and dextral movements, respectively. Three major fault directions have been identified, including the northeast-southwest trending sinistral faults, north-south trending dextral faults, and northwest-southeast trending dextral faults. The younger spot units are small intrusive bodies largely situated along these latest fault segments. The aeromagnetic interpretation results, together with relevant current field verification, as well as previous geochronological and petrochemical investigations, have lead to the clarification of structural development in the PVT. The elongate units are interpreted to represent Late Carboniferous intrusive bodies. They occurred as a result of an eastward subduction of the Nakhonthai oceanic plate beneath the Indochina continental plate, along the Loei suture. The elongate units are also reflected in a north-south trending deformation zone formed by the east-west compressional tectonics. The ring units are considered to have formed in a Permo-Triassic volcanic arc, whereas the circular units represent equigranular intrusive bodies which formed in a response to the second phase of eastward subduction

  1. Impact of the Yakutat indentor corner on present-day tectonics and fault activity in SE Alaska - SW Yukon

    NASA Astrophysics Data System (ADS)

    Mazzotti, S.; Marechal, A.; Ritz, J. F.; Ferry, M. A.

    2015-12-01

    We present an active tectonic model of the SE Alaska - SW Yukon region based principally on the integration of recent GPS velocity data and new fault-slip rates derived from geomorphology. In this region, the Yakutat collision results in complex tectonics with patterns of strain localization and strain partitioning that strongly vary across the various mountain ranges and active faults. We propose that deformation and fault activity in the St. Elias and Chugach Mountains are primarily controlled by the eastern syntaxis of the Yakutat collision, which produces a semi-radial tectonic pattern: Velocities, principal horizontal shortening rates, and maximum horizontal stress orientations rotate by 60 - 80 ° around the syntaxis, from roughly parallel to the relative Pacific - North America motion at the front of the collision to roughly orthogonal southeast of the syntaxis. The interaction between this strain pattern and major inherited tectonic structures inland of the collision zone (i.e., Denali and Duke River Faults) results in various reactivation modes of these structures. Specifically, the Denali Fault shows a very pronounced lateral variations of activity from ~12 mm/a of dextral slip rate in its central section to ~1 mm/a of mostly shortening slip rate along its southern section. This marked change of activity is associated with a possible relay system where the Duke River and Totschunda Faults accommodate a major part (8 - 12 mm/a) of the inland strain transfer directly in front of the syntaxis. This new tectonic model retains some questions, in particular regarding the mechanisms of deformation and strain transfer (1) from the syntaxis to the Duke River - Totschunda system and (2) at the junction between Totschunda and Denali Faults. Numerical models of present-day deformation may help address these issues and provide information about relative strength of the various crustal and inherited fault elements of this system.

  2. Recent Fluvial, Volcanic, and Tectonic Activity on the Cerberus Plains of Mars

    NASA Astrophysics Data System (ADS)

    Berman, Daniel C.; Hartmann, William K.

    2002-09-01

    Athabasca and Marte Valles lie on the Cerberus plains, between the young, lava-covered plains of Elysium Planitia and Amazonis Planitia. To test pre- MGS ( Mars Global Surveyor) suggestions of extremely young volcanic and fluvial activity, we present the first crater counts from MGS imagery, at resolutions (˜2-20 m/pixel) much higher than previously available. The most striking result, based on morphologic relations as well as crater counts from different stratigraphic units, is to confirm quantitatively that these channel systems are much younger than most other major outflow channels. The general region has an average model age for lava and fluvial surfaces of ≤200 Myr, and has possibly seen localized water releases, interspersed with lava flows, within the past 20 Myr. The youngest lavas may be no more than a few megayears old. Access of lava and liquid brines to the surface may be favored by openings of the Cerberus Fossae fracture system, but, as shown in the new images, the fractures appear to have continued developing more recently than the most recent lavas or fluvial activity. The Cerberus Fossae system may be an analog to an early stage of Valles Marineris, and its youthful activity raises questions about regional tectonic history. Large-volume water delivery to the surface of young lava flows in recent martian history puts significant boundary conditions on the storage and history of water on Mars.

  3. Geomorphic assessment of the tectonic activity of Qiulitagh fold-belt, Kuqa foreland basin, Xinjiang, China

    NASA Astrophysics Data System (ADS)

    Saint Carlier, Dimitri; Graveleau, Fabien; Delcaillau, Bernard; Hurtrez, Jean-Emmanuel; Vendeville, Bruno

    2014-05-01

    The Qiulitagh fold belt is an anticline structure located in the Kuqa fold-and-thrust belt (southern Tian Shan, China), whose active folding is well documented by structural and palaeomagnetic studies (Chen et al., 2007; Hubert-Ferrari et al., 2007; Li et al., 2012; Wang et al., 2011). The topography of Quilitagh fold belt can be divided into two SW-NE parallel ridges: 1) a 90 km long northern ridge, composed of the Northern Qiulitagh anticline and the Yakelike anticline, and 2) a 165km long southern ridge, composed of the Southern Qiulitagh anticline and the Mishikantage anticline. Due to the current absence of vegetation and relative homogeneity of outcropping lithologies (mainly Neogene detrital sandstone and silstone), these anticlines provide exceptional field cases for investigating the dynamic relationships between fold growth mechanisms, the subsurface structures, the geomorphic entities and the drainage network evolution. We used free topographic and satellite image datasets to carry out a morphometric study of the Quilitagh fold-belt and investigate the kinematics of active folding. Topographic datasets include Digital Elevation Models (DEM) from the NASA SRTM V.4.0 and ASTER programs, whereas satellite images are extracted from Landsat 7 shots and Google Earth. These datasets were incorporated in GIS software where three scales of observation were investigated: 1) a global fold scale, 2) a drainage basin scale and 3) a valley scale. At the drainage basin scale, we selected about 250 items and quantified several geomorphic indices of relative active tectonic growth. These are the basin mean slope, hypsometric integral, basin asymmetry and local relief. We also used published seismic profiles to link the 3D subsurface geometry of the salt-related Qiulitagh fold belt with the geomorphic signal. Results indicate that the morphometry of Quilitagh drainage basins (hypsometry, drainage basin asymmetry, local relief, valley incision, steepness index) change

  4. The feedback between active tectonics, fluid flow and mineralization in an Andean geotermal reservoir

    NASA Astrophysics Data System (ADS)

    Reich, M.; Arancibia, G.; Perez, P.; Sanchez, P.; Cembrano, J. M.; Stimac, J. A.; Lohmar, S.

    2012-12-01

    In the Andean Cordillera of Central-Southern Chile, geothermal resources occur in close spatial relationship with active volcanism. The nature of the relationship between tectonics and volcanism in this region is the result of interaction between the crustal structures of the basement and the ongoing regional stress field, which is primarily controlled by the oblique convergence of the Nazca and South America Plates. Between 39° and 46°S, the volcanic and geothermal activity is controlled by the NNE-trending, 1,000 km long Liquiñe-Ofqui Fault Zone (LOFZ), an intra-arc dextral strike-slip fault system. Although there is consensus that volcanism (and hence geothermal activity) in southern Chile is largely controlled by the regional-scale tectonic stress field and architecture of the volcanic arc, there is limited scientific information about the role of local kinematic conditions on fluid flow and mineralization during the development and evolution of geothermal reservoirs. In this report, we present the preliminary results of an undergoing structural, mineralogical and geochemical study of the Tolhuaca geothermal system in southern Chile. The Tolhuaca geothermal reservoir formed as a liquid-dominated hydrothermal system, where shallow upflow resulted in near-boiling temperatures in a roughly horizontal liquid reservoir at 100-200 m depth (Melosh et al., 2010, 2012). In an early stage of evolution, hydrothermal brecciation and phase-separation (boiling) episodes penetrated at least 950 m depth into the deeper reservoir, and boiling was followed by steam-heated water invasion that cooled the reservoir. In a later stage, the preliminary conceptual model involves boiling and reheating of the reservoir, forming a system with deep hot brines that is connected to the shallow steam zone by an upflow conduit that is characterized by high-temperature mineralogy. The structural analysis of veins, fault-veins and faults of the Tol-1 drillcore (~1080 m depth) provide insights

  5. Influence of depth, focal mechanism, and tectonic setting on the shape and duration of earthquake source time functions

    NASA Astrophysics Data System (ADS)

    Houston, Heidi

    2001-06-01

    Source time functions of 255 moderate to great earthquakes obtained from inversions of teleseismic body waves by Tanioka and Ruff [1997] and coworkers were compared in a systematic way. They were scaled to remove the effect of moment and to allow the direct comparison and averaging of time function shape as well as duration. Time function durations picked by Tanioka and Ruff [1997] are proportional to the cube root of seismic moment if moments from the Harvard centroid moment tensor catalog are used. The average duration of scaled time functions is shorter and the average shape has a more abrupt termination for deeper events than shallower ones, with a distinct change occurring at ˜40 km depth. The complexity of the time functions, as quantified by the number of subevents, appears to decrease below ˜40 km depth. Furthermore, among events shallower than 40 km, the average duration of scaled time functions is shorter, and their average shape has a more abrupt termination (1) for events with strike-slip focal mechanisms compared to thrust events and (2) for the few thrust events associated with an intraplate setting compared to the majority associated with an interplate (subduction) boundary. In each of these cases, events in more technically and seismically active settings have a longer duration and a more gradual termination. This can be interpreted in terms of lower stress drops and/or slower rupture velocities at active plate boundaries, suggesting that fault rheology depends on slip rate and may evolve as total fault slip accumulates. Furthermore, differences in average time function shape and duration associated with different subduction zones suggest that differences exist in the rheology on the plate boundaries at the various subduction zones. Supporting data table is available via Web browser or via Anonymous FTP from ftp://kosmos.agu.org, directory "append" (Username = "anonymous", Password = "guest"); subdirectories in the ftp site are arranged by paper

  6. Pore pressure sensitivities to dynamic strains: Observations in active tectonic regions

    NASA Astrophysics Data System (ADS)

    Barbour, Andrew J.

    2015-08-01

    Triggered seismicity arising from dynamic stresses is often explained by the Mohr-Coulomb failure criterion, where elevated pore pressures reduce the effective strength of faults in fluid-saturated rock. The seismic response of a fluid-rock system naturally depends on its hydromechanical properties, but accurately assessing how pore fluid pressure responds to applied stress over large scales in situ remains a challenging task; hence, spatial variations in response are not well understood, especially around active faults. Here I analyze previously unutilized records of dynamic strain and pore pressure from regional and teleseismic earthquakes at Plate Boundary Observatory (PBO) stations from 2006 to 2012 to investigate variations in response along the Pacific/North American tectonic plate boundary. I find robust scaling response coefficients between excess pore pressure and dynamic strain at each station that are spatially correlated: around the San Andreas and San Jacinto fault systems, the response is lowest in regions of the crust undergoing the highest rates of secular shear strain. PBO stations in the Parkfield instrument cluster are at comparable distances to the San Andreas Fault (SAF), and spatial variations there follow patterns in dextral creep rates along the fault, with the highest response in the actively creeping section, which is consistent with a narrowing zone of strain accumulation seen in geodetic velocity profiles. At stations in the San Juan Bautista (SJB) and Anza instrument clusters, the response depends nonlinearly on the inverse fault-perpendicular distance, with the response decreasing toward the fault; the SJB cluster is at the northern transition from creeping-to-locked behavior along the SAF, where creep rates are at moderate to low levels, and the Anza cluster is around the San Jacinto Fault, where to date there have been no statistically significant creep rates observed at the surface. These results suggest that the strength of the

  7. Fluid seepage, Deformation, Tectonics and Accretionary Prism Formation in Two Different Settings of the Nankai Accretionary Prism- Dive Results of YK05-08 Leg 2

    NASA Astrophysics Data System (ADS)

    Ogawa, Y. F.; Kawamura, K.; Anma, R.; Yokoyama, S.; Kawakami, S.; Moore, G. F.; Dilek, Y.; S. Y.

    2005-12-01

    Fluid seepages recognized by the presence of bacterial mats, chemosynthetic biocommunities, and carbonate deposits were critically analyzed in relation to large to small scale deformation features in two different settings of the Nankai accretionary prism by the manned submersible Shinkai 6500 during JAMSTEC cruise YK05-08 Leg 2. We present dive profiles in the Shionomisaki and Tenryu submarine canyons that form a 3D transect extending from the outer-arc ridge formed by out-of-sequence thrusts (OOST ridge) to the prism toe. Ten dives in addition to six previous dives (including three unmanned ROV Kaiko dives) verified that Shionomisaki Canyon exposes typical accretionary prism features, including regular repetition of offscraping and underplating structure, whereas Tenryu Canyon shows highly modified structures caused by the collisional subduction of the Paleo-Zenisu ridge of the Izu island arc. The fluid seepages were observed in three different settings: (1) just beneath large thrust faults which demarcate the sharp ridge foot; (2) the open fractured crests of the thrust-anticline folds; and (3) the conspicuous circular expression on the OOST ridge top. The last case and previously known examples in the forearc basin setting are both examples of large scale seepage that might be due to intermittent, sometimes explosive methane seepage, whereas the first two cases are of constant flow rate of smaller magnitude. Such differences may be due to differences in the tectonic setting between the two; the large flow rate example is due to open or strike-slip regime tectonics where large amount of seepage occurs along the high permeability zones. In contrast, the small flow rate example is seepage along a thrust, with rather constant (although intermittent during co-seismic stage) flow rate along thrust faults which are of relatively lower permeability. In addition, we verified some carbonate veins in fractured or sheared rocks along faults, and the various deformation

  8. Geodetic evidence for continuing tectonic activity of the Carboneras fault (SE Spain)

    NASA Astrophysics Data System (ADS)

    Echeverria, Anna; Khazaradze, Giorgi; Asensio, Eva; Masana, Eulalia

    2015-11-01

    The Carboneras fault zone (CFZ) is a prominent onshore-offshore strike-slip fault that forms part of the Eastern Betic Shear Zone (EBSZ), located in SE Spain. In this work, we show for the first time, the continuing tectonic activity of the CFZ and quantify its geodetic slip-rates using continuous and campaign GPS observations conducted during the last decade. We find that the left-lateral motion dominates the kinematics of the CFZ, with a strike-slip rate of 1.3 ± 0.2 mm/yr along the N48° direction. The shortening component is significantly lower and poorly constrained. Recent onshore and offshore paleoseismic and geomorphic results across the CFZ suggest a minimum Late Pleistocene to present-day strike-slip rate of 1.1 mm/yr. Considering the similarity of the geologic and geodetic slip rates measured at different points along the fault, the northern segment of the CFZ must have been slipping approximately at a constant rate during the Quaternary. Regarding the eastern Alpujarras fault zone corridor (AFZ), located to the north of the CFZ, our GPS measurements corroborate that this zone is active and exhibits a right-lateral motion. These opposite type strike-slip motion across the AFZ and CFZ is a result of a push-type force due to Nubia and Eurasia plate convergence, which, in turn, causes the westward escape of the block bounded by these two fault zones.

  9. Active tectonic and magmatic processes beneath Long Valley Caldera, eastern California: an overview ( USA).

    USGS Publications Warehouse

    Hill, D.P.; Bailey, R.A.; Ryall, A.S.

    1985-01-01

    Geological, chronological, and structural studies of the Long Valley-Mono/Inyo Craters area document a long history of related volcanic eruptions and earthquakes controlled by regional extensional tectonics of the Basin and Range province. This activity has persisted for hundreds of thousands of years and is likely to continue. The Long Valley magma chamber had a volume approaching 3000 km3 prior to its climatic caldera-forming eruption 0.7 ma but has been reduced to less than a third of this volume by cooling, eruption, and crystallization. Although current unrest is concentrated in the S moat of Long Valley caldera, the Inyo/Mono Craters probably hold a greater potential for producing an eruption in the foreseeable future. The Inyo/Mono Craters have erupted at 500-year intervals over the past 2000-3000 years, whereas the Long Valley magma chamber has erupted at about 200,000-year intervals over the past 700,000 years. In either case, a major earthquake near the caldera could strongly influence the course of volcanic activity.-from Authors

  10. Peculiar Active-Tectonic Landscape Within the Sanctuary of Zeus at Mt. Lykaion (Peloponnese, Greece)

    NASA Astrophysics Data System (ADS)

    Davis, G. H.

    2008-12-01

    The Sanctuary of Zeus (Mt. Lykaion) lies in the Peloponnese within the Pindos fold and thrust belt. It is the object of investigation of the Mt. Lykaion Excavation and Survey (http://lykaionexcavation.org/). Mt. Lykaion is a thrust klippe, on the summit of which is an upper sanctuary marked by an ash altar, temenos, and column bases. Earliest objects recovered from the ash altar go back to 3000 BCE, leading Dr. David Romano (University of Pennsylvania), a principal leader of the project, to conclude that worship of divinities on the summit is ancient. Detailed structural geological mapping reveals one dimension of the "power" of the site. Crisscrossing the upper sanctuary are scree bands that mark the traces of active normal faults, which are expressions of tectonic stretching of the Aegean region. The scree bands, composed of cinder-block-sized limestone blocks, range up to 10 m in outcrop breadth, 100 m in length, and 5 m in thickness. Though discontinuous, most of the scree bands lie precisely on the traces of through-going faults, which cut and displace the sedimentary formations of the Pindos group. Some cut the thrust fault, whose elliptical trace defines the Lykaion klippe. What makes the scree bands of this active-tectonic landscape "peculiar" is that there are no cliffs from which the scree descends. Rather, the bands of scree occur along flanks of smooth, rounded hillslopes and ridges. The scree bands coincide with modest steps in the topography, ranging from tens of centimeters to several tens of meters. The specific bedrock formation where the bands are best developed is an Upper Cretaceous limestone whose average platy-bedding thickness (approximately 20 cm) matches closely the average joint spacing. The limestone has little mechanical integrity. It cannot support itself as a scarp footwall and instead collapses into a pile of scree, whose upper-surface inclination conforms to a stable angle of repose. Evidence of the contemporary nature of this

  11. Geomorphic impacts of active tectonics on a river course, the case of Klissoura gorge, central Greece.

    NASA Astrophysics Data System (ADS)

    Tsanakas, Konstantinos; Fubelli, Giandomenico; Karymbalis, Efthimios

    2014-05-01

    The delicate balance of the natural processes within the river systems can be easily tipped making them very sensitive to changes occurring on the earth surface. Fluvial systems are therefore profoundly influenced by endogenic processes such as active tectonics as well as global sea level fluctuations following the climatic variations during the Quaternary. This study deals with the geomorphological evolution of the broader area of the abandoned gorge of Klissoura which is located in central Greece. This 130 m deep and roughly 3 km long gorge is a characteristic example of an old drainage course preserved on the footwall blocks of two normal faults which confine both outlets of the deeply incised valley. The gorge has formed by a river that once had a N-S flow direction discharging into the Gulf of Patras. Acheloos River and the much smaller Ermitza Remma Stream are the two recent primary watercourses which drain the area close to the abandoned gorge. Both the dimensions and morphological characteristics of the abandoned deep valley indicate that the gorge has formed by a large river with high discharge in order to incise into the limestone bedrock. In order to investigate the tectonic constrains and determine the geomorphic and climatic processes that compelled the lower reaches of Acheloos River to abandon the gorge and find an outlet following its present course a GIS based analysis at a scale of 1:50.000 was applied in the drainage basin of Acheloos River. Additionally, to reconstruct the palaeolandscape and the earth surface processes, a detailed morphometric and geomorphic analysis of the abandoned gorge was also performed at a scale of 1:5.000 coupled with field observations and stratigraphic analysis of the deposits outcropping on the valley sides within the gorge as well as on both outlets. The geomorphic analysis led to the conclusion that the primary course of the gorge abandonment and diversion and reverse of the drainage is the uplift of the footwall

  12. Provenance and sediment-dispersal system in tectonically active rapidly evolving foreland basin, Western Interior

    SciTech Connect

    Khandaker, N.I.; Vondra, C.F.

    1989-03-01

    The Upper Cretaceous Frontier Formation, along the mobile edge of the Western Interior foreland basin, is composed mainly of clastic sediments and was deposited during the initial Late Cretaceous transgressive-regressive phases of the Western Interior seaway across Wyoming. The formation contains many persistent bentonite beds and several sandstone packages in its lower part and a thin, lenticular lithic wacke-polymictic conglomerate association at its upper contact (Torchlight Sandstone Member). Abundant granule to cobble-sized clasts of andesite, granite, chert, and quartzite are set in a poorly sorted sand-to-granule grade volcaniclastic matrix. There is a lithologic continuity of this volcaniclastic unit across the Bighorn Mountains into the Powder River basin. A high-energy distributary complex of sizable areal extent is invoked for the deposition of this linear conglomerate facies. Geochemical investigations of the whole-rock andesite clasts and bentonite allowed more precise definition of character, tectonic setting, and evolutionary stages of sedimentary distributive provinces. Bentonites and andesites are strongly enriched in strontium and barium, but only mildly enriched in heavy rare earth elements and high field-strength elements. These analyzed rocks have trace element characteristics similar in a general way to those of typical orogenic volcanics; they show some significant differences in detail. Composition of volcaniclasts and paleocurrent data indicate a proximal sediment source for the extrabasinal detritus within the Frontier Formation. The possibility of a contribution from a Mesozoic volcanic center in the neighborhood of southwestern Montana is strongly favored. The products of this volcanism constitute an assemblage of deep crustal to mantle( ) derived rocks, and their composition record time-integrated enrichment in light over heavy rare earth elements.

  13. Geochemistry of the Cretaceous coals from Lamja Formation, Yola Sub-basin, Northern Benue Trough, NE Nigeria: Implications for paleoenvironment, paleoclimate and tectonic setting

    NASA Astrophysics Data System (ADS)

    Sarki Yandoka, Babangida M.; Abdullah, Wan Hasiah; Abubakar, M. B.; Hakimi, Mohammed Hail; Adegoke, Adebanji Kayode

    2015-04-01

    The Cretaceous coals of Lamja Formation located in Yola Sub-basin of the Northern Benue Trough, northeastern Nigeria, were analyzed based on a combined investigation of organic and inorganic geochemistry to define the paleodepositional environment condition, organic matter source inputs and their relation to paleoclimate and tectonic setting. The total organic carbon and sulfur contents of Lamja Formation coals ranges from 48.2%-67.8% wt.% and 0.42%-0.76% wt.%, respectively, pointing their deposition in freshwater environment with inferred marine influence during burial. Biomarkers and chemical compositions provide evidence for a major contribution of land-derived organic matter, with minor aquatic organic matter input. Minerals such as quartz, pyrite, kaolinite, illite, montmorillonite and calcite were present in the coals, suggesting that these minerals were sourced from terrigenous origin with slightly marine influence, considered as post-depositional. This is consistent with a significant amount of the oxides of major elements such as SiO2, Fe2O3, Al2O3, TiO2, CaO, and MgO. The investigated biomarkers are characterized by dominant odd carbon numbered n-alkanes (n-C23 to n-C33), moderately high Pr/Ph ratios (1.72-3.75), very high Tm/Ts ratios (18-29), and high concentrations of regular sterane C29, indicating oxic to relatively suboxic conditions, delta plain marine environment of deposition with prevalent contribution of land plants and minor aquatic organic matter input. Concentrations of trace elements such as Ba, Sr, Cr, Ni, V, Co and their standard ratios also suggested that the organic matter was deposited under oxic to relatively suboxic conditions, which is in parts deposited under marine influenced. Some standard binary plots of SiO2 versus (Al2O3 + K2O + Na2O) indicate a semi-arid paleoclimatic condition whereas log SiO2 versus (K2O/Na2O) also revealed passive continental margin setting. The inferred tectonic setting is in agreement with the tectonic

  14. Active tectonics of the Ganzi-Yushu fault in the southeastern Tibetan Plateau

    NASA Astrophysics Data System (ADS)

    Shi, Feng; He, Honglin; Densmore, Alexander L.; Li, An; Yang, Xiaoping; Xu, Xiwei

    2016-04-01

    The ongoing convergence between India and Eurasia apparently is accommodated not merely by crustal shortening in Tibet, instead also by motions along strike slip faults which are usually boundaries between tectonic blocks, especially in the Tibetan Plateau. Quantification of this strike slip faulting is fundamental for understanding the collision between India and Eurasia. Here, we use a variety of geomorphic observations to place constraints on the late Quaternary kinematics and slip rates of the Ganzi-Yushu fault, one of the significant strike-slip faults in eastern Tibet. The Ganzi-Yushu fault is an active, dominantly left-lateral strike-slip structure that can be traced continuously for up to 500 km along the northern boundary of the clockwise-rotating southeastern block of the Tibetan Plateau. We analyse geomorphic evidence for deformation, and calculate the late Quaternary slip rates at four sites along the eastern portion of the fault trace. The latest Quaternary apparent throw rates are variable along strike but are typically ~ 1 mm/a. Rates of strike-slip displacement are likely to be an order of magnitude higher, 8-11 mm/a. Trenching at two locations suggests that the active fault behaviour is dominated by strike-slip faulting and reveals several earthquake events with refined information of timing. The 2010 Mw 6.9 Yushu earthquake, which occurred on the northwestern segment of the Ganzi-Yushu fault zone, provides additional evidence for fault activity. These observations agree with GPS-derived estimates, and show that late Quaternary slip rates on the Ganzi-Yushu fault are comparable to those on other major active strike-slip faults in the eastern Tibetan Plateau.

  15. Geochronology and Geochemistry of Volcanic Suites from the Middle Sulu Orogenic Belt, Eastern China: Implication for Petrogenesis and Tectonic Setting

    NASA Astrophysics Data System (ADS)

    Wang, J.; Chang, S. C.; Lu, H.; Zhang, H.

    2014-12-01

    The widely distributed Late Mesozoic igneous events in North China have been intensively studied in the past decades and proposed to be accounted by lithospheric thinning. However, mechanism of the lithospheric thining is still in debate. In this study, we report U-Pb zircon ages, geochemical data and Sr-Nd isotopic data for the Cretaceous mafic and associated felsic intrusions from the middle Sulu orogenic belt in the Shandong Peninsula. The ICP-MS U-Pb zircon analyses show consistent crystallization ages ranging from 120.2 ± 2.1 Ma to 123.3 ± 1.6 Ma for four representative samples. These rocks are characterized by LREE and LILE enrichment, HREE depletion, high initial 87Sr/86Sr values ranging from 0.70401 to 0.70966, low negative ɛNd(t) values from -22.0 to -12.2. These features suggest that they were derived from a common enriched lithospheric mantle source. Geochemical and isotopic data indicate that the original magma of these rocks was produced by partial melting of an ancient lithospheric mantle, which was variably mixed with lower crustal eclogite derived melts. The lamprophyres, andesitic porphyrites and syenogranite may have been attributed to subsequent fractional crystallization of olivine and pyroxene, whereas the rhyolite resulted from K-feldspar and plagioclase fractionation, without any crustal contamination affection. Tectonically, the petrogenesis process of these rocks favors an intense lithospheric extensional regime beneath the Sulu orogenic belt at 120 ~ 124 Ma, which was resulted by the widespread removal of the upper mantle and lower crust that driven by the abrupt change of the subducting direction of the Pacific plate.

  16. Depositional architecture, provenance and tectonic setting of Miocene submarine fans in the Shikoku Basin: Results from IODP Expedition 322

    NASA Astrophysics Data System (ADS)

    Pickering, K. T.; Underwood, M.; Saito, S.; Naruse, H.; Kutterolf, S.; Scudder, R. P.; Park, J.; Moore, G. F.; Slagle, A. L.

    2012-12-01

    Seismo-stratigraphy, coring and logging while drilling (LWD) during IODP Expedition 322 (Sites C0011 and C0012) show that three submarine fans accumulated in the NE Shikoku Basin during the Miocene. Regional comparisions with ODP Site 1177 (seaward margin of Nankai Trough) and DSDP Site 297 (NW Shikoku Basin) reveal sandy deposits that are broadly contemporaneous. The oldest (and finer-grained) fan has a sheet-like geometry, and petrographic data suggest that quartz-rich sediment gravity flows traveled toward the southwest from a source on the ancestral Kyushu-Shikoku landmass. During a time of hemipelagic deposition at C0011-C0012, turbidites continued to accumulate at Sites 1177 and 297. Sand delivery to the Shikoku Basin was disrupted when a phase of sinistral strike-slip motion cut off canyon pathways. The intermediate fan (Zenisu Daiichi) at ~10 Ma is characterized by channel elements that routed sand into a more proximal, middle-fan environment. The youngest fan (Zenisu Daini) also has sheet-like geometry but with thick-bedded and coarse-grained pumiceous sandstones. The pumice fragments were transported from a mixed provenance that included the collision zone of the Izu-Bonin and Honshu arcs. The change from channelized to sheet-like flows occurred at ~8 Ma. At that time, renewal of relatively rapid northward subduction evidently favored axial flows in a bathymetric trench, with some overspill by large-volume events. The times of significant sand influx also coincided with long-term falls in eustatic sea level, as inferred from oxygen-isotope curves. Thus, global climate change amplified the effects of local tectonics in modulating sediment delivery to the Shikoku Basin.

  17. Teleseismic P and S Delay Times within Tectonically Active and Stable North America

    NASA Astrophysics Data System (ADS)

    Lou, X.; van der Lee, S.

    2009-12-01

    We have measured teleseismic P and S relative delay times within 1) Stable North America (SNA) using waveforms from IRIS PASSCAL seismic arrays MOMA (Fischer et al., 1995), ABBA (Roecker and Beavan, 1995), Abitibi (Hearn and Mareschal, 1996), and FLED (Wysession and Fischer, 2001), and 2) Tectonically-active North America (TNA) using Earthscope's Transportable Array (TA). To study the contribution of mantle structure to these delays we subtracted delays predicted for topography and crustal structure, using CRUST 2.0 (Bassin et al., 2000). Preliminary analyses of delay times from earthquakes with Mw>=6.5 show surprising differences between the heterogeneity of the mantle beneath SNA and TNA. While the range of delay times is expectedly small for an intra-shield array such as Abitibi, the range of delay times from Proterozoic basement in the midwest to Paleozoic margin in New England is much larger and slightly exceeds that for the TA in TNA. This suggests that that the mantle of SNA is slightly more heterogeneous than TNA, despite there being relatively little surface expression of this heterogeneity. Patterns of P and S relative delay times measured in TNA correlate better with surface tectonics, suggesting that the mantle in TNA has a greater effect on the surface geology than in SNA. The central and southern Basin and Range are characterized by positive delays. As shown in previous studies, the Snake River Plain is also well delineated by positive delays. These delays exhibit a significant peak at station H17A in Yellowstone National Park. Teleseismic P and S waves arriving at stations in the Rocky Mountains are much faster, including in northern Idaho and western Washington, but not in western Oregon. For both SNA and TNA, the measured S and P delay times have a significant linear correlation, with S delays at approximately 3 times the P delays, which confirms the dominant effect of mantle temperature on mantle velocity structure. However, the slope of this

  18. Analyzing the drainage system anomaly of Zagros basins: Implications for active tectonics

    NASA Astrophysics Data System (ADS)

    Bahrami, Shahram

    2013-11-01

    tectonic activities.

  19. Relative earthquake location for remote offshore and tectonically active continental regions using surface waves

    NASA Astrophysics Data System (ADS)

    Cleveland, M.; Ammon, C. J.; Vandemark, T. F.

    2015-12-01

    Earthquake locations are a fundamental parameter necessary for reliable seismic monitoring and seismic event characterization. Within dense continental seismic networks, event locations can be accurately and precisely estimated. However, for many regions of interest, existing catalog data and traditional location methods provide neither accurate nor precise hypocenters. In particular, for isolated continental and offshore areas, seismic event locations are estimated primarily using distant observations, often resulting in inaccurate and imprecise locations. The use of larger, moderate-size events is critical to the construction of useful travel-time corrections in regions of strong geologic heterogeneity. Double difference methods applied to cross-correlation measured Rayleigh and Love wave time shifts are an effective tool at providing improved epicentroid locations and relative origin-time shifts in these regions. Previous studies have applied correlation of R1 and G1 waveforms to moderate-magnitude vertical strike-slip transform-fault and normal faulting earthquakes from nearby ridges. In this study, we explore the utility of phase-match filtering techniques applied to surface waves to improve cross-correlation measurements, particularly for smaller magnitude seismic events. We also investigate the challenges associated with applying surface-wave location methods to shallow earthquakes in tectonically active continental regions.

  20. Active tectonics of northwestern U.S. inferred from GPS-derived surface velocities

    SciTech Connect

    Robert McCaffrey; Robert W. King; Suzette J. Payne; Matthew Lancaster

    2013-02-01

    Surface velocities derived from GPS observations from 1993 to 2011 at several hundred sites across the deforming northwestern United States are used to further elucidate the region's active tectonics. The new velocities reveal that the clockwise rotations, relative to North America, seen in Oregon and western Washington from earlier GPS observations, continue to the east to include the Snake River Plain of Idaho and south into the Basin and Range of northern Nevada. Regional-scale rotation is attributed to gravitationally driven extension in the Basin and Range and Pacific-North America shear transferred through the Walker Lane belt aided by potentially strong pinning below the Idaho Batholith. The large rotating section comprising eastern Oregon displays very low internal deformation rates despite seismological evidence for a thin crust, warm mantle, organized mantle flow, and elevated topography. The observed disparity between mantle and surface kinematics suggests that either little stress acts between them (low basal shear) or that the crust is strong relative to the mantle. The rotation of the Oregon block impinges on Washington across the Yakima fold-thrust belt where shortening occurs in a closing-fan style. Elastic fault locking at the Cascadia subduction zone is reevaluated using the GPS velocities and recently published uplift rates. The 18 year GPS and 80 year leveling data can both be matched with a common locking model suggesting that the locking has been stable over many decades. The rate of strain accumulation is consistent with hundreds of years between great subduction events.

  1. Evaluation of Ground-Motion Modeling Techniques for Use in Global ShakeMap - A Critique of Instrumental Ground-Motion Prediction Equations, Peak Ground Motion to Macroseismic Intensity Conversions, and Macroseismic Intensity Predictions in Different Tectonic Settings

    USGS Publications Warehouse

    Allen, Trevor I.; Wald, David J.

    2009-01-01

    Regional differences in ground-motion attenuation have long been thought to add uncertainty in the prediction of ground motion. However, a growing body of evidence suggests that regional differences in ground-motion attenuation may not be as significant as previously thought and that the key differences between regions may be a consequence of limitations in ground-motion datasets over incomplete magnitude and distance ranges. Undoubtedly, regional differences in attenuation can exist owing to differences in crustal structure and tectonic setting, and these can contribute to differences in ground-motion attenuation at larger source-receiver distances. Herein, we examine the use of a variety of techniques for the prediction of several ground-motion metrics (peak ground acceleration and velocity, response spectral ordinates, and macroseismic intensity) and compare them against a global dataset of instrumental ground-motion recordings and intensity assignments. The primary goal of this study is to determine whether existing ground-motion prediction techniques are applicable for use in the U.S. Geological Survey's Global ShakeMap and Prompt Assessment of Global Earthquakes for Response (PAGER). We seek the most appropriate ground-motion predictive technique, or techniques, for each of the tectonic regimes considered: shallow active crust, subduction zone, and stable continental region.

  2. Taiwan: a perfect field trip to study active tectonics and erosion processes

    NASA Astrophysics Data System (ADS)

    Bigot-Cormier, Florence; Beauval, Véronique; Martinez, Claire-Marie; Seyeux, Jana

    2014-05-01

    Taiwan is located at the boundary between the Philippine Sea Plate to the East and the Eurasian Plate to the West. This plate boundary is rather complex since it comprises two subduction zones of reverse polarities. Due to this specific geodynamic context, this field is a perfect area to answer the French program in 5th grade (erosion processes) and 4th grade (active tectonics) in Earth Science class. That's why for the second year, students from the Lycée Français de Shanghai (LFS) in 4th grade will go for a 4-day field trip to discover volcanoes (in the Yangminshan National Park) and para-seismic constructions in the 101 Tower at Taipei. It will remind them the program of their previous class (5ème) through the visit of Yehliu Geographic Park and some other areas in the North of the Island where they will be able to observe different erosion processes (wind or water) carving the landscape. The aim of this field trip is first to show them that Earth Sciences cannot be studied only in class but also on the field to get a better understanding of the processes. In this manner, after having understood the internal thermal system of our Earth in class, they will see its manifestations on the surface of the Earth, by seeing an active explosive volcano with gas ejection, specific mineralization, and hot springs. Furthermore on the field, they will be able to do a link between the external and internal geodynamics processes usually studied separately in middle school. The poster presented will detail the first field trip in Taiwan realized in May 2013 by the LFS 4th grade students and will be made by the students going in June 2014. Thus, this activity will allow them to get a perspective of the topic that they will discover on the field trip.

  3. Origin and depositional setting of pre-Devonian, coarse-clastic sequences in the central Transantarctic Mountains: Evidence of one or more tectonic events

    SciTech Connect

    Rees, M.N. )

    1987-09-01

    The Transantarctic Mountains extend over 4,000 kilometers between the Weddell and Ross seas and form the western boundary of the east antarctic craton. Within the mountain chain and in the Ellsworth Mountains in West Antarctica, Upper Proterozoic and Lower Paleozoic rocks crop out in isolated areas. From regional mapping and some detailed studies geologists have shown that generally these areas have similar geologic histories, but these studies also have indicated that differences in stratigraphy and structure exist. The study focuses on two sequences of conglomerate and sandstone, one in the central Transantarctic Mountains and the other in northern Victoria Land. The similarity in stratigraphy of the clastic sequences in these areas suggests that a genetic relationship may exist between the two geographically widespread areas. To improve the understanding of the tectonic and geologic history of rocks in these areas, the authors will analyze facies to establish the depositional settings, evaluate the sediment composition to ascertain the lithologies and ages of the source areas, determine ages of interbedded volcanic rocks, collect fossils from fine-grained sedimentary units to establish the age of deposition, and examine the relationship between the coarse-clastic sequences and underlying formations. From these data, he will try to determine if the tectonic setting that controlled the origin and distribution of the sequences later deformed them. If he can determine that there is a genetic relationship between the coarse-clastic rocks of the Bowers terrane and those in the central Transantarctic Mountains, these data will greatly modify scientific understanding of the lower Paleozoic development of the western continental margin of Antarctica and perhaps of Gondwana.

  4. Mesozoic tectonic setting of rift basins in eastern North China and implications for destruction of the North China Craton

    NASA Astrophysics Data System (ADS)

    Qi, Guo-wei; Zhang, Jin-Jiang; Wang, Meng

    2015-11-01

    Destruction of the North China Craton (NCC) in the Mesozoic due to subduction of the Paleo-Pacific Plate has attracted a lot of recent interest, with numerous studies focusing on regional tectonics and associated magmatism. Although the peak ages for this event have been established, the timing of its initiation remains poorly understood. In this paper, two rift basins in the northern Hebei Province of China, the Diaoe Basin (DB) and Houcheng Basin (HB), are studied in order to constrain the timing of destruction of the northern margin of the NCC. Both NNE-striking basins developed on Proterozoic basement. The DB is a graben controlled by normal faults on its two margins, and the HB is a half-graben bounded by normal faults on its eastern side. Basin fills include detrital sediments and volcanic rocks, which are (from bottom to top) the Houcheng Formation (Fh), the Zhangjiakou Formation (Fzh), the Shijiayao Formation (Fs), and the Huajiying Formation (Fhj). The Fh is composed mainly of detrital sediments interlayered with andesite in its lower section, and interlayered with felsic volcanics (rhyolite) in its upper section. There exists a transitional change from the Fh to the thick felsic volcanic strata of the Fzh. Geochemically, the andesite layers in the lower Fh were most likely derived from mixing of crust and mantle melts, whereas the felsic rocks were derived from melting of the lower crust. U-Pb dating of zircons by LA-ICP-MS yielded ages for the lower Fh andesites of ca. 165.7 Ma in the HB and ca. 157.4 Ma in the DB. The felsic rocks at the base of the Fzh yielded ages of ca. 155.1 Ma in the HB and ca. 149.2-143.4 Ma in the DB. The Fs and Fhj in the DB both yielded similar ages of ca. 136 Ma. The development of rift basins, together with the occurrence of massive felsic volcanic rocks, indicates a period of significant extension and thinning of the NCC. The ca. 165.7-155.1 Ma age for andesites not only represents the initial timing of crustal extension

  5. Alternating thin versus thick-skinned decollements, example in a fast tectonic setting: The Misool-Onin-Kumawa Ridge (West Papua)

    NASA Astrophysics Data System (ADS)

    Sapin, F.; Pubellier, M.; Ringenbach, J.-C.; Bailly, V.

    2009-04-01

    The Misool-Onin-Kumawa Ridge (Eastern Indonesia) is a broad anticline in the lower plate of the Seram subduction system. In the south it lies between the Seram accretionary wedge and the young Lengguru fold-and-thrust belt (<8 My). A large seismic dataset from recent petroleum exploration in the area allows the ridge to be interpreted as the result of a dual system of thin-skinned and thick-skinned tectonics. A forebulge effect may be superimposed on the emergent sections of the ridge (Onin and Kumawa Domes), where the morphology has been reactivated. The evolution results from what appears to be a continuum of deformation through three major stages: (1) formation of a Messinian thin-skinned fold-and-thrust belt over a shaly-silty Permian-Paleocene unit; (2) a Pliocene thick-skinned event responsible for the uplift of the ridge, possibly induced by the onset of continental subduction; and (3) recent Pleistocene deformation when thin-skinned tectonics resumed in the Seram Trough. Currently, the Seram wedge abuts the ridge, transferring compression northward into the Salawati Basin. The jumps of active detachment levels may be a response to changes in subduction parameters (velocity, rugosity, etc.) during the transition between oceanic and continental subduction, or at least from thinned crust to thicker continental crust.

  6. Architecture and evolution of an Early Permian carbonate complex on a tectonically active island in east-central California

    USGS Publications Warehouse

    Stevens, Calvin H.; Magginetti, Robert T.; Stone, Paul

    2015-01-01

    The newly named Upland Valley Limestone represents a carbonate complex that developed on and adjacent to a tectonically active island in east-central California during a brief interval of Early Permian (late Artinskian) time. This lithologically unique, relatively thin limestone unit lies within a thick sequence of predominantly siliciclastic rocks and is characterized by its high concentration of crinoidal debris, pronounced lateral changes in thickness and lithofacies, and a largely endemic fusulinid fauna. Most outcrops represent a carbonate platform and debris derived from it and shed downslope, but another group of outcrops represents one or possibly more isolated carbonate buildups that developed offshore from the platform. Tectonic activity in the area occurred before, probably during, and after deposition of this short-lived carbonate complex.

  7. Seismic hazard assessment of Syria using seismicity, DEM, slope, active tectonic and GIS

    NASA Astrophysics Data System (ADS)

    Ahmad, Raed; Adris, Ahmad; Singh, Ramesh

    2016-07-01

    In the present work, we discuss the use of an integrated remote sensing and Geographical Information System (GIS) techniques for evaluation of seismic hazard areas in Syria. The present study is the first time effort to create seismic hazard map with the help of GIS. In the proposed approach, we have used Aster satellite data, digital elevation data (30 m resolution), earthquake data, and active tectonic maps. Many important factors for evaluation of seismic hazard were identified and corresponding thematic data layers (past earthquake epicenters, active faults, digital elevation model, and slope) were generated. A numerical rating scheme has been developed for spatial data analysis using GIS to identify ranking of parameters to be included in the evaluation of seismic hazard. The resulting earthquake potential map delineates the area into different relative susceptibility classes: high, moderate, low and very low. The potential earthquake map was validated by correlating the obtained different classes with the local probability that produced using conventional analysis of observed earthquakes. Using earthquake data of Syria and the peak ground acceleration (PGA) data is introduced to the model to develop final seismic hazard map based on Gutenberg-Richter (a and b values) parameters and using the concepts of local probability and recurrence time. The application of the proposed technique in Syrian region indicates that this method provides good estimate of seismic hazard map compared to those developed from traditional techniques (Deterministic (DSHA) and probabilistic seismic hazard (PSHA). For the first time we have used numerous parameters using remote sensing and GIS in preparation of seismic hazard map which is found to be very realistic.

  8. Analysis of Landsat TM data for active tectonics: the case of the Big Chino Fault, Arizona

    NASA Astrophysics Data System (ADS)

    Salvi, Stefano

    1994-12-01

    The Big Chino Valley is a 50 km-long tectonic depression of the Basin and Range province of the South- western United States. It is bordered on the NE side by an important normal fault, the Big Chino Fault. The activity of the latter has been hypothesised on the basis of the presence of a 20 m-high fault scarp and on local geomorphological studies. Moreover, a magnitude 4.9 earthquake occurred in southern Arizona in 1976 has been attributed to this fault. The climate in the Big Chino Valley is semi-arid with average rainfall of about 400 mm per year; a very sparse vegetation cover is present, yielding a good possibility for the geo-lithologic application of remote sensing data. The analysis of the TM spectral bands shows, in the short wave infrared, a clear variation in the reflected radiance across the fault scarp. Also the available radar (SLAR) images show a marked difference in response between the two sides of the fault. An explanation of this phenomena has been found in the interaction between the geomorphic evolution, the pedological composition, and the periodic occurrence of coseismic deformation along the fault. Other effects of the latter process have been investigated on colour D- stretched images whose interpretation allowed to detect two paleoseismic events of the Big Chino Fault. This work demonstrates that important information on the seismological parameters of active faults in arid and semiarid climates can be extracted from the analysis of satellite spectral data in the visible and near -infrared.

  9. Erosional flux from tectonically active landscapes: Case studies from Southern Italy

    NASA Astrophysics Data System (ADS)

    Roda-Boluda, Duna; D'Arcy, Mitch; Whittaker, Alex; Allen, Philip; Gheorghiu, Delia; Rodes, Angel

    2016-04-01

    Erosion and sediment supply are fundamentally important controls on landscape evolution, governing the denudation of relief, the stratigraphy deposited in basins, and the ultimate destruction of orogens. However, quantifying the rates, timescales, and predominant processes of erosion remains a major challenge in many tectonically active areas. Here, we use Southern Italy as a case study to demonstrate how these challenges can be overcome. We present 15 new 10Be catchment-averaged erosion rates, for systems distributed along 5 active normal faults for which we have excellent constraints on throw rates along strike and uplift history. These footwall catchments have a total relief of up to 1800 m and throw rates up to 1.4 mm/yr. We show that sediment supply estimates based on the 10Be erosion rates agree well with sediment supply predictions based on the fault throw profiles. Our results suggest that about 80% of the material uplifted by the faults is being eroded at a similar magnitude to the fault throw rates, offering new insights into the topographic balance of uplift and erosion in this area. These findings imply that active normal faulting is the primary control on sediment supply in Southern Italy. Our field observations suggest that landslides are an important source of sediment in our study area, and are largely driven by incision in response to fault activity. Using a field-calibrated landslide inventory, we estimate landslide-derived sediment flux for our sampled catchments. These estimates correlate well with total sediment flux estimates, demonstrating quantitatively that landslides must be a major source of sediment. Their erosional signal is adequately captured by the 10Be analyses most likely because of the high frequency of small landslides and their high spatial density in these catchments (typically >10% of the total area), which ensures sufficient sediment mixing. Finally, we use our results to calibrate the BQART model of sediment supply, enabling

  10. Stratigraphic and tectonic settings of Proterozoic glaciogenic rocks and banded iron-formations: relevance to the snowball Earth debate

    NASA Astrophysics Data System (ADS)

    Young, Grant M.

    2002-11-01

    Among Palaeoproterozoic glacial deposits on four continents, the best preserved and documented are in the Huronian on the north shore of Lake Huron, Ontario, where three glaciogenic formations have been recognized. The youngest is the Gowganda Formation. The glacial deposits of the Gowganda Formation were deposited on a newly formed passive margin. To the west, on the south side of Lake Superior, the oldest Palaeoproterozoic succession (Chocolay Group) begins with glaciogenic diamictites that have been correlated with the Gowganda Formation. The >2.2 Ga passive margin succession (Chocolay Group=upper Huronian) is overlain, with profound unconformity, by a >1.88 Ga succession that includes the superior-type banded iron-formations (BIFs). The iron-formations are therefore not genetically associated with Palaeoproterozoic glaciation but were deposited ˜300 Ma later in a basin that formed as a result of closure of the "Huronian" ocean. In Western Australia, Palaeoproterozoic glaciogenic deposits of the Meteorite Bore Member appear to have formed part of a similar basin fill. The glaciogenic rocks are, however, separated from underlying BIF by a thick siliciclastic succession. In both North America and Western Australia, BIF-deposition took place in compressional (possibly foreland basin) settings but the iron-formations are of greatly different age, suggesting that the most significant control on their formation was not oxygenation of the Earth's atmosphere but rather, emplacement of Fe-rich waters (uplifted as a result of ocean floor destruction?) in a siliciclastic-starved environment where oxidation (biogenic?) could take place. Some of the Australian BIFs appear to predate the appearance of red beds in North American Palaeoproterozoic successions and are therefore unlikely to be related to oxygenation of the atmosphere. Neoproterozoic glaciogenic deposits are widespread on the world's continents. Some are associated with iron-formations. Two theories have emerged

  11. Seismic body wave separation in volcano-tectonic activity inferred by the Convolutive Independent Component Analysis

    NASA Astrophysics Data System (ADS)

    Capuano, Paolo; De Lauro, Enza; De Martino, Salvatore; Falanga, Mariarosaria; Petrosino, Simona

    2015-04-01

    One of the main challenge in volcano-seismological literature is to locate and characterize the source of volcano/tectonic seismic activity. This passes through the identification at least of the onset of the main phases, i.e. the body waves. Many efforts have been made to solve the problem of a clear separation of P and S phases both from a theoretical point of view and developing numerical algorithms suitable for specific cases (see, e.g., Küperkoch et al., 2012). Recently, a robust automatic procedure has been implemented for extracting the prominent seismic waveforms from continuously recorded signals and thus allowing for picking the main phases. The intuitive notion of maximum non-gaussianity is achieved adopting techniques which involve higher-order statistics in frequency domain., i.e, the Convolutive Independent Component Analysis (CICA). This technique is successful in the case of the blind source separation of convolutive mixtures. In seismological framework, indeed, seismic signals are thought as the convolution of a source function with path, site and the instrument response. In addition, time-delayed versions of the same source exist, due to multipath propagation typically caused by reverberations from some obstacle. In this work, we focus on the Volcano Tectonic (VT) activity at Campi Flegrei Caldera (Italy) during the 2006 ground uplift (Ciaramella et al., 2011). The activity was characterized approximately by 300 low-magnitude VT earthquakes (Md < 2; for the definition of duration magnitude, see Petrosino et al. 2008). Most of them were concentrated in distinct seismic sequences with hypocenters mainly clustered beneath the Solfatara-Accademia area, at depths ranging between 1 and 4 km b.s.l.. The obtained results show the clear separation of P and S phases: the technique not only allows the identification of the S-P time delay giving the timing of both phases but also provides the independent waveforms of the P and S phases. This is an enormous

  12. Detrital modes of the Pyeongan Supergroup (Late Carboniferous Early Triassic) sandstones in the Samcheog coalfield, Korea: implications for provenance and tectonic setting

    NASA Astrophysics Data System (ADS)

    Lee, Yong Il; Sheen, Dong-Hee

    1998-08-01

    Medium to coarse sandstones of the Carboniferous to Early Triassic Pyeongan Supergroup in the Samcheog coalfield, Korea, were studied to infer the provenance and tectonic settings of the source areas. Sandstone detrital modes change upwards stratigraphically. Sandstone types from the Manhang to Dosagog formations low to middle in the sequence are quartzarenite, and sublitharenite to litharenite, whereas sandstones of the Gohan and Donggo formations high in the sequence are feldspathic litharenite and arkose, respectively. Using various ternary diagrams, the provenance of the Manhang to Gohan formations is suggested to be a recycled orogen setting. Some Gohan Formation sandstones plot within the arc-related setting field, and the Donggo Formation sandstones plot within both continental block and recycled orogen fields. Results of quartz grain petrography are consistent with those of detrital modes. Quartz in sandstones of all units except the Donggo Formation indicates derivation from low-rank metamorphic sources. Quartz in Donggo sandstones was derived from medium- to high-rank metamorphic and plutonic source rocks. Considering the sandstone composition and palaeocurrent data, the Pyeongan Supergroup probably was deposited in a molasse foreland basin and was derived from a synbasinal orogenic belt, probably the Akiyoshi orogen located in southwest Japan.

  13. Glacier Ice Mass Fluctuations and Fault Instability in Tectonically Active Southern Alaska

    NASA Technical Reports Server (NTRS)

    SauberRosenberg, Jeanne M.; Molnia, Bruce F.

    2003-01-01

    Across southern Alaska the northwest directed subduction of the Pacific plate is accompanied by accretion of the Yakutat terrane to continental Alaska. This has led to high tectonic strain rates and dramatic topographic relief of more than 5000 meters within 15 km of the Gulf of Alaska coast. The glaciers of this area are extensive and include large glaciers undergoing wastage (glacier retreat and thinning) and surges. The large glacier ice mass changes perturb the tectonic rate of deformation at a variety of temporal and spatial scales. We estimated surface displacements and stresses associated with ice mass fluctuations and tectonic loading by examining GPS geodetic observations and numerical model predictions. Although the glacial fluctuations perturb the tectonic stress field, especially at shallow depths, the largest contribution to ongoing crustal deformation is horizontal tectonic strain due to plate convergence. Tectonic forces are thus the primary force responsible for major earthquakes. However, for geodetic sites located < 10-20 km from major ice mass fluctuations, the changes of the solid Earth due to ice loading and unloading are an important aspect of interpreting geodetic results. The ice changes associated with Bering Glacier s most recent surge cycle are large enough to cause discernible surface displacements. Additionally, ice mass fluctuations associated with the surge cycle can modify the short-term seismicity rates in a local region. For the thrust faulting environment of the study region a large decrease in ice load may cause an increase in seismic rate in a region close to failure whereas ice loading may inhibit thrust faulting.

  14. Tectonic Plate Movement.

    ERIC Educational Resources Information Center

    Landalf, Helen

    1998-01-01

    Presents an activity that employs movement to enable students to understand concepts related to plate tectonics. Argues that movement brings topics to life in a concrete way and helps children retain knowledge. (DDR)

  15. Quaternary landscape evolution of tectonically active intermontane basins: the case of the Middle Aterno River Valley (Abruzzo, Central Italy)

    NASA Astrophysics Data System (ADS)

    Falcucci, Emanuela; Gori, Stefano; Della Seta, Marta; Fubelli, Giandomenico; Fredi, Paola

    2014-05-01

    The Middle Aterno River Valley is characterised by different Quaternary tectonic depressions localised along the present course of the Aterno River (Central Apennine) .This valley includes the L'Aquila and Paganica-Castelnuovo-San Demetrio tectonic basins, to the North, the Middle Aterno Valley and the Subequana tectonic basin, to the South. The aim of this contribution is to improve the knowledge about the Quaternary geomorphological and tectonic evolution of this portion of the Apennine chain. A synchronous lacustrine depositional phase is recognized in all these basins and attributed to the Early Pleistocene by Falcucci et al. (2012). At that time, this sector of the chain showed four distinct closed basins, hydrologically separated from each other and from the Sulmona depression. This depression, actually a tectonic basin too, was localized South of the Middle Aterno River Valley and it was drained by an endorheic hydrographic network. The formation of these basins was due to the activity of different fault systems, namely the Upper Aterno River Valley-Paganica system and San Pio delle Camere fault, to the North, and the Middle Aterno River Valley-Subequana Valley fault system to the South. These tectonic structures were responsible for the origin of local depocentres inside the depressions which hosted the lacustrine basins. Ongoing surveys in the uppermost sectors of the Middle Aterno River Valley revealed the presence of sub-horizontal erosional surfaces that are carved onto the carbonate bedrock and suspended several hundreds of metres over the present thalweg. Gently dipping slope breccias referred to the Early Pleistocene rest on these surfaces, thus suggesting the presence of an ancient low-gradient landscape adjusting to the local base level.. Subsequently, this ancient low relief landscape underwent a strong erosional phase during the Middle Pleistocene. This erosional phase is testified by the occurrence of valley entrenchment and of coeval fluvial

  16. Late Quaternary tectonic activity and paleoseismicity of the Eastern Messinia Fault Zone, SW Peloponessus (Messinia, Greece).

    NASA Astrophysics Data System (ADS)

    Valkaniotis, Sotirios; Betzelou, Konstantina; Zygouri, Vassiliki; Koukouvelas, Ioannis; Ganas, Athanassios

    2015-04-01

    The southwestern part of Peloponnesus, Messinia and Laconia, is an area of significant tectonic activity situated near the Hellenic trench. Most of the deformation in this area is accommodated by the Eastern Messinia Fault Zone, bordering the western part of Taygetos Mt range and the west coast of Mani peninsula. The Eastern Messinia Fault Zone (EMFZ) is a complex system of primarily normal faults dipping westwards with a strike of NNW-SSE to N-S direction attaining a total length of more than 100 km from the northern Messinia plain in the north to the southern part of Mani peninsula in the south. The continuity of the EMFZ is disrupted by overlapping faults and relay ramp structures. The central part of the EMFZ, from the town of Oichalia to the city of Kalamata, was investigated by detailed field mapping of fault structures and post-alpine sediment formations together with re-evaluation of historical and modern seismicity. Several fault segments with lengths of 6 to 10 km were mapped, defined and evaluated according to their state of activity and age. Analysis of fault striation measurements along fault planes of the fault zone shows a present regime of WSW-ENE extension, in accordance with focal mechanisms from modern seismicity. Known faults like the Katsareika and Verga faults near the city of Kalamata are interpreted as older-generation faults that are re-activated (e.g. the 1986 Ms 6.0 Kalamata earthquake on Verga Fault) as part of a system of distributed deformation. New fault segments, some of them previously unmapped like the Asprohoma fault to the west of Kalamata, and offshore faults like Kitries and Kourtissa, are being assigned to the EMFZ. Moreover, a paleoseismological trench was excavated in the northern part of Pidima fault segment, one of the most prominent active segments of the central part of the EMFZ, in order to examine the paleoearthquake record of the fault system. A significant number of historical and instrumental earthquakes in the area

  17. Spectral damping scaling factors for shallow crustal earthquakes in active tectonic regions

    USGS Publications Warehouse

    Rezaeian, Sanaz; Bozorgnia, Yousef; Idriss, I.M.; Campbell, Kenneth; Abrahamson, Norman; Silva, Walter

    2012-01-01

    Ground motion prediction equations (GMPEs) for elastic response spectra, including the Next Generation Attenuation (NGA) models, are typically developed at a 5% viscous damping ratio. In reality, however, structural and non-structural systems can have damping ratios other than 5%, depending on various factors such as structural types, construction materials, level of ground motion excitations, among others. This report provides the findings of a comprehensive study to develop a new model for a Damping Scaling Factor (DSF) that can be used to adjust the 5% damped spectral ordinates predicted by a GMPE to spectral ordinates with damping ratios between 0.5 to 30%. Using the updated, 2011 version of the NGA database of ground motions recorded in worldwide shallow crustal earthquakes in active tectonic regions (i.e., the NGA-West2 database), dependencies of the DSF on variables including damping ratio, spectral period, moment magnitude, source-to-site distance, duration, and local site conditions are examined. The strong influence of duration is captured by inclusion of both magnitude and distance in the DSF model. Site conditions are found to have less significant influence on DSF and are not included in the model. The proposed model for DSF provides functional forms for the median value and the logarithmic standard deviation of DSF. This model is heteroscedastic, where the variance is a function of the damping ratio. Damping Scaling Factor models are developed for the “average” horizontal ground motion components, i.e., RotD50 and GMRotI50, as well as the vertical component of ground motion.

  18. Geochemistry and Nd Sr isotopic studies of Late Mesozoic granitoids in the southeastern Hubei Province, Middle Lower Yangtze River belt, Eastern China: Petrogenesis and tectonic setting

    NASA Astrophysics Data System (ADS)

    Xie, Guiqing; Mao, Jingwen; Li, Ruiling; Bierlein, Frank P.

    2008-08-01

    A geochemical and isotopic study was carried out for the Mesozoic Yangxin, Tieshan and Echeng granitoid batholiths in the southeastern Hubei Province, eastern China, in order to constrain their petrogenesis and tectonic setting. These granitoids dominantly consist of quartz diorite, monzonite and granite. They are characterized by SiO 2 and Na 2O compositions of between 54.6 and 76.6 wt.%, and 2.9 to 5.6 wt.%, respectively, enrichment in light rare earth elements (LREE) and large ion lithophile elements (LILE), and relative depletion in Y (concentrations ranging from 5.17 to 29.3 ppm) and Yb (0.34-2.83 ppm), with the majority of the granitoids being geochemically similar to high-SiO 2 adakites (HSA). Their initial Nd ( ɛNd = - 12.5 to - 6.1) and Sr (( 87Sr/ 86Sr) i = 0.7054-0.7085) isotopic compositions, however, distinguish them from adakites produced by partial melting of subducted slab and those produced by partial melting of the lower crust of the Yangtze Craton in the Late Mesozoic. The granitoid batholiths in the southeastern Hubei Province exhibit very low MgO ranging from 0.09 to 2.19 wt.% with an average of 0.96 wt.%, and large variations in negative to positive Eu anomalies (Eu/Eu * = 0.22-1.4), especially the Tieshan granites and Yangxin granite porphyry (Eu/Eu * = 0.22-0.73). Geochemical and Nd-Sr isotopic data demonstrate that these granitoids originated as partial melts of an enriched mantle source that experienced significant contamination of lower crust materials and fractional crystallization during magma ascent. Late Mesozoic granitoids in the southeastern Hubei Province of the Middle-Lower Yangtze River belt were dominantly emplaced in an extensional tectonic regime, in response to basaltic underplating, which was followed by lithospheric thinning during the early Cretaceous.

  19. Petrography and geochemistry of Cretaceous to quaternary siliciclastic rocks in the Tarfaya basin, SW Morocco: implications for tectonic setting, weathering, and provenance

    NASA Astrophysics Data System (ADS)

    Ali, Sajid; Stattegger, Karl; Garbe-Schönberg, Dieter; Kuhnt, Wolfgang; Kluth, Oliver; Jabour, Haddou

    2014-01-01

    The petrography, heavy mineral analysis, major element geochemical compositions and mineral chemistry of Early Cretaceous to Miocene-Pliocene rocks, and recent sediments of the Tarfaya basin, SW Morocco, have been studied to reveal their depositional tectonic setting, weathering history, and provenance. Bulk sediment compositional and mineral chemical data suggest that these rocks were derived from heterogeneous sources in the Reguibat Shield (West African Craton) including the Mauritanides and the western Anti-Atlas, which likely form the basement in this area. The Early Cretaceous sandstones are subarkosic in composition, while the Miocene-Pliocene sandstones and the recent sediments from Wadis are generally carbonate-rich feldspathic or lithic arenites, which is also reflected in their major element geochemical compositions. The studied samples are characterized by moderate SiO2 contents and variable abundances of Al2O3, K2O, Na2O, and ferromagnesian elements. Binary tectonic discrimination diagrams demonstrate that most samples can be characterized as passive continental marginal deposits. Al2O3/Na2O ratios indicate more intense chemical weathering during the Early Cretaceous and a variable intensity of weathering during the Late Cretaceous, Early Eocene, Oligocene-Early Miocene, Miocene-Pliocene and recent times. Moreover, weathered marls of the Late Cretaceous and Miocene-Pliocene horizons also exhibit relatively low but variable intensity of chemical weathering. Our results indicate that siliciclastics of the Early Cretaceous were primarily derived from the Reguibat Shield and the Mauritanides, in the SW of the basin, whereas those of the Miocene-Pliocene had varying sources that probably included western Anti-Atlas (NE part of the basin) in addition to the Reguibat Shield and the Mauritanides.

  20. A detection method of subrecent to recent tectonic activity in the anticlinal system of the northern Negev, Israel

    SciTech Connect

    Zilberman, E.; Wachs, D. )

    1988-02-01

    Geomorphological and geophysical methods combined with borehole information were employed to search for possible subrecent small-scale vertical movement along the anticlinal fold belt of the central Negev, Israel. Such tectonic deformation might indicate displacement on the buried reverse faults underneath the anticlines. Variations in the thickness of the alluvial fill in the study area, which are in accordance with the fold structures, could be an indication of recent folding activity along the anticlinal system. In order to detect these thickness variations in the alluvial fill, seismic refraction and electrical resistivity measurements were carries out along the valley of Nahal Besor, which crosses the anticlinal belt. The thickness variations of the alluvial fill along the valley were not found to indicate any significant tectonic movement along the anticlines during the Pleistocene. The thickest alluvium was found overlying a karst bedrock, hence karst relief is suggested to be responsible for these variations.

  1. The relationships between volcanism, tectonism and hydrothermal activity on the Mid-Atlantic Ridge south of the equator

    NASA Astrophysics Data System (ADS)

    Devey, C. W.; German, C. R.; Haase, K. M.; Lackschewitz, K. S.; Melchert, B.; Connelly, D.; Parson, L. M.

    2009-04-01

    Using data from the complete bathymetric and side-scan (TOBI) coverage of the Mid-Atlantic Ridge 2-14 °S collected since 2004 in conjunction with the results of extensive prospecting for hydrothermal systems in this area we attempt to formulate a general model for the interplay between volcanism, tectonics and hydrothermalism on a slow-spreading ridge. The model defines three basic types of ridge morphology with specific hydrothermal characteristics: (a) A deep, tectonically-dominated rift valley where hydrothermalism is seldom associated with volcanism and much more likely confined to long-lived bounding faults (b) a shallower, segment-centre bulge where a combination of repeated magmatic activity and tectonism results in repeated, possibly temporally overlapping periods of hydrothermal activity on the ridge axis and (c) a very shallow, inflated axis beneath which temperatures in all but the uppermost crust are so high that deformation is ductile, inhibiting the formation of high-porosity deep fractures and severely depressing hydrothermal circulation. This model is used together with predicted bathymetry to provide forecasts of the best places to look for hydrothermal sites in the remaining unexplored regions of the South Atlantic

  2. Sequence stratigraphic and synsedimentary tectonic controls on reservoir compartmentalization in a transgressive sequence set: Almond formation, southwest Wyoming

    SciTech Connect

    Krystinik, L.F.; Mead, R.H. )

    1996-01-01

    The Campanian upper Almond Formation in Southwestern Wyoming contains at least 15 aggradational to backstepping microtidal to low mesotidal barrier/shoreline complexes laid down during a period of net transgression from 72 to 70.5 million years ago. Reservoir compartmentalization in the upper Almond occurs at several scales, including an aggradational to retrogradations sequence set composed of 3 retrogradational parasequence sets; numerous parasequences, and diverse barrier sub-facies units. The lowstand shorelines of these sequence sets stack aggradationally prior to transgression by a really extensive, marine mudstone horizons which separate the sequences. Highstand systems tracts are poorly preserved, often completely removed below fourth of fifth order sequence boundaries which cause seaward jumps of facies in excess of 30 Km and place fluvial sediment, coal and lagoonal deposits abruptly over marine mudstone. Each sequence in the upper Almond is composed of several parasequences (sanding-upward, storm-dominated barrier shorefaces) which intercalate with marine mudstone to the east and grade into oyster-bearing, organic-rich lagoonal mudstone to the west. Compartmentalization in the barrier complexes occurs at most parasequence boundaries and in association with major sub-facies; boundaries (barrier margins, tidal inlets, flood-tidal deltas, washover fans). Further reservoir compartmentalization is induced by synsedimentary faulting and subsidence which locally preserve isolated reservoir-quality barrier/shoreline sandstone bodies by dropping them below the depth of ravinement (5-30 m). The recognition of synsedimentary faulting and subsequent ravinement is critical to accurate sequence stratigraphic analysis and for prediction of reservoir compartments.

  3. Sequence stratigraphic and synsedimentary tectonic controls on reservoir compartmentalization in a transgressive sequence set: Almond formation, southwest Wyoming

    SciTech Connect

    Krystinik, L.F.; Mead, R.H.

    1996-12-31

    The Campanian upper Almond Formation in Southwestern Wyoming contains at least 15 aggradational to backstepping microtidal to low mesotidal barrier/shoreline complexes laid down during a period of net transgression from 72 to 70.5 million years ago. Reservoir compartmentalization in the upper Almond occurs at several scales, including an aggradational to retrogradations sequence set composed of 3 retrogradational parasequence sets; numerous parasequences, and diverse barrier sub-facies units. The lowstand shorelines of these sequence sets stack aggradationally prior to transgression by a really extensive, marine mudstone horizons which separate the sequences. Highstand systems tracts are poorly preserved, often completely removed below fourth of fifth order sequence boundaries which cause seaward jumps of facies in excess of 30 Km and place fluvial sediment, coal and lagoonal deposits abruptly over marine mudstone. Each sequence in the upper Almond is composed of several parasequences (sanding-upward, storm-dominated barrier shorefaces) which intercalate with marine mudstone to the east and grade into oyster-bearing, organic-rich lagoonal mudstone to the west. Compartmentalization in the barrier complexes occurs at most parasequence boundaries and in association with major sub-facies; boundaries (barrier margins, tidal inlets, flood-tidal deltas, washover fans). Further reservoir compartmentalization is induced by synsedimentary faulting and subsidence which locally preserve isolated reservoir-quality barrier/shoreline sandstone bodies by dropping them below the depth of ravinement (5-30 m). The recognition of synsedimentary faulting and subsequent ravinement is critical to accurate sequence stratigraphic analysis and for prediction of reservoir compartments.

  4. Repeated large-magnitude earthquakes in a tectonically active, low-strain continental interior: The northern Tien Shan, Kyrgyzstan

    NASA Astrophysics Data System (ADS)

    Landgraf, A.; Dzhumabaeva, A.; Abdrakhmatov, K. E.; Strecker, M. R.; Macaulay, E. A.; Arrowsmith, Jr.; Sudhaus, H.; Preusser, F.; Rugel, G.; Merchel, S.

    2016-05-01

    The northern Tien Shan of Kyrgyzstan and Kazakhstan has been affected by a series of major earthquakes in the late 19th and early 20th centuries. To assess the significance of such a pulse of strain release in a continental interior, it is important to analyze and quantify strain release over multiple time scales. We have undertaken paleoseismological investigations at two geomorphically distinct sites (Panfilovkoe and Rot Front) near the Kyrgyz capital Bishkek. Although located near the historic epicenters, both sites were not affected by these earthquakes. Trenching was accompanied by dating stratigraphy and offset surfaces using luminescence, radiocarbon, and 10Be terrestrial cosmogenic nuclide methods. At Rot Front, trenching of a small scarp did not reveal evidence for surface rupture during the last 5000 years. The scarp rather resembles an extensive debris-flow lobe. At Panfilovkoe, we estimate a Late Pleistocene minimum slip rate of 0.2 ± 0.1 mm/a, averaged over at least two, probably three earthquake cycles. Dip-slip reverse motion along segmented, moderately steep faults resulted in hanging wall collapse scarps during different events. The most recent earthquake occurred around 3.6 ± 1.3 kyr ago (1σ), with dip-slip offsets between 1.2 and 1.4 m. We calculate a probabilistic paleomagnitude to be between 6.7 and 7.2, which is in agreement with regional data from the Kyrgyz range. The morphotectonic signals in the northern Tien Shan are a prime example of deformation in a tectonically active intracontinental mountain belt and as such can help understand the longer-term coevolution of topography and seismogenic processes in similar structural settings worldwide.

  5. Hot spot activity and tectonic settings near Amsterdam-St. Paul plateau (Indian Ocean)

    NASA Astrophysics Data System (ADS)

    Janin, M.; HéMond, C.; Guillou, H.; Maia, M.; Johnson, K. T. M.; Bollinger, C.; Liorzou, C.; Mudholkar, A.

    2011-05-01

    The Amsterdam-St. Paul (ASP) plateau is located in the central part of the Indian Ocean and results from the interaction between the ASP hot spot and the Southeast Indian Ridge (SEIR). It is located near the diffuse boundary between the Capricorn and Australian plates. The seamount chain of the Dead Poets (CDP) is northeast of the ASP plateau and may represent older volcanism related to the ASP hot spot; this chain consists of two groups of seamounts: (1) large flat-topped seamounts formed 8-10 Ma and (2) smaller conical seamounts formed during the last 2 Myr. The ASP hot spot has produced two pulses of magmatism that have been ponded under the ASP plateau and erupted along the divergent boundary between the Capricorn and Australian plates. The N65° orientation of the CDP as well as the seamount's elongated shapes support an opening motion between the Capricorn and Australian plates along a suture oriented in the N155° direction. This motion compared to the Antarctic plate amounts to an apparent velocity of 7.7 cm/yr northeastward for the Capricorn-Australian block. This motion does not fit with a fixed plume model. We suggest, therefore, that the ASP plume experienced a motion of about 1-2 cm/yr to the SW, which is opposite to the asthenospheric flow in this region and suggests a deep-seated plume.

  6. Synergy of tectonic geomorphology, applied geophysics and remote sensing techniques reveals new data for active extensional tectonism in NW Peloponnese (Greece)

    NASA Astrophysics Data System (ADS)

    Fountoulis, Ioannis; Vassilakis, Emmanuel; Mavroulis, Spyridon; Alexopoulos, John; Dilalos, Spyridon; Erkeki, Athanasia

    2015-05-01

    In tectonically active areas, such as in the northwest Peloponnese of western Greece, geomorphic processes are strongly influenced by active faulting; in many cases such faults cannot be easily identified. In this paper we apply multidisciplinary analysis (morphotectonic indices, neotectonic mapping, geophysical surveys and remote sensing techniques) to map the recently-recognized east-west trending Pineios River normal fault zone with a high degree of accuracy, and to better understand its contribution to the evolution of the ancient region of Elis during Holocene time. Fault activity seems to be related to frequent changes in river flow patterns and to displacements of the nearby shoreline. We argue that fault activity is the main reason for migration of Pineios river mouth as documented for several time periods during historical time. Quantitative constraints on deformation caused by the faulting were applied through the application of the morphotectonic indices proposed in this paper, including drainage network asymmetry and sinuosity, and mountain front sinuosity, all of which indicate that this is a highly active structure. Slip rates calculated to be as high as 0.48 mm/yr for the last 209 ka (based on previously published dating) were verified by applied geophysical methods. The fault surface discontinuity was identified at depth using vertical electrical resistivity measurements and depositional layers of different resistivity were found to be clearly offset. Displacement increases toward the west, reaching an observed maximum of 110 m. The most spectacular landform alteration due to surface deformation is the north-south migration of the river estuary into completely different open sea areas during the late Quaternary, mainly during the Holocene. The sediment transport path has been altered several times due to these changes in river geometry with and the most recent seeming to have occurred almost 2000 years ago. The river estuary migrated to its

  7. Tectonic Geomorphology.

    ERIC Educational Resources Information Center

    Bull, William B.

    1984-01-01

    Summarizes representative quantitative tectonic-geomorphology studies made during the last century, focusing on fault-bounded mountain-front escarpments, marine terraces, and alluvial geomorphic surfaces (considering stream terraces, piedmont fault scarps, and soils chronosequences). Also suggests where tectonic-geomorphology courses may best fit…

  8. Evolution of volcanic and tectonic features in caldera settings and their importance in the localization of ore deposits

    USGS Publications Warehouse

    Rytuba, J.J.

    1994-01-01

    Many calderas are located along regionally important fault zones that are intermittently active before and after the caldera cycle. In mineralized calderas, the ore deposits are controlled by structures developed during caldera formation and by regional faults which intersect and reactivate the caldera-related structures. The paper discusses the importance of the different stages of caldera formation in connection with the localization of ore deposits. -from Author

  9. 77 FR 36984 - International Standard-Setting Activities

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-06-20

    ...This notice informs the public of the sanitary and phytosanitary standard-setting activities of the Codex Alimentarius Commission (Codex), in accordance with section 491 of the Trade Agreements Act of 1979, as amended, and the Uruguay Round Agreements Act, Public Law 103-465, 108 Stat. 4809. This notice also provides a list of other standard-setting activities of Codex, including commodity......

  10. The Development of a Resource for Physically Active School Settings

    ERIC Educational Resources Information Center

    Bradley, Vicki R.; O'Connor, Justen P.

    2009-01-01

    This project describes the development of a resource designed to facilitate the exploration of factors influencing physical activity within school settings across multiple levels. Using a socio-ecological framework, the study draws upon factors across three domains that potentially impact physical activity levels within school settings: The…

  11. 75 FR 31749 - International Standard-Setting Activities

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-06-04

    ...This notice informs the public of the sanitary and phytosanitary standard-setting activities of the Codex Alimentarius Commission (Codex), in accordance with section 491 of the Trade Agreements Act of 1979, as amended, and the Uruguay Round Agreements Act, Public Law 103-465, 108 Stat. 4809. This notice also provides a list of other standard-setting activities of Codex, including commodity......

  12. Tectonic Setting and Sedimentary Evolution of The South-west Margin of The Corinth Rift (aigion - Xylocastro Area)

    NASA Astrophysics Data System (ADS)

    Moretti, I.; Ghisetti, F.; Vezani, L.; Sibson, R.

    The existence of a proto-rift in the Gulf of Corinth area has been debated for long time by various authors. Recent subsurface acquisitions through DG-Lab in the Aigion area as well as new field data collection on the southern margin of the rift provide some new insights on the history of progressive opening of the rift. 1- In the studied area, the active faults (Pirgaki, Helike and Aigion faults, from the southernmost to the north- ernmost) display E-W trends and a planar geometry in the first kilometer of depth; faults dip nearly 60 north. 2- The top of the pre-rift Mesozoic-Tertiary limestone se- quence is located at depths of about 900 m (below sea level) in the hangingwall of the Aigion fault and about 700 meters (below ground surface) in the footwall of the fault. 3- The evolution of the Pliocene-Pleistocene sedimentary basins controlled by the synsedimentary activity of their bounding faults and the subsequent deformation of their infilling sequences testifies to the continuous, repeated reactivation of some mas- ter faults (e.g. the Pirgaki fault), and to the contemporaneous activity of different fault systems during the same time interval, as inferred for the Pirgaki and Helike faults dur- ing the late Pleistocene times and the Helike and Aigion faults in the Holocene. 4- No apparent rotation of the Helike and Aigion fault hangingwall occurred in Pleistocene- Holocene times. In contrast, marked rotations of early Pleistocene sequences towards the fault plane, a system of E-W oriented roll-over anticlines and discordant overlap of middle-late Pleistocene fan deltas above earlier rotated horizons are present in the hangingwall sequence of the Pirgaki fault. Our data are consistent with a 2-stage rift evolution. During the first stage (from late Pliocene to early-middle Pleistocene) the rift was wider, extension was accommodated above shallow decollement levels and the total vertical throw of the active faults remained rather small. During the second stage

  13. Tectonic setting of the Portland-Vancouver area, Oregon and Washington: constraints from low-altitude aeromagnetic data

    USGS Publications Warehouse

    Blakely, R.J.; Wells, R.E.; Yelin, T.S.; Madin, I.P.; Beeson, M.H.

    1995-01-01

    Seismic activity in the Portland-Vancouver metropolitan area may be associated with various mapped faults that locally offset volcanic basement of Eocene age and younger. This volcanic basement is concealed in most places by young deposits, vegetation, and urban development. The US Geological Survey conducted an aeromagnetic survey in September 1992 to investigate the extent of these mapped faults and possibly to help identify other seismic and volcanic hazards in the area. The survey was flown approximately 240 m above terrain, along flight lines spaced 460 m apart, and over an area about 50 ?? 50 km. -from Authors

  14. Middle proterozoic tectonic activity in west Texas and eastern New Mexico and analysis of gravity and magnetic anomalies

    SciTech Connect

    Adams, D.C.; Keller, G.R. )

    1994-03-01

    The Precambrian history of west Texas and eastern New Mexico is complex, consisting of four events: Early Proterozoic orogenic activity (16309-1800 Ma), formation of the western granite-rhyolite province (WGRP) (1340-1410 Ma), Grenville age tectonics (1116-1232 Ma), and middle Proterozoic extension possibly related to mid-continent rifting (1086-1109 Ma). Pre-Grenville tectonics, Grenville tectonics, and mid-continent rifting are represented in this area by the Abilene gravity minimum (AGM) and bimodal igneous rocks, which are probably younger. We have used gravity modeling and the comparison of gravity and magnetic anomalies with rock types reported from wells penetrating Precambrian basement to study the AGM and middle Proterozoic extension in this area. The AGM is an east-northeast-trending, 600 km long, gravity low, which extends from the Texas-Oklahoma border through the central basin platform (CBP) to the Delaware basin. This feature appears to predate formation of the mafic body in the CBP (1163 Ma) and is most likely related to Pre-Grenville tectonics, possibly representing a continental margin arc batholith. Evidence of middle Proterozoic extension is found in the form of igneous bodies in the CBP, the Van Horn uplift, the Franklin Mountains, and the Sacramento Mountains. Analysis of gravity and magnetic anomalies shows that paired gravity and magnetic highs are related to mafic intrusions in the upper crust. Mapping of middle Proterozoic igneous rocks and the paired anomalies outlines a 530 km diameter area of distributed east-west-oriented extension. The Debaca-Swisher terrain of shallow marine and clastic sedimentary rocks is age correlative with middle Proterozoic extension. These rocks may represent the lithology of possible Proterozoic exploration targets. Proterozoic structures were reactivated during the Paleozoic, affecting both the structure and deposition in the Permian basin.

  15. Petrography and geochemistry of sands from the Chachalacas and Veracruz beach areas, western Gulf of Mexico, Mexico: Constraints on provenance and tectonic setting

    NASA Astrophysics Data System (ADS)

    Armstrong-Altrin, John S.; Nagarajan, Ramasamy; Balaram, Vysetti; Natalhy-Pineda, Olmedo

    2015-12-01

    Compositional and geochemical analyses of sands collected from the Chachalacas (CHA) and Veracruz (VER) beach areas along the western Gulf of Mexico were studied to determine the provenance and tectonic setting of the source region. The modal composition showed that the proportion of quartz (Q) is lower in CHA than in VER sands. The average quartz-feldspar-lithic fragment (QFL) ratios for the CHA and VER sands are Q75F8L17 and Q86F4L10, respectively. The X-ray diffractometer (XRD) and Scanning Electron Microscope equipped with EDAX spectrometer (SEM-EDS) data revealed that the CHA sands were abundant in heavy minerals like magnetite, ilmenite, and zircon. The rare earth element concentration (REE) is higher in CHA than in VER sands, which is due to the concentration of heavy minerals in CHA sands. The weathering indices such as chemical index of alteration (CIA), plagioclase index of alteration, and A-CN-K (A = Al2O3, CN = CaO∗ + Na2O, K = K2O) plot suggested that the intensity of weathering in the source area was low to moderate. The index of chemical variability (ICV) for the CHA (˜1.9-3.0) and VER (˜0.82-1.33) sands indicated that the compositional maturity was higher for the VER sands. The concentrations of Co, Cr, Ni, and V are lower in VER sands than in CHA sands, indicating that the CHA sands were derived from the intermediate source rocks. Provenance modelling revealed that the CHA sands were associated with the mixture of basalt, andesite, dacite, and trachyandesite in the ratio of 5:20:25:50. The VER sands were best matched with a mixture having 75-90% dacite and 25-10% andesite compositions. The provenance difference between the two beach areas suggested that longshore current play a less significant role in mixing and homogenization of sands. The multidimensional tectonic discrimination diagrams revealed rift and collision settings for the VER and CHA beach areas, respectively, which is consistent with the general geology of the study areas.

  16. GeoBioScience: Red Wood Ants as Bioindicators for Active Tectonic Fault Systems in the West Eifel (Germany)

    PubMed Central

    Berberich, Gabriele; Schreiber, Ulrich

    2013-01-01

    Simple Summary In a 1.140 km² study area of the volcanic West Eifel, approx. 3,000 Red Wood Ant (RWA; Formica rufa-group) mounds had been identified and correlated with tectonically active gas-permeable faults, mostly strike-slip faults. Linear alignment of RWA mounds and soil gas anomalies distinctly indicate the course of these faults, while clusters of mounds indicate crosscut zones of fault systems, which can be correlated with voids caused by crustal block rotation. This demonstrates that RWA are bioindicators for identifying active fault systems and useful where information on the active regime is incomplete or the resolution by technical means is insufficient. Abstract In a 1.140 km² study area of the volcanic West Eifel, a comprehensive investigation established the correlation between red wood ant mound (RWA; Formica rufa-group) sites and active tectonic faults. The current stress field with a NW-SE-trending main stress direction opens pathways for geogenic gases and potential magmas following the same orientation. At the same time, Variscan and Mesozoic fault zones are reactivated. The results showed linear alignments and clusters of approx. 3,000 RWA mounds. While linear mound distribution correlate with strike-slip fault systems documented by quartz and ore veins and fault planes with slickensides, the clusters represent crosscut zones of dominant fault systems. Latter can be correlated with voids caused by crustal block rotation. Gas analyses from soil air, mineral springs and mofettes (CO2, Helium, Radon and H2S) reveal limiting concentrations for the spatial distribution of mounds and colonization. Striking is further the almost complete absence of RWA mounds in the core area of the Quaternary volcanic field. A possible cause can be found in occasionally occurring H2S in the fault systems, which is toxic at miniscule concentrations to the ants. Viewed overall, there is a strong relationship between RWA mounds and active tectonics in the West Eifel

  17. Tectonic-geodynamic settings of OIB-magmatism on the eastern Asian continental margin during the Cretaceous-Paleogene transition

    NASA Astrophysics Data System (ADS)

    Filatova, N. I.

    2015-11-01

    At the Cretaceous-Paleogene transition, the convergent boundary between the Asian and Pacific plates was replaced by a transform boundary to determine destruction of the continental margin including the Okhotsk-Chukotka Cretaceous subduction-related belt along left-lateral strike-slip and downdip-strikeslip faults. The newly formed East Asian rift system (EARS) continues in the easterly direction the Mongol-Okhotsk zone of left-lateral strike-slip faults, a former transform boundary of the Asian continent. Basaltoids of the East Asian rift system that erupted through fractures onto the former active margin are similar intraplate OIB volcanics related to the lower mantle source. The specific feature of OIB-type magmatism in the system consists in its continental marginal position near the transform boundary.

  18. The April 2007 earthquake swarm near Lake Trichonis and implications for active tectonics in western Greece

    NASA Astrophysics Data System (ADS)

    Kiratzi, A.; Sokos, E.; Ganas, A.; Tselentis, A.; Benetatos, C.; Roumelioti, Z.; Serpetsidaki, A.; Andriopoulos, G.; Galanis, O.; Petrou, P.

    2008-06-01

    We investigate the properties of the April 2007 earthquake swarm (Mw 5.2) which occurred at the vicinity of Lake Trichonis (western Greece). First we relocated the earthquakes, using P- and S-wave arrivals to the stations of the Hellenic Unified Seismic Network (HUSN), and then we applied moment tensor inversion to regional broad-band waveforms to obtain the focal mechanisms of the strongest events of the 2007 swarm. The relocated epicentres, cluster along the eastern banks of the lake, and follow a distinct NNW-ESE trend. The previous strong sequence close to Lake Trichonis occurred in June-December 1975. We applied teleseismic body waveform inversion, to obtain the focal mechanism solution of the strongest earthquake of this sequence, i.e. the 31 December 1975 (Mw 6.0) event. Our results indicate that: a) the 31 December 1975 Mw 6.0 event was produced by a NW-SE normal fault, dipping to the NE, with considerable sinistral strike-slip component; we relocated its epicentre: i) using phase data reported to ISC and its coordinates are 38.486°N, 21.661°E; ii) using the available macroseismic data, and the coordinates of the macroseismic epicentre are 38.49°N, 21.63°E, close to the strongly affected village of Kato Makrinou; b) the earthquakes of the 2007 swarm indicate a NNW-SSE strike for the activated main structure, parallel to the eastern banks of Lake Trichonis, dipping to the NE and characterized by mainly normal faulting, occasionally combined with sinistral strike-slip component. The 2007 earthquake swarm did not rupture the well documented E-W striking Trichonis normal fault that bounds the southern flank of the lake, but on the contrary it is due to rupture of a NW-SE normal fault that strikes at a ˜ 45° angle to the Trichonis fault. The left-lateral component of faulting is mapped for the first time to the north of the Gulf of Patras which was previously regarded as the boundary for strike-slip motions in western Greece. This result signifies the

  19. Eruptive history and tectonic setting of Medicine Lake Volcano, a large rear-arc volcano in the southern Cascades

    NASA Astrophysics Data System (ADS)

    Donnelly-Nolan, Julie M.; Grove, Timothy L.; Lanphere, Marvin A.; Champion, Duane E.; Ramsey, David W.

    2008-10-01

    Medicine Lake Volcano (MLV), located in the southern Cascades ˜ 55 km east-northeast of contemporaneous Mount Shasta, has been found by exploratory geothermal drilling to have a surprisingly silicic core mantled by mafic lavas. This unexpected result is very different from the long-held view derived from previous mapping of exposed geology that MLV is a dominantly basaltic shield volcano. Detailed mapping shows that < 6% of the ˜ 2000 km 2 of mapped MLV lavas on this southern Cascade Range shield-shaped edifice are rhyolitic and dacitic, but drill holes on the edifice penetrated more than 30% silicic lava. Argon dating yields ages in the range ˜ 475 to 300 ka for early rhyolites. Dates on the stratigraphically lowest mafic lavas at MLV fall into this time frame as well, indicating that volcanism at MLV began about half a million years ago. Mafic compositions apparently did not dominate until ˜ 300 ka. Rhyolite eruptions were scarce post-300 ka until late Holocene time. However, a dacite episode at ˜ 200 to ˜ 180 ka included the volcano's only ash-flow tuff, which was erupted from within the summit caldera. At ˜ 100 ka, compositionally distinctive high-Na andesite and minor dacite built most of the present caldera rim. Eruption of these lavas was followed soon after by several large basalt flows, such that the combined area covered by eruptions between 100 ka and postglacial time amounts to nearly two-thirds of the volcano's area. Postglacial eruptive activity was strongly episodic and also covered a disproportionate amount of area. The volcano has erupted 9 times in the past 5200 years, one of the highest rates of late Holocene eruptive activity in the Cascades. Estimated volume of MLV is ˜ 600 km 3, giving an overall effusion rate of ˜ 1.2 km 3 per thousand years, although the rate for the past 100 kyr may be only half that. During much of the volcano's history, both dry HAOT (high-alumina olivine tholeiite) and hydrous calcalkaline basalts erupted

  20. Eruptive history and tectonic setting of Medicine Lake Volcano, a large rear-arc volcano in the southern Cascades

    USGS Publications Warehouse

    Donnelly-Nolan, J. M.; Grove, T.L.; Lanphere, M.A.; Champion, D.E.; Ramsey, D.W.

    2008-01-01

    Medicine Lake Volcano (MLV), located in the southern Cascades ??? 55??km east-northeast of contemporaneous Mount Shasta, has been found by exploratory geothermal drilling to have a surprisingly silicic core mantled by mafic lavas. This unexpected result is very different from the long-held view derived from previous mapping of exposed geology that MLV is a dominantly basaltic shield volcano. Detailed mapping shows that < 6% of the ??? 2000??km2 of mapped MLV lavas on this southern Cascade Range shield-shaped edifice are rhyolitic and dacitic, but drill holes on the edifice penetrated more than 30% silicic lava. Argon dating yields ages in the range ??? 475 to 300??ka for early rhyolites. Dates on the stratigraphically lowest mafic lavas at MLV fall into this time frame as well, indicating that volcanism at MLV began about half a million years ago. Mafic compositions apparently did not dominate until ??? 300??ka. Rhyolite eruptions were scarce post-300??ka until late Holocene time. However, a dacite episode at ??? 200 to ??? 180??ka included the volcano's only ash-flow tuff, which was erupted from within the summit caldera. At ??? 100??ka, compositionally distinctive high-Na andesite and minor dacite built most of the present caldera rim. Eruption of these lavas was followed soon after by several large basalt flows, such that the combined area covered by eruptions between 100??ka and postglacial time amounts to nearly two-thirds of the volcano's area. Postglacial eruptive activity was strongly episodic and also covered a disproportionate amount of area. The volcano has erupted 9 times in the past 5200??years, one of the highest rates of late Holocene eruptive activity in the Cascades. Estimated volume of MLV is ??? 600??km3, giving an overall effusion rate of ??? 1.2??km3 per thousand years, although the rate for the past 100??kyr may be only half that. During much of the volcano's history, both dry HAOT (high-alumina olivine tholeiite) and hydrous calcalkaline

  1. Long-lasting tectonic activities of the Lepontine Dome. New evidence from low-temperature thermochronology

    NASA Astrophysics Data System (ADS)

    Elfert, Simon; Reiter, Wolfgang; Spiegel, Cornelia

    2013-11-01

    To investigate the Neogene exhumation history of the central European Alps, we apply low-temperature thermochronology in combination with thermal history modelling. Fission track and (U-Th-Sm)/He ages on apatites from the central Lepontine Dome (Ticino, Switzerland) indicate higher exhumation rates in the centre of the dome and rather moderate exhumation at the northern and southern boundaries since Neogene times. We present a model for explaining the latest stage exhumation of the central Lepontine Dome and show that (I) both episodic and continuous exhumations are found on small-scale throughout the Neogene, (II) compressional tectonics control the exhumation until the Late Neogene, (III) the exhumation regime changes between 6 and 4 Ma and (IV) increasing hinterland exhumation rates at the Mio-Pliocene boundary cannot be related to tectonic structures of the dome and they are thus explained by climatic changes.

  2. Paleozoic magmatism and porphyry Cu-mineralization in an evolving tectonic setting in the North Qilian Orogenic Belt, NW China

    NASA Astrophysics Data System (ADS)

    Qiu, Kun-Feng; Deng, Jun; Taylor, Ryan D.; Song, Kai-Rui; Song, Yao-Hui; Li, Quan-Zhong; Goldfarb, Richard J.

    2016-05-01

    40-m.y.-younger ore-bearing porphyritic granodiorite is sub-alkaline and peraluminous. They are enriched in LREEs and LILEs, depleted in HFSEs, and show weak negative Eu anomalies. They display εHf(t) values of captured or inherited zircons in the range of +8.5 to +10.0, and younger two-stage Hf model ages of 0.78 Ga and 0.86 Ga, similar to those of ca. 485 Ma tonalite. The ca. 445 Ma zircons have εHf(t) values of -2.1 to +9.9, with two-stage Hf model ages of 0.75-1.27 Ga. Moreover, they have relatively high oxygen fugacity than that of the precursor barren tonalite. The ca. 445 Ma magmas at Wangdian thus formed in a subduction setting, and incorporated melts from the subduction-modified lithosphere that had previously been enriched by additions of chalcophile and siderophile element-rich materials by the earlier magmatism and metasomatism during the Paleo Qilian-Qinling Ocean subduction event.

  3. Paleozoic magmatism and porphyry Cu-mineralization in an evolving tectonic setting in the North Qilian Orogenic Belt, NW China

    USGS Publications Warehouse

    Qiu, Kun-Feng; Deng, Jun; Taylor, Ryan D.; Song, Kai-Rui; Song, Yao-Hui; Li, Quan-Zhong; Goldfarb, Richard J.

    2016-01-01

    the lithosphere. In contrast, the 40-m.y.-younger ore-bearing porphyritic granodiorite is sub-alkaline and peraluminous. They are enriched in LREEs and LILEs, depleted in HFSEs, and show weak negative Eu anomalies. They displayεHf(t) values of captured or inherited zircons in the range of +8.5 to +10.0, and younger two-stage Hf model ages of 0.78 Ga and 0.86 Ga, similar to those of ca. 485 Ma tonalite. The ca. 445 Ma zircons have εHf(t) values of −2.1 to +9.9, with two-stage Hf model ages of 0.75–1.27 Ga. Moreover, they have relatively high oxygen fugacity than that of the precursor barren tonalite. The ca. 445 Ma magmas at Wangdian thus formed in a subduction setting, and incorporated melts from the subduction-modified lithosphere that had previously been enriched by additions of chalcophile and siderophile element-rich materials by the earlier magmatism and metasomatism during the Paleo Qilian-Qinling Ocean subduction event.

  4. Teaching Plate Tectonic Concepts using GeoMapApp Learning Activities

    NASA Astrophysics Data System (ADS)

    Goodwillie, A. M.; Kluge, S.

    2012-12-01

    GeoMapApp Learning Activities ( http://serc.carleton.edu/geomapapp/collection.html ) can help educators to expose undergraduate students to a range of earth science concepts using high-quality data sets in an easy-to-use map-based interface called GeoMapApp. GeoMapApp Learning Activities require students to interact with and analyse research-quality geoscience data as a means to explore and enhance their understanding of underlying content and concepts. Each activity is freely available through the SERC-Carleton web site and offers step-by-step student instructions and answer sheets. Also provided are annotated educator versions of the worksheets that include teaching tips, additional content and suggestions for further work. The activities can be used "off-the-shelf". Or, since the educator may require flexibility to tailor the activities, the documents are provided in Word format for easy modification. Examples of activities include one on the concept of seafloor spreading that requires students to analyse global seafloor crustal age data to calculate spreading rates in different ocean basins. Another activity has students explore hot spots using radiometric age dating of rocks along the Hawaiian-Emperor seamount chain. A third focusses upon the interactive use of contours and profiles to help students visualise 3-D topography on 2-D computer screens. A fourth activity provides a study of mass wasting as revealed through geomorphological evidence. The step-by-step instructions and guided inquiry approach reduce the need for teacher intervention whilst boosting the time that students can spend on productive exploration and learning. The activities can be used, for example, in a classroom lab with the educator present and as self-paced assignments in an out-of-class setting. GeoMapApp Learning Activities are funded through the NSF GeoEd program and are aimed at students in the introductory undergraduate, community college and high school levels. The activities are

  5. Geology, petrology, and tectonic setting of the Mafic rocks of the 1480 Ma old granite-rhyolite terrane of Missouri, USA

    NASA Astrophysics Data System (ADS)

    Sylvester, P. J.

    Igneous and metamorphic mafic rocks form a volumetrically subordinate component of the 1480 Ma old granite rhyolite terrain of Missouri. The igneous rocks are present in the St. Francois Mountains and a drillcore from Shannon county and can be subdivided into two groups. The Silver Mines Mafic Group exhibits some calc-alkaline chemical affinities that may be the result of crustal contamination by a source with a bulk intermediate to felsic composition. The contaminant probably is not the exposed granites or rhyolites of the St. Francois Mountains. The 1500 to 1400 Ma old belt probably formed in an extensional tectonic setting. The Basin and Range province of the western United States may be the most similar modern analogue. Between 1400 to 1200 Ma ago, an incipient continental rift may have formed along the axis of the 1500 to 1400 Ma old magmatic belt. Mafic magma emplaced during the rifting event possibly included the Skrainka Mafic Group of Missouri, the Harp dikes and Seal Lake Group of Labrador, and some of the Gardar rocks of southwest Greenland.

  6. Tectonics, magmatism and fluid flow in a transtensional strike-slip setting: The northern termination of the Liquiñe-Ofqui fault System, Chile

    NASA Astrophysics Data System (ADS)

    Cembrano, J. M.; Perez-Flores, P.; Sánchez, P.; Sielfeld, G.

    2013-12-01

    vein systems, which appear to be associated with dextral strike-slip displacement on the LOFS. Fault-vein and vein structure varies from mineral fibers to typical ridge-and-groove striae. Bladed calcite occurs in dilational jogs along the main LOFS master faults; they are interpreted to represent boiling episodes. Thicker and more pervasive WNW sinistral-reverse fault-vein systems and breccias bodies suggest that the fault-valve mechanism was active during fluid transport and mineral precipitation. In some sites the WNW-striking system cuts and displaces the active LOFS, suggesting that their active has extended to at least the Pleistocene. Internally consistent structural and kinematic data from fault-fracture systems spatially and temporally associated with volcanoes and hydrothermal systems suggest that the same processes that drive the interplay between volcanism and tectonics may also control the nature, geometry and composition of geothermal reservoirs in the southern Andes.

  7. Timing and tectonic setting of the Sijiaying banded iron deposit in the eastern Hebei province, North China Craton: Constraints from geochemistry and SIMS zircon U-Pb dating

    NASA Astrophysics Data System (ADS)

    Cui, Minli; Zhang, Lianchang; Wu, Huaying; Xu, Yingxia; Li, Wenjun

    2014-11-01

    The North China Craton (NCC), one of the oldest continental blocks in Asia, has a complicated evolutionary history with the age of the old crust up to 3.8 Ga and records the important geological events of the Earth. The Sijiaying BIF, the largest banded iron formation located in eastern Hebei province, in the east part of NCC, records an important thermo-tectonic event; Previous studies focused on the geological description, but the timing and tectonic setting have been unclear so far. The Sijiaying BIF is hosted in Neoarchean metamorphic rocks, which includes biotite-leptynite, hornblende plagioclase-gneiss and biotite plagioclase-gneiss. Using major element contents and ratios of the host rocks, the protoliths of the hornblende plagioclase-gneiss and biotite plagioclase-gneiss are shown to be dacite, whereas those of the biotite-leptynites are sedimentary rocks. Based on geology and geochemistry of the host rocks, we infer that the Sijiaying BIF is an Algoma type deposit. SIMS zircon U-Pb dating shows: igneous zircons from the biotite plagioclase-gneiss and hornblende plagioclase-gneiss have U-Pb ages of 2535 ± 8 Ma and 2543 ± 14 Ma, respectively; zircons from the biotite-leptynite have an age of 2537 ± 13 Ma. We infer that the ages of 2543-2535 Ma represent the time of the Sijiaying BIF. PAAS-normalized REY profiles of the ore samples are characterized by LREE depletion and HREE enrichment, positive La and Eu anomalies and an average Y/Ho weight ratio of 32, indicating a mixture of submarine hydrothermal fluids and deep seawater. REE data was combined with the δ18O analyzed by previous researcher of the ore from individual magnetite bands to infer that the Sijiaying BIF precipitated from hydrothermal fluids discharging on the sea floor. The hornblende plagioclase-gneiss and biotite plagioclase-gneiss that are enriched in LILE and LREE and depleted in high field strength elements (HFSE) Nb, Ta and Ti, have geochemical signatures that are similar to those of

  8. Gravity sliding in basinal setting, a surficial record of tectonic and geodynamic evolution; examples from the southern W. Alps and their foreland

    NASA Astrophysics Data System (ADS)

    Dumont, T.; Franzi, V.; Matthews, S. J.

    2012-04-01

    -Miocene dynamics and which are overprinted or crosscut by the modern orogen (Dumont et al., 2011). Theses examples show that, in different structural and geodynamic settings, detailed analysis of basin floor morphology, (re)sediments transport directions, syndepositional deformations and provenance of exotic blocks can provide useful information about the regional kinematics, which can be integrated with other datasets, i.e. tectonic, metamorphic, thermochronologic, etc. Dumont T., Schwartz S., Guillot S., Simon-Labric T., Tricart P. & Jourdan S. (2011), Structural and sedimentary records of the Oligocene revolution in the Western Alpine arc. Jour. Geodyn., in press. Ferry S. & Flandrin J. (1979), Mégabrèches de resédimentation, lacunes mécaniques et pseudo-« hard-grounds » sur la marge vocontienne au Barrémien et à l'Aptien inférieur (SE France). Géologie Alpine, 55, p. 75-92. Michard A., Dumont T., Andreani L. & Loget N. (2010), Structural and sedimentary records of the Oligocene revolution in the Western Alpine arc. Bull. Soc. Géol. Fr., 181, p. 565-581.

  9. Late Pleistocene to Historical Activity of the Hovd Fault (Mongolian Altay) from Tectonic Geomorphology and Paleoseismology

    NASA Astrophysics Data System (ADS)

    Ferry, M. A.; Battogtokh, D.; Ritz, J. F.; Kurtz, R.; Braucher, R.; Klinger, Y.; Ulzibat, M.; Chimed, O.; Demberel, S.

    2015-12-01

    Active tectonics of western Mongolia is dominated by large strike-slip fault systems that produced great historical earthquakes: the Bulnay fault (Mw 8.1 and 8.4 in 1905), the Fu-Yun fault (Mw 8.0 in 1931) and the Bogd fault (Mw 8.1 in 1957). Central to these faults is the Altay Range that accommodates ~4 mm/yr of right-lateral motion. An earthquake of similar magnitude occurred in 1761 and has been attributed to the Hovd fault were seemingly fresh surface rupture was reported in 1985. Here, we study the Ar-Hötöl section of the Hovd fault where surface rupture was described over a length of ~200 km. Detailed mapping of stream gullies from high-resolution Pleiades satellite images show a consistent pattern of right-lateral offsets from a few meters to ~500 m. At Climbing Rock, we surveyed a gully offset by 75 ± 5 m. The associated surface was sampled for 10Be profile which yields an exposure age of 154 ± 20 ka. The resulting minimal right-lateral slip rate ranges 0.4-0.6 mm/yr. However, drainage reconstruction suggests this surface may have recorded as much as 400 ± 20 m of cumulative offset. This implies the Hovd fault may accommodate as much as 2.6 ± 0.4 mm/yr, which would make it the main active fault of the Altay. At a smaller scale, TLS topography documents offsets in the order of 2.5-5 m that likely correspond to the most recent surface-rupturing event with Mw ~8. A value of 2.8-3.0 m is reconstructed from a Uiger grave dated AD 750-840. At Marmot Creek and Small Creek, short drainages flow across the fault and form ponds against the main scarp. Two paleoseimic trenches reveal similar stratigraphy with numerous peat layers that developed over alluvial sands. The fault exhibits near vertical strands affecting pre-ponding units as well as a well-developed peat unit radiocarbon-dated AD 1465-1635. This unit likely corresponds to the ground surface at the time of the last rupture. It is overlain with a sandy pond unit on top of which a second continuous peat

  10. Petrology, geochemistry, and tectonic setting of granitic rocks from the Ellsworth-Whitmore Mountains crustal block and Thiel Mountains, West Antarctica

    NASA Astrophysics Data System (ADS)

    Vennum, Walter R.; Storey, Bryan C.

    Ellsworth-Whitmore Mountains crustal block (EWM) is a belt of small mountain ranges, hills, and nunataks which trend northward 500 km from the Thiel Mountains of the Transantarctic range to the Ellsworth Mountains. Granitic rocks compose most of the Pirrit Hills, Nash Hills, and Whitmore Mountains, and all of Pagano Nunatak. Mount Woollard is a migmatized complex of biotite schist, amphibolite, pegmatite, and massive biotite granite. A rhyodacite stock crops out in the Martin Hills. The Mount Seelig hornblende-bearing biotite granite of the Whitmore Mountains and the Mount Woollard biotite granite are metaluminous diopside-normative granitoids. All other granitic rocks of the EWM are mildly peraluminous, corundum-normative biotite (locally muscovite-bearing) leucogranites. Previously published radiometric ages range from 163 to 190 Ma. Petrography, geochemistry, and isotopic data suggest that these rocks are largely highly differentiated leucocratic S-type granites formed by anatexis of either metasedimentary rocks or more deeply seated, more mafic, plagioclase-rich granitoids. In these aspects they strongly resemble granites developed in intracontinental terranes such as the Hercynian belt of Europe and in continental collision-type settings such as the Bhutan and Nepalese Himalaya and the Seward Peninsula of western Alaska. We ascribe their origin to post-tectonic emplacement in a neutral or extensional (rifted) within-plate setting following deformation of the EWM. S-type Cambro-Ordovician granitic rocks and Precambrian quartz monzonite porphyries of the Thiel Mountains are geochemically similar to the EWM granites, but are correlative with the Granite Harbour Intrusive Series of the Transantarctic Mountains and the Wyatt Formation of the nearby La Gorce Mountains, respectively.

  11. Multilayer stress from gravity and its tectonic implications in urban active fault zone: A case study in Shenzhen, South China

    NASA Astrophysics Data System (ADS)

    Xu, Chuang; Wang, Hai-hong; Luo, Zhi-cai; Ning, Jin-sheng; Liu, Hua-liang

    2015-03-01

    It is significant to identify urban active faults for human life and social sustainable development. The ordinary methods to detect active faults, such as geological survey, artificial seismic exploration, and electromagnetic exploration, are not convenient to be carried out in urban area with dense buildings. It is also difficult to supply information about vertical extension of the deeper faults by these methods. Gravity, reflecting the mass distribution of the Earth's interior, provides an alternative way to detect faults, which is more efficient and convenient for urban active fault detection than the aforementioned techniques. Based on the multi-scale decomposition of gravity anomalies, a novel method to invert multilayer horizontal tectonic stresses is proposed. The inverted multilayer stress fields are further used to infer the distribution and stability of the main faults. In order to validate our method, the multilayer stress fields in the Shenzhen fault zone are calculated as a case study. The calculated stress fields show that their distribution is controlled significantly by the strike of the main faults and can be used to derive depths of the faults. The main faults in Shenzhen may range from 4 km to 20 km in the depth. Each layer of the crust is nearly equipressure since the horizontal tectonic stress has small amplitude. It indicates that the main faults in Shenzhen are relatively stable and have no serious impact on planning and construction of the city.

  12. Collapse of the Cretaceous Helvetiafjellet Formation due to tectonic activity at Kvalvågen, eastern Spitsbergen

    NASA Astrophysics Data System (ADS)

    Onderdonk, N.; Midtkandal, I.; Ahokas, J.

    2008-12-01

    A variety of features recording disturbance of Mid-Cretaceous sediments are exposed in coastal cliffs at Kvalvågen, east Spitsbergen. The most striking of these features are large displaced blocks of Helvetiafjellet Formation sandstone (ranging from 5 to 25 meters across) that were dropped down into underlying shale- dominated sediments along normal faults. In addition to the displaced blocks much of the sandstone unit is missing along a 2 km stretch of coastal exposure and must have been slipped out of the plane of exposure. Several hypotheses have been proposed to explain the style and cause of the Cretaceous collapse at Kvalvågen including delta front collapse (Nemec et al., 1988), landslides into a submarine canyon (Steel et al., 2001), and collapse related to magmatic activity (Midtkandal et al., 2007). New structural data and field observations show that the orientations and style of deformation are not entirely consistent with the previous hypotheses and are better explained as the direct result of tectonically produced topography (i.e., a fault scarp). The deformation at Kvalvågen is the result of west-side-down displacement along a north-striking fault that crops out at the southern end of the cliff exposure. Tectonic disturbance in the area began in Hauterivian time and was over by the early Aptian. These outcrops are the only evidence of tectonic activity in the area during the Mid-Cretaceous and may be the result of displacement along a previously unrecognized extension of the Lomfjorden fault zone or related to regional stresses imposed by extensive sill intrusions during the formation of the High Arctic Large Igneous Province.

  13. 10 CFR 960.5-2-11 - Tectonics.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... of active faulting within the geologic setting. (2) Historical earthquakes or past man-induced... design limits. (3) Evidence, based on correlations of earthquakes with tectonic processes and features, (e.g., faults) within the geologic setting, that the magnitude of earthquakes at the site...

  14. 10 CFR 960.5-2-11 - Tectonics.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... of active faulting within the geologic setting. (2) Historical earthquakes or past man-induced... design limits. (3) Evidence, based on correlations of earthquakes with tectonic processes and features, (e.g., faults) within the geologic setting, that the magnitude of earthquakes at the site...

  15. 10 CFR 960.4-2-7 - Tectonics.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... activity within the geologic setting during the Quaternary Period. (2) Historical earthquakes within the... isolation. (3) Indications, based on correlations of earthquakes with tectonic processes and features, that either the frequency of occurrence or the magnitude of earthquakes within the geologic setting...

  16. 10 CFR 960.5-2-11 - Tectonics.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... of active faulting within the geologic setting. (2) Historical earthquakes or past man-induced... design limits. (3) Evidence, based on correlations of earthquakes with tectonic processes and features, (e.g., faults) within the geologic setting, that the magnitude of earthquakes at the site...

  17. 10 CFR 960.4-2-7 - Tectonics.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... activity within the geologic setting during the Quaternary Period. (2) Historical earthquakes within the... isolation. (3) Indications, based on correlations of earthquakes with tectonic processes and features, that either the frequency of occurrence or the magnitude of earthquakes within the geologic setting...

  18. 10 CFR 960.5-2-11 - Tectonics.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... of active faulting within the geologic setting. (2) Historical earthquakes or past man-induced... design limits. (3) Evidence, based on correlations of earthquakes with tectonic processes and features, (e.g., faults) within the geologic setting, that the magnitude of earthquakes at the site...

  19. 10 CFR 960.4-2-7 - Tectonics.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... activity within the geologic setting during the Quaternary Period. (2) Historical earthquakes within the... isolation. (3) Indications, based on correlations of earthquakes with tectonic processes and features, that either the frequency of occurrence or the magnitude of earthquakes within the geologic setting...

  20. 10 CFR 960.5-2-11 - Tectonics.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... of active faulting within the geologic setting. (2) Historical earthquakes or past man-induced... design limits. (3) Evidence, based on correlations of earthquakes with tectonic processes and features, (e.g., faults) within the geologic setting, that the magnitude of earthquakes at the site...

  1. Goal setting: Eating, Physical activity & Weight loss | Smokefree.gov

    Cancer.gov

    No matter what your weight loss goal is, the key to reaching your goals is to make changes to your lifestyle like eating and physical activity. This involves setting realistic expectations and making a plan. 

  2. Tectonic history and setting of a seismogenic intraplate fault system that lacks microseismicity: The Saline River fault system, southern United States

    NASA Astrophysics Data System (ADS)

    Cox, Randel Tom; Hall, J. Luke; Gardner, Chris S.

    2013-11-01

    Although the northwest-striking Saline River fault system of southeastern Arkansas is not defined by microseismicity, it is associated with sand blows and shows evidence of Pleistocene and Holocene surface ruptures, suggesting a significant seismogenic potential. This fault system is within the northern Gulf of Mexico interior coastal plain, a region only recently recognized as containing seismogenic faults. To better characterize this active fault system, we reconstructed its post-Paleozoic history using petroleum and coal industry wire-line well log and seismic reflection subsurface data. The Saline river fault system initiated as a series of northwest-striking grabens during Triassic/Jurassic uplift and incipient Gulf of Mexico rifting along the basement Alabama-Oklahoma transform margin of the North American Proterozoic craton. During post-rift subsidence, these grabens were buried by Gulf sediments until mid-Cretaceous uplift and igneous activity resulted in minor extensional reactivation of graben faults. Faulting style changed from extension to transpression during the Late Cretaceous due to compression of eastern North America as the North Atlantic rapidly widened and due to thermal weakening of the Alabama-Oklahoma transform lithospheric discontinuity as it obliquely crossed a mantle hot spot. In the Late Cretaceous, graben faults experienced contractional reactivation and steep, deeply-rooted transpressional faults developed within and parallel to the graben system. These transpressional faults locally displace Eocene, Pleistocene, and Holocene sediments. Fault activity continues on the Saline River fault system due to thin crust along the Alabama-Oklahoma transform and to high heat flow, which act together to weaken the crust and promote seismogenic tectonism. The fault system may lack appreciable microseismicity because the aftershock sequence of the last large earthquake has had time to dissipate.

  3. Morphotectonic evolution of triangular facets and wine-glass valleys in the Noakoh anticline, Zagros, Iran: Implications for active tectonics

    NASA Astrophysics Data System (ADS)

    Bahrami, Shahram

    2012-07-01

    The Noakoh anticline is located in Kermanshah province and is part of the Simply Folded Belt of Zagros. Boundaries of 97 triangular facets and 67 wine-glass (W-G) valleys, which formed on anticline limbs, were delineated using Quickbird satellite imagery. The strata dip (D), area (A), base length (BL), topographic slope (S) of facets, the maximum width (M), outlet width (O) and ratio of maximum width to outlet width (W index) of W-G valleys were analysed in detail. Noakoh anticline was subdivided into 9 tectonic zones on the basis of dip, topographic slopes and width of limbs. Results show that there are strong positive correlations between means of D-BL and S-BL pairs. Poor positive correlations exist between means of D-A and S-A pairs. Among W-G valley metrics, the W index has strong relations with D and S parameters. Based on the results, steep facets with long bases and well developed W-G valleys with narrow outlets and wide upper parts are associated with more rotated limbs having steep slopes. Facets on the northeastern slope have more forest cover, micro-organism activity, karstic features and soil cover, whereas facets on relatively drier southwestern slope are characterized by physical weathering processes and minor karstic landforms. This study demonstrates that, apart from tectonic activity as a major control on the morphometry of facets and valleys, climate and slope aspect have also acted as secondary factors on the development of the studied landforms.

  4. Late Pleistocene and Holocene uplift history of Cyprus: implications for active tectonics along the southern margin of the Anatolian microplate

    USGS Publications Warehouse

    Harrison, R.W.; Tsiolakis, E.; Stone, B.D.; Lord, A.; McGeehin, J.P.; Mahan, S.A.; Chirico, P.

    2013-01-01

    The nature of the southern margin of the Anatolian microplate during the Neogene is complex, controversial and fundamental in understanding active plate-margin tectonics and natural hazards in the Eastern Mediterranean region. Our investigation provides new insights into the Late Pleistocene uplift history of Cyprus and the Troodos Ophiolite. We provide isotopic (14C) and radiogenic (luminescence) dates of outcropping marine sediments in eastern Cyprus that identify periods of deposition during marine isotope stages (MIS) 3, 4, 5 and 6. Past sea-levels indicated by these deposits are c. 95±25 m higher in elevation than estimates of worldwide eustatic sea-level. An uplift rate of c. 1.8 mm/year and possibly as much as c. 4.1 mm/year in the past c. 26–40 ka is indicated. Holocene marine deposits also occur at elevations higher than those expected for past SL and suggest uplift rates of c. 1.2–2.1 mm/year. MIS-3 marine deposits that crop out in southern and western Cyprus indicate uniform island-wide uplift. We propose a model of tectonic wedging at a plate-bounding restraining bend as a mechanism for Late Pleistocene to Holocene uplift of Cyprus; uplift is accommodated by deformation and seismicity along the margins of the Troodos Ophiolite and re-activation of its low-angle, basal shear zone.

  5. GeoBioScience: Red Wood Ants as Bioindicators for Active Tectonic Fault Systems in the West Eifel (Germany).

    PubMed

    Berberich, Gabriele; Schreiber, Ulrich

    2013-01-01

    In a 1.140 km² study area of the volcanic West Eifel, a comprehensive investigation established the correlation between red wood ant mound (RWA; Formica rufa-group) sites and active tectonic faults. The current stress field with a NW-SE-trending main stress direction opens pathways for geogenic gases and potential magmas following the same orientation. At the same time, Variscan and Mesozoic fault zones are reactivated. The results showed linear alignments and clusters of approx. 3,000 RWA mounds. While linear mound distribution correlate with strike-slip fault systems documented by quartz and ore veins and fault planes with slickensides, the clusters represent crosscut zones of dominant fault systems. Latter can be correlated with voids caused by crustal block rotation. Gas analyses from soil air, mineral springs and mofettes (CO₂, Helium, Radon and H₂S) reveal limiting concentrations for the spatial distribution of mounds and colonization. Striking is further the almost complete absence of RWA mounds in the core area of the Quaternary volcanic field. A possible cause can be found in occasionally occurring H₂S in the fault systems, which is toxic at miniscule concentrations to the ants. Viewed overall, there is a strong relationship between RWA mounds and active tectonics in the West Eifel. PMID:26487413

  6. Channel morphometry, sediment transport, and implications for tectonic activity and surficial ages of Titan basins

    USGS Publications Warehouse

    Cartwright, R.; Clayton, J.A.; Kirk, R.L.

    2011-01-01

    Fluvial features on Titan and drainage basins on Earth are remarkably similar despite differences in gravity and surface composition. We determined network bifurcation (Rb) ratios for five Titan and three terrestrial analog basins. Tectonically-modified Earth basins have Rb values greater than the expected range (3.0-5.0) for dendritic networks; comparisons with Rb values determined for Titan basins, in conjunction with similarities in network patterns, suggest that portions of Titan's north polar region are modified by tectonic forces. Sufficient elevation data existed to calculate bed slope and potential fluvial sediment transport rates in at least one Titan basin, indicating that 75mm water ice grains (observed at the Huygens landing site) should be readily entrained given sufficient flow depths of liquid hydrocarbons. Volumetric sediment transport estimates suggest that ???6700-10,000 Titan years (???2.0-3.0??105 Earth years) are required to erode this basin to its minimum relief (assuming constant 1m and 1.5m flows); these lowering rates increase to ???27,000-41,000 Titan years (???8.0-12.0??105 Earth years) when flows in the north polar region are restricted to summer months. ?? 2011 Elsevier Inc.

  7. Stability of active mantle upwelling revealed by net characteristics of plate tectonics.

    PubMed

    Conrad, Clinton P; Steinberger, Bernhard; Torsvik, Trond H

    2013-06-27

    Viscous convection within the mantle is linked to tectonic plate motions and deforms Earth's surface across wide areas. Such close links between surface geology and deep mantle dynamics presumably operated throughout Earth's history, but are difficult to investigate for past times because the history of mantle flow is poorly known. Here we show that the time dependence of global-scale mantle flow can be deduced from the net behaviour of surface plate motions. In particular, we tracked the geographic locations of net convergence and divergence for harmonic degrees 1 and 2 by computing the dipole and quadrupole moments of plate motions from tectonic reconstructions extended back to the early Mesozoic era. For present-day plate motions, we find dipole convergence in eastern Asia and quadrupole divergence in both central Africa and the central Pacific. These orientations are nearly identical to the dipole and quadrupole orientations of underlying mantle flow, which indicates that these 'net characteristics' of plate motions reveal deeper flow patterns. The positions of quadrupole divergence have not moved significantly during the past 250 million years, which suggests long-term stability of mantle upwelling beneath Africa and the Pacific Ocean. These upwelling locations are positioned above two compositionally and seismologically distinct regions of the lowermost mantle, which may organize global mantle flow as they remain stationary over geologic time. PMID:23803848

  8. Channel morphometry, sediment transport, and implications for tectonic activity and surficial ages of Titan basins

    USGS Publications Warehouse

    Cartwright, Richard; Clayton, Jordan A.; Kirk, Randolph L.

    2011-01-01

    Fluvial features on Titan and drainage basins on Earth are remarkably similar despite differences in gravity and surface composition. We determined network bifurcation (Rb) ratios for five Titan and three terrestrial analog basins. Tectonically-modified Earth basins have Rb values greater than the expected range (3.0–5.0) for dendritic networks; comparisons with Rb values determined for Titanbasins, in conjunction with similarities in network patterns, suggest that portions of Titan's north polar region are modified by tectonic forces. Sufficient elevation data existed to calculate bed slope and potential fluvial sedimenttransport rates in at least one Titanbasin, indicating that 75 mm water ice grains (observed at the Huygens landing site) should be readily entrained given sufficient flow depths of liquid hydrocarbons. Volumetric sedimenttransport estimates suggest that ~6700–10,000 Titan years (~2.0–3.0 x 105 Earth years) are required to erode this basin to its minimum relief (assuming constant 1 m and 1.5 m flows); these lowering rates increase to ~27,000–41,000 Titan years (~8.0–12.0 x 105 Earth years) when flows in the north polar region are restricted to summer months.

  9. Tectonic evolution and setting of the Sa'al Complex, southern Sinai, Egypt: A Proterozoic continental back-arc rift model

    NASA Astrophysics Data System (ADS)

    Fowler, A.; Hassen, I.; Hassan, M.

    2015-04-01

    The Sa'al Complex is a mainly low grade metamorphosed polydeformed volcanosedimentary sequence exposed in the northern central Sinai basement, Egypt. Details of the stratigraphy, sedimentology and petrography of the three formations: Agramiya, Ra'ayan and Zaghara Formations are described. The earliest deformation (D1) is related to extensional tectonism and HT-LP regional metamorphism. The main D1 structure is a bedding-parallel S1 foliation with at least 50% vertical shortening in the well-foliated Ra'ayan phyllites. Earlier models that explained S1 by bedding-parallel shearing are rejected. The Sa'al volcanism, D1 extension and HT metamorphism were probably associated with back-arc rifting in a continental arc setting, similar to the modern Taupo Zone of New Zealand. Later deformations, D2 and D3, involved folding about NE-trending and NW-trending axial planes, respectively. D2 was probably a result of compressional stresses typical of continental back-arc regions, and resulted in development of steep NW-vergent imbricate thrusts and NE-trending F2 meso- and macrofolds. The Firinga gabbro and the Wadi Murad foliated diorite intruded along D2 backthrusts, while the main diorite intrusion dominating the centre of the complex intruded along D2 steepened imbricate thrusts. F3 deformation may be related to the latest convergence of the east and west Gondwana, and has correlatives in the Kid and Feiran Complexes. A final deformation D4 that generated the main strike-slip faults in the area correlates with NE-SW trending σ1, inconsistent with a Najd origin. Recent geochronological results from U/Pb zircon studies are difficult to reconcile with stratigraphic and intrusion field evidence, and apparently require very tight time constraints on the main metamorphism, D1 and D2 deformations of the complex.

  10. Decadal to millennial deformation in the Pamir - Tian Shan collision zone, NW China and surface expression of active tectonics

    NASA Astrophysics Data System (ADS)

    Bufe, A.; Bookhagen, B.; Burbank, D. W.; Bekaert, D. P.; Hussain, E.

    2013-12-01

    The collision between the Pamir and the Tian Shan is a type example of intracontinental collision. GPS studies show that in Northwest China, at the junction between the Tarim basin, the Pamir and the Tian Shan, 7-9 mm/y of north-south shortening are presently accommodated across the boundary between the two orogens. Here, the deformation has mostly stepped out from the high mountain front into the foreland and has formed a complex array of compressional structures. We compare rates of decadal deformation in the area with 104- to 106-year estimates and investigate the extent to which stream profiles and topography reflect the active tectonics in this setting. A dataset of decadal deformation rates around the Tarim-Tian Shan-Pamir junction in Northwest China is obtained from Interferometric Synthetic Aperture Radar (InSAR) time-series analysis. We use the StaMPS/MTI package to combine small-baseline and persistent-scatterer techniques and obtain results that show no significant residual topographic phase correlation. Our data show that deformation has stepped away from the high mountain front and is concentrated on a few structures in the foreland of the Pamir and Tian Shan. Line-of-sight deformation of up to 2-4 mm/y on the Pamir Frontal Thrust (PFT) and the Kashi detachment anticline are observed. No significant displacement of the Main Pamir Thrust can be detected. Within error, the modern deformation rates agree with previously published millennial to million-year estimates along the PFT. However, decadal deformation rates deviate from million-year shortening and rock-uplift rates of anticlines in the foreland of the Tian Shan. It remains unclear whether the discrepancy arises from a recent change to a new persistent uplift rate, or merely from short timescale fluctuation of uplift rate, for example within an earthquake cycle. In an additional step, we extract stream profiles and normalized steepness index (ksn) values for rivers with drainage areas larger than 9

  11. Topographic Expression of Active Tectonics in the Absence of Physical Erosion in the External Dinarides of Croatia

    NASA Astrophysics Data System (ADS)

    Casale, G.; Paulson, K.; Salamonsen, E.; Bennett, R. A.; Surkovic, M.

    2010-12-01

    The Dinarides of Croatia and Bosnia-Herzegovina form part of the actively deforming Adria-Eurasia boundary, but their topography differs greatly from similar sized active orogens such as the neighboring Northern Apennines. The Dinarides include two distinct regions with contrasting surface drainage patterns: the surface drainage of the External Dinarides is a series of disconnected internally drained basins, whereas the Internal Dinarides much more closely resemble the Northern Apennines with well connected basins and waterways. We used SRTM DEMs to characterize surface drainage in the Dinarides and found a strong correlation between mapped rock-type and surface connectivity. Specifically, disconnected internally drained basins are restricted to carbonate lithologies prevelant in the External Dinarides, which are often susceptible to chemical dissolution, whereas heterogenous rock types found in the Internal Dinarides are associated with typical dendritic drainages. The extent of the carbonate-dominated topography characterizing the External Dinarides is further divided into areas of distinctly higher (300-700 m) and (<100 m) lower relief despite the inability of the low topography of the Dinarides to concentrate precipitation and thus chemical erosion. Therefore, the topographic variation between these two areas is either controlled by the contrasting solubility of various carbonate lithologies, or active tectonics. To test for contrasting solubility, we analyzed a suite of samples from both ridge and valley forming sites using a microprobe and ICP-MS. We found that the weight percent Ca was indistinguishable between our samples and that of pure calcite. We then expanded our investigation by incorporating spectral analysis of ASTER imagery across the entire external Dinarides, with similar results. We conclude that the large scale topography of the External Dinarides is not the result of lithologic heterogeneity, and is instead controlled by tectonics. Our

  12. Quaternary migration of active extension revealed by a syn-tectonic alluvial fan shift. A case study in the Northern Apennines of Italy

    NASA Astrophysics Data System (ADS)

    Mirabella, Francesco; Bucci, Francesco; Cardinali, Mauro; Santangelo, Michele; Guzzetti, Fausto

    2016-04-01

    In areas characterized by the progressive migration of active extension through time, shifts in the position of the active depocenter occur. Such shifts through time produces peculiar geomorphological settings that are often characterized by wind gaps, abandoned valleys, streams captures and drainage inversions. These features provide the opportunity to investigate active areas by studying the recent-most geological history of the related nearby basins. We investigate this topic in a tectonically active area in the Northern Apennines of Italy, as indicated by both instrumental and historical seismicity (maximum epicentral intensity I0=VIII) and extension rates in the order of 2.5-2.7 mm/yr. In particular, we study the Montefalco ridge drainage inversion. Here, fluvial sands and imbricated conglomerates deposited in a lower Pleistocene depocenter constituted by an extensional subsiding basin, are presently uplifted more than 200 m above the present day alluvial plain. The Montefalco ridge drainage inversion, at about 400 m a.s.l., separates two valleys, the Gualdo Cattaneo - Bastardo valley to the West (300 m a.s.l.) and the Foligno present-day alluvial plain to the East (200 m a.s.l.). Seismic reflection data show that the maximum thickness of the continental sequence in the Foligno valley is in the order of 500 m. This valley is presently occupied by a 37 km2 alluvial fan produced by the Topino river flowing from NE to SW. To unravel the Quaternary tectonic evolution of the area, we integrate different data sets collected by field mapping, detailed photo-geological data, sediments provenance information, and subsurface data. We interpret the Montefalco ridge as a paleo-Foligno-like alluvial fan representing the evidence of the recent migration of the active extension to the East of around 7 km. Considering an age of deformation of 2.5 My, an extension rate of about 2.8 mm/yr is derived, which corresponds to the present-day geodetic rates. We stress the importance

  13. Geomorphologic, stratigraphic and sedimentologic evidences of tectonic activity in Sone-Ganga alluvial tract in Middle Ganga Plain, India

    NASA Astrophysics Data System (ADS)

    Sahu, Sudarsan; Saha, Dipankar

    2014-08-01

    The basement of the Ganga basin in the Himalayan foreland is criss-crossed by several faults, dividing the basin into several sub-blocks forming horsts, grabens, or half-grabens. Tectonic perturbations along basement faults have affected the fluvial regime and extent of sediment fill in different parts of the basin during Late Quaternary. The East Patna Fault (EPF) and the West Patna Fault (WPF), located in Sone-Ganga alluvial tract in the southern marginal parts of Middle Ganga Plain (MGP), have remained tectonically active. The EPF particularly has acted significantly and influenced in evolving the geomorphological landscape and the stratigraphic architecture of the area. The block bounded by the two faults has earlier been considered as a single entity, constituting a half-graben. The present investigation (by morpho-stratigraphic and sedimentologic means) has revealed the existence of yet another fault within the half-graben, referred to as Bishunpur-Khagaul Fault (BKF). Many of the long profile morphological characters (e.g., knick-zone, low width-depth ratio) of the Sone River at its lower reaches can be ascribed to local structural deformation along BKF. These basement faults in MGP lie parallel to each other in NE-SW direction.

  14. Tree Tectonics

    NASA Astrophysics Data System (ADS)

    Vogt, Peter R.

    2004-09-01

    Nature often replicates her processes at different scales of space and time in differing media. Here a tree-trunk cross section I am preparing for a dendrochronological display at the Battle Creek Cypress Swamp Nature Sanctuary (Calvert County, Maryland) dried and cracked in a way that replicates practically all the planform features found along the Mid-Oceanic Ridge (see Figure 1). The left-lateral offset of saw marks, contrasting with the right-lateral ``rift'' offset, even illustrates the distinction between transcurrent (strike-slip) and transform faults, the latter only recognized as a geologic feature, by J. Tuzo Wilson, in 1965. However, wood cracking is but one of many examples of natural processes that replicate one or several elements of lithospheric plate tectonics. Many of these examples occur in everyday venues and thus make great teaching aids, ``teachable'' from primary school to university levels. Plate tectonics, the dominant process of Earth geology, also occurs in miniature on the surface of some lava lakes, and as ``ice plate tectonics'' on our frozen seas and lakes. Ice tectonics also happens at larger spatial and temporal scales on the Jovian moons Europa and perhaps Ganymede. Tabletop plate tectonics, in which a molten-paraffin ``asthenosphere'' is surfaced by a skin of congealing wax ``plates,'' first replicated Mid-Oceanic Ridge type seafloor spreading more than three decades ago. A seismologist (J. Brune, personal communication, 2004) discovered wax plate tectonics by casually and serendipitously pulling a stick across a container of molten wax his wife and daughters had used in making candles. Brune and his student D. Oldenburg followed up and mirabile dictu published the results in Science (178, 301-304).

  15. Tectonic evolution and chrono-stratigraphy of sediments in Lake Ohrid Basin (Macedonia/Albania) revealed by multichannel seismic and bathymetric data sets

    NASA Astrophysics Data System (ADS)

    Lindhorst, K.; Krastel, S.; Reicherter, K. R.; Stipp, M.; Wagner, B.; Schwenk, T.

    2012-12-01

    Lake Ohrid located on the Balkan Peninsula is probably the oldest existing lake in Europe and is often referred to as a hotspot of endemic biodiversity. Here we present the analysis of multichannel seismic cross sections and bathymetric data demonstrating the importance of Lake Ohrid as a valuable sedimentary archive within the terrestrial Mediterranean region. According to our data Lake Ohrid formed in two main deformation phases such as a transtensional phase opening up a pull-apart basin in Late Miocene and an extensional phase since the Pliocene leading to the present geometry. The early stage geometry of the basin has a typical rhomboidal shape restricted by two sets of major normal faults. The location of the basin initiation coincides with the greatest depth of the acoustic basement that is now covered by more than 700 m of undisturbed sediments. Numerous faults are present in the northern area offsetting syn-tectonic sediments, thus confirming the hypothesis that Lake Ohrid Basin is still experiencing extension. Seismic stratigraphic interpretation revealed a succession of fluvial deposits overlying the pre-rift basement. The majority of the entire sedimentary infill is interpreted as deep lacustrine sediments. A chrono-stratigraphic scheme developed for undisturbed lacustrine sediments back to an age of 430 kyr indicate that the sediments document glacial and interglacial cycles back to Marine Isotope Stage 12. A refined calculation on the basis of our new data set revealed a limnological age of at least 2 Myr for Lake Ohrid. Mass wasting deposits are widespread in Lake Ohrid at different stratigraphic levels of the basin. Slide deposits, in general are present adjacent to major fault structures suggesting that they are seismically triggered. A mass wasting deposited along the Lini Fault in the NW-part can be linked to the 518 AD earthquake that destroyed the city of Ohrid. The Udenisht Slide Complex (USC) in the southwestern part of the lake is the

  16. Collision tectonics

    SciTech Connect

    Coward, M.P.; Ries, A.C.

    1985-01-01

    The motions of lithospheric plates have produced most existing mountain ranges, but structures produced as a result of, and following the collision of continental plates need to be distinguished from those produced before by subduction. If subduction is normally only stopped when collision occurs, then most geologically ancient fold belts must be collisional, so it is essential to recognize and understand the effects of the collision process. This book consists of papers that review collision tectonics, covering tectonics, structure, geochemistry, paleomagnetism, metamorphism, and magmatism.

  17. Coastal and submarine instabilities distribution in the tectonically active SW margin of the Corinth Rift (Psathopyrgos, Achaia, Greece)

    NASA Astrophysics Data System (ADS)

    Simou, Eirini; Papanikolaou, Dimitrios; Lykousis, Vasilios; Nomikou, Paraskevi; Vassilakis, Emmanuel

    2014-05-01

    The Corinth Rift, one of the most active rifts in the world as local extension trending NE-SW reaches the amount of 14±2 mm/yr, corresponds to one of the largest zones of seismically active normal faulting. The formation, growth and migration southwards of the prevailing fault systems, which evolve simultaneously with the intense morphogenetic processes, are overprinted in the age, facies and thickness of the Plio-Pleistocene sequences constructing the south margin of the western Gulf of Corinth. The dominant fault blocks, defined by east-west trending, north dipping normal faults, are accompanied by several morphological features and anomalies, noticed in both the terrestrial and the marine environment. Our main aim has been to examine how the tectonic evolution, in combination with the attendant fierce erosional and sedimentary processes, has affected the morphology through geodynamic processes expressed as failures in the wider coastal area. High resolution multibeam bathymetry in combination with the available land surface data have contributed to submarine and subaerial morphological mapping. These have been used as a basis for the detection of all those geomorphic features that indicate instabilities probably triggered, directly or indirectly, by the ongoing active tectonic deformation. The interpretation of the combined datasets shows that the southwestern margin of the Corinth Rift towards Psathopyrgos fault zone is characterized by intense coastal relief and a narrow, almost absent, continental shelf, which passes abruptly to steep submarine slopes. These steep slope values denote the effects of the most recent brittle deformation and are related to coastal and submarine instabilities and failures. High uplift rates and rapid sedimentation, indicative of the regional high-energy terrestrial and submarine environment, are subsequently balanced by the transportation of the seafloor currents, especially where slope gradients decrease, disintegrating the

  18. Tectonics of the Outer Planet Satellites

    NASA Technical Reports Server (NTRS)

    McKinnon, W. B.; Collins, G. C.; Moore, J. M.; Nimmo, F.; Pappalardo, R. T.; Prockter, L. M.; Schenk, P. M.

    2010-01-01

    Tectonic features on the satellites of the outer planets range from the familiar, such as clearly recognizable graben on many satellites, to the bizarre, such as the ubiquitous double ridges on Europa, the twisting sets of ridges on Triton, or the isolated giant mountains rising from Io's surface. All of the large and middle-sized outer planet satellites except Io are dominated by water ice near their surfaces. Though ice is a brittle material at the cold temperatures found in the outer solar system, the amount of energy it takes to bring it close to its melting point is lower than for a rocky body. Therefore, some unique features of icy satellite tectonics may be influenced by a near-surface ductile layer beneath the brittle surface material, and several of the icy satellites may possess subsurface oceans. Sources of stress to drive tectonism are commonly dominated by the tides that deform these satellites as they orbit their primary giant planets. On several satellites, the observed tectonic features may be the result of changes in their tidal figures, or motions of their solid surfaces with respect to their tidal figures. Other driving mechanisms for tectonics include volume changes due to ice or water phase changes in the interior, thermoelastic stress, deformation of the surface above rising diapirs of warm ice, and motion of subsurface material toward large impact basins as they fill in and relax. Most satellites exhibit evidence for extensional deformation, and some exhibit strike-slip faulting, whereas contractional tectonism appears to be rare. Io s surface is unique, exhibiting huge isolated mountains that may be blocks of crust tilting and foundering into the rapidly emptying interior as the surface is constantly buried by deposits from hyperactive volcanoes. Of the satellites, diminutive Enceladus is spectacularly active; its south polar terrain is a site of young tectonism, copious heat flow, and tall plumes venting into space. Europa's surface is

  19. Seismo-turbidite Sedimentology: Implications for Active Tectonic Margin Stratigraphy and Sediment Facies Patterns

    NASA Astrophysics Data System (ADS)

    Nelson, C. H.; Goldfinger, C.; Gutierrez Pastor, J.; Polonia, A.; Van Daele, M. E.

    2014-12-01

    Earthquakes generate mass transport deposits (MTDs); megaturbidites (MTD overlain by coeval turbidite); multi-pulsed, stacked, and mud homogenite seismo-turbidites; tsunamites; and seiche deposits. The strongest (Mw 9) earthquake shaking signatures appear to create multi-pulsed individual turbidites, where the number and character of multiple coarse-grained pulses for correlative turbidites generally remain constant both upstream and downstream in different channel systems. Multiple turbidite pulses, that correlate with multiple ruptures shown in seismograms of historic earthquakes (e.g. Chile 1960, Sumatra 2004 and Japan 2011), support this hypothesis. The weaker (Mw = or < 8) (e.g. northern California San Andreas) earthquakes generate dominantly upstream simple fining-up (uni-pulsed) turbidites in single tributary canyons and channels; however, downstream stacked turbidites result from synchronously triggered multiple turbidity currents that deposit in channels below confluences of the tributaries. Proven tsunamites, which result from tsunami waves sweeping onshore and shallow water debris into deeper water, are a fine-grained turbidite cap over other seismo-turbidites. In contrast, MTDs and seismo-turbidites result from slope failures. Multiple great earthquakes cause seismic strengthening of slope sediment, which results in minor MTDs in basin floor turbidite system deposits (e.g. maximum run-out distances of MTDs across basin floors along active margins are up to an order of magnitude less than on passive margins). In contrast, the MTDs and turbidites are equally intermixed in turbidite systems of passive margins (e.g. Gulf of Mexico). In confined basin settings, earthquake triggering results in a common facies pattern of coeval megaturbidites in proximal settings, thick stacked turbidites downstream, and ponded muddy homogenite turbidites in basin or sub-basin centers, sometimes with a cap of seiche deposits showing bi-directional flow patterns.

  20. Southeast Papuan crustal tectonics: Imaging extension and buoyancy of an active rift

    NASA Astrophysics Data System (ADS)

    Abers, G. A.; Eilon, Z.; Gaherty, J. B.; Jin, G.; Kim, YH.; Obrebski, M.; Dieck, C.

    2016-02-01

    Southeast Papua hosts the world's youngest ultra-high-pressure (UHP) metamorphic rocks. These rocks are found in an extensional setting in metamorphic core complexes. Competing theories of extensional shear zones or diapiric upwelling have been suggested as driving their exhumation. To test these theories, we analyze the CDPAPUA temporary array of 31 land and 8 seafloor broadband seismographs. Seismicity shows that deformation is being actively accommodated on the core complex bounding faults, offset by transfer structures in a manner consistent with overall north-south extension rather than radial deformation. Rayleigh wave dispersion curves are jointly inverted with receiver functions for crustal velocity structure. They show crustal thinning beneath the core complexes of 30-50% and very low shear velocities at all depths beneath the core complexes. On the rift flanks velocities resemble those of normal continents and increase steadily with depth. There is no evidence for velocity inversions that would indicate that a major density inversion exists to drive crustal diapirs. Also, low-density melt seems minor within the crust. Together with the extension patterns apparent in seismicity, these data favor an extensional origin for the core complexes and limit the role of diapirism as a secondary exhumation mechanism, although deeper mantle diapirs may be undetected. A small number of intermediate-depth earthquakes, up to 120 km deep, are identified for the first time just northeast of the D'Entrecasteaux Islands. They occur at depths similar to those recorded by UHP rocks and similar temperatures, indicating that the modern seismicity occurs at the setting that generates UHP metamorphism.

  1. SET for life: biochemical activities and biological functions of SET domain-containing proteins

    PubMed Central

    Herz, Hans-Martin; Garruss, Alexander; Shilatifard, Ali

    2013-01-01

    SET domain-containing proteins belong to a group of enzymes named after a common domain that utilizes the cofactor S-adenosyl-L-methionine (SAM) to achieve methylation of its substrates. Many SET domain-containing proteins have been shown to display catalytic activity towards particular lysine residues on histones, but emerging evidence also indicates that various non-histone proteins are specifically targeted by this clade of enzymes. Here, we summarize the most recent findings on the biological functions of the major families of SET domain-containing proteins catalyzing the methylation of histones 3 on lysines 4, 9, 27, and 36 (H3K4, H3K9, H3K27, and H3K36) and histone 4 on lysine 20 (H4K20) as well as candidates that have been reported to regulate non-histone substrates. PMID:24148750

  2. An active set algorithm for nonlinear optimization with polyhedral constraints

    NASA Astrophysics Data System (ADS)

    Hager, William W.; Zhang, Hongchao

    2016-08-01

    A polyhedral active set algorithm PASA is developed for solving a nonlinear optimization problem whose feasible set is a polyhedron. Phase one of the algorithm is the gradient projection method, while phase two is any algorithm for solving a linearly constrained optimization problem. Rules are provided for branching between the two phases. Global convergence to a stationary point is established, while asymptotically PASA performs only phase two when either a nondegeneracy assumption holds, or the active constraints are linearly independent and a strong second-order sufficient optimality condition holds.

  3. Geochemical discrimination of siliciclastic sediments from active and passive margin settings

    NASA Astrophysics Data System (ADS)

    Verma, Surendra P.; Armstrong-Altrin, John S.

    2016-03-01

    Discrimination of active and passive margins is important from both academic and economic aspects. This can only be successfully achieved, however, if there are major compositional differences among sediments derived from different continental margins. A worldwide database of active and passive margin settings was established from published major and trace element geochemical data of Neogene to Quaternary siliciclastic sediments. These data were used to evaluate the performance of existing discrimination diagrams, which were shown to work unsatisfactorily with success values of mostly between 0% and 30%. Because these diagrams were not based on a statistically coherent methodology, we proposed two new discriminant functions from linear discriminant analysis of multinormally distributed isometric log-transformed ratios of major and combined major and trace elements. These new diagrams showed very high percent success values of about 87%-97% and 84%-86% for the active and passive margins, respectively, for the original database. Excellent performance of the multidimensional diagrams and related discriminant functions was confirmed from 11 test studies involving Quaternary to Holocene siliciclastic sediments from known tectonic margins. The expected result of an active or passive margin was obtained, with most samples plotting correctly in the respective field.

  4. New evidence for active tectonics at the boundary of the Kashi Depression, China, from time series InSAR observations

    NASA Astrophysics Data System (ADS)

    He, Ping; Wen, Yangmao; Xu, Caijun; Liu, Yang; Fok, H. S.

    2015-06-01

    Kashi Depression is one of the most complex active tectonic areas in the southern flank of Tianshan, China. Due to the lack of ground observations, the boundary of basin mountain transition zone and the interseismic activity of the Tianshan have not been clearly determined. In this study, 48 Envisat Advanced Synthetic Aperture Radar (ASAR) imagery acquired from 2003 to 2010 are used to construct interferograms for measuring high-resolution interseismic deformation in the Kashi Depression area. A global atmospheric model ERA-Interim provided by the European Center for Medium Range Weather Forecast (ECMWF) and a global network orbital correction are applied to remove atmospheric effect, and the long-wavelength orbital errors, respectively, for the interferograms. Interferometric SAR time series with Atmospheric Estimation Model (InSAR TS + AEM) are then used to obtain a deformation rate map for the Kashi Depression area. The InSAR rate map indicates that the north part of South Atushi Fault has ~ 3 mm/year uplift relative to that of the south part. This result manifests the main tectonic deformation potentially occurs along the Southern Atushi Fault. Based on a simple edge dislocation model, the dip angle of 31 ± 0.6°, slip rate of 2.3 ± 0.1 mm/year, and locking depth of 10.6 ± 0.4 km for the Southern Atushi Fault between Tianshan Orogenic Belt and the Kashi Depression are obtained. This modeling result shows in good agreement with the InSAR derived rates. Our results show that the Southern Atushi Fault is the main active fault in block boundary region between the south of Tianshan and the Tarim Basin.

  5. Early Cretaceous tectono-magmatic activity and tectonic implications along the Sulu Orogenic Belt - case study of the Dashan complex

    NASA Astrophysics Data System (ADS)

    Liu, Yanghe; Liu, Junlai; Shi, Xiaoxiao; Yuan, Fengjie; Ni, Jinlong; Wu, Wenbin; Chen, Xiaoyu

    2016-04-01

    The tectonic extension of the eastern Eurasian continent during the Early Cretaceous resulted in widespread occurrence of metamorphic core complexes, wide rifts and related magmatic emplacement, among which the Dashan complex of the Jiaonan orogenic belt is a typical example. The complex is a complex massif of several types of granitic rocks. The core of the complex is composed of massive porphry-bearing biotite-hornblende granitoid without any evidence of ductile deformation. Mylonitized augen quartz monzonite and granodiorite constitute the margin of the complex. A transition zone is composed of porphyritic biotite-hornblende monzonite with weakly orientated K-feldspar phenocryst and mafic microgranular enclave. The foliations along the northwestern margin of the complex dip to NW at with dip angles of about 38°, and along the southwestern and northeastern margins to SE with dip angles of about 45°. Stretching lineations are constantly plunging WNW-ESE with pitch angles between 10° and 40°, which is consistent with the orientation of lineations in the other regions in eastern China. The granites,porphyritic monzogranite and the mafic microgranular enclaves in monzogranite are dated of ca.126Ma. The similarities in ages of crystallization of the monzogranite and its MME's implies the existence of magmatic mixing processes. Meanwhile, the mylonitized augen quartz monzonite and granodiorite along the margins of the complex possess crystallization ages of 129.8±1.1Ma and 132.7±2.8Ma, respectively. The petrographical zonation , structural characteristics and the systematical zircon U-Pb geochronology of the granitic rocks may suggest that the Dashan complex has experienced multistage emplacement under the same tectonic extension setting. In despite of the location of the complex near the Tanlu fault zone, the remarkable consistency of the orientations of stretching lineation of the Dashan complex to those from the other parts of the eastern China area implies

  6. Dynamical parameter analysis of continuous seismic signals of Popocatépetl volcano (Central Mexico): A case of tectonic earthquakes influencing volcanic activity

    NASA Astrophysics Data System (ADS)

    Tárraga, Marta; Cruz-Reyna, Servando; Mendoza-Rosas, Ana; Carniel, Roberto; Martínez-Bringas, Alicia; García, Alicia; Ortiz, Ramon

    2012-06-01

    The continuous background seismic activity contains information on the internal state of a volcanic system. Here, we report the influence of major regional tectonic earthquakes (M > 5 in most cases) on such state, reflected as changes in the spectral and dynamical parameters of the volcano continuous seismic data. Although changes do not always occur, analysis of five cases of earthquake-induced variations in the signals recorded at Popocatépetl volcano in central México reveal significant fluctuations following the tectonic earthquakes. External visible volcanic activity, such as small to moderate explosions and ash emissions, were related to those fluctuations. We briefly discuss possible causes of the variations. We conclude that recognition of fluctuations in the dynamical parameters in volcano monitoring seismic signals after tectonic earthquakes, even those located in the far field, hundreds of kilometers away, may provide an additional criterion for eruption forecasting, and for decision making in the definition of volcanic alert levels.

  7. Evidence for Tectonic Activity During the Mature Harappan Civilization, 2600-1800 BCE

    NASA Astrophysics Data System (ADS)

    Grijalva, K. A.; Kovach, R. L.; Nur, A. M.

    2006-12-01

    The mature Harappan civilization located in Pakistan and India dates from 2600 to 1800 BCE. By combining seismic data, three-dimensional elastic dislocation modeling, and archaeological findings we examined the role that earthquakes played in the demise of Harappan settlements. The study focuses on three different geographical regions: Gujarat, the Sarasvati-Ghaggar-Hakra River valley, and the Makran coast of Pakistan. In Gujarat, the fluvial system of the Rann of Kachchh has undergone significant changes. The Rann of Kachchh formed as a delta for three rivers, becoming an inland sea during the time of Alexander the Great, and ultimately a salty marsh. These changes were brought about by a combination of sea level changes, the truncation of the three rivers by tectonic uplift and the deepening of the Rann by earthquake induced subsidence. Events analogous to the 1819 Allah Bund earthquake, which dammed the Puran River for seven years, would have significantly altered the water source for downstream settlements. Data from the recent 2001 Bhuj event shows that Harappan settlements would have suffered considerable shaking damage from an analogous historical event. Archaeological studies to date have found direct evidence for of at least one large earthquake at Dholavira in 2200 BCE. A number of the mature Harappan settlements are located along the dry Sarasvati-Ghaggar-Hakra river system. The decline of these sites coincides with the divergence of the Sarasvati-Ghaggar-Hakra system to the Indus and Ganga river systems. A succession of earthquakes, along with a period of aridity, likely led to the disappearance of the Sarasvati-Ghaggar-Hakra system. Although this region has not had any large earthquakes in historic times, there is archaeological evidence of two large events at the Harappan site of Kalibangan, at 2900 and 2700 BCE. Along the Makran coast two settlements, believed to have been Harappan seaports, are now located tens of kilometers inland. Changes in sea

  8. Ganges-Brahmaputra Delta: Balance of Subsidence, Sea level and Sedimentation in a Tectonically-Active Delta (Invited)

    NASA Astrophysics Data System (ADS)

    Steckler, M. S.; Goodbred, S. L.; Akhter, S. H.; Seeber, L.; Reitz, M. D.; Paola, C.; Nooner, S. L.; DeWolf, S.; Ferguson, E. K.; Gale, J.; Hossain, S.; Howe, M.; Kim, W.; McHugh, C. M.; Mondal, D. R.; Petter, A. L.; Pickering, J.; Sincavage, R.; Williams, L. A.; Wilson, C.; Zumberge, M. A.

    2013-12-01

    Bangladesh is vulnerable to a host of short and long-term natural hazards - widespread seasonal flooding, river erosion and channel avulsions, permanent land loss from sea level rise, natural groundwater arsenic, recurrent cyclones, landslides and huge earthquakes. These hazards derive from active fluvial processes related to the growth of the delta and the tectonics at the India-Burma-Tibet plate junctions. The Ganges and Brahmaputra rivers drain 3/4 of the Himalayas and carry ~1 GT/y of sediment, 6-8% of the total world flux. In Bangladesh, these two great rivers combine with the Meghna River to form the Ganges-Brahmaputra-Meghna Delta (GBMD). The seasonality of the rivers' water and sediment discharge is a major influence causing widespread flooding during the summer monsoon. The mass of the water is so great that it causes 5-6 cm of seasonal elastic deformation of the delta discerned by our GPS data. Over the longer-term, the rivers are also dynamic. Two centuries ago, the Brahmaputra River avulsed westward up to 100 km and has since captured other rivers. The primary mouth of the Ganges has shifted 100s of km eastward from the Hooghly River over the last 400y, finally joining the Brahmaputra in the 19th century. These avulsions are influenced by the tectonics of the delta. On the east side of Bangladesh, the >16 km thick GBMD is being overridden by the Burma Arc where the attempted subduction of such a thick sediment pile has created a huge accretionary prism. The foldbelt is up to 250-km wide and its front is buried beneath the delta. The main Himalayan thrust front is <100 km north, but adjacent to the GBMD is the Shillong Massif, a 300-km long, 2-km high block of uplifted Indian basement that is overthrusting and depressing GBMD sediments to the south. The overthrusting Shillong Massif may represent a forward jump of the Himalayan front to a new plate boundary. This area ruptured in a ~M8 1897 earthquake. Subsidence from the tectonics and differential

  9. Active Tectonics In The Rukwa Rift (sw Tanzania): A Study of The Potential For Large Earthquakes In A Continental Rift.

    NASA Astrophysics Data System (ADS)

    Kervyn, F.

    The Rukwa rift is a deep sedimentary basin that is considered as a tectonic trans- fer zone between the Tanganyika and the Malawi troughs. The tectonic evolution of the depression is controlled by the reactivation of proterozoic structures and started with the deposition of the permo-triasic Karoo sediments. In the southeast, the rift is divided into two facing half graben separated by a Precambrian horst, whereas its northwestern part has a more symmetrical graben structure. Although most of the vertical displacement is accommodated by the Lupa eastern boundary fault, onshore shallow seismic profiles have confirmed the co-occurrence of intrabasin synthetic- and strike-slip faults within the sub surface sediments. Both normal and dextral strike-slip movement are indeed observed in the basin in response to the E-W to WNW-SSE ex- tension. The region has a moderate seismic activity and the earthquakes magnitude is generally below M 6.5. However, a M 7.4 earthquake occurred in the Rukwa region in 1910 but its exact location remains uncertain. The current research aimed at the identi- fication of active faults within the recent deposits of the basin by the combination in a GIS of radar interferometric data with topographical and geological maps, geophysical data, and field observations. Radar interferometry (InSAR) was found to be especially suitable for DEM computation in low relief areas where available topographic data are limited in accuracy. Numerous topographic lineaments were observed on InSAR DEM, and follow two main directions, both oblique to the main NW-SE trend of the rift. On the one hand, the GIS analysis confirms that the observed lineaments corre- spond to real natural alignment such like the drainage for example, and are therefore not related to atmospheric artefacts. On the other hand, the field observations revealed that in most cases, the topographic lineaments are very subtle and difficult to identify. However, direct correlations with tectonic

  10. Geochemical and tectonic implications on plate-interface evolution achieved from high-pressure ultramafic rocks in mélange settings

    NASA Astrophysics Data System (ADS)

    Cannaò, E.; Agostini, S.; Scambelluri, M.; Tonarini, S.

    2014-12-01

    Geochemical studies of fluid-mobile elements (FME) joined with B, Sr and Pb isotopic analyses of high-pressure mélanges terranes help constraining tectonic processes and mass transfer during accretion of slab and suprasubduction mantle in plate-interface domains. Here we focus on ultramafic rocks from two plate interface settings: (I) metasediment-dominated mélange (Cima di Gagnone, CdG, Adula Unit), where eclogite-facies de-serpentinized garnet peridotite and chlorite harzburgite lenses are embedded in paraschist; (II) dominated by high-pressure serpentinite (Erro-Tobbio, ET, and Voltri Units, VU, Ligurian Alps). CdG metaperidotite shows low [B], negative δ 11B and high Sr and Pb isotopic ratios. As, Sb loss from metasediment and gain by garnet and chlorite metaperidotite points to exchange between the two systems. Presence of As and Sb in eclogite-facies peridotite minerals and preferential low-T mobility of such elements suggest that exchange was during early subduction burial and prior to eclogitization. Based on high [B], positive δ11B, oxygen and hydrogen isotope, the ET serpentinties were recently interpreted as supra-subduction mantle flushed by slab fluids (Scambelluri & Tonarini, 2012, Geology, 40, 907-910). Their 206Pb/204Pb and 87Sr/86Sr isotope ratios range between 18.300-18.514 and 0.7048-0.7060, respectively. Compared with ET rocks, VU serpentinites have higher As, Sb (up to 1.3 and 0.39 ppm, respectively) and are enriched in radiogenic Sr (up to 0.7105 87Sr/86Sr). This signature reflects interaction with fluids that exchanged with sedimentary rocks, either in outer rise environments or during accretion atop the slab. In the above cases, the serpentinized mantle rocks fingerprint interaction with fluids from different sources, indicating a timing of accretion to plate interface domains. We provide evidence that serpentinized mantle slices of different size and provenance (slab or wedge) accreted to plate interface domains since early subduction

  11. Provenance and tectonic setting of the Paleo- to Mesoproterozoic Dongchuan Group in the southwestern Yangtze Block, South China: Implication for the breakup of the supercontinent Columbia

    NASA Astrophysics Data System (ADS)

    Wang, Wei; Zhou, Mei-Fu

    2014-01-01

    The Paleoproterozoic to Mesoproterozoic (1742-1503 Ma) Dongchuan Group in the southwestern Yangtze Block is a rift-related sedimentary sequence that was associated with the breakup of the supercontinent Columbia and is particularly important for the possible linkage between the Yangtze Block and other continents in Columbia. The Dongchuan Group consists of the Yinmin, Luoxue, Etouchang and Luzhijiang formations from the base upward. Sandstones from the Yinmin Formation are mainly arkose containing dominant K-feldspar with subordinate plagioclase and quartz. Abundant feldspar and high Qm/Q ratios (0.94-1) are indicative of plutonic sources. These sandstones have high La/Sc (3.06 to 4.32), low Sc/Th (0.74 to 1.15) and Co/Th (0.85 to 1.52) and highly evolved Nd isotopes (εNd(t) = - 6.2 to - 8.2), consistent with an old, felsic igneous source. Detrital zircons of this formation have two major age groups at 2602-2887 Ma and 2224-2392 Ma. Siltstones of the Etouchang Formation have detrital zircons with a prominent age peak at ~ 2560 Ma and several subordinate peaks at ~ 2180 Ma, ~ 2100 Ma and ~ 1900 Ma. They have high Sc/Th (1.00-7.08), Co/Th (0.13 to 6.31) and εNd(t) (- 2.1 to - 6.7), significantly different from the Yinmin Formation. The Yinmin Formation is interpreted to deposit during the initial stage of extensional rifting receiving detritus of granites and TTG mainly from uplifted shoulder. The Etouchang Formation more likely formed in a passive margin with sedimentary material largely from cratonic sources. Paleoproterozoic to Mesoproterozoic rift basins in the southwestern Yangtze Block, north Australia and northwestern Laurentia have remarkably similar provenance and tectonic setting in their lower part (1742-1596 Ma), but significantly different since the onset of the Etouchang Formation (ca. 1596 Ma). Therefore, the southwestern Yangtze Block was likely connected with the north Australia and northwestern Laurentia in Columbia and drifted away from these

  12. Geomorphic evidence of possible tectonic activity in the Mississippi embayment of southeast Missouri

    SciTech Connect

    Steckel, P.J.

    1993-03-01

    Several distinct topographic and geomorphic features in the Mississippi Embayment of southeast Missouri may provide direct and indirect evidence of tectonic influence on surface processes. First, the Pascola bulge is an extremely subtle feature, which probably trends northwest from about Caruthersville to northeast of Kennett and may or may not be associated with the Pascola Arch. The Pascola bulge may be responsible for an abrupt change in both the direction and meander pattern of the natural channel of the Little river near Wardell; a bifurcation of the natural channel of the Little river west of Wardell; the closing off of a natural, navigable waterway between the Mississippi and St. Francis rivers (in the early 1800s); and, at least partly, the extremely inefficient Caruthersville Bend of the Mississippi River. Second, the Canalou nickpoint is an abrupt and distinct change in slope that coincides with both a series of northwest-trending surface lineaments and a southeast projection of the Black fault, located in the Paleozoic rock of the Ozark Uplift. The Canalou nickpoint may suggest a structural feature in the area west of Sikeston. Finally, a subtle yet distinctly irregular surface topography and the near obliteration of topographic expression of the natural channel of the Little River suggest that sunklands may have occurred in areas southeast of Kennett and from near Hornersville south to at least the Missouri-Arkansas state line.

  13. Project ACE Activity Sets. Book III: Grades 8 through 12.

    ERIC Educational Resources Information Center

    Eden City Schools, NC.

    Eleven activity sets for students in grades 8 through 12 are designed to supplement courses in citizenship and U.S. history and government. "The Civil War That Could Have Been" creates a hypothetical situation which requires the participant to analyze the causes of the Civil War. In "History on TV -- Enemy or Ally of the Social Studies Program,"…

  14. Geochemical characteristics of the Triassic Tethys-turbidites in northwestern Sichuan, China: Implications for provenance and interpretation of the tectonic setting

    NASA Astrophysics Data System (ADS)

    Gu, X. X.

    1994-11-01

    The Triassic Tethys graywacke-slate turbidites in the northwestern Sichuan, China have been analysed for major and trace elements and petrographically studied. Compared to Phanerozoic turbidites, the turbidites in this study are quartz-intermediate (average 55%) in composition and are characterized geochemically by their moderate Fe 2O ∗3 + MgO (9.28 ± 2.84%), TiO 2 (0.72 ± 0.17%) contents and Al 2O 3/SiO 2 (0.25 ± 0.10) ratios; moderate abundances of ferromagnesian trace elements ( Co = 15 ± 8 ppm, Cr = 113 ± 72 ppm, Ni = 14 + 9 ppm, Sc = 12 ± 4 ppm, etc.); and moderate contents of incompatible elements, such as Th (11 ± 3 ppm), U (3 ± 0.7 ppm), Zr (170 ± 64 ppm), Hf (4 ± 1 ppm) and total REEs (159 ± 33 ppm). In general, the slates show systematically higher Fe 2O ∗3 + MgO, Sc, Co and Eu/Eu∗, but lower solLa/Sc and Th/Sc than the associated graywackes, suggesting that various provenance components may separate into different grain-size fractions during sedimentary sorting processes, that is, the more mafic materials tended to incorporate into the sedimentary record for the clay-size fraction. Framework modes and geochemical data indicate that the turbidites were mainly derived from a recycled orogenic provenance characterized chiefly by sedimentary-metasedimentary rocks and granite-gneisses, similar to the upper continental crust, but with a variable admixture of continental island arc volcanic components. Flysch deposition took place in a back arc basin situated between an active continental margin (the Kunlun-Qinling fold belt) and a continental island arc (the Yidun island arc). Weathering conditions in the source area significantly influenced the composition and distribution of elements in the sediments. With the elapse of time during sedimentation, the degree of chemical weathering in the provenance became intense while the tectonic activity decreased gradually.

  15. Tectonic Controls on the Volumes and Petrologic Evolution of Pantellerite-Trachyte-Phonolite Volcanoes in a Continental Rift Setting, Marie Byrd Land, Antarctica

    NASA Astrophysics Data System (ADS)

    Lemasurier, W. E.

    2010-12-01

    some basanite magmas within the stability field of kaersutite, but allowed others to rise directly to upper crustal reservoirs, allowing a range of FC schemes to produce diverse felsic rock types. Mantle plume activity has produced syn-volcanic doming and large volumes of basalt magma in MBL over the past ~30 m.y. A stationary plate environment has allowed a continued focus of magma generation, storage, and eruption beneath the same volcanic centers throughout this time. The sum of these tectonic factors has resulted in an environment that was optimal for producing large volumes of felsic rock by FC.

  16. Fluid-Faulting Interactions Examined Though Massive Waveform-Based Analyses of Earthquake Swarms in Volcanic and Tectonic Settings: Mammoth Mountain, Long Valley, Lassen, and Fillmore, California Swarms, 2014-2015

    NASA Astrophysics Data System (ADS)

    Shelly, D. R.; Ellsworth, W. L.; Prejean, S. G.; Hill, D. P.; Hardebeck, J.; Hsieh, P. A.

    2015-12-01

    Earthquake swarms, sequences of sustained seismicity, convey active subsurface processes that sometimes precede larger tectonic or volcanic episodes. Their extended activity and spatiotemporal migration can often be attributed to fluid pressure transients as migrating crustal fluids (typically water and CO2) interact with subsurface structures. Although the swarms analyzed here are interpreted to be natural in origin, the mechanisms of seismic activation likely mirror those observed for earthquakes induced by industrial fluid injection. Here, we use massive-scale waveform correlation to detect and precisely locate 3-10 times as many earthquakes as included in routine catalogs for recent (2014-2015) swarms beneath Mammoth Mountain, Long Valley Caldera, Lassen Volcanic Center, and Fillmore areas of California, USA. These enhanced catalogs, with location precision as good as a few meters, reveal signatures of fluid-faulting interactions, such as systematic migration, fault-valve behavior, and fracture mesh structures, not resolved in routine catalogs. We extend this analysis to characterize source mechanism similarity even for very small newly detected events using relative P and S polarity estimates. This information complements precise locations to define fault complexities that would otherwise be invisible. In particular, although swarms often consist of groups of highly similar events, some swarms contain a population of outliers with different slip and/or fault orientations. These events highlight the complexity of fluid-faulting interactions. Despite their different settings, the four swarms analyzed here share many similarities, including pronounced hypocenter migration suggestive of a fluid pressure trigger. This includes the July 2015 Fillmore swarm, which, unlike the others, occurred outside of an obvious volcanic zone. Nevertheless, it exhibited systematic westward and downdip migration on a ~1x1.5 km low-angle, NW-dipping reverse fault at midcrustal depth.

  17. Task 1 quarternary tectonics

    SciTech Connect

    Bell, J.W.

    1994-12-31

    Activities on the task of quarternary tectonics for the Yucca Mountain Site investigations are described. Technical topics include: A preliminary reveiw of Bare Mountain Trench; A preliminary detailed lineament map of the Southwestern part of the proposed repository; A discussion on the 1994 Double Spring Flat, Nevada earthquake; and evidence for temporal clustering.

  18. Tectonics, magmatism and paleo-fluid distribution in a strike-slip setting: Insights from the northern termination of the Liquiñe-Ofqui fault System, Chile

    NASA Astrophysics Data System (ADS)

    Pérez-Flores, Pamela; Cembrano, José; Sánchez-Alfaro, Pablo; Veloso, Eugenio; Arancibia, Gloria; Roquer, Tomás

    2016-06-01

    This study addresses the interplay between strain/stress fields and paleo-fluid migration in the Southern Andean Volcanic Zone (SVZ). The SVZ coexists with the margin-parallel Liquiñe-Ofqui Fault System (LOFS) and with NW-striking Andean Transverse Faults (ATF). To tackle the role of different fault-fracture systems on deformation distribution and magma/fluid transport, we map the nature, geometry and kinematics of faults, veins and dikes at various scales. Fault-slip data analysis yields stress and strain fields from the full study area data base (regional scale) and fault zones representative of each fault system (local scale). Regional scale strain analysis shows kinematically heterogeneous faulting. Local strain analyses indicate homogeneous deformation with NE-trending shortening and NW-trending extension at NNE-striking Liquiñe-Ofqui master fault zones. Strain axes are clockwise rotated at second order fault zones, with ENE-trending shortening and NNW-trending stretching. The ATF record polyphasic deformation. Conversely, stress field analysis at regional scale indicates a strike-slip dominated transpressional regime with N64°E-trending σ1 and N30°W-trending σ3. Deformation is further partitioned within the arc through NNE-striking dextral-reverse faults, NE-striking dextral-normal faults and NW-striking sinistral-reverse faults with normal slip activation. The regional tectonic regime controls the geometry of NE-striking dikes and volcanic centers. NE-striking faults record local stress axes that are clockwise rotated with respect to the regional stress field. NNE- and NE-striking faults are favorably oriented for reactivation under the regional stress field and show poorly-developed damage zones. Conversely, NW-striking fault systems, misoriented under the regional stress field, show multiple fault cores, wider damage zones and dense vein networks. Deformation driven by oblique subduction is partially partitioned into strike-slip and shortening

  19. Variations of fluvial tufa sub-environments in a tectonically active basin, Pleistocene Teruel Basin, NE Spain

    NASA Astrophysics Data System (ADS)

    Camuera, Jon; Alonso-Zarza, Ana M.; Rodríguez-Berriguete, Álvaro; Meléndez, Alfonso

    2015-12-01

    The Pleistocene Tortajada fluvial deposit occurs in the eastern active margin of the Teruel Basin. It developed in the early stages of opening of the basin and at present is disconnected to the Alfambra River. The preserved deposits show that the fluvial system consisted in three different sub-environments including: Upper Terraces, Ponds and Cascades. The main facies are framestones of stems, phytoclastic rudstone, framestone of bryophytes, peloidal and filamentous stromatolites, mudstone and detrital (conglomerates and slope-breccias) facies. These facies are arranged in three different sequence types, all of them showing a lower detrital term followed by pond and, in cases, cascade deposits. The microfacies analyses reveal that both biotic and abiotic processes performed an important role in the deposition within the river. Isotopic analyses (δ18O from - 8.58‰ to - 6.70‰ VPDB and δ13C from - 7.44‰ to - 3.97‰ VPDB) are indicative of meteoric water within a hydrologically open system. The carbonate hinterland rocks, together with a semi-arid to sub-humid climate favored carbonate accumulation within the river. Our results point out that the location, morphology and sedimentary sequences of the Tortajada fluvial system had an important tectonic control. The situation of the main and secondary faults controlled the paleomorphology of the river floor. Thus cascades are found in areas of important step faults, whereas the spaces between faults were occupied by fluviatile/lacustrine areas. In addition the development of the different sedimentary sequences was also a reflection of movements of these faults. In short, our study may confirm that tectonism is an important control on tufa development.

  20. Seismicity study of volcano-tectonic in and around Tangkuban Parahu active volcano in West Java region, Indonesia

    NASA Astrophysics Data System (ADS)

    Ry, Rexha V.; Priyono, A.; Nugraha, A. D.; Basuki, A.

    2016-05-01

    Tangkuban Parahu is one of the active volcano in Indonesia located about 15 km northern part of Bandung city. The objective of this study is to investigate the seismic activity in the time periods of January 2013 to December 2013. First, we identified seismic events induced by volcano-tectonic activities. These micro-earthquake events were identified as having difference of P-wave and S-wave arrival times less than three seconds. Then, we constrained its location of hypocenter to locate the source of the activities. Hypocenter determination was performed using adaptive simulated annealing method. Using these results, seismic tomographic inversions were conducted to image the three-dimensional velocity structure of Vp, Vs, and the Vp/Vs ratio. In this study, 278 micro-earthquake events have been identified and located. Distribution of hypocenters around Tangkuban Parahu volcano forms an alignment structure and may be related to the stress induced by magma below, also movement of shallow magma below Domas Crater. Our preliminary tomographic inversion results indicate the presences of low Vp, high Vs, and low Vp/Vs ratio that associate to accumulated young volcanic eruption products and hot material zones.

  1. Basement and crustal structure of the Davis Sea region (East Antarctica): implications for tectonic setting and continent to oceanic boundary definition

    USGS Publications Warehouse

    Guseva, Y.B.; Leitchenkov, G.L.; Gandyukhin, V.V.; Ivanov, S.V.

    2007-01-01

    This study is based on about 8400 km of MCS, magnetic and gravity data as well as 20 sonobuoys collected by the Russian Antarctic Expedition during 2003 and 2004 in the Davis Sea and adjacent areas between 80°E and 102°E. Major tectonic provinces and features are identified and mapped in the study region including: 1) A marginal rift with a the extended continental crust ranging 130 to more than 200 km in width; 2) The marginal volcanic plateau of the Bruce Bank consisting of the Early Cretaceous igneous rocks; 3) The Early Cretaceous and Late Cretaceous−Paleogene oceanic basins; and 4) The Early Cretaceous igneous province of the Kerguelen Plateau. Four major horizons identified in the sedimentary cover of the Davis Sea region are attributed to main tectonic events and/or paleoenvironmental changes.

  2. Geochemistry of the Jurassic and Upper Cretaceous shales from the Molango Region, Hidalgo, eastern Mexico: Implications for source-area weathering, provenance, and tectonic setting

    NASA Astrophysics Data System (ADS)

    Armstrong-Altrin, John S.; Nagarajan, Ramasamy; Madhavaraju, Jayagopal; Rosalez-Hoz, Leticia; Lee, Yong Il; Balaram, Vysetti; Cruz-Martínez, Adriana; Avila-Ramírez, Gladis

    2013-04-01

    This study focuses on the Jurassic (Huayacocotla and Pimienta Formations) and Upper Cretaceous (Méndez Formation) shales from the Molango Region, Hidalgo, Mexico. In this article, we discuss the mineralogy, major, and trace element geochemistry of the Mesozoic shales of Mexico. The goal of this study is to constrain the provenance of the shales, which belong to two different periods of the Mesozoic Era and to understand the weathering conditions and tectonic environments of the source region.

  3. Integrating 40Ar-39Ar, 87Rb-87Sr and 147Sm-143Nd geochronology of authigenic illite to evaluate tectonic reactivation in an intraplate setting, central Australia

    NASA Astrophysics Data System (ADS)

    Middleton, Alexander W.; Uysal, I. Tonguç; Bryan, Scott E.; Hall, Chris M.; Golding, Suzanne D.

    2014-06-01

    The Warburton-Cooper basins, central Australia, include a multitude of reactivated fracture-fault networks related to a complex, and poorly understood, tectonic evolution. We investigated authigenic illites from a granitic intrusion and sedimentary rocks associated with prominent structural features (Gidgealpa-Merrimelia-Innamincka Ridge and the Nappamerri Trough). These were analysed by 40Ar-39Ar, 87Rb-87Sr and 147Sm-143Nd geochronology to explore the thermal and tectonic histories of central Australian basins. The combined age data provide evidence for three major periods of fault reactivation throughout the Phanerozoic. While Carboniferous (323.3 ± 9.4 Ma) and Late Triassic ages (201.7 ± 9.3 Ma) derive from basin-wide hydrothermal circulation, Cretaceous ages (∼128 to ∼86 Ma) reflect episodic fluid flow events restricted to the synclinal Nappamerri Trough. Such events result from regional extensional tectonism derived from the transferral of far-field stresses to mechanically and thermally weakened regions of the Australian continent. Specifically, Cretaceous ages reflect continent-wide transmission of tensional stress from a >2500 km long rifting event on the eastern (and southern) Australian margin associated with break-up of Gondwana and opening of the Tasman Sea. By integrating 40Ar-39Ar, 87Rb-87Sr and 147Sm-143Nd dating, this study highlights the use of authigenic illite in temporally constraining the tectonic evolution of intracontinental basins that would otherwise remain unknown. Furthermore, combining Sr- and Ar-isotopic systems enables more accurate dating of authigenesis whilst significantly reducing geochemical pitfalls commonly associated with these radioisotopic dating methods.

  4. Active tectonics of North Haji Abad (Hormozgan region) in south of Iran

    NASA Astrophysics Data System (ADS)

    shafiei bafti, amir

    2014-05-01

    Zagros Active Fold -thrust Belt is situated in the northern margin of the Arabian Plat and formed due to shortening, thickening and uplift of tethys sedimentary basin between Arabian and Iranian plates. In this study, the rate of uplift in the northern margin of the Zagros Mountains in southern Iran are examined. The Zagros fault zone in this region is composed of a set faults, including Deragah, Haji Abad, Tezerj and several other faults and also we call these branches from F1 to F8. These segments puts from northwest to the East- Southeast. Based on field surveys and Geological maps, we prepared a structural map from major faults of Zagros fault system for identify faults pattern and estimating of uplift rate movements in Zagros fault. Three methods used to calculation of uplift rate: A: Asymmetry index Accordance with the procedure, in studied area, northeast drainage are longer than of southwest drainage and east minor drainages also longer than the west side drainages, Uplifting in this region is characterized by mentioned asymmetry factor. The amount of this index is AF=71.81. B. Interaction between the faults movements and erosion process We comparison contrast between uplifting movement rates and erosion rates in different parts of studied region by Smf and other indexes. Average amount of Smf=1.1. C. Evaluation of Uplift rate of alluvial terraces was performed by sediment ages and terraces height. We surveyed Quaternary facieses which have ages between 17,000 and 30,000 years old. the rate of uplifting for each fault is follows : Deragah fault and F8 fault between 1.0 to 1.85mm per year and F7, F6, F5, and F4 faults, have a rate Uplifting between 0.6 to 1.0 mm per year and the rate of Uplift for other faults is between 0.04 to 0.06 mm per year. According to our studies, uplift rates in north -east and south-west more than other regions The minimum rate at different stations are about 0.5mm/y to 0.93mm/y and its maximum is 0.88 mm/y to 1.47mm/y.

  5. Characteristics of helium isotopes in natural gas and its tectonic implication in Bohai Bay Basin

    NASA Astrophysics Data System (ADS)

    Ding, Weiwei; Dai, Jinxin; Yang, Shufeng; Chen, Hanlin

    2006-09-01

    Analysis on helium isotopes in natural gas in Bohai Bay Basin showed their mantle-origin indicated by high3He/4He ratio. The span of3He/4He ratio increased from west to east. This pattern implied a close relationship to the local tectonic setting. Bohai Bay Basin experienced intensive neo-tectonic activities in the Cenozoic. Widespread faulted-depressions and strong volcanic eruptions manifested its extensional tectonics. Abiogenic natural gas could be released from magmas and migrate upward through deep faults during the extension. Tectonic conditions in the area would favor upward invasion and reservation of mantle-originated helium. Furthermore, with decrease of convergence rate between the Pacific and the Eurasia Plate, the subduction slab of the Pacific Plate rolled back and became steeper, resulting in mantle flow and other tectonic activities migrating from west to east in nature, and caused the variation in isotopic helium ratios.

  6. Tectonic Maps of the Poles

    NASA Technical Reports Server (NTRS)

    2002-01-01

    These tectonic relief maps of the north (left, view large [540k]) and south (right, view large [411k]) poles are the result of new satellite-based technologies which are being used to analyze tectonic activity in the Earth's crust. These maps, known as Digital Tectonic Activity Maps (DTAMs), synoptically depict the architecture of the Earth's crust including current and past tectonic activity. This is significant because it permits researchers to view broad zones of activity over the entire surface of the Earth, rather than focusing on single boundary features. By looking at these 'big pictures,' scientists can possibly identify regions of activity which were not previously recognized or mapped using traditional methods. For more information, see: DTAM web site Putting Earthquakes in Their Place Images courtesy Brian Montgomery, NASA GSFC; data by Paul Lowman and Jacob Yates, NASA GSFC

  7. An objective method for the assessment of fluid injection-induced seismicity and application to tectonically active regions in central California

    NASA Astrophysics Data System (ADS)

    Goebel, T. H. W.; Hauksson, E.; Aminzadeh, F.; Ampuero, J.-P.

    2015-10-01

    Changes in seismicity rates, whether of tectonic or of induced origin, can readily be identified in regions where background rates are low but are difficult to detect in seismically active regions. We present a novel method to identify likely induced seismicity in tectonically active regions based on short-range spatiotemporal correlations between changes in fluid injection and seismicity rates. The method searches through the entire parameter space of injection rate thresholds and determines the statistical significance of correlated changes in injection and seismicity rates. Applying our method to Kern County, central California, we find that most earthquakes within the region are tectonic; however, fluid injection contributes to seismicity in four different cases. Three of these are connected to earthquake sequences with events above M4. Each of these sequences followed an abrupt increase in monthly injection rates of at least 15,000 m3. The probability that the seismicity sequences and the abrupt changes in injection rates in Kern County coincide by chance is only 4%. The identified earthquake sequences display low Gutenberg-Richter b values of ˜0.6-0.7 and at times systematic migration patterns characteristic for a diffusive process. Our results show that injection-induced pressure perturbations can influence seismic activity at distances of 10 km or more. Triggering of earthquakes at these large distances may be facilitated by complex local geology and faults in tectonically active regions. Our study provides the first comprehensive, statistically robust assessment of likely injection-induced seismicity within a large, tectonically active region.

  8. Tracking Activities in Complex Settings Using Smart Environment Technologies

    PubMed Central

    Singla, Geetika; Cook, Diane J.; Schmitter-Edgecombe, Maureen

    2009-01-01

    The pervasive sensing technologies found in smart homes offer unprecedented opportunities for providing health monitoring and assistance to individuals experiencing difficulties living independently at home. A primary challenge that needs to be tackled to meet this need is the ability to recognize and track functional activities that people perform in their own homes and everyday settings. In this paper we look at approaches to perform real-time recognition of Activities of Daily Living. We enhance other related research efforts to develop approaches that are effective when activities are interrupted and interleaved. To evaluate the accuracy of our recognition algorithms we assess them using real data collected from participants performing activities in our on-campus smart apartment testbed. PMID:20019890

  9. Late Pleistocene Alberca de Guadalupe maar volcano (Zacapu basin, Michoacán): Stratigraphy, tectonic setting, and paleo-hydrogeological environment

    NASA Astrophysics Data System (ADS)

    Kshirsagar, Pooja; Siebe, Claus; Guilbaud, Marie Noëlle; Salinas, Sergio; Layer, Paul W.

    2015-10-01

    The Late Pleistocene (~ 21,000 yr BP) Alberca de Guadalupe maar is one of the few phreatomagmatic volcanoes occurring within the scoria-cone dominated Plio-Quaternary Michoacán-Guanajuato Volcanic Field. The scarcity of this type of volcano implies that conditions favoring their formation are rarely met in this region. We identify these factors by implementing current methods of investigation with emphasis on hydrogeological conditions. We present the stratigraphy (including a set of 40Ar/39Ar and 14C dates) of the SE margin of the Zacapu intermontane tectonic basin, where the maar just forms a hole (~ 1 km in diameter, ~ 150 m deep, bearing a ~ 9 m deep lake) in the otherwise planar topography of the underlying early Pleistocene lava flows of the Cerro Pelón scoria cone. The maar is composed of typical phreatomagmatic surge deposits that are poorly sorted and rich in accidental lithics (> 60 wt.% of the deposit) with few juveniles (basaltic andesite, SiO2 = 54-58 wt.%). The entire structure is cut by an ENE-WSW trending normal fault and is underlain by andesite lavas and silicic ignimbrites (partly inferred from xenoliths encountered in the maar deposits) that are Miocene to Early Pleistocene in age. The crater is at the center of a N-S elongated drainage basin surrounded by topographic highlands that channel water with high hydraulic pressure from most directions towards the location of the maar. This geometric configuration was already in existence at the time of the maar-forming eruption, but the climate was different. Colder and more humid conditions during the Last Glacial Maximum (Cw2-climate type, annual precipitation of > 1000 mm) favored the saturation of the fractured shallow aquifer system (hydraulic conductivity of 10- 8 to 10- 7 m/s) that supplied sufficient groundwater at a high flow rate directed towards the center of the basin. Upon contact near surface (< 200 m) with the rising dike of basaltic andesite magma, the continuous supply of both dike

  10. Interplay between active and past tectonics in the Hellenic Arc (Greece): Geological and geomorphic evidences from Kythira Island

    NASA Astrophysics Data System (ADS)

    Fernández-Blanco, David; de Gelder, Gino; Delorme, Arthur; Lacassin, Robin; Armijo, Rolando

    2016-04-01

    The Hellenic Arc undergoes the largest convergence velocity and highest seismic activity among Mediterranean subduction systems. The outer-arc high islands of the Hellenic Arc are thus key to understand the mode of deformation of the crust during subduction and the mechanisms behind vertical motions at the front of overriding plates, here and elsewhere. Kythira Island, located between SW Peloponnese and NE Crete, provides an exceptional opportunity to understand the interaction between past and active tectonics in the Hellenic Arc. The recent uplift of the Kythira Island is marked in its landscape as paleosurfaces, marine terraces, abandon valleys and gorges. Together with the sedimentary record of the island and its geologic structures, we attempt to reconstruct its tectonic evolution since the latest Miocene. Here, we present exceptionally detailed geological and geomorphological maps of the Kythira Island based on fieldwork, Pleiades satellite imagery and 2-m resolution DEM, as well as the analyses of marine terraces and river network morphometrics. Pliocene or younger infill sequences rest atop of Palaeocene or older rocks in several marine basins in the island. In the largest marine basin, we found a stratigraphic sequence with a (tilted) continental conglomerate at the base, passing upwards to a disconformal subhorizontal conglomerate, calcarenites and fine sands, and terminating with a marine conglomerate. This marine conglomerate acts as a "cap rock" that marks the topography and shapes the highermost, and most extensive, low-relief surface. Overall, the infill sequence onlaps basement with the exception of the western margin where normal faults partly controlled the deposition of its lower sector. These faults reactivated older Hellenic fold-and-thrust structures, parallel to the subduction trench, and were not active during the maximum marine transgression that led to the deposition of the subhorizontal part of the infill sequence, including the topmost

  11. Spiral tectonics

    NASA Astrophysics Data System (ADS)

    Hassan Asadiyan, Mohammad

    2014-05-01

    Spiral Tectonics (ST) is a new window to global tectonics introduced as alternative model for Plate Tectonics (PT). ST based upon Dahw(rolling) and Tahw(spreading) dynamics. Analogues to electric and magnetic components in the electromagnetic theory we could consider Dahw and Tahw as components of geodynamics, when one component increases the other decreases and vice versa. They are changed to each other during geological history. D-component represents continental crust and T-component represents oceanic crust. D and T are two arm of spiral-cell. T-arm 180 degree lags behind D-arm so named Retard-arm with respect to D or Forward-arm. It seems primary cell injected several billions years ago from Earth's center therefore the Earth's core was built up first then mantel and finally the crust was build up. Crust building initiate from Arabia (Mecca). As the universe extended gravitation wave swirled the earth fractaly along cycloid path from big to small scale. In global scale (order-0) ST collect continents in one side and abandoned Pacific Ocean in the other side. Recent researches also show two mantels upwelling in opposite side of the Earth: one under Africa (tectonic pose) and the other under Pacific Ocean (tectonic tail). In higher order (order-1) ST build up Africa in one side and S.America in the other side therefore left Atlantic Ocean meandered in between. In order-n e.g. Khoor Musa and Bandar-Deylam bay are seen meandered easterly in the Iranian part but Khoor Abdullah and Kuwait bay meandered westerly in the Arabian part, they are distributed symmetrically with respect to axis of Persian Gulf(PG), these two are fractal components of easterly Caspian-wing and westerly Black Sea-wing which split up from Anatoly. Caspian Sea and Black Sea make two legs of Y-like structure, this shape completely fitted with GPS-velocity map which start from PG and split up in the Catastrophic Point(Anatoly). We could consider PG as remnants of Ancient Ocean which spent up

  12. Flare-Shaped Acoustic Anomalies in the Water Column Along the Ecuadorian Margin: Relationship with Active Tectonics and Gas Hydrates

    NASA Astrophysics Data System (ADS)

    Francois, Michaud; Noël, Proust Jean; Alexandre, Dano; Yves, Collot Jean; Daniella, Guiyeligou Grâce; José, Hernández Salazar María; Gueorgui, Ratzov; Carlos, Martillo; Hugo, Pouderoux; Laure, Schenini; Frederic, Lebrun Jean; Glenda, Loayza

    2016-01-01

    With hull-mounted multibeam echosounder data, we report for the first time along the active Ecuadorian margin, acoustic signatures of water column fluid emissions and seep-related structures on the seafloor. In total 17 flare-shaped acoustic anomalies were detected from the upper slope (1250 m) to the shelf break (140 m). Nearly half of the flare-shaped acoustic anomalies rise 200-500 m above the seafloor. The base of the flares is generally associated with high-reflectivity backscatter patches contrasting with the neighboring seafloor. We interpret these flares as caused by fluid escape in the water column, most likely gases. High-resolution seismic profiles show that most flares occur close to the surface expression of active faults, deformed areas, slope instabilities or diapiric structures. In two areas tectonic deformation disrupts a Bottom Simulating Reflector (BSR), suggesting that buried frozen gas hydrates are destabilized, thus supplying free gas emissions and related flares. This discovery is important as it opens the way to determine the nature and origin of the emitted fluids and their potential link with the hydrocarbon system of the forearc basins along the Ecuadorian margin.

  13. Active tectonics of the Devils Mountain Fault and related structures, northern Puget Lowland and eastern Strait of Juan de Fuca region, Pacific Northwest

    USGS Publications Warehouse

    Johnson, Samuel Y.; Dadisman, Shawn V.; Mosher, David C.; Blakely, Richard J.; Childs, Jonathan R.

    2001-01-01

    Information from marine high-resolution and conventional seismic-reflection surveys, aeromagnetic mapping, coastal exposures of Pleistocene strata, and lithologic logs of water wells is used to assess the active tectonics of the northern Puget Lowland and eastern Strait of Juan de Fuca region of the Pacific Northwest. These data indicate that the Devils Mountain Fault and the newly recognized Strawberry Point and Utsalady Point faults are active structures and represent potential earthquake sources.

  14. A systematic overview of the coincidences of river sinuosity changes and tectonically active structures in the Pannonian Basin

    NASA Astrophysics Data System (ADS)

    Petrovszki, Judit; Székely, Balázs; Timár, Gábor

    2012-12-01

    As tectonic movements change the valley slope (low-gradient reaches of valleys, in sedimentary basins), the alluvial rivers, as sensitive indicators, respond to these changes, by varying their courses to accommodate this forcing. In our study sinuosity values, a commonly used characteristic parameter to detect river pattern changes, were studied for the major rivers in the Pannonian Basin in order to reveal neotectonic influence on their planform shape. Our study area comprises the entire Pannonian Basin (330,000 km2) located in eastern Central-Europe, bounded by the Alps, Carpathians and Dinarides. The studied rivers were mostly in their natural meandering state before the main river regulations of the 19th century. The last quasi-natural, non-regulated river planforms were surveyed somewhat earlier, during the Second Military Survey of the Habsburg Empire. Using the digitized river sections of that survey, the sinuosities of the rivers were calculated with different sample section sizes ranging from 5 km to 80 km. Depending on the bank-full discharge, also a 'most representative' section size is given, which can be connected to the neotectonic activity. In total, the meandering reaches of 28 rivers were studied; their combined length is 7406 km. The places where the river sinuosity changed were compared to the structural lines of the "Atlas of the present-day geodynamics of the Pannonian Basin" (Horváth et al., 2006). 36 junctions along 26 structural lines were identified where the fault lines of this neotectonic map crossed the rivers. Across these points the mean sinuosity changed. Depending on the direction of the relative vertical movements, the sinuosity values increased or decreased. There were some points, where the sinuosity changed in an opposite way. Along these sections, the rivers belong to the range of unorganized meandering or there are lithological margins. Assuming that the rivers indicate on-going faulting accurately, some places were found

  15. Evolution of the Late Pleistocene Aspe River (Western Pyrenees, France). Signature of climatic events and active tectonics

    NASA Astrophysics Data System (ADS)

    Nivière, Bertrand; Lacan, Pierre; Regard, Vincent; Delmas, Magali; Calvet, Marc; Huyghe, Damien; Roddaz, Bernard

    2016-03-01

    We make use of the cosmogenic nuclide 10Be exposure to date an alluvial terrace of the Aspe River in the foothills of the northwestern Pyrenees. Initially ascribed to the Rissian glaciation, our dating shows that the terrace was abandoned at 18 ± 2 kyr. In reference to the Late Pleistocene climatic chronology, two kinds of terraces can be distinguished: high-standing fill terraces probably deposited during glacial events and lower cut-in-fill and strath terraces cut during the postglacial river incision. A part of the terrace aggradations could have occurred during the Würmian glacial episodes. Hence, the dated terrace fits in with the prevailing view of incision during climate transitions. Our study also shows that elevation is not a good criterion of terrace correlation, which should be better carried out on the basis of absolute dating. In addition, this dating also suggests a potential Late Pleistocene fault reactivation of the Mail Arrouy thrust in this tectonically active area of the Western Pyrenees.

  16. Late Quaternary tectonic activity and crustal shortening rate of the Bogda mountain area, eastern Tian Shan, China

    NASA Astrophysics Data System (ADS)

    Wu, Chuanyong; Wu, Guodong; Shen, Jun; Dai, Xunye; Chen, Jianbo; Song, Heping

    2016-04-01

    The Bogda mountain range is the highest range among the northern Tian Shan mountains. Based on geologic and geomorphologic field surveys, trench excavation and optically stimulated luminescence (OSL) dating, we targeted the active Fukang fault along the Bogda mountain range and identified the late Quaternary deformation characteristics of this area. We found that the Fukang fault dislocated different geomorphic surfaces of the northern Bogda piedmont. The vertical fault displacement corresponds to the topographic relief of the Bogda over long time scales. Since the late Quaternary, the crustal shortening rate was estimated to be 0.90 ± 0.20 mm/yr, which is less than that of the western segment of the northern Tian Shan. We interpret the Bogda fold and thrust belt to be a thick-skinned structure, since a high angle thrust fault bounds the Bogda mountain range and the foreland basin. The deformation characteristics of this region have been dominated by vertical uplift, and the component of propagation toward the basin has been very limited. This tectonic deformation is evidenced as vertical growth. Although the deformation rate is small, the uplift amplitude is very significant in this region.

  17. Damping scaling factors for elastic response spectra for shallow crustal earthquakes in active tectonic regions: "average" horizontal component

    USGS Publications Warehouse

    Rezaeian, Sanaz; Bozorgnia, Yousef; Idriss, I.M.; Abrahamson, Norman; Campbell, Kenneth; Silva, Walter

    2014-01-01

    Ground motion prediction equations (GMPEs) for elastic response spectra are typically developed at a 5% viscous damping ratio. In reality, however, structural and nonstructural systems can have other damping ratios. This paper develops a new model for a damping scaling factor (DSF) that can be used to adjust the 5% damped spectral ordinates predicted by a GMPE for damping ratios between 0.5% to 30%. The model is developed based on empirical data from worldwide shallow crustal earthquakes in active tectonic regions. Dependencies of the DSF on potential predictor variables, such as the damping ratio, spectral period, ground motion duration, moment magnitude, source-to-site distance, and site conditions, are examined. The strong influence of duration is captured by the inclusion of both magnitude and distance in the DSF model. Site conditions show weak influence on the DSF. The proposed damping scaling model provides functional forms for the median and logarithmic standard deviation of DSF, and is developed for both RotD50 and GMRotI50 horizontal components. A follow-up paper develops a DSF model for vertical ground motion.

  18. Regional and global variations in the temporal clustering of tectonic tremor activity

    NASA Astrophysics Data System (ADS)

    Idehara, Koki; Yabe, Suguru; Ide, Satoshi

    2014-12-01

    The temporal distribution of tremor activity exhibits a highly non-Poissonian behavior, and its maximum period of non-Poissonian clustering statistically describes the recurrence interval of major tremor bursts. Here, we examine variations in the temporal clustering properties of tremor activity by assessing their characteristic times, which are determined by the maximum period of the non-Poissonian distribution. By applying a two-point correlation integral to some of the world's major tremor zones, including Shikoku, Kii-Tokai, and Kyushu in Japan; Cascadia, Jalisco, and Guerrero in Mexico; southern Chile; Taiwan; and Manawatu in New Zealand, we reveal local spatial variations in the temporal clustering properties in each tremor zone and show global-scale variations in tremor activity. The spatial variation in local tremor activity is characterized by a gradual transition in the along-dip direction and shorter-wavelength heterogeneities in the along-strike direction, possibly associated with a spatial change in frictional conditions at the plate interface and rheological conditions in the surrounding materials. The characteristic time correlates positively with locally measured median tremor duration, implying an inherent correlation between the moment release rate and the recurrence interval of tremors.

  19. Impact of wind erosion on detecting active tectonics from geomorphic indexes in extremely arid areas: a case study from the Hero Range, Qaidam Basin, NW China

    NASA Astrophysics Data System (ADS)

    Wu, Lei; Xiao, Ancheng; Yang, Shufeng

    2014-11-01

    Geomorphologic analysis has been used widely to detect active tectonics in regions where fluvial incision is the major erosional process. In this paper, however, we assess the feasibility of utilizing these frequently-used geomorphic indexes (e.g., hypsometric curves, longitudinal channel profiles, normalized stream length-gradient (SLK) index) to determine active tectonics in extremely arid areas where wind erosion also plays an important role. The case study is developed on the Hero Range in the western Qaidam Basin, one of the driest regions on Earth with severe wind erosion since late Pliocene. The result shows that in the west and south sectors, as well as the western part of the east sector, of the Hero Range where fluvial incision prevails, these geomorphic indexes are good indicators of active faulting and consistent with the geological result based on study of fault traces, scarps, faulted Holocene fans and historical seismicity within the past four decades. In contrast, along the northeastern margin (the NE and the SE parts of the east sector) of the range where wind erosion is also important, the results from the geomorphic indexes show quite active tectonics, contrary with the geological evidence favoring weakly active tectonics. Moreover, the positive SLK anomaly lies oblique to the fault trace and the anticline axis but parallel to the wind direction. To reconcile the contradiction, we propose that wind erosion caused by northwestern winds has a tendency to make geomorphic indexes exhibit anomalous values that indicate higher activities, by way of (1) lowering the base-level to generate knickpoints on the longitudinal channel profiles and therefore positive SLK anomalies, and (2) lateral erosion of the mountain front making the hypsometric curves and even the longitudinal channel profiles more convex, and producing obvious slope breaks.

  20. Slip sense inversion on active strike-slip faults in southwest Japan and its implications for Cenozoic tectonic evolution

    NASA Astrophysics Data System (ADS)

    Maruyama, Tadashi; Lin, Aiming

    2004-05-01

    Analyses of deflected river channels, offset of basement rocks, and fault rock structures reveal that slip sense inversion occurred on major active strike-slip faults in southwest Japan such as the Yamasaki and Mitoke fault zones and the Median Tectonic Line (MTL). Along the Yamasaki and Mitoke fault zones, small-size rivers cutting shallowly mountain slopes and Quaternary terraces have been deflected sinistrally, whereas large-size rivers which deeply incised into the Mio-Pliocene elevated peneplains show no systematically sinistral offset or complicated hairpin-shaped deflection. When the sinistral offsets accumulated on the small-size rivers are restored, the large-size rivers show residual dextral deflections. This dextral offset sense is consistent with that recorded in the pre-Cenozoic basement rocks. S-C fabrics of fault gouge and breccia zone developed in the active fault zones show sinistral shear sense compatible with earthquake focal mechanisms, whereas those of the foliated cataclasite indicate a dextral shear sense. These observations show that the sinistral strike-slip shear fabrics were overprinted on dextral ones which formed during a previous deformation phase. Similar topographic and geologic features are observed along the MTL in the central-eastern part of the Kii Peninsula. Based on these geomorphological and geological data, we infer that the slip sense inversion occurred in the period between the late Tertiary and mid-Quaternary period. This strike-slip inversion might result from the plate rearrangement consequent to the mid-Miocene Japan Sea opening event. This multidisciplinary study gives insight into how active strike-slip fault might evolves with time.

  1. Continental tectonics in the aftermath of plate tectonics

    NASA Technical Reports Server (NTRS)

    Molnar, Peter

    1988-01-01

    It is shown that the basic tenet of plate tectonics, rigid-body movements of large plates of lithosphere, fails to apply to continental interiors. There, buoyant continental crust can detach from the underlying mantle to form mountain ranges and broad zones of diffuse tectonic activity. The role of crustal blocks and of the detachment of crustal fragments in this process is discussed. Future areas of investigation are addressed.

  2. Tectonic and gravity-induced deformation along the active Talas-Fergana Fault, Tien Shan, Kyrgyzstan

    NASA Astrophysics Data System (ADS)

    Tibaldi, A.; Corazzato, C.; Rust, D.; Bonali, F. L.; Pasquarè Mariotto, F. A.; Korzhenkov, A. M.; Oppizzi, P.; Bonzanigo, L.

    2015-08-01

    This paper shows, by field palaeoseismological data, the Holocene activity of the central segment of the intracontinental Talas-Fergana Fault (TFF), and the relevance of possible future seismic shaking on slope stability around a large water reservoir. The fault, striking NW-SE, is marked by a continuous series of scarps, deflected streams and water divides, and prehistoric earthquakes that offset substrate and Holocene deposits. Fault movements are characterised by right-lateral strike-slip kinematics with a subordinate component of uplift of the NE block. Structural, geological and geomorphological field data indicate that shallow and deep landslides are aligned along the TFF, and some of them are active. Where the TFF runs close to the reservoir, the fault trace is obscured by a series of landslides, affecting rock and soil materials and ranging in size from small slope instabilities to deep-seated gravity-induced slope deformations (DGSDs). The largest of these, which does not show clear evidence of present-day activity, involves a volume of about 1 km3 and is associated with smaller but active landslides in its lower part, with volumes in the order of 2.5 × 104 m3 to 1 × 106 m3. Based on the spatial and temporal relations between landslides and faults, we argue that at least some of these slope failures may have a coseismic character. Stability analyses by means of limit equilibrium methods (LEMs), and stress-strain analysis by finite difference numerical modelling (FDM), were carried out to evaluate different hazard scenarios linked to these slope instabilities. The results indicate concern for the different threats posed, ranging from the possible disruption of the M-41 highway, the main transportation route in central Asia, to the possible collapse of huge rock masses into the reservoir, possibly generating a tsunami.

  3. Preliminary atlas of active shallow tectonic deformation in the Puget Lowland, Washington

    USGS Publications Warehouse

    Barnett, Elizabeth A.; Haugerud, Ralph A.; Sherrod, Brian L.; Weaver, Craig S.; Pratt, Thomas L.; Blakely, Richard J.

    2010-01-01

    This atlas presents an up-to-date map compilation of the geological and geophysical observations that underpin interpretations of active, surface-deforming faults in the Puget Lowland, Washington. Shallow lowland faults are mapped where observations of deformation from paleoseismic, seismic-reflection, and potential-field investigations converge. Together, results from these studies strengthen the identification and characterization of regional faults and show that as many as a dozen shallow faults have been active during the Holocene. The suite of maps presented in our atlas identifies sites that have evidence of deformation attributed to these shallow faults. For example, the paleoseismic-investigations map shows where coseismic surface rupture and deformation produced geomorphic scarps and deformed shorelines. Other maps compile results of seismic-reflection and potential-field studies that demonstrate evidence of deformation along suspected fault structures in the subsurface. Summary maps show the fault traces derived from, and draped over, the datasets presented in the preceding maps. Overall, the atlas provides map users with a visual overview of the observations and interpretations that support the existence of active, shallow faults beneath the densely populated Puget Lowland.

  4. Active tectonics in the Mygdonia basin (northern Greece): a combined seismological and remote-sensed geomorphology approach

    NASA Astrophysics Data System (ADS)

    Gkarlaouni, Charikleia; Andreani, Louis; Pennos, Chris; Gloaguen, Richard; Papadimitriou, Eleftheria; Kilias, Adamantios; Michail, Maria

    2014-05-01

    In Greek mainland, active extensional deformation resulted in the development of numerous seismogenic E- to SE-trending basins. The Mygdonia graben located in central Macedonia produced major historical earthquakes and poses a serious threat to the neighbouring city of Thessaloniki. Our aim is to determine which active seismic sources have the potential to generate strong events. Active tectonics shape the landscape, control the evolution of the fluvial network and cause the occurrence of strong and frequent earthquakes generated by fault populations. Thus, our approach combined both seismology and remote-sensed geomorphology. Seismological investigation and more especially relocation analysis was performed for recent seismicity in the area (2000-2012). Low magnitude earthquakes not exceeding 4.8 constitute the seismicity pattern for this period. Accurately determined focal parameters indicate that seismicity is not only localized along major fault zones. Smaller faults seem also to be activated. Temporal and spatial investigation show that seismicity is clustered and seismic bursts often migrate to adjacent faults. The hypocentral distribution of precisely determined microearthquake foci reveals the existence of high-angle (> 60º) normal faults dipping both south and north. This is consistent with fault plane solutions of stronger earthquakes. The largest amount of earthquakes is generated along the NW-SE sub-basin bounded from "Assiros-Analipsi" and "Lagina" fault zone, as well as in "Sochos" fault in the north which dips with approximately 70º-80º to the south. All these structures played an important role in the seismotectonic evolution of the area. We used geomorphic indices in order to analyse the landscapes of the Mygdonia region. Geomorphic indices were derived from DEM and computed using MATLAB scripts. We classified the landscapes according to their erosional stages using hypsometric integral and surface roughness. Both indices suggest stronger erosion

  5. Active Tectonics of off-Hokuriku, Central Japan, by two ships seismic reflection profiling

    NASA Astrophysics Data System (ADS)

    Kato, Naoko; Sato, Hiroshi; Ishiyama, Tatsuya; Abe, Susumu; Shiraishi, Kazuya

    2015-04-01

    Along the southern to eastern margin of the Sea of Japan, active faults are densely distributed. These submarine active faults produced tsunami disasters, such as 1983 Nihonkai-chubu earthquake (M7.7) and 1993 Hokkaido Nansei-oki earthquake (M7.8). To estimate tsunami hazards, we performed deep seismic reflection profiling to obtain the information of tsunami source faults, off-Hokuriku area in the central part of Honshu, Japan. The survey is carried out as a part of research project named "the integrated research project on seismic and tsunami hazards around the Sea of Japan" funded by MEXT. To obtain long offset data in busy marine activity area, we used two vessels; a gun-ship with 3020 cu. inch air-gun and a cable-ship with a 2-km-long, streamer cable with 156 channels and 480 cu. inch air-gun. Common-midpoint reflection data were acquired using two ships at 4 km offset. The survey area consists of stretched continental crust associated with rifting and opening of the Sea of Japan in early Miocene and is marked by densely distributed syn-rift normal faults. Fault reactivation of normal faults as reverse faults is common. Two phases of fault reactivation are identified from the seismic sections after termination of opening of the Sea of Japan. One is the late Miocene NS trending shortening deformation. This is produced by NS-trending convergence of the Shikoku basin (15 Ma), which belongs to the Philippine Sea plate (PHS) to SW Japan at Nankai trough (Kimura et al., 2005). After the initiation of the subduction of PHS at Nankai trough, the strong shortening deformation is terminated and the fold-and-thrust belt was unconformably covered by sub-horizontal Pliocene sediments. Some horizons of unconformities represent multiple events of shortening driven from the subduction interface. Some normal faults reactivated as active strike-slip and reverse faults in Quaternary. Well observed example is the 2007 Noto peninsula earthquake (M6.8). The 2007 Noto peninsula

  6. Cenozoic Tectonic Activity of the "Passive" North America Margin: Evidence for Cenozoic Activity on Mesozoic or Paleozoic Faults

    NASA Astrophysics Data System (ADS)

    Nedorub, O. I.; Knapp, C. C.

    2012-12-01

    The tectonic history of the Eastern North American Margin (ENAM) incorporates two cycles of continental assembly, multiple pulses of orogeny, rifting, and post-rift geodynamic evolution. This is reflected in the heterogeneous lithosphere of the ENAM which contains fault structures originated in Paleozoic to Mesozoic eras. The South Georgia Rift basin is probably the largest Mesozoic graben within its boundaries that is associated with the breakup of Pangea. It is composed of smaller sub-basins which appear to be bounded by high-angle normal faults, some of which may have been inverted in late Cretaceous and Cenozoic eras. Paleozoic structures may have been reactivated in Cenozoic time as well. The ENAM is characterized by N-NE maximum horizontal compressive stress direction. This maximum compressional stress field is sub-parallel to the strike of the Atlantic Coast province fault systems. Camden, Augusta, Allendale, and Pen Branch faults are four of the many such reactivated faults along the southern part of ENAM. These faults are now buried under the 0-400 m of loosely consolidated Cretaceous and Cenozoic age sediments and thus are either only partially mapped or currently not recognized. Some of the objectives of this study are to map the subsurface expression and geometry of these faults and to investigate the post Cretaceous deformation and possible causes of fault reactivation on a passive margin. This study employs an integrated geophysical approach to investigate the upper 200 m of identified locations of the above mentioned faults. 2-D high-resolution shallow seismic reflection and refraction methods, gravity surveys, GPR, 2-D electrical resistivity and well data are used for analyses and interpretation. Preliminary results suggest that Camden fault shows signs of Cenozoic reactivation through an approximately 30 m offset NW side up mainly along a steeply dipping fault zone in the basal contact of Coastal Plain sediments with the Carolina Piedmont. Drill

  7. Saturn's Titan: Surface change, ammonia, and implications for atmospheric and tectonic activity

    USGS Publications Warehouse

    Nelson, R.M.; Kamp, L.W.; Matson, D.L.; Irwin, P.G.J.; Baines, K.H.; Boryta, M.D.; Leader, F.E.; Jaumann, R.; Smythe, W.D.; Sotin, C.; Clark, R.N.; Cruikshank, D.P.; Drossart, P.; Pearl, J.C.; Hapke, B.W.; Lunine, J.; Combes, M.; Bellucci, G.; Bibring, J.-P.; Capaccioni, F.; Cerroni, P.; Coradini, A.; Formisano, V.; Filacchione, G.; Langevin, R.Y.; McCord, T.B.; Mennella, V.; Nicholson, P.D.; Sicardy, B.

    2009-01-01

    Titan is known to have a young surface. Here we present evidence from the Cassini Visual and Infrared Mapping Spectrometer that it is currently geologically active. We report that changes in the near-infrared reflectance of a 73,000 km2 area on Titan (latitude 26° S, longitude 78° W) occurred between July 2004 and March of 2006. The reflectance of the area increased by a factor of two between July 2004 and March–April 2005; it then returned to the July 2004 level by November 2005. By late December 2005 the reflectance had surged upward again, establishing a new maximum. Thereafter, it trended downward for the next three months. Detailed spectrophotometric analyses suggest these changes happen at or very near the surface. The spectral differences between the region and its surroundings rule out changes in the distribution of the ices of reasonably expected materials such as H2O, CO2, and CH4 as possible causes. Remarkably, the change is spectrally consistent with the deposition and removal of NH3 frost over a water ice substrate. NH3 has been proposed as a constituent of Titan's interior and has never been reported on the surface. The detection of NH3 frost on the surface might possibly be explained by episodic effusive events occur which bring juvenile ammonia from the interior to the surface. If so, its decomposition would feed nitrogen to the atmosphere now and in the future. The lateral extent of the region exceeds that of active areas on the Earth (Hawaii) or Io (Loki).

  8. Tectonics of the central Andes

    NASA Technical Reports Server (NTRS)

    Bloom, Arthur L.; Isacks, Bryan L.; Fielding, Eric J.; Fox, Andrew N.; Gubbels, Timothy L.

    1989-01-01

    Acquisition of nearly complete coverage of Thematic Mapper data for the central Andes between about 15 to 34 degrees S has stimulated a comprehensive and unprecedented study of the interaction of tectonics and climate in a young and actively developing major continental mountain belt. The current state of the synoptic mapping of key physiographic, tectonic, and climatic indicators of the dynamics of the mountain/climate system are briefly reviewed.

  9. Luminescence ages for alluvial-fan deposits in Southern Death Valley: Implications for climate-driven sedimentation along a tectonically active mountain front

    USGS Publications Warehouse

    Sohn, M.F.; Mahan, S.A.; Knott, J.R.; Bowman, D.D.

    2007-01-01

    Controversy exists over whether alluvial-fan sedimentation along tectonically active mountain fronts is driven by climatic changes or tectonics. Knowing the age of sedimentation is the key to understanding the relationship between sedimentation and its cause. Alluvial-fan deposits in Death Valley and throughout the arid southwestern United States have long been the subjects of study, but their ages have generally eluded researchers until recently. Most mapping efforts have recognized at least four major relative-age groupings (Q1 (oldest), Q2, Q3, and Q4 (youngest)), using observed changes in surface soils and morphology, relation to the drainage net, and development of desert pavement. Obtaining numerical age determinations for these morphologic stages has proven challenging. We report the first optically stimulated luminescence (OSL) ages for three of these four stages deposited within alluvial-fans along the tectonically active Black Mountains of Death Valley. Deposits showing distinct, remnant bar and swale topography (Q3b) have OSL ages from 7 to 4 ka., whereas those with moderate to poorly developed desert pavement and located farther above the active channel (Q3a) have OSL ages from 17 to 11 ka. Geomorphically older deposits with well-developed desert pavement (Q2d) have OSL ages ???25 ka. Using this OSL-based chronology, we note that alluvial-fan deposition along this tectonically active mountain front corresponds to both wet-to-dry and dry-to-wet climate changes recorded globally and regionally. These findings underscore the influence of climate change on alluvial fan deposition in arid and semi-arid regions. ?? 2007 Elsevier Ltd and INQUA.

  10. Regional Tectonic Framework and Human Activities on the North Central Part of The Mexican Volcanic Belt.

    NASA Astrophysics Data System (ADS)

    Nieto-Obregon, J.

    2001-12-01

    Faults and fractures northeasterly oriented dipping NW and SE, with slips mainly normal with a slight left lateral component, affect a suite of rocks of Mesozoic to Pleistocene age, in the area of El Bajio, in the states of Queretaro, Guanajuato, Michoacan, and Aguascalientes. The faults and fractures have affected the infrastructure of the cities and surroundings of Queretaro, Celaya, Salamanca, Irapuato, Silao, Leon and Aguascalientes. In the city of Queretaro, the Tlacote-Balvanera active fault has developed a scarp and its motion may potentially affect life lines of great importance. In Celaya City a N-S trending fault traverses the city and has produced a step wise scarp more than 1.80 m high, damaging houses, streets and life lines. In Salamanca, a fault trending N 60oE, dipping to the SE extends from Cerro Gordo to the SW traversing the city and affecting with a varying degree its infrastructure. Displacements observed within the urban area reach as much as 50 cm. Close to Irapuato City, in a quarry near La Valencianita village, a N 45oE trending fault dipping to the NW affects a lacustrine sequence bearing calcareous horizons. The fault exhibits a throw of 10 m and passes north of the urban area. A similarly oriented fault traverses the city of Irapuato, and near the Traffic Circle of Puente de Guadalupe, changes its strike to the SE and continues to the city limits. In the city of Silao, a fault oriented N 60oE, traverses the city and continues to the SW up to the localities of Venta de Ramales and La Aldea. Important displacements in urban and rural areas reach more than 60 cm. Outside the city of Leon in the junction of the highways to Aguascalientes and Guadalajara a normal fault plane NE oriented and dipping SE shows striations compatible with a normal left lateral motion. Faulting is associated with old buried scarps controlled by pre existing faults, and over exploited aquifers. Some of these faults however are considered potentially active based on

  11. Geological and tectonic implications obtained from first seismic activity investigation around Lembang fault

    NASA Astrophysics Data System (ADS)

    Afnimar; Yulianto, Eko; Rasmid

    2015-12-01

    The Lembang fault located at northern part of populated Bandung basin is the most conspicuous fault that potentially capable in generating earthquakes. The first seismic investigation around Lembang fault has been done by deploying a seismic network from May 2010 till December 2011 to estimate the seismic activities around that fault. Nine events were recorded and distributed around the fault. Seven events were likely to be generated by the Lembang fault and two events were not. The events related to the Lembang fault strongly suggest that this fault has left-lateral kinematic. It shows vector movement of Australian plate toward NNE might have been responsible for the Lembang fault kinematic following its initial vertical gravitational movement. The 1-D velocity model obtained from inversion indicates the stratigraphy configuration around the fault composed at least three layers of low Vp/Vs at the top, high Vp/Vs at the middle layer and moderate Vp/Vs at the bottom. In comparison with general geology of the area, top, mid and bottom layers may consecutively represent Quaternary volcanic layer, pre-Quaternary water-filled sedimentary layer and pre-Quaternary basement. Two eastern events related to minor faults and were caused by a gravitational collapse.

  12. Permian to late Cenozoic evolution of northern Patagonia: Main tectonic events, magmatic activity, and depositional trends

    NASA Astrophysics Data System (ADS)

    Uliana, M. A.; Biddle, K. T.

    The late Paleozoic to late Cenozoic evolution of northern Patagonia was influenced significantly by events that occurred while the area was part of the South American sector of Gondwanaland. Late Paleozoic to Middle Triassic subduction along the edge of the supercontinent formed a broad convergent-margin system that is the underpinning of northern Patagonia. Deformation (Gondwanidian orogeny) associated with the subduction is recognized in both the forearc and the convergent backarc areas. Regional extension, accompanied by bimodal volcanism, began in the Late Triassic and led to the formation of a number of north-northwest trending rift basins in Patagonia, which generally followed the Gondwanidian basement grain. Continued extension in the Jurassic and Early Cretaceous led to the opening of the Rocas Verdes marginal basin in southern Chile and, ultimately, to the opening of the South Atlantic Ocean. Once oceanic crust began to form, faulting and volcanism declined in Patagonia. During the late Early Cretaceous to the Late Cretaceous, sags over the rift basins coalesced to form a broad backarc basin behind the volcanic arc to the west. These sags are suggestive of thermally driven subsidence. Subsidence of the evolving Atlantic margin allowed extensive marine transgressions to take place from the east. The stratigraphic record of northern Patagonia reflects these events. The upper Paleozoic to upper Mesozoic sedimentary sequences were deposited in basins directly associated with convergent activity along the margin of Gondwanaland or in rift basins created during its breakup. Even though the Tertiary evolution of Patagonia was dominated by events along the western margin of South America, the patterns of sediment transport, thickness, and general shoreline position were still influenced by the locations of the Mesozoic rifts formed during the breakup of Gondwanaland.

  13. Active tectonics of the Seattle fault and central Puget sound, Washington - Implications for earthquake hazards

    USGS Publications Warehouse

    Johnson, S.Y.; Dadisman, S.V.; Childs, J. R.; Stanley, W.D.

    1999-01-01

    We use an extensive network of marine high-resolution and conventional industry seismic-reflection data to constrain the location, shallow structure, and displacement rates of the Seattle fault zone and crosscutting high-angle faults in the Puget Lowland of western Washington. Analysis of seismic profiles extending 50 km across the Puget Lowland from Lake Washington to Hood Canal indicates that the west-trending Seattle fault comprises a broad (4-6 km) zone of three or more south-dipping reverse faults. Quaternary sediment has been folded and faulted along all faults in the zone but is clearly most pronounced along fault A, the northernmost fault, which forms the boundary between the Seattle uplift and Seattle basin. Analysis of growth strata deposited across fault A indicate minimum Quaternary slip rates of about 0.6 mm/yr. Slip rates across the entire zone are estimated to be 0.7-1.1 mm/yr. The Seattle fault is cut into two main segments by an active, north-trending, high-angle, strike-slip fault zone with cumulative dextral displacement of about 2.4 km. Faults in this zone truncate and warp reflections in Tertiary and Quaternary strata and locally coincide with bathymetric lineaments. Cumulative slip rates on these faults may exceed 0.2 mm/yr. Assuming no other crosscutting faults, this north-trending fault zone divides the Seattle fault into 30-40-km-long western and eastern segments. Although this geometry could limit the area ruptured in some Seattle fault earthquakes, a large event ca. A.D. 900 appears to have involved both segments. Regional seismic-hazard assessments must (1) incorporate new information on fault length, geometry, and displacement rates on the Seattle fault, and (2) consider the hazard presented by the previously unrecognized, north-trending fault zone.

  14. Active tectonics and rheology of slow-moving thrusts in the Tibetan foreland of peninsular India

    NASA Astrophysics Data System (ADS)

    Copley, Alex; Mitra, Supriyo; Sloan, Alastair; Gaonkar, Sharad; Avouac, Jean-Philippe; Hollingsworth, James

    2016-04-01

    Peninsular India is cut by active thrust faults that break in earthquakes in response to the compressive force exerted between India and the Tibetan Plateau. The rate of deformation is low, with 2 +/- 1 mm/yr of shortening being accommodated over the entire N-S extent of the Indian sub-continent. However, the large seismogenic thickness in the region (40-50 km), and the long faults, mean that the rare earthquakes that do occur can have magnitudes up to at least 8. This contribution describes studies of two large Indian earthquakes, and their rheological and hazard implications, using a range of techniques. First, the Mw 7.6 Bhuj (Gujarat) earthquake of 2001 is examined using a combination of seismology, InSAR, and levelling data. A slip model for the earthquake will be presented, which allows the material properties of the fault plane to be examined. Second, a Holocene-age earthquake rupture from central India will be discussed. Geomorphic analysis of the scarps produced by the event suggest a magnitude of 7.6 - 8.4. Both of these earthquakes had unusually large stress-drops, amongst the largest recorded for shallow earthquakes. The information provided by these two events will be combined with calculations for the total compressive force being transmitted through the Indian peninsular in order to suggest that the faults are characterised by a low coefficient of friction (approximately 0.1), and that the stress-drops in the earthquakes are close to complete. In turn, these results imply that the majority of the force being transmitted through the Indian plate is supported by the brittle crust. Finally, the along-strike continuation of the faults will be described, with implications for hazard assessment and material properties throughout India.

  15. Petrogenesis and geodynamic setting of Early Cretaceous mafic-ultramafic intrusions, South China: A case study from the Gan-Hang tectonic belt

    NASA Astrophysics Data System (ADS)

    Qi, Youqiang; Hu, Ruizhong; Liu, Shen; Coulson, Ian M.; Qi, Huawen; Tian, Jianji; Zhu, Jingjing

    2016-08-01

    A study using whole-rock major-trace elements and Sr-Nd isotopes as well as zircon U-Pb dating has been carried out on Early Cretaceous mafic-ultramafic intrusions from the Gan-Hang tectonic belt (GHTB), South China, to understand the origin of mantle sources and the sequential evolution of the underlying Late Mesozoic lithospheric mantle of this area. The study focused on two intrusions, one at Quzhou and the other at Longyou (see Fig. 1). They are primarily composed of mafic-ultramafic rocks with wide range of chemical compositions. The Quzhou mafic rocks have relatively narrow ranges of SiO2 (48.94-51.79 wt%), MgO (6.07-7.21 wt%), Fe2O3 (10.48-11.56 wt%), CaO (8.20-8.81 wt%), and Mg# (51.7-56.5) with relatively low K2O (0.56-0.67 wt%) and Na2O (3.09-3.42 wt%). By contrast, the ultramafic rocks from Longyou have distinct lower SiO2 (41.50-45.11 wt%) and higher MgO (9.05-9.90 wt%), Fe2O3 (12.14-12.62 wt%), CaO (8.64-10.67 wt%), and Mg# (59.5-61.1) with relatively higher K2O (1.32-1.75 wt%) and Na2O (4.53-5.08 wt%). They are characterized by Ocean Island Basalts (OIB)-type trace element distribution patterns, with a significant enrichment of light rare earth elements (LREE), large ion lithophile elements (LILE, i.e., Rb, Ba, K, and Sr) and high field strength elements (HFSE, i.e., Nb, Ta), and slight depletion of Th, U, Ti, and Y. The intrusions exhibit relatively depleted Sr-Nd isotope compositions, with (87Sr/86Sr)i range of 0.7035 to 0.7055 (143Nd/144Nd)i of 0.51264 to 0.51281 and εNd(t) values of + 3.0 to + 6.6. Zircon U-Pb dating of Longyou and Quzhou intrusions yields consistent magma emplacement ages of 129.0 ± 3.9 to 126.2 ± 2.4 Ma, respectively. The dating results are consistent with the peak of extension in Early Cretacerous throughout the Gan-Hang tectonic belt. Their magmas were principally derived from near-solidus partial melting of pyroxenites with different content of silica, and the pyroxenites were resulted from a juvenile SCLM peridotite

  16. Edaphics, active tectonics and animal movements in the Kenyan Rift - implications for early human evolution and dispersal

    NASA Astrophysics Data System (ADS)

    Kübler, Simon; Owenga, Peter; Rucina, Stephen; King, Geoffrey C. P.

    2014-05-01

    The quality of soils (edaphics) and the associated vegetation strongly controls the health of grazing animals. Until now, this has hardly been appreciated by paleo-anthropologists who only take into account the availability of water and vegetation in landscape reconstruction attempts. A lack of understanding the importance of the edaphics of a region greatly limits interpretations of the relation between our ancestors and animals over the last few million years. If a region lacks vital trace elements then wild grazing and browsing animals will avoid it and go to considerable length and take major risks to seek out better pasture. As a consequence animals must move around the landscape at different times of the year. In complex landscapes, such as tectonically active rifts, hominins can use advanced group behaviour to gain strategic advantage for hunting. Our study in the southern Kenya rift in the Lake Magadi region shows that the edaphics and active rift structures play a key role in present day animal movements as well as the for the location of an early hominin site at Mt. Olorgesailie. We carried out field analysis based on studying the relationship between the geology and soil development as well as the tectonic geomorphology to identify 'good' and 'bad' regions both in terms of edaphics and accessibility for grazing animals. We further sampled different soils that developed on the volcanic bedrock and sediment sources of the region and interviewed the local Maasai shepherds to learn about present-day good and bad grazing sites. At the Olorgesailie site the rift valley floor is covered with flood trachytes; basalts only occur at Mt. Olorgesailie and farther east up the rift flank. The hominin site is located in lacustrine sediments at the southern edge of a playa that extends north and northwest of Mt. Olorgesailie. The lakebeds are now tilted and eroded by motion on two north-south striking faults. The lake was trapped by basalt flows from Mt. Olorgesailie

  17. Active tectonics, paleoseismology and associated methodological challenges posed by the slow moving Alhama de Murcia fault (SE Iberia)

    NASA Astrophysics Data System (ADS)

    Ferrater, Marta; Ortuño, Maria; Masana, Eulàlia; Pallàs, Raimon; Perea, Hector; Baize, Stephane; García-Meléndez, Eduardo; Martínez-Díaz, José J.; Echeverria, Anna; Rockwell, Thomas; Sharp, Warren D.; Arrowsmith, Ramon; Medialdea, Alicia; Rhodes, Edward

    2016-04-01

    The Alhama de Murcia fault (AMF) is a 87 km-long left-lateral slow moving fault and is responsible for the 5.1 Mw 2011 Lorca earthquake. The characterization of the seismic potential of seismogenic strike-slip slow moving faults is necessary but raises huge methodological challenges, as most paleoseismological and active tectonic techniques have been designed on and for fast moving faults. The AMF is used here as a pilot study area to adapt the traditional geomorphological and trenching analyses, especially concerning the precise quantification of offset channels. We: 1) adapted methodologies to slow moving faults, 2) obtained, for the first time, the slip rate of the AMF, and 3) updated its recurrence period and maximum expected magnitude. Morphotectonic studies aim to use the measured tectonic offset of surface channels to calculate seismic parameters. However, these studies lack a standard criterion to score the analysed features. We improved this by differentiating between subjective and objective qualities, and determining up to three objective parameters (lithological changes, associated morphotectonics and shape, and three shape sub-parameters; all ranging from 0 to 1). By applying this methodology to the AMF, we identified and characterized 138 offset features that we mapped on a high-resolution (0.5 × 0.5 m pixel size) Digital Elevation Model (DEM) from a point cloud acquired in 2013 by airborne light detection and ranging (lidar). The identified offsets, together with the ongoing datings, are going to be used to calculate the lateral slip rate of the AMF. In three-dimensional trenches, we measured the offsets of a buried channel by projecting the far-field tendency of the channel onto the fault. This procedure is inspired by the widespread geomorphological procedure and aims to avoid the diffuse deformation in the fault zone associated with slow moving faults. The calculation of the 3D tendency of the channel and its projection onto the fault permitted

  18. Evidence of active tectonics on a Roman aqueduct system (II-III century A.D.) near Rome, Italy

    NASA Astrophysics Data System (ADS)

    Marra, Fabrizio; Montone, Paola; Pirro, Mario; Boschi, Enzo

    2004-04-01

    In this paper we describe evidence of strong tectonic deformation affecting two aqueducts of Roman age (II-III century A.D.). The channels are located approximately 20 km northeast of Rome along the ancient Via Tiburtina. Brittle and ductile deformation affects these two structures, including extensional joint systems, NE-oriented faults, and horizontal distortion. This deformation is consistent with right-lateral movement on major N-striking faults, and represents the first evidence that tectonic deformation took place in historical times in the vicinity of Rome, with local strike-slip movement superimposed on a regional extensional fault system.

  19. Normal faulting along the western side of the Matese Mountains: Implications for active tectonics in the Central Apennines (Italy)

    NASA Astrophysics Data System (ADS)

    Boncio, Paolo; Dichiarante, Anna Maria; Auciello, Eugenio; Saroli, Michele; Stoppa, Francesco

    2016-01-01

    We provide new field data from geologic mapping and bedrock structural geology along the western side of the Matese Mts in central Italy, a region of high seismicity, strain rates among the highest of the entire Apennines (4-5 mm/yr GPS-determined extension), and poorly constrained active faults. The existing knowledge on the Aquae Iuliae normal fault (AIF) was implemented with geometric and kinematic data that better constrain its total length (16.5 km), the minimum long-term throw rate (0.3-0.4 mm/yr, post-late glacial maximum, LGM), and the segmentation. For the first time, we provide evidence of post-350 ka and possibly late Quaternary activity of the Ailano - Piedimonte Matese normal fault (APMF). The APMF is 18 km long. It is composed of a main 11 km-long segment striking NW-SE and progressively bending to the E-W in its southern part, and a 7 km-long segment striking E-W to ENE-WSW with very poor evidence of recent activity. The available data suggest a possible post-LGM throw rate of the main segment of ≳0.15 mm/yr. There is no evidence of active linkage in the step-over zone between the AIF and APMF (Prata Sannita step-over). An original tectonic model is proposed by comparing structural and geodetic data. The AIF and APMF belong to two major, nearly parallel fault systems. One system runs at the core of the Matese Mts and is formed by the AIF and the faults of the Gallo-Letino-Matese Lake system. The other system runs along the western side of the Matese Mts and is formed by the APMF, linked to the SE with the Piedimonte Matese - Gioia Sannitica fault. The finite extension of the APMF might be transferred to the NW towards the San Pietro Infine fault. The nearly 2-3 mm/yr GPS-determined extension rate is probably partitioned between the two systems, with a ratio that is difficult to establish due to poor GPS coverage. The proposed model, though incomplete (several faults/transfer zones need further investigations), aids in the seismotectonic

  20. Detrital zircon U-Pb geochronology, Lu-Hf isotopes and REE geochemistry constrains on the provenance and tectonic setting of Indochina Block in the Paleozoic

    NASA Astrophysics Data System (ADS)

    Wang, Ce; Liang, Xinquan; Foster, David A.; Fu, Jiangang; Jiang, Ying; Dong, Chaoge; Zhou, Yun; Wen, Shunv; Van Quynh, Phan

    2016-05-01

    In situ U-Pb geochronology, Lu-Hf isotopes and REE geochemical analyses of detrital zircons from Cambrian-Devonian sandstones in the Truong Son Belt, central Vietnam, are used to provide the information of provenance and tectonic evolution of the Indochina Block. The combined detrital zircon age spectra of all of the samples ranges from 3699 Ma to 443 Ma and shows with dominant age peaks at ca. 445 Ma and 964 Ma, along with a number of age populations at 618-532 Ma, 1160-1076 Ma, 1454 Ma, 1728 Ma and 2516 Ma. The zircon age populations are similar to those from time equivalent sedimentary sequences in continental blocks disintegrated from the East Gondwana during the Phanerozoic. The younger zircon grains with age peaks at ca. 445 Ma were apparently derived from middle Ordovician-Silurian igneous and metamorphic rocks in Indochina. Zircons with ages older than about 600 Ma were derived from other Gondwana terrains or recycled from the Precambrian basement of the Indochina Block. Similarities in the detrital zircon U-Pb ages suggest that Paleozoic strata in the Indochina, Yangtze, Cathaysia and Tethyan Himalayas has similar provenance. This is consistent with other geological constrains indicating that the Indochina Block was located close to Tethyan Himalaya, northern margin of the India, and northwestern Australia in Gondwana.

  1. Geochemistry, Sr-Nd isotope composition, and tectonic setting of Holocene Pelado, Guespalapa and Chichinautzin scoria cones, south of Mexico City

    NASA Astrophysics Data System (ADS)

    Siebe, Claus; Rodríguez-Lara, Virgilio; Schaaf, Peter; Abrams, Michael

    2004-02-01

    Holocene Pelado, Guespalapa and Chichinautzin monogenetic scoria cones and associated lava flows located within the Sierra del Chichinautzin Volcanic Field (SCVF) at the southern margin of Mexico City were mapped and sampled for mineralogical and chemical analyses. With the exception of Parı´cutin volcano in western Mexico, few scoria cones in the Trans-Mexican Volcanic Belt have ever been sampled in greater detail. Chemical analyses of rocks indicate that mafic products (e.g. Guespalapa and Chichinautzin) from individual volcanoes in the Sierra del Chichinautzin are characterized by substantial chemical variability, whereas high-silica andesite volcanoes (e.g. Pelado) are very uniform in composition. These findings have important bearings for regional tephrochronology. As a whole, rock compositions form a continuous coherent calc-alkaline suite, explicable by polybaric fractional crystallization±assimilation associated with successive stagnation at different depths along the ascent path. Trace element and Sr-Nd isotope analyses point toward a <1-km-scale heterogeneous (enriched/depleted) mantle wedge underneath the SCVF. The recently proposed plume-origin for these rocks is not in accord with our data. Instead, magma origin is discussed in relation to the tectonically complex subduction process of the oceanic Cocos Plate underneath the continental North American Plate.

  2. Global Tectonics on Ganymede

    NASA Technical Reports Server (NTRS)

    Thomas, P. G.; Forni, O. P.; Masson, P. L.

    1985-01-01

    Three large basin surroundings on Ganymede located on grooved terrains, which are supposed to be intensely tectonized areas were studied. All rectilinear morphological elements such as ridges, block edges; and parts of scarps were mapped. The geometric properties (grid pattern) characteristics were determined and a history for the formation of the Ganymede basins studied is proposed. Results indicate that the grooved terrains are very surficial layers, and that their formation does not significantly affect, disturb or rotate the basement. This is in agreement with the conclusion obtained from completely different data (crosscutting relationships between groove sets and their basements).

  3. Active faulting Vs other surface displacing complex geomorphic phenomena. Case studies from a tectonically active area, Abruzzi Region, central Apennines, Italy

    NASA Astrophysics Data System (ADS)

    Lo Sardo, Lorenzo; Gori, Stefano; Falcucci, Emanuela; Saroli, Michele; Moro, Marco; Galadini, Fabrizio; Lancia, Michele; Fubelli, Giandomenico; Pezzo, Giuseppe

    2016-04-01

    How can be univocally inferred the genesis of a linear surface scarp as the result of an active and capable fault (FAC) in tectonically active regions? Or, conversely, how it is possible to exclude that a scarp is the result of a capable fault activation? Trying to unravel this open questions, we show two ambiguous case studies about the problem of the identification of active and capable faults in a tectonically active area just based on the presence of supposed fault scarps at surface. The selected cases are located in the area comprised between the Middle Aterno Valley Fault (MAVF) and the Campo Imperatore Plain (Abruzzi Region, central Apennines), nearby the epicentral area of the April 6th, 2009 L'Aquila earthquake. In particular, the two case studies analysed are located in a region characterized by a widespread Quaternary faults and by several linear scarps: the case studies of (i) Prata D'Ansidonia area and (ii) Santo Stefano di Sessanio area. To assess the origin and the state of activity of the investigated geomorphic features, we applied a classical geological and geomorphological approach, based on the analysis of the available literature, the interpretation of the aerial photographs, field surveying and classical paleoseismological approach, the latter consisting in digging excavations across the analysed scarps. These analysis were then integrated by morphometrical analyses. As for case (i), we focused on determining the geomorphic "meaning" of linear scarps carved onto fluvial-deltaic conglomerates (dated to the Early Pleistocene; Bertini and Bosi, 1993), up to 3 meters high and up to 1,5 km long, that border a narrow, elongated and flat-bottom depressions, filled by colluvial deposits. These features groove the paleo-landsurface of Valle Daria (Bosi and Bertini, 1970), wide landsurface located between Barisciano and Prata D'Ansidonia. Entwining paleoseismological trenching with geophysical analyses (GPR, ERT and microgravimetrical prospections), it

  4. Deep reaching versus vertically restricted Quaternary normal faults: Implications on seismic potential assessment in tectonically active regions: Lessons from the middle Aterno valley fault system, central Italy

    NASA Astrophysics Data System (ADS)

    Falcucci, E.; Gori, S.; Moro, M.; Fubelli, G.; Saroli, M.; Chiarabba, C.; Galadini, F.

    2015-05-01

    We investigate the Middle Aterno Valley fault system (MAVF), a poorly investigated seismic gap in the central Apennines, adjacent to the 2009 L'Aquila earthquake epicentral area. Geological and paleoseismological analyses revealed that the MAVF evolved through hanging wall splay nucleation, its main segment moving at 0.23-0.34 mm/year since the Middle Pleistocene; the penultimate activation event occurred between 5388-5310 B.C. and 1934-1744 B.C., the last event after 2036-1768 B.C. and just before 1st-2nd century AD. These data define hard linkage (sensu Walsh and Watterson, 1991; Peacock et al., 2000; Walsh et al., 2003, and references therein) with the contiguous Subequana Valley fault segment, able to rupture in large magnitude earthquakes (up to 6.8), that did not rupture since about two millennia. By the joint analysis of geological observations and seismological data acquired during to the 2009 seismic sequence, we derive a picture of the complex structural framework of the area comprised between the MAVF, the Paganica fault (the 2009 earthquake causative fault) and the Gran Sasso Range. This sector is affected by a dense array of few-km long, closely and regularly spaced Quaternary normal fault strands, that are considered as branches of the MAVF northern segment. Our analysis reveals that these structures are downdip confined by a decollement represented by to the presently inactive thrust sheet above the Gran Sasso front limiting their seismogenic potential. Our study highlights the advantage of combining Quaternary geological field analysis with high resolution seismological data to fully unravel the structural setting of regions where subsequent tectonic phases took place and where structural interference plays a key role in influencing the seismotectonic context; this has also inevitably implications for accurately assessing seismic hazard of such structurally complex regions.

  5. Timing, petrogenesis and tectonic setting of the Late Paleozoic gabbro-granodiorite-granite intrusions in the Shalazhashan of northern Alxa: Constraints on the southernmost boundary of the Central Asian Orogenic Belt

    NASA Astrophysics Data System (ADS)

    Shi, Xingjun; Wang, Tao; Zhang, Lei; Castro, Antonio; Xiao, XuChang; Tong, Ying; Zhang, Jianjun; Guo, Lei; Yang, Qidi

    2014-11-01

    The Late Paleozoic tectonic setting and location of the southernmost boundary of the Central Asian Orogenic Belt (CAOB) with respect to the Alxa Block or Alxa-North China Craton (ANCC) are debated. This paper presents new geochronological, petrological, geochemical and zircon Hf isotopic data of the Late Paleozoic intrusions from the Shalazhashan in northern Alxa and discusses the tectonic setting and boundary between the CAOB and ANCC. Using zircon U-Pb dating, intrusions can be broadly grouped as Late Carboniferous granodiorites (~ 301 Ma), Middle Permian gabbros (~ 264 Ma) and granites (~ 266 Ma) and Late Permian granodiorites, monzogranites and quartz monzodiorites (254-250 Ma). The Late Carboniferous granodiorites are slightly peraluminous and calcic. The remarkably high zircon Hf isotopes (εHf(t) = + 6-+ 10) and characteristics of high silica adakites suggest that these granodiorites were mainly derived from "hot" basaltic slab-melts of the subducted oceanic crust. The Middle Permian gabbros exhibited typical cumulate textures and were derived from the partial melting of depleted mantle. The Middle Permian granites are slightly peraluminous with high-K calc-alkaline and low εHf(t) values from - 0.9 to + 2.9. These granites were most likely derived from juvenile materials mixed with old crustal materials. The Late Permian granodiorites, monzogranites and quartz monzodiorites are characterized as metaluminous to slightly peraluminous, with variable Peacock alkali-lime index values from calc-alkalic to alkali-calcic. These rocks were mainly derived from juvenile crustal materials, as evidenced by their high εHf(t) values (+ 3.3 to + 8.9). The juvenile sources of the above intrusions in the Shalazhashan are similar to those of the granitoids from the CAOB but distinct from the granitoids within the Alxa Block. These findings suggest that the Shalazhashan Zone belongs to the CAOB rather than the Alxa Block and that its boundary with the Alxa block can be

  6. Geochemistry of the Neoproterozoic metasediments of Malhaq and Um Zariq formations, Kid metamorphic complex, Sinai, Egypt: Implications for source-area weathering, provenance, recycling, and depositional tectonic setting

    NASA Astrophysics Data System (ADS)

    El-Bialy, Mohammed Zaky

    2013-08-01

    The Um Zariq and Malhaq formations occupy roughly the northern half of the Kid metamorphic complex of SE Sinai, in the NE part of the Arabian-Nubian Shield. The Um Zariq Formation metasediments are relicts of an old sedimentary sequence (Cryogenian; 813 ± 6 Ma), whereas the Malhaq Formation records several phases of Ediacaran sedimentation and volcanic activity (615-607 Ma). The Um Zariq Formation is mainly represented by well-bedded metapelitic schists, while the Malhaq Formation comprises a series of structureless to schistose felsic to intermediate metavolcanics interbedded with mica-rich phyllites and schists. The Um Zariq metasediments are depleted in SiO2, CaO and K2O and enriched in TiO2, Al2O3 and K2O relative to those of the Malhaq Formation. Aside from the relatively low Ni and Cr concentrations, compatible transition elements of these metasediments are comparable to average crustal contents. Except for marked Sr depletion, LILEs are around average continental crust values. Pronounced negative Nb-Ta anomalies and enrichment of Um Zariq samples in Th, U, Zr, Ti and Y relative to Malhaq ones are the main features of HFSEs. The REE patterns of all samples are parallel to sub-parallel LREE-enriched, with distinct negative Eu anomalies and weakly fractionated HREE segments. The source rocks of the Malhaq Formation metasediments underwent mild to moderate chemical weathering, whereas those of the Um Zariq Formation have suffered severe chemical weathering. These metasediments are predominately derived from felsic to intermediate igneous sources, with a particular slight addition from recycled sedimentary source to the Malhaq Formation metasediments. They are collectively geochemically immature and have suffered minor sedimentary recycling, with the experience of the Malhaq Formation metasediments from higher degree of sorting and reworking. The Malhaq and Um Zariq metasediments were originally deposited in a continental arc setting, most probably back

  7. Ulkan-Dzhugdzhur ore-bearing anorthosite-rapakivi granite-peralkaline granite association, Siberian Craton: Age, tectonic setting, sources, and metallogeny

    NASA Astrophysics Data System (ADS)

    Larin, A. M.

    2014-07-01

    The paper systematizes and integrates the results of geological, isotopic geochronological, and geochemical studies of the igneous rocks that make up the Ulkan-Dzhugdzhur anorthosite-rapakivi granite-peralkaline granite association and related mineralization. This association is a typical example of anorogenic igneous rocks that formed in the within-plate geodynamic setting most likely under effect of the mantle superplume, which was active in the territory of the Siberian Craton 1.75-1.70 Ga ago. The igneous rock association formed in a discrete regime that reflected the pulsatory evolution of a sublithospheric mantle source. The prerift (1736-1727 Ma) and rift proper (1722-1705 Ma) stages and a number of substages are distinguished. All igneous rocks pertaining to this association have mixed mantle-crustal origin. Basic rocks crystallized from the OIB-type basaltic magma, which underwent crustal contamination at various depths. Felsic rocks are products of mantle and crustal magma mixing. The contribution of mantle component progressively increased in a time-dependent sequence: moderately alkaline subsolvus granite → moderately alkaline and alkaline hypersolvus granites → peralkaline hypersolvus granite. All endogenic deposits in the studied district are related to a single source represented by the mantle plume and its derivatives. The Fe-Ti-apatite deposits hosted in anorthosite formed as a result of intense lower crustal contamination of basaltic magma near the Moho discontinuity and two stages of fractional crystallization at lower and upper crustal depth levels. The rare-metal deposits are genetically related to peralkaline granite. Formation of uranium deposits was most likely caused by Middle Riphean rejuvenation of the region, which also involved rocks of the Ulkan-Dzhugdzhur association.

  8. Influence of Tectonic Setting on Geochemical Characteristics of Post-orogenic Pegmatites: an Example from the Mojave Pegmatite District, Northern Arizona

    NASA Astrophysics Data System (ADS)

    Hanson, S. L.; Simmons, W. B.; Falster, A.; Brown, T.

    2011-12-01

    The Mojave pegmatite district, located in northwestern Arizona, lies near the eastern margin of the Mojave terrane, a fragment of predominantly crustal material that docked with Laurentia during the Yavapai orogeny. The pegmatite district is host to numerous post-orogenic pegmatites that were emplaced subsequent to the Yavapai (1.71-1.68 Ga), and Mazatzal (1.65-1.60 Ga) orogenies. They range from simple, meter wide dikes to complexly zoned sill-like bodies. Five of the larger pegmatites include the Kingman (KM) pegmatite exposed in the southeastern Cerbat Range and the Rare Metals (RM) and three Wagon Bow (WB) pegmatites 65 km to the east in the Aquarius Range. The ~1.56 KM pegmatite is intrusive into orogenic granodiorite whereas the circa 1.44 RM and WB pegmatites occur as segregations in dike-like bodies that are intrusive into granitic host rocks. The pegmatites are zoned with composite quartz-microcline cores, are rare-earth-element (REE) enriched, and depleted in HFSE and F. The KM pegmatite exhibits an extreme LREE enrichment reflected in the unusually large abundance of allanite-(Ce) and allanite-(Nd) which occurs as pods of crudely formed crystals up to 0.5 m in length. The WB # 3 pegmatite contains only small quantities of REE bearing minerals including xenotime and monazite whereas RM has accessory allanite-(Ce), monazite-(Ce), bastnaesite, aeschynite-(Y), euxenite-(Y), and polycrase-(Y). These characteristics are generally atypical for anorogenic pegmatites, which contain higher and more equal abundances of both LREE- and HREE-bearing minerals. Genetically related host granites for the WB pegmatites are metaluminous to weakly peraluminous, have high K2O (4.95 - 5.65 wt%) and high FeO/(FeO+MgO) ratios (0.82-0.85). Spider diagrams show general enrichments in the more incompatible elements with deep troughs for Sr, Ba, P, and Ti and peaks for Rb, Th, Ce, Hf, Zr and Y. On tectonic discrimination diagrams, the host granites lie predominantly in the within

  9. Active tectonic data calling for the re-evaluation of the seismic hazard along the Vienna Basin Transform Fault

    NASA Astrophysics Data System (ADS)

    Decker, K.; Hinsch, R.; Peresson, H.; Wagreich, M.

    2003-04-01

    The Vienna Basin Transform Fault is a slow moving active fault passing through the most populated and most productive region of Austria with 2.4 million inhabitants producing c. 45% of the Austrian GDP. Active faulting in this highly vulnerable environment is accompanied by historically moderate seismicity (Imax ~ 8-9) in a narrow NE-striking zone paralleling the fault. Novel tectonic data such as maps of active faults and computed seismic slip deficits indicate that previous hazard analyses for the surrounding of Vienna may both underestimate the probability of severe earthquakes and the maximum credible earthquake. Slip rates of the fault in the Vienna Basin are derived from an actively subsiding pull-apart structure filled with up to 140 m Quaternary sediments. 1.5 to 2 km sinistral displacement, which accumulated during basin formation in the last 400 (?) ky corresponds to a slip rate of 1.6 - 2.5 mm/y. This is in good agreement with GPS data showing 2 mm slip per year and precise leveling proving surface subsidence up to 1 mm/y. The data, however, strongly contrast from slip rates computed from cumulative seismic moments of earthquakes. Seismic energy release only accounts for c. 0.2 mm/yr slip proving a seismic slip deficit for the historical time window of about 750 y. In addition, seismic slip calculations for arbitrarily selected fault sectors reveal large differences between the fastest (0.5 mm/yr) and slowest (0.02 mm/yr) seismically moving sector. We relate these to the locking of fault segments. Both results indicate that the seismic cycle exceeds the length of available seismological observation and larger earthquakes than those recorded need to be expected along the fault. Additional data to call for hazard re-evaluation come from the integration of subcrop data, Quaternary thickness, earthquake data, geophysical data (Gegenleitner et al., this vol.) and geomorphology, which results in a detailed map of active faults. The map depicts a major NE

  10. Compositions of micas in peraluminous granitoids of the eastern Arabian shield - Implications for petrogenesis and tectonic setting of highly evolved, rare-metal enriched granites

    USGS Publications Warehouse

    du Bray, E.A.

    1994-01-01

    Compositions and pleochroism of micas in fourteen peraluminous alkali-feldspar granites in the eastern part of the Late Proterozoic Arabian Shield are unlike those of micas (principally biotite) in most calc-alkaline granitoid rocks. Compositions of these micas are distinguished by elevated abundances of Li2O, F, and numerous cations and by low MgO abundances. These micas, constituents of highly evolved rare-metal enriched granitoids, represent an iron-lithium substitution series that ranges from lithium-poor siderophyllite to lithium-rich ferroan lepidolite. The eastern Arabian Shield also hosts six epizonal granitoids that contain colorless micas. Compositions of these micas, mostly muscovite, and their host granitoids are distinct from those of the iron-lithium micas and their host granitoids. Compositions of the analyzed micas have a number of petrogenetic implications. The twenty granitoids containing these micas form three compositional groups that reflect genesis in particular tectonic regimes; mica compositions define the same three groups. The presence of magmatic muscovite in six of these shallowly crystallized granitoids conflicts with experimental data indicating muscovite stability at pressures greater than 3 kbar. Muscovite in the Arabian granitoids probably results from its non-ideal composition; the presence of muscovite cannot be used as a pressure indicator. Finally, mineral/matrix partition coefficients are significantly greater than 1.0 for a number of cations, the rare-earth elements in particular, in many of the analyzed iron-lithium micas. Involvement of these types of micas in partial melting or fractionation processes can have a major influence on silicate liquid compositions. ?? 1994 Springer-Verlag.

  11. Can deep seated gravitational slope deformations be activated by regional tectonic strain: First insights from displacement measurements in caves from the Eastern Alps

    NASA Astrophysics Data System (ADS)

    Baroň, Ivo; Plan, Lukas; Grasemann, Bernhard; Mitroviċ, Ivanka; Lenhardt, Wolfgang; Hausmann, Helmut; Stemberk, Josef

    2016-04-01

    Tectonic elastic strain and ground deformations are documented as the most remarkable environmental phenomena occurring prior to local earthquakes in tectonically active areas. The question arises if such strain would be able to trigger mass movements. We discuss a directly observed fault slip and a subsequent minor activation of a deep-seated gravitational slope deformation prior to the M = 3 Bad Fischau earthquake between end of November and early December 2013 in NE Austria. The data originate from two faults in the Emmerberg and Eisenstein Caves in the transition zone between the Eastern Alps and the Vienna Basin, monitored in the framework of the FWF "Speleotect" project. The fault slips have been observed at the micrometer-level by means of an opto-mechanical 3D crack gauge TM-71. The discussed event started with the fault activation in the Emmerberg Cave on 25 November 2013 recorded by measurements of about 2 μm shortening and 1 μm sinistral parallel slip, which was fully in agreement with the macroscopically documented past fault kinematics. One day later, the mass (micro) movement activated on the opposite side of the mountain ridge in the Eisenstein Cave and it continued on three consecutive days. Further, the fault in the Emmerberg Cave experienced also a subsequent gravitational relaxation on 2/3 December 2013, when the joint opened and the southern block subsided towards the valley, while the original sinistral displacement remained irreversible. The process was followed by the M = 3 earthquake in Bad Fischau on 11 December 2013. Our data suggest that tectonic strain could play a higher role on the activation of slow mass movements in the area than expected. Although we cannot fully exclude the co-activation of the mass movement in the Eisenstein Cave by water saturation, the presented data bring new insight into recent geodynamics of the Eastern Alps and the Vienna Basin. For better interpretations and conclusions however, we need a much longer

  12. Active strike-slip faulting history inferred from offsets of topographic features and basement rocks: a case study of the Arima Takatsuki Tectonic Line, southwest Japan

    NASA Astrophysics Data System (ADS)

    Maruyama, Tadashi; Lin, Aiming

    2002-01-01

    Geological, geomorphological and geophysical data have been used to determine the total displacement, slip rates and age of formation of the Arima-Takatsuki Tectonic Line (ATTL) in southwest Japan. The ATTL is an ENE-WSW-trending dextral strike-slip fault zone that extends for about 60 km from northwest of the Rokko Mountains to southwest of the Kyoto Basin. The ATTL marks a distinct topographic boundary between mountainous regions and basin regions. Tectonic landforms typically associated with active strike-slip faults, such as systematically-deflected stream channels, offset ridges and fault scarps, are recognized along the ATTL. The Quaternary drainage system shows progressive displacement along the fault traces: the greater the magnitude of stream channel, the larger the amount of offset. The maximum dextral deflection of stream channels is 600-700 m. The field data and detailed topographic analyses, however, show that pre-Neogene basement rocks on both sides of the ATTL are displaced by about 16-18 km dextrally and pre-Mio-Pliocene elevated peneplains are also offset 16-17 km in dextral along the ATTL. This suggests that the ATTL formed in the period between the development of the pre-Mio-Pliocene peneplains and deflection of the Quaternary stream channels. The geological, geomorphological and geophysical evidence presented in this study indicates that (1) the ATTL formed after the mid-Miocene, (2) the ATTL has moved as a dextral strike-slip fault with minor vertical component since its formation to late Holocene and (3) the ATTL is presently active with dextral slip rates of 1-3 mm/year and a vertical component of >0.3 mm/year. The formation of the ATTL was probably related to the opening of the Japan Sea, which is the dominant tectonic event around Japan since mid-Miocene. The case study of the ATTL provides insight into understanding the tectonic history and relationship between tectonic landforms and structures in active strike-slip faults.

  13. The Ross Orogen and Lachlan Fold Belt in Marie Byrd Land, Northern Victoria Land and New Zealand: implication for the tectonic setting of the Lachlan Fold Belt in Antarctica

    USGS Publications Warehouse

    Bradshaw, J.D.

    2007-01-01

    Correlation of the Cambrian Delamerian Orogen of Australia and Ross Orogen of the Transantarctic Mountains widely accepted but the extension of the adjacent Lachlan Orogen into Antarctica is controversial. Outside the main Ross-Delamerian belt, evidence of this orogeny is preserved at Mt Murphy in Marie Byrd Land and the in Takaka Terrane of New Zealand. In all pre-break- configurations of the SW Pacific, these two areas are far removed from the Ross-Delamerian belt. Evidence from conglomerates in the Takaka Terrane, however, shows that in Late Cambrian times it was adjacent to the Ross Orogen. This indicates major tectonic displacements within Gondwana after the Cambrian and before break-up. The Lachlan Orogen formed in an extensional belt in a supra-subduction zone setting and the Cambrian rocks of Marie Byrd Land and New Zealand are interpreted as parts of a rifted continental ribbon on the outboard side of the Lachlan belt.

  14. Travertine-Depositing Cool-Springs of the Rio Grande Rift, New Mexico: Links Between Geochemistry, Tectonic Setting, and Microbial Diversity

    NASA Astrophysics Data System (ADS)

    Newell, D. L.; Crossey, L. J.; Dahm, C. N.; Takacs-Vesbach, C.

    2005-12-01

    Travertine-depositing cool springs found within the Rio Grande rift in New Mexico may represent the distal discharges of deep hydrothermal systems related to continental rifting. We hypothesize that these springs represent overlooked ecological niches that host chemolithotrophic microorganisms relying on spring chemistry for metabolism. The geochemistry of these springs is in many ways similar to seafloor and continental hot springs, such as Yellowstone, where thermophilic microbes representing the deepest branches of the universal phylogenetic tree are found. We analyzed cool springs that varied in water type from Ca-Mg-HCO3 to Na-Cl and Na-SO4 waters and ranged from dilute to high (23,000 ppm) in total dissolved solids. Carbon dioxide comprised up to 99% of the water-free spring gases. Hydrogen was present up to tenths of percent, equating to 7-3400 nM dissolved H2. Methane and hydrogen sulfide were detected in some springs up to 0.1 and 4%, respectively. Oxygen was deficient to absent. 3 He4He ratios ranged from 0.1 to 0.6 RA (relative to air), equating to 1-7% mantle-derived helium. The δ13CO2 of spring gases ranged from -4.6 to -1.0 permil PDB, overlapping the mantle and marine limestone ranges. Mixing models using carbon and helium isotopes suggest that at least 5% of the CO2 was mantle derived. We hypothesize that the source of high H2 levels was mantle-derived magmatism. The lack of oxygen, abundance of hydrogen and carbon (dissolved CO2), and high concentrations of aqueous species such as sulfate have created an environment suitable for chemolithotrophic microbes. The presence of methane and hydrogen sulfide suggest that methanogenic and sulfate reducing microbes are active. Microbial community analysis using PCR-DGGE will test for microbial diversity and identify potential trends in metabolism related to spring geochemistry. The apparent link between mantle-derived gases and deeply-circulated fluids in a continental rift setting with the presence of

  15. Tectonic setting of the Jurassic bimodal magmatism in the Sakarya Zone (Central and Western Pontides), Northern Turkey: A geochemical and isotopic approach

    NASA Astrophysics Data System (ADS)

    Genç, Ş. Can; Tüysüz, Okan

    2010-07-01

    The Lower to Middle Jurassic Mudurnu formation of the Sakarya Zone (Northern Turkey) was deposited in an extensional basin. This unit crops out along the southern Pontide range and consists of marine sedimentary rocks including debris flows, lignite-bearing clastic rocks and Ammonitico Rosso horizons alternating with mafic and felsic volcanic and volcaniclastic rocks. Magmatic rocks of the Mudurnu formation comprise two compositionally different groups; 1) a mafic group including diabase-microgabbro-basaltic lavas and their pyroclastic equivalents, and 2) a felsic group including granite porphyries and felsic pyroclastic rocks. All the magmatic members of the Mudurnu formation are subalkaline and display a calc-alkaline affinity. They are bimodal, with a significant silica gap between the mafic and felsic members with the exception of a few samples. These magmatic rocks display enrichment in LILE and depletion in Nb, Ta, P and Ti, implying a subduction-related magmatic signature. Melting modelling for the mafic rocks indicates that they originated possibly from subcontinental lithospheric mantle (SCLM) composed of spinel lherzolite. ɛNd(i) values (+ 1.5 to + 4.3) imply that the mafic volcanic and hypabyssal rocks were possibly derived from a time-integrated LREE-depleted mantle source. The initial Sr and Nd isotope values, and ɛNd(i) of the felsic hypabyssal rocks are comparable to the mafic ones. The isotope data point to a genetic relationship between the felsic and mafic members. Results obtained from the geochemical modelling of incompatible versus compatible trace elements show that the felsic rocks were derived from the mafic melts by fractional crystallization (FC) process. In the light of their regional geological setting and these geochemical characteristics, we propose that the magmatic rocks of the Mudurnu formation formed in an extensional basin situated on an active and/or just ended subduction zone during the Jurassic period. The Mudurnu formation

  16. Geochemistry of the Neoproterozoic metasediments of Malhaq and Um Zariq formations, Kid Metamorphic Complex, Sinai, Egypt: implications for source-area weathering, provenance, recycling, and depositional tectonic setting

    NASA Astrophysics Data System (ADS)

    El-Bialy, Mohammed Z.

    2013-04-01

    The Kid Metamorphic Complex of SE Sinai represents a thick volcano-sedimentary succession that underwent polyphase deformation and greenschist to upper amphibolite facies metamorphism in the NE part of the Arabian-Nubian Shield (ANS). The Malhaq and Um Zariq Formations, the target of this study, occupy roughly the northern half of this complex. The Malhaq Formation records several phases of Ediacaran sedimentation and volcanic activity (615-607 Ma), whereas Um Zariq Formation metasediments are relicts of an older sedimentary sequence (Cryogenian; 813±6 Ma). The Malhaq Formation comprises a series of dark gray structureless to schistose felsic to intermediate metavolcanics interbedded and intercalated with fine- to medium-grained foliated mica-rich phyllites and schists, while the Um Zariq Formation is a dominantly metasedimentary sequence, mainly represented by well-bedded metapelitic schists. Malhaq metasediments are enriched in SiO2, CaO and K2O and depleted in TiO2, Al2O3 and K2O relative to those of Um Zariq Formation. Aside from the relatively low Ni and Cr concentrations, compatible transition elements of these metasediments are comparable to average crustal contents. Except for marked Sr depletion, LILEs are around average continental crust values. Pronounced negative Nb-Ta anomalies in all samples, and general enrichment of Um Zariq samples in Th, U, Zr, Ti and Y relative to Malhaq ones are the main features of HFSEs. The REE patterns of all samples are parallel to sub-parallel LREE-enriched, with distinct negative Eu anomalies and weakly fractionated HREE segments. Geochemical investigations have revealed that the source rocks of Malhaq Formation metasediments underwent mild to moderate chemical weathering, whereas those of Um Zariq Formation have suffered severe chemical weathering. These metasediments are predominately derived from felsic to intermediate igneous sources, with a particular slight addition from recycled sedimentary source to the Malhaq

  17. Implications for the tectonic transition zone of active orogeny in Hoping drainage basin, by landscape evolution at the multi-temporal timescale

    NASA Astrophysics Data System (ADS)

    Chang, Q.; Chen, R. F.; Lin, W.; Hsieh, P. S.

    2015-12-01

    In an actively orogeny the landscape are transient state of disequilibrium in response to climatic and tectonic inputs. At the catchment scale, sensitivity of river systems plays an important role in landscape evolution. Hoping drainage basin is located at the tectonic transition zone in the north-eastern Taiwan, where the behavior of Philippine Sea plate switches from overriding above the east-dipping Eurasian Continental plate to northward subducting under the Ryukyu arc. However, extensive deep-seated landslides, debris flow, and numerous large alluvial terraces can be observed, suggesting strong surface processes in this watershed. This effect on regional climate fundamentally changed the landscape by reconfiguring drainage patterns and creating a vast influx of sediments into the basin. In this study we review the morphological evidence from multi-temporal timescale, including in-situ cosmogenic nuclides denudation rate and suspension load data, coupled with the analysis of the longitudinal profiles. The main goal of this study is to compare Holocene erosion rates with thermochronology and radiometric dating of river terraces to investigate the erosion history of Hoping area. The result shows that short-term erosion rate is around twice as large as the long-term denudation rate, which might due to the climate-driven erosion events such as typhoon-induced landslide. We've also mapped detail morphological features by using the high-resolution LiDAR image, which help us to identify not only the landslide but also tectonic features such as lineation, fault scarps, and fracture zones. The tectonic surface features and field investigation results show that the drainage basin is highly fractured, suggesting that even though the vertical tectonic activity rate is small, the horizontal shortening influenced by both southward opening of the back-arc Okinawa trough and the north-western collision in this area is significant. This might cause the reducing in rock strength

  18. Seismicity at Uturuncu Volcano, Bolivia: Volcano-Tectonic Earthquake Swarms Triggered by the 2010 Maule, Chile Earthquake and Non-Triggered Background Activity

    NASA Astrophysics Data System (ADS)

    Christensen, D. H.; Chartrand, Z. A.; Jay, J.; Pritchard, M. E.; West, M. E.; McNutt, S. R.

    2010-12-01

    We find that the 270 ky dormant Uturuncu Volcano in SW Bolivia exhibits relatively high rates of shallow, volcano-tectonic seismicity that is dominated by swarm-like activity. We also document that the 27 February 2010 Mw 8.8 Maule, Chile earthquake triggered an exceptionally high rate of seismicity in the seconds to days following the main event. Although dormant, Uturuncu is currently being studied due to its large-scale deformation rate of 1-2 cm/yr uplift as revealed by InSAR. As part of the NASA-funded Andivolc project to investigate seismicity of volcanoes in the central Andes, a seismic network of 15 stations (9 Mark Products L22 short period and 6 Guralp CMG40T intermediate period sensors) with an average spacing of about 10 km was installed at Uturuncu from April 2009 to April 2010. Volcano-tectonic earthquakes occur at an average rate of about 3-4 per day, and swarms of 5-60 events within a span of minutes to hours occur a few times per month. Most of these earthquakes are located close to the summit at depths near and above sea level. The largest swarm occurred on 28 September 2009 and consisted of 60 locatable events over a time span of 28 hours. The locations of volcano-tectonic earthquakes at Uturuncu are oriented in a NW-SE trend, which matches the dominant orientation of regional faults and suggests a relationship between the fault system at Uturuncu and the regional tectonics of the area; a NW-SE trending fault beneath Uturuncu may serve to localize stresses that are accumulating over the broad area of uplift. Based on automated locations, the maximum local magnitude of these events is approximately M = 4 and the average magnitude is approximately M = 2. An initial estimate of the b-value is about b = 1.2. The Mw 8.8 Maule earthquake on 27 February 2010 triggered hundreds of local volcano-tectonic events at Uturuncu. High-pass filtering of the long period surface waves reveals that the first triggered events occurred with the onset of the Rayleigh

  19. Professional Development Settings: More than Time, Place, Activity

    ERIC Educational Resources Information Center

    Rosemary, Catherine A.; Feldman, Naomi

    2009-01-01

    Like authors who create settings as integral components of engaging narratives, thoughtful literacy coaches and other educators who plan and implement professional development consider elements of settings to engage teachers in continuous learning. Many teacher educators, researchers, administrators, literacy coaches, and K-12 teachers understand…

  20. Hydrothermal activity on the southern Mid-Atlantic Ridge: Tectonically- and volcanically-controlled venting at 4 5°S

    NASA Astrophysics Data System (ADS)

    German, C. R.; Bennett, S. A.; Connelly, D. P.; Evans, A. J.; Murton, B. J.; Parson, L. M.; Prien, R. D.; Ramirez-Llodra, E.; Jakuba, M.; Shank, T. M.; Yoerger, D. R.; Baker, E. T.; Walker, S. L.; Nakamura, K.

    2008-09-01

    We report results from an investigation of the geologic processes controlling hydrothermal activity along the previously-unstudied southern Mid-Atlantic Ridge (3-7°S). Our study employed the NOC (UK) deep-tow sidescan sonar instrument, TOBI, in concert with the WHOI (USA) autonomous underwater vehicle, ABE, to collect information concerning hydrothermal plume distributions in the water column co-registered with geologic investigations of the underlying seafloor. Two areas of high-temperature hydrothermal venting were identified. The first was situated in a non-transform discontinuity (NTD) between two adjacent second-order ridge-segments near 4°02'S, distant from any neovolcanic activity. This geologic setting is very similar to that of the ultramafic-hosted and tectonically-controlled Rainbow vent-site on the northern Mid-Atlantic Ridge. The second site was located at 4°48'S at the axial-summit centre of a second-order ridge-segment. There, high-temperature venting is hosted in an ˜ 18 km 2 area of young lava flows which in some cases are observed to have flowed over and engulfed pre-existing chemosynthetic vent-fauna. In both appearance and extent, these lava flows are directly reminiscent of those emplaced in Winter 2005-06 at the East Pacific Rise, 9°50'N and reference to global seismic catalogues reveals that a swarm of large (M 4.6-5.6) seismic events was centred on the 5°S segment over a ˜ 24 h period in late June 2002, perhaps indicating the precise timing of this volcanic eruptive episode. Temperature measurements at one of the vents found directly adjacent to the fresh lava flows at 5°S MAR (Turtle Pits) have subsequently revealed vent-fluids that are actively phase separating under conditions very close to the Critical Point for seawater, at ˜ 3000 m depth and 407 °C: the hottest vent-fluids yet reported from anywhere along the global ridge crest.

  1. The effect of a rainfall and discharge variability on erosion rates in a highly active tectonic setting: a stochastic approach

    NASA Astrophysics Data System (ADS)

    Braun, Jean; Deal, Eric; Andermann, Christoff

    2015-04-01

    The influence of climate on surface processes and consequently on landscape evolution is undeniably important; despite this, many fluvial landscape evolution models do not integrate an accurate or physically based parameterisation of precipitation, the climatic forcing most important for fluvial processes. This is likely due to two major challenges; first of all there is the difficulty in moving from the hourly, daily and monthly timescales most relevant to precipitation to the millennial timescales used in landscape evolution modelling. To confront this challenge, we adopt the approach of Tucker and Bras, 2000 and Lague, 2005, and upscale precipitation with a statistical parameterisation accounting for mean precipitation as well as short term (daily) variability. This technique is key in capturing and quantifying the importance of rare, extreme events. The second challenge stems from the fact that erosion rates are proportional not to precipitation, but rather to discharge, which results from a complex convolution of the regional precipitation patterns with the landscape. To address this second obstacle we present work that investigates the relationship between a stochastic description of precipitation and one of discharge, linking general patterns of precipitation and discharge rather than attempting to establish a deterministic relationship. To achieve this we model the effect of precipitation variability on runoff variability as well as compare associated precipitation and discharge measurements from a range of climatic regimes and spatial scales in the Himalayas. Using the results of this work, we integrate the statistical parameterisation of precipitation into a landscape evolution model, allowing us to explore the effect of realistic precipitation patterns, specifically precipitation variability, on the evolution of relief and topography. References Bras, R. L., & Tucker, G. E. (2000). A stochastic approach to modeling the role of rainfall variability in drainage basin evolution. Water Resources Research, 36(7), 1953-1964. doi:10.1029/2000WR900065 Lague, D. (2005). Discharge, discharge variability, and the bedrock channel profile. Journal of Geophysical Research, 110(F4), F04006. doi:10.1029/2004JF000259

  2. Age and tectonic setting of subsurface plutonic rocks in south Alabama: Implications for igneous activity along the Alleghanian suture

    SciTech Connect

    Guthrie, G.M. ); Steltenpohl, M.G. . Dept. of Geology); Heatherington, A.L. . Dept. of Geology); Kunk, M.J. ); Defant, M.S. . Dept. of Geology); Salpas, P.A. )

    1994-03-01

    The proposed Alleghanian suture between ancestral North America and Suwannee terrane Gondwana crust trends east-west beneath coastal plain sediments from South Carolina to Alabama. Three distinct intrusive suites in south Alabama have been examined to determine their possible relationships with the suture. The first suite consists of rhyolite, andesite, andesitic breccia, and granodiorite and forms the stratigraphic base of the Suwannee terrane. Calc-alkaline metaluminous granodiorite yields a whole-rock depleted mantle Nd model age of 1,023 Ma, a U-Pb zircon crystallization age of 625 Ma, and a [sup 40]Ar/[sup 39]Ar cooling age (ca. 500 C) of ca. 612 Ma. The second suite comprises felsic granophyre, pyroxenite, and diabase. Metaluminous granophyre follows a calc-alkaline trend with pyroxenite. Trace element ratios (Ta/Yb and Rb/Yb+Ta) indicate a volcanic or syn-collisional arc environment. Biotite separates from granodiorite yield a [sup 40]Ar/[sup 39]Ar cooling age (ca. 300 C) of ca. 329 Ma. Pyroxenite and granophyre Nd model ages are 1,062 and 1,090 Ma, respectively. The third suite comprises high-iron quartz-normative tholeiitic diabase, gabbro, and basalt. These rocks have Ta/Yb and Rb/Yb+Ta ratios similar to within plate magmas, and are correlated with the Lower Jurassic North American diabase suite because of geochemical similarities and intrusive contacts with the Upper Triassic-Lower Jurassic Newark Group.

  3. Active Ways to Teach Health Concepts in the Elementary Setting

    ERIC Educational Resources Information Center

    Gregory, Julie

    2015-01-01

    This article provides three movement-based activities for teaching health concepts to elementary school students. Two activities focus on nutrition concepts and the other focuses on teaching body systems. Diagrams are provided to show the setup of activities, as well as links for accessing materials to help implement the activities.

  4. Active tectonics west of New Zealand's Alpine Fault: South Westland Fault Zone activity shows Australian Plate instability

    NASA Astrophysics Data System (ADS)

    De Pascale, Gregory P.; Chandler-Yates, Nicholas; Dela Pena, Federico; Wilson, Pam; May, Elijah; Twiss, Amber; Cheng, Che

    2016-04-01

    The 300 km long South Westland Fault Zone (SWFZ) is within the footwall of the Central Alpine Fault (<20 km away) and has 3500 m of dip-slip displacement, but it has been unknown if the fault is active. Here the first evidence for SWFZ thrust faulting in the "stable" Australian Plate is shown with cumulative dip-slip displacements up to 5.9 m (with 3 m throw) on Pleistocene and Holocene sediments and gentle hanging wall anticlinal folding. Cone penetration test (CPT) stratigraphy shows repeated sequences within the fault scarp (consistent with thrusting). Optically stimulated luminescence (OSL) dating constrains the most recent rupture post-12.1 ± 1.7 ka with evidence for three to four events during earthquakes of at least Mw 6.8. This study shows significant deformation is accommodated on poorly characterized Australian Plate structures northwest of the Alpine Fault and demonstrates that major active and seismogenic structures remain uncharacterized in densely forested regions on Earth.

  5. Quarternary tectonics, Task 1

    SciTech Connect

    Bell, J.W.

    1993-09-30

    Activities conducted for the evaluation of the geology and seismotectonics stability of Yucca Mountain as a potential site for the underground disposal of high-level radioactive wastes continued. Tasks concerned with quaternary tectonics include: scheduling of photography of Little Skull Mountain area; the collection and dating of rock varnish samples from the 1932 Cedar Mountain earthquake area for carbon 14 AMS and cation-ratio analysis; collection of samples for thermoluminescence dating from the 1932 Cedar Mountain earthquake area; mapping of the northern area of Crater Flat; and surveying of the May 17, 1993 Eureka the Valley earthquake area.

  6. Tectonic activity as a significant source of crustal tetrafluoromethane emissions to the atmosphere: Observations in groundwaters along the San Andreas Fault

    NASA Astrophysics Data System (ADS)

    Deeds, Daniel A.; Kulongoski, Justin T.; Mühle, Jens; Weiss, Ray F.

    2015-02-01

    Tetrafluoromethane (CF4) concentrations were measured in 14 groundwater samples from the Cuyama Valley, Mil Potrero and Cuddy Valley aquifers along the Big Bend section of the San Andreas Fault System (SAFS) in California to assess whether tectonic activity in this region is a significant source of crustal CF4 to the atmosphere. Dissolved CF4 concentrations in all groundwater samples but one were elevated with respect to estimated recharge concentrations including entrainment of excess air during recharge (Cre; ∼30 fmol kg-1 H2O), indicating subsurface addition of CF4 to these groundwaters. Groundwaters in the Cuyama Valley contain small CF4 excesses (0.1-9 times Cre), which may be attributed to an in situ release from weathering and a minor addition of deep crustal CF4 introduced to the shallow groundwater through nearby faults. CF4 excesses in groundwaters within 200 m of the SAFS are larger (10-980 times Cre) and indicate the presence of a deep crustal flux of CF4 that is likely associated with the physical alteration of silicate minerals in the shear zone of the SAFS. Extrapolating CF4 flux rates observed in this study to the full extent of the SAFS (1300 km × 20-100 km) suggests that the SAFS potentially emits (0.3- 1) ×10-1 kg CF4 yr-1 to the Earth's surface. For comparison, the chemical weathering of ∼ 7.5 ×104km2 of granitic rock in California is estimated to release (0.019- 3.2) ×10-1 kg CF4 yr-1. Tectonic activity is likely an important, and potentially the dominant, driver of natural emissions of CF4 to the atmosphere. Variations in preindustrial atmospheric CF4 as observed in paleo-archives such as ice cores may therefore represent changes in both continental weathering and tectonic activity, including changes driven by variations in continental ice cover during glacial-interglacial transitions.

  7. GPS Monitoring of Ionospheric TEC Over the Area of Thessaliniki in Order to Detect Disturbances Related to the Local Tectonic Activity

    NASA Astrophysics Data System (ADS)

    Contadakis, M. E.; Arambelos, D.; Asteriadis, G.; Pikridas, Ch.; Spatalas, S.

    2004-04-01

    Atmospheric and underground explosions as well as shallow earthquakes producing strong vertical ground displacement, are known to produce pressure waves (e.g. Calais and Minster 1995) that propagates at infrasonic speeds in the atmosphere. At ionospheric altitudes these waves are coupled to ionospheric gravity waves and induce variations in the ionospheric electron density. On the other hand local lithospheric density variations, produced by the local tectonic activity during the earthquake preparation period, affect the local gravity field and consequently the overlying atmospheric and ionospheric density. This fact is reflected in the presence of exalting on atmospheric tide parameters (e.g. Arabelos et al. 2003, Contadakis et al. 2004) and on LF radio signals (Biagi et al. 2003). That is the lithospheric near surface tectonic activity results in local pre-, co- and post-seismic disturbances on the ionospheric Total Electronic Content. There for a program for the monitoring of TEC over the area of Thessaloniki in relation with the local seismic activity was initiated, using the data of the GPS permanent station of the Department of Surveying and Geodesy, University of Thessaloniki. In this paper the organizing of the observations and the method of analysis are presented and the first results of the observed ionospheric TEC variations in relation with the weak local seismic activity are being discussed.

  8. Tectonics, magmatism and fluid flow in a transtensional strike-slip setting: The northern termination of the dextral strike-slip Liquiñe-Ofqui Fault System, Chile

    NASA Astrophysics Data System (ADS)

    Perez Flores, P.; Sanchez, P.; Sielfeld, G.; Cembrano, J. M.

    2013-05-01

    One fundamental problem in continental margin tectonics is the nature of the interplay between tectonics and magma/fluid transport through the lithosphere. Deformation-driven fault-fracture networks have been regarded as efficient pathways through which magma and/or hydrothermal fluids are transported, stored and eventually connected to the earth surface. Thus, the state of stress of the lithosphere at the time of fluid transport should somehow control the first and second-order spatial distribution of dikes swarms, volcanic centers and geothermal reservoirs. We conducted a detailed structural mapping of the geometry, kinematics and relative timing of first and second-order fault systems and their spatially associated fault-vein networks at regional and local scales at the northern termination of the Liquiñe-Ofqui Fault System (LOFS). This is characterized by a transtensional imbricate fan (horsetail structure). Stratovolcanoes, minor eruptive centers, and hydrothermal vein systems are spatially and temporally associated with NNE master and ENE subsidiary faults of the LOFS and with NW-striking long-lived basement faults. The overprinted geothermal system is documented by NNE and ENE striking calcite-quartz hybrid and extensional vein systems, which appear to be associated with dextral strike-slip displacement on the LOFS. Fault-vein and vein microstructure varies from mineral fibers indicative of creeping faults to typical ridge-and-groove striae. Bladed calcite occurs in dilational jogs along the main LOFS master faults; they are interpreted to represent boiling episodes. Thicker and more pervasive NW sinistral-reverse fault-vein systems and breccias bodies suggest that the fault-valve mechanism was active during fluid transport and mineral precipitation. In some sites the NW-striking system cuts and displaces the active LOFS, suggesting that their active has extended to at least the Pleistocene.

  9. Project ACE Activity Sets. Book I: Grades 3, 4, and 5.

    ERIC Educational Resources Information Center

    Eden City Schools, NC.

    Eleven activity sets suitable for supplementing social studies units in grades 3, 4, and 5 are presented. Each set lists appropriate resources, concepts, general objectives and instructional objectives for each activity within the set. Grade 3 sets are "You Can Help Conserve Our Natural Resources,""Urban Decay and Urban Renewal,""The Use of…

  10. Investigating Cenozoic climate change in tectonically active regions with a high-resolution atmospheric general circulation model (ECHAM5)

    NASA Astrophysics Data System (ADS)

    Mutz, Sebastian; Ehlers, Todd; Li, Jingmin; Werner, Martin; Stepanek, Christian; Lohmann, Gerrit

    2016-04-01

    Studies of Cenozoic palaeo-climates contribute to our understanding of contemporary climate change by providing insight into analogues such as the Pliocene (PLIO), and by evaluation of GCM (General Circulation Models) performance using the Mid-Holocene (MH) and the Last Glacial Maximum (LGM). Furthermore, climate is a factor to be considered in the evolution of ecology, landscapes and mountains, and in the reconstruction of erosion histories. In this study, we use high-resolution (T159) ECHAM5 simulations to investigate pre-industrial (PI) and the the above mentioned palaeo-climates for four tectonically active regions: Alaska (St. Elias Range), the US Northwest Pacific (Cascade Range), western South America (Andes) and parts of Asia (Himalaya-Tibet). The PI climate simulation is an AMIP (Atmospheric Model Intercomparison Project) style ECHAM5 experiment, whereas MH and LGM simulation are based on simulations conducted at the Alfred Wegner Institute, Bremerhaven. Sea surface boundary conditions for MH were taken from coupled atmosphere-ocean model simulations (Wei and Lohmann, 2012; Zhang et al, 2013) and sea surface temperatures and sea ice concentration for the LGM are based on GLAMAP project reconstructions (Schäfer-Neth and Paul, 2003). Boundary conditions for the PLIO simulation are taken from the PRISM (Pliocene Research, Interpretation and Synoptic Mapping) project and the employed PLIO vegetation boundary condition is created by means of the transfer procedure for the PRISM vegetation reconstruction to the JSBACH plant functional types as described by Stepanek and Lohmann (2012). For each of the investigated areas and time slices, the regional simulated climates are described by means of cluster analyses based on the variability of precipitation, 2m air temperature and the intra-annual amplitude of the values. Results indicate the largest differences to a PI climate are observed for LGM and PLIO climates in the form of widespread cooling and warming

  11. 40 CFR 35.3535 - Authorized set-aside activities.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... ASSISTANCE STATE AND LOCAL ASSISTANCE Drinking Water State Revolving Funds § 35.3535 Authorized set-aside... DWSRF program and to provide technical assistance to public water systems. (c) Small systems technical... PWSS program; (ii) To administer or provide technical assistance through source water...

  12. 40 CFR 35.3535 - Authorized set-aside activities.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... ASSISTANCE STATE AND LOCAL ASSISTANCE Drinking Water State Revolving Funds § 35.3535 Authorized set-aside... DWSRF program and to provide technical assistance to public water systems. (c) Small systems technical... PWSS program; (ii) To administer or provide technical assistance through source water...

  13. 40 CFR 35.3535 - Authorized set-aside activities.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... ASSISTANCE STATE AND LOCAL ASSISTANCE Drinking Water State Revolving Funds § 35.3535 Authorized set-aside... DWSRF program and to provide technical assistance to public water systems. (c) Small systems technical... PWSS program; (ii) To administer or provide technical assistance through source water...

  14. 40 CFR 35.3535 - Authorized set-aside activities.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... ASSISTANCE STATE AND LOCAL ASSISTANCE Drinking Water State Revolving Funds § 35.3535 Authorized set-aside... DWSRF program and to provide technical assistance to public water systems. (c) Small systems technical... PWSS program; (ii) To administer or provide technical assistance through source water...

  15. 40 CFR 35.3535 - Authorized set-aside activities.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... ASSISTANCE STATE AND LOCAL ASSISTANCE Drinking Water State Revolving Funds § 35.3535 Authorized set-aside... DWSRF program and to provide technical assistance to public water systems. (c) Small systems technical... PWSS program; (ii) To administer or provide technical assistance through source water...

  16. Stars and Planets: A New Set of Middle School Activities

    NASA Technical Reports Server (NTRS)

    Urquhart, M. L.

    2002-01-01

    A set of lesson plans for grades 6-8 which deal with the sizes and distances of stars and planets using a scale factor of 1 to 10 billion, the life cycle of stars, and the search for planets beyond the solar system. Additional information is contained in the original extended abstract.

  17. Preliminary results on the tectonic activity of the Ovacık Fault (Malatya-Ovacık Fault Zone, Turkey): Implications of the morphometric analyses

    NASA Astrophysics Data System (ADS)

    Yazıcı, Müge; Zabci, Cengiz; Sançar, Taylan; Sunal, Gürsel; Natalin, Boris A.

    2016-04-01

    , are mostly seen at the NE part of the study region. We observe several knick points along the longitudinal channel profiles that mostly fits to the surface trace of the OF. The existence of multiple knick points along the same channel profiles on the southwestern sections of the fault are interpreted to be the result of multiple parallel/sub-parallel branches of the OF in this region. The integrated preliminary results of all applied methods indicate the evidence of a stronger deformation at the northeastern part of the OF, in addition to the OB section. The deformation significantly diffuses to the southwest of the OB, where the main fault bifurcates into several branches. In order to explain the distribution of the deformation style along the OF, we suggest three hypotheses: (a) the OF is confined within a very narrow zone in its most northeastern parts, and the total strain is distributed at its southwestern section (especially to the southwest of the OB), (b) The high asymmetric values, calculated at the northeastern OF, are mainly affected by another major tectonic structure, the North Anatolian Shear Zone, at this region or (c) the combined effect of these two settings. Our further studies, which will include the analyzing the lithological properties of drainage basins, detailed fault mapping, and understanding the cumulative horizontal slip by constructing and comparing the pseudo-palaeotopography at both sides of the fault, are going to provide more detailed information on the activity and the style of deformation along the OF. This study is supported by TÜBİTAK project no. 114Y227. References -AFAD, 2013, Son 48 saatte 48 deprem (48 earthquakes at the last 48 hours) http://www.afad.gov.tr/TR/HaberDetay.aspx?IcerikID=1511&ID=12, Volume 2013. -Aktuǧ, B., Dikmen, Ü., Doǧru, A., and Özener, H., 2013, Seismicity and strain accumulation around Karliova Triple Junction (Turkey): Journal of Geodynamics, v. 67, no. 0, p. 21-29. -Şengör, A. M. C., Görür, N

  18. Preliminary results on the tectonic activity of the Ovacık Fault (Malatya-Ovacık Fault Zone, Turkey): Implications of the morphometric analyses

    NASA Astrophysics Data System (ADS)

    Yazıcı, Müge; Zabci, Cengiz; Sançar, Taylan; Sunal, Gürsel; Natalin, Boris A.

    2016-04-01

    , are mostly seen at the NE part of the study region. We observe several knick points along the longitudinal channel profiles that mostly fits to the surface trace of the OF. The existence of multiple knick points along the same channel profiles on the southwestern sections of the fault are interpreted to be the result of multiple parallel/sub-parallel branches of the OF in this region. The integrated preliminary results of all applied methods indicate the evidence of a stronger deformation at the northeastern part of the OF, in addition to the OB section. The deformation significantly diffuses to the southwest of the OB, where the main fault bifurcates into several branches. In order to explain the distribution of the deformation style along the OF, we suggest three hypotheses: (a) the OF is confined within a very narrow zone in its most northeastern parts, and the total strain is distributed at its southwestern section (especially to the southwest of the OB), (b) The high asymmetric values, calculated at the northeastern OF, are mainly affected by another major tectonic structure, the North Anatolian Shear Zone, at this region or (c) the combined effect of these two settings. Our further studies, which will include the analyzing the lithological properties of drainage basins, detailed fault mapping, and understanding the cumulative horizontal slip by constructing and comparing the pseudo-palaeotopography at both sides of the fault, are going to provide more detailed information on the activity and the style of deformation along the OF. This study is supported by TÜBİTAK project no. 114Y227. References -AFAD, 2013, Son 48 saatte 48 deprem (48 earthquakes at the last 48 hours) http://www.afad.gov.tr/TR/HaberDetay.aspx?IcerikID=1511&ID=12, Volume 2013. -Aktuǧ, B., Dikmen, Ü., Doǧru, A., and Özener, H., 2013, Seismicity and strain accumulation around Karliova Triple Junction (Turkey): Journal of Geodynamics, v. 67, no. 0, p. 21-29. -Şengör, A. M. C., Görür, N

  19. Active faulting Vs other surface displacing complex geomorphic phenomena. Case studies from a tectonically active area, Abruzzi Region, central Apennines, Italy

    NASA Astrophysics Data System (ADS)

    Lo Sardo, Lorenzo; Gori, Stefano; Falcucci, Emanuela; Saroli, Michele; Moro, Marco; Galadini, Fabrizio; Lancia, Michele; Fubelli, Giandomenico; Pezzo, Giuseppe

    2016-04-01

    How can be univocally inferred the genesis of a linear surface scarp as the result of an active and capable fault (FAC) in tectonically active regions? Or, conversely, how it is possible to exclude that a scarp is the result of a capable fault activation? Trying to unravel this open questions, we show two ambiguous case studies about the problem of the identification of active and capable faults in a tectonically active area just based on the presence of supposed fault scarps at surface. The selected cases are located in the area comprised between the Middle Aterno Valley Fault (MAVF) and the Campo Imperatore Plain (Abruzzi Region, central Apennines), nearby the epicentral area of the April 6th, 2009 L'Aquila earthquake. In particular, the two case studies analysed are located in a region characterized by a widespread Quaternary faults and by several linear scarps: the case studies of (i) Prata D'Ansidonia area and (ii) Santo Stefano di Sessanio area. To assess the origin and the state of activity of the investigated geomorphic features, we applied a classical geological and geomorphological approach, based on the analysis of the available literature, the interpretation of the aerial photographs, field surveying and classical paleoseismological approach, the latter consisting in digging excavations across the analysed scarps. These analysis were then integrated by morphometrical analyses. As for case (i), we focused on determining the geomorphic "meaning" of linear scarps carved onto fluvial-deltaic conglomerates (dated to the Early Pleistocene; Bertini and Bosi, 1993), up to 3 meters high and up to 1,5 km long, that border a narrow, elongated and flat-bottom depressions, filled by colluvial deposits. These features groove the paleo-landsurface of Valle Daria (Bosi and Bertini, 1970), wide landsurface located between Barisciano and Prata D'Ansidonia. Entwining paleoseismological trenching with geophysical analyses (GPR, ERT and microgravimetrical prospections), it

  20. Retrospective salt tectonics

    SciTech Connect

    Jackson, M.P.A.

    1996-12-31

    The conceptual breakthroughs in understanding salt tectonics can be recognized by reviewing the history of salt tectonics, which divides naturally into three parts: the pioneering era, the fluid era, and the brittle era. The pioneering era (1856-1933) featured the search for a general hypothesis of salt diapirism, initially dominated by bizarre, erroneous notions of igneous activity, residual islands, in situ crystallization, osmotic pressures, and expansive crystallization. Gradually data from oil exploration constrained speculation. The effects of buoyancy versus orogeny were debated, contact relations were characterized, salt glaciers were discovered, and the concepts of downbuilding and differential loading were proposed as diapiric mechanisms. The fluid era (1933-{approximately}1989) was dominated by the view that salt tectonics resulted from Rayleigh-Taylor instabilities in which a dense fluid overburden having negligible yield strength sinks into a less dense fluid salt layer, displacing it upward. Density contrasts, viscosity contrasts, and dominant wavelengths were emphasized, whereas strength and faulting of the overburden were ignored. During this era, palinspastic reconstructions were attempted; salt upwelling below thin overburdens was recognized; internal structures of mined diapirs were discovered; peripheral sinks, turtle structures, and diapir families were comprehended; flow laws for dry salt were formulated; and contractional belts on divergent margins and allochthonous salt sheets were recognized. The 1970s revealed the basic driving force of salt allochthons, intrasalt minibasins, finite strains in diapirs, the possibility of thermal convection in salt, direct measurement of salt glacial flow stimulated by rainfall, and the internal structure of convecting evaporites and salt glaciers. The 1980`s revealed salt rollers, subtle traps, flow laws for damp salt, salt canopies, and mushroom diapirs.

  1. Park-like campus settings and physical activity

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Background: Urban communities can have limited access to natural environments for physical activity. Parks and college campuses may serve as pastoral islands within urban centers to promote physical activity. Purpose: To utilize a course centered on a quantitative field research experience to provi...

  2. Impact Tectonics

    NASA Astrophysics Data System (ADS)

    Koeberl, Christian; Henkel, Herbert

    This volume is the 8th in a series of impact books resulting from the activities of the scientific program "Response of the Earth System to Impact Processes" (IMPACT), by the European Science Foundation. The book resulted from an international meeting at Mora, Sweden, which was held as part of the IMPACT program. The papers cover various structural geologic, geochemical, and geophysical topics on research of asteroid impact structures on Earth and Mars.

  3. Tectonic Setting and Characteristics of Natural Fractures in Mesaverde and Dakota Reservoirs of the San Juan Basin, New Mexico and Colorado

    SciTech Connect

    LORENZ, JOHN C.; COOPER, SCOTT P.

    2001-01-01

    A set of vertical extension fractures, striking N-S to NNE-SSW but with local variations, is present in both the outcrop and subsurface in both Mesaverde and Dakota sandstones. Additional sets of conjugate shear fractures have been recognized in outcrops of Dakota strata and may be present in the subsurface. However, the deformation bands prevalent locally in outcrops in parts of the basin as yet have no documented subsurface equivalent. The immature Mesaverde sandstones typically contain relatively long, irregular extension fractures, whereas the quartzitic Dakota sandstones contain short, sub-parallel, closely spaced, extension fractures, and locally conjugate shear planes as well. Outcrops typically display secondary cross fractures which are rare in the subsurface, although oblique fractures associated with local structures such as the Hogback monocline may be present in similar subsurface structures. Spacings of the bed-normal extension fractures are approximately equal to or less than the thicknesses of the beds in which they formed, in both outcrop and subsurface. Fracture intensities increase in association with faults, where there is a gradation from intense fracturing into fault breccia. Bioturbation and minimal cementation locally inhibited fracture development in both formations, and the vertical limits of fracture growth are typically at bedding/lithology contrasts. Fracture mineralizations have been largely dissolved or replaced in outcrops, but local examples of preserved mineralization show that the quartz and calcite common to subsurface fractures were originally present in outcrop fractures. North-south trending compressive stresses created by southward indentation of the San Juan dome area (where Precambrian rocks are exposed at an elevation of 14,000 ft) and northward indentation of the Zuni uplift, controlled Laramide-age fracturing. Contemporaneous right-lateral transpressive wrench motion due to northeastward translation of the basin was both

  4. Fault kinematics and tectonic stress in the seismically active Manyara Dodoma Rift segment in Central Tanzania Implications for the East African Rift

    NASA Astrophysics Data System (ADS)

    Macheyeki, Athanas S.; Delvaux, Damien; De Batist, Marc; Mruma, Abdulkarim

    2008-07-01

    The Eastern Branch of the East African Rift System is well known in Ethiopia (Main Ethiopian Rift) and Kenya (Kenya or Gregory Rift) and is usually considered to fade away southwards in the North Tanzanian Divergence, where it splits into the Eyasi, Manyara and Pangani segments. Further towards the south, rift structures are more weakly expressed and this area has not attracted much attention since the mapping and exploratory works of the 1950s. In November 4, 2002, an earthquake of magnitude Mb = 5.5 struck Dodoma, the capital city of Tanzania. Analysis of modern digital relief, seismological and geological data reveals that ongoing tectonic deformation is presently affecting a broad N-S trending belt, extending southward from the North Tanzanian Divergence to the region of Dodoma, forming the proposed "Manyara-Dodoma Rift segment". North of Arusha-Ngorongoro line, the rift is confined to a narrow belt (Natron graben in Tanzania) and south of it, it broadens into a wide deformation zone which includes both the Eyasi and Manyara grabens. The two-stage rifting model proposed for Kenya and North Tanzania also applies to the Manyara-Dodoma Rift segment. In a first stage, large, well-expressed topographic and volcanogenic structures were initiated in the Natron, Eyasi and Manyara grabens during the Late Miocene to Pliocene. From the Middle Pleistocene onwards, deformations related to the second rifting stage propagated southwards to the Dodoma region. These young structures have still limited morphological expressions compared to the structures formed during the first stage. However, they appear to be tectonically active as shown by the high concentration of moderate earthquakes into earthquake swarms, the distribution of He-bearing thermal springs, the morphological freshness of the fault scarps, and the presence of open surface fractures. Fault kinematic and paleostress analysis of geological fault data in basement rocks along the active fault lines show that recent

  5. Activity Settings and Daily Routines in Preschool Classrooms: Diverse Experiences in Early Learning Settings for Low-Income Children

    PubMed Central

    Fuligni, Allison Sidle; Howes, Carollee; Huang, Yiching; Hong, Sandra Soliday; Lara-Cinisomo, Sandraluz

    2011-01-01

    This paper examines activity settings and daily classroom routines experienced by 3- and 4-year-old low-income children in public center-based preschool programs, private center-based programs, and family child care homes. Two daily routine profiles were identified using a time-sampling coding procedure: a High Free-Choice pattern in which children spent a majority of their day engaged in child-directed free-choice activity settings combined with relatively low amounts of teacher-directed activity, and a Structured-Balanced pattern in which children spent relatively equal proportions of their day engaged in child-directed free-choice activity settings and teacher-directed small- and whole-group activities. Daily routine profiles were associated with program type and curriculum use but not with measures of process quality. Children in Structured-Balanced classrooms had more opportunities to engage in language and literacy and math activities, whereas children in High Free-Choice classrooms had more opportunities for gross motor and fantasy play. Being in a Structured-Balanced classroom was associated with children’s language scores but profiles were not associated with measures of children’s math reasoning or socio-emotional behavior. Consideration of teachers’ structuring of daily routines represents a valuable way to understand nuances in the provision of learning experiences for young children in the context of current views about developmentally appropriate practice and school readiness. PMID:22665945

  6. Activity Settings and Daily Routines in Preschool Classrooms: Diverse Experiences in Early Learning Settings for Low-Income Children.

    PubMed

    Fuligni, Allison Sidle; Howes, Carollee; Huang, Yiching; Hong, Sandra Soliday; Lara-Cinisomo, Sandraluz

    2012-06-01

    This paper examines activity settings and daily classroom routines experienced by 3- and 4-year-old low-income children in public center-based preschool programs, private center-based programs, and family child care homes. Two daily routine profiles were identified using a time-sampling coding procedure: a High Free-Choice pattern in which children spent a majority of their day engaged in child-directed free-choice activity settings combined with relatively low amounts of teacher-directed activity, and a Structured-Balanced pattern in which children spent relatively equal proportions of their day engaged in child-directed free-choice activity settings and teacher-directed small- and whole-group activities. Daily routine profiles were associated with program type and curriculum use but not with measures of process quality. Children in Structured-Balanced classrooms had more opportunities to engage in language and literacy and math activities, whereas children in High Free-Choice classrooms had more opportunities for gross motor and fantasy play. Being in a Structured-Balanced classroom was associated with children's language scores but profiles were not associated with measures of children's math reasoning or socio-emotional behavior. Consideration of teachers' structuring of daily routines represents a valuable way to understand nuances in the provision of learning experiences for young children in the context of current views about developmentally appropriate practice and school readiness. PMID:22665945

  7. A tectonically controlled basin-fill within the Valle del Cauca, West-Central Colombia

    SciTech Connect

    Rine, J.M.; Keith, J.F. Jr.; Alfonso, C.A.; Ballesteros, I.; Laverde, F.; Sacks, P.E.; Secor, D.T. Jr. ); Perez, V.E.; Bernal, I.; Cordoba, F.; Numpaque, L.E. )

    1993-02-01

    Tertiary strata of the Valle del Cauca reflect a forearc/foreland basin tectonic history spanning a period from pre-uplift of the Cordillera Central to initiation of uplift of the Cordillera Occidental. Stratigraphy of the Valle del Cauca begins with Jurassic-Cretaceous rocks of exotic and/or volcanic provenance and of oceanic origin. Unconformably overlying these are Eocene to Oligocene basal quartz-rich sandstones, shallow marine algal limestones, and fine-grained fluvial/deltaic mudstones and sandstones with coalbeds. These Eocene to Oligocene deposits represent a period of low tectonic activity. During late Oligocene to early Miocene, increased tectonic activity produced conglomeratic sediments which were transported from east to west, apparently derived from uplift of the Cordillera Central, and deposited within a fluvial to deltaic setting. East-west shortening of the Valle del Cauca basin folded the Eocene to early Miocene units, and additional uplift of the Cordillera Central during the later Miocene resulted in syn-tectonic deposition of alluvial fans. After additional fold and thrust deformation of the total Eocene-Miocene basin-fill, tectonic activity abated and Pliocene-Quaternary alluvial and lacustrine strata were deposited. Within the framework of this depositional and tectonic history of the Valle del Cauca, hydrocarbon exploration strategies can be formulated and evaluated.

  8. Activity Settings and Daily Routines in Preschool Classrooms: Diverse Experiences in Early Learning Settings for Low-Income Children

    ERIC Educational Resources Information Center

    Fuligni, Allison Sidle; Howes, Carollee; Huang, Yiching; Hong, Sandra Soliday; Lara-Cinisomo, Sandraluz

    2012-01-01

    This paper examines activity settings and daily classroom routines experienced by 3- and 4-year-old low-income children in public center-based preschool programs, private center-based programs, and family child care homes. Two daily routine profiles were identified using a time-sampling coding procedure: a High Free-Choice pattern in which…

  9. A quantitative geomorphological approach to constraining the volcanic and tectonic evolution of the active Dabbahu rift segment, Afar, Ethiopia.

    NASA Astrophysics Data System (ADS)

    Medynski, Sarah; Pik, Raphaël; Burnard, Peter; Vye-Brown, Charlotte; Blard, Pierre-Henri; France, Lydéric; Dumont, Stéphanie; Grandin, Raphaël; Schimmelpfennig, Irene; Benedetti, Lucilla; Ayalew, Dereje; Yirgu, Gezahegn

    2013-04-01

    In the Afar depression (Ethiopia), extension is organised along rift segments that morphologically resemble oceanic rifts. Segmentation results from interactions between dyke injection and volcanism, as observed during the well-documented 2005 rifting event on the Dabbahu rift segment. This tectono-volcanic crisis was observed in detail via remote sensing techniques, providing invaluable information on the present-day tectonic - magmatic interplay during a sequence of dyke intrusions. However, lack of data remains on timescales of 1 to 100 kyr, the period over which the main morphology of the rift is acquired. The Dabbahu rift segment represents an ideal natural laboratory to study the evolution of rift morphology as a response to volcanic and tectonic influences. We use cosmogenic nuclides (3He and 36Cl) to determine the ages of young (<100 kyr) lava flows and to date the initiation and movement of fault scarps, which cut the lavas. Where possible, we analysed vertical profiles along fault scarps, in an attempt to distinguish individual tectonic events that offset the scarp, estimate their amplitudes and date the recurrence intervals. These geochronological constraints, combined with major & trace element compositions, field mapping and digital mapping (Landsat, ASTER and SPOT imagery), provide valuable insights on the magmatic and tectonic history of the segment. The results show that over the last 100 ka, the northern part of the Dabbahu segment was supplied by at least two different magma reservoirs, which can be identified from their distinctive chemistries. The main reservoir is located beneath Dabbahu volcano at the northern tip of the rift segment, and has been supplied with magma for at least 72 ka. The second reservoir is located further south on the rift axis and corresponds to the current mid-segment magma chamber, which was responsible for the 2005 rifting episode. Two magmatic cycles linked to the Dabbahu magma chamber were recorded, lasting 20-30 kyr

  10. Active tectonic features and structural dynamics of the summit area of Mt. Etna (Italy) revealed by soil CO2 and soil temperature surveying

    NASA Astrophysics Data System (ADS)

    Giammanco, Salvatore; Melián, Gladys; Neri, Marco; Hernández, Pedro A.; Sortino, Francesco; Barrancos, José; López, Manuela; Pecoraino, Giovannella; Perez, Nemesio M.

    2016-02-01

    This work presents the results of an extensive geochemical survey aimed at measuring soil CO2 effluxes and soil temperatures over a large portion of Mt. Etna's summit area, coupled with an updated structural survey of the same area. The main goals of this study were i) to find concealed or hidden volcano-tectonic structures in the studied area by detecting anomalous soil gas emissions, ii) to investigate the origin of the emitted gas and the mechanism of gas and heat transport to the surface, iii) to produce a structural model based both on the surface geology and on the soil gas data and, lastly, iv) to contribute to the assessment of hazard from slope failure and crater collapses at Mt. Etna. The results revealed many concealed structural lines that followed the major directions of structural weakness in the summit area of Mt. Etna, mostly due to a combined action of gravitational spreading of the volcano and magma intrusions. Both recent and old volcano-tectonic lines were found to act as pathways for the leakage of magmatic gases to the surface. An important role in driving magmatic gases to the surface is also played by fracturing and faulting due to caldera-forming collapses and smaller crater collapses. Correlation between soil CO2 emissions and soil temperature allowed discriminating areas of active shallow hydrothermal circulation along deep fractures (characterized by high values of both parameters, but mostly soil temperature) from those affected by undeveloped fractures that did not reach the surface (characterized by high CO2 emissions at low temperature). The former corresponded to weak zones of the volcano edifice that were frequently site of past eruptions, indicating that those areas keep a high potential for future opening of eruptive fissures. The latter were likely related to sites where new eruptive fissures may open in the near future due to backward propagation of extensional tectonic stress.

  11. Petrogenesis and tectonic setting of Triassic granitoids in the Qiangtang terrane, central Tibet: Evidence from U-Pb ages, petrochemistry and Sr-Nd-Hf isotopes

    NASA Astrophysics Data System (ADS)

    Li, Guang-Ming; Li, Jin-Xiang; Zhao, Jun-Xing; Qin, Ke-Zhang; Cao, Ming-Jian; Evans, Noreen J.

    2015-06-01

    Triassic granitoids, including the ∼220 Ma Shuanghu and ∼210 Ma Rongma granitoids studied here, are widely distributed around the Longmu-Shuanghu suture and in the Qiangtang terrane, central Tibet. The majority of these granitoids can be classified as high-K calc-alkaline in nature and yield negative Ba and Sr anomalies on primitive mantle-normalized diagrams. In addition, they are: enriched in light rare earth elements (LREE) ((La/Yb)N = 1.61-21.79); strongly enriched in large ion lithophile elements (LILE: e.g., Cs, Rb, and K), and depleted in high field strength elements (HFSE: e.g., Nb and Ti). Magma mixing played a role in the genesis of the Shuanghu granodiorites, as indicated by the occurrence of dioritic enclaves and the wide range in zircon Hf compositions (εHf(t) = -15.0 to -2.5). The I-type Shuanghu granodiorites and S-type Shuanghu and Rongma granites might have been derived from melting of southern Qiangtang crust given the high initial Sr (0.7131-0.7272), low εNd(t) (-8.9 to -11.1) and zircon εHf(t) values (-15 to -7.2). The granitoids may have formed during melting of southern Qiangtang crust, heated by upwelling asthenosphere mantle, a result of break-off and delamination of the Paleo-Tethys slab in a collisional setting.

  12. Tectonic provinces of the Atlantic Ocean

    NASA Astrophysics Data System (ADS)

    Pushcharovsky, Yu. M.

    2009-05-01

    The tectonic structure of the floor of the Atlantic Ocean beyond the continental margins is insufficiently studied. This is also true of its tectonic demarcation. The segmentation of the floor into regional-scale tectonic provinces of several orders proposed in this paper is primarily based on structural and historical geological features. It is shown that deep oceanic basins and fault tectonics are of particular importance in this respect. Tectonic provinces of two orders are distinguished by a set of attributes. The first-order provinces are the North, Central, South, and Antarctic domains of the Atlantic Ocean. They are separated by wide demarcation fracture zones into Transatlantic (transverse) second-order tectonic provinces. Ten such provinces are recognized (from the north southward): Greenland-Lofoten, Greenland-Scandinavia, Greenland-Ireland, Newfoundland-European, North American-African, Antilles-African, Angola-Brazil, Cape-Argentine, North Antarctic, and South Antarctic. This subdivision demonstrates significant differentiation in the geodynamic state of the oceanic lithosphere that determines nonuniform ocean formation and the tectonic features of the ocean floor. The latitudinal orientation of the second-order provinces inherits the past tectonic pattern, though newly formed structural units cannot be ruled out. The Earth rotation exerts a crucial effect on the crust and the mantle.

  13. Detrital zircon U-Pb ages of the Proterozoic metaclastic-sedimentary rocks in Hainan Province of South China: New constraints on the depositional time, source area, and tectonic setting of the Shilu Fe-Co-Cu ore district

    NASA Astrophysics Data System (ADS)

    Wang, Zhilin; Xu, Deru; Hu, Guocheng; Yu, Liangliang; Wu, Chuanjun; Zhang, Zhaochong; Cai, Jianxin; Shan, Qiang; Hou, Maozhou; Chen, Huayong

    2015-12-01

    The Shilu Fe-Co-Cu ore district, located at Hainan Province of South China, is well known for high-grade hematite-rich Fe ores and also two Precambrian host successions, i.e. the Shilu Group and the overlying Shihuiding Formation. This district has been interpreted as a banded iron formation (BIF) deposit-type, but its depositional time, source area and depositional setting have been in debate due to poor geochronological work. Detrital zircon U-Pb dating aided by cathodoluminescence imaging has been carried out on both the Shilu Group and Shihuiding Formation. Most of the zircon grains from both the successions are subrounded to rounded in morphology and have age spectra between 2000 Ma and 900 Ma with two predominant peaks at ca. 1460-1340 Ma and 1070 Ma, and three subordinate peaks at ca. 1740-1660 Ma, 1220 Ma and 970 Ma. The similar age distribution suggests the same depositional system for both successions. Linked to the geological and paleontological signatures, the Shihuiding Formation is better re-interpreted as the top, i.e. Seventh member of the Shilu Group, rather than a distinct Formation. The youngest statistical zircon age peaks for both successions, i.e. ca. 1070-970 Ma may define the maximum depositional time of the Shilu Group and interbedded BIFs. At least two erosional sources are required for deposition of the studied detrital zircons, with one proximal to provide the least abraded zircons and the other distal or recycled to offer the largely abraded zircons. The predominance of rounded or subrounded zircons over angular zircons probably implies a relatively stable tectonic setting during deposition. Given the Precambrian tectonics of Hainan Island, a retro-arc foreland basin is proposed for the deposition of the Shilu Group and interbedded BIFs. In comparison with those from the South China and other typical Grenvillian orogens, the detrital zircon age populations reveal that Hainan Island had crystalline basement similar to neither the Yangtze

  14. The tectonic puzzle of the Messina area (Southern Italy): Insights from new seismic reflection data

    PubMed Central

    Doglioni, Carlo; Ligi, Marco; Scrocca, Davide; Bigi, Sabina; Bortoluzzi, Giovanni; Carminati, Eugenio; Cuffaro, Marco; D'Oriano, Filippo; Forleo, Vittoria; Muccini, Filippo; Riguzzi, Federica

    2012-01-01

    The Messina Strait, that separates peninsular Italy from Sicily, is one of the most seismically active areas of the Mediterranean. The structure and seismotectonic setting of the region are poorly understood, although the area is highly populated and important infrastructures are planned there. New seismic reflection data have identified a number of faults, as well as a crustal scale NE-trending anticline few km north of the strait. These features are interpreted as due to active right-lateral transpression along the north-eastern Sicilian offshore, coexisting with extensional and right-lateral transtensional tectonics in the southern Messina Strait. This complex tectonic network appears to be controlled by independent and overlapping tectonic settings, due to the presence of a diffuse transfer zone between the SE-ward retreating Calabria subduction zone relative to slab advance in the western Sicilian side. PMID:23240075

  15. The tectonic puzzle of the Messina area (Southern Italy): insights from new seismic reflection data.

    PubMed

    Doglioni, Carlo; Ligi, Marco; Scrocca, Davide; Bigi, Sabina; Bortoluzzi, Giovanni; Carminati, Eugenio; Cuffaro, Marco; D'Oriano, Filippo; Forleo, Vittoria; Muccini, Filippo; Riguzzi, Federica

    2012-01-01

    The Messina Strait, that separates peninsular Italy from Sicily, is one of the most seismically active areas of the Mediterranean. The structure and seismotectonic setting of the region are poorly understood, although the area is highly populated and important infrastructures are planned there. New seismic reflection data have identified a number of faults, as well as a crustal scale NE-trending anticline few km north of the strait. These features are interpreted as due to active right-lateral transpression along the north-eastern Sicilian offshore, coexisting with extensional and right-lateral transtensional tectonics in the southern Messina Strait. This complex tectonic network appears to be controlled by independent and overlapping tectonic settings, due to the presence of a diffuse transfer zone between the SE-ward retreating Calabria subduction zone relative to slab advance in the western Sicilian side. PMID:23240075

  16. Earthquakes and plate tectonics.

    USGS Publications Warehouse

    Spall, H.

    1982-01-01

    Earthquakes occur at the following three kinds of plate boundary: ocean ridges where the plates are pulled apart, margins where the plates scrape past one another, and margins where one plate is thrust under the other. Thus, we can predict the general regions on the earth's surface where we can expect large earthquakes in the future. We know that each year about 140 earthquakes of magnitude 6 or greater will occur within this area which is 10% of the earth's surface. But on a worldwide basis we cannot say with much accuracy when these events will occur. The reason is that the processes in plate tectonics have been going on for millions of years. Averaged over this interval, plate motions amount to several mm per year. But at any instant in geologic time, for example the year 1982, we do not know, exactly where we are in the worldwide cycle of strain build-up and strain release. Only by monitoring the stress and strain in small areas, for instance, the San Andreas fault, in great detail can we hope to predict when renewed activity in that part of the plate tectonics arena is likely to take place. -from Author

  17. Setting the Stage for Physical Activity for Secondary Students

    ERIC Educational Resources Information Center

    Ciccomascolo, Lori; Riebe, Deborah

    2006-01-01

    Despite the positive long-term physiological and psychological effects of exercise, many young adults between the ages of 12 and 21 years do not participate in regular physical activity. With the time constraints and other challenges in teaching and assessing students, physical educators need realistic strategies that will help in their efforts to…

  18. Predicting Physical Activity Promotion in Health Care Settings.

    ERIC Educational Resources Information Center

    Faulkner, Guy; Biddle, Stuart

    2001-01-01

    Tested the theory of planned behavior's (TPB) ability to predict stage of change for physical activity promotion among health professionals. Researchers measured attitudes, subjective norms, intentions, perceived behavioral control, and stage of change, then later reassessed stage of change. TPB variables of attitude, subjective norms, perceived…

  19. Input of UAV, DTM photo-interpretation and SAR interferometry on active tectonics applied on the Southern Coastal Range (SE Taiwan)

    NASA Astrophysics Data System (ADS)

    Deffontaines, Benoit; Chang, Kuo-Jen; Champenois, Johann; Magalhaes, Samuel; Serries, Gregory

    2016-04-01

    Taiwan is an excellent geomorphic laboratory where both extreme climatic events and high active tectonics compete. Moreover many Earth Sciences and Environmental data bases exist nowadays that help to better constrain both structural geology and active deformations. The latter unfortunately is still poorly known in the Cosatal Range of E.Taiwan in terms of geology due to access difficulties, high relief, paucity of roads, tropical vegetation and high climatic events (typhoons and heavy rainfall) and so on. Indirect methods such as photogrammetric survey using UAV's helps a lot to get high resolution topographic DEM and DTM, better than 10cm in planimetry, that helps a lot to get through careful photo-interpretation, a bird's eye view of the geology. Therefore we were able to much update the famous pre-existing geological maps (Wang and Chen, 1993). Moreover, by combining our high resolution topographic results with those of SAR interferometry (database of Champenois et al, EPSL, 2012), we were able to identify, characterise and quantify the differential active features toward the LOS of the Coastal Range (eastern Taiwan). In order to synthetise and to model the deformation of that famous place, we herein constructed more than 500 parallel projected profiles in order to locate, characterize and quantify the active tectonic features and compare them to the topography and the updated photo-interpreted geology (this work). We then were able to reconstruct the structural geometry of the Coastal Range and the Longitudinal Valley in SE Taiwan. Among our results, we reveal and prove : 1. the whole 2cm differential surrection of the Coastal Range ; 2. the differential displacement between both Central and Coastal Ranges ; 3. we explain the location of the Pinantashi river situated within the Lichi melange that correspond to the maximum surrection of the Coastal Range ; 4. we reveal the different units and their relative displacement within the Coastal Range itself ; 5. we

  20. Triassic post collision igneous activity and granulite facies metamorphic event in the Yangpyeong area, South Korea and its meaning to the tectonics of Northeast Asia

    NASA Astrophysics Data System (ADS)

    Lee, S.; Oh, C.

    2009-12-01

    The Korean peninsula is tectonically positioned in the eastern margin of the Asia continent and the Gyeonggi massif is situated in the center part of Korean peninsula. Triassic (231 Ma) eclogite was first found in the Hongseong area, the southwestern part of the Gyeonggi Massif, which suggested that the Hongseong area is the extension of Triassic collision belt between the North and South China blocks, in China. The 257-226 post-collisional mangerite was also found in the Odesan area, the eastern part of Gyeonggi massif. Based on these new findings, it was proposed that the line connecting Hongseong and Odesan areas is the collision belt between the North and South China blocks. It was also reported that 247 Ma ultrahigh temperature metamorphism occurred together with the intrusion of mangerite in the Odesan area indicating that regional metamorphism occurred together with the post-collision igneous activity. The Yangpyeong area locates in the middle part of the Hongseong-Odesan collision belt. The area mainly consists of Precambrian migmatitic gneiss which was intruded by Triassic igneous complex. The igneous complex mainly consists of gabbro and porpyritic syeno-diorite and SHRIMP age dating indicates that they intruded at 227 ± 4 Ma. They are shoshonitic and high-K series and have high Ba, Sr contents. They show LREE enriched pattern and Nb, Ta, P, Ti depletion in the chondrite- and primitive-mantle-normalized trace element patterns, respectively. In the tectonic discrimination diagrams, gabbros are plotted in the within plate tectonic field and porpyritic syeno-diorites are plotted in the Post-collision field. These geochemical characters indicate that they formed in the within plate after continental collision. Two metamorphic ages (1861 ± 6 Ma, and 235 ± 6 Ma) are obtained from the migmatitic gneiss. The peak metamorphic conditions of the first Precambrian metamorphism are 750-780°C and 8-10 kbar indicating intermediate-P/T metamorphism. On the other hand