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Sample records for alboran sea basin

  1. Evolution of a Miocene sag basin in the Alboran Sea

    NASA Astrophysics Data System (ADS)

    Do Couto, D.; Gorini, C.; Jolivet, L.; Letouzey, J.; Smit, J.; d'Acremont, E.; Auxietre, J. L.; Le Pourhiet, L.; Estrada, F.; Elabassi, M.; Ammar, A.; Jabour, H.; Vendeville, B.

    2012-04-01

    The Alboran domain represents the westernmost termination of the peri-Mediterranean Alpine orogen. Its arcuate shape, delimited to the North by the Betic range and to the South by the Rif range, is the result of subduction, collision and slab migration processes. During the Neogene, several sedimentary basins formed on the Betics metamorphic basement, mainly due to the extensional collapse of the previously thickened crust of the Betic-Rif belt. The major sedimentary depocentre, the Western Alboran Basin (WAB), is surrounded by the Gibraltar arc, the volcanic Djibouti mounts and the Alboran ridge, and is partly affected by shale tectonics and associated mud volcanism. High-quality 2-D seismic profiles acquired along the Moroccan margin during the last decade reveal a complete history of the basin. Our study deals with the analysis of seismic profiles oriented parallel and orthogonal to the Mediterranean Moroccan margin. The stratigraphy was calibrated using well data from offshore Spain and Morocco. Our study focuses particularly on the tectono-stratigraphic reconstruction of the basin. The formation of the WAB began in the Early Miocene (Aquitanian - Burdigalian). A massive unit of Early Miocene to Lower Langhian shales and olistostromes forms a thick mobile décollement layer that controls and accommodates deformation of the basin fill. From the Upper Langhian to the Upper Tortonian, the basin is filled by a thick sequence of siliciclastic deposits. Stratigraphic geometries identified on seismic data clearly indicate that deformation of the basin fill started during deposition of Upper Langhian to the Upper Tortonian clastics. Shale tectonic deformation was re-activated recently, during the Messinian desiccation of the Mediterranean Sea (and the following catastrophic Pliocene reflooding) or during the Quaternary contourite deposition The sedimentary layers gently dip towards the basin centre and "onlaps" onto the basin margin, especially onto the basement high

  2. Seafloor morphology related to recent tectonics in the Alboran Sea Basin

    NASA Astrophysics Data System (ADS)

    Vázquez, Juan-Tomás; Estrada, Ferran; Vegas, Ramon; Ercilla, Gemma; Medialdea, Teresa; d'Acremont, Elia; Alonso, Belen; Fernández-Salas, Luis-Miguel; Gómez-Ballesteros, María; Somoza, Luis; Bárcenas, Patricia; Palomino, Desirée; Gorini, Christian

    2014-05-01

    A detailed geomorphological study of the northern part of the Alboran Sea Basin has been realized based on the combined analysis of multibeam swath bathymetric data and medium to very high resolution seismic profiles (singled Sparker, Airgun, TOPAS and Atlas PARASOUND P35). This has enabled us to define several tectonic-related seafloor features and their role in the recent tectonics. The observed morpho-tectonic features correspond to: i) lineal scarps with a wide range of dimensions and following several trends ,WNW-ESE, NE-SW, NNE-SSW and N-S; ii) NE-SW to NNE-SSW-oriented compressive ridges; iii) ENE-WSW to NE-SW-striking antiforms; iv) NNE-SSW-oriented lineal depressions; v) rhomb-shaped depressions; vi) lineal valleys, canyons and gullies with WNW-ESE, and N-S orientations; and vii) N-S directed dissected valleys, canyons and gullies. Three families of faults and related folds, with NE-SW, WNW-ESE and NNE-SSW to N-S have been interpreted within this geomorphological scheme. The NE-SW family corresponds to: a) major scarps in both flanks of the Alboran Ridge and b) the offshore prolongation of La Serrata Fault, and both have been considered as a set of sinistral strike-slip faults. To this family, some compressive ridges, antiforms and occasionally reverse faults have been correlated. The WNW-ESE family corresponds to a set of faulted valleys (occasionally with rhomb-shaped depressions), fault scarps and linear inflection points occurring in the northern Alboran margin and the Yusuf-Habibas corridor. This family has been interpreted as transtensive dextral strike-slip faults. The NNE-SSW to N-S family corresponds to a penetrative system of linear fault scarps and tectonic depressions that cross-cut the Alboran Ridge and the Djibouti-Motril marginal plateau. This family can be considered as more recent since it offsets the other two families and shows a minor importance with regard to the main reliefs. This communication is a contribution to the Spanish R + D

  3. A study of models and controls for basin formation during continental collision: (1) Australian lithosphere along Banda orogen (Indonesia) and (2) Alboran Sea basin (western Mediterranean)

    NASA Astrophysics Data System (ADS)

    Tandon, Kush

    Mechanisms for the formation of a foreland basin at the beginning of continental collision (Pliocene-Recent Australian continental foreland along the Banda orogen) and a post-orogenic, continental, Miocene extensional basin (Alboran Sea) are studied. Such a study investigates the controls on the basin formation during the start of the Wilson cycle and later during the break up of a thickened continent in a collisional environment. Effective Elastic Thickness (EET) of the Australian continental lithosphere from Roti to the Kai Plateau ({˜}121sp°{-}137sp°E longitude) are estimated using an elastic-half beam model to match the sea floor bathymetry and the Bouguer gravity anomalies. Range of constant EET values from 27-75 km across the shelf of Australian lithosphere shows a variation of 64% with the highest value in the vicinity of central Timor where the collision is most advanced. Downdip on the Australian continental lithosphere from shelf to beneath the Banda orogen, the reduction in EET is from ˜90 km-˜30 km (66%). Variations in EET can be explained by inelastic yielding (brittle and plastic failure, crust-mantle decoupling in the lower crust and brittle-ductile decoupling in the upper-middle crust) in the Australian lithosphere. Change in EET occurred at the start of continental subduction due to change in curvature, both in map and cross-sectional view. Oroclinal bending of the continental Australian lithosphere increased the inelastic failure in the eastern end. Different mechanisms of basin formation at a site of post-orogenic collapse are studied by constraining the timing of rifting in the western, eastern, and northern parts of the Alboran Sea basin on seismic reflectors via synthetic seismograms using ODP Leg 161 and Andalucia A-1 data. Regions of adjacent coeval compression and extension are found in the Alboran Sea basin. Normal faulting continues in parts of the eastern Alboran Sea basin later than in the western Alboran Sea basin. The development

  4. Tectonic and stratigraphic evolution of the Western Alboran Sea basin since the last 25 Myrs

    NASA Astrophysics Data System (ADS)

    Do Couto, Damien; Gorini, Christian; Jolivet, Laurent; Lebret, Noëmie; Augier, Romain; Gumiaux, Charles; D'Acremont, Elia; Ammar, Abdellah; Auxietre, Jean-Luc

    2016-04-01

    The Western Alboran Basin (WAB) formation has always been a matter of debate and was either considered as a backarc or a forearc basin. Based on stratigraphic analysis of high-resolution 2D seismic profiles mostly located offshore Morocco, the tectonic and stratigraphic history of the WAB is clarified. A thick pre-rift sequence is observed beneath the Miocene basin and interpreted as the topmost Malaguide/Ghomaride complex composing the Alboran domain. The structural position of this unit compared with the HP-LT exhumed Alpujarride/Sebtide metamorphic basement, leads us to link the Early Miocene subsidence of the basin with an extensional detachment. Above the Early Miocene, a thick Serravallian sequence marked by siliciclastic deposits is nearly devoid of extensional structures. Its overall landward to basinward onlap geometry indicates that the WAB has behaved as a sag basin during most of its evolution, from the Serravallian to the Late Tortonian. Tectonic reconstructions in map view and cross-section further suggest that the basin has always represented a strongly subsiding topographic low without internal deformation that has migrated westward together with the retreating slab. We propose that the subsidence of the WAB was controlled by the pull of the dipping subducting lithosphere explaining the large thickness (10 km) of the mostly undeformed sedimentary infill.

  5. Tectonic and stratigraphic evolution of the Western Alboran Sea Basin in the last 25 Myrs

    NASA Astrophysics Data System (ADS)

    Do Couto, Damien; Gorini, Christian; Jolivet, Laurent; Lebret, Noëmie; Augier, Romain; Gumiaux, Charles; d'Acremont, Elia; Ammar, Abdellah; Jabour, Haddou; Auxietre, Jean-Luc

    2016-05-01

    The Western Alboran Basin (WAB) formation has always been the subject of debate and considered either as a back-arc or a forearc basin. Stratigraphic analyses of high-resolution 2D seismic profiles mostly located offshore Morocco, enabled us to clarify the tectonic and stratigraphic history of the WAB. The thick pre-rift sequence located beneath the Miocene basin is interpreted as the topmost Malaguide/Ghomaride complex composing the Alboran domain. The structural position of this unit compared with the HP-LT exhumed Alpujarride/Sebtide metamorphic basement, leads us to link the Early Miocene subsidence of the basin with an extensional detachment. Above the Early Miocene, a thick Serravallian sequence marked by siliciclastic deposits is nearly devoid of extensional structures. Its overall landward to basinward onlap geometry indicates that the WAB has behaved as a sag basin during most of its evolution from the Serravallian to the late Tortonian. Tectonic reconstructions in map view and in cross section further suggest that the basin has always represented a strongly subsiding topographic low without internal deformation that migrated westward together with the retreating slab. We propose that the subsidence of the WAB was controlled by the pull of the dipping subducting lithosphere hence explaining the considerable thickness (10 km) of the mostly undeformed sedimentary infill.

  6. The Physical Oceanography of the Alboran Sea.

    DTIC Science & Technology

    1987-03-01

    geostrophic adjustment in sea de Alboran. Revista Las Ciencias XXV(4):765-779. straits and wide estuaries: theory and laboratory experi- Stevenson, R. E. (1977... Comunicaciones 3, Zaragoza: Whitehead, J. A. and A. R. Miller (1979). Labora- 1151-1166. tory simulation of the gyre in the Alboran Sea. Jour- Parrilla, G

  7. Evolution of the Alboran Sea hydrographic structures during July 1993

    NASA Astrophysics Data System (ADS)

    Lafuente, Jesús García.; Cano, Natalio; Vargas, Manuel; Rubín, Juan P.; Hernández-Guerra, Alonso

    1998-01-01

    During the ICTIOALBORAN-0793 multidisciplinary oceanographic survey carried out in July 1993 by the Instituto Español de Oceanografı´a (IEO) in the Alboran Sea, some anomalous features were detected. One was the presence of a small cyclonic eddy in the western Alboran Basin, close to the African coast. The upper layer of the eddy consisted of Mediterranean Surface Water and was separated from its supposed source (the northern Alboran Sea) by the Atlantic Jet. Another feature was the probable temporary interruption of the flow of fresh Atlantic Water (S≈36.5) into the eastern Alboran Basin and its replacement by a modified (saltier) Atlantic Water. These features can be explained assuming a time evolution of the surface circulation in the Alboran Sea forced by speed variations in the inflowing Atlantic Water through the Strait of Gibraltar. A collection of satellite images covering the survey period and across-strait sea level difference data, indicative of the geostrophic velocity of the inflow through the Strait, were used to check this assumption. Both sets of data supplied independent but compatible information in the sense that they complemented each other and gave support to the proposed evolving model. Finally, some speculative ideas attempting to correlate the inferred variability in the Alboran Sea with the state of the baroclinic water exchange through the Strait of Gibraltar (maximal or submaximal) are discussed.

  8. The Messinian erosional surface and early Pliocene reflooding in the Alboran Sea: New insights from the Boudinar basin, Morocco

    NASA Astrophysics Data System (ADS)

    Cornée, Jean-Jacques; Münch, Philippe; Achalhi, Mohammed; Merzeraud, Gilles; Azdimousa, Ali; Quillévéré, Frédéric; Melinte-Dobrinescu, Mihaela; Chaix, Christian; Moussa, Abdelkhalak Ben; Lofi, Johanna; Séranne, Michel; Moissette, Pierre

    2016-03-01

    New investigations in the Neogene Boudinar basin (Morocco) provide new information about the Messinian Salinity Crisis (MSC) and Zanclean reflooding in the southern part of the Alboran realm (westernmost Mediterranean). Based on a new field, sedimentological and palaeontological analyses, the age and the geometry of both the Messinian erosional surface (MES) and the overlying deposits have been determined. The MES is of late Messinian age and was emplaced in subaerial settings. In the Boudinar basin, a maximum of 200 m of Miocene sediments was eroded, including late Messinian gypsum blocks. The original geometry of the MES is preserved only when it is overlain by late Messinian continental deposits, conglomeratic alluvial fans or lacustrine marly sediments. These sediments are interpreted as indicators of the sea-level fall during the MSC. Elsewhere in the basin, the contact between late Messinian and early Pliocene deposits is a low-angle dipping, smooth surface that corresponds to the early Pliocene transgression surface that subsequently re-shaped the regressive MES. The early Pliocene deposits are characterized by: (i) their onlap onto either the basement of the Rif chain or the late Miocene deposits; (ii) lagoonal deposits at the base to offshore marls and sands at the top (earliest Pliocene; 5.33-5.04 Ma interval; foraminifer zone PL1); (iii) marine recovery occurring in the 5.32-5.26 Ma interval; and (iv) the change from lagoonal to offshore environments occurring within deposits tens of metres thick. This information indicates that at least the end of the reflooding period was progressive, not catastrophic as previously thought.

  9. Tectono-sedimentary evolution of the peripheral basins of the Alboran Sea in the arc of Gibraltar during the latest Messinian-Pliocene

    NASA Astrophysics Data System (ADS)

    Guerra-Merchán, Antonio; Serrano, Francisco; Hlila, Rachid; El Kadiri, Khalil; Sanz de Galdeano, Carlos; Garcés, Miguel

    2014-07-01

    In the peripheral basins of the Alboran Sea, five stratigraphic units (latest Messinian-Pliocene) separated by discontinuities and representing transgressive-regressive cycles have been recognized. The first unit (LM) is latest Messinian in age and precisely characterizes the Lago-Mare event at the end of the Messinian Salinity Crisis, i.e. just before the opening of the Strait of Gibraltar at the beginning of the Pliocene. The three following units (Pl-1, Pl-2 and Pl-3) are Zanclean in age, whereas the last one (Pl-4) is Piacenzian. These four Pliocene units consist of alluvial, deltaic, and littoral deposits in the marginal areas, changing to open marine deposits with planktonic components in the basinal areas, although their extension varies in each basin. Regionally, these units do not necessarily stack in a single stratigraphic succession because of tectonics that controlled their hosting basins. Thus, the LM and Pl-1 units occur only in the Malaga and Estepona-Marbella basins, revealing that the onset of the sedimentation after the Messinian evaporitic stage and the Pliocene transgression was not a single and synchronous event in the western Alboran Sea. Moreover, the Pl-3 and Pl-4 units do not appear in all basins, so that the subsequent continentalization process of these Alboran peripheral areas during the Pliocene was also diachronous. The sedimentary evolution of the peripheral basins was controlled mainly by tectonics. During the latest Messinian-early Pliocene, the sedimentation took place in a context marked by a NNW-SSE compression and ENE-WSW perpendicular tension. The onset of the sedimentation (LM and Pl-1 units) could be linked to preexisting E-W faults that mark part of the borders of the Malaga basin and the Estepona-Marbella sector. During the deposition of the Pl-2 unit, the movements of E-W, NW-SE, and NE-SW normal faults determined a continuous subsidence in several basins, resulting in the accumulation of thick clastic marine sequences (i

  10. Geodynamics of the Gibraltar Arc and the Alboran Sea region

    NASA Astrophysics Data System (ADS)

    Corsini, M.; Chalouan, A.; Galindo-Zaldivar, J.

    2014-07-01

    Located at the Westernmost tip of the Mediterranean sea, the Gibraltar Arc is a very complex zone. The Betics in Spain and the Rif belt in Morocco surround the Alboran sea characterized by a thinned continental crust. The geodynamic evolution of this region results from the convergence of African and Iberian margins since the Late Cretaceous. It is controlled both by plate convergence and mantle dynamics, which significantly impact on morphology, sedimentary environments, tectonics, metamorphism and magmatism. We present here the contents of the special issue on the Gibraltar Arc and nearby regions, following the workshop organized at the University Abdelmalek Essaadi of Tetouan in Morocco from 27 to 28 October, 2011. The goal of this international workshop was to have an overview of the actual advance in research concerning the Rif and Betics chains, the Alboran basin, and their influence on the Iberian and African forelands.

  11. Miocene shale tectonics in the Moroccan margin (Alboran Sea)

    NASA Astrophysics Data System (ADS)

    Do Couto, D.; El Abbassi, M.; Ammar, A.; Gorini, C.; Estrada, F.; Letouzey, J.; Smit, J.; Jolivet, L.; Jabour, H.

    2011-12-01

    The Betic (Southern Spain) and Rif (Morocco) mountains form an arcuate belt that represents the westernmost termination of the peri-mediterranean Alpine mountain chain. The Miocene Alboran Basin and its subbasins is located in the hinterland of the Betic-Rif belt. It is considered to be a back-arc basin that developed during the coeval westward motion of the Alboran domain and the extensional collapse of previously thickened crust of the Betic-Rif belt. The Western Alboran Basin (WAB) is the major sedimentary depocenter with a sediment thickness in excess of 10 km, it is bordered by the Gibraltar arc, the volcanic Djibouti mounts and the Alboran ridge. Part of the WAB is affected by shale tectonics and associated mud volcanism. High-quality 2D seismic profiles acquired on the Moroccan margin of the Alboran Basin during the last decade reveal the multiple history of the basin. This study deals with the analysis of a number of these seismic profiles that are located along and orthogonal to the Moroccan margin. Seismic stratigraphy is calibrated from industrial wells. We focus on the interactions between the gravity-driven tectonic processes and the sedimentation in the basin. Our seismic interpretation confirms that the formation of the WAB began in the Early Miocene (Aquitanian - Burdigalian). The fast subsidence of the basin floor coeval to massive sedimentation induced the undercompaction of early miocene shales during their deposition. Downslope migration of these fine-grained sediments initiated during the deposition of the Langhian siliciclastics. This gravity-driven system was accompanied by continuous basement subsidence and induced disharmonic deformation in Mid Miocene units (i.e. not related to basement deformation). The development of shale-cored anticlines and thrusts in the deep basin is the result of compressive deformation at the front of the gravity-driven system and lasted for ca. 15 Ma. The compressive front has been re-activated by strong

  12. Magnetotelluric Measurements in the Alboran Sea

    NASA Astrophysics Data System (ADS)

    Evans, R. L.; Jegen, M. D.; Garcia, X. A.; Matsuno, T.; Elsenbeck, J.; Worzewski, T. W.

    2010-12-01

    The PICASSO program aims to understand the tectonic history of the western Mediterranean, between Spain and Morocco, where conflicting models have suggested that the region is either a relict subduction system or a zone of mantle delamination. As part of this program we successfully deployed 12 seafloor MT instruments in water depths greater than 800m in the Alboran sea. We plan to deploy additional instruments in the fall of 2010. An initial analysis of the data shows complex MT response functions with strong distortion due to seafloor topography and coast effect. This coast effect suggests a fairly resistive lithosphere beneath the seafloor, which is confirmed after inspection of the preliminary responses. We will present the data collected thus far, along with preliminary models of the profiles collected.

  13. Modeling the impact of tidal flows on the biological productivity of the Alboran Sea

    NASA Astrophysics Data System (ADS)

    Sánchez-Garrido, José C.; Naranjo, C.; Macías, D.; García-Lafuente, J.; Oguz, T.

    2015-11-01

    The control of phytoplankton production by tidal forcing in the Alboran Sea is investigated with a high-resolution ocean circulation model coupled to an ecosystem model. The aim of the modeling efforts was to elucidate the role of tides in sustaining the high biological productivity of the Alboran Sea, as compared with the rest of the Mediterranean subbasins. It is shown that tidal forcing accounts for an increase of phytoplankton biomass and primary productivity in the basin of about 40% with respect to a nontidal circulation, and about 60% in the western Alboran Sea alone. The tidal dynamics of the Strait of Gibraltar is shown to be the primary factor in determining the enhancement of productivity, pumping nutrients from depth to the photic zone in the Alboran Sea. Model results indicate that the biological implications of the propagating internal tides are small. These results imply that nutrient transports through the Strait of Gibraltar have to be parametrized in ocean models that do not resolve tides in order to properly represent the biochemical budgets of the Alboran Sea.

  14. Evolution of the continental margin of southern Spain and the Alboran Sea

    USGS Publications Warehouse

    Dillon, William P.; Robb, James M.; Greene, H. Gary; Lucena, Juan Carlos

    1980-01-01

    Seismic reflection profiles and magnetic intensity measurements were collected across the southern continental margin of Spain and the Alboran basin between Spain and Africa. Correlation of the distinct seismic stratigraphy observed in the profiles to stratigraphic information obtained from cores at Deep Sea Drilling Project site 121 allows effective dating of tectonic events. The Alboran Sea basin occupies a zone of motion between the African and Iberian lithospheric plates that probably began to form by extension in late Miocene time (Tortonian). At the end of Miocene time (end of Messinian) profiles show that an angular unconformity was cut, and then the strata were block faulted before subsequent deposition. The erosion of the unconformity probably resulted from lowering of Mediterranean sea level by evaporation when the previous channel between the Mediterranean and Atlantic was closed. Continued extension probably caused the block faulting and, eventually the opening of the present channel to the Atlantic through the Strait of Gibraltar and the reflooding of the Mediterranean. Minor tectonic movements at the end of Calabrian time (early Pleistocene) apparently resulted in minor faulting, extensive transgression in southeastern Spain, and major changes in the sedimentary environment of the Alboran basin. Active faulting observed at five locations on seismic profiles seems to form a NNE zone of transcurrent movement across the Alboran Sea. This inferred fault trend is coincident with some bathymetric, magnetic and seismicity trends and colinear with active faults that have been mapped on-shore in Morocco and Spain. The faults were probably caused by stresses related to plate movements, and their direction was modified by inherited fractures in the lithosphere that floors the Alboran Sea.

  15. The Physical Oceanography of the Alboran Sea.

    DTIC Science & Technology

    1987-03-01

    Spanish version is being issued simultaneously by al ititclo lOi : 2re in the % estern Alboran that nearly the Instituto Espa ol de Oceanografia in...Gregorio Parrilla Instituto Espan- ol de Oceanografia Madrid, Spain ToThomas H. Kinder Oceanography Division Ocean Science Directorate Approved for public...in t he w estern .Alboran. ;i it:plcd at 540-rn depth from V1 eerlgclefcso h lk 6I ’,el 0 tC ai ’ oL ! 4 47’ N. ihese instruments I. eto loia efeton h

  16. Mantle structure beneath the Alboran Sea from shear wave splitting

    NASA Astrophysics Data System (ADS)

    Alpert, L. A.; Becker, T. W.; Miller, M. S.; Allam, A. A.

    2011-12-01

    New seismological investigations in the Alboran domain of the western Mediterranean, as part of the PICASSO experiment, support geodynamic models which constrain the mantle structure beneath the Alboran Sea. We evaluate global circulation models in the context of seismic anistropy as inferred from SKS/SKKS splitting observations. Using instantaneous velocity fields from 3-D flow models with variable mantle density based on several tomography and seismicity based models, we calculate the predicted anisotropy, fast polarization direction (FPD), and delay times in order to explain the complex tectonic and geologic history of the Alboran Sea region. Slab rollback, delamination, and convective removal processes have been invoked to explain the synorogenic extension in the Alboran and recently published splitting measurements show north-east trending FPD across the Iberian margin with a rotation to the southeast that follows the curve of the Gibraltar arc, suggested by the authors as supporting west-directed slab rollback. Our new measurements from 39 stations substantiate the measurements in southern Spain, but we find a striking, nearly 90 degree rotation in azimuth and reduced delay times across the High Atlas Mountains in northern Morocco. These splitting patterns define three distinct regions we attempt to predict with our geodynamic models. Here, we test several differently-oriented subduction, slab break-off, and delamination scenarios. Our preliminary results show that density models which include a curved, northeast trending slab predict the east-northeast oriented measurements along the Iberian margin. Imposing a drip structure beneath the Alboran Sea also predicts these orientations. In order to predict the rotation of the FPD we find in Morocco, however, most models require a stiff keel beneath the African craton.

  17. The structure of the Alboran Sea: an interpretation from seismological and geological data

    NASA Astrophysics Data System (ADS)

    López Casado, C.; Sanz de Galdeano, C.; Molina Palacios, S.; Henares Romero, J.

    2001-08-01

    Almost all the earthquakes included in the catalog for the Iberian-Maghrebian area up to 2000 have been used in order to know the structure of the Alboran Sea area after the verification of the aleatory nature of the errors in their spatial localization. A new focal mechanisms catalog has also been used as well as many of the available geological data. During the Mesozoic and till the Oligocene, the Betic-Rif Internal Zone was situated further E, but with the opening of the Algero-Provençal basin in the early Miocene, the Betic-Rif Internal Zone moved to the W. Contemporary, the Alboran Sea was created as the western prolongation of the Algero-Provençal basin. The Betic-Rif Internal Zone overthrused part of the Iberian and African plates, producing the partial sinking of both plates and being responsible of the intermediate seismicity existing in the western sector of the Alboran Sea. The intermediate earthquakes in the Atlas towards the NE and WSW are not related to lithospheric sinking but to significant deep faults limiting a subplate in NW Africa. In the Atlantic, the intermediate earthquakes between the Gorringe sector and Gibraltar are produced in the contact between the Iberian and African plates and by the important faults crossing it. The existence of four very deep earthquakes is related to the previous sinking of the lithosphere originally associated to the domain in which the Betic-Rif Internal Zone was situated.

  18. Role of structural inheritances and major transfer fault-zones in the tectonic history of the Alboran Basin (Western Mediterranean)

    NASA Astrophysics Data System (ADS)

    Comas, Menchu; Crespo-Blanc, Ana; Balanya, Juan Carlos

    2014-05-01

    The geodynamic evolution of the Gibraltar Arc System (GAS), which involves the origin and development of the Alboran back-arc basin, occurred during the Neogene related to the westward moving of the Alboran Domain (the Betic-Rifean hinterland) within a context of NNW-SSE plate-tectonic convergence. In this contribution we document shallow-crustal structures, deformation partitioning, and the different structural domains from the tectonic framework beneath the Alboran Sea. Furthermore, we focus the critical role of inherited crustal structures and major transfer faults within a coherent sequence of Miocene to Recent deformation phases. Early Miocene extensional processes conditioned substantial thinning and the exhumation of the metamorphic Alboran Domain before the opening of the Alboran Basin. Beneath the Alboran Sea, an ENE-SSW directed back-arc extension (from about 16 to 8.5 Ma, late Burdigalian to late Tortonian) affected both the metamorphic basement (the crustal Alboran Domain) and the overlying Miocene sedimentary units. This extension resulted in major low-angle normal faults, and NNW-SSE trending grabens connected by ENE-SSW transtensional transfer-faults, both happening in concomitance with the westward migration (around 200 km) of the Alboran Domain. The geometry of the extensional structures constrains the manner, timing and amount of the coeval crustal thinning. In the late Tortonian (about 8.5 Ma) a dominant N-S directed compressional phase caused inversions of former extensional faults, discrete folding, and strike-slip faulting. This compressional event triggered the spectacular West Alboran shale-diapirism from over-pressured basal units. At the South and Eastern Alboran and at the transition to the Algeria basins, a pervasive period of NW-SE directed compressional deformation (from about 7 Ma onwards) that affected the whole basin is patent. Long lasting compressional conditions since the late Tortonian resulted in a dramatic structural

  19. The Alboran Sea Gyre: Ship, Satellite and Historical Data,

    DTIC Science & Technology

    1979-06-15

    Track of the MARIA PAOLINA G. in the Alboran Sea during 1977 5 (dashed line) and 1978 ( solid line). 2. NOAA 5 images received by the University of...34󈧋 FIG. 1 TRCK OF THE M~IA PAOLINA G. IN THE ALBORN SEA DURING 1977 (dashed line) AND 1978 ( solid line) I r o 2 DATA Figures 2 and 3 are the NOAA 5...In the enlargement of the infrared ( IR ) image it is apparent that the front was encountered at a 450 angle along this track and the average slope may

  20. Structure of the mantle beneath the Alboran Basin from magnetotelluric soundings

    NASA Astrophysics Data System (ADS)

    Garcia, X.; Seillé, H.; Elsenbeck, J.; Evans, R. L.; Jegen, M.; Hölz, Sebastian; Ledo, J.; Lovatini, A.; Marti, A.; Marcuello, A.; Queralt, P.; Ungarelli, C.; Ranero, C. R.

    2015-12-01

    We present results of marine MT acquisition in the Alboran sea that also incorporates previously acquired land MT from southern Spain into our analysis. The marine data show complex MT response functions with strong distortion due to seafloor topography and the coastline, but inclusion of high resolution topography and bathymetry and a seismically defined sediment unit into a 3-D inversion model has allowed us to image the structure in the underlying mantle. The resulting resistivity model is broadly consistent with a geodynamic scenario that includes subduction of an eastward trending plate beneath Gibraltar, which plunges nearly vertically beneath the Alboran. Our model contains three primary features of interest: a resistive body beneath the central Alboran, which extends to a depth of ˜150 km. At this depth, the mantle resistivity decreases to values of ˜100 Ohm-m, slightly higher than those seen in typical asthenosphere at the same depth. This transition suggests a change in slab properties with depth, perhaps reflecting a change in the nature of the seafloor subducted in the past. Two conductive features in our model suggest the presence of fluids released by the subducting slab or a small amount of partial melt in the upper mantle (or both). Of these, the one in the center of the Alboran basin, in the uppermost-mantle (20-30 km depth) beneath Neogene volcanics and west of the termination of the Nekkor Fault, is consistent with geochemical models, which infer highly thinned lithosphere and shallow melting in order to explain the petrology of seafloor volcanics.

  1. Plio-Quaternary tectonic evolution off Al Hoceima, Moroccan Margin of the Alboran Basin.

    NASA Astrophysics Data System (ADS)

    Lafosse, Manfred; d'Acremont, Elia; Rabaute, Alain; Mercier de Lépinay, Bernard; Gorini, Christian; Ammar, Abdellah; Tahayt, Abdelilah

    2015-04-01

    We use data from a compilation of industrial and academic 2D surveys and recent data from MARLBORO-1 (2011), MARLBORO-2 (2012), and SARAS (2012) surveys, which provide high resolution bathymetry and 2D seismic reflexion data. We focus on the key area located south of the Alboran Ridge and the Tofiño Bank, and encompassing the Nekor and Boudinar onshore-offshore basins on the Moroccan side of the Alboran Sea. The Nekor basin is a present pull-apart basin in relay between inherited N050° sinistral strike-slip faults. We consider that these faults define the Principal Displacement Zones (PDZ). The northern PDZ marks the position of the crustal Bokkoya fault, which is connected to the Al-Idrisi Fault Zone en relais with the Adra and Carboneras Fault Zones. On the seabed, right-stepping non-coalescent faults characterize the sinistral kinematics of the northern PDZ and give a general N050° azimuth for the crustal discontinuity. The southern PDZ corresponds to the Nekor fault Zone, a Miocene sinistral strike-slip fault acting as the structural limit of the External Rif. On its eastern edge, the Nekor basin is bounded by the N-S onshore-offshore Trougout fault, connecting the northern and the southern PDZ. The western boundary of the Nekor basin is marked by the Rouadi and El-Hammam Quaternary active N-S normal faults. In the offshore Nekor basin, recent N155° conjugated normal faults affect the seabed. Further east, the Boudinar basin is a Plio-Quaternary uplifted Neogene basin. The northeastern segment of the Nekor fault bounds this basin to the south but is inactive in the Quaternary. Normal east-dipping N150° faults are visible offshore in the continuity of the Boudinar fault. From our perspective, the orientation of major tectonic structures (Bokkoya, Nekor and Carboneras faults and the Alboran ridge) under the present compressive regime due to the Europe/Africa convergence is not compatible with a strike-slip motion. The orientation of the most recent Plio

  2. Numerical Modeling of physical-biological interactions in the Alboran Sea with a submesoscale-resolving model

    NASA Astrophysics Data System (ADS)

    Sánchez Garrido, José Carlos; Naranjo Rosa, Cristina; Sammartino, Simone; Macias Moy, Diego

    2014-05-01

    Ageostrophic motion, such those associated to internal hydraulic jumps, propagating nonlinear internal waves, and submesoscale vortices, are recognized to efficiently supply nutrients to the euphotic zone and thereby fuel biological productivity. These processes are ubiquitous in the Strait of Gibraltar and the adjacent Alboran Sea, and therefore are expected to play an important role in the overall biomass budget of the basin. This has been investigated with a three-dimensional, tidally-forced, high-resolution model [O(1km)] ocean model embedded with an ecosystem NPZD module. We found that tidal mixing in the Strait of Gibraltar enhances remarkably local primary production and drive a net flow of biomass to the Alboran Sea. Additionally, tides also cause an inflow of nutrients confined to the photic layer, which increase further the Alboran Sea biomass through the enhancement of local primary productivity. Subinertial accelerations of the Atlantic flow are also found to temporary enhance biological productivity through the advection of shear vorticity (and submesoscale eddies) from the Strait to the Alboran Sea.

  3. Surface mesoscale pico-nanoplankton patterns at the main fronts of the Alboran Sea

    NASA Astrophysics Data System (ADS)

    León, P.; Blanco, J. M.; Flexas, M. M.; Gomis, D.; Reul, A.; Rodríguez, V.; Jiménez-Gómez, F.; Allen, J. T.; Rodríguez, J.

    2015-03-01

    The mesoscale (10-100 km, days-weeks) plays a key role in the Ocean's ecosystem structure and dynamics. This work compares the pico-nanoplankton patterns observed in the Alboran Sea (Western Mediterranean) during three oceanographic cruises. We analyse its response to different expressions of mesoscale circulation associated with the three major hydrodynamic features in the basin; namely the Northwestern Alboran Front (NWAF, surveyed in OMEGA-1 cruise), the Almeria-Oran Front (AOF, surveyed in OMEGA-2 cruise) and the Western Alboran Gyre (WAG, surveyed in BIOMEGA cruise). The first two surveys were carried out under the most typical quasi-stationary twin gyre conditions of the Alboran Sea, whereas the third cruise was performed after an eastward migration of the WAG. The analysis of pico and nanoplankton populations was carried out using flow cytometry. The patchiness observed in the three cruises indicates an association of phytoplankton peaks with the main frontal structures: abundances were higher in the NWAF/upwelling area in OMEGA-1, at the Mediterranean side of the AOF in OMEGA-2, and at a tongue of recent Atlantic Water west of the WAG in BIOMEGA. However, a more detailed analysis reveals that different factors explain the origin of the phytoplankton biomass in each front/cruise. Mixing processes at the Strait of Gibraltar and the subsequent advection of water properties into the Western Alboran Sea were the mechanisms responsible for the abundances observed in the NWAF. The highest concentrations observed in the AOF were related to the intrusion of Mediterranean Surface Waters to the north of the front. During the migrating WAG the phytoplankton distribution was influenced by the formation of a new gyre. The relation between phytoplankton and mesoscale dynamics is further explored in terms of vertical velocity diagnosis. In all cases, intense vertical motion is negatively correlated with the abundance of phytoplankton populations. This resulted from the

  4. Deep Water Mass Circulation in the Western Alboran Basin: Measurements in July and September 1980 (Alboran I Experiment),

    DTIC Science & Technology

    1984-07-15

    that area and that it accelerates towards Gibraltar. ClO and STD data showed an upward bending of isolines towards the Moroccan continental slope...currentmeters were acoustically tracked in the southwestern part of the Alboran Sea to measure the deep currents near the Moroccan continental slope...the slope, as predicted P y Bryden and Stomel. by deploying free-floating verticalI currentmeters (VCN%) near the Moroccan continental slope. Third

  5. New evidence of delamination in the Western Alboran Sea. Geodynamic evolution of the Alboran domain and its margins

    NASA Astrophysics Data System (ADS)

    Timoulali, Youssef; Djellit, Hamou; Hahou, Youssef; Jabour, Nacer; Merrouch, Redouane

    2014-07-01

    The presence of continuous upper crustal blocks between the Iberian Betics and Moroccan Rif in the western and middle Alboran Sea, detected with tomography, can add new information about the lithosphere structure and geodynamic evolution in this region. A large volume of seismic data (P and S wave arrival times) has been collected for the period between 1 December 1988 and 31 December 2008 by 57 stations located in northern Morocco (National Institute of Geophysics, CNRST, Rabat), southern Portugal (Instituto de Meteorologia, Lisbon) and Spain (Instituto Geografico National, Madrid) and used to investigate the lithosphere in the western Alboran Sea region. We use a linearized inversion procedure comprising two steps: (1) finding the minimal 1-D model and simultaneous relocation of hypocenters and (2) determination of local velocity structure using linearized inversion. The model parameterization in this method assumes a continuous velocity field. The resolution tests indicate that the calculated images give near true structure imaged at 5 km depth for the Tanger peninsula, the Alhoceima region and southern Spain. At 15, 30 and 45 km depth we observe a near true structure imaged in northern Morocco, and southern Spain. At 60 and 100 km, southern Spain and the SW region of the Alboran Sea give a near true structure. The resulting tomographic image shows the presence of two upper crustal bodies (velocity 6.5 km/s) at 5-10 km depth between the Betics, Rif, western and central Alboran Sea. Low velocities at the base of these two bodies favor the presence of melt. This new evidence proves that the Tethysian ocean upper crust was not totally collapsed or broken down during the late Oligocene-early Miocene. These two blocks of upper crust were initially one block. The geodynamic process in the eastern of the Mediterranean is driven by slab rollback. The delamination process of the lithospheric mantle terminates with the proposed slab rollback in the western part of the

  6. Deep Water Mass Circulation in the Alboran Basin: Measurements - August to November 1983. Alboran III.

    DTIC Science & Technology

    1988-02-01

    ern Alboran displayed slow and variable current speed. Floats deployed on the Moroccan continental slope moved swiftly along the slope towards...Gibraltar with accelerating speed, and then passed through the Strait of Gibraltar i~t’into the Atlantic. tUpward bading of isolines across the Moroccan ...circulation o Igeostrophic current o Levantine o Mediterranean o modelling o moroccan continental slope o remote sensing o sound propagation o Spanish

  7. Seismicity and active tectonics in the Alboran Sea, Western Mediterranean: Constraints from an offshore-onshore seismological network and swath bathymetry data

    NASA Astrophysics Data System (ADS)

    Grevemeyer, Ingo; Gràcia, Eulàlia; Villaseñor, Antonio; Leuchters, Wiebke; Watts, Anthony B.

    2015-12-01

    Seismicity and tectonic structure of the Alboran Sea were derived from a large amphibious seismological network deployed in the offshore basins and onshore in Spain and Morocco, an area where the convergence between the African and Eurasian plates causes distributed deformation. Crustal structure derived from local earthquake data suggests that the Alboran Sea is underlain by thinned continental crust with a mean thickness of about 20 km. During the 5 months of offshore network operation, a total of 229 local earthquakes were located within the Alboran Sea and neighboring areas. Earthquakes were generally crustal events, and in the offshore domain, most of them occurred at crustal levels of 2 to 15 km depth. Earthquakes in the Alboran Sea are poorly related to large-scale tectonic features and form a 20 to 40 km wide NNE-SSW trending belt of seismicity between Adra (Spain) and Al Hoceima (Morocco), supporting the case for a major left-lateral shear zone across the Alboran Sea. Such a shear zone is in accord with high-resolution bathymetric data and seismic reflection imaging, indicating a number of small active fault zones, some of which offset the seafloor, rather than supporting a well-defined discrete plate boundary fault. Moreover, a number of large faults known to be active as evidenced from bathymetry, seismic reflection, and paleoseismic data such as the Yusuf and Carboneras faults were seismically inactive. Earthquakes below the Western Alboran Basin occurred at 70 to 110 km depth and hence reflected intermediate depth seismicity related to subducted lithosphere.

  8. The depiction of Alboran Sea Gyre during Donde Va? using remote sensing and conventional data

    NASA Technical Reports Server (NTRS)

    Laviolette, P. E.

    1984-01-01

    Experienced oceanographic investigators have come to realize that remote sensing techniques are most successful when applied as part of programs of integrated measurements aimed at solving specific oceanographic problems. A good example of such integration occurred during the multi-platform international experiment, Donde Va? in the Alboran Sea during the period June through October, 1982. The objective of Donde Va? was to derive the interrelationship of the Atlantic waters entering the Mediterranean Sea and the Alboran Sea Gyre. The experimental plan conceived solely with this objective in mind consisted of a variety of remote sensing and conventional platforms: three ships, three aircraft, five current moorings, two satellites and a specialized beach radar (CODAR). Integrated analyses of these multiple-data sets are still being conducted. However, the initial results show detailed structure of the incoming Atlantic jet and Alboran Sea Gyre that would not have been possible by conventional means.

  9. Identification of T-Waves in the Alboran Sea

    NASA Astrophysics Data System (ADS)

    Carmona, Enrique; Almendros, Javier; Alguacil, Gerardo; Soto, Juan Ignacio; Luzón, Francisco; Ibáñez, Jesús M.

    2015-11-01

    Analyses of seismograms from ~1,100 north-Moroccan earthquakes recorded at stations of the Red Sísmica de Andalucía (Southern Spain) reveal the systematic presence of late phases embedded in the earthquake codas. These phases have distinctive frequency contents, similar to the P and S spectra and quite different to the frequency contents of the earthquake codas. They are best detected at near-shore stations. Their amplitudes decay significantly with distance to the shoreline. The delays with respect to the P-wave onsets of the preceding earthquakes are consistently around 85 s. Late phases are only detected for earthquakes located in a small region of about 100 × 60 km centered at 35.4°N, 4.0°W near the northern coast of Morocco. Several hypotheses could, in principle, explain the presence of these late phases in the seismograms, for example, the occurrence of low-energy aftershocks, efficient wave reflections, or Rayleigh waves generated along the source-station paths. However, we conclude that the most-likely origin of these phases corresponds to the incidence of T-waves (generated by conversion from elastic to acoustic energy in the north-Moroccan coast) in the southern coast of the Iberian Peninsula. T-waves are thought to be generated by energy trapping in low-velocity channels along long oceanic paths; in this case, we demonstrate that they can be produced in much shorter paths as well. Although T-waves have been already documented in other areas of the Mediterranean Sea, this is the first time that they have been identified in the Alboran Sea.

  10. Crossing the Iberian Plate from the Bay of Biscay to the Alboran Sea: a lithospheric geotransect

    NASA Astrophysics Data System (ADS)

    Carballo, Alberto; Fernandez, Manel; Torne, Montserrat; Jiménez-Munt, Ivone; Vergés, Jaume; Pedreira, David; Díaz, Jordi; Villaseñor, Antonio

    2014-05-01

    A ~1000-km-long lithospheric transect running from the North-Iberian Margin to the Neogene Alboran Basin (W- Mediterranean) is investigated. The main goal is to image the lateral changes in the crustal and lithospheric structure occurring in: i) the North-Iberian margin, whose deformation in Alpine times gave rise to the uplift of the Cantabrian Mountains related to incipient subduction; ii) the Spanish Meseta, characterized by the presence of Cenozoic basins on top of a Variscan basement with weak Alpine deformation in the Spanish Central System and localized Neogene-Quaternary deep volcanism; and iii) the Betic-Alboran system related to the roll-back of the Ligurian-Tethyan domain. The modeling approach based on the LitMod package combines potential fields, elevation, thermal, seismic and petrological data under a self-consistent scheme. The crustal structure is mainly constrained by active and passive seismic experiments whereas the upper mantle is constrained by tomography models. The results highlight the lateral variations in the topography of the lithosphere-asthenosphere boundary (LAB), suggesting a strong lithospheric mantle strain below the Cantabrian and Betic mountain belts. The LAB depth ranges from 160 km beneath the Cantabrian Mountains to 110-90 km beneath Iberia Meseta deepenly again to values of 190 km beneath Betic Mountain. The Spanish Central System, with elevations higher than 1400 m, has no noticeable signature on the LAB depth. We have considered three lithospheric mantle compositions: a predominantly average Phanerozoic in the continental mainland, and two more fertile PUM (primitive upper mantle) compositions in the oceanic domains of Cantabrian and Mediterranean seas, and in the Calatrava volcanic field. These compositional differences allowed us to reproduce the main trends of the geophysical observables as well as the inferred P-, Pn- and S-wave seismic velocities from tomography models and seismic experiments available in the study

  11. Well log interpretation and seismic character of the cenozoic sequence in the northern Alboran Sea

    NASA Astrophysics Data System (ADS)

    Jurado, M. J.; Comas, M. C.

    1992-06-01

    Seismic stratigraphic and main lithological features of the sedimentary cover overlying the basement of the Alboran Sea were established via the analysis of commercial multichannel seismic surveys, geophysical well logs, and well data. Six seismic stratigraphics units (VI to I), bounded by unconformities, form the marine sediments that range in age from early Miocene to Quaternary. They are dated by extrapolation of commercial drilling results from the northern Alboran Sea. Volcanic activity is recorded within sedimentary sequences of units V to II. Undercompaction features are detected in the two basal units.

  12. Controls of picophytoplankton abundance and composition in a highly dynamic marine system, the Northern Alboran Sea (Western Mediterranean)

    NASA Astrophysics Data System (ADS)

    Amorim, Ana L.; León, Pablo; Mercado, Jesús M.; Cortés, Dolores; Gómez, Francisco; Putzeys, Sebastien; Salles, Soluna; Yebra, Lidia

    2016-06-01

    The Alboran Sea is a highly dynamic basin which exhibits a high spatio-temporal variability of hydrographic structures (e.g. fronts, gyres, coastal upwellings). This work compares the abundance and composition of picophytoplankton observed across the northern Alboran Sea among eleven cruises between 2008 and 2012 using flow cytometry. We evaluate the seasonal and longitudinal variability of picophytoplankton on the basis of the circulation regimes at a regional scale and explore the presence of cyanobacteria ecotypes in the basin. The maximal abundances obtained for Prochlorococcus, Synechococcus and picoeukaryotes (12.7 × 104, 13.9 × 104 and 8.6 × 104 cells mL- 1 respectively) were consistent with those reported for other adjacent marine areas. Seasonal changes in the abundance of the three picophytoplankton groups were highly significant although they did not match the patterns described for other coastal waters. Higher abundances of Prochlorococcus were obtained in autumn-winter while Synechococcus and picoeukaryotes exhibited a different seasonal abundance pattern depending on the sector (e.g. Synechococcus showed higher abundance in summer in the west sector and during winter in the eastern study area). Additionally, conspicuous longitudinal gradients were observed for Prochlorococcus and Synechococcus, with Prochlorococcus decreasing from west to east and Synechococcus following the opposite pattern. The analysis of environmental variables (i.e. temperature, salinity and inorganic nutrients) and cell abundances indicates that Prochlorococcus preferred high salinity and nitrate to phosphate ratio. On the contrary, temperature did not seem to play a role in Prochlorococcus distribution as it was numerically important during the whole seasonal cycle. Variability in Synechococcus abundance could not be explained by changes in any environmental variable suggesting that different ecotypes were sampled during the surveys. In particular, our data would indicate

  13. Fueling plankton production by a meandering frontal jet: a case study for the Alboran Sea (Western Mediterranean).

    PubMed

    Oguz, Temel; Macias, Diego; Garcia-Lafuente, Jesus; Pascual, Ananda; Tintore, Joaquin

    2014-01-01

    A three dimensional biophysical model was employed to illustrate the biological impacts of a meandering frontal jet, in terms of efficiency and persistency of the autotrophic frontal production, in marginal and semi-enclosed seas. We used the Alboran Sea of the Western Mediterranean as a case study. Here, a frontal jet with a width of 15-20 km, characterized by the relatively low density Atlantic water mass, flows eastward within the upper 100 m as a marked meandering current around the western and the eastern anticyclonic gyres prior to its attachment to the North African shelf/slope topography of the Algerian basin. Its inherent nonlinearity leads to the development of a strong ageostrophic cross-frontal circulation that supplies nutrients into the nutrient-starved euphotic layer and stimulates phytoplankton growth along the jet. Biological production is larger in the western part of the basin and decreases eastwards with the gradual weakening of the jet. The higher production at the subsurface levels suggests that the Alboran Sea is likely more productive than predicted by the satellite chlorophyll data. The Mediterranean water mass away from the jet and the interiors of the western and eastern anticyclonic gyres remain unproductive.

  14. Fueling Plankton Production by a Meandering Frontal Jet: A Case Study for the Alboran Sea (Western Mediterranean)

    PubMed Central

    Oguz, Temel; Macias, Diego; Garcia-Lafuente, Jesus; Pascual, Ananda; Tintore, Joaquin

    2014-01-01

    A three dimensional biophysical model was employed to illustrate the biological impacts of a meandering frontal jet, in terms of efficiency and persistency of the autotrophic frontal production, in marginal and semi-enclosed seas. We used the Alboran Sea of the Western Mediterranean as a case study. Here, a frontal jet with a width of 15–20 km, characterized by the relatively low density Atlantic water mass, flows eastward within the upper 100 m as a marked meandering current around the western and the eastern anticyclonic gyres prior to its attachment to the North African shelf/slope topography of the Algerian basin. Its inherent nonlinearity leads to the development of a strong ageostrophic cross-frontal circulation that supplies nutrients into the nutrient-starved euphotic layer and stimulates phytoplankton growth along the jet. Biological production is larger in the western part of the basin and decreases eastwards with the gradual weakening of the jet. The higher production at the subsurface levels suggests that the Alboran Sea is likely more productive than predicted by the satellite chlorophyll data. The Mediterranean water mass away from the jet and the interiors of the western and eastern anticyclonic gyres remain unproductive. PMID:25372789

  15. Scenarios for earthquake-generated tsunamis on a complex tectonic area of diffuse deformation and low velocity: The Alboran Sea, Western Mediterranean

    USGS Publications Warehouse

    Alvarez-Gomez, J. A.; Aniel-Quiroga, I.; Gonzalez, M.; Olabarrieta, M.; Carreno, E.

    2011-01-01

    The tsunami impact on the Spanish and North African coasts of the Alboran Sea generated by several reliable seismic tsunamigenic sources in this area was modeled. The tectonic setting is complex and a study of the potential sources from geological data is basic to obtain probable source characteristics. The tectonic structures considered in this study as potentially tsunamigenic are: the Alboran Ridge associated structures, the Carboneras Fault Zone and the Yusuf Fault Zone. We characterized 12 probable tsunamigenic seismic sources in the Alboran Basin based on the results of recent oceanographical studies. The strain rate in the area is low and therefore its seismicity is moderate and cannot be used to infer characteristics of the major seismic sources. These sources have been used as input for the numerical simulation of the wave propagation, based on the solution of the nonlinear shallow water equations through a finite-difference technique. We calculated the Maximum Wave Elevations, and Tsunami Travel Times using the numerical simulations. The results are shown as maps and profiles along the Spanish and African coasts. The sources associated with the Alboran Ridge show the maximum potential to generate damaging tsunamis, with maximum wave elevations in front of the coast exceeding 1.5. m. The Carboneras and Yusuf faults are not capable of generating disastrous tsunamis on their own, although their proximity to the coast could trigger landslides and associated sea disturbances. The areas which are more exposed to the impact of tsunamis generated in the Alboran Sea are the Spanish coast between Malaga and Adra, and the African coast between Alhoceima and Melilla. ?? 2011 Elsevier B.V.

  16. Role of the Alboran Sea volcanic arc choking the Mediterranean to the Messinian salinity crisis and foundering biota diversification in North Africa and Southeast Iberia

    NASA Astrophysics Data System (ADS)

    Booth-Rea, Guillermo; Ranero, Cesar R.; Grevemer, Ingo

    2016-04-01

    The Mediterranean Sea desiccated ~5.96 million years ago when it became isolated from the world oceans during the Messinian salinity crisis. This event permitted the exchange of terrestrial biota between Africa and Iberia contributing to the present rich biodiversity of the Mediterranean region. The cause chocking the Mediterranean has been proposed to be tectonic uplift and dynamic topography but the driving mechanism still remains debated. We present a new wide-angle seismic profile that provides a detailed image of the thickness and seismic velocity distribution of the crust in the eastern Alboran basin. The velocity model shows a characteristic structure of a subduction-related volcanic arc with a high-velocity lower crust and a 16-18 km total-thickness igneous crust that magmatic accreted mostly between ~10-6 Ma across the eastern Alboran basin. Estimation of the isostatically corrected depth of the arc crust taking into account the original thermal structure and sediment-loading subsidence since 6 Ma places a large area of the eastern Alboran basin above sea level at the time. This estimation is supported by geophysical data showing subaereal erosional unconformities for that time. This model may explain several up-to-now-disputed features of the Messinian salinity crisis, including: the progressive isolation of the Mediterranean since 7.1 Ma with the disappearance of open marine taxa, the existence of evaporites mostly to the east of the volcanic arc, the evidence that the Gibraltar straits were not a land bridge offered by continuous Messinian open marine sediments at ODP site 976 in the western Alboran basin, the importance of southeastern Iberia and North Africa as centres of biota diversification since before the salinity crisis, and patterns of speciation irradiating from SE Iberia and the eastern Rif in some taxons.

  17. Origin of lipid biomarkers in mud volcanoes from the Alboran Sea, western Mediterranean

    NASA Astrophysics Data System (ADS)

    López-Rodríguez, C.; Stadnitskaia, A.; De Lange, G. J.; Martínez-Ruíz, F.; Comas, M.

    2014-06-01

    Mud volcanoes (MVs) are the most prominent indicators of active methane/hydrocarbon venting at the seafloor on both passive and active continental margins. Their occurrence in the western Mediterranean is patent at the West Alboran Basin, where numerous MVs develop overlaying a major sedimentary depocentre containing overpressured shales. Although some of these MVs have been studied, the detailed biogeochemistry of expelled mud so far has not been examined in detail. This work provides the first results on the composition and origin of organic matter, anaerobic oxidation of methane (AOM) processes and general characteristics on MV dynamics using lipid biomarkers as the main tool. Lipid biomarker analysis was performed on MV expelled material (mud breccias) and interbedded hemipelagic sediments from Perejil, Kalinin and Schneider's Heart MVs located in the northwest margin of the Alboran Sea. The n alkane distributions and n alkane-derived indices (CPI and ACL), in combination with the epimerization degree of hopanes (22S/(22S+22R)) indicate that all studied mud breccia have a similar biomarker composition consisting of mainly thermally immature organic matter with an admixture of petroleum-derived compounds. This concordant composition indicates that common source strata must feed all three studied MVs. The past or present AOM activity was established using lipid biomarkers specific for anaerobic methanotrophic archaea (irregular isoprenoids and dialkyl glycerol diethers) and the depleted carbon isotope composition (δ13C) of crocetane/phytane. The presence of these lipid biomarkers, together with the low amounts of detected glycerol dialkyl glycerol tetraethers, is consistent with the dominance of anaerobic methanotrophs of the ANME-2 over ANME-1, at least in mud breccia from Perejil MVs. In contrast, the scarce presence or lack of these AOM-related lipid biomarkers in sediments from Kalinin and Schneider's Heart MVs, suggests that no recent active methane seepage

  18. The Alboran Sea mesoscale in a long term high resolution simulation: Statistical analysis

    NASA Astrophysics Data System (ADS)

    Peliz, Alvaro; Boutov, Dmitri; Teles-Machado, Ana

    2013-12-01

    We analyze the Alboran Sea mesoscale variability in a 2-decade high resolution (2 km) simulation. The circulation modes and eddies are described from a statistical perspective. The double-gyre quasi-steady state is confirmed as the most common circulation mode in the Alboran Sea (48% of the time), followed by single-gyre mode in about 24% of the situations. These persistent modes are compared in terms of structure, frequency of occurrence and seasonality, energetics, and their links to inflow variability and wind forcing. The double-gyre state is the most stable situation with higher kinetic and potential energy and lower eddy kinetic energy and seems to be limited by a critical value of the Rossby radius (∼12 km). The transitions between the quasi-steady states are studied and typified with a particular focus on the Western Alboran Gyre migration which stands out as the major contributor for flow transitions. A typical sequence of flow types and transients is proposed: The double-gyre is usually canceled after a migration event occurring in late summer or autumn. The Western Alboran Gyre is not immediately replaced by a new born anticyclone. Instead, there is a cycle of migration-merging events with the Eastern Alboran Gyre which eventually force the latter to move westward and form a single-gyre situation. The generation of a second Eastern Alboran Gyre in spring-early summer sets the beginning of a new double-gyre stable period. An analysis of coherent mesoscale eddies is conducted and their statistics, sites and processes of generation are described. Cyclones (anticyclones) mean radius are in the range of ∼12 km (∼15 km), they are much more frequent in winter time and cyclones significantly outnumber the anticyclones. The link of mesoscale processes and transients (in particular of migrations) with the inflow is analyzed, and no clear relationship of transient events with inflow magnitude is disclosed. On the other hand, the large majority of transitions

  19. Atmospheric forcing and Sea Surface Temperature response in the Gulf of Cadiz-Alboran Sea system in a 20 years simulation

    NASA Astrophysics Data System (ADS)

    Boutov, D.; Peliz, A.

    2012-04-01

    In the frame of MedEX ("Inter-basin exchange in the changing Mediterranean Sea") Project a 20 years (1989-2008) simulation at 2km resolution covering Gulf of Cadiz and Alboran Sea, forced by 9 km winds (WRF downscaling of ERA-Interim reanalysis), is analyzed and compared with observations. Statistical methods, EOF techniques and two harmonic (including annual and semi-annual frequencies) data fit were performed for the analysis. Modeled SST fields are also compared with long-term (1996-2008) in-situ buoy observations provided by Puertos del Estado (Spain) and satellite derived Pathfinder SST database. Model SSTs generally follow observations data at annual and inter-annual scales with a global error not exceeding 0.17°C (model warmer than SST). No significant warming tendency was observed in both basins during the 20 years and the Interanual variability dominates, with the series showing a cooling period from 1991 to 1993 followed by a warming period started from 1994. In particular we show that SST cooling observed in the early 1990's in the Gulf of Cadiz - Alboran system is associated with the 1991 catastrophic eruption of Pinatubo volcano (Philippines).

  20. From the North-Iberian Margin to the Alboran Basin: A lithosphere geo-transect across the Iberian Plate

    NASA Astrophysics Data System (ADS)

    Carballo, A.; Fernandez, M.; Jiménez-Munt, I.; Torne, M.; Vergés, J.; Melchiorre, M.; Pedreira, D.; Afonso, J. C.; Garcia-Castellanos, D.; Díaz, J.; Villaseñor, A.; Pulgar, J. A.; Quintana, L.

    2015-11-01

    A ~ 1000-km-long lithospheric transect running from the North-Iberian Margin to the Alboran Basin (W-Mediterranean) is investigated. The main goal is to image the changes in the crustal and upper mantle structure occurring in: i) the North-Iberian margin, whose deformation in Alpine times gave rise to the uplift of the Cantabrian Mountains related to Iberia-Eurasia incipient subduction; ii) the Spanish Meseta, characterized by the presence of Cenozoic basins on top of a Variscan basement with weak Alpine deformation in the Central System, and localized Neogene-Quaternary deep volcanism; and iii) the Betic-Alboran system related to Africa-Iberia collision and the roll-back of the Ligurian-Tethyan domain. The modeling approach, combines potential fields, elevation, thermal, seismic, and petrological data under a self-consistent scheme. The crustal structure is mainly constrained by seismic data whereas the upper mantle is constrained by tomographic models. The results highlight the lateral variations in the topography of the lithosphere-asthenosphere boundary (LAB), suggesting a strong lithospheric mantle strain below the Cantabrian and Betic mountain belts. The LAB depth ranges from 180 km beneath the Cantabrian Mountains to 135-110 km beneath Iberia Meseta deepening again to values of 160 km beneath the Betic Cordillera. The Central System, with a mean elevation of 1300 m, has a negligible signature on the LAB depth. We have considered four lithospheric mantle compositions: a predominantly average Phanerozoic in the continental mainland, two more fertile compositions in the Alboran Sea and in the Calatrava Volcanic Province, and a hydrated uppermost mantle in the North-Iberian Margin. These compositional differences allowed us to reproduce the main trends of the geophysical observables as well as the inferred P- and S-wave seismic velocities from tomography models and seismic experiments available in the study transect. The high mean topography of Iberia can be

  1. XRF geochemistry of Maya mud volcano (SAGAS 08 cruise Alboran Sea)

    NASA Astrophysics Data System (ADS)

    Rodríguez Germade, Isabel; Fátima López Rodríguez, Carmen; Rubio, Belén.; Comas, Menchu; Rey, Daniel; Vilas, Federico; Álvarez, Paula

    2010-05-01

    Mud ascent as the result of active diapirism and mud volcanoes on the seafloor are common features in the Alboran Sea. It is thought that these have been developed during a compressional tectonic setting that produced folding and wrench tectonics throughout the basin. During the TTR 17 cruise of the R/V Professor Logachev (2008), several new and previously discovered mud volcanoes and structure mounds were sampled in the southwest sector of Alboran Basin. Most of the investigated mud volcanic deposits, such as Melilla and Maya structures, were covered by a thick drape of hemipelagic mud, suggesting that volcanoes are currently inactive. The aim of this paper is to demonstrate the ability of high-resolution XRF core scanning based geochemical depth profiles to discriminate between mud volcanoes, mounds and hemipelagic sediments, and also to show high resolution geochemical profiles of the core 419G from Maya mud volcano. For our purpose U-channels were subsampled from the centre of half-split gravity cores. High-resolution XRF data of 28 major and trace elements were acquired for each core on an Itrax Core Scanner at the University of Vigo by using Mo and Cr lamps. The acquisition was performed with in this case a 300 µm resolution and provided about 100,000 data point (i.e. XRF spectra), for each meter of core. We used carbon dating to estimate the age of the Maya mud volcano sediments. We also used a scanning electron microscope to do microanalysis and to study mineralogy. The results show that down-core high resolution XRF scanner based geochemical profiles represented a good and quick screening tool for identifying authigenic methane-related carbonate-rich layers that may represent paleo-indicators for ancient methane seepage. Sedimentary Sr/Ca and Mg/Ca ratios have also been explored to infer the presence of authigenic aragonite (Sr-rich) and Mg-rich carbonate phases (high-Mg calcite, dolomite). The coexistence of methane anaerobic oxidation process and

  2. The Climatological Annual Cycle of Satellite-derived Phytoplankton Pigments in the Alboran Sea: A Physical Interpretation

    NASA Technical Reports Server (NTRS)

    Garcia-Gorriz, E.; Carr, M. E.

    1998-01-01

    The circulation and upwelling processes (coastal and gyre-induced) that control the phytoplankton distribution in the Alboran sea are examined by analyzing monthly climatological patterns of Coastal Zone Color Scanner (CZCS) pigment concentrations, sea surface temperatures, winds, and seasonal geostrophic fields.

  3. Geotechnical properties and preliminary assessment of sediment stability on the continental slope of the northwestern Alboran Sea

    USGS Publications Warehouse

    Baraza, J.; Ercilla, G.; Lee, H.J.

    1992-01-01

    Laboratory analysis of core samples from the western Alboran Sea slope reveal a large variability in texture and geotechnical properties. Stability analysis suggests that the sediment is stable under static gravitational loading but potentially unstable under seismic loading. Slope failures may occur if horizontal ground accelerations greater than 0.16 g are seismically induced. The, Alboran Sea is an active region, on which earthquakes inducing accelerations big enough to exceed the shear strength of the soft soil may occur. Test results contrast with the apparent stability deduced from seismic profiles. ?? 1992 Springer-Verlag New York Inc.

  4. High resolution simulations and glider observations in the eastern Alboran Sea (Mediterranean Sea): implications for vertical velocity estimates

    NASA Astrophysics Data System (ADS)

    Mason, Evan; Pascual, Ananda; McWilliams, James C.

    2013-04-01

    The transition region between the Alboran Sea and the Algerian sub-basin to the east is characterised by strong fronts and mesoscale anticyclonic eddies, and has correspondingly raised levels of eddy kinetic energy. The transient Almería-Orán front separates Atlantic Water (AW) flowing into the Mediterranean Sea, and recirculating Mediterranean Water (MW) that intrudes southwestward along the Spanish coast. Quasi-geostrophic vertical motions estimated from a combination of altimetry and glider observations by Ruiz et al. (2009) are of the order of ±1 m day-1, although higher velocities (up to 20-25 m day-1) can be assumed for smaller scale structures embedded within the front, as revealed by chlorophyll data and pointed out by Tintoré et al. (1991). In order to further investigate the vertical velocity spectrum we present results from a high resolution nested modelling study that focuses on the Almería-Orán front. The model is the primitive equation Regional Ocean Modeling System (ROMS). We identify the conditions under which the front forms using a 5 km resolution Mediterranean climatological solution that is run for 15 years. A series of one-way nested simulations then lead to a sub-km solution that permits a high resolution characterisation of the 3D structure of the front. These are then compared with glider observations collected during July 2009. Further, this work will support a high-resolution multi-platform experiment to sample the Almería-Orán front that is to take place in Spring 2014 as part of the European project FP7 PERSEUS.

  5. Atmospheric patterns driving Holocene productivity in the Alboran Sea (Western Mediterranean): a multiproxy approach.

    NASA Astrophysics Data System (ADS)

    Ausin, Blanca; Flores, Jose-Abel; Sierro, Francisco Javier; Cacho, Isabel; Hernández-Almeida, Iván; Martrat, Belén; Grimalt, Joan

    2014-05-01

    This study is aimed to reconstruct productivity during the Holocene in the Western Mediterranean as well as to investigate what processes account for its short-term variability. Fossil coccolithophore assemblages have been studied along with Mg/Ca and Uk'37-estimated Sea Surface Temperature (SST) and other paleoenvironmental proxies. The study site is located in a semi-permanent area of upwelling in the Alboran Sea. This productive cell is of special interest since is closely related to local hydrological dynamics driven by the entering Atlantic Jet (AJ). The onset of this productive cell is suggested at 7.7 ka cal. B.P. and linked to the establishment of the anticyclonic gyres. From 7.7 ka cal. BP to present, the N ratio and accumulation rate of Florisphaera profunda show successive upwelling and stratification events. This alternation is simultaneous to changes in the Western Mediterranean Deep Water (WMDW) formation rate in the Gulf of Lions [Frigola et al., 2007], along with changes in Mg/Ca-estimated SST, relative abundance of reworked nannoliths, pollen grains record [Fletcher et al., 2012] and n-hexacosan-1-ol index. Two scenarios are proposed to explain short-term climatic and oceanographic variability: [1] Wetter climate and weaker north-westerlies blowing over the Gulf of Lions trigger a slackening of the WMDW formation. Consequently, a minor AJ inflows the Alboran Sea leading to less vertical mixing and a deepening of the nutricline and hence, long-term stratification events. [2] Arid climate and stronger north-westerlies enable WMDW reinforcement. In turn, increased AJ triggers vertical mixing and nutricline shoaling, and therefore, productive periods. Finally, changes in atmospheric patterns (e.g. the winter North Atlantic Oscillation; [Olsen et al., 2012]) prove to be useful in explaining the WMDW formation in the Gulf of Lions and associated short-term productivity variations in the Alboran Sea. References Fletcher, W. J., M. Debret, and M. F

  6. Shewanella woodyi sp. nov., an exclusively respiratory luminous bacterium isolated from the Alboran Sea.

    PubMed

    Makemson, J C; Fulayfil, N R; Landry, W; Van Ert, L M; Wimpee, C F; Widder, E A; Case, J F

    1997-10-01

    Thirty-four strains of nonfermentative, respiratory, luminous bacteria were isolated from samples of squid ink and seawater from depths of 200 to 300 m in the Alboran Sea. Although these strains had a few properties similar to properties of Shewanella (Alteromonas) hanedai, they did not cluster phenotypically with any previously described bacterium. The nucleotide sequence of a 740-bp segment of luxA was not homologous with other known luxA sequences but clustered with the luxA sequences of Shewanella hanedai, Vibrio logei, Vibrio fischeri, and Photobacterium species. The 16S RNA gene from two strains was sequenced and was found to be most closely related to the S. hanedai 16S RNA gene. Based on the differences observed, we describe the new isolates as members of new species, Shewanella woodyi sp. nov. Strain ATCC 51908 (= MS32) is the type strain of this new species.

  7. Turbulent mixing in the eddy transport of Western Mediterranean Intermediate Water to the Alboran Sea

    NASA Astrophysics Data System (ADS)

    Forryan, A.; Allen, J. T.; Edhouse, E.; Silburn, B.; Reeve, K.; Tesi, E.

    2012-09-01

    Western Mediterranean Intermediate Water (WIW) is formed in winter in the North-Western Mediterranean. WIW, identifiable as a distinct temperature minimum layer between Atlantic-Mediterranean Interface waters and the denser Levantine Intermediate Water, is carried down the east coast of Spain in anticyclonic mode water eddies, or “weddies” eventually reaching the Alboran sea. A previous detailed analysis of a weddy in the vicinity of the Almeria-Oran front indicated that it could have accounted for 10% of a winter's production of WIW, but this analysis was unable to consider turbulent dissipation. In this study we present microstructure measurements across a similar observation of WIW in the vicinity of the Almeria-Oran front and show that this figure could be conservative by 15-50% due to the turbulent dissipation associated with a weddy.

  8. Architectures of the Moroccan continental shelf of the Alboran Sea: insights from high-resolution bathymetry and seismic data.

    NASA Astrophysics Data System (ADS)

    Lafosse, Manfred; Gorini, Christian; Leroy, Pascal; d'Acremont, Elia; Rabineau, Marina; Ercilla, Gemma; Alonso, Belén; Ammar, Abdellah

    2016-04-01

    The MARLBORO and the SARAS oceanographic surveys have explored the continental shelf in the vicinity of the transtensive Nekor basin (South Alboran Sea, Western Mediterranean) and over three submarine highs located at several tens of kilometers from the shelf. Those surveys have produced high-resolution (≤29m²/pixel) bathymetry maps. Simultaneously, seismic SPARKER and TOPAS profiles were recorded. To quantify and understand Quaternary vertical motions of this tectonically active area, we searched for morphological and sedimentary paleobathymetric or paleo-elevations markers. Shelf-edge wedges associated marine terraces and paleo-shorelines have been identified on the bathymetry and on seismic cross-sections. These features reflect the trends of long term accommodation variations. Along the Moroccan continental shelf the lateral changes of shelf-edges geometries and the spatial distribution of marine landforms (sedimentary marine terraces, sediment wave fields, marine incisions) reflect the interaction between sea level changes and spatial variations of subsidence rates. Positions of paleo-shorelines identified in the studied area have been correlated with the relative sea-level curve (Rohling et al., 2014). Several still stands or slow stands periods have been recognized between -130-125m, -100-110m and -85-80m. The astronomical forcing controls the architecture of Mediterranean continental shelves. Marine landforms distribution also reveals the way sea level changed since the LGM. The comparison with observations on other western Mediterranean margins (e.g. the Gulf of Lion, the Ionian-Calabrian shelf) allowed a first order access to vertical motion rates.

  9. Processes driving submarine landslide geohazards in Alboran Sea: A complex interaction between fluid pressure, contouritic sedimentation and seismicity

    NASA Astrophysics Data System (ADS)

    Lafosse, M.; Gorini, C.

    2015-12-01

    The active Eurasia-Nubia plate boundary runs across the Alboran Sea in the Western Mediterranean Sea. Earthquakes of magnitude Mw >6, fluid escape and thick accumulations are potential triggers of submarine landslides along the Alboran contouritic margins. Over the last decade, international collaboration between Spanish, French and Moroccan marine geologists working has allowed a large amount of high-resolution multibeam and multi- and single channel seismic data to be collected from the Alboran Sea. Multibeam and echosounder data collected during the SARAS Eurofleet cruise reveal the distribution of slope failures along the northern flank of the Xauen-Tofiño bank along the Moroccan margin and the southern flank of the Alboran ridge. Those highs are active folds located on both sides of the Trans Alboran Shear Zone (TASZ). Here we provide a detailed mapping and description of the morphology of the Xauen-Tofiño landslides, including volumetric estimates of the failed mass and the related mass transport deposits over the last 2 myr. The most voluminous Holocene landslide mobilized ~0.5 km3 of sediment at the initial stage of slope failure, and formed a ~2.2-2.4 km3 mass transport deposit. Twenty-eight and thirty-eight Mass Transport Deposits (MTD) were described from the Xauen and Tofiño banks, respectively. Boreholes analysis of ODP sites 976 and 979 allowed the calibration of some of the reflectors and relative ages of the pulses of tectonic activity and MTD's events. Active uplift pulses are observed at 1.19, 0.79 and 0.46 Ma for the Alboran ridge, and at 1.19 and 0.79 Ma for the Xauen-Tofiño Bank. We compute different parameters for each MTD's from the literature, including the volume of sediments involved and the porosity, thanks to physical laws. For few MTD's, we also map associated slump scars and compute parameters such as the run-off and the volume of sediments, deduced from the scar with a simple geometric reconstitution of the paleo-topography. The

  10. Tidal motions and tidally induced fluxes through La Línea submarine canyon, western Alboran Sea

    NASA Astrophysics Data System (ADS)

    Lafuente, Jesús GarcíA.; Sarhan, Tarek; Vargas, Manuel; Vargas, Juan M.; Plaza, Francisco

    1999-02-01

    Detailed observations from two mooring lines deployed in La Línea submarine canyon, western Alboran Sea, are presented. This is a narrow canyon in the sense that its width is always less than the internal radius of deformation. Tidal currents within the canyon are polarized in the along-canyon direction according to its narrow nature. They have considerable amplitude (values of around 0.5 m/s are often observed) and are forced by the internal pressure gradients associated with the baroclinic tide that is generated in the surroundings. Subsequent amplification of onshore baroclinic currents within the canyon accounts for the large amplitude observed. Cross-shelf exchange through the canyon due to tidal motions is different from zero despite the close to zero mean of tidal currents. The explanation is based on the asymmetry of water properties flowing up-canyon and down-canyon (some sort of tidal rectification). Regarding the energy flux, the canyon seems to be an adequate conduit to carry energy to the shore. Estimations made from our observations indicate that energy input onto the shelf per unit length parallel to the shore at the canyon head is enough to maintain mixing on the shelf at intermediate depths.

  11. Microfossils, a Key to Unravel Cold-Water Carbonate Mound Evolution through Time: Evidence from the Eastern Alboran Sea

    PubMed Central

    Stalder, Claudio; Vertino, Agostina; Rosso, Antonietta; Rüggeberg, Andres; Pirkenseer, Claudius; Spangenberg, Jorge E.; Spezzaferri, Silvia; Camozzi, Osvaldo; Rappo, Sacha; Hajdas, Irka

    2015-01-01

    Cold-water coral (CWC) ecosystems occur worldwide and play a major role in the ocean's carbonate budget and atmospheric CO2 balance since the Danian (~65 m.y. ago). However their temporal and spatial evolution against climatic and oceanographic variability is still unclear. For the first time, we combine the main macrofaunal components of a sediment core from a CWC mound of the Melilla Mounds Field in the Eastern Alboran Sea with the associated microfauna and we highlight the importance of foraminifera and ostracods as indicators of CWC mound evolution in the paleorecord. Abundances of macrofauna along the core reveal alternating periods dominated by distinct CWC taxa (mostly Lophelia pertusa, Madrepora oculata) that correspond to major shifts in foraminiferal and ostracod assemblages. The period dominated by M. oculata coincides with a period characterized by increased export of refractory organic matter to the seafloor and rather unstable oceanographic conditions at the benthic boundary layer with periodically decreased water energy and oxygenation, variable bottom water temperature/density and increased sediment flow. The microfaunal and geochemical data strongly suggest that M. oculata and in particular Dendrophylliidae show a higher tolerance to environmental changes than L. pertusa. Finally, we show evidence for sustained CWC growth during the Alleröd-Younger-Dryas in the Eastern Alboran Sea and that this period corresponds to stable benthic conditions with cold/dense and well oxygenated bottom waters, high fluxes of labile organic matter and relatively strong bottom currents PMID:26447699

  12. How is the surface Atlantic water inflow through the Gibraltar Strait forecasted? A lagrangian validation of operational oceanographic services in the Alboran Sea and the Western Mediterranean

    NASA Astrophysics Data System (ADS)

    Sotillo, M. G.; Amo-Baladrón, A.; Padorno, E.; Garcia-Ladona, E.; Orfila, A.; Rodríguez-Rubio, P.; Conti, D.; Madrid, J. A. Jiménez; de los Santos, F. J.; Fanjul, E. Alvarez

    2016-11-01

    An exhaustive validation of some of the operational ocean forecast products available in the Gibraltar Strait and the Alboran Sea is here presented. The skill of two ocean model solutions (derived from the Eulerian ocean forecast systems, such as the regional CMEMS IBI and the high resolution PdE SAMPA) in reproducing the complex surface dynamics in the above areas is evaluated. To this aim, in-situ measurements from the MEDESS-GIB drifter buoy database (comprising the Lagrangian positions, derived velocities and SST values) are used as the observational reference and the temporal coverage for the validation is 3 months (September to December 2014). Two metrics, a Lagrangian separation distance and a skill score, have been applied to evaluate the performance of the modelling systems in reproducing the observed trajectories. Furthermore, the SST validation with in-situ data is carried out by means of validating the model solutions with L3 satellite SST products. The Copernicus regional IBI products are evaluated in an extended domain, beyond the Alboran Sea, and covering western Mediterranean waters. This analysis reveals some strengths of the presented regional solution (i.e. realistic values of the Atlantic Jet in the Strait of Gibraltar area, realistic simulation of the Algerian Current). However, some shortcomings are also identified, with the major one being related to the simulated geographical position and intensity of the Alboran Gyres, particularly the western one. This performance limitation affects the IBI-modelled surface circulation in the entire Alboran Sea. On the other hand, the SAMPA system shows a more accurate model performance and it realistically reproduces the observed surface circulation in the area. The results reflect the effectiveness of the dynamical downscaling performed through the SAMPA system with respect to the regional IBI solution (in which SAMPA is nested), providing an objective measure of the potential added values introduced by

  13. A new diagnosis of the genus Delectona (Porifera, Demospongiae), with a description of a new species from the Alboran Sea (western Mediterranean)

    NASA Astrophysics Data System (ADS)

    Rosell, D.

    1996-12-01

    A redescription of the genus Delectona is provided, based on information gained by the finding of a new species, D. alboransis, from the Alboran Sea (southwestern Mediterranean Sea). Up to now, this genus contained only one species: Delectona higgini, from the Indian Ocean, which has not been recorded since 1880. The presence of megascleres in the new species and the different ranges of amphiaster lengths of the two species are the main features allowing a differentiation. In addition, the excavating capability of sponges of this genus is questioned, following the observations on the external morphology of D. alboransis. Our results support the hypothesis of other authors that some areas of the circalittoral level of the Alboran Sea may represent a redoubt of relict species with Indo-Pacific affinities.

  14. Highly diverse molluscan assemblages of Posidonia oceanica meadows in northwestern Alboran Sea (W Mediterranean): Seasonal dynamics and environmental drivers

    NASA Astrophysics Data System (ADS)

    Urra, Javier; Mateo Ramírez, Ángel; Marina, Pablo; Salas, Carmen; Gofas, Serge; Rueda, José L.

    2013-01-01

    The seasonal dynamics of the molluscan fauna associated with the westernmost populations of the Mediterranean seagrass Posidonia oceanica, has been studied throughout an annual cycle in the northwestern coasts of the Alboran Sea. Samples were collected seasonally (5 replicated per season) using a non-destructive sampling technique (airlift sampler) on quadrats of 50 × 50 cm at 2 sites located 7 km apart. Several environmental variables from the water column (temperature, chlorophyll a), the sediment (percentage of organic matter) and the seagrass meadows (shoot density, leaf height and width, number of leaves per shoot) were also measured in order to elucidate their relationships with the dynamics of the molluscan assemblages. In these meadows, a total of 17,416 individuals of molluscs were collected, belonging to 71 families and 171 species, being Rissoidae, Pyramidellidae and Trochidae the best-represented families, and Mytilidae, Nassaridae and Trochidae the dominant ones in terms of abundance. The assemblages were dominated by micro-algal grazers, filter feeders and ectoparasites (including those feeding on sessile preys). The species richness and the abundance displayed significant maximum values in summer, whereas evenness and diversity displayed maximum values in spring, being significant for the evenness. Both abundance and species richness values were positively correlated to seawater temperature and percentage organic matter, only for the latter, and negatively to leaf width. Significant seasonal groupings were obtained with multivariate analyses (MDS, Cluster, ANOSIM) using qualitative and quantitative data that could be mainly related to biological aspects (i.e. recruitment) of single species. The molluscan assemblages are influenced by the biogeographical location of the area (Alboran Sea), reflected in the absence or scarcity of most Mediterranean species strictly associated with P. oceanica (e.g. Tricolia speciosa, Rissoa ventricosa) and by the

  15. The seasonal cycle of the Atlantic Jet dynamics in the Alboran Sea: direct atmospheric forcing versus Mediterranean thermohaline circulation

    NASA Astrophysics Data System (ADS)

    Macias, Diego; Garcia-Gorriz, Elisa; Stips, Adolf

    2016-02-01

    The Atlantic Jet (AJ) is the inflow of Atlantic surface waters into the Mediterranean Sea. This geostrophically adjusted jet fluctuates in a wide range of temporal scales from tidal to subinertial, seasonal, and interannual modifying its velocity and direction within the Alboran Sea. At seasonal scale, a clearly defined cycle has been previously described, with the jet being stronger and flowing towards the northeast during the first half of the year and weakening and flowing more southwardly towards the end of the year. Different hypothesis have been proposed to explain this fluctuation pattern but, up to now, no quantitative assessment of the importance of the different forcings for this seasonality has been provided. Here, we use a 3D hydrodynamic model of the entire Mediterranean Sea forced at the surface with realistic atmospheric conditions to study and quantify the importance of the different meteorological forcings on the velocity and direction of the AJ at seasonal time scale. We find that the direct effects of local zonal wind variations are much more important to explain extreme collapse events when the jet dramatically veers southward than to the seasonal cycle itself while sea level pressure variations over the Mediterranean seem to have very little direct effect on the AJ behavior at monthly and longer time scales. Further model results indicate that the annual cycle of the thermohaline circulation is the main driver of the seasonality of the AJ dynamics in the model simulations. The annual cycles in local wind forcing and SLP variations over the Mediterranean have no causal relationship with the AJ seasonality.

  16. Characterization of the submesoscale energy cascade in the Alboran Sea thermocline from spectral analysis of high-resolution MCS data

    NASA Astrophysics Data System (ADS)

    Sallares, Valenti; Mojica, Jhon F.; Biescas, Berta; Klaeschen, Dirk; Gràcia, Eulàlia

    2016-06-01

    Part of the kinetic energy that maintains ocean circulation cascades down to small scales until it is dissipated through mixing. While most steps of this downward energy cascade are well understood, an observational gap exists at horizontal scales of 103-101 m that prevents characterizing a key step in the chain: the transition from anisotropic internal wave motions to isotropic turbulence. Here we show that this observational gap can be covered using high-resolution multichannel seismic (HR-MCS) data. Spectral analysis of acoustic reflectors imaged in the Alboran Sea thermocline shows that this transition is likely caused by shear instabilities. In particular, we show that the averaged horizontal wave number spectra of the reflectors vertical displacements display three subranges that reproduce theoretical spectral slopes of internal waves (λx > 100 m), Kelvin-Helmholtz-type shear instabilities (100 m > λx > 33 m), and turbulence (λx < 33 m), indicating that the whole chain of events is occurring continuously and simultaneously in the surveyed area.

  17. Interaction between seabed morphology and water masses around the seamounts on the Motril Marginal Plateau (Alboran Sea, Western Mediterranean)

    NASA Astrophysics Data System (ADS)

    Palomino, Desirée; Vázquez, Juan-Tomás; Ercilla, Gemma; Alonso, Belén; López-González, Nieves; Díaz-Del-Río, Víctor

    2011-12-01

    The seabed morphology in the vicinity of the seamounts on the Motril Marginal Plateau (northern Alboran Sea) was investigated using high-resolution (sparker) and very high-resolution (TOPAS) seismic reflection profiles and multibeam bathymetry. The aim of the study was to determine the recent geological processes, and in particular those that control the contourite depositional system associated with the intermediate and deep Mediterranean water masses. Six groups of morphological features were identified: structural features (seamount tops, tectonic depressions), fluid escape-related features (pockmarks), mass-movement features (gullies, slides), bottom-current features (moats, scour marks, terraces, elongated and separated drifts, plastered drifts, confined drifts, sheeted drifts), mixed features (ridges) and biogenic features (including evidence of (dead) cold water corals such as Lophelia pertusa and Madrepora oculata). The main processes controlling the formation of these features are recent tectonic activity and the interaction of Mediterranean water masses with the seafloor topography. Seamounts act as topographic barriers that affect the pathway and velocity of the deep Mediterranean water masses, which are divided into strands that interact with the surrounding seafloor. The influence of the intermediate Mediterranean water mass, by contrast, is restricted mainly to the tops of the seamounts. Sediment instability and fluid-escape processes play a minor role, their occurrence being probably related to seismicity.

  18. Deep Chlorophyll Maximum distribution in the Alboran sea and its relationship with mesoscale and frontal features through syncronous glider observations.

    NASA Astrophysics Data System (ADS)

    Olita, Antonio; Ribotti, Alberto; Ruiz, Simon; Pascual, Ananda

    2015-04-01

    May 25 2014, two gliders were launched in the framework of the multiplatform and multidisciplinary experiment in the Alboran sea named ALBOREX (a PERSEUS project sampling) and of the JERICO TNA FRIPP project. The two instruments glided for 6 days, during which ADCP, ship based CTD, ARGO floats and surface drifters also sampled surface to deep waters allowing, togheter with bottle water samples, to collect a comprehensive dataset of oceanographic multidisciplinary quasi-synoptic data at (sub-)mesoscale. This preliminary work presents the results related to the two glider launched at approximatively 20 km each other. The two gliders intercepted in their pathway a frontal structure belonging to the northern margin of a quite large and strong anticyclonic structure originating by the meandering of Atlantic Waters entering in Mediterranean through Gibraltar. The vertical structure of Chlorophyll-a (as derived by fluorimeter measurements) shows the area of subsidence across the front and the deepening of isolines in the eddy interior. The analysis of the relatively low-cost glider data, combined with synoptic satellite measurements, shed light on the dynamics determining the re-distribution of the phytoplanktonic biomass and provide pretious hints, combined with dissolved oxygen data also collected by the unmanned autonomous vehicles, about the influence of such dynamical features on Primary Production.

  19. Last glacial to Holocene productivity and oxygen changes based on benthic foraminiferal assemblages from the western Alboran Sea

    NASA Astrophysics Data System (ADS)

    Pérez-Asensio, José N.; Cacho, Isabel; Frigola, Jaime; Pena, Leopoldo D.; Asioli, Alessandra; Kuhlmann, Jannis; Huhn, Katrin

    2016-04-01

    Late glacial to Holocene productivity and oxygen changes in the Alboran Sea were investigated analyzing benthic foraminiferal assemblages from the marine sediment core HER-GC-UB06. This 255 cm-long core was recovered at 946 m water depth in the Alboran Sea (western Mediterranean Sea) and includes homogeneous greyish clays from the last 23 ka. Nowadays, the core site is bathed by the Western Mediterranean Deep Water (WMDW) and near the overlying Levantine Intermediate Water (LIW). Benthic foraminifera from the size fraction >63 μm were identified at species level and counted until reaching at least 300 individuals. Q-mode principal component analyses (PCA) was performed to establish benthic foraminiferal assemblages. In addition, benthic foraminifera were classified according to their microhabitat preferences. Diversity was assessed with several diversity indices. Four benthic foraminiferal assemblages have been identified along the core. The distribution of these assemblages records changes in productivity and oxygen conditions during the last 23 ka. The last glacial and deglaciation interval, 23-12.5 ka, shows low diversity and is characterized by the Nonionella iridea assemblage, which includes Cassidulina laevigata, Bolivina dilatata, Nonionoides turgida and Cibicides pachyderma as secondary taxa. This assemblage can be interpreted as a moderately oxygenated mesotrophic environment with episodic pulses of fresh organic matter. Although general mesotrophic conditions prevail, the Last Glacial Maximum shows a more oligotrophic and better oxygenated setting as suggested by higher abundance of epifaunal-shallow infaunal taxa. In contrast, along the Bølling-Allerød eutrophic conditions with higher productivity and lower oxygenation are recorded by a deep infaunal taxa maximum. During the Younger Dryas (YD) and the earliest Holocene (12.5-10.5 ka), the Bolivina dilatata assemblage dominates coinciding with a lower diversity, especially during the YD. This species

  20. Beaked Whales and Pilot Whales in the Alboran Sea SW Mediterranean

    DTIC Science & Technology

    2011-09-30

    dorsal fin and other distinguishing features (for example, pigmentation patterns and scars) of individual pilot whales were usually taken by 5 or 6...and photosynthetically available radiation (PAR) measurements from the SeaWiFS sensor aboard the GeoEye spacecraft, SST measurements from the NOAA

  1. Aerosol Characteristics on the Alboran Sea, 9-18 October 1982

    DTIC Science & Technology

    1983-12-01

    8217FALO NY AerosDi Characteristics on tne Aiboran Sea, 9—13 Q c t o d e r 19 S 2» (u) tractor rspc, 1/ bep ti’Z—/ cisp S-::-, u...Boundary Layer in the Gulf of Mexico ," Calspan Report, 64 pp. 11. Mack, E.J., R.J. Anderson, C.K. Akers, and T.A. Niziol, 1978: "Aerosol...COMMANDER & DIRECTOR ATTN: DELAS-AS-P U.S. ARMY ATMOS. SCI. LAB WHITE SANDS MISSILE RANGE, NEW MEXICO 88002 USAFETAC/TS SCOTT AFB, IL 62225

  2. Spatial variability and response to anthropogenic pressures of assemblages dominated by a habitat forming seaweed sensitive to pollution (northern coast of Alboran Sea).

    PubMed

    Bermejo, Ricardo; de la Fuente, Gina; Ramírez-Romero, Eduardo; Vergara, Juan J; Hernández, Ignacio

    2016-04-15

    The Cystoseira ericaefolia group is conformed by three species: C. tamariscifolia, C. mediterranea and C. amentacea. These species are among the most important habitat forming species of the upper sublittoral rocky shores of the Mediterranean Sea and adjacent Atlantic coast. This species group is sensitive to human pressures and therefore is currently suffering important losses. This study aimed to assess the influence of anthropogenic pressures, oceanographic conditions and local spatial variability in assemblages dominated by C. ericaefolia in the Alboran Sea. The results showed the absence of significant effects of anthropogenic pressures or its interactions with environmental conditions in the Cystoseira assemblages. This fact was attributed to the high spatial variability, which is most probably masking the impact of anthropogenic pressures. The results also showed that most of the variability occurred on at local levels. A relevant spatial variability was observed at regional level, suggesting a key role of oceanographic features in these assemblages.

  3. Looking for long-term changes in hydroid assemblages (Cnidaria, Hydrozoa) in Alboran Sea (South-Western Mediterranean): a proposal of a monitoring point for the global warming

    NASA Astrophysics Data System (ADS)

    González-Duarte, Manuel María; Megina, Cesar; Piraino, Stefano

    2014-12-01

    In the last 20-30 years, the temperature of the Mediterranean Sea has increased and global warming is allowing the establishment of tropical-affinity species into more temperate zones. Sessile communities are particularly useful as a baseline for ecological monitoring; however, a lack of historical data series exists for sessile marine organisms without commercial interest. Hydroids are ubiquitous components of the benthic sessile fauna on rocky shores and have been used as bio-indicators of environmental conditions. In this study on the benthic hydroid assemblages of the Chafarinas Islands (Alboran Sea, South-Western Mediterranean), we characterized the hydroid assemblages, identified the bathymetric gradients, and compared them with a previous study carried out in 1991. Hydroid assemblages showed a significant difference both between year and among depths. Furthermore, eight species not present in 1991 were found, including two possible new species and the tropical and subtropical species Sertularia marginata. Due to its strategic position at the entrance of the Mediterranean and the existence of previous data on hydroid assemblages, the Chafarinas Islands are proposed as a possible monitoring point for entrance of Atlantic tropical species into the Mediterranean Sea.

  4. Crustal and upper mantle shear velocities of Iberia, the Alboran Sea, and North Africa from ambient noise and ballistic finite-frequency Rayleigh wave tomography

    NASA Astrophysics Data System (ADS)

    Palomeras, I.; Villasenor, A.; Thurner, S.; Levander, A.; Gallart, J.; mimoun, H.

    2013-12-01

    The complex Mesozoic-Cenozoic Alpine deformation in the western Mediterranean extends from the Pyrenees in northern Spain to the Atlas Mountains in southern Morocco. The Iberian plate was accreted to the European plate in late Cretaceous, resulting in the formation of the Pyrenees. Cenozoic African-European convergence resulted in subduction of the Tethys oceanic plate beneath Europe. Rapid Oligocene slab rollback from eastern Iberia spread eastward and southward, with the trench breaking into three segments by the time it reached the African coast. One trench segment moved southwestward and westward creating the Alboran Sea, floored by highly extended continental crust, and building the encircling Betics Rif mountains comprising the Gibraltar arc, and the Atlas mountains, which formed as the inversion of a Jurassic rift. A number of recent experiments have instrumented this region with broad-band arrays (the US PICASSO array, Spanish IberArray and Siberia arrays, the University of Munster array), which, including the Spanish, Portuguese, and Moroccan permanent networks, provide a combined array of 350 stations having an average interstation spacing of ~60 km. Taking advantage of this dense deployment, we have calculated the Rayleigh waves phase velocities from ambient noise for short periods (4 s to 40 s) and teleseismic events for longer periods (20 s to 167 s). Approximately 50,000 stations pairs were used to measure the phase velocity from ambient noise and more than 160 teleseismic events to measure phase velocity for longer periods. The inversion of the phase velocity dispersion curves provides a 3D shear velocity for the crust and uppermost mantle. Our results show differences between the various tectonic regions that extend to upper mantle depths (~200 km). In Iberia we obtain, on average, higher upper mantle shear velocities in the western Variscan region than in the younger eastern part. We map high upper mantle velocities (>4.6 km/s) beneath the

  5. Acoustic and seismic imaging of the Adra Fault (NE Alboran Sea): in search of the source of the 1910 Adra earthquake

    NASA Astrophysics Data System (ADS)

    Gràcia, E.; Bartolome, R.; Lo Iacono, C.; Moreno, X.; Stich, D.; Martínez-Diaz, J. J.; Bozzano, G.; Martínez-Loriente, S.; Perea, H.; Diez, S.; Masana, E.; Dañobeitia, J. J.; Tello, O.; Sanz, J. L.; Carreño, E.; Event-Shelf Team

    2012-11-01

    Recently acquired swath-bathymetry data and high-resolution seismic reflection profiles offshore Adra (Almería, Spain) reveal the surficial expression of a NW-SE trending 20 km-long fault, which we termed the Adra Fault. Seismic imaging across the structure depicts a sub-vertical fault reaching the seafloor surface and slightly dipping to the NE showing an along-axis structural variability. Our new data suggest normal displacement of the uppermost units with probably a lateral component. Radiocarbon dating of a gravity core located in the area indicates that seafloor sediments are of Holocene age, suggesting present-day tectonic activity. The NE Alboran Sea area is characterized by significant low-magnitude earthquakes and by historical records of moderate magnitude, such as the Mw = 6.1 1910 Adra Earthquake. The location, dimension and kinematics of the Adra Fault agree with the fault solution and magnitude of the 1910 Adra Earthquake, whose moment tensor analysis indicates normal-dextral motion. The fault seismic parameters indicate that the Adra Fault is a potential source of large magnitude (Mw ≤ 6.5) earthquakes, which represents an unreported seismic hazard for the neighbouring coastal areas.

  6. From basin to sub-basin scale assessment and intercomparison of numerical simulations in the Western Mediterranean Sea

    NASA Astrophysics Data System (ADS)

    Juza, Mélanie; Mourre, Baptiste; Lellouche, Jean-Michel; Tonani, Marina; Tintoré, Joaquin

    2015-09-01

    This study describes a quantitative evaluation of simulations in the western Mediterranean Sea at basin and sub-basin scales. The Mediterranean Forecasting System and the Mercator-Océan simulations provide operational ocean forecasts and hindcasts in the Mediterranean, and are also used as initial and boundary conditions for regional models. In this context, hindcast simulations from 2009 to 2012 are compared with available multi-platform observations at various spatial and temporal scales to evaluate their performance. Both simulations reproduce well the observed mean conditions and variability over the last years. The sub-basin scale analyses of the three-dimensional ocean structures and water mass properties reveal seasonal and regional temperature and salinity errors at the surface in both simulations, as well as significant biases at intermediate and deep layers in the Mediterranean Forecasting System. The simulated surface geostrophic velocities are weaker than those derived from altimetry, and circulation biases persist in the Balearic Sea. Additionally, the seasonal existence of the Alboran gyres is not well reproduced in either simulation. The identification of regional simulation biases is essential to advance from global to regional and local scale forecasting, in particular, improving the representation of the local physical processes and their interactions with the sub-basin dynamics and the general circulation.

  7. Seismostratigraphy and tectonic architecture of the Carboneras Fault offshore based on multiscale seismic imaging: Implications for the Neogene evolution of the NE Alboran Sea

    NASA Astrophysics Data System (ADS)

    Moreno, Ximena; Gràcia, Eulàlia; Bartolomé, Rafael; Martínez-Loriente, Sara; Perea, Héctor; de la Peña, Laura Gómez; Iacono, Claudio Lo; Piñero, Elena; Pallàs, Raimon; Masana, Eulàlia; Dañobeitia, Juan José

    2016-10-01

    In the SE Iberian Margin, which hosts the convergent boundary between the European and African Plates, Quaternary faulting activity is dominated by a large left-lateral strike-slip system referred to as the Eastern Betic Shear Zone. This active fault system runs along more than 450 km and it is characterised by low to moderate magnitude shallow earthquakes, although large historical events have also occurred. The Carboneras Fault is the longest structure of the Eastern Betic Shear Zone, and its southern termination extends further into the Alboran Sea. Previously acquired high-resolution data (i.e. swath-bathymetry, TOBI sidescan sonar and sub-bottom profiler) show that the offshore Carboneras Fault is a NE-SW-trending upwarped zone of deformation with a length of 90 km long and a width of 0.5 to 2 km, which shows geomorphic features typically found in subaerial strike-slip faults, such as deflected drainage, pressure ridges and "en echelon" folds. However, the neotectonic, depth architecture, and Neogene evolution of Carboneras Fault offshore are still poorly known. In this work we present a multiscale seismic imaging of the Carboneras Fault (i.e. TOPAS, high-resolution multichannel-seismic reflection, and deep penetration multichannel-seismic reflection) carried out during three successive marine cruises, from 2006 to 2010. The new dataset allowed us to define a total of seven seismostratigraphic units (from Tortonian to Late Quaternary) above the basement, to characterise the tectonic architecture and structural segmentation of the Carboneras Fault, and to estimate its maximum seismic potential. We finally discuss the role of the basement in the present-day tectonic evolution of the Carboneras Fault, and explore the northern and southern terminations of the fault and how the strain is transferred to nearby structures.

  8. Understanding the Patterns and Causes of Variability in Distribution, Habitat Use, Abundance, Survival and Reproductive Rates of Three Species of Cetacean in the Alboran Sea, Western Mediterranean

    DTIC Science & Technology

    2011-09-30

    species that feed at lower trophic levels ; (3) Explore the relative contribution of environmental variation and anthropogenic activities on...predators is an important one because of their role within ecosystems and their potential to influence community structure and biodiversity (Heithaus...southern Spain. The Alborán Sea is a highly productive and distinct ecosystem that plays an important role in the oceanography of the Mediterranean basin

  9. Impacts of reprocessed altimetry on the surface circulation and variability of the Western Alboran Gyre

    NASA Astrophysics Data System (ADS)

    Juza, Mélanie; Escudier, Romain; Pascual, Ananda; Pujol, Marie-Isabelle; Taburet, Guillaume; Troupin, Charles; Mourre, Baptiste; Tintoré, Joaquín

    2016-08-01

    New altimetry products in semi-enclosed seas are of major interest given the importance of the coastal-open ocean interactions. This study shows how reprocessed altimetry products in the Mediterranean Sea from Archiving, Validation and Interpolation of Satellite Oceanographic data (AVISO) have improved the representation of the surface circulation over the 1993-2012 period. We focus on the Alboran Sea, which is the highest mesoscale activity area of the western Mediterranean. The respective impacts of the new mean dynamic topography (MDT) and mapped sea level anomaly (MSLA) on the description of the Western Alboran Gyre (WAG) are quantitatively evaluated. The temporal mean and variability of the total kinetic energy have been significantly increased in the WAG considering both the new MDT and MSLA (by more than 50%). The new MDT has added 39% to the mean kinetic energy, while the new MSLA has increased the eddy kinetic energy mean (standard deviation) by 53% (30%). The new MSLA has yielded higher variability of total (eddy) kinetic energy, especially in the annual frequency band by a factor of 2 (3). The MDT reprocessing has particularly increased the low-frequency variability of the total kinetic energy by a factor of 2. Geostrophic velocities derived from the altimetry products have also been compared with drifter data. Both reprocessed MDT and MSLA products intensify the velocities of the WAG making them closer to the in situ estimations, reducing the root mean square differences and increasing the correlation for the zonal and meridional components. The results obtained using refined coastal processing of altimetry products and new observational data are very encouraging to better understand the ocean circulation variability and coastal-open ocean interactions, and for potential improvements in other sub-basins, marginal seas and coastal global ocean.

  10. Aral Sea basin: a sea dies, a sea also rises.

    PubMed

    Glantz, Michael H

    2007-06-01

    The thesis of this article is quite different from many other theses of papers, books, and articles on the Aral Sea. It is meant to purposely highlight the reality of the situation in Central Asia: the Aral Sea that was once a thriving body of water is no more. That sea is dead. What does exist in its place are the Aral seas: there are in essence three bodies of water, one of which is being purposefully restored and its level is rising (the Little Aral), and two others which are still marginally connected, although they continue to decline in level (the Big Aral West and the Big Aral East). In 1960 the level of the sea was about 53 m above sea level. By 2006 the level had dropped by 23 m to 30 m above sea level. This was not a scenario generated by a computer model. It was a process of environmental degradation played out in real life in a matter of a few decades, primarily as a result of human activities. Despite wishes and words to the contrary, it will take a heroic global effort to save what remains of the Big Aral. It would also take a significant degree of sacrifice by people and governments in the region to restore the Big Aral to an acceptable level, given that the annual rate of flow reaching the Amudarya River delta is less than a 10th of what it was several decades ago. Conferring World Heritage status to the Aral Sea(s) could spark restoration efforts for the Big Aral.

  11. Magmatic evolution of the Alboran region: The role of subduction in forming the western Mediterranean and causing the Messinian Salinity Crisis

    NASA Astrophysics Data System (ADS)

    Duggen, Svend; Hoernle, Kaj; van den Bogaard, Paul; Harris, Chris

    2004-01-01

    The magmatic evolution of the Alboran region (westernmost Mediterranean) contains important clues for improving our understanding of the origin of Mediterranean-style back-arc basins and the desiccation of the Mediterranean Sea in the Messinian. We use new laser 40Ar/ 39Ar age and geochemical (major and trace element and O-Sr-Nd-Pb isotope) data from igneous rocks from southern Spain, the Alboran Sea and northern Morocco to reconstruct the magmatic evolution of the westernmost Mediterranean since the Eocene. Lower Oligocene dikes near Malaga (33.6±0.6 Ma) and Middle to Upper Miocene volcanic rocks from the Alboran Sea area (6.57±0.04 to 11.8±0.4 Ma) can be subdivided into two groups: (1) LREE-depleted (relative to N-MORB), primarily tholeiitic series, and (2) LREE-enriched, primarily calc-alkaline series volcanic rocks. Both groups are generally enriched in fluid-mobile elements (e.g. Rb, Th, U, K and Pb) relative to fluid-immobile elements (e.g. Nb, Ta, LREE). The LREE-depleted group has 143Nd/ 144Nd (0.5128-0.5130) isotope ratios similar to Atlantic MORB but higher 87Sr/ 86Sr (0.7046-0.7100). In contrast, the LREE-enriched group has less radiogenic Nd (0.5121-0.5126) and tend to more radiogenic Sr (0.7066-0.7205) isotopic composition. Pb isotope ratios are surprisingly uniform and have compositions similar to marine sediments. Analyses of mineral separates show that mafic melts with relatively low δ 18O (5.6-7.2‰) had high 87Sr/ 86Sr (0.7048-0.7088), Δ7/4 (10.6-14.1) and Δ8/4 (40.0-49.3). Modeling of the trace elements and Sr-Nd-Pb-O isotopic compositions provides compelling evidence for the contamination of the mantle source with hydrous fluids/melts, which can be explained through subduction of oceanic lithosphere beneath the Alboran Basin but not through detachment/delamination of lithospheric mantle. We present a geodynamic model that reconstructs the Late Eocene to Quaternary evolution of the western Mediterranean through westward roll-back of

  12. Understanding the Patterns and Causes of Variability in Distribution, Habitat Use, Abundance, Survival and Reproductive Rates of Three Species of Cetacean in the Alboran Sea, Western Mediterranean

    DTIC Science & Technology

    2014-09-30

    Distribution, Habitat Use, Abundance, Survival and Reproductive Rates of Three Species of Cetacean in the Alborán Sea, Western Mediterranean...changes in distribution, habitat use, abundance, survival and reproductive rates of three species of cetacean in the Alborán Sea (western Mediterranean...to environmental change, particularly climate change, focusing on distribution, abundance and estimated reproductive and survival rates. The two

  13. Beaked Whales and Pilot Whales in the Alboran Sea (SW Mediterranean): Research Towards Improved Science-Based Mitigation Strategies for Risks from Man-Made Sound

    DTIC Science & Technology

    2010-09-30

    sighting, and compiling and organizing all the data in an excel spreadsheet in a format more easily usable for analysis. Tagging of pilot whales...Sea (SGM), the National Scientific Council (CSIC) the Spanish Oceanographic Institute (IEO) and the NGOs SEO Birdlife, WWF Adena, OCEANA, SECAC

  14. Extreme flood events in the Dead Sea basin

    NASA Astrophysics Data System (ADS)

    Ahlborn, Marieke; Ben Dor, Yoav; Schwab, Markus J.; Neugebauer, Ina; Plessen, Birgit; Tjallingii, Rik; Erel, Yigal; Enzel, Yehouda; Brauer, Achim

    2016-04-01

    The Dead Sea is a hypersaline, terminal lake located within the Dead Sea basin at the lowest continental elevation on Earth (~425 m below mean sea level). Extreme hydro-meteorological events in terms of flash floods occur regularly during the wet season in the Dead Sea basin and adjacent mountain ranges. However, little is known about the impact of these extreme floods on the sedimentary dynamics in the Dead Sea and possible links to long-term climate changes. The trilateral research project PALEX (Paleoclimate in the Eastern Mediterranean Region - Levante: Paleohydrology and Extreme Flood Events) was recently initiated within the framework of the DFG priority program 1006 ICDP (International Continental Scientific Drilling Program) to investigate extreme flood events in the Dead Sea basin during the Late Pleistocene and Holocene. Within the ICDP Dead Sea Deep Drilling Project (DSDDP) the ~455 m long sediment core 5017-1 was recovered from the northern Dead Sea basin. Previously published results (Neugebauer et al., 2014, 2015) have demonstrated the occurrence of extreme flood events represented in the sediments as thick graded detrital layers during Late Holocene dry phases. Based on these results we will apply a comprehensive analytical approach including microfacies analyses, μXRF element scanning, and stable isotope geochemistry to different time intervals of core 5017-1. Particularly, we aim to investigate the structure and composition of detrital layers in order to decipher sediment transport mechanisms and the provenance of the flood-triggered sediments. The overarching goal is to establish a high-resolution extreme flood time series for the Dead Sea basin on the basis of a previously established radiocarbon and U-Th chronology (Torfstein et al., 2015; Neugebauer et al., 2014) and to study a possible link between the frequency and magnitude of extreme flood events and the long-term climate trend. Neugebauer I, Brauer A, Schwab MJ, et al. (2014) Lithology of

  15. Practical application of a sea-water battery in deep-sea basin and its performance

    NASA Astrophysics Data System (ADS)

    Shinohara, Masanao; Araki, Eiichiro; Mochizuki, Masashi; Kanazawa, Toshihiko; Suyehiro, Kiyoshi

    Stable power supply is essential for various long-term sea floor geophysical observations. Due to a simple structure and a large energy capacity, sea-water batteries have been developed and used for such observations. However, the characteristics of sea-water batteries have not been well known in the case of installations at depths more than 5000 m in deep-sea basin. In 2000, a sea floor borehole broadband seismic observatory was installed in the northwestern Pacific basin where the water depth is 5577 m. For electric power supply, a Sea-Water Battery (SWB) system with monitoring and control was developed and used. The SWB system consists of four sea-water battery cells, a DC/DC converter, the Power Control System, the Data Logger, and an accumulator. The conditions of the SWB system were recorded more than 1 year, and the monitoring data was recovered. The SWB system generated enough power for the observation system consuming power of 6 W in average and continued to supply power for at least 5 years. From the monitoring data, the SWB can supply up to the long-term average of at least 13 W. The energy density is estimated to be 318 Wh kg -1. The sea-water battery is useful for application of long-term power consumption even in the deep-sea basin.

  16. Decadal variability of Arctic sea ice in the Canada Basin

    NASA Astrophysics Data System (ADS)

    Connor, L. N.

    2015-12-01

    A series of spring Arctic flight campaigns surveying a region over the Canada Basin, from 2006 to 2015, has resulted in unique observations that reveal new details of sea ice leads and freeboard evolution, during a decade of significant interannual variability in the Arctic ice cover. The series began in 2006 with a joint NASA/NOAA airborne altimetry campaign over a 1300 km survey line northwest of the Canadian Archipelago extending into the northern Beaufort Sea. Operation IceBridge (OIB) took up this flight line again in 2009 and repeated it annually through 2012. Additional observations have been collected along a 1000+ km flight line, in the southern Canada Basin and eastern Beaufort Sea, between 2009 and 2015. Here we examine laser altimetry, snow radar data, and high-resolution visible imagery to better understand the frequency and distribution of leads and ice floes, the characteristics of first- and multi-year ice types in the survey region, and their impact on the derivation and accuracy of sea ice freeboard. We demonstrate a novel lead detection methodology that depends only upon laser altimeter measurements, and we quantify the impact of low lead frequencies on estimates of instantaneous sea surface height. The analysis reveals a variable springtime freeboard north of 78° N, significantly reduced after 2006, and a notable lead outbreak over the Canada Basin during 2010.

  17. Stress tensor and focal mechanisms in the Dead Sea basin

    NASA Astrophysics Data System (ADS)

    Hofstetter, A.; Dorbath, C.; Dorbath, L.; Braeuer, B.; Weber, M.

    2016-04-01

    We use the recorded seismicity, confined to the Dead Sea basin and its boundaries, by the Dead Sea Integrated Research (DESIRE) portable seismic network and the Israel and Jordan permanent seismic networks for studying the mechanisms of earthquakes in the Dead Sea basin. The observed seismicity in the Dead Sea basin is divided into nine regions according to the spatial distribution of the earthquakes and the known tectonic features. The large number of recording stations and the adequate station distribution allowed the reliable determinations of 494 earthquake focal mechanisms. For each region, based on the inversion of the observed polarities of the earthquakes, we determine the focal mechanisms and the associated stress tensor. For 159 earthquakes, out of the 494 focal mechanisms, we could determine compatible fault planes. On the eastern side, the focal mechanisms are mainly strike-slip mechanism with nodal planes in the N-S and E-W directions. The azimuths of the stress axes are well constrained presenting minimal variability in the inversion of the data, which is in agreement with the Eastern Boundary fault on the east side of the Dead Sea basin and what we had expected from the regional geodynamics. However, larger variabilities of the azimuthal and dip angles are observed on the western side of the basin. Due to the wider range of azimuths of the fault planes, we observe the switching of σ1 and σ2 or the switching of σ2 and σ3 as major horizontal stress directions. This observed switching of stress axes allows having dip-slip and normal mechanisms in a region that is dominated by strike-slip motion.

  18. IODP expedition 347: Baltic Sea basin paleoenvironment and biosphere

    NASA Astrophysics Data System (ADS)

    Andrén, T.; Barker Jørgensen, B.; Cotterill, C.; Green, S.; IODP expedition 347 scientific party, the

    2015-12-01

    The Integrated Ocean Drilling Program (IODP) expedition 347 cored sediments from different settings of the Baltic Sea covering the last glacial-interglacial cycle. The main aim was to study the geological development of the Baltic Sea in relation to the extreme climate variability of the region with changing ice cover and major shifts in temperature, salinity, and biological communities. Using the Greatship Manisha as a European Consortium for Ocean Research Drilling (ECORD) mission-specific platform, we recovered 1.6 km of core from nine sites of which four were additionally cored for microbiology. The sites covered the gateway to the North Sea and Atlantic Ocean, several sub-basins in the southern Baltic Sea, a deep basin in the central Baltic Sea, and a river estuary in the north. The waxing and waning of the Scandinavian ice sheet has profoundly affected the Baltic Sea sediments. During the Weichselian, progressing glaciers reshaped the submarine landscape and displaced sedimentary deposits from earlier Quaternary time. As the glaciers retreated they left a complex pattern of till, sand, and lacustrine clay, which in the basins has since been covered by a thick deposit of Holocene, organic-rich clay. Due to the stratified water column of the brackish Baltic Sea and the recurrent and widespread anoxia, the deeper basins harbor laminated sediments that provide a unique opportunity for high-resolution chronological studies. The Baltic Sea is a eutrophic intra-continental sea that is strongly impacted by terrestrial runoff and nutrient fluxes. The Holocene deposits are recorded today to be up to 50 m deep and geochemically affected by diagenetic alterations driven by organic matter degradation. Many of the cored sequences were highly supersaturated with respect to methane, which caused strong degassing upon core recovery. The depth distributions of conservative sea water ions still reflected the transition at the end of the last glaciation from fresh-water clays to

  19. Morphometric analysis of the Marmara Sea river basins, Turkey

    NASA Astrophysics Data System (ADS)

    Elbaşı, Emre; Ozdemir, Hasan

    2014-05-01

    The drainage basin, the fundamental unit of the fluvial landscape, has been focus of research aimed at understanding the geometric characteristics of the master channel and its tributary network. This geometry is referred to as the basin morphometry and is nicely reviewed by Abrahams (1984). A great amount of research has focused on geometric characteristic of drainage basins, including the topology of the stream networks, and quantitative description of drainage texture, pattern, shape, and relief characteristics. Evaluation of morphometric parameters necessitates the analysis of various drainage parameters such as ordering of the various streams, measurement of basin area and perimeter, length of drainage channels, drainage density (Dd), stream frequency (Fs), bifurcation ratio (Rb), texture ratio (T), basin relief (Bh), Ruggedness number (Rn), time of concentration (Tc), hypsometric curve and integral (Hc and Hi) (Horton, 1932, Schumn, 1956, Strahler, 1957; Verstappen 1983; Keller and Pinter, 2002; Ozdemir and Bird, 2009). These morphometric parameters have generally been used to predict flood peaks, to assess sediment yield, and to estimate erosion rates in the basins. River basins of the Marmara Sea, has an area of approximately 40,000 sqkm, are the most important basins in Turkey based on their dense populations, industry and transportation systems. The primary aim of this study is to determine and analyse of morphometric characteristics of the Marmara Sea river basins using 10 m resolution Digital Elevation Model (DEM) and to evaluate of the results. For these purposes, digital 10 m contour maps scaled 1:25000 and geological maps scaled 1:100000 were used as the main data sources in the study. 10 m resolution DEM data were created using the contour maps and then drainage networks and their watersheds were extracted using D8 pour point model. Finally, linear, areal and relief morphometries were applied to the river basins using Geographic Information Systems

  20. Ground Motion Prediction Atop Geometrically Complex Sedimentary Basins - The Dead Sea Basin

    NASA Astrophysics Data System (ADS)

    Shani-Kadmiel, S.; Tsesarsky, M.; Louie, J. N.; Gvirtzman, Z.

    2014-12-01

    The Dead Sea Transform (DST) is the source for some of the largest earthquakes in the eastern Mediterranean. Several deep and structurally complex sedimentary basins are associated with the DST. These basins are up to 10 km deep and typically bounded by active fault zones. The low seismicity of the DST combined with the limited instrumental coverage of the seismic network in the area result in a critical knowledge gap. Therefore, it is necessary to complement the limited instrumental data with synthetic data based on computational modeling, in order to study the effects of earthquake ground motion in these sedimentary basins. We performed a 2D ground-motion analysis in the Dead Sea Basin (DSB) using a finite-difference code. Results indicate a complex pattern of ground motion amplification affected by the geometric features in the basin. To distinguish between the individual contributions of each geometrical feature in the basin, we developed a semiquantitative decomposition approach. This approach enabled us to interpret the DSB results as follows: (1) Ground-motion amplification as a result of resonance occurs basin-wide due to a high impedance contrast at the base of the uppermost layer; (2) Steep faults generate a strong edge-effect that further ampli- fies ground motions; (3) Sub-basins cause geometrical focusing that may significantly amplify ground motions; and (4) Salt diapirs diverge seismic energy and cause a de- crease in ground-motion amplitude. We address the significance of ground motion amplification due to geometrical focusing via an analytical and numerical study. We show that effective geometrical focusing occurs for a narrow set of eccentricities and velocity ratios, where seismic energy is converged to a region of ±0.5 km from surface. This mechanism leads to significant ground motion amplification at the center of the basin, up to a factor of 3; frequencies of the modeled spectrum are amplified up to the corner frequency of the source.

  1. Geologic evolution of the Bering Sea Komandorksy deep basin

    SciTech Connect

    Bogdanov, N.A.

    1986-07-01

    The deep-water Komandorsky basin is located in the southwestern part of the Bering Sea. On the east, it is separated from the Aleutian basin by the submerged Shirshov Ridge; on the west, it is bordered by structures of the north Kamchatka accretionary prism. The Komandorsky basin is characterized by strongly dissected relief of it acoustic basement, which is overlain by a 1.5 to 2.0-km thick sedimentary cover. The western part of the basin is occupied by a rift zone, which is characterized by modern seismicity and high heat flow. It is considered to be the axial zone of Miocene-Pleistocene spreading. On the north terrace of the Komandorsky island arc, traced active volcanos provide evidence that subduction is occurring under the arc from the north. The spreading rift zone is reflected on the continent in Miocene-Pleistocene volcanic rocks, characterized by typical oceanic tholeiitic composition. The Komandorsky basin formed as a result of spreading during the Maestrichtian. Spreading within the basin occurred during the early and middle Oligocene and the late Miocene. East and west of the spreading axis, accretionary prisms formed. The latter are observed along the western flank of the Shirshov Ridge and on the eastern sides of the Kamchatka Peninsula and Koraginsky Island.

  2. Occurrence of organohalogens at the Dead Sea Basin

    NASA Astrophysics Data System (ADS)

    Tubbesing, Christoph; Kotte, Karsten; Keppler, Frank; Krause, Torsten; Bahlmann, Enno; Schöler, Heinfried

    2013-04-01

    Most arid and semi-arid regions are characterized by evaporites, which are assured sources for volatile organohalogens (VOX) [1]. These compounds play an important role in tropospheric and stratospheric chemistry. The Dead Sea between Israel and Jordan is the world's most famous and biggest all-season water covered salt lake. In both countries chemical plants like the Dead Sea Works and the Arab Potash Company are located at the southern part of the Dead Sea and mine various elements such as bromine and magnesium. Conveying sea water through constructed evaporation pans multifarious salts are enriched and precipitated. In contrast, the Northern basin and main part of the Dead Sea has remained almost untouched by industrial salt production. Its fresh water supply from the Jordan River is constantly decreasing, leading to further increased salinity. During a HALOPROC campaign (Natural Halogenation Processes in the Environment) we collected various samples including air, soils, sediments, halophytic plants, ground- and seawater from the Northern and Southern basin of the Israeli side of the Dead Sea. These samples were investigated for the occurrence of halocarbons using different analytical techniques. Most samples were analyzed for volatile organohalogens such as haloalkanes using gas chromatography- mass spectrometry (GC-MS). Interestingly, there is a strong enrichment of trihalomethanes (THM), especially all chlorinated and brominated ones and also the iodinated compound dichloroiodomethane were found in the Southern basin. In addition, volatile organic carbons (VOC) such as ethene and some other alkenes were analyzed by a gas chromatography-flame ionisation detector (GC-FID) to obtain further information about potential precursors of halogenated compounds. Halophytic plants were investigated for their potential to release chloromethane and bromomethane but also for their stable carbon and hydrogen isotope composition. For this purpose, a plant chamber was

  3. Late Pleistocene carbonate dissolution in the Venezuela Basin, Caribbean Sea

    SciTech Connect

    Cofer-Shabica, N.B.; Peterson, L.C.

    1985-01-01

    Piston cores from water depths greater than 4000 m in the Venezuela Basin (Caribbean Sea) provide continuous late Pleistocene records of carbonate dissolution and accumulation. The authors examination of multiple dissolution indices indicate that, at least for the last 150,000 years, dissolution of carbonate in the Venezuela Basin has been more intense during interglacial than glacial periods, a pattern opposite to more general observations from the deep Atlantic and Gulf of Mexico. By virtue of its shallow sill depth (1815 m), the Venezuela Basin is relatively isolated from the mainstream of Atlantic thermohaline circulation, and presently is filled with homogeneous, relatively warm (3.8/sup 0/C) waters primarily derived from Upper North Atlantic Deep Water. During the last glacial, the enhanced preservation of carbonate in the Venezuela Basin suggests the presence of a less corrosive, more oxygenated water mass in the Atlantic near sill depth. However, this simple interpretations is potentially complicated by past changes in the rain of biogenic materials from surface waters to the deep basin in what must be an essentially closed system below sill depth. Their observations of increased interglacial dissolution may help to explain previously noted discrepancies in the local glacial to interglacial amplitude of delta/sup 18/O variations recorded by coccoliths and planktonic foraminifera.

  4. Oil and gas bearing in Norwegian Sea basins

    NASA Astrophysics Data System (ADS)

    Zabanbark, A.

    2013-07-01

    The Norwegian passive continental margin is represented by an extensive gentle shelf and continental slope. On the continental slope, there are the isolated Vøring, Møre and Ras basins, the Halten Terrace is situated to the east of them at the shelf, then the Nordland submarine ridge and the Trondelag Platform at the seaboard. There are Paleozoic, Mesozoic and Cenozoic sediments in its sections. Two complex structures are clearly distinguished in the sedimentary section: the lower stage (up to the Upper Cretaceous), reflecting the rifting structure of the basins, broken by a system of dislocations to a series of horsts, grabens, and separated blocks; and the upper stage, poorly dislocated, like a mantle covering the lower stage, with erosion and sharp unconformity. The Halten Terrace is the principal oil and gas production basin. At present, there are more than 50 oil, gas, and condensate fields in it. The following particularities have been discovered: than the field lays in the deepwater, than the age of the hydrocarbon pay is younger. It is also interesting that all gas fields are situated in the Vøring and Møre basins and western part of the Halten Terrace; the oil and gas fields, mainly at the center of the Halten Terrace; but pure oil fields, in the north of the terrace. In conformity with discovering the particularities, it is possible to say that the prospects of oil and gas bearing in the Norwegian Sea are primarilyt related to the Halten Terrace and the Vøring and Møre basins, especially the territories situated at the boundary of the two basins, where it is possible to discover large hydrocarbon accumulations like the Ormen-Lange field, because the Paleocene-Upper Cretaceous productive turbidite thick at the boundary of these basins is on the continental slope, which is considered promising a priori.

  5. Chapter 44: Geology and petroleum potential of the Lincoln Sea Basin, offshore North Greenland

    USGS Publications Warehouse

    Sorensen, K.; Gautier, D.; Pitman, J.; Ruth, Jackson H.; Dahl-Jensen, T.

    2011-01-01

    A seismic refraction line crossing the Lincoln Sea was acquired in 2006. It proves the existence of a deep sedimentary basin underlying the Lincoln Sea. This basin appears to be comparable in width and depth to the Sverdrup Basin of the Canadian Arctic Islands. The stratigraphy of the Lincoln Sea Basin is modelled in analogy to the Sverdrup Basin and the Central Spitsbergen Basin, two basins between which the Lincoln Sea intervened before the onset of seafloor spreading in the Eurasian Basin. The refraction data indicates that the Lincoln Sea Basin is capped by a kilometre-thick, low-velocity layer, which is taken to indicate an uplift history similar to, or even more favourable than, the fairway part of the Sverdrup Basin. Tectonic activity in the Palaeogene is likely to constitute the major basin scale risk. We conclude that the Lincoln Sea Basin is likely to be petroliferous and contains risked resources on the order of 1 ?? 109 barrels of oil, to which comes an equivalent amount of (associated and nonassociated) gas. ?? 2011 The Geological Society of London.

  6. Does Arctic sea ice reduction foster shelf-basin exchange?

    PubMed

    Ivanov, Vladimir; Watanabe, Eiji

    2013-12-01

    The recent shift in Arctic ice conditions from prevailing multi-year ice to first-year ice will presumably intensify fall-winter sea ice freezing and the associated salt flux to the underlying water column. Here, we conduct a dual modeling study whose results suggest that the predicted catastrophic consequences for the global thermohaline circulation (THC), as a result of the disappearance of Arctic sea ice, may not necessarily occur. In a warmer climate, the substantial fraction of dense water feeding the Greenland-Scotland overflow may form on Arctic shelves and cascade to the deep basin, thus replenishing dense water, which currently forms through open ocean convection in the sub-Arctic seas. We have used a simplified model for estimating how increased ice production influences shelf-basin exchange associated with dense water cascading. We have carried out case studies in two regions of the Arctic Ocean where cascading was observed in the past. The baseline range of buoyancy-forcing derived from the columnar ice formation was calculated as part of a 30-year experiment of the pan-Arctic coupled ice-ocean general circulation model (GCM). The GCM results indicate that mechanical sea ice divergence associated with lateral advection accounts for a significant part of the interannual variations in sea ice thermal production in the coastal polynya regions. This forcing was then rectified by taking into account sub-grid processes and used in a regional model with analytically prescribed bottom topography and vertical stratification in order to examine specific cascading conditions in the Pacific and Atlantic sectors of the Arctic Ocean. Our results demonstrate that the consequences of enhanced ice formation depend on geographical location and shelf-basin bathymetry. In the Pacific sector, strong density stratification in slope waters impedes noticeable deepening of shelf-origin water, even for the strongest forcing applied. In the Atlantic sector, a 1.5x increase of

  7. The Gela Basin pockmark field in the strait of Sicily (Mediterranean Sea): chemosymbiotic faunal and carbonate signatures of postglacial to modern cold seepage

    NASA Astrophysics Data System (ADS)

    Taviani, M.; Angeletti, L.; Ceregato, A.; Foglini, F.; Froglia, C.; Trincardi, F.

    2013-07-01

    The geo-biological exploration of a pockmark field located at ca. 800 m below sea level in the Gela basin (Strait of Sicily, Central Mediterranean) provided a relatively diverse chemosymbiotic community and methane-imprinted carbonates. To date, this is the first occurrence of such a type of specialised deep-water cold-seep communities recorded from this key region, before documented in the Mediterranean as rather disjunct findings in its eastern and westernmost basins. The thiotrophic chemosymbiotic organisms recovered from this area include empty tubes of the vestimentiferan Lamellibrachia sp., loose and articulated shells of lucinids (Lucinoma kazani, Myrtea amorpha), vesicomyids (Isorropodon perplexum), and gastropods (Taranis moerchii). A callianassid decapod (Calliax sp.) was consistently found alive in large numbers in the pockmark mud. Their post-mortem calcified parts mixed with molluscs and subordinately miliolid foraminifers form a distinct type of skeletal assemblage. Carbonate concretions display δ13C values as low as -40‰ PDB suggesting the occurrence of light hydrocarbons in the seeping fluids. Since none of the truly chemosymbiotic organisms was found alive, although their skeletal parts appear at times very fresh, some specimens have been AMS-14C dated to shed light on the historical evolution of this site. Lamellibrachiav and Lucinoma are two of the most significant chemosymbiotic taxa reported from various Mediterranean cold seep sites (Alboran Sea and Eastern basin). Specimens from station MEDCOR78 (pockmark #1, Lat. 36°46´10.18" N, Long. 14°01´31.59" E, 815 m below sea level) provided ages of 11736 ± 636 yr cal BP (Lamellibrachia sp.), and 9609.5 ± 153.5 yr cal BP (L. kazani). One shell of M. amorpha in core MEDCOR81 (pockmark #6, Lat 36°45´38.89" N, Long 14°00´07.58" E, 822 m below sea level) provided a sub-modern age of 484 ± 54 yr cal BP. These ages document that fluid seepage at this pockmark site has been episodically

  8. Effects of large sea-level variations in connected basins: the Dacian - Black Sea system of the Eastern Paratethys

    NASA Astrophysics Data System (ADS)

    Munteanu, I.; Matenco, L.; Dinu, C.; Cloetingh, S.

    2012-04-01

    Sea-level changes provide an important control on the interplay between accommodation space and sediment supply, in particular for shallow-water basins where the available space is limited. Sediment exchange between connected basins separated by a subaqueous sill (bathymetric threshold) is still not well understood. When sea-level falls below the bathymetric level of this separating sill, the shallow-water basin evolution is controlled by its erosion and rapid fill. Once this marginal basin is filled, the sedimentary depocenter shifts to the open marine basin (outward shift). With new accommodation space created during the subsequent sea-level rise, sediment depocenter shifts backwards to the marginal basin (inward shift). This new conceptual model is tested here in the context of Late Miocene to Quaternary evolution of the open connection between Dacian and Black Sea basins. By the means of seismic sequence stratigraphic analysis of the Miocene-Pliocene evolution of this Eastern Paratethys domain, this case study demonstrates these shifts in sedimentary depocenter between basins. An outward shift occurs with a delay that corresponds to the time required to fill the remaining accommodation space in the Dacian Basin below the sill that separates it from the Black Sea. This study provides novel insight on the amplitude and sedimentary geometry of the Messinian Salinity Crisis (MSC) event in the Black Sea. A large (1.3 - 1.7km) sea-level drop is demonstrated by quantifying coeval sedimentation patterns that change to mass-flows and turbiditic deposits in the deep-sea part of this main sink. The post-MSC sediment routing continued into the present-day pattern of Black Sea rivers discharge.

  9. Evolution history of the Heuksan Basin, a continental rift basin in the Yellow Sea

    NASA Astrophysics Data System (ADS)

    Yoon, S.; Kim, G.; Park, M.

    2011-12-01

    This study focuses on the establishment of evolutionary framework of the Heuksan Basin regions located on the southwestern part of the concession block III of the Korean offshore in the Yellow Sea. Three fault-bounded sub-basins (SB-1, SB-2, and SB-3) are recognized on the basis of topographic map of acoustic basement, which are generally in asymmetric half-graben geometry trending WNW-ESE. The axial lengths of the sub-basins are generally less than 80 km in axial length and 20 km in width. The acoustic basement occurs at around 0.6 to 0.8 s twt bsl in generally, locally much deeper at about 2.4 s twt bsl in the deepest part of the sub-basins, and it is correlated with the Upper Paleozoic to Lower Mesozoic sequence of thick micritic limestones overlying major clastic cycles with thin coals. In the sedimentary succession, two erosional surfaces (ES-1 and ES-2) are identified based on the interpretation of truncated geometries and lap-out patterns, which provide three stratigraphic units (SU-1, SU-2, and SU-3). During the Late Cretaceous to Oligocene the basin had opened by NE-SW extension or transtension. By this tectonic movement, WNW-ESE trending sub-basins with an array of listric normal faults were formed. Until the cessation of the opening, the wedge-shaped syn-rift unit (SU-1) infilled the depressions of the rift basins. In the Late Oligocene to Early Miocene time the extensional or transtensional tectonic movement of the Heuksan Basin region was aborted or partly inverted into compressional or transpressional regime. By this tectonic movement, acoustic basement and syn-rift unit (SU-1) might have uplifted, and have experienced a regional planation process. Topographic irregularities were removed by erosion and infilling process. SU-1 might have formed during this period in the localized topographic lows of the basins. Subaerial to shallow-marine planation process on the slightly folded and uplifted SU-1during subsequent tectonic inversion in the Early Miocene

  10. Groundwater Availability Within the Salton Sea Basin Final Report

    SciTech Connect

    Tompson, A; Demir, Z; Moran, J; Mason, D; Wagoner, J; Kollet, S; Mansoor, K; McKereghan, P

    2008-01-11

    It is widely recognized that increasing demands for water in Southern California are being affected by actions to reduce and redirect the amount of water imported from the Colorado River. In the Imperial Valley region, for example, import reductions will not only affect agricultural users but also could produce significant collateral impacts on the level and quality of water in the Salton Sea, its regional ecology, or even the long term air quality in the greater basin. The notion of using groundwater in the Imperial Valley as an additional source for agricultural or domestic needs, energy production, or Salton Sea restoration efforts, so as to offset reductions in imported water, is not a new concept. Even though it has been discussed recently (e.g., LLNL, 2002), the idea goes back, in part, to several studies performed by the US Department of Interior and other agencies that have indicated that there may be substantial, usable amounts of groundwater in some portions of the Imperial Valley. It has been estimated, for example, that between 1.1 and 3 billion acre-feet (AF) of groundwater lie within the extended, deep basin underlying the valley and Salton Sea region, even though much of it may be unrecoverable or too poor in its quality (Imperial County, 1997). This is a significant volume with respect to the total annual precipitation volume received in California, whose average is close to 200 million (or 0.2 billion) AF per year (DWR, 1998), and especially with respect to the total annual precipitation received in the Salton Sea watershed itself, which we estimate (Appendix A) to be approximately 2.5 million acre feet (MAF) per year. Clearly, a thorough appraisal of the groundwater resources in the Imperial Valley and Salton Sea region--i.e., an assessment of their overall physical availability--will be needed to determine how they can be used and managed to suit new or redirected demands in the region. Development of an improved or updated groundwater assessment

  11. Modelling the Baltic Sea as thirteen sub-basins with vertical resolution

    NASA Astrophysics Data System (ADS)

    Omstedt, Anders

    1990-03-01

    A mathematical model of the Baltic Sea is presented and explored. The model divides the Baltic Sea into 13 sub-basins. The dynamics in each sub-basin is reduced to a one dimensional boundary layer problem with vertical mean velocities based upon in- and outflows from surrounding basins. The turbulent exchange coefficients are calculated using a two-equation model of turbulence. The boundary conditions consider wind stress as well as the heat exchange between water and air. Sea ice is neglected in the model; instead, the water temperature is kept at the freezing point when the temperature is below freezing. The model is tested against observations from the severe sea ice winter 1986/87 and found to simulate the surface water temperature reasonably in all sub-basins during the whole winter. The thermal response due to sea ice has, however, to be considered in some sub-basins, particularly during spring warming.

  12. Thermal evolution of a rift basin: The Tyrrhenian Sea

    NASA Astrophysics Data System (ADS)

    1989-04-01

    Existing geological and geophysical data support the view that the coming of the Tyrrhenian Sea was by rifting of a formerly continuous continental lithosphere, which began in upper Miocene on the upper Sardinian margin and migrated southeastward to the Calabria margin. Heat flow across the Tyrrhenian Sea shows a pronounced asymmetry, from about 50-70 mW m-2 over the Sardinian margin, to more than 150 mW m-2 over its southeastern margin off southern Italy and Calabria. In this study we use the newly acquired data from Ocean Drilling Program Leg 107, heat flow, seismic velocity, and bathymetric data to constrain a group of models that supposes the Tyrrhenian Sea opened by detachment of a formerly continuous lithosphere along a southeastern facing, low-angle normal fault. Specific models tested include (1) the Wernicke model, in which thinning and extension of the continental lithosphere are supposed to be accomplished by ``simple shear'' along a large-scale, gently dipping detachment fault zone which cut through the entire lithosphere, and (2) the delamination model, in which the low-angle detachment fault is supposed to cut only the upper and middle crust but to merge subhorizontally into the lower crust, below which concurrent pure shear may occur. A versatile, two-dimensional finite element procedure is used to evaluate the tectonic and thermal evolution of these models, and the results are compared with observations to test the validity of the models. Delamination models with large pure shear components in the lower lithosphere and the Wernicke model predict heat flow within +/-1 σ of the measurements. The Wernicke model, however, predicts a basin configuration much too deep in comparison with bathymetry and a subbasinal lithospheric thickness substantially different from Rayleigh wave dispersion results. The delamination model with a large component of pure shear in the subbasinal lower lithosphere, on the other hand, predicts satisfactorily both the

  13. Thermal evolution of a rift basin: The Tyrrhenian Sea

    NASA Astrophysics Data System (ADS)

    Wang, Chi-Yuen; Hwang, Win-Tsuang; Shi, Yaolin

    1989-04-01

    Existing geological and geophysical data support the view that the opening of the Tyrrhenian Sea was by rifting of a formerly continuous continental lithosphere, which began in upper Miocene on the upper Sardinian margin and migrated southeastward to the Calabria margin. Heat flow across the Tyrrhenian Sea shows a pronounced asymmetry, from about 50-70 mW m-2 over the Sardinian margin, to more than 150 mW m-2 over its southeastern margin off southern Italy and Calabria. In this study we use the newly acquired data from Ocean Drilling Program Leg 107, heat flow, seismic velocity, and bathymetric data to constrain a group of models that supposes the Tyrrhenian Sea opened by detachment of a formerly continuous lithosphere along a southeastern facing, low-angle normal fault. Specific models tested include (1) the Wernicke model, in which thinning and extension of the continental lithosphere are supposed to be accomplished by "simple shear" along a large-scale, gently dipping detachment fault zone which cut through the entire lithosphere, and (2) the delamination model, in which the low-angle detachment fault is supposed to cut only the upper and middle crust but to merge subhorizontally into the lower crust, below which concurrent pure shear may occur. A versatile, two-dimensional finite element procedure is used to evaluate the tectonic and thermal evolution of these models, and the results are compared with observations to test the validity of the models. Delamination models with large pure shear components in the lower lithosphere and the Wernicke model predict heat flow within ±1σ of the measurements. The Wernicke model, however, predicts a basin configuration much too deep in comparison with bathymetry and a subbasinal lithospheric thickness substantially different from Rayleigh wave dispersion results. The delamination model with a large component of pure shear in the subbasinal lower lithosphere, on the other hand, predicts satisfactorily both the bathymetry

  14. Modes of sedimentary basin formation in the north-eastern Black Sea

    NASA Astrophysics Data System (ADS)

    Stephenson, Randell; Starostenko, Vitaly; Sydorenko, Grygoriy; Yegorova, Tamara

    2016-04-01

    The Greater Caucasus and Black Sea sedimentary basins developed in a Mesozoic back-arc setting, the former older than the latter (Jurassic v. Cretaceous). Compressional shortening of the former and accompanying ongoing development of marginal basin depocentres in the north-eastern Black Sea - which is closely tied to the formation of the Crimea-Greater Caucasus orogen - is a Cenozoic phenomenon, starting in the Eocene and proceeding until the present day. Recently, the sedimentary basin/crust/lithosphere geometry of the study area has been characterised across a range of scales using regional seismic reflection profiling, long-offset refraction/wide-angle reflection profiling and local earthquake tomography. These provide a new integrated image of the present-day crustal structure and sedimentary basin architecture of the northern margin of the eastern Black Sea, north across the Azov Sea and provide evidence of the deeper expression of sedimentary basins and the processes controlling the geometry of their inversion during the Cenozoic. It is inferred that the Greater Caucasus paleo-Basin, lying stratigraphically below the Black Sea and younger sedimentary successions, extends further to the west than previously known. This basin has significant thickness in the area between the Azov and Black seas and probably forms the deeper core of the Crimea-Caucasus inversion zone. The Crimea-Greater Caucasus orogenic belt is the expression of "basin inversion" of the Jurassic Greater Caucasus paleo-Basin, the degree of inversion of which varies along strike. The Greater Caucasus foredeep basins - Indolo-Kuban and Sorokin-Tuapse troughs -represent syn-inversional marginal troughs to the main inversion zone. The Shatsky Ridge - the northern flank of the main East Black Sea Basin - may also be mainly a syn-inversional structure, underlain by a blind thrust zone expressed as a northward dipping zone of seismicity on the northern margin of the eastern Black Sea.

  15. Pulsed basin development on northern margin of South China Sea

    SciTech Connect

    Ru, K.; Pigott, J.D.

    1987-05-01

    Detailed analysis of the geothermal gradients, structural architecture, genetic stratigraphy, and subsidence rate history of the sedimentary basins on the northern margin of the South China Sea (NMSC) reveal three temporally distinct but regionally correlative tectonic extensional episodes. The timing of these pulsed episodes of basin development are: Episode One, Late Cretaceous to Paleocene; Episode Two, late Eocene to early Oligocene; and Episode Three, middle Miocene. Each initiating episode on the NMSC is characterized by an ephemeral (< 10 m.y.) increase in heat flow (> 3 HFU), formation of regionally en echelon grabens or half-grabens, ensuing transgression, and high subsidence rate (> 50 m/m.y.). Trends of basin boundaries and major fault trends evolved from predominantly northeast for Episode One, to northeast and east-west for Episode Two, and to northwest and east-west and for Episode Three. Tectonically, the northeast and east-west trends resulted primarily from rifting along northwest and north-south extensional directions, respectively. The orientation, sense of displacement and time of activation of the Red River fault, Vietnam fracture zone, and the northeast-east-west and northwest-east-west multiple sets of fractures may be explained as responses to episodic changes in the regional stress field utilizing the guidance of inherited zones of crustal weakness. The timing and extent of the hydrocarbon maturation, reservoir development, and stratigraphic-structural closure in the NMSC were directly affected by this pulsed tectonic activity. Therefore, exploration strategies based purely upon the NMSC being a passive rifted margin are both inappropriate and misleading.

  16. Retrieval of eddy dynamics from SMOS sea surface salinity measurements in the Algerian Basin (Mediterranean Sea)

    NASA Astrophysics Data System (ADS)

    Isern-Fontanet, Jordi; Olmedo, Estrella; Turiel, Antonio; Ballabrera-Poy, Joaquim; García-Ladona, Emilio

    2016-06-01

    The circulation in the Algerian Basin is characterized by the presence of fresh-core eddies that propagate along the coast or at distances between 100 and 200 km from the coast. Enhancements in the processing of the Soil Moisture and Ocean Salinity (SMOS) data have allowed to produce, for the first time, satellite sea surface salinity (SSS) maps in the Mediterranean Sea that capture the signature of Algerian eddies. SMOS data can be used to track them for long periods of time, especially during winter. SMOS SSS maps are well correlated with in situ measurements although the former has a smaller dynamical range. Despite this limitation, SMOS SSS maps capture the key dynamics of Algerian eddies allowing to retrieve velocities from SSS with the correct sign of vorticity.

  17. Lower crustal flow and the role of shear in basin subsidence: An example from the Dead Sea basin

    USGS Publications Warehouse

    Al-Zoubi, A.; ten Brink, U.

    2002-01-01

    We interpret large-scale subsidence (5-6 km depth) with little attendant brittle deformation in the southern Dead Sea basin, a large pull-apart basin along the Dead Sea transform plate boundary, to indicate lower crustal thinning due to lower crustal flow. Along-axis flow within the lower crust could be induced by the reduction of overburden pressure in the central Dead Sea basin, where brittle extensional deformation is observed. Using a channel flow approximation, we estimate that lower crustal flow would occur within the time frame of basin subsidence if the viscosity is ??? 7 ?? 1019 - 1 ?? 1021 Pa s, a value compatible with the normal heat flow in the region. Lower crustal viscosity due to the strain rate associated with basin extension is estimated to be similar to or smaller than the viscosity required for a channel flow. However, the viscosity under the basin may be reduced to 5 ?? 1017 - 5 ?? 1019 Pa s by the enhanced strain rate due to lateral shear along the transform plate boundary. Thus, lower crustal flow facilitated by shear may be a viable mechanism to enlarge basins and modify other topographic features even in the absence of underlying thermal anomalies. ?? 2002 Elsevier Science B.V. All rights reserved.

  18. Present state of the Aral Sea: diverging physical and biological characteristics of the residual basins

    PubMed Central

    Izhitskiy, A. S.; Zavialov, P. O.; Sapozhnikov, P. V.; Kirillin, G. B.; Grossart, H. P.; Kalinina, O. Y.; Zalota, A. K.; Goncharenko, I. V.; Kurbaniyazov, A. K.

    2016-01-01

    Latest data on the hydrophysical and biological state of the residual basins of the Aral Sea are presented and compared. Direct, quasi-simultaneous observations were carried out in the central part of the Western Large Aral Sea, the northern extremity of the Large Aral known as Chernyshev Bay, Lake Tshchebas, and the Small Aral Sea in October 2014. The Large Aral Sea and Lake Tshchebas transformed into hyperhaline water bodies with highly special taxocene structure. The Small Aral Sea was a relatively diverse brackish ecosystem, which was rather similar to the pre-desiccation environment. The Small Aral Sea and Lake Tshchebas exhibited a fully-mixed vertical structure, whereas the Western Large Aral Sea was strongly stratified. Our data show that during desiccation, different parts of the Aral Sea experienced different environmental conditions, resulting in qualitative and quantitative differences in the physical and biological regimes among the different residual basins. PMID:27032513

  19. Present state of the Aral Sea: diverging physical and biological characteristics of the residual basins

    NASA Astrophysics Data System (ADS)

    Izhitskiy, A. S.; Zavialov, P. O.; Sapozhnikov, P. V.; Kirillin, G. B.; Grossart, H. P.; Kalinina, O. Y.; Zalota, A. K.; Goncharenko, I. V.; Kurbaniyazov, A. K.

    2016-04-01

    Latest data on the hydrophysical and biological state of the residual basins of the Aral Sea are presented and compared. Direct, quasi-simultaneous observations were carried out in the central part of the Western Large Aral Sea, the northern extremity of the Large Aral known as Chernyshev Bay, Lake Tshchebas, and the Small Aral Sea in October 2014. The Large Aral Sea and Lake Tshchebas transformed into hyperhaline water bodies with highly special taxocene structure. The Small Aral Sea was a relatively diverse brackish ecosystem, which was rather similar to the pre-desiccation environment. The Small Aral Sea and Lake Tshchebas exhibited a fully-mixed vertical structure, whereas the Western Large Aral Sea was strongly stratified. Our data show that during desiccation, different parts of the Aral Sea experienced different environmental conditions, resulting in qualitative and quantitative differences in the physical and biological regimes among the different residual basins.

  20. A comparison of the South China Sea and Canada Basin: two small marginal ocean basins with hyper-extended margins and central zones of sea-floor spreading.

    NASA Astrophysics Data System (ADS)

    Li, L.

    2015-12-01

    Both the South China Sea and Canada Basin preserve oceanic spreading centres and adjacent passive continental margins characterized by broad COT zones with hyper-extended continental crust. We have investigated the nature of strain accommodation in the regions immediately adjacent to the oceanic spreading centres in these two basins using 2-D backstripping subsidence reconstructions, coupled with forward modelling constrained by estimates of upper crustal extensional faulting. Modelling is better constrained in the South China Sea but our results for the Beaufort Sea are analogous. Depth-dependent extension is required to explain the great depth of both basins because only modest upper crustal faulting is observed. A weak lower crust in the presence of high heat flow is suggested for both basins. Extension in the COT may continue even after sea-floor spreading has ceased. The analogous results for the two basins considered are discussed in terms of (1) constraining the timing and distribution of crustal thinning along the respective continental margins, (2) defining the processes leading to hyper-extension of continental crust in the respective tectonic settings and (3) illuminating the processes that control hyper-extension in these basins and more generally.

  1. Deep Water Mass Circulation in the Alboran Basin. Measurements - January to April 1982. ALBORAN II,

    DTIC Science & Technology

    1987-09-01

    Informes Tecnicos Instituto Espafiol de Oceanografia 24 1984. Ma- drid, Spain. Inst. Espanol de Oceanografia . Alcala, 27, 1984: 159-167. LACOMBE, H...18-21 October 1983, Informes Tecnicos Instituto Espafiol de Oceanografia 24 1984. Madrid, Spain. Inst. Espanol de Oceanografia . Alcala, 27, 1984

  2. Can the South China Sea tell us anything about Canada Basin?

    NASA Astrophysics Data System (ADS)

    Stephenson, Randell; Li, Lu

    2016-04-01

    The Canada Basin (a sub-basin within the Amerasia Basin) and the South China Sea both preserve oceanic spreading centres and adjacent passive continental margins characterised by broad continent-ocean transition zones with hyper-extended continental crust. There are indications that hyper-extension in the South China Sea occurred mainly as a result of flow within a weak lower crustal layer and that it occurred both before and after plate break-up and the onset of ocean lithosphere formation at the sea-floor spreading axis. Available geophysical data from Canada Basin permit similar inferences. Both basins are about the same size and the oceanic segment in both is about the same size. Seafloor spreading in the South China Sea took place in the Cenozoic whereas in Canada Basin it is widely believed to have occurred during the Cretaceous. Widespread magmatism expressed as the High Arctic Large Igneous Province (HALIP) may or may not have played an intrinsic, linked, role in Canada Basin formation. No similar LIP is associated with the South China Sea although one mechanism proposed to have driven its formation is ascribed to mantle plume activity in its northernmost part. More conventionally the mechanism of opening of the South China Sea is considered to be "passive" rather than "active", related to plate reconfigurations in the southeast Asia region linked or not linked to the nearby collision of India and Eurasia and/or subduction of a "proto-South China Sea". The driving mechanism for opening of Canada Basin is poorly discussed in the literature but is generally ascribed to paleo-tectonic plate reconfigurations and subduction in the northern Pacific (Eurasia-North America plates) region in the Mesozoic. Can the South China Sea tell us anything about Canada Basin in terms of the pre-existing lithosphere of each and the geodynamic processes leading to its hyper-extension and eventual break-up?

  3. Environmental selection of protistan plankton communities in hypersaline anoxic deep-sea basins, Eastern Mediterranean Sea

    PubMed Central

    Filker, Sabine; Stock, Alexandra; Breiner, Hans-Werner; Edgcomb, Virginia; Orsi, William; Yakimov, Michail M; Stoeck, Thorsten

    2013-01-01

    High salt concentrations, absence of light, anoxia, and high hydrostatic pressure make deep hypersaline anoxic basins (DHABs) in the Eastern Mediterranean Sea one of the most polyextreme habitats on Earth. Taking advantage of the unique chemical characteristics of these basins, we tested the effect of environmental selection and geographic distance on the structure of protistan communities. Terminal restriction fragment length polymorphism (T-RFLP) analyses were performed on water samples from the brines and seawater/brine interfaces of five basins: Discovery, Urania, Thetis, Tyro, and Medee. Using statistical analyses, we calculated the partitioning of diversity among the ten individual terminal restriction fragment (T-RF) profiles, based on peak abundance and peak incidence. While a significant distance effect on spatial protistan patterns was not detected, hydrochemical gradients emerged as strong dispersal barriers that likely lead to environmental selection in the DHAB protistan plankton communities. We identified sodium, magnesium, sulfate, and oxygen playing in concerto as dominant environmental drivers for the structuring of protistan plankton communities in the Eastern Mediterranean DHABs. PMID:23239531

  4. Assessment of Undiscovered Oil and Gas Resources of the Red Sea Basin Province

    USGS Publications Warehouse

    ,

    2010-01-01

    The U.S. Geological Survey estimated mean volumes of 5 billion barrels of undiscovered technically recoverable oil and 112 trillion cubic feet of recoverable gas in the Red Sea Basin Province using a geology-based assessment methodology.

  5. Petroleum system of the Shelf Rift Basin, East China Sea

    SciTech Connect

    Cunningham, A.C.; Armentrout, J.M.; Prebish, M.

    1996-12-31

    The Tertiary section of the Oujioang and Quiontang Depressions of the East China Sea Basin consists of at least eight rift-related depositional sequences identified seismically by regionally significant onlap and truncation surfaces. These sequences are calibrated by several wells including the Wenzhou 6-1-1 permitting extrapolation of petroleum system elements using seismic facies analysis. Gas and condensate correlated to non-marine source rocks and reservoired in sandstone at the Pinghu field to the north of the study area provides an known petroleum system analogue. In the Shelf Rift Basin, synrift high-amplitude parallel reflections within the graben axes correlate with coaly siltstone strata and are interpreted as coastal plain and possibly lacustrine facies with source rock potential. Synrift clinoform seismic facies prograding from the northwest footwall correlate with non-marine to marginal marine conglomerate, sandstone and siltstone, and are interpreted as possible delta or fan-delta facies with reservoir potential although porosity and permeability is low within the Wenzhou 6-1-1 well. Post-rift thermal sag sequences are characterized by parallel and relatively continuous seismic reflections and locally developed clinoform packages. These facies correlate with porous and permeable marine sandstone and siltstone. Shales of potential sealing capacity occur within marine flooding intervals of both the synrift and post-rift sequences. Traps consist of differentially rotated synrift fill, and post-rift inversion anticlines. Major exploration risk factors include migration from the synrift coaly source rocks to the post-rift porous and permeable sandstones, and seismic imaging and drilling problems associated with extensive Tertiary igneous intrusions.

  6. Petroleum system of the Shelf Rift Basin, East China Sea

    SciTech Connect

    Cunningham, A.C.; Armentrout, J.M.; Prebish, M. )

    1996-01-01

    The Tertiary section of the Oujioang and Quiontang Depressions of the East China Sea Basin consists of at least eight rift-related depositional sequences identified seismically by regionally significant onlap and truncation surfaces. These sequences are calibrated by several wells including the Wenzhou 6-1-1 permitting extrapolation of petroleum system elements using seismic facies analysis. Gas and condensate correlated to non-marine source rocks and reservoired in sandstone at the Pinghu field to the north of the study area provides an known petroleum system analogue. In the Shelf Rift Basin, synrift high-amplitude parallel reflections within the graben axes correlate with coaly siltstone strata and are interpreted as coastal plain and possibly lacustrine facies with source rock potential. Synrift clinoform seismic facies prograding from the northwest footwall correlate with non-marine to marginal marine conglomerate, sandstone and siltstone, and are interpreted as possible delta or fan-delta facies with reservoir potential although porosity and permeability is low within the Wenzhou 6-1-1 well. Post-rift thermal sag sequences are characterized by parallel and relatively continuous seismic reflections and locally developed clinoform packages. These facies correlate with porous and permeable marine sandstone and siltstone. Shales of potential sealing capacity occur within marine flooding intervals of both the synrift and post-rift sequences. Traps consist of differentially rotated synrift fill, and post-rift inversion anticlines. Major exploration risk factors include migration from the synrift coaly source rocks to the post-rift porous and permeable sandstones, and seismic imaging and drilling problems associated with extensive Tertiary igneous intrusions.

  7. [Species composition and distribution of foraminifers in the Deryugin Basin (Sea of Okhotsk)].

    PubMed

    Khusid, T A; Domanov, M M; Svinininnikov, A M

    2006-01-01

    Analysis of the composition and quantitative distribution of foraminifers in bathyal sediments collected at 14 stations in the Deryugin Basin and at 11 stations in other regions of the Sea of Okhotsk, Sea of Japan, and North Pacific demonstrated specific foraminifer complex in the basin at depths from 1650 to 1800 m associated with cold barite/methane seeps. Oligomixed biocenosis with prevailing agglutinated foraminifers and Saccorhiza ramosa as the dominant was shown to develop in these zones.

  8. Selective erosion by gravity flows in the deep-sea Lofoten Basin, Norwegian Sea

    NASA Astrophysics Data System (ADS)

    Sverre Laberg, Jan; Forwick, Matthias; Johannessen, Hilde B.; Ivanov, Mikhail; Kenyon, Neil H.; Vorren, Tore O.

    2010-05-01

    Deposits from gravity flows form a substantial part of the Lofoten Basin stratigraphy, a deep-water basin offshore Norway. This includes glacigenic debris flows from the shelf edge/upper slope, sandy turbidites from canyon - channel systems and debris flow deposits from submarine landslides. Little is, however, known about the properties of the gravity flows and their interaction with the sea floor sediments. We present newly acquired deep-towed side-scan sonar data co-registered with sub-bottom profiles showing small and large-scale irregularities of the sea floor in two areas relatively recently affected by gravity flows. The first area is located at about 2700 m water depth and is part of the distal Andøya Slide. Here, three several km wide and about 25 m thick lensoid and acoustically transparent deposits with a slightly irregular relief are inferred to represent debris flow deposits from submarine landslides originating from the nearby continental slope. The seafloor both below the debris flows and between and not affected by the debris flows is irregular due to closed seafloor depressions. They occur randomly and with a variety of forms up to 1 km across, 500 m wide and some meters deep. The second area is the Lofoten Basin Channel near its termination at about 3200 m water depth, beyond which laterally extensive sheets of normal graded sand interbedded with thinner mud layers occur. Sea floor depressions appear in several morphological forms on the channel flanks. The largest is more than 1 km long, up to 250 m wide, some meters deep has its longest axis parallel to the flow direction. It becomes less distinct in the down-flow direction. Other features in this area include densely spaced longitudinal features. In both areas the irregular sea floor morphology is inferred to be flute marks (or scours) formed by erosive gravity flows. Erosion of channel flanks by turbidity currents is well known from other studies but is not commonly described from the most

  9. Three-dimensional modeling of pull-apart basins: implications for the tectonics of the Dead Sea Basin

    USGS Publications Warehouse

    Katzman, Rafael; ten Brink, Uri S.; Lin, Jian

    1995-01-01

    We model the three-dimensional (3-D) crustal deformation in a deep pull-apart basin as a result of relative plate motion along a transform system and compare the results to the tectonics of the Dead Sea Basin. The brittle upper crust is modeled by a boundary element technique as an elastic block, broken by two en echelon semi-infinite vertical faults. The deformation is caused by a horizontal displacement that is imposed everywhere at the bottom of the block except in a stress-free “shear zone” in the vicinity of the fault zone. The bottom displacement represents the regional relative plate motion. Results show that the basin deformation depends critically on the width of the shear zone and on the amount of overlap between basin-bounding faults. As the width of the shear zone increases, the depth of the basin decreases, the rotation around a vertical axis near the fault tips decreases, and the basin shape (the distribution of subsidence normalized by the maximum subsidence) becomes broader. In contrast, two-dimensional plane stress modeling predicts a basin shape that is independent of the width of the shear zone. Our models also predict full-graben profiles within the overlapped region between bounding faults and half-graben shapes elsewhere. Increasing overlap also decreases uplift near the fault tips and rotation of blocks within the basin. We suggest that the observed structure of the Dead Sea Basin can be described by a 3-D model having a large overlap (more than 30 km) that probably increased as the basin evolved as a result of a stable shear motion that was distributed laterally over 20 to 40 km.

  10. The Pre-Messinian Total Petroleum System of the Provence Basin, Western Mediterranean Sea

    USGS Publications Warehouse

    Pawlewicz, Mark

    2004-01-01

    The Provence Basin is in that portion of the western Mediterranean Sea that is deeper than 2 kilometers. The basin lies essentially beyond the outer continental shelf, between the countries of France, Italy, and Algeria, the Balearic Islands, and the islands of Sardinia and Corsica. It encompasses nearly 300,000 square kilometers and includes the Rhone River submarine fan on the continental slope of southern France. It is province 4068 in the World Energy study. A single, hypothetical, total petroleum system (TPS), the Pre-Messinian TPS (406801), was described for the Provence Basin. The designation hypothetical is used because there is no hydrocarbon production from the basin. The Provence Basin is a deep-water Tertiary rift basin in which the geothermal gradients vary regionally. The Red Sea Basin shares a similar geologic and thermal history with the rifted western Mediterranean Sea and was used as an analog to better understand the genesis of the Provence Basin and as a guide to estimating possible undiscovered amounts of hydrocarbons. For this assessment the basin was given a potential, at the mean, for undiscovered resources of 51 trillion cubic feet (1.4 trillion cubic meters) gas, 0.42 billion barrels oil, and 2.23 million barrels natural gas liquids.

  11. Avalonian crustal controls on basin evolution: implications for the Mesozoic basins of the southern North Sea

    NASA Astrophysics Data System (ADS)

    Smit, Jeroen; van Wees, Jan-Diederik; Cloetingh, Sierd

    2015-04-01

    Little is known of the Southern North Sea Basin's (SNSB) Pre-Permian basement due to a lack of outcrop and cores. The nature and structure of the East Avalonian crust and lithosphere remain even less constrained in the absence of deep seismic (refraction) lines. However, various studies have hinted at the importance of the Reactivation of the Early Carboniferous fault network during each consecutive Mesozoic and Cenozoic tectonic phase, demonstrating the key role of weak zones from the Early Carboniferous structural grain in partitioning of structural deformation and vertical basin motions at various scales. Although the older basin history and the basement attract increasing attention, the Pre-Permian tectonics of the SNSB remains little studied with most attention focused on the Permian and younger history. The strong dispersal of existing constraints requires a comprehensive study from Denmark to the UK, i.e. the East Avalonian microplate, bordered by the Variscan Rheïc suture, the Atlantic and Baltica. Based on an extensive literature study and the reinterpretation of publicly available data, linking constraints from the crust and mantle to stratigraphic-sedimentological information, we complement the map of Early Carboniferous rifting of East Avalonia and propose a new tectonic scenario. From the reinterpretation of the boundary between Avalonia and Baltica we propose a new outline for the Avalonian microplate with implications for the tectonics of the North German Basin. Furthermore, we highlight the nature and extent of the major crustal/lithospheric domains with contrasting structural behaviour and the major boundaries that separate them. Results shed light on the effects of long lived differences in crustal fabric that are responsible for spatial heterogeneity in stress and strain magnitudes and zonations of fracturing, burial history and temperature history. The geomechanical control of large crustal-scale fault structures will provide the constraints

  12. Structure and hydrocarbon potential of sedimentary basins of the far east marginal seas

    SciTech Connect

    Gnibidenko, H. ); Kononov, V. )

    1990-05-01

    Crustal structural of the Bering, Okhotsk Japan, East China, and South China marginal seas consists of continental plates and deep sea basins that are the elements of the lowermost order in the structure of transition zone from the Asia continent to the Pacific Ocean. Two stages are recognized in the crustal evolution of the northwest Pacific transition zone: (1) geosyncline development that began in the pre-Paleozoic and continues to the present within island arcs; and (2) quasiplatform stage that began in the late Cretaceous and continues to the Holocene within shelf plates. The continental margins of the Far East seas consist of Cenozoic terrigenous cover and pre-Cenozoic basement composed of geosyncline rock association. Normal faults control graben features in the basement and develop rift systems. Paleogene subcontinental formations make up the lowermost section of the cover. A major Oligocene-Holocene sequence (marine formations) overlies and smooths rough topography of the basement and creates giant sedimentary basins. Sediment thickness of the basins attains 10 km. Tectonic evolution of the marginal seas implies the shelf plates to be young platforms and deep-sea basins are believed to be parts of the Pacific thalassocraton fenced by island arcs. The tectonic criterion enables us to differ and grade the provinces according to a hydrocarbon potential. Nearly 100 promising sedimentary basins are presently known in the Bering, Okhotst Japan, East China, and South China seas. About ten basins have been identified as hydrocarbon resources. Deep-sea basins also look promising for hydrocarbons. All the economically significant hydrocarbon accumulations in the Far East marginal seas are attributed to the Cenozoic sediment cover. Major resources are concentrated in the Miocene and Pliocene terrigenous sequences composed of progradation facies within the shelf plates.

  13. Younger Dryas thermohaline circulation in the N-Atlantic: Irminger Sea versus Norwegian Sea Basin

    NASA Astrophysics Data System (ADS)

    Kuijpers, Antoon; Seidenkrantz, Marit-Solveig; Luise Knudsen, Karen; Knutz, Paul C.; Sicre, Marie-Alexandrine; Andresen, Camilla S.; Pearce, Christof

    2016-04-01

    ventilation (well) over 1900 m, which contrasts with more limited convection conditions in the Nordic Seas as signaled by Norwegian Sea Deep Water Overflow records from the Faroe-Shetland Channel gateway(9).We conclude that during the YD a steep SST gradient must have existed between the Irminger and Norwegian Sea basin, having resulted in an intensification of (zonal) atmospheric circulation and increased (westerly) storminess, which is documented as a characteristic European YD feature(10). References (1) Blindheim, J. et al. 2000. Deep-Sea Res. I 47,655-680 (2) Condron, A., Winsor, P. 2012. PNAS 109 (49), 19929-19933 (3) Löfverström, M. 2014. Clim. Past 10, 1453-1471 (4) Weinelt, M. et al. 1995. KNAW Verh. Nat. 1. R. 44, 109-116 (5) Knudsen, K.L. et al. 2004. Mar. Micropal. 50, 273-305 (6) Kuijpers, A. et al. 2003. Mar.Geo. 195, 109-129 (7) Knutz, P. et al. 2011. Paleoceanography 26 PA3204, doi:10.1029/2010PA002053 (8) Björck, S. et al. 2002. Geology 90, 427-430 (9) Kuijpers, A. et al. 1998. Mar.Geo. 152, 1-3, 75-99 (10) Renssen, H. et al. 1996. Clim. Dyn. 12, 813-824

  14. The Gela Basin pockmark field in the strait of Sicily (Mediterranean Sea): chemosymbiotic faunal and carbonate signatures of postglacial to modern cold seepage

    NASA Astrophysics Data System (ADS)

    Taviani, M.; Angeletti, L.; Ceregato, A.; Foglini, F.; Froglia, C.; Trincardi, F.

    2013-01-01

    The geo-biological exploration of a pockmark field located at ca. -800 m in the Gela basin (Strait of Sicily, Central Mediterranean) provided a relatively diverse chemosymbiotic community and methane-imprinted carbonates. To date, this is the first occurrence of such type of specialized deep-water cold-seep communities recorded from this key region, before documented in the Mediterranean as rather disjunct findings in its eastern and westernmost basins. The thiotrophic chemosymbiotic organisms recovered from this area include empty tubes of the vestimentiferan Lamellibrachia sp., loose and articulated shells of lucinids (Lucinoma kazani, Myrtea amorpha), vesicomyids (Isorropodon perplexum), and gastropods (Taranis moerchi). A callianassid decapod (Calliax sp.) was consistently found alive in large numbers in the pockmark mud. Their post-mortem calcified parts mixed with molluscs and subordinately miliolid foraminifers form a distinct type of skeletal assemblage (named DECAMOL). Carbonate concretions display δ13C values as low as -40 ‰ PDB suggesting the occurrence of light hydrocarbons in the seeping fluids. Since none of the truly chemosymbiotic organisms was found alive, although their skeletal parts appear at times very fresh, some specimens have been AMS-14C dated to shed light on the historical evolution of this site. Lamellibrachia and Lucinoma are two of the most significant chemosymbiotic taxa reported from various Mediterranean cold seep sites (Alboran Sea and Eastern basin). Specimens from station MEDCOR78 (pockmark#1, Lat 36°46´10.18´´ N, Long 14°01´31.59´´ E, -815 m) provided ages of 11 736 ± 636 yr cal BP (Lamellibrachia sp.), and 9609.5 ± 153.5 yr cal BP (L. kazani). One shell of M. amorpha in core MEDCOR81 (pockmark#6, Lat 36°45´38.89´´ N, Long 14°00´07.58´´ E, -822 m) provided a sub-modern age of 484 ± 54 yr cal BP. These ages document that fluid seepage at this pockmark site has been episodically sustaining thiotrophic

  15. Tectonic subsidence of the Zhu 1 Sub-basin in the Pearl River Mouth Basin, northern South China Sea

    NASA Astrophysics Data System (ADS)

    Tang, Xiaoyin; Yang, Shuchun; Zhu, Junzhang; Long, Zulie; Jiang, Guangzheng; Huang, Shaopeng; Hu, Shengbiao

    2017-01-01

    The Pearl River Mouth Basin, which is situated on the northern margin of the South China Sea, has attracted great attention not only because of its tectonic setting but also because of its abundant hydrocarbon resources. We have analyzed the Cenozoic tectonic subsidence history of 4 drilled wells and 43 artificial wells from the Zhu 1 Sub-basin of the Pearl River Mouth Basin by back-stripping, using newly interpreted seismic profiles. We also calculated the average tectonic sub-sidence rates of the four sags in the Zhu 1 Sub-basin. The rifting and post-rifting stages are separated by abrupt changes in the tectonic subsidence curves and average subsidence rates. In the eastern sags of the Zhu 1 Sub-basin, tectonic subsidence started to slow at ca. 30 Ma, compared with ca. 23.8 Ma in the western sags. This probably corresponds to the timing of break-up and suggests that rifting in the Pearl River Mouth Basin ended earlier in the eastern sags than in the western sags. Anomalously accelerated tectonic subsidence occurred at 17.5-16.4 Ma during the post-rifting stage, with average subsidence rates as high as 301.9 m/Myr. This distinguishes the Pearl River Mouth Basin from classical Atlantic passive continental marginal basins, which demonstrate exponentially decaying post-rift tectonic subsidence.

  16. A Rossby whistle: A resonant basin mode observed in the Caribbean Sea

    NASA Astrophysics Data System (ADS)

    Hughes, Chris W.; Williams, Joanne; Hibbert, Angela; Boening, Carmen; Oram, James

    2016-07-01

    We show that an important source of coastal sea level variability around the Caribbean Sea is a resonant basin mode. The mode consists of a baroclinic Rossby wave which propagates westward across the basin and is rapidly returned to the east along the southern boundary as coastal shelf waves. Almost two wavelengths of the Rossby wave fit across the basin, and it has a period of 120 days. The porous boundary of the Caribbean Sea results in this mode exciting a mass exchange with the wider ocean, leading to a dominant mode of bottom pressure variability which is almost uniform over the Grenada, Venezuela, and Colombia basins and has a sharp spectral peak at 120 day period. As the Rossby waves have been shown to be excited by instability of the Caribbean Current, this resonant mode is dynamically equivalent to the operation of a whistle.

  17. Bio-optical characteristics of Cariaco Basin (Caribbean Sea) waters

    NASA Astrophysics Data System (ADS)

    Lorenzoni, Laura; Hu, Chuanmin; Varela, Ramón; Arias, Glenda; Guzmán, Laurencia; Muller-Karger, Frank

    2011-04-01

    Bio-optical properties of marine waters of the Cariaco Basin (southeastern Caribbean Sea) were assessed monthly between 1995 and 2005 as part of the CARIACO Ocean Time Series program. Temporal changes in light quality and penetration were caused by seasonal variation in the concentration of three major optical constituents, namely phytoplankton, detrital particles, and colored dissolved organic matter (CDOM). All constituents showed higher absorption coefficients during the upwelling season (January-May) compared to the rainy season (June-November). Both the absorption coefficient due to CDOM ( ag(440)) and due to phytoplankton ( aph(440)) had similar contributions to total absorption of light during the upwelling season ( aph(440)=0.062±0.042 m -1, ag(440)=0.065±0.047 m -1). In contrast, ag(440) dominated light absorption during the rainy season ( aph(440)=0.017±0.011 m -1, ag(440)=0.057±0.031). This led to an overestimate in SeaWiFS-derived chlorophyll concentrations during the rainy season, of between 7% and 45%. The detrital component, ad(440), typically showed the smallest contribution ( ad(440)=0.021±0.014 m -1 during upwelling and 0.007±0.001 m -1 during the rainy season). There was no clear relationship between the various optically active components in time. During the upwelling season the chlorophyll-specific absorption coefficient, aph*(440), was nearly half the value observed during the rainy season due to changes in the package effect (explaining ˜40% of the variability) and in accessory pigment composition as a result of species succession (explaining ˜60% of the variability). The euphotic zone depth (depth of the 1% photosynthetic active radiation (PAR) level) was typically shallower during the upwelling season (36.7±12.3 m) than during the rainy season (47.9±13.5 m) due to the onset of a shallower and stronger phytoplankton bloom. During upwelling, the highest chlorophyll- a concentrations (Chl>1 mg m -3) were observed in the upper 25 m

  18. Basin-edge diapirism and updip salt flow in Zechstein of southern North Sea

    SciTech Connect

    Jenyon, M.K.

    1985-01-01

    Some unusual and interesting structural geometries have been recognized on seismic lines recorded in the United Kingdom sector of the southern Permian basin of the North Sea. They seem to be the result of diapirism at the northern edge of the (Upper Permian) Zechstein salt basin, and involve the preservation of a 75 km (47 mi) long prism of a younger Mesozoic sequence replaced elsewhere by the widespread Jurassic/Cretaceous late Kimmerian unconformity. It is suggested that the diapiric features described are due to the movement of salt toward the basin edge having been dammed by a change in facies from basinal halite to shelf lithologies over a short distance.

  19. Basin-edge diapirism and updip salt flow in Zechstein of southern North Sea

    SciTech Connect

    Jenyon, M.K.

    1985-12-01

    Some unusual and interesting structural geometries have been recognized on seismic lines recorded in the United Kingdom sector the southern Permian basin of the North Sea. They seem to be the result of diapirism at the northern edge of the (Upper Permian) Zechstein salt basin, and involve the preservation of a 75 km (47 mi) long prism of a younger Mesozoic sequence replaced elsewhere by the widespread Jurassic/Cretaceous late Kimmerian unconformity. It is suggested that the diapiric features described are due to the movement of salt toward the basin edge having been dammed by a change in facies from basinal halite to shelf lithologies over a short distance. 13 figures.

  20. Correlation of sea level falls interpreted from atoll stratigraphy with turbidites in adjacent basins

    SciTech Connect

    Lincoln, J.M. )

    1990-05-01

    Past sea levels can be derived from any atoll subsurface sediments deposited at or near sea level by determining the ages of deposition and correcting the present depths to the sediments for subsidence of the underlying edifice since the times of deposition. A sea level curve constructed by this method consists of discontinuous segments, each corresponding to a period of rising relative sea level and deposition of a discrete sedimentary package. Discontinuities in the sea level curve derived by this method correspond to relative sea level falls and stratigraphic hiatuses in the atoll subsurface. During intervals of relative sea level fall an atoll emerges to become a high limestone island. Sea level may fluctuate several times during a period of atoll emergence to become a high limestone island. Sea level may fluctuate several times during a period of atoll emergence without depositing sediments on top of the atoll. Furthermore, subaerial erosion may remove a substantial part of the depositional record of previous sea level fluctuations. For these reasons the authors must look to the adjacent basins to complement the incomplete record of sea level change recorded beneath atolls. During lowstands of sea level, faunas originally deposited near sea level on an atoll may be eroded and redeposited as turbidites in deep adjacent basins. Three such turbidites penetrated during deep-sea drilling at Sites 462 and 315 in the central Pacific correlate well with a late Tertiary sea level curve based on biostratigraphic ages and {sup 87}Sr/{sup 86}Sr chronostratigraphy for core from Enewetak Atoll in the northern Marshall Islands. Further drilling of the archipelagic aprons adjacent to atolls will improve the sea level history that may be inferred from atoll stratigraphy.

  1. Long-term sea-level fluctuations driven by ocean basin dynamics.

    PubMed

    Müller, R Dietmar; Sdrolias, Maria; Gaina, Carmen; Steinberger, Bernhard; Heine, Christian

    2008-03-07

    Earth's long-term sea-level history is characterized by widespread continental flooding in the Cretaceous period (approximately 145 to 65 million years ago), followed by gradual regression of inland seas. However, published estimates of the Late Cretaceous sea-level high differ by half an order of magnitude, from approximately 40 to approximately 250 meters above the present level. The low estimate is based on the stratigraphy of the New Jersey margin. By assimilating marine geophysical data into reconstructions of ancient ocean basins, we model a Late Cretaceous sea level that is 170 (85 to 270) meters higher than it is today. We use a mantle convection model to suggest that New Jersey subsided by 105 to 180 meters in the past 70 million years because of North America's westward passage over the subducted Farallon plate. This mechanism reconciles New Jersey margin-based sea-level estimates with ocean basin reconstructions.

  2. The impact of sea breeze under different synoptic patterns on air pollution within Athens basin.

    PubMed

    Mavrakou, Thaleia; Philippopoulos, Kostas; Deligiorgi, Despina

    2012-09-01

    Air quality in densely populated urban coastal areas is directly related to the coupling of the synoptic and the local scale flows. The dispersion conditions within Athens basin, under the influence of different meteorological forcings, lead to distinct spatio-temporal air pollution patterns. The aim of the current observational research is to identify and examine the effect of sea breeze under different atmospheric circulation patterns on air pollution levels for a one-year study period (2007). The study employs surface pressure maps, routine meteorological observations at two coastal sites and nitrogen monoxide (NO), nitrogen dioxide (NO(2)) and ozone (O(3)) concentrations from a network of four air quality stations within the Athens basin. A three-step methodology is applied that incorporates a set of criteria for classifying atmospheric circulation and identifying sea breeze events under each circulation pattern. Two types of sea breeze development are identified (pure sea breeze-PSB and modified sea breeze-MSB) with distinct characteristics. Sea breeze is found to develop more frequently under offshore compared to onshore and parallel to the shoreline background flows. Poor dispersion conditions (high nitrogen oxides-NO(x) and O(3) concentrations) are connected to the pure sea breeze cases and to those cases where sea breeze interacts with a moderate northerly flow during the warm period. The levels of NO(x) and O(3) for the northern Athens basin area are found to be significantly higher during the sea breeze days compared to the Etesian days. Regarding the diurnal variation of ozone for the sea breeze days, peak concentrations and higher intra-daily ranges are observed. Day-to-day pollution accumulation (build-up effect) is measured for O(3) at the northern stations in the Athens basin.

  3. Geology of Norton Basin and continental shelf beneath northwestern Bering Sea, Alaska

    SciTech Connect

    Fisher, M.A.; Patton, W.W. Jr.; Holmes, M.L.

    1982-03-01

    The rocks that floor the Norton basin and the northwestern Bering Sea are most likely of Precambrian and Paleozoic age, like those rocks that crop out around the basin. A maximum of 6.5 km of mainly Cenozoic strata lie over basement in the basin. On the basis of the geometry of reflections in seismic data, it is believed alluvial fans to be present deep in the basin and to border major basement fault blocks. These fans are the lowest units of the basin fill in many areas and consist of uppermost Cretaceous or lower Paleogene, possibly coal- and volcanic-rich rocks. Mainly clastic nonmarine sedimentary rocks overlie the fan deposits. The Neogene and Quaternary basin rocks apparently were deposited in a marine environment.

  4. The Holocene palaeogeography and relative sea level for two tidal basins of the German North Sea coast

    NASA Astrophysics Data System (ADS)

    Bungenstock, Friederike; Wartenberg, Wolfram; Mauz, Barbara; Freund, Holger; Frechen, Manfred; Weerts, Henk J. T.; Berner, Heinrich

    2014-05-01

    The response of coasts to global sea-level rise is highly variable. Knowledge of driving coastal parameters alongside the regional sea-level history is therefore indispensable when the response to global sea-level rise is to be assessed. Here, we study the Holocene relative sea-level of the south coast of the North Sea which is controlled by a number of very local parameters, as well as by regional glacio-isostatic adjustments. It is therefore crucial to restrict the data acquisition and evaluation to small coastal sections, ideally to single tidal basins, to minimize the sources of uncertainties (Bungenstock & Weerts 2010, 2012). We present data from two tidal basins, Langeoog and Jade Bay. For Langeoog a database derived from 600 cores, 68 km of Boomer seismic data, 33 radiocarbon ages and 8 OSL dates is available. (Bungenstock & Schäfer 2009, Mauz & Bungenstock 2007). For the Jade bay, the database comprises sedimentary markers, pollen and macro remains derived from 68 cores. The sedentary chronology is based on 54 radiocarbon ages and pollen constraints (Wartenberg & Freund 2011, Wartenberg et al. 2013). For both tidal basins the sedimentological record was interpreted in terms of the local paleogeographical development since about 7000 cal BP and its influence on the local relative sea-level curve. While the trend of the relative sea level is similar for both tidal basins, it shows a different altitude. The timing of the main marine transgression within the Langeoog area takes place ~3000 cal. BP whereas the sedimentological record of the Jade Bay shows two prominent transgressions, one for ~5000 cal. BP and one for ~3000 cal. BP. The Langeoog palaeo-environment is continuously characterised by marine influence. Within the Jade Bay two different palaeo-environments could be identified, documenting that from the West to the centre the landscape development in the Jade Bay was drainage driven feeding the associated fen peat with minerogenic water but being

  5. Acidification of the Mediterranean Sea from anthropogenic carbon penetration

    NASA Astrophysics Data System (ADS)

    Hassoun, Abed El Rahman; Gemayel, Elissar; Krasakopoulou, Evangelia; Goyet, Catherine; Abboud-Abi Saab, Marie; Guglielmi, Véronique; Touratier, Franck; Falco, Cédric

    2015-08-01

    This study presents an estimation of the anthropogenic CO2 (CANT) concentrations and acidification (ΔpH=pH2013-pHpre-industrial) in the Mediterranean Sea, based upon hydrographic and carbonate chemistry data collected during the May 2013 MedSeA cruise. The concentrations of CANT were calculated using the composite tracer TrOCA. The CANT distribution shows that the most invaded waters (>60 μmol kg-1) are those of the intermediate and deep layers in the Alboran, Liguro- and Algero-Provencal Sub-basins in the Western basin, and in the Adriatic Sub-basin in the Eastern basin. Whereas the areas containing the lowest CANT concentrations are the deep layers of the Eastern basin, especially those of the Ionian Sub-basin, and those of the northern Tyrrhenian Sub-basin in the Western basin. The acidification level in the Mediterranean Sea reflects the excessive increase of atmospheric CO2 and therefore the invasion of the sea by CANT. This acidification varies between -0.055 and -0.156 pH unit and it indicates that all Mediterranean Sea waters are already acidified, especially those of the Western basin where ΔpH is rarely less than -0.1 pH unit. Both CANT concentrations and acidification levels are closely linked to the presence and history of the different water masses in the intermediate and deep layers of the Mediterranean basins. Despite the high acidification levels, both Mediterranean basins are still highly supersaturated in calcium carbonate minerals.

  6. Basin Economic Allocation Model (BEAM): An economic model of water use developed for the Aral Sea Basin

    NASA Astrophysics Data System (ADS)

    Riegels, Niels; Kromann, Mikkel; Karup Pedersen, Jesper; Lindgaard-Jørgensen, Palle; Sokolov, Vadim; Sorokin, Anatoly

    2013-04-01

    The water resources of the Aral Sea basin are under increasing pressure, particularly from the conflict over whether hydropower or irrigation water use should take priority. The purpose of the BEAM model is to explore the impact of changes to water allocation and investments in water management infrastructure on the overall welfare of the Aral Sea basin. The BEAM model estimates welfare changes associated with changes to how water is allocated between the five countries in the basin (Kazakhstan, Kyrgyz Republic, Tajikistan, Turkmenistan and Uzbekistan; water use in Afghanistan is assumed to be fixed). Water is allocated according to economic optimization criteria; in other words, the BEAM model allocates water across time and space so that the economic welfare associated with water use is maximized. The model is programmed in GAMS. The model addresses the Aral Sea Basin as a whole - that is, the rivers Syr Darya, Amu Darya, Kashkadarya, and Zarafshan, as well as the Aral Sea. The model representation includes water resources, including 14 river sections, 6 terminal lakes, 28 reservoirs and 19 catchment runoff nodes, as well as land resources (i.e., irrigated croplands). The model covers 5 sectors: agriculture (crops: wheat, cotton, alfalfa, rice, fruit, vegetables and others), hydropower, nature, households and industry. The focus of the model is on welfare impacts associated with changes to water use in the agriculture and hydropower sectors. The model aims at addressing the following issues of relevance for economic management of water resources: • Physical efficiency (estimating how investments in irrigation efficiency affect economic welfare). • Economic efficiency (estimating how changes in how water is allocated affect welfare). • Equity (who will gain from changes in allocation of water from one sector to another and who will lose?). Stakeholders in the region have been involved in the development of the model, and about 10 national experts, including

  7. Tectonic evolution of the north depression of the south Yellow Sea basin since late Cretaceous

    NASA Astrophysics Data System (ADS)

    Li, Nan; Li, Weiran; Long, Haiyan

    2016-12-01

    On the basis of subsidence history analysis and balanced cross-section analysis, the vertical uplift/subsidence history and horizontal extension/compression history of the north depression of the south Yellow Sea basin are quantitatively studied. The results show that the tectonic evolution of the north depression of the south Yellow Sea basin since late Cretaceous can be divided into a rifting phase (late Cretaceous to Paleogene) and a post-rifting phase (Neogene to Quaternary). The rifting phase can be further subdivided into an initial rifting stage (late Cretaceous), an intensive rifting stage (Paleocene), a rifting termination stage (Eocene), and an inversion-uplifting stage (Oligocene). Together, this division shows the characteristics of an episodic-evolved intracontinental rift-depression basin. The deformation of the north depression of the south Yellow Sea basin since late Cretaceous was mainly fault-related. The horizontal extension and tectonic subsidence were controlled by the activity of faults. The differential evolution of faults also caused variations in local uplift/subsidence movements and the regional heterogeneity in extension. The late Cretaceous initial rifting of the north depression of the south Yellow Sea basin is related to the Pacific-Eurasia convergence. From the Paleocene intensive rifting stage to present, the Pacific-Eurasia convergence and India-Eurasia convergence have played important roles in the evolution of this region.

  8. The Rossby whistle: A resonant basin mode in the Caribbean Sea.

    NASA Astrophysics Data System (ADS)

    Hughes, Christopher W.; Williams, Joanne; Hibbert, Angela; Boening, Carmen; Oram, James

    2016-04-01

    We present a a leaky, resonant Rossby basin mode in the Caribbean Sea, excited by instability of the Caribbean Current. The mode is seen at the surface as westward-propagating Rossby waves with period 120 days, but it is most distinctive in ocean bottom pressure where it is seen in both observations and in a wide variety of ocean models. This bottom pressure mode is a product of the leakiness of the basin, which allows for mass exchange with the surrounding ocean. The mode is found to dominate sea level variability on parts of the South American coast.

  9. Geology and hydrocarbon potential of the Dead Sea Rift Basins of Israel and Jordan

    USGS Publications Warehouse

    Coleman, James; Ten Brink, Uri

    2016-01-01

    Geochemical analyses indicate that the source of all oils, asphalts, and tars recovered in the Lake Lisan basin is the Ghareb Formation. Geothermal gradients along the Dead Sea fault zone vary from basin to basin. Syn-wrench potential reservoir rocks are highly porous and permeable, whereas pre-wrench strata commonly exhibit lower porosity and permeability. Biogenic gas has been produced from Pleistocene reservoirs. Potential sealing intervals may be present in Neogene evaporites and tight lacustrine limestones and shales. Simple structural traps are not evident; however, subsalt traps may exist. Unconventional source rock reservoir potential has not been tested.

  10. Deep crustal structure of the Adare and Northern Basins, Ross Sea, Antarctica, from sonobuoy data

    NASA Astrophysics Data System (ADS)

    Selvans, M. M.; Stock, J. M.; Clayton, R. W.; Cande, S.; Granot, R.

    2014-11-01

    Extension associated with ultraslow seafloor spreading within the Adare Basin, in oceanic crust just north of the continental shelf in the Ross Sea, Antarctica, extended south into the Northern Basin. Magnetic and gravity anomaly data suggest continuity of crustal structure across the continental shelf break that separates the Adare and Northern Basins. We use sonobuoy refraction data and multi-channel seismic (MCS) reflection data collected during research cruise NBP0701, including 71 new sonobuoy records, to provide constraints on crustal structure in the Adare and Northern Basins. Adjacent 1D sonobuoy profiles along several MCS lines reveal deep crustal structure in the vicinity of the continental shelf break, and agree with additional sonobuoy data that document fast crustal velocities (6000-8000 m/s) at shallow depths (1-6 km below sea level) from the Adare Basin to the continental shelf, a structure consistent with that of other ultraslow-spread crust. Our determination of crustal structure in the Northern Basin only extends through sedimentary rock to the basement rock, and so cannot help to distinguish between different hypotheses for formation of the basin.

  11. Analysis of Marine Gravity Anomalies in the Ulleung Basin (East Sea/Sea of Japan) and Its Implications for the Architecture of Rift-Dominated Backarc Basin

    NASA Astrophysics Data System (ADS)

    Lee, Sang-Mook; Kim, Yoon-Mi

    2016-04-01

    Marginal basins locate between the continent and arc islands often exhibit diverse style of opening, from regions that appear to have formed by well-defined and localized spreading center (manifested by the presence of distinct seafloor magnetic anomaly patterns) to those with less obvious zones of extension and a broad magmatic emplacement most likely in the lower crust. Such difference in the style of back-arc basin formation may lead to marked difference in crustal structure in terms of its overall thickness and spatial variations. The Ulleung Basin, one of three major basins in the East Sea/Sea of Japan, is considered to represent a continental rifting end-member of back-arc opening. Although a great deal of work has been conducted on the sedimentary sections in the last several decades, the deep crustal sections have not been systematically investigated for long time, and thus the structure and characteristics of the crust remain poorly understood. This study examines the marine gravity anomalies of the Ulleung Basin in order to understand the crustal structure using crucial sediment-thickness information. Our analysis shows that the Moho depth in general varies from 16 km at the basin center to 22 km at the margins. However, within the basin center, the inferred thickness of the crust is more or less the same (10-12 km), thus by varying only about 10-20% of the total thickness, contrary to the previous impression. The almost-uniformly-thick crust that is thicker than a normal oceanic crust (~ 7 km) is consistent with previous observations using ocean bottom seismometers and recent deep seismic results from the nearby Yamato Basin. Another important finding is that small residual mantle gravity anomaly highs exist in the northern part of the basin. These highs are aligned in the NNE-SSW direction which correspond to the orientation of the major tectonic structures on the Korean Peninsula, raising the possibility that, though by a small degree, they are a

  12. The southwestern Nansen Basin: Crustal stretching and sea floor spreading

    NASA Astrophysics Data System (ADS)

    Berglar, Kai; Ehrhardt, Axel; Damm, Volkmar; Heyde, Ingo; Schreckenberger, Bernd; Barckhausen, Udo

    2014-05-01

    New geophysical data were collected in August/September 2013 north of Svalbard in the zone from the North Barents shelf towards the oceanic Nansen Basin. We acquired 1056 km of multi-channel seismic data, 2658 km of magnetic data and more than 5000 km of gravity, bathymetric and sediment echosounder data. In the east of the working area, the transition from the Yermak Plateau to the Nansen Basin is characterized by block faulting and well developed syn-rift basins. A large crustal block located about 80 km east of the Yermak Plateau and 120 km north of the slope of the Barents shelf indicates extensive rifting and east-west directed crustal stretching and the absence of oceanic crust in that area. A different picture is found north of Kvitoya Island, in the western part of the working area. There, the slope of the Barents shelf is very steep and a distinct continent-ocean-boundary seems to be located directly at the foot of the slope where we interpret oceanic crust characterized by irregular topography based on the multi-channel seismic data. This will be tested by an analysis of the gravity and magnetic data which is currently work in progress. The combination of east-west-directed continental stretching east of the Yermak Plateau and adjacent oceanic crust to the west points to an opening of the southwesternmost part of the Nansen Basin prior to the spreading of the Gakkel Ridge, possibly related to the opening of the Amerasian Basin.

  13. Sediment Bacterial Communities Reflect the History of a Sea Basin

    PubMed Central

    Lyra, Christina; Sinkko, Hanna; Rantanen, Matias; Paulin, Lars; Kotilainen, Aarno

    2013-01-01

    How entire microbial communities are structured across stratified sediments from the historical standpoint is unknown. The Baltic Sea is an ideal research object for historical reconstruction, since it has experienced many fresh- and brackish water periods and is depleted of dissolved oxygen, which increases the sediment's preservation potential. We investigated the bacterial communities, chemical elements (e.g. Cr, Pb Na, P, Sr and U) and sediment composition in a stratified sediment core dated by radiocarbon and spanning 8000 years of Baltic Sea history, using up-to-date multivariate statistics. The communities were analysed by 16S rRNA gene terminal restriction fragment length polymorphism. The communities of the deep Early Litorina and surface Late Litorina Sea laminae were separated from the communities of the middle Litorina Sea laminae, which were associated with elevated concentrations of U and Sr trace elements, palaeo-oxygen and palaeosalinity proxies. Thus, the Litorina Sea laminae were characterized by past oxygen deficiency and salinity increase. The communities of the laminae, bioturbated and homogeneous sediments were differentiated, based on the same historical sea phases, with correct classifications of 90%. Palaeosalinity was one of the major parameters that separated the bacterial communities of the stratified sediments. A discontinuous spatial structure with a surprising increase in community heterogeneity was detected in Litorina Sea sediments from 388 to 422 cm deep, which suggests that a salinity maximum occurred in the central Gulf of Finland app. 6200–6600 years ago. The community heterogeneity decreased from the surface down to 306 cm, which reflected downcore mineralization. The plateau of the decrease was in the app. 2000-year-old sediment layers. Bacterial community data may be used as an additional tool in ocean-drilling projects, in which it is important to detect mineralization plateaus both to determine historically comparable

  14. Plio-Quaternary seismic stratigraphy of Ross Sea eastern basin (Antarctica): Implications to glacial history and basin evolution

    SciTech Connect

    Alonso, M.B.; Diaz, J.I. ); Anderson, J.S.; Bartek, L. )

    1991-03-01

    From air-gun and water-gun high-resolution single-channel seismic records, seven seismic units are defined, overlying the Ross Sea Unconformity, in the Plio-Quaternary sequences of the Ross Sea Eastern basin. These units are up to 600 m in thickness and generally thin onshore, disappearing near the western limit of the basin. The units are separated by smooth erosional surfaces characterized by continuous, high-amplitude reflectors. By correlation to DSDP Site 272, seismic units I and II are Pliocene in age, and the overlying units (III or VII) are Quaternary in age. Units I, III, and VII are basinal in extension and the others are confined to the central part of the basin. Thickness of the units ranges from 50 to 120 m, and they are mainly characterized by lenticular and wedge geometrics. Three acoustic facies are discerned: stratified, semitransparent, and chaotic. Wide (7 km) lenticular deposits, containing chaotic facies, are incised by U-shaped channels in seismic units, II, III (both up to 0.5 km wide), and VI (2 km wide), The spatial distribution of these channels indicates a paleodrainage system in which ice streams followed flow paths similar to those of the present. The major geological events that occurred on the continental shelf during Plio-Quaternary time were: (1) the first channel incisions are identified near the boundary of the late Pliocene-Quaternary; (2) the advance and retreat of the ice sheet resulted in widespread erosion processes alternating with deposition of glacial and glaciomarine sediments; (3) the largest depocenter has been always situated in the shelf break environment, near the western limit of the basin; and (4) the only important progradation of the shelf occurred during the late Pliocene, and since then the shelf has been aggradational.

  15. Time-dependence of sea-ice concentration and multiyear ice fraction in the Arctic Basin

    USGS Publications Warehouse

    Gloersen, P.; Zwally, H.J.; Chang, A.T.C.; Hall, D.K.; Campbell, W.J.; Ramseier, R.O.

    1978-01-01

    The time variation of the sea-ice concentration and multiyear ice fraction within the pack ice in the Arctic Basin is examined, using microwave images of sea ice recently acquired by the Nimbus-5 spacecraft and the NASA CV-990 airborne laboratory. The images used for these studies were constructed from data acquired from the Electrically Scanned Microwave Radiometer (ESMR) which records radiation from earth and its atmosphere at a wavelength of 1.55 cm. Data are analyzed for four seasons during 1973-1975 to illustrate some basic differences in the properties of the sea ice during those times. Spacecraft data are compared with corresponding NASA CV-990 airborne laboratory data obtained over wide areas in the Arctic Basin during the Main Arctic Ice Dynamics Joint Experiment (1975) to illustrate the applicability of passive-microwave remote sensing for monitoring the time dependence of sea-ice concentration (divergence). These observations indicate significant variations in the sea-ice concentration in the spring, late fall and early winter. In addition, deep in the interior of the Arctic polar sea-ice pack, heretofore unobserved large areas, several hundred kilometers in extent, of sea-ice concentrations as low as 50% are indicated. ?? 1978 D. Reidel Publishing Company.

  16. Contributions to the Oceanography of the Western Alboran Sea.

    DTIC Science & Technology

    1985-04-01

    Biological and nutrient concentrations also had a complicated and variable I. structure. Phosphate concentrations were...d’Histoire Naturelle , Paris. Haltiner, G.J. and F.L. Martin, 1957. Dynamical and Physical Meteorology. McGraw-Hill Book Co., 470pp. Hurlburt, H.E. and J.D

  17. Midwater Bioluminescence Assessment in the West Alboran Gyre (Mediterranean Sea)

    DTIC Science & Technology

    1991-09-01

    Mediterranean (see Mills and Goy, m 1988, for review), moving up into the upper 100 m during the night. Our night dive observations tented to support that...413 484.7 91.4I 57)491 Nepheloctena white- tent -ade 2939-CGS Creno 511 491.2 86.3 P42)491 Ocyropsis macalata BWI-4 Creno 356 492.2 86.3 F39)491...umbrellar margin. Solmissus (the single most abundant medusa) is also transparent and brightly luminescent from the lateral umbrellar margin,the velum

  18. Tectonics of Chukchi Sea Shelf sedimentary basins and its influence on petroleum systems

    NASA Astrophysics Data System (ADS)

    Agasheva, Mariia; Antonina, Stoupakova; Anna, Suslova; Yury, Karpov

    2016-04-01

    The Chukchi Sea Shelf placed in the East Arctic offshore of Russia between East Siberian Sea Shelf and North Slope Alaska. The Chukchi margin is considered as high petroleum potential play. The major problem is absence of core material from drilling wells in Russian part of Chukchi Shelf, hence strong complex geological and geophysical analyses such as seismic stratigraphy interpretation should be provided. In addition, similarity to North Slope and Beaufort Basins (North Chukchi) and Hope Basin (South Chukchi) allow to infer the resembling sedimentary succession and petroleum systems. The Chukchi Sea Shelf include North and South Chukchi Basins, which are separated by Wrangel-Herald Arch and characterized by different opening time. The North Chukchi basin is formed as a general part of Canada Basin opened in Early Cretaceous. The South Chukchi Basin is characterized by a transtensional origin of the basin, this deformation related to motion on the Kobuk Fault [1]. Because seismic reflections follow chronostratigraphic correlations, it is possible to achieve stratigraphic interpretation. The main seismic horizons were indicated as: PU, JU, LCU, BU, mBU marking each regional unconformities. Reconstruction of main tectonic events of basin is important for building correct geological model. Since there are no drilling wells in the North and South Chukchi basins, source rocks could not be proven. Referring to the North Chukchi basin, source rocks equivalents of Lower Cretaceous Pebble Shale Formation, Lower Jurassic Kingdak shales and Upper Triassic Shublik Formation (North Slope) is possible exhibited [2]. In the South Chukchi, it is possible that Cretaceous source rocks could be mature for hydrocarbon generation. Erosions and uplifts that could effect on hydrocarbon preservation was substantially in Lower Jurassic and Early Cretaceous periods. Most of the structures may be connected with fault and stratigraphy traps. The structure formed at Wrangel-Herald Arch to

  19. Understanding sedimentation in the Song Hong-Yinggehai Basin, South China Sea

    NASA Astrophysics Data System (ADS)

    Yan, Yi; Carter, Andrew; Palk, Carl; Brichau, StéPhanie; Hu, Xiaoqiong

    2011-06-01

    The Cenozoic Song Hong-Yinggehai Basin in the South China Sea contains a large volume of sediment that has been used in previous studies, together with regional geomorphology, to argue for the existence of a large palaeodrainage system that connected eastern Tibet with the South China Sea. To test this and to understand the significance of sediment volumes deposited in the Song Hong-Yinggehai Basin, this study compared erosion histories of source regions with sediment volumes deposited during the two main stages in basin evolution spanning active rifting and subsidence (30-15.5 Ma) and postrift sedimentation (15.5 Ma to present). The study of basin provenance by detrital zircon U-Pb dating revealed Hainan was an important and continuous source of sediment, and a bedrock thermochronological study quantified its overall contribution to basin sedimentation. Comparison between the accumulated mass of basin sediment and volumes of eroded bedrock, calculated from apatite thermochronometry across the modern Red River drainage in northern Vietnam as well as Hainan Island, accounted for the bulk of sediment deposited since 30 Ma. Consequently, if an expanded paleodrainage ever existed it must have predated the Oligocene.

  20. Subcrustal structure of the black sea basin from seismological data

    NASA Astrophysics Data System (ADS)

    Yanovskaya, T. B.; Gobarenko, V. S.; Yegorova, T. P.

    2016-01-01

    The P-wave travel time data from the earthquakes offshore and onshore around the Black Sea are used for the tomographic reconstruction of the three-dimensional (3D) velocity distribution in the lithosphere of the region. The preliminary refinement of the foci parameters (the coordinates and origin time) has reduced the random errors in the travel-time data. The earthquake data were supplemented by the previous deep seismic sounding (DSS) data on the profiles in Crimea and offshore off the Black Sea. The dataset included more than 4000 travel times overall. In order to eliminate the crustal effect, the travel times were reduced to a surface at a depth of 35 km corresponding to the mean Moho depth in the region. The improved crustal model was used for removing the contribution of the crust from the initial data. The new tomography method, which was recently developed by one of the authors and which relies on the assumption of smoothness of the lateral velocity variations, was applied for reconstructing the velocity structure of the upper mantle beneath the Black Sea up to a depth of 95 km. The lateral velocity variation maps at different depths and the vertical velocity distributions along the meridional and sublatitudinal cross sections across the Black Sea were constructed. High velocities were revealed in the subcrustal lithosphere, and the structural difference below two subbasins—the West Black Sea (WBS) and the East Black Sea (EBS) ones—was established. It shows that the high-velocity body below the WBS is located deeper than below the EBS and is distinguished by higher velocities. Based on these results, it is concluded that the lithosphere beneath the Black Sea has a continental origin.

  1. Tectonics and petroleum potential of sedimentary basins in the Bering, Okhotsk, Japan seas, and island arcs

    SciTech Connect

    Levin, L.E. )

    1993-09-01

    In this vast region located in the northwestern part of the Pacific rim, basins of two main genetic types possess petroleum potential. These two types are represented by basins of the recent active margin and basins of the transitional zone between analogs of the passive margin and the recent active margin. For basins of the active margin, the mean density of potential resources is estimated at 5000 MT/km[sup 2] or more. The total area of these basins is 324,000 km[sup 2] among which 120,000 km[sup 2] are in the Russian sector. Ultimate resources of hydrocarbons are estimated at 1.62 billing MT of oil equivalent. Basins of the zone, transitional from analogs of the passive margin to the recent active margin, are characterized by a number of factors favorable for petroleum occurrence. One of the important factors is the presence of rift trough and foredeeps that are potential sites for zones of oil and gas accumulation. The age of the rifts varies from the late Cretaceous through the Oligocene-Miocene in the Olyutorsky and Litke basins, to the Neogene in the Okhotsk Sea and Tatar-Japan basins. Only a small area of the rifts has been proven to contain zones of oil and gas accumulation. Based on the structural characteristics, the rifts are subdivided into oil-gas bearing, potentially oil-gas bearing, and nonprospective for hydrocarbon exploration. Potential hydrocarbon resources of basins of this type are estimated to be not less than 15.12 billion MT of oil equivalent including 9.2 billion MT in the Russian sector. New large zones of oil and gas accumulation are expected to be found both on the shallow shelf and in some deep-water basins such as in the Aleutian and Kuril basins.

  2. Localized accumulation and a shelf-basin gradient of particles in the Chukchi Sea and Canada Basin, western Arctic

    NASA Astrophysics Data System (ADS)

    Yamada, Yosuke; Fukuda, Hideki; Uchimiya, Mario; Motegi, Chiaki; Nishino, Shigeto; Kikuchi, Takashi; Nagata, Toshi

    2015-07-01

    Transparent exopolymer particles (TEP), particulate organic carbon (POC), and particles (size range: 5.2-119 μm) as determined by laser in situ scattering and transmissometry (LISST) were measured in the water column from the Chukchi Sea to the Canada Basin in the western Arctic Ocean, during the late summer of 2012. In general, the percentages of TEP-carbon to POC were high (the mean values for the shelf and slope-basin regions were 135.4 ± 58.0% (± standard deviation, n = 36) and 187.6 ± 73.3% (n = 58), respectively), relative to the corresponding values reported for other oceanic regions, suggesting that TEP play an important role in regulating particle dynamics. A hotspot (extremely high concentration) of particles, accompanied by high prokaryote abundance and production, was observed near the seafloor (depth 50 m) of the shelf region. Localized accumulation of particles was also found in the thin layer near the pycnocline (depth 10-30 m) and on the slope. Over a broader spatial scale, particle concentration gradients were identified from the shelf to the basin in the upper water column (<50 m). The particle-size distribution analysis indicated that relatively small particles were dominant in the shelf region compared to the slope-basin region. These results suggest that particles containing large amounts of TEP are produced in the shelf region and are potentially delivered to the slope-basin region along the pycnocline, which might support productivity and material cycles in the nutrient-depleted basin region of the western Arctic Ocean.

  3. Middle Cenozoic depositional, tectonic, and sea level history of southern San Joaquin basin, California

    SciTech Connect

    Decelles, P.G.

    1988-11-01

    As a prolific producer of hydrocarbons, the San Joaquin basin in south-central California has been the subject of geological research since the late nineteenth century. Much of this research has focused on the subsurface Eocene to lower Miocene succession because of its attractive reservoir potential. Although seismic and well-log data are available in profuse quantities, the complex sedimentary architecture of the basin fill, the application of local and inconsistent stratigraphic nomenclature, and the inherent limitations of subsurface data have led to much confusion concerning the middle Cenozoic history of the basin. This paper presents a sedimentological analysis of the depositional systems in the Eocene to lower Miocene strata of the San Emigdio and Tehachapi Mountains. The various depositional systems are considered within the contexts of encompassing depositional sequences to reconstruct the middle Cenozoic depositional, tectonic, and sea level history of the southern San Joaquin basin. 14 figures, 1 table.

  4. Combined Effects of Nutrient Load Reduction and Climate Scenarios for the Baltic Sea Basin

    NASA Astrophysics Data System (ADS)

    Donnelly, Chantal; Strömqvist, Johan; Dahné, Joel; Arheimer, Berit

    2010-05-01

    A Baltic Sea Action Plan was approved in 2007 by the countries surrounding the Baltic Sea to improve the ecological status of this sea. An important part of this plan is reduction of nutrient inflows from the Baltic Sea basin into the sea. Required nutrient reductions have been apportioned to the countries within the basin and these countries are now planning the remedial measures required to meet the plan's requirements. An important factor that remains to be considered, however, is how well the planned nutrient reductions improve nutrient inflows into the Baltic Sea in a changed future climate. A high resolution, process based hydrological and nutrient flux model was set up for the entire Baltic Sea catchment area using the HYPE (Hydrological Predictions for the Environment) model. The HYPE model introduces the ability to model detailed hydrological processes at high resolution simultaneously and homogenously across many river basins. When using a modelling tool to assess water resources and their quality for a basin entailing several political entities, it is an advantage that the methods and data used are homogenous across such political boundaries. Readily available, regional and global databases were used to set up the model inputs including topography, precipitation, temperature, land use, soil-type, and nutrients from atmospheric, agricultural, industrial and urban wastewaster sources, over the entire model domain. Daily river runoff data from the Baltex and GRDC databases was used to calibrate and validate the parameters describing runoff processes, while monthly and seasonal data from the European Environment Agency's WISE database were used to calibrate and validate the water quality parameters in the model. The model application is able to reproduce measured daily flow variations and magnitude in both large and small waterways across the model domain, and measured seasonal variation and overall magnitude of nutrient fluxes to the Baltic Sea. Total

  5. Study of southern CHAONAN sag lower continental slope basin deposition character in Northern South China Sea

    NASA Astrophysics Data System (ADS)

    Tang, Y.

    2009-12-01

    Northern South China Sea Margin locates in Eurasian plate,Indian-Australia plate,Pacific Plates.The South China Sea had underwent a complicated tectonic evolution in Cenozoic.During rifting,the continental shelf and slope forms a series of Cenozoic sedimentary basins,including Qiongdongnan basin,Pearl River Mouth basin,Taixinan basin.These basins fill in thick Cenozoic fluviolacustrine facies,transitional facies,marine facies,abyssal facies sediment,recording the evolution history of South China Sea Margin rifting and ocean basin extending.The studies of tectonics and deposition of depression in the Southern Chaonan Sag of lower continental slope in the Norther South China Sea were dealt with,based on the sequence stratigraphy and depositional facies interpretation of seismic profiles acquired by cruises of“China and Germany Joint Study on Marine Geosciences in the South China Sea”and“The formation,evolution and key issues of important resources in China marginal sea",and combining with ODP 1148 cole and LW33-1-1 well.The free-air gravity anomaly of the break up of the continental and ocean appears comparatively low negative anomaly traps which extended in EW,it is the reflection of passive margin gravitational effect.Bouguer gravity anomaly is comparatively low which is gradient zone extended NE-SW.Magnetic anomaly lies in Magnetic Quiet Zone at the Northern Continental Margin of the South China Sea.The Cenozoic sediments of lower continental slope in Southern Chaonan Sag can be divided into five stratum interface:SB5.5,SB10.5,SB16.5,SB23.8 and Hg,their ages are of Pliocene-Quaternary,late Miocene,middle Miocene,early Miocene,paleogene.The tectonic evolution of low continental slope depressions can be divided into rifting,rifting-depression transitional and depression stages,while their depositional environments change from river to shallow marine and abyssa1,which results in different topography in different stages.The topographic evolvement in the study

  6. The petroleum basins of the sea of Okhotsk

    SciTech Connect

    Khvedchuk, I. )

    1993-09-01

    The Okhotsk area includes the major oil and gas basins of north Sakhalin and west Kamchatka, where more than 70 fields have been discovered. The basins consist of Tertiary cover (marine, coastal and continental terrigenous, and siliceous volcanogenic and volcanoclastic rocks) and pre-Cenozoic basement composed of geosynclinal rock associations. Sediment thickness in the basins attains 10-12 km. Rifting of the basement has resulted in the development of grabens controlled by northwest- and northeast-trending faults. Crustal thickness is 27-31 km. All the petroleum basins are related to rifts, which were associated with volcanic and magmatic activity and abnormally high temperature and pressures. Analysis of the data show that the main factors affecting deposition of the source rocks, their spatial distribution, and their effectiveness in generating hydrocarbons are; the geological age, regional tectonics, paleogeography, dominant kerogen type, and temperature. There are various types of oil and gas source rocks: Paleocene to lower Eocene claystones contain gas-prone kerogen type III (west Kamchatka); upper Eocene and Oligocene marine clays and siliceous clays contain oil-prone kerogen type II (west Kamchatka); upper Oligocene to lower Miocene siliceous shales (north Sakhalin and west Kamchatka) contain kerogen type II; lower and middle Miocene clays are gas prone (north Sakhalin and west Kamchatka); and middle Miocene marine clays contain oil-prone kerogen type II (north Sakhalin). The quantity of organic matter in the source rocks ranges from 0.6 to 4.2%, and the geothermal gradient ranges from 24 to 44[degrees]C per km. The main reservoirs are upper Oligocene-lower Miocene siliceous shales, Miocene-lower Pliocene sandstones, and upper Miocene deltaic sandstones. Oil and gas accumulations occur in anticlines and stratigraphic traps.

  7. Salt tectonics in the northeastern Nordkapp Basin, southwestern Barents Sea

    SciTech Connect

    Koyi, H.; Talbot, C.J.; Torudbakken, B.O.

    1996-12-31

    Salt structures in the northeastern Nordkapp subbasin are interpreted on reflection seismic profiles. Thickness variations indicate localized accumulation of the mother salt in Late Carboniferous-Early Permian time. Rapid sedimentation in the Early Triassic accompanied rise of salt into asymmetric salt pillows during regional extension. These pillows domed the prekinematic Permian sediments and became diapiric during the late Early-Middle Triassic, perhaps as a result of thin-skinned normal faulting decoupled by the salt from old basements faults reactivated by thick-skinned regional (northwest-southeast) extension. Variations in size, maturity, and evolution history of individual salt structures can be attributed to local differences in thickness of the initial salt layer and its burial history. Salt structures form three rows concentric to the basin margins and cover {approximately}20% of the basin area. Some salt stocks appear to overlie basement faults. Asymmetric primary, secondary, and in places tertiary, peripheral sinks indicate that salt was withdrawn mainly from the basin side of most diapirs throughout Triassic downbuilding.

  8. Chapter 19: Geology and petroleum potential of the east Barents Sea Basins and Admiralty Arch

    USGS Publications Warehouse

    Klett, T.R.; Pitman, J.K.

    2011-01-01

    The US Geological Survey (USGS) recently assessed the potential for undiscovered oil and gas resources of the East Barents Basins and Novaya Zemlya Basins and Admiralty Arch Provinces as part of the USGS Circum-Arctic Resource Appraisal. These two provinces are located NE of Scandinavia and the northwestern Russian Federation, on the Barents Sea Shelf between Novaya Zemlya to the east and the Barents Platform to the west. Three assessment units (AUs) were defined in the East Barents Basins for this study - Kolguyev Terrace Assessment Unit (AU), South Barents Basin and Ludlov Saddle AU, and North Barents Basin AU. A fourth, defined as Novaya Zemlya Basins and Admiralty Arch AU, is coincident with the Novaya Zemlya basins and Admiralty Arch Province. These AUs, all lying north of the Arctic Circle, were assessed for undiscovered, technically recoverable resources resulting in total estimated mean volumes of approximately 7.4 billion barrels of crude oil, 318 trillion cubic feet of natural gas and 1.4 billion barrels of natural gas liquids. ?? 2011 The Geological Society of London.

  9. Gravity field over the Sea of Galilee: Evidence for a composite basin along a transform fault

    USGS Publications Warehouse

    Ben-Avraham, Z.; ten Brink, U.; Bell, R.; Reznikov, M.

    1996-01-01

    The Sea of Galilee (Lake Kinneret) is located at the northern portion of the Kinneret-Bet Shean basin, in the northern Dead Sea transform. Three hundred kilometers of continuous marine gravity data were collected in the lake and integrated with land gravity data to a distance of more than 20 km around the lake. Analyses of the gravity data resulted in a free-air anomaly map, a variable density Bouguer anomaly map, and a horizontal first derivative map of the Bouguer anomaly. These maps, together with gravity models of profiles across the lake and the area south of it, were used to infer the geometry of the basins in this region and the main faults of the transform system. The Sea of Galilee can be divided into two units. The southern half is a pull-apart that extends to the Kinarot Valley, south of the lake, whereas the northern half was formed by rotational opening and transverse normal faults. The deepest part of the basinal area is located well south of the deepest bathymetric depression. This implies that the northeastern part of the lake, where the bathymetry is the deepest, is a young feature that is actively subsiding now. The pull-apart basin is almost symmetrical in the southern part of the lake and in the Kinarot Valley south of the lake. This suggests that the basin here is bounded by strike-slip faults on both sides. The eastern boundary fault extends to the northern part of the lake, while the western fault does not cross the northern part. The main factor controlling the structural complexity of this area is the interaction of the Dead Sea transform with a subperpendicular fault system and rotated blocks.

  10. Sea-floor drainage features of Cascadia Basin and the adjacent continental slope, northeast Pacific Ocean

    USGS Publications Warehouse

    Hampton, M.A.; Karl, Herman A.; Kenyon, Neil H.

    1989-01-01

    Sea-floor drainage features of Cascadia Basin and the adjacent continental slope include canyons, primary fan valleys, deep-sea valleys, and remnant valley segments. Long-range sidescan sonographs and associated seismic-reflection profiles indicate that the canyons may originate along a mid-slope escarpment and grow upslope by mass wasting and downslope by valley erosion or aggradation. Most canyons are partly filled with sediment, and Quillayute Canyon is almost completely filled. Under normal growth conditions, the larger canyons connect with primary fan valleys or deep-sea valleys in Cascadia Basin, but development of accretionary ridges blocks or re-routes most canyons, forcing abandonment of the associated valleys in the basin. Astoria Fan has a primary fan valley that connects with Astoria Canyon at the fan apex. The fan valley is bordered by parallel levees on the upper fan but becomes obscure on the lower fan, where a few valley segments appear on the sonographs. Apparently, Nitinat Fan does not presently have a primary fan valley; none of the numerous valleys on the fan connect with a canyon. The Willapa-Cascadia-Vancouver-Juan de Fuca deep-sea valley system bypasses the submarine fans and includes deeply incised valleys to broad shallow swales, as well as within-valley terraces and hanging-valley confluences. ?? 1989.

  11. The Northern end of the Dead Sea Basin: Geometry from reflection seismic evidence

    USGS Publications Warehouse

    Al-Zoubi, A. S.; Heinrichs, T.; Qabbani, I.; ten Brink, U.S.

    2007-01-01

    Recently released reflection seismic lines from the Eastern side of the Jordan River north of the Dead Sea were interpreted by using borehole data and incorporated with the previously published seismic lines of the eastern side of the Jordan River. For the first time, the lines from the eastern side of the Jordan River were combined with the published reflection seismic lines from the western side of the Jordan River. In the complete cross sections, the inner deep basin is strongly asymmetric toward the Jericho Fault supporting the interpretation of this segment of the fault as the long-lived and presently active part of the Dead Sea Transform. There is no indication for a shift of the depocenter toward a hypothetical eastern major fault with time, as recently suggested. Rather, the north-eastern margin of the deep basin takes the form of a large flexure, modestly faulted. In the N-S-section along its depocenter, the floor of the basin at its northern end appears to deepen continuously by roughly 0.5??km over 10??km distance, without evidence of a transverse fault. The asymmetric and gently-dipping shape of the basin can be explained by models in which the basin is located outside the area of overlap between en-echelon strike-slip faults. ?? 2007 Elsevier B.V. All rights reserved.

  12. A 4D Framework for Ocean Basin Paleodepths and Eustatic Sea Level Change

    NASA Astrophysics Data System (ADS)

    Muller, R.; Sdrolias, M.; Gaina, C.

    2006-12-01

    A digital framework for paleobathymetry of the ocean basins requires the complete reconstruction of ocean floor through time, including the main ocean basins, back-arc basins, and now subducted ocean crust. We reconstruct paleo-oceans by creating "synthetic plates", the locations and geometry of which is established on the basis of preserved ocean crust (magnetic lineations and fracture zones), geological data, and the rules of plate tectonics. We reconstruct the spreading histories of the Pacific, Phoenix, Izanagi, Farallon and Kula plates, the plates involved in the Indian, Atlantic, Caribbean, Arctic, Tethys and Arctic oceanic domains and all plates involved in preserved backarc basins. Based mainly on the GML-standards compliant GPlates software and the Generic Mapping Tools, we have created a set of global oceanic paleo-isochrons and paleoceanic age and depth grids. We show that the late-Cretaceous sea level highstand and the subsequent long-term drop in sea level was primarily caused by the changing age-area distribution of Pacific ocean floor through time. The emplacement of oceanic plateaus has resulted in a 40 m sealevel rise between 125 and 110 Ma, and a further 60 m rise after 110 Ma, whereas the oceanic age and latitude dependence of marine sediments has resulted in a 40m sealevel rise since about 120Ma, offsetting the gradual post-80Ma drop in sealevel due to the ageing and deepening mainly of the Pacific ocean basin, with the net effect being an about 200m drop after 80 Ma. Between 140 Ma and the present, oceanic crustal production dropped by over 40% in the Pacific, but stayed roughly constant in the remaining ocean basins. Our results suggest that the overall magnitude of 1st order sealevel change implied by Haq's sea level curve is correct.

  13. Diachronous fault array growth within continental rift basins: Quantitative analyses from the East Shetland Basin, northern North Sea

    NASA Astrophysics Data System (ADS)

    Claringbould, Johan; Bell, Rebecca; Jackson, Christopher; Gawthorpe, Robert; Odinsen, Tore

    2016-04-01

    The evolution of rift basins has been the subject of many studies, however, these studies have been mainly restricted to investigating the geometry of rift-related fault arrays. The relative timing of development of individual faults that make up the fault array is not yet well constrained. First-order tectono-stratigraphic models for rifts predict that normal faults develop broadly synchronously throughout the basin during a temporally distinct 'syn-rift' episode. However, largely due to the mechanical interaction between adjacent structures, distinctly diachronous activity is known to occur on the scale of individual fault segments and systems. Our limited understanding of how individual segments and systems contribute to array-scale strain largely reflects the limited dimension and resolution of the data available and methods applied. Here we utilize a regional extensive subsurface dataset comprising multiple 3D seismic MegaSurveys (10,000 km2), long (>75km) 2D seismic profiles, and exploration wells, to investigate the evolution of the fault array in the East Shetland Basin, North Viking Graben, northern North Sea. Previous studies propose this basin formed in response to multiphase rifting during two temporally distinct extensional phases in the Permian-Triassic and Middle-to-Late Jurassic, separated by a period of tectonic quiescence and thermal subsidence in the Early Jurassic. We document the timing of growth of individual structures within the rift-related fault array across the East Shetland Basin, constraining the progressive migration of strain from pre-Triassic-to-Late Jurassic. The methods used include (i) qualitative isochron map analysis, (ii) quantitative syn-kinematic deposit thickness difference across fault & expansion index calculations, and (iii) along fault throw-depth & backstripped displacement-length analyses. In contrast to established models, we demonstrate that the initiation, growth, and cessation of individual fault segments and

  14. Aspects of exploration, development of Vulcan sub-basin, Timor Sea

    SciTech Connect

    Smith, B.L. ); Lawrence, R.B. )

    1989-10-01

    This article presents a geological summary of the Vulcan sub-basin. Three exploratory phases in the Timor Sea are detailed and the economics of exploration in this area is discussed. The Timor Sea is emerging as a major Australian oil-producing area. From the Jabiru field alone Timor Sea oil production contributes 9% of Australia's oil production. The Timor Sea will soon rank second in terms of daily production. Early phases of exploration in the area focused on the detection and drilling of large structures. Success rates were low. Since the Jabiru discovery in 1983, better exploration methods have resulted in the delineation of many prospects which could contain significant oil reserves. New play concepts being developed will result in additional prospects.

  15. The Paleoclimate of the Dead Sea Basin from the Last Glacial Maximum to the Holocene

    DTIC Science & Technology

    2001-11-01

    The purpose of this study was to determine the late glacial paleoclimate of the Southern Levant. A study of delta 13C and delta 18O in carbonates...derived from carbon and oxygen isotopes provide insight into the paleoclimate of the Southern Levant. The period from 20-14.6 kya was dry and cool, with...organic matter into the basin. The results of this study agree with other studies based on paleolake levels, pollen levels and paleoclimate studies from the Dead Sea Basin.

  16. Geologic implications of gas hydrates in the offshore of India: Krishna-Godavari Basin, Mahanadi Basin, Andaman Sea, Kerala-Konkan Basin

    USGS Publications Warehouse

    Kumar, Pushpendra; Collett, Timothy S.; Boswell, Ray; Cochran, James R.; Lall, Malcolm; Mazumdar, Aninda; Ramana, Mangipudi Venkata; Ramprasad, Tammisetti; Riedel, Michael; Sain, Kalachand; Sathe, Arun Vasant; Vishwanath, Krishna; Yadav, U.S.

    2014-01-01

    NGHP-01 yielded evidence of gas hydrate from downhole log and core data obtained from all the sites in the Krishna–Godavari Basin, the Mahanadi Basin, and in the Andaman Sea. The site drilled in the Kerala–Konkan Basin during NGHP-01 did not yield any evidence of gas hydrate. Most of the downhole log-inferred gas hydrate and core-recovered gas hydrate were characterized as either fracture-filling in clay-dominated sediments or as pore-filling or grain-displacement particles disseminated in both fine- and coarse-grained sediments. Geochemical analyses of gases obtained from sediment cores recovered during NGHP-01 indicated that the gas in most all of the hydrates in the offshore of India is derived from microbial sources; only one site in the Andaman Sea exhibited limited evidence of a thermogenic gas source. The gas hydrate petroleum system concept has been used to effectively characterize the geologic controls on the occurrence of gas hydrates in the offshore of India.

  17. Propagation regimes and populations of internal waves in the Mediterranean Sea basin

    NASA Astrophysics Data System (ADS)

    Kurkina, Oxana; Rouvinskaya, Ekaterina; Talipova, Tatiana; Soomere, Tarmo

    2017-02-01

    The geographical and seasonal distributions of kinematic and nonlinear parameters of long internal waves are derived from the Generalized Digital Environmental Model (GDEM) climatology for the Mediterranean Sea region, including the Black Sea. The considered parameters are phase speed of long internal waves and the coefficients at the dispersion, quadratic and cubic terms of the weakly-nonlinear Korteweg-de Vries-type models (in particular, the Gardner model). These parameters govern the possible polarities and shapes of solitary internal waves, their limiting amplitudes and propagation speeds. The key outcome is an express estimate of the expected parameters of internal waves for different regions of the Mediterranean basin.

  18. Discussion of the Ionian and Levantine Seas, NATO workshop on atmospheric and oceanic circulation in the Mediterranean Basin

    SciTech Connect

    Hopkins, T.S.

    1984-01-01

    The gross features and distinctiveness of its thermohaline circulation are described for the Ionian and Levantine Seas of the eastern Mediterranean. The paper also discusses the significance of the thermohaline coupling with neighboring Mediterranean basins. 22 refs. (ACR)

  19. The Norwegian Danish Basin: A key to understanding the Cenozoic in the eastern North Sea

    NASA Astrophysics Data System (ADS)

    Rasmussen, Thomas L.; Clausen, Ole R.; Andresen, Katrine J.; Goledowski, Bartosz

    2015-04-01

    The Danish part of Norwegian-Danish Basin, which constitutes the eastern part of the North Sea Basin, has been the key area for sequence stratigraphic subdivision and analysis of the Cenozoic succession since the mid 1990's. Widespread 3D seismic data, in the central parts of the North Sea Basin, as well as more scattered 3D seismic data in the Danish part of the Norwegian-Danish Basin, have given a more detailed understanding of the sequences and indicate that climate is tenable for the origin of Cenozoic sequence boundaries. The previous sequence stratigraphic interpretations have been an integrated part of an ongoing debate concerning vertical movements of the Fennoscandian shield versus the impact of climate and erosion. A newly accessed coherent regional 2D and reprocessed 3D seismic data set, in the Norwegian part of the Norwegian-Danish Basin, constitute the database for a new sequence stratigraphic analysis of the entire area. The objective of the new study is to test previous subdivisions and introduce a coherent 3D sequence stratigraphic analysis and depositional model for the entire Norwegian-Danish Basin. This analysis is necessary to get out of the stalemate with the uplift discussion. The study shows that the original subdivision by Michelsen et al. (1995, 1998) stands. However, revision of few a sequence boundaries may have to be adjusted due to new biostratigraphic information published. Furthermore, high-angle clinoforms and geomorphological transport complexes observed in the Danish North Sea Basin can be traced into the Norwegian sector. This together with the recognition of several other high-angle clinoform complexes, and their associated seismic facies distribution maps and thickness-maps, enhances the level of detail and constrains the previous published paleogeographic reconstructions of the Cenozoic. The geometry of the Cenozoic infill, in the Norwegian part of the Norwegian-Danish Basin, is here interpreted to be controlled by relative sea

  20. The Canada Basin compared to the southwest South China Sea: Two marginal ocean basins with hyper-extended continent-ocean transitions

    NASA Astrophysics Data System (ADS)

    Li, Lu; Stephenson, Randell; Clift, Peter D.

    2016-11-01

    Both the Canada Basin (a sub-basin within the Amerasia Basin) and southwest (SW) South China Sea preserve oceanic spreading centres and adjacent passive continental margins characterized by broad COT zones with hyper-extended continental crust. We have investigated strain accommodation in the regions immediately adjacent to the oceanic spreading centres in these two basins using 2-D backstripping subsidence reconstructions, coupled with forward modelling constrained by estimates of upper crustal extensional faulting. Modelling is better constrained in the SW South China Sea but our results for the Canada Basin are analogous. Depth-dependent extension is required to explain the great depth of both basins because only modest upper crustal faulting is observed. A weak lower crust in the presence of high heat flow and, accordingly, a lower crust that extends far more the upper crust are suggested for both basins. Extension in the COT may have continued even after seafloor spreading has ceased. The analogous results for the two basins considered are discussed in terms of (1) constraining the timing and distribution of crustal thinning along the respective continental margins, (2) defining the processes leading to hyper-extension of continental crust in the respective tectonic settings and (3) illuminating the processes that control hyper-extension in these basins and more generally.

  1. On the origin age of the Southwest Basin in the South China Sea

    NASA Astrophysics Data System (ADS)

    Liu, Zhao-Shu; Yan, Pin; Liu, Hai-Ling

    1997-09-01

    This paper propounds that the origin and evolution of the Southwest Basin (SWB) in the South China Sea (SCS) are closely related with those of the SCS, reviews various viewpoints on its origin age with a large gap between the oldest age and the youngest age, offers some suggestions on the SWB’s origin age and gives some proposals to ascertain satisfactorily the origin and evolution, and multi-phasal and multiaxial spreading of the SCS and SWB.

  2. Shelf sheet-sand reservoir of the lower Cretaceous Greensand, North Celtic Sea Basin, offshore Ireland

    SciTech Connect

    Winn, R.D. Jr.

    1994-11-01

    Core and log data show that the marine, early to middle Albian {open_quotes}A{close_quotes} Sand of the Aptian to lower Cenomanian Greensand-Gault interval, North Celtic Sea Basin, offshore Ireland, was deposited as an approximately tabular sand body in shelf water depths. The {open_quotes}A{close_quotes} Sand is the major reservoir interval at Kinsale Head and Ballycotton gas fields. The reservoir sandstone is bioturbated, variably glauconitic, shell rich, and least muddy toward its provenance in a local area of the Irish massif and finer grained southeastward into the basin. Thickness and coarseness of the {open_quotes}A{close_quotes} Sand are related, in part, to distance from a narrow area of the paleoshore. Bathymetric control of sand thickness was superimposed on proximal-distal trends. Specifically, thick intervals are inferred to have been deposited in shelf lows, and thin zones were deposited over bathymetric highs. The {open_quotes}A{close_quotes} Sand was not deposited as a ridge sand, and positive relief on the depositional sand body appears to have been minor. Deposition of the Greensand occurred during thermal subsidence of the North Celtic Sea Basin following Early Cretaceous rifting. Overall late Early Cretaceous to Late Cretaceous transgression was interrupted by progradation of the {open_quotes}A{close_quotes} Sand, probably caused by a relative drop in sea level (forced regression). The {open_quotes}A{close_quotes} Sand sheet consists of several units within the central depositional basin. Three slightly coarsening-upward units up to 15 m thick probably are the consequence of high-frequency fluctuations in sea level during progradation. The top of the {open_quotes}A{close_quotes} Sand consists of a several-meter-thick, very glauconitic, muddy sandstone to sandy mudstone. The upper unit accumulated in deepening water following the maximum lowstand.

  3. Cheirimedon foscae sp. nov. (Amphipoda: Lysianassidae: Tryphosinae) from the deep sea Campos Basin, Southwestern Atlantic Ocean.

    PubMed

    Siqueira, Silvana Gomes L; Serejo, Cristiana S

    2014-10-15

    A new species of lysianassid amphipod belonging to the genus Cheirimedon was collected on the continental slope of the Campos Basin, the largest oil reserve in Brazilian waters. This is the first record of the genus Cheirimedon from the Atlantic Ocean, which was previously restricted to the Antarctic and Tasmanian sea. The new species is fully illustrated and compared with related species. Additionally, a world key to the Cheirimedon species is provided. 

  4. Mitochondrial Genetic Differentiation of Spirlin (Actinopterigii: Cyprinidae) in the South Caspian Sea basin of Iran

    PubMed Central

    Seifali, Mahvash; Arshad, Aziz; Moghaddam, Faezeh Yazdani; Esmaeili, Hamid Reza; Kiabi, Bahram H.; Daud, Siti Khalijah; Aliabadian, Mansour

    2012-01-01

    Background Knowledge about Alburnoides remains lacking relative to many other species, resulting in a lack of a systematic position and taxonomic diagnosis. Basic biological information for Alburnoides has been constructed, and it is necessary to understand further and obtain more information about this species. Its phylogenetic relationships are still debated and no molecular data have been used to study this taxon in Iran. A holistic approach for genetic methods was adopted to analyze possible spirlin population differences at selected centers in the south Caspian Sea basin of Iran. Methods The phylogenetic relationships were determined based on 774 base pairs of the mitochondrial cytochrome b gene of 32 specimens of spirlin from nine locations in the south Caspian Sea drainage basin of Iran. The nucleotide sequences were subjected to phylogenetic analysis using the neighbor-joining, maximum parsimony, maximum likelihood, and Bayesian methods. Results The mitochondrial gene tree largely supports the existence of three major clades. The western populations (clade I) may be considered as Alburnoides eichwaldii, whereas the Talar river populations (clade II) are represented as Alburnoides sp.1 and the eastern populations (clade III) may be distinct taxa of Alburnoides sp.2. Conclusion This molecular evidence supports the hypothesis that A. bipunctatus does not exist in the south Caspian Sea basin of Iran, and that the western and eastern populations are distinct taxa. PMID:22654487

  5. Palaeocommunities, diversity and sea-level change from middle Eocene shell beds of the Paris Basin

    NASA Astrophysics Data System (ADS)

    Dominici, Stefano; Zuschin, Martin

    2016-04-01

    The middle Eocene, a time of global transition from greenhouse to icehouse climate, was approached through high-resolution stratigraphy at a few classic localities of the Paris Basin. Quantitative data on the distribution of molluscan species abundance, collected at 12 different shell beds representative of the middle Lutetian and the lower Bartonian, formed the basis for a palaeoecological study. The succession can be subdivided into a hierarchy of depositional sequences, interpreted as the product of relative sea-level change. Abundance distributions are better correlated with 5th-order depositional sequences than geographic locality, suggesting that sea-level played an important role in the distribution of palaeocommunities. Rarefied diversities were measured and compared with analogous data from modern tropical and warm-temperate intertidal and subtidal communities. The palaeoecological analysis shows that sea-level variation is responsible for a major change in the upper part of the middle Lutetian, leading from high-diversity subtidal to low-diversity intertidal and shallow subtidal palaeocommunities. The study did not confirm that the stage-level drop in species richness documented in this basin is related to the global climatic deterioration. Instead, the global climatic signal might be obscured in the Paris Basin by facies control.

  6. GLORIA side-scan imagery of Aleutian basin, Bering Sea slope and Abyssal plain

    SciTech Connect

    Carlson, P.R.; Cooper, A.K.; Gardner, J.V.; Karl, H.A.; Marlow, M.S.; Stevenson, A.J.; Huggett, Q.; Kenyon, N.; Parson, L.

    1987-05-01

    During July-September 1986, about 700,000 km/sup 2/ of continental slope and abyssal plain of the Aleutian basin, Bering Sea, were insonified with GLORIA (Geological Long Range Inclined Asdic) side-scane sonar. A sonar mosaic displays prominent geomorphic features including the massive submarine canyons of the Beringian and the northern Aleutian Ridge slopes and shows well-defined sediment patterns including large deep-sea channels and fan systems on the Aleutian basin abyssal plain. Dominant erosional and sediment transport processes on both the Beringian and the Aleutian Ridge slopes include varieties of mass movement that range from small debris flows and slides to massive slides and slumps of blocks measuring kilometers in dimension. Sediment-flow patterns that appear to be formed by sheet flow rather than channelized flow extend basinward from the numerous canyons and gullies that incise the slopes of the Beringian margin and of Bowers Ridge and some places along the Aleutian Ridge. These Beringian and Bowers canyon sediment sources, however, appear to have contributed less modern sediment to the Aleutian basin than the large, well-defined channel systems that emanate from Bering, Umnak, and Amchitka submarine canyons and extend for several hundred kilometers across the abyssal plain. This GLORIA imagery emphasizes the important contribution of the Aleutian Ridge to modern sedimentation in the deep Bering Sea.

  7. Cassiopidae gastropods, influence of Tethys Sea of the Romualdo Formation (Aptian-Albian), Araripe Basin, Brazil

    NASA Astrophysics Data System (ADS)

    Pereira, Priscilla Albuquerque; Cassab, Rita de Cassia Tardin; Barreto, Alcina Magnólia Franca

    2016-10-01

    The Cassiopidae family belongs to a group of gastropods of the Tethyan Realm, whose origin and dispersion are related a transgression of the Tethys Sea during the Early Cretaceous. The Romualdo Formation in the Araripe Basin, located in Northeast Brazil, presents fossil assemblages with echinoids, bivalves and cassiopid gastropods, indicating a marine sedimentation at the top of the formation. This research reveals three new species of this fauna: Gymnentome (Craginia) beurleni sp. nov., 'Pseudomesalia' ('Pseudomesalia') mennessieri sp. nov and 'Pseudomesalia' ('Pseudomesalia') santanensis sp. nov. We also review two other species: Craginia araripensisBeurlen, 1964 and Gymnentome romualdoiBeurlen, 1964, which we reclassify taxonomically as Paraglauconia (Diglauconia) araripensis and Gymnentome (Gymnentome) romualdoi, respectively; Paraglauconia (Diglauconia) lyrica Maury, 1936 and Gymnentome (Gymnentome) carregozica Maury, 1936 were the first recorded species in the Araripe Basin. The occurrence of these cassiopid gastropod fauna in other basins, such as Sergipe, Potiguar and Parnaíba, indicate the influence of waters coming from the north through the Tethys Sea in the Aptian-Albian and in the marginal continental basins of the Brazilian Northeast.

  8. Basin filling related to the Philippine Sea Plate motion in Beppu Bay, southwest Japan

    NASA Astrophysics Data System (ADS)

    Yamada, Keitaro; Takemura, Keiji; Kuwae, Michinobu; Ikehara, Ken; Yamamoto, Masanobu

    2016-03-01

    Strike-slip basins are one of the most important accumulation spaces for sediment of terrigenous, biogenic, and volcanic origins, and generally include large amount of event deposits. Although these event deposits are important basin filling process, research on this topic, particularly the effects of event deposits, is insufficient. In this study, we discuss sedimentation features based on grain composition and other properties for ca. 3000 year periods in Beppu Bay, which is strike-slip basin located at the western end of an arc-bisecting dextral fault known as Median Tectonic Line (MTL) associated with the northwestward subduction of the Philippine Sea Plate. This sediment is composed of hemipelagic clay and coarser event layers of turbidites referred to as types A, B, and C; ash layers referred to as type D; and other referred to as type E. The turbidite event layers, which accounted for 92% of the total major event layer, with >1 cm thickness, consist of particles related to volcanism, including hydrothermal activity. The events control the regional filling rate and transportation of coarse and heavy volcaniclastic materials. In particular, type A, which accounted for 73% of the total major event layer thickness, is likely induced by earthquakes related to the MTL, according to its age. As a result, the basin filling processes are controlled mainly by tectonics related to the subduction of the Philippine Sea Plate.

  9. Novel active kinetoplastids associated with hypersaline anoxic basins in the Eastern Mediterranean deep-sea

    NASA Astrophysics Data System (ADS)

    Edgcomb, V. P.; Orsi, W.; Breiner, H.-W.; Stock, A.; Filker, S.; Yakimov, M. M.; Stoeck, T.

    2011-10-01

    The combination of nearly saturated salt concentration and corresponding high density, high hydrostatic pressure, absence of light, anoxia, and a sharp chemocline make the deep hypersaline anoxic basins in the Eastern Mediterranean Sea some of the most polyextreme habitats on Earth. Using kinetoplastid-specific primers, we detected kinetoplastid flagellates in some of the harshest deep-sea environments known to date, including some whose small subunit ribosomal RNA gene sequences are not closely related to cultured representatives. Kinetoplastids, including presumably novel representatives appear to be specialists of halocline environments in the Eastern Mediterranean, and to comprise a significant fraction of the protist communities in the brines and haloclines of several basins. Fluorescent in situ hybridization data indicate a novel 'unidentified' sequence clade of kinetoplastids related to bodonids represents as much as 10% of the total protist community in the Discovery Basin halocline. Different kinetoplastid groups are unevenly represented in the different basins and habitats we sampled, which we discuss as a result of environmental selection.

  10. Influence of regional tectonics on halokinesis in the Nordkapp Basin, Barents Sea

    SciTech Connect

    Nilsen, K.T.; Johansen, J.T.; Vendeville, B.C.

    1996-12-31

    Seismic analysis of salt structures in the Nordkapp Basin, a deep salt basin in the southern Barents Sea, combined with experimental modeling suggests that regional tectonics closely controlled diapiric growth. Diapirs formed in the Early Triassic during basement-involved regional extension. The diapirs then rose rapidly by passive growth and exhausted their source layer. Regional extension in the Middle-Late Triassic triggered down-to-the-basin gravity gliding, which laterally shortened the diapirs. This squeezed salt out of diapir stems, forcing diapirs to rise, extrude, and form diapir overhangs. After burial under more than 1000 m of Upper Triassic-Lower Cretaceous sediments, the diapirs were rejuvenated by a Late Cretaceous episode of regional extension and gravity gliding, which deformed their thick roofs. After extension, diapirs stopped rising and were buried under 1500 m of lower Tertiary sediments. Regional compression of the Barents Sea region in the middle Tertiary caused one more episode of diapiric rise. Diapirs in the Nordkapp Basin are now extinct.

  11. Diachronous Growth of Normal Fault Systems in Multiphase Rift Basins: Structural Evolution of the East Shetland Basin, Northern North Sea

    NASA Astrophysics Data System (ADS)

    Claringbould, Johan S.; Bell, Rebecca E.; A-L. Jackson, Christopher; Gawthorpe, Robert L.; Odinsen, Tore

    2015-04-01

    Our ability to determine the structural evolution and interaction of fault systems (kinematically linked group of faults that are in the km to 10s of km scale) within a rift basin is typically limited by the spatial extent and temporal resolution of the available data and methods used. Physical and numerical models provide predictions on how fault systems nucleate, grow and interact, but these models need to be tested with natural examples. Although field studies and individual 3D seismic surveys can provide a detailed structural evolution of individual fault systems, they are often spatially limited and cannot be used examine the interaction of fault systems throughout the entire basin. In contrast, regional subsurface studies, commonly conducted on widely spaced 2D seismic surveys, are able to capture the general structural evolution of a rift basin, but lack the spatial and temporal detail. Moreover, these studies typically describe the structural evolution of rifts as comprising multiple discrete tectonic stages (i.e. pre-, syn- and post-rift). This simplified approach does not, however, consider that the timing of activity can be strongly diachronous along and between faults that form part of a kinematically linked system within a rift basin. This study focuses on the East Shetland Basin (ESB), a multiphase rift basin located on the western margin of the North Viking Graben, northern North Sea. Most previous studies suggest the basin evolved in response to two discrete phases of extension in the Permian-Triassic and Middle-Late Jurassic, with the overall geometry of the latter rift to be the result of selective reactivation of faults associated with the former rift. Gradually eastwards thickening intra-rift strata (deposited between two rift phases) that form wedges between and within fault blocks have led to two strongly contrasting tectonic interpretations: (i) Early-Middle Jurassic differential thermal subsidence after Permian-Triassic rifting; or (ii

  12. Sea level rise of semi-enclosed basins: deviation of Adriatic and Baltic sea level from the mean global value.

    NASA Astrophysics Data System (ADS)

    Scarascia, Luca; Lionello, Piero

    2015-04-01

    Future sea level rise (SL), which represents today one of the major threats that are caused by climate change, will not be uniform. Regional differences are crucial for 40% of the world population, which is located in the coastal zone. To explore the mechanisms linking regional SL to climate variables is very important in order to provide reliable future projections. This study focuses on two semi-enclosed basins, the Adriatic and Baltic Sea and investigates the deviation of their SL from the mean global value. In fact, past deviations of the SL of these two basins from the global value have been observed and can be attributed to large scale factors (such as teleconnections) and regional factors, such as the inverse barometric effect, the wind stress, the thermosteric and halosteric effects. The final goal of this work is to assess to which extent the Adriatic and Baltic SL will depart from the mean global value in the next decades and at the end of 21st century. This is achieved by analyzing deviations of the mean SL of the Baltic and Adriatic Sea from the global mean SL during the 20th century and investigating which factors can explain such deviations. A multivariate linear regression model is built and used to describe the link between three large scale climate variables which are used as predictors (mean sea level pressure, surface air temperature and precipitation), and the regional SL deviation (the predictand), computed as the difference between the regional and the global SL. At monthly scale this linear regression model provides a good reconstruction of the past variability in the cold season during which it explains 60%-70% of the variance. Summer reconstruction is substantially less successful and it represents presently the main limit of the model skill. This linear regression model, forced by predictors extracted from CMIP5 multi-model simulations, is used to provide projections of SL in the Adriatic and Baltic Sea. On the basis of the projections

  13. The deeper structure of the southern Dead Sea basin derived from neural network analysis of velocity and attenuation tomography

    NASA Astrophysics Data System (ADS)

    Braeuer, Benjamin; Haberland, Christian; Bauer, Klaus; Weber, Michael

    2014-05-01

    The Dead Sea basin is a pull-apart basin at the Dead Sea transform fault, the boundary between the African and the Arabian plates. Though the DSB has been studied for a long time, the available knowledge - based mainly on surface geology, drilling and seismic reflection surveys - gives only a partial picture of its shallow structure. Therefore, within the framework of the international DESIRE (DEad Sea Integrated REsearch) project, a dense temporary local seismological network was operated in the southern Dead Sea area. Within 18 month of recording 650 events were detected. In addition to an already published tomography study revealing the distribution of P velocities and the Vp/Vs ratios a 2D P-wave attenuation tomography (parameter Qp) was performed. The neural network technique of Self-organizing maps (SOM) is used for the joint interpretation of these three parameters (Vp, Vp/Vs, Qp). The resulting clusters in the petrophysical parameter space are assigned to the main lithological units below the southern part of the Dead Sea basin: (1) The basin sediments characterized by strong attenuation, high vp/vs ratios and low P velocities. (2) The pre-basin sediments characterized by medium to strong attenuation, low Vp/Vs ratios and medium P velocities. (3) The basement characterized by low to moderate attenuation, medium vp/vs ratios and high P velocities. Thus, the asymmetric southern Dead Sea basin is filled with basin sediments down to depth of 7 to 12 km. Below the basin sediments, the pre-basin sediments are extending to a depth between 13 and 18 km.

  14. Implication of biomarkers signatures of the Ulleung Basin, East Sea, during the Pleistocene

    NASA Astrophysics Data System (ADS)

    Choi, Jiyoung; Lee, Kyung Eun; Kim, Ji-Hoon; Bahk, Jang-Jun; Yoo, Dong-Geun

    2014-05-01

    In this study, the molecular distribution of the n-alkanes, alkenone and C/N ratio and δ13C of bulk sediment were used to assess changes in organic matter (OM) source and transport which could be related with paleoclimate change. The proxy records corresponding to the Pleistocene have been obtained from the well-studied the Ulleung Basin Gas Hydrate Expedition 2 (UBGH2) site 11 in the Ulleung Basin, East Sea. The distribution of carbon preference index (CPI) of n-alkane encountered in this study confirmed the importance of terrestrial OM in the marine sediment. Alkenone has been widely applied for sea surface temperature (SST) reconstruction. The data results show that CPI values generally increase with decreasing paleo-SST. Plot of C/N ratio versus δ13C shows a predominance of marine algae origin in the study area. It may indicate that the minimum CPI in warm period is related with the contribution of probably enhanced biodegradation, while the maximum CPI value in cold period result from restrain of OM input associated with sea level lowering. It is likely that the vertical variations of the biomarkers signature reflect the shifts in sedimentary environment and transportation related with change of ocean currents and sea level during the Pleistocene period.

  15. Chemostratigraphy of Upper Cretaceous chalk sequences in Norwegian-Danish basin and North Sea Central Trough

    SciTech Connect

    Joergensen, N.O.

    1987-05-01

    Geochemical studies of subsurface sections and outcrops in the Upper Cretaceous chalk sequences from the Norwegian-Danish basin and the North Sea Central Trough have resulted in a detailed chemostratigraphy for these strata. The most applicable chemostratigraphic markers are based on the distribution of strontium, magnesium, manganese, the /sup 13/C//sup 12/C ratio, and the variations in the carbonate contents. It is demonstrated that the chemostratigraphic approach is valid at two levels: (1) a superior chemostratigraphy in which deep-sea cores from the Atlantic Ocean and sections from western Europe are correlated on the basis of significant geochemical anomalies and long-term variations most likely induced by oceanic geochemical cycles and sea level fluctuations; (2) a subordinate but detailed intrabasinal chemostratigraphic correlation which primarily reflects the physicochemical conditions in the depositional environment. The Upper Cretaceous chemostratigraphy established in the Danish area allows a detailed correlation between relatively continuous chalk sequences in the Norwegian-Danish basin and the rather condensed and hiati-influenced sections in the oil fields of the North Sea. The results emphasize the applicability of chemostratigraphy in the subsurface exploration for hydrocarbon reservoirs in chalk.

  16. Macroparasite community in molluscs of a tidal basin in the Wadden Sea

    NASA Astrophysics Data System (ADS)

    Thieltges, David W.; Krakau, Manuela; Andresen, Henrike; Fottner, Silke; Reise, Karsten

    2006-12-01

    We provide a quantitative inventory of macroparasites in intertidal molluscs from a tidal basin in the Wadden Sea (eastern North Sea). Gastropods and bivalves contained a species rich macroparasite community consisting of trematodes (26 species), turbellarians (1), nematodes (1), copepods (2) and polychaetes (1) in 3,800 host individuals from 10 host species. Highest parasite burdens were observed in the gastropods Hydrobia ulvae and Littorina littorea and in the bivalves Cerastoderma edule and Mytilus edulis. In contrast, only one parasite species and no trematodes were found in Crepidula fornicata. The parasite community in the molluscs was similar to other Western European localities but some parasite species showed obvious differences, related to the large-scale distribution of intermediate and final hosts. Parasitism seems to be a common phenomenon in molluscs of the Wadden Sea and hence the detrimental effects observed in experiments can be expected to frequently happen in the field.

  17. Geophysical Evidence for the Occurrence of Gas Hydrate in the Ulleung Basin, East Sea off Korea

    NASA Astrophysics Data System (ADS)

    Yoo, D.-G.; Kim, G.-Y.; Kang, D.-H.; Ryu, B.-J.

    2009-04-01

    Analysis of multi-channel seismic reflection data collected from the Ulleung Basin, East Sea reveals five types of seismic indicators that imply the existence of gas hydrate including the bottom simulating reflector (BSR), seismic chimney/column, acoustic blanking, enhanced reflections, and gas seepage. The BSR, the most common seismic indicator in the Ulleung Basin, is of high amplitude and good continuity in the southern slope, whereas it is of low amplitude and poor continuity in the northern basin. Seismic chimney/column of reduced reflectivity and velocity pull-up is commonly seen in the central basin and northeastern part of the study area and suggests that imply the probability of gas hydrate or gas fluids. Acoustic blanking of reduced reflectivity partly occurs on the central basin consisting of turbidite/pelagic sediment. Acoustic blanking related to column structures is common in the southeastern slope of the study area. Enhanced reflection below the BSR is seen in the western slope of the area and suggests the existence of free gas due to strong negative amplitude. Gas seepages combined with dome structures and pockmark are widely distributed on the southern slope, consisting of debris flow deposits.

  18. Salt diapirs in the Dead Sea basin and their relationship to Quaternary extensional tectonics

    USGS Publications Warehouse

    Al-Zoubi, A.; ten Brink, U.S.

    2001-01-01

    Regional extension of a brittle overburden and underlying salt causes differential loading that is thought to initiate the rise of reactive diapirs below and through regions of thin overburden. We present a modern example of a large salt diapir in the Dead Sea pull-apart basin, the Lisan diapir, which we believe was formed during the Quaternary due to basin transtension and subsidence. Using newly released seismic data that are correlated to several deep wells, we determine the size of the diapir to be 13 x 10 km. its maximum depth 7.2 km. and its roof 125 m below the surface. From seismic stratigraphy, we infer that the diapir started rising during the early to middle Pleistocene as this section of the basin underwater rapid subsidence and significant extension of the overburden. During the middle to late Pleistocene, the diapir pierced through the extensionally thinned overburden, as indicated by rim synclines, which attest to rapid salt withdrawal from the surrounding regions. Slight positive topography above the diapir and shallow folded horizons indicate that it is still rising intermittently. The smaller Sedom diapir, exposed along the western bounding fault of the basin is presently rising and forms a 200 m-high ridge. Its initiation is explained by localized E-W extension due monoclinal draping over the edge of a rapidly subsiding basin during the early to middle Pleistocene, and its continued rise by lateral squeezing due to continued rotation of the Amazyahu diagonal fault. ?? 2001 Elsevier Science Ltd. All rights reserved.

  19. Seismic stratigraphy of the Tyrrhenian Sea (western Mediterranean Sea) based on ODP leg results: Consequences for the basin evolution

    SciTech Connect

    Mascle, J.; Rehault, J.

    1988-08-01

    A revision of the seismic stratigraphy of the Tyrrehenian Sea is based on detailed calibrations between a dense network of single-channel seismic reflection lines, about 2,000 km of recent multichannel seismic profiles, and the seven sites drilled within the Tyrrhenian in 1986 during the Ocean Drilling Program Leg 107. These correlations substantiate that the basin has been submitted to a succession of short-lived rifting episodes progressively shifting toward the southeast and leading to the local creation of discrete oceanic crust floored basins. Most of the Tyr-rhenian basins and margins have been created in a very short time (between 8 and 2 m.y. in age) and are much younger than previously anticipated. Rifting processes have been acting on a very heterogeneous continental basement (including several suture zones); drifting has created small oceanic subbasins also floored by a very heterogeneous magmatic basement (including serpentinized peridotites). The hypothesis of an asymmetric evolution facilitated by one or several crustal detachment fault systems and driven by geodynamic mechanisms of the bordering collision/subduction is considered.

  20. On the origin of late Holocene sea-level highstands within equatorial ocean basins

    NASA Astrophysics Data System (ADS)

    Mitrovica, J. X.; Milne, G. A.

    2002-11-01

    Late Holocene sea-level highstands of amplitude ˜3 m are endemic to equatorial ocean basins. These highstands imply an ongoing and moderate, sub-mm/yr, sea-level fall in the far field of the Late Pleistocene ice cover that has long been linked to the process of glacial isostatic adjustment (GIA; Clark et al., 1978). Mitrovica and Peltier (1991) coined the term 'equatorial ocean syphoning' to describe the GIA-induced sea-level fall and they provided the first physical explanation for the process. They argued that water migrated away from far-field equatorial ocean basins in order to fill space vacated by collapsing forebulges at the periphery of previously glaciated regions. We provide a complete physical explanation for the origin of equatorial ocean syphoning, and the associated development of sea-level highstands, using numerical solutions of the equation that governs meltwater redistribution on spherical, viscoelastic Earth models. In particular, we separate the total predicted sea-level change into contributions associated with ice and meltwater loading effects, and, by doing so, isolate a second mechanism that contributes significantly to the ocean syphoning process. Ocean loading at continental margins induces a 'levering' of continents and a subsidence of offshore regions that has also long been recognized within the GIA literature (Walcott, 1972). We show that the influx of water into the volume created by this subsidence produces a sea-level fall at locations distant from these margins—indeed over the major ocean basins—that is comparable in amplitude to the syphoning mechanism isolated by Mitrovica and Peltier (1991).

  1. Structures and geometries of the Tajo Basin crust, Spain: Results of a magnetotelluric investigation compared to seismic and thermal models

    NASA Astrophysics Data System (ADS)

    Schmoldt, J.-P.; Jones, A. G.; Rosell, O.

    2014-09-01

    The Tajo Basin and Betic Mountain Chain in the south central region of the Iberian Peninsula were chosen for investigation in the first phase of the magnetotelluric (MT) component of the PICASSO (Program to Investigate the Convective Alboran Sea System Overturn) project. The MT results provide information about the electrical conductivity distribution in previously unprobed subsurface regions, as well as complimenting and enhancing results of prior geological and geophysical investigations thereby enabling the definition of a petrological subsurface model and a comprehensive understanding about the tectonic setting. Two-dimensional (2-D) inversion of the MT data provides enhanced insight into Iberian subsurface geology in the crust. The most striking features of the final model are (i) a distinct vertical interface within the Variscan basement beneath the center of the Tajo Basin that is spatially associated with the boundary between regions with and without substantial Alpine deformation, and (ii) a middle to lower crustal conductive anomaly that can be related to remnants of asthenospheric intrusion in connection with Pliocene volcanic events in the Calatrava Volcanic Province. For the latter, effects of hydrous phases are inferred that may originate from dehydration processes within the subducting slab beneath Alboran Domain and Betic Mountain Chain.

  2. Tectonic Subsidence Analysis of the Pearl River Mouth Basin, Northern South China Sea

    NASA Astrophysics Data System (ADS)

    Tang, X.; Huang, S. S. X. E. C.; Zhuang, W.; LIU, Z.; Duan, W.; Hu, S.

    2015-12-01

    The Pearl River Mouth Basin (PRMB hereafter) in the northern margin of the South China Sea has attracted great attention not only because of its special tectonic location but also for its abundant hydrocarbon resources. Tectonic evolution controls the petroleum geological condition of hydrocarbon-bearing basins. Efforts have been made to understand the tectonic evolution of this basin. However, many issues about the tectonic features and the evolution process of this basin, such as the age of the breakup unconformities and the anomalously accelerated subsidence during the post-rifting stage, remain controversial. Here we employ tectonic subsidence analysis of sedimentary basins, a technique of removing isostatic loading and compaction effects by back-stripping, to investigate the tectonic controls on the basin formation of the PRMB. We performed the analysis on 4 drill wells and 43 synthetic wells constructed based on recently acquired seismic profiles. The result shows that tectonic subsidence in the eastern sags of the PRMB began to decrease at ~30Ma while in the western sags the onset was ~23.8Ma. This suggests that the break-up time i.e. the end of rifting in the PRMB is earlier in the eastern sags than in the western sags. Abnormally accelerated tectonic subsidence occurred between 17.5-16.4Ma during the post-rifting stage, at an average subsidence rate as high as 301.9m/Ma. This phenomenon discriminates the PRMB from the category of classical Atlantic passive continental marginal basins, of which the tectonic subsidence during the post-rifting stage decays exponentially. The main objective of this paper is to provide insights into the geological and geodynamic evolution of the PRMB. The result bears significance to hydrocarbon exploration in this region.

  3. Anatomy of mass transport deposits in the Dead Sea: sedimentary processes in an active tectonic hypersaline basin

    NASA Astrophysics Data System (ADS)

    Waldmann, Nicolas; Hadzhiivanova, Elitsa; Neugebauer, Ina; Brauer, Achim; Schwab, Markus; Frank, Ute; Dulski, Peter

    2014-05-01

    Continental archives such as interplate endorheic lacustrine sedimentary basins provide an excellent source of data for studying regional climate, seismicity and environmental changes through time. Such is the case for the sediments that were deposited in the Dead Sea basin, a tectonically active pull-apart structure along the Dead Sea fault (DSF). This elongated basin is characterized by steep slopes and a deep and flat basin-floor, which are constantly shaped by seismicity and climate. In this study, we present initial results on the sedimentology and internal structure of mass transport deposits in the Pleistocene Dead Sea. The database used for this study consists of a long core retrieved at ~300 m water depth in the deepest part of the Dead Sea as part of an international scientific effort under the auspice of the ICDP. Micro-facies analysis coupled by elemental scanning (µXRF), granulometry and petrophysical measurements (magnetic susceptibility) have been carried out on selected intervals in order to decipher and identify the source-to-sink processes and controlling mechanisms behind the formation of mass transport deposits. The findings of this study allowed defining and characterizing the mass transport deposits into separate sedimentary facies according to the lake level and limnological conditions. Investigating sediments from the deep Dead Sea basin allowed better understanding and deciphering the depositional processes in relation with the tectonic forces shaping this basin.

  4. Hydrographic properties of separate residual basins of the Aral Sea: in situ observations and intercomparison

    NASA Astrophysics Data System (ADS)

    Izhitskiy, Alexander; Zavialov, Peter; Kurbaniyazov, Abilgazi

    2015-04-01

    Desiccation of the Aral Sea continued intensively throughout the last decade. As reported by NASA and widely commented in mass media, the eastern lobe of the Southern Sea (i.e., the Large Aral Sea) dried up completely in the summer of 2014. Only the western basin of the Large Sea remains there, and the separation of its northernmost portion called Chernyshev Bay is imminent. The northern part of the former Aral Sea known as the Small Aral Sea has separated decades ago and eventually stabilized thanks to a man-made dam trapping all of the Syr Daria discharges in the Small Sea. In addition, the Tschebas Bay, formerly a large bay of the Aral Sea, has evolved into a separate lake with relatively stable boundaries. In this way, the present-day Aral Sea should be considered as a system of separated water bodies with a common origin but different fates and very different physical, chemical, and biological features. In the presented study, we focus on hydrophysical state of the newly individual parts of the former Aral Sea. The comparative investigation is based on field data collected during two surveys of Shirshov Institute of Oceanology to the Aral Sea which took place in the fall season of 2014. In situ measurements including CTD profiling and water sampling were carried in the central western basin of the Large Aral (Aktumsuk area), in the northern extremity of the western Large Aral (Chernyshev bay), in Tschebas Lake, and the western part of the Small Sea (Shevchenko Bay). The analysis of direct observations together with the satellite data allows clarifying main processes and factors determining the physical state of the residual water bodies. According to the results of the in situ observations, three different types of hydrographic structure were documented in the lakes of the former Aral Sea. Salinity of Tschebas Lake water was around 92 g/kg, with the water column fully mixed from surface to bottom. The CTD measurements conducted in the Shevchenko bay of the

  5. Back-arc basin opening and closure along the southern margin of the Sea of Japan

    NASA Astrophysics Data System (ADS)

    Sato, Hiroshi; Claringbould, Johan; Ishiyama, Tatsuya; Kato, Naoko; Abe, Susumu; Kawasaki, Shinji

    2016-04-01

    Following the tsunami disaster produced by 2001 Off-Tohoku earthquake (M9) along the Pacific coast of Japan, the Japanese government started an intense evaluation of tsunami hazards. This evaluation spanned along the full Japanese coast, including the Sea of Japan coast on the western side of the Japan arc. In the Sea of Japan, tsunamis are produced by crustal faults. As the longer interval of faulting activity, the historical records of tsunamis in the Sea of Japan are not enough for the evaluation of tsunami height. Thus, the evaluation is carried out based on structural analyses of the margin of the Sea of Japan. To get better understanding of the present-day structural geometry and develop a source-fault model in this region, intense seismic reflection profiling has been carried out since 2013. We introduce the results of the seismic reflection profiles and discuss the structural evolution of the southern margin of the Sea of Japan. 2D seismic reflection profiles were acquired using 1950 cu. in. air-gun and 2100 m streamer cable. The seismic profiles provide the image image up to 3 seconds TWT. The southern margin of the Sea of Japan was produced by back-arc opening and post-rift deformation, and the structural evolution of this area is divided into several stages: rifting (25 - 14 Ma), post-rift compression (14 - 5 Ma), weak thrusting (5 - 1 Ma), and strike-slip deformation (1 Ma to present). During the rifting stage that is associated with the fan-shaped opening of the Sea of Japan, grabens and half-grabens were formed trending parallel to the extension of SW-Japan arc. These grabens were filled by syn-rift sediments, and the maximum thickness of basin fill is observed along the southern margin of the rifted crust. The opening of the Sea of Japan ceased as a result of the collision of Izu-Bonin-Mariana arc system at the Izu collision zone on the central part of Honshu, Japan. Soon after the this event, the young Shikoku basin within the Philippine Sea plate

  6. Greater role for Atlantic inflows on sea-ice loss in the Eurasian Basin of the Arctic Ocean.

    PubMed

    Polyakov, Igor V; Pnyushkov, Andrey V; Alkire, Matthew B; Ashik, Igor M; Baumann, Till M; Carmack, Eddy C; Goszczko, Ilona; Guthrie, John; Ivanov, Vladimir V; Kanzow, Torsten; Krishfield, Richard; Kwok, Ronald; Sundfjord, Arild; Morison, James; Rember, Robert; Yulin, Alexander

    2017-04-06

    Arctic sea-ice loss is a leading indicator of climate change and can be attributed, in large part, to atmospheric forcing. Here, we show that recent ice reductions, weakening of the halocline, and shoaling of intermediate-depth Atlantic Water layer in the eastern Eurasian Basin have increased winter ventilation in the ocean interior, making this region structurally similar to that of the western Eurasian Basin. The associated enhanced release of oceanic heat has reduced winter sea-ice formation at a rate now comparable to losses from atmospheric thermodynamic forcing, thus explaining the recent reduction in sea-ice cover in the eastern Eurasian Basin. This encroaching "atlantification" of the Eurasian Basin represents an essential step toward a new Arctic climate state, with a substantially greater role for Atlantic inflows.

  7. Recognition of relict Mesozoic Dongsha Basin in the northern margin, South China Sea and its implication

    NASA Astrophysics Data System (ADS)

    Yan, Pin; Wang, Yanlin

    2015-04-01

    The Pearl River Mouth Basin (PRMB) is dominated by NE-trending rift architecture produced mainly during Cenozoic Era. It comprises a series of grabens built up with thick Paleogene and thick Neogene sediments, up to 12000 m, and dividing basement highs composing Yanshanian granitic rocks. Though previously considered as one constituent part of PRMB in the southeast, Dongsha Basin displays major differences in sedimentary architecture and tectonic framework. Firstly, Dongsha Basin is characterized by a prominent angular unconformity, interpreted as a spectacular planation or rough erosion surface which separates the sediment column into two distinct parts. It is interpreted with accumulating seismic and drill data that the underlying strata comprise Early Cretaceous terrestrial, Jurassic marine and possibly Triassic sedimentary rocks totaling to 4~9 km thick, whereas the overlying strata are very thin (usually 0.5~1 km in whole) composing mainly Neogene sediments. The major sedimentary hiatus between them corresponds to the Late Cretaceous to mid-Miocene Epoch, well during the rifting to spreading process when the PRMB developed. Secondly, unlike the PRMB, the Dongsha Basin has suffered considerably less extension except its boundary areas, and actually remained as a relatively stable block though Cenozoic Era. Moreover, there are a few compressive open fold structures within the buried Mesozoic strata over the central Dongsha Basin. These folds trend in NNE and are characterized mostly by few minor growing upthrust faults with offsets in the order of few tens to hundreds meter. The upthrust faults dipped mostly southeastward against the northwestward subduction of paleo-Pacific plate as postulated in other previous study. The blind folds featured more like back-thrust growth tectonics, formed a broad NNE-SSW trending belt, obviously oblique to the trend of northern margin of the South China Sea and the PRMB as well. In a few recent models, the most prominent

  8. Kinematics of back-arc inversion of the Western Black Sea Basin

    NASA Astrophysics Data System (ADS)

    Munteanu, I.; Matenco, L.; Dinu, C.; Cloetingh, S.

    2011-10-01

    Back-arc basin evolution is driven by processes active at the main subduction zone typically assuming the transition from an extensional back-arc, during the retreat of a mature slab, to a contractional basin, during high-strain collisional processes. Such a transition is observed in the Black Sea, where the accurate quantification of shortening effects is hampered by the kinematically unclear geometries of Cenozoic inversion. By means of seismic profiles interpretation, quantified deformation features and associated syn-tectonic geometries on the Romanian offshore, this study demonstrates that uplifted areas, observed by exploration studies, form a coherent thick-skinned thrust system with N-ward vergence. Thrusting inverted an existing geometry made up by successive grabens that were inherited from the Cretaceous extensional evolution. The shortening started during late Eocene times and gradually affected all areas of the Western Black Sea Basin during Oligocene and Miocene times, deformation being coherently correlated across its western margin. The mechanism of this generalized inversion is the transmission of stresses during the collision recorded in the Pontides-Balkanides system. Syn-tectonic sedimentation in the Western Black Sea demonstrates that this process was continuous and took place through the onset of gradual shortening migrating northward. Although the total amount of shortening is roughly constant in an E-W direction, individual thrusts have variable offsets, deformation being transferred between structures located at distance across the strike of the system. The Black Sea example demonstrates that the vergence and offset of thrusts can change rapidly along the strike of such a compressional back-arc system. This generates apparently contrasting geometries that accommodate the same orogenic shortening.

  9. Seismic Stratigraphy around Continent-Ocean Boundary in the NW Sub-basin, Northern South China Sea

    NASA Astrophysics Data System (ADS)

    Chang, S. P.; Liu, C. S.; Hsu, H. H.; Chang, J. H.

    2015-12-01

    The northern continental margin of the South China Sea (SCS) is a passive margin, and have experienced rifting and seafloor spreading. From continental shelf to deep sea basin, the nature of the crust gradually changes from continental crust to oceanic crust. Many studies use a term "continent-ocean boundary (COB)", to describe the boundary between these two kinds of crust. This boundary is roughly located along the boundary between slope and deep sea basin, and roughly parallels to the 3000 m isobath in the northern SCS. This study analyzes many multiple channel seismic reflection profiles in the northern continental margin of the SCS, and has identified an angular unconformity between the slope and deep sea basin deposits at the COB in the NW sub-basin area. This unconformity extends from continental slope to NW sub-basin near the COB. Strata beneath the unconformity downlap to the basement. Furthermore, there is a strong reflector beneath the unconformity, and this strong reflector, called "Tom", represents a hiatus which was recognized by biostratigraphic analyses from Site 1148 of ODP Leg 184. The strata between the unconformity surface and reflector Tom pinch toward deep sea basin, and then the unconformity and reflector Tom merge into one reflector. Therefore, the unconformity might be an erosional surface. The strata covered the unconformity onlap the unconformity. Some portions of the COB have intrusions forming basement high, and the unconformity and strata are coherent with basement relief. The unconformity has been interpreted as a normal fault in some previous studies, but our study distinguishes it as an erosional surface. Besides, some previous studies consider the bottom of the sedimentary layers in the NW sub-basin as the onset of depositing deep sea environment, and suggested that it is related to the onset of seafloor spreading. However, we interpret the angular unconformity as the onset of deep sea environment, and it differs from the onset of

  10. A study of in-situ stress magnitudes in the North Sea basin from borehole measurements

    NASA Astrophysics Data System (ADS)

    Edwards, Stephen Tean

    The stress field in the crust is a fundamental first order geophysical property that is intimately linked to the dynamic behavior of the Earth. This project has concentrated on crustal stress magnitudes as these are generally less well understood than stress orientations. Leak-off tests have been evaluated as a potential method of stress magnitude estimation, and the most suitable uses of leak-off data to estimate stress magnitudes have been defined. Vertical stresses have been estimated using geophysical logs. The variations of stress with depth, geographic domain, lithology and pore pressure have been has been studied in order to investigate the origins of crustal stress in the North Sea basin. The most reliable method of stress magnitude determination is the hydraulic fracturing (hydro-frac) method, however, hydro-frac data is rare. By contrast the leak-off test is performed routinely by the oil industry, with several tests in each hole drilled. An extensive 3-dimensional dataset of leak-off pressures therefore exists for the North Sea. Datasets have been obtained for the southern North Sea, and also from onshore boreholes drilled by UK Nirex, where leak-off tests and hydro-fracs have been performed in the same holes. This has enabled the leak-off test to be evaluated as a possible stress determination method. From these datasets, it is concluded that the trends of leak-off pressure with depth reflect changes in the minimum horizontal stress magnitude (Oh) with depth. Where leak-off test pressure records are available, it is seen that the shape of many leak-off test pressure/volume plots resemble those of hydro-frac re-opening plots, and that in these leak-off tests, the leak-off pressure is very close to the hydro-frac determined Oh. Furthermore, when leak-off tests are conducted carefully, a slightly extended test procedure can yield even better estimates of Oh. Over 3,000 leak-off test results have been obtained from throughout the North Sea. The trends of

  11. Late Quaternary co-seismic sedimentation in the Sea of Marmara's deep basins

    NASA Astrophysics Data System (ADS)

    Beck, Christian; Mercier de Lépinay, Bernard; Schneider, Jean-Luc; Cremer, Michel; Çağatay, Namik; Wendenbaum, Evrard; Boutareaud, Sébastien; Ménot, Guillemette; Schmidt, Sabine; Weber, Olivier; Eris, Kadir; Armijo, Rolando; Meyer, Bertrand; Pondard, Nicolas; Gutscher, Marc-André; Turon, J.-L.; Labeyrie, L.; Cortijo, E.; Gallet, Y.; Bouquerel, Hélène; Gorur, N.; Gervais, A.; Castera, M.-H.; Londeix, L.; de Rességuier, A.; Jaouen, A.; Marmacore Cruise Party

    2007-07-01

    The deep, northern, part of the Sea of Marmara (northwestern Turkey) is composed of several aligned, actively subsiding, basins, which are the direct structural and morphological expression of the North-Anatolian Fault's northern branch. The last 20 kyr of their sedimentary fill (non-marine before 12 kyr BP) have been investigated through giant piston coring onboard R/V MARION-DUFRESNE (MARMACORE Cruise, 2001) and by chirp sub-bottom profiler onboard R/V ATALANTE during MARMARASCARPS Cruise (2002). Especially during the lacustrine stage, the infilling of the deep basins (Tekirdağ, Central, Kumburgaz, and Çinarcic Basins; up to 1250-m depth) was dominated by turbidites (with coarse mixed siliciclastic and bioclastic basal parts), intercalated in "hemipelagic-type" fine-grained calcareous and slightly siliceous clays. Often the turbidites show strong segregation and a sharp boundary between a coarse lower part and a suspended-load upper part. In the Central Basin, 8 m of a unique sedimentary event include a 5 to 8-m thick "homogenite" well imaged on seismic profiles. The latter is interpreted as related to a major - possibly earthquake-triggered - tsunami effect, as described in the Eastern Mediterranean by Kastens and Cita [Kastens K. and Cita M.B., 1981. Tsunami-induced sediment transport in the abyssal Mediterranean Sea. Geological Society of America Bulletin, 92:845-857]. In the marine (Holocene) upper part of the sedimentary fill, repeated to-and-from structures, affecting silt or fine sand, are evidencing seiche-like effects and, thus, earthquake triggering. Detailed correlations between two deep coring sites (at 1250 m and 1200 m) indicate more than 100% over-thickening in the deepest one; this implies specific processes of distribution of terrigenous input by dense currents (high kinetic energy, seiche effects, complex reflections on steep slopes). The peculiar sedimentary fill of the Sea of Marmara's Central Basin is interpreted as a direct consequence of

  12. Sequence stratigraphy and hydrocarbon potential of the Phu Khanh Basin offshore central Vietnam, South China Sea

    SciTech Connect

    Lee, G.H.; Watkins, J.S.

    1996-12-31

    The Phu Khanh Basin offshore central Vietnam is one of the few untested basins on the Vietnam margin of the South China Sea. Analysis of over 1,600 km of multi-channel seismic reflection data indicates that the Phu Khanh Basin follows a typical rift-margin order: faulted basement, synrift sedimentation, a breakup unconformity, and postrift sedimentation. Postrift sedimentation consists of a transgressive phase characterized by ramp-like depositional geometries followed by a regressive phase characterized by prograding sequences. An early middle Miocene unconformity separates these two phases. During the transgressive phase rising sea level provided favorable conditions for carbonate buildup development. The regressive interval contains a number of third-order depositional sequences composed of seismically resolvable lowstand, highstand, and rarely, transgressive systems tracts. Lacustrine sediments deposited in graben and half-graben lakes during the rifting stage are probably the principal source rocks. Fractured and/or weathered basement, carbonate complexes, basinfloor fans, and shallows water sands may have good reservoir quality. Potential traps include basement hills, carbonate complexes, fault taps, and stratigraphic traps within lowstand systems tracts. Hydrocarbon indicators such as flat spots, bright spots, gas chimneys with gas mounds on the seafloor occur at a number of locations.

  13. Sequence stratigraphy and hydrocarbon potential of the Phu Khanh Basin offshore central Vietnam, South China Sea

    SciTech Connect

    Lee, G.H. ); Watkins, J.S. )

    1996-01-01

    The Phu Khanh Basin offshore central Vietnam is one of the few untested basins on the Vietnam margin of the South China Sea. Analysis of over 1,600 km of multi-channel seismic reflection data indicates that the Phu Khanh Basin follows a typical rift-margin order: faulted basement, synrift sedimentation, a breakup unconformity, and postrift sedimentation. Postrift sedimentation consists of a transgressive phase characterized by ramp-like depositional geometries followed by a regressive phase characterized by prograding sequences. An early middle Miocene unconformity separates these two phases. During the transgressive phase rising sea level provided favorable conditions for carbonate buildup development. The regressive interval contains a number of third-order depositional sequences composed of seismically resolvable lowstand, highstand, and rarely, transgressive systems tracts. Lacustrine sediments deposited in graben and half-graben lakes during the rifting stage are probably the principal source rocks. Fractured and/or weathered basement, carbonate complexes, basinfloor fans, and shallows water sands may have good reservoir quality. Potential traps include basement hills, carbonate complexes, fault taps, and stratigraphic traps within lowstand systems tracts. Hydrocarbon indicators such as flat spots, bright spots, gas chimneys with gas mounds on the seafloor occur at a number of locations.

  14. Magnetic anomaly pattern of the Marsili Basin (southern Tyrrhenian Sea, Italy): Ultrafast oceanic spreading or not?

    NASA Astrophysics Data System (ADS)

    Speranza, F.; Nicolosi, I.; Chiappini, M.

    2011-12-01

    The Marsili Basin is a ~100x70 km flat and deep (3000-3500 m) basin located in the southern Tyrrhenian Sea, encircling the huge 16x50 km (and ~3000 m high) Marsili seamount. Though results from ODP Site 650 had proven more than twenty years ago the oceanic nature of the Marsili Basin, oceanic-type linear magnetic anomalies above the basin floor were clearly documented only in the last few years. Nicolosi et al. (2006) reported on spectral analysis of both airborne and shipborne magnetic maps from the Marsili Basin, and showed the occurrence of six magnetic anomaly stripes covering the flat basin floor, symmetrically arranged with respect to a central positive anomaly located above the Marsili seamount. By assuming that the two 17 km wide lateral normal polarity stripes formed during the Olduvai chron (1.77-1.95 Ma), Nicolosi et al. (2006) suggested that the Marsili Basin opened at the ultrafast full-spreading rate of ~19 cm/yr between 2.1 and 1.6 Ma. They also proposed that the normally magnetized Marsili seamount formed during the Brunhes chron (after 0.78 Ma), when slower spreading (coupled with huge magmatic inflation) resumed, after ~1 Myr of spreading cessation. The spreading model by Nicolosi et al. (2006) has been recently questioned by Cocchi et al. (2009), who argued that filtering had created fictitious anomaly stripes. Cocchi et al. (2009) also gathered new high-resolution shipborne magnetic anomaly data from the Marsili seamount and surrounding basin area. They found two tiny positive magnetic anomaly stripes flanking the Marsili seamount in the north, which they interpreted as due to spreading occurring during the Jaramillo subchron (0.99-1.07 Ma). Consequently, they calculated a post-1.95 Ma initial spreading rate of 3.4 cm/yr (instead of 19 cm/yr), and supported a decreasing yet continuous spreading until Present. Here we discuss the whole magnetic residual evidence from the Marsili Basin. First, we show that magnetic anomaly stripes are also

  15. Linear sea-level response to abrupt ocean warming of major West Antarctic ice basin

    NASA Astrophysics Data System (ADS)

    Mengel, M.; Feldmann, J.; Levermann, A.

    2016-01-01

    Antarctica's contribution to global sea-level rise has recently been increasing. Whether its ice discharge will become unstable and decouple from anthropogenic forcing or increase linearly with the warming of the surrounding ocean is of fundamental importance. Under unabated greenhouse-gas emissions, ocean models indicate an abrupt intrusion of warm circumpolar deep water into the cavity below West Antarctica's Filchner-Ronne ice shelf within the next two centuries. The ice basin's retrograde bed slope would allow for an unstable ice-sheet retreat, but the buttressing of the large ice shelf and the narrow glacier troughs tend to inhibit such instability. It is unclear whether future ice loss will be dominated by ice instability or anthropogenic forcing. Here we show in regional and continental-scale ice-sheet simulations, which are capable of resolving unstable grounding-line retreat, that the sea-level response of the Filchner-Ronne ice basin is not dominated by ice instability and follows the strength of the forcing quasi-linearly. We find that the ice loss reduces after each pulse of projected warm water intrusion. The long-term sea-level contribution is approximately proportional to the total shelf-ice melt. Although the local instabilities might dominate the ice loss for weak oceanic warming, we find that the upper limit of ice discharge from the region is determined by the forcing and not by the marine ice-sheet instability.

  16. Trichoptera biodiversity of the Aegean and Adriatic sea basins in the republic of Kosovo.

    PubMed

    Ibrahimi, Halil; Kučinić, Mladen; Gashi, Agim; Grapci-Kotori, Linda

    2014-01-01

    We present the first preliminary inventory of Trichoptera taxa in the Aegean and Adriatic Sea basins in Kosovo that have previously received poor and fragmentary attention. Adult caddisflies were collected using ultraviolet (UV) light traps in 13 stations in areas of the Aegean Sea and Adriatic Sea drainage basins in Kosovo. Nineteen species out of 82, reported in this article, are first records for the Kosovo caddisfly fauna. Five genera are recorded for the first time in Kosovo: Brachycentrus, Ecclisopteryx, Psilopteryx, Thremma, and Oecetis. During this investigation, we found several Southeastern European endemic and rare species whose previous known distribution was limited to particular areas of this region, as well as other species whose distribution is considerably enlarged by this investigation: Polycentropus ierapetra, Polycentropus irroratus, Chaetopteryx stankovici, Drusus schmidi, Drusus tenellus, Potamophylax goulandriourum, Oecetis notata, and Notidobia melanoptera. Even though this article is a result of a limited sampling effort, it increases the number of Trichoptera taxa recorded for the Republic of Kosovo to 131.

  17. Clustering and interpretation of local earthquake tomography models in the southern Dead Sea basin

    NASA Astrophysics Data System (ADS)

    Bauer, Klaus; Braeuer, Benjamin

    2016-04-01

    The Dead Sea transform (DST) marks the boundary between the Arabian and the African plates. Ongoing left-lateral relative plate motion and strike-slip deformation started in the Early Miocene (20 MA) and produced a total shift of 107 km until presence. The Dead Sea basin (DSB) located in the central part of the DST is one of the largest pull-apart basins in the world. It was formed from step-over of different fault strands at a major segment boundary of the transform fault system. The basin development was accompanied by deposition of clastics and evaporites and subsequent salt diapirism. Ongoing deformation within the basin and activity of the boundary faults are indicated by increased seismicity. The internal architecture of the DSB and the crustal structure around the DST were subject of several large scientific projects carried out since 2000. Here we report on a local earthquake tomography study from the southern DSB. In 2006-2008, a dense seismic network consisting of 65 stations was operated for 18 months in the southern part of the DSB and surrounding regions. Altogether 530 well-constrained seismic events with 13,970 P- and 12,760 S-wave arrival times were used for a travel time inversion for Vp, Vp/Vs velocity structure and seismicity distribution. The work flow included 1D inversion, 2.5D and 3D tomography, and resolution analysis. We demonstrate a possible strategy how several tomographic models such as Vp, Vs and Vp/Vs can be integrated for a combined lithological interpretation. We analyzed the tomographic models derived by 2.5D inversion using neural network clustering techniques. The method allows us to identify major lithologies by their petrophysical signatures. Remapping the clusters into the subsurface reveals the distribution of basin sediments, prebasin sedimentary rocks, and crystalline basement. The DSB shows an asymmetric structure with thickness variation from 5 km in the west to 13 km in the east. Most importantly, a well-defined body

  18. Crustal structure of the western Yamato Basin, Japan Sea, revealed from seismic survey

    NASA Astrophysics Data System (ADS)

    No, T.; Sato, T.; Kodaira, S.; Miura, S.; Ishiyama, T.; Sato, H.

    2015-12-01

    The Yamato Basin is the second largest basin of the Japan Sea. This basin is important to clarify its formation process. Some studies of crustal structure had been carried out in the Yamato Basin (e.g. Ludwig et al., 1975; Katao, 1988; Hirata et al., 1989; Sato et al., 2006). However, the relationship between formation process and crustal structure is not very clear, because the amount of seismic exploration data is very limited. In addition, since there is ODP Leg 127 site 797 (Tamaki et al., 1990) directly beneath our seismic survey line, we contributed to the study on the formation of the Yamato Basin by examining the relation between the ODP results and our results. During July-August 2014, we conducted a multi-channel seismic (MCS) survey and ocean bottom seismometer (OBS) survey to study the crustal structure of the western Yamato Basin. We present an outline of the data acquisition and results of the data processing and preliminary interpretations from this study. As a result of our study, the crust, which is about 12 km thick, is thicker than standard oceanic crust (e.g., Spudich and Orcutt, 1980; White et al., 1992) revealed from P-wave velocity structure by OBS survey. A clear reflector estimated to be the Moho can be identified by MCS profiles. The characteristics of the sedimentary layer are common within the survey area. For example, a strong coherent reflector that is estimated to be an opal-A/opal-CT BSR (bottom simulating reflector) (Kuramoto et al., 1992) was confirmed in the sediment of all survey lines. On the other hand, a coherent reflector in the crust was confirmed in some lines. It is identified as this reflector corresponding with the deformation structure in the sediment and basement.

  19. Crustal and basin evolution of the southwestern Barents Sea: From Caledonian orogeny to continental breakup

    NASA Astrophysics Data System (ADS)

    Gernigon, L.; Brönner, M.; Roberts, D.; Olesen, O.; Nasuti, A.; Yamasaki, T.

    2014-04-01

    A new generation of aeromagnetic data documents the post-Caledonide rift evolution of the southwestern Barents Sea (SWBS) from the Norwegian mainland up to the continent-ocean transition. We propose a geological and tectonic scenario of the SWBS in which the Caledonian nappes and thrust sheets, well-constrained onshore, swing from a NE-SW trend onshore Norway to NW-SE/NNW-SSE across the SWBS platform area. On the Finnmark and Bjarmeland platforms, the dominant inherited magnetic basement pattern may also reflect the regional and post-Caledonian development of the late Paleozoic basins. Farther west, the pre-breakup rift system is characterized by the Loppa and Stappen Highs, which are interpreted as a series of rigid continental blocks (ribbons) poorly thinned as compared to the adjacent grabens and sag basins. As part of the complex western rift system, the Bjørnøya Basin is interpreted as a propagating system of highly thinned crust, which aborted in late Mesozoic time. This thick Cretaceous sag basin is underlain by a deep-seated high-density body, interpreted as exhumed high-grade metamorphic lower crust. The abortion of this propagating basin coincides with a migration and complete reorganization of the crustal extension toward a second necking zone defined at the level of the western volcanic sheared margin and proto-breakup axis. The abortion of the Bjørnøya Basin may be partly explained by its trend oblique to the regional, inherited, structural grain, revealed by the new aeromagnetic compilation, and by the onset of further weakening later sustained by the onset of magmatism to the west.

  20. Crustal and basin evolution of the southwestern Barents Sea: from the Caledonian orogeny to continental breakup

    NASA Astrophysics Data System (ADS)

    Gernigon, Laurent; Brönner, Marco; Roberts, David; Olesen, Odleiv

    2013-04-01

    A new generation of aeromagnetic data documents the post-Caledonian tectonic evolution of the southwestern Barents Sea (SBS) up to the continent-ocean transition. Clear evidence of reactivation of Caledonian structures controlling both, Late Palaeozoic and Mesozoic basins can be observed at the edge of the Hammerfest and Nordkapp basins where reactivated low-angle detachments are observed on seismics. Our new aeromagnetic surveys confirm most of the previous structural elements, but new features appear and illustrate the complexity of the pre-Permian tectonic and the basement architecture in the SBS. We propose an updated tectonic scenario of the SBS where the Caledonian nappes and thrust sheets, well constrained onshore, swing anticlockwise from a NE-SW trend close to the Varanger Peninsula to NW-SE across the Nordkapp Basin and the Bjarmeland Platform. On the Bjarmeland Platform, the dominant magnetic grain is clearly NNW-SSE. We show that this pattern reflects a regional pre-Permian system involving several Caledonian thrust sheets that possibly collapsed and controlled the post-Caledonian late Palaeozoic rift development of the SBS. We also consider that this model can explain the later development of the SBS. One specific case is the Bjørnøya Basin, located between the Loppa and Stappen highs which are interpreted as a series of rigid and poorly thinned continental blocks (ribbons) flanked by the Hammerfest and Bjørnøya basins and the basins of the Vestbakken volcanic province. As part of this extensive complex system, the Bjørnøya Basin is interpreted as a extensively thinned and propagating system that aborted in Late Mesozoic time. This thick, Cretaceous sag basin is characterised by a deep high-density body, interpreted as a combination of exhumed lower crust and/or potential serpentinised mantle as suggested by potential field modelling. The abortion of this propagating basin may be partly explained by its trend, which is oblique to the inherited

  1. Transplant experiments uncover Baltic Sea basin-specific responses in bacterioplankton community composition and metabolic activities

    PubMed Central

    Lindh, Markus V.; Figueroa, Daniela; Sjöstedt, Johanna; Baltar, Federico; Lundin, Daniel; Andersson, Agneta; Legrand, Catherine; Pinhassi, Jarone

    2015-01-01

    Anthropogenically induced changes in precipitation are projected to generate increased river runoff to semi-enclosed seas, increasing loads of terrestrial dissolved organic matter and decreasing salinity. To determine how bacterial community structure and functioning adjust to such changes, we designed microcosm transplant experiments with Baltic Proper (salinity 7.2) and Bothnian Sea (salinity 3.6) water. Baltic Proper bacteria generally reached higher abundances than Bothnian Sea bacteria in both Baltic Proper and Bothnian Sea water, indicating higher adaptability. Moreover, Baltic Proper bacteria growing in Bothnian Sea water consistently showed highest bacterial production and beta-glucosidase activity. These metabolic responses were accompanied by basin-specific changes in bacterial community structure. For example, Baltic Proper Pseudomonas and Limnobacter populations increased markedly in relative abundance in Bothnian Sea water, indicating a replacement effect. In contrast, Roseobacter and Rheinheimera populations were stable or increased in abundance when challenged by either of the waters, indicating an adjustment effect. Transplants to Bothnian Sea water triggered the initial emergence of particular Burkholderiaceae populations, and transplants to Baltic Proper water triggered Alteromonadaceae populations. Notably, in the subsequent re-transplant experiment, a priming effect resulted in further increases to dominance of these populations. Correlated changes in community composition and metabolic activity were observed only in the transplant experiment and only at relatively high phylogenetic resolution. This suggested an importance of successional progression for interpreting relationships between bacterial community composition and functioning. We infer that priming effects on bacterial community structure by natural episodic events or climate change induced forcing could translate into long-term changes in bacterial ecosystem process rates. PMID

  2. Imaging the crustal and lithospheric structures beneath the Alboran Domain and its surrounding area

    NASA Astrophysics Data System (ADS)

    Dündar, Süleyman; Kind, Rainer; Yuan, Xiaohui

    2010-05-01

    -out correction is applied prior to stacking the individual traces in order to compare and then to better identify the coherent phases. We alternatively use piercing-point approach for stacking process subdividing the region into the grids with a size of 1°x1° and stack the individual traces based on their corresponding grids (piercing-points). The S-receiver function is used to avoid complications due to the crustal-reverberations and thus to better resolve the variation of lithosphere-asthenosphere boundary (LAB). The variation of crustal thickness derived from P-wave receiver functions is well-correlated with the pattern obtained from S-wave receiver functions.The results suggest that the thickness of the crust as well as the depth of LAB systematically decreases towards the east. The greatest crustal thickness is observed along the Betic and Rift mountains. The relatively shallow Moho as well as the shallow LAB beneath the Alboran Sea are consistent with the extensional nature of the boundary between Iberian and African plates.

  3. Turonian-Santonian depositional and sea level history of the Tarfaya Atlantic coastal basin, SW Morocco

    NASA Astrophysics Data System (ADS)

    Aquit, Mohamed; Kuhnt, Wolfgang; Holbourn, Ann; Hassane Chellai, El; Lees, Jacqueline A.; Kluth, Oliver; Jabour, Haddou; Delaporte, Jean-Pierre

    2013-04-01

    The Turonian to Santonian organic-rich successions deposited in the continuously subsiding Tarfaya Atlantic coastal basin (SW Morocco) allow detailed reconstruction of depositional environments and correlation to eustatic sea level changes. We present high-resolution X-ray fluorescence (XRF) scanning and natural gamma-ray (NGR) records from a newly drilled sedimentary core Tarfaya SN°2 (27° 57´ 43.1´´N, 12° 48´ 37.0´´W), which recovered a continuous sedimentary succession from a middle to outer shelf environment. In the latest Turonian, the late Coniacian, and the middle and latest Santonian, high NGR and Al with low Mn and Ca content indicate pronounced dysoxic horizons that reflect impingement of the oxygen minimum zone on the shelf during sea level highstands. In contrast, lower NGR and Al with higher Mn and Ca values indicate high detrital carbonate content and more oxic conditions related to regressive events in the late Turonian, early to middle Conacian and early Santonian. Exceptionally high sedimentation rates (>10cm/kyr) characterize the late Turonian, and spectral analyses of XRF and NGR data reveal that sedimentation was mostly controlled by obliquity and precession, suggesting an overriding glacioeustatic control. However, the response to orbital forcing weakened during the latest Turonian, when sedimentation rates declined markedly to ~2 cm/kyr. We will extend this study to three newly drilled cores nearby that recovered sediment sequences from the late Albian to late Turonian and from the late Santonian to Campanian in order to retrace the complete Late Cretaceous depositional history of the Tarfaya Basin and to develop a high-resolution carbon isotope stratigraphy allowing correlation to records from other continental margins. Key words: Late Cretaceous, Tarfaya Basin, XRF scanning, natural gamma-ray, oxygen minimum zone, sea level, orbital forcing.

  4. Seismic Stratigraphy of the Central South China Sea Basin and Implications for Neotectonics

    NASA Astrophysics Data System (ADS)

    Li, C. F.; Ding, W.; Franke, D.; Yao, Y.; Pang, X.; Shi, H.; Li, J.; Cao, Y.

    2014-12-01

    International Ocean Discovery Program (IODP) Expedition 349 drilled five sites in the central South China Sea Basin. Three sites (U1431 in the East Subbasin, and U1433 and U1434 in the Southwest Subbasin) reached basalt interpreted to be igneous basement of the oceanic crust. Site U1435 on the northern continent-ocean boundary recovered pre-Oligocene sedimentary rocks deposited prior to the opening of the South China Sea. Furthermore, a full suite of geophysical logging was also carried out at Sites U1431 and U1433. These coring and logging data and physical property measurements are integrated with, and correlated to, regional reflection seismic data to map regional sequence stratigraphic boundaries and seismic facies of the central basin and the continent-ocean transition zone. With our carefully selected seismic profiles, stratigraphic correlation is possible even between the continent-ocean transition zone and the central basin, circumventing preexisting basement highs near the continent-ocean boundary that often prevent direct correlation. We interpret four sequence boundaries, which are Oligocene/Miocene, middle Miocene/late Miocene, Miocene/Pliocene, and Pliocene/Pleistocene boundaries. Seismic facies between sequence boundaries are often characteristic and distinctive, allowing relatively straightforward regional correlation. For example, massive Miocene carbonate deposits, if well consolidated, are readily distinguishable by strong seismic reflectivities, caused by their relatively higher density and velocity in contrast to those of interbedded turbidite clastic sediments. However, we found abrupt seismic facies changes both temporally and spatially. In particular, the fossil spreading ridge and the Zhongnan ridge between the East and Southwest Subbasins acted as major sedimentary barriers, across which seismic facies changes sharply and cannot be easily correlated. The well-constrained seismic sequence boundaries also allow us to estimate the timing of

  5. Microbial Sulfide Filter along a Benthic Redox Gradient in the Eastern Gotland Basin, Baltic Sea

    PubMed Central

    Yücel, Mustafa; Sommer, Stefan; Dale, Andrew W.; Pfannkuche, Olaf

    2017-01-01

    The sediment-water interface is an important site for material exchange in marine systems and harbor unique microbial habitats. The flux of nutrients, metals, and greenhouse gases at this interface may be severely dampened by the activity of microorganisms and abiotic redox processes, leading to the “benthic filter” concept. In this study, we investigate the spatial variability, mechanisms and quantitative importance of a microbially-dominated benthic filter for dissolved sulfide in the Eastern Gotland Basin (Baltic Sea) that is located along a dynamic redox gradient between 65 and 173 m water depth. In August-September 2013, high resolution (0.25 mm minimum) vertical microprofiles of redox-sensitive species were measured in surface sediments with solid-state gold-amalgam voltammetric microelectrodes. The highest sulfide consumption (2.73–3.38 mmol m−2 day−1) occurred within the top 5 mm in sediments beneath a pelagic hypoxic transition zone (HTZ, 80–120 m water depth) covered by conspicuous white bacterial mats of genus Beggiatoa. A distinct voltammetric signal for polysulfides, a transient sulfur oxidation intermediate, was consistently observed within the mats. In sediments under anoxic waters (>140 m depth), signals for Fe(II) and aqueous FeS appeared below a subsurface maximum in dissolved sulfide, indicating a Fe(II) flux originating from older sediments presumably deposited during the freshwater Ancylus Lake that preceded the modern Baltic Sea. Our results point to a dynamic benthic sulfur cycling in Gotland Basin where benthic sulfide accumulation is moderated by microbial sulfide oxidation at the sediment surface and FeS precipitation in deeper sediment layers. Upscaling our fluxes to the Baltic Proper; we find that up to 70% of the sulfide flux (2281 kton yr−1) toward the sediment-seawater interface in the entire basin can be consumed at the microbial mats under the HTZ (80–120 m water depth) while only about 30% the sulfide flux effuses

  6. A physical view of La Guajira Upwelling System, Colombian Basin, Caribbean Sea

    NASA Astrophysics Data System (ADS)

    Bernal, G.; Beier, E.; Barton, E. D.; Ruiz-Ochoa, M.; Correa, J. G.

    2013-05-01

    La Guajira Peninsula lies within a large upwelling system along the South Caribbean Coast, created by the NE trade winds. In this location, sea surface temperature (SST) exhibits the lowest mean value and the highest variability in the whole Colombian Basin. The seasonal variation of SST explains up to 75 % of the total variability. La Guajira coastal zone also experiences the highest values of wind stress and wind stress curl, with the greatest annual and semiannual variability in the Colombian Basin. It has been shown that wind stress curl enhances the upwelling over the region. Near 90% of the variability of SST in La Guajira can be explained by the seasonality plus the first three EOFs interannual modes: the first, synchronous throughout the Basin, is dominant, and consists of a uniform interannual variation in phase with the North Tropical Atlantic Index; the second co-varies strongly with the second mode of wind stress curl; and the third reflects the role of the vertical atmospheric circulation cell associated with the Caribbean Low Level Jet off Central America. The inclusion of wind stress curl with its maximum offshore of La Guajira explains in part the extension of cool coastal water into the Colombian Basin, with advection in filaments, eddies and meanders. In order to complement the physical knowledge of La Guajira upwelling system, an analysis of water masses, sea surface height, Ekman suction, Ekman transport and coastal upwelling index (CUI) was performed. Hydrographic data was obtained from gridded climatologies from the National Oceanographic Data Center (WOD01); sea surface height anomalies from the Archiving, Validation, and Interpretation of Satellite Oceanography (AVISO) data; and wind data from the Cross-Calibrated Multi-Platform Ocean Surface Wind Velocity Product for Meteorological and Oceanographic Applications (CCMP). The upwelling forms a local water mass, La Guajira surface water (LGSW), with the mixing of subtropical underwater and

  7. Unusual dominance by desert pupfish (Cyprinodon macularius) in experimental ponds within the Salton Sea Basin

    USGS Publications Warehouse

    Saiki, Michael K.; Martin, Barbara A.; Anderson, Thomas W.

    2011-01-01

    In October 2006, months after shallow experimental ponds in the Salton Sea Basin were filled with water from the Alamo River and Salton Sea, fish were observed in several ponds, although inlets had been screened to exclude fish. During October 2007November 2009, nine surveys were conducted using baited minnow traps to document species and relative abundance of fish. Surveys yielded 3,620 fish representing five species. Desert pupfish (Cyprinodon macularius), the only native species encountered, was the most numerous and comprised >93% of the catch. Nonnative species included western mosquitofish (Gambusia affinis, 4.1%), sailfin molly (Poecilia latipinna, 2.8%), and tilapia (a mixture of hybrid Mozambique tilapia Oreochromis mossambicus ?? O. urolepis and redbelly tilapia Tilapia zillii, <0.1%). Dominance by desert pupfish, which persisted over our 2 years of study, was unusual because surveys conducted in nearby agricultural drains yielded relatively few desert pupfish.

  8. The last interglacial-glacial transition as recorded in sediments from the deep Dead Sea basin

    NASA Astrophysics Data System (ADS)

    Neugebauer, I.; Brauer, A.; Schwab, M. J.; Waldmann, N.; Hadzhiivanova, E.; Frank, U.; Dulski, P.

    2013-12-01

    The Dead Sea and its Pleistocene precursors act as amplifier lakes of climate change affecting the eastern Mediterranean region. The ~460 m long sediment core 5017-1, retrieved from the deepest part of the lake, ideally mirrors the climate variability of the last approximately 200-250 ka. In the current study, we focus on the upper part of the last interglacial Samra Formation (~135-70 ka BP; Waldmann et al., 2009) and the transition into the last glacial Lisan Formation (~70-14ka BP; e.g. Bartov et al., 2002). Overlying the ca 45 m thick main salt layered sequence deposited during the last interglacial, the analyzed ca 30 m thick interval in core 5017-1 is characterized by a lower ~20 m thick interval of predominant alternating aragonite and detrital marl (aad) with occasional intercalations of mass movement deposits, accumulated during temporary humid climatic conditions. The entire sequence is topped by an upper ~10 m thick interval of predominantly layered massive halite, reflecting a dryer climate. Micro-facies analysis on large-scale petrographic thin sections, XRF element scanning, grain size and magnetic susceptibility measurements have been carried out on this interval for detailed and high-resolution characterization of the sediments and interpretation in terms of depositional processes and their value as paleoclimate proxies. The finding of a most likely millennial-scale dry interval just before the beginning of the stratigraphically defined humid Lisan interval falls in agreement with a previously identified depositional hiatus and associated erosional unconformity in the shallower areas outcropping at the margins of the lake (Stein, 2001). However, the deposition of glacial-like aad sediments prior to this pronounced dry period stands in contrast to previous analyses on outcrops (Waldmann et al. 2009). Investigating sediments from the deep Dead Sea basin will hence allow understanding and better deciphering the depositional processes in relation with

  9. Tectonics of East Siberian Sea Basin and its influence on petroleum systems

    NASA Astrophysics Data System (ADS)

    Karpov, Yury; Antonina, Stoupakova; Anna, Suslova; Mariia, Agasheva

    2016-04-01

    The East Siberian Sea basin (ESSB) is the largest part of the Siberian Arctic shelf, extending for over 1000 km from New Siberian Islands archipelago to Wrangel Island. Nowadays East Siberian Sea margin is considered as a region with probable high petroleum potential. This part of Russian Arctic shelf is the least studied. The major problems in geological investigation of East Siberian Sea shelf are absence of deep wells in area and low seismic exploration maturity. Only general conclusions on its geology and hydrocarbon systems can be drawn based on limited seismic, gravity and magnetic data, supported by projection of onshore geological data to offshore. So, that's why now only complex geological and seismic stratigraphy interpretations are provided. Today we have several concepts and can summarize the tectonic history of the basin. The basin is filled with siliclastic sediments. In the deepest depocentres sediments thickness exceed 8 km in average. Seismic data was interpreted using methods of seismic stratigraphy. Stratigraphic interpretation was possible to achieve because seismic reflections follow chronostratigraphic correlations. Finally, main seismic horizons were indicated. Each indicated horizon follows regional stratigraphic unconformity. In case of absence of deep wells in ESSB, we can only prove possible source rocks by projection of data about New Siberian Islands archipelago source rocks on offshore. The petroleum potential of these rocks was investigated by several authors [1, 2, 3]. Perspective structures, investigated in ESSB were founded out by comparing seismogeological cross-sections with explored analogs in other Russian and foreign onshore and offshore basins. The majority of structures could be connected with stratigraphic and fault traps. New data on possible petroleum plays was analyzed, large massif of data on geology and tectonic history of the region was collected, so now we can use method of basin modelling to evaluate hydrocarbon

  10. Distribution of polybrominated diphenyl ethers and decabromodiphenylethane in surface sediments from the Bering Sea, Chukchi Sea, and Canada Basin

    NASA Astrophysics Data System (ADS)

    Cai, M. G.; Hong, Q. Q.; Wang, Y.; Luo, X. J.; Chen, S. J.; Cai, M. H.; Qiu, C. R.; Huang, S. Y.; Mai, B. X.

    2012-12-01

    24 surface sediment samples were collected from the Bering Sea, Chukchi Sea, and Canada Basin during the 3rd Chinese National Arctic Research Expedition in July-September 2008. To obtain information on the levels, spatial distribution, possible sources, and influences of total carbon and black carbon, we analyzed the samples for polybrominated diphenyl ethers (PBDEs) and decabromodiphenylethane (DBDPE). Concentrations of ∑PBDEs (hereafter, ∑PBDEs refers to the sum of all detected PBDE congeners without BDE-209), BDE-209, and DBDPE were in the ranges 3.58-148.95 pg/g d.w. (dry weight), n.d. -804.91 pg/g d.w. and n.d. -452.57 pg/g d.w., respectively. The congener patterns of PBDEs suggested that BDE-209 was the major congener in these areas, followed by BDE-99 and -47, which was consistent with the predominance of technical deca-BDE mixtures in the dominant technical PBDE mixtures. The significant relationships of BDE-209, -47, and -99 and total PBDEs with total organic carbon and black carbon, as well as the skewed distribution of ∑PBDEs and BDE-209, indicated that atmospheric deposition and local discharge might be potential sources in this area, and the distribution pattern may be the combined effect of multiple factors.

  11. Amazon Basin climate under global warming: the role of the sea surface temperature.

    PubMed

    Harris, Phil P; Huntingford, Chris; Cox, Peter M

    2008-05-27

    The Hadley Centre coupled climate-carbon cycle model (HadCM3LC) predicts loss of the Amazon rainforest in response to future anthropogenic greenhouse gas emissions. In this study, the atmospheric component of HadCM3LC is used to assess the role of simulated changes in mid-twenty-first century sea surface temperature (SST) in Amazon Basin climate change. When the full HadCM3LC SST anomalies (SSTAs) are used, the atmosphere model reproduces the Amazon Basin climate change exhibited by HadCM3LC, including much of the reduction in Amazon Basin rainfall. This rainfall change is shown to be the combined effect of SSTAs in both the tropical Atlantic and the Pacific, with roughly equal contributions from each basin. The greatest rainfall reduction occurs from May to October, outside of the mature South American monsoon (SAM) season. This dry season response is the combined effect of a more rapid warming of the tropical North Atlantic relative to the south, and warm SSTAs in the tropical east Pacific. Conversely, a weak enhancement of mature SAM season rainfall in response to Atlantic SST change is suppressed by the atmospheric response to Pacific SST. This net wet season response is sufficient to prevent dry season soil moisture deficits from being recharged through the SAM season, leading to a perennial soil moisture reduction and an associated 30% reduction in annual Amazon Basin net primary productivity (NPP). A further 23% NPP reduction occurs in response to a 3.5 degrees C warmer air temperature associated with a global mean SST warming.

  12. Salt distribution in the Norwegian-Danish Basin, Central North Sea

    NASA Astrophysics Data System (ADS)

    Sassier, Caroline; Jarsve, Erlend; Heeremans, Michel; Mansour Abdelmalak, Mohamed; Faleide, Jan Inge; Helge Gabrielsen, Roy

    2014-05-01

    Salt tectonics have extensively been studied in most parts of the Central North Sea. However, few studies have been done in the Norwegian side of the Norwegian-Danish Basin. In this contribution, we report a new regional analysis of the salt patterns across the offshore Norwegian-Danish Basin. We have mapped the regional distribution of salt structures in the Norwegian-Danish Basin using both old and recent 2D seismic reflection profiles tied to wells. The salt-thickness map shows three distinct salt structures patterns: (1) NW-SE trending salt walls in the northern part of the basin; the spacing between the walls vary between 7 to 12 km; (2) a dense and irregular distribution of salt diapirs in the southern part of the studied area; (3) an irregular pattern of sparse but big salt diapirs in the eastern part of the basin. This domain is characterized by numerous turtle structures associated with salt diapirs. Reflection seismic cross-sections show that most salt structures only pierce the Triassic sedimentary strata whereas only few salt structures reach the seabed. Rotated fault blocks indicate a gliding vergence towards the South in the eastern part of the basin and towards the SE in the western side of the Norwegian-Danish Basin. No mature or compressive salt structures, except some squeezed salt diapirs, are observed in the topographic lows of the basin. The initiation of salt tectonics started during the early Middle Triassic in the entire basin; salt tectonics reactivations were recorded during the Middle Jurassic, Paleogene, and prior to the Quaternary but are not homogeneous across the basin. Salt movements inferred from our study are in good agreement with previous studies. The trend of salt walls (domain 1) indicates a NE-SW extension which is not compatible with N-S trending pre-salt faults. Instead, the strong Triassic subsidence towards the SW has most likely controlled the formation of the salt walls. The salt was initially thicker in domain 2 that

  13. Structures of the northeasternmost South China Sea continental margin and ocean basin: geophysical constraints and tectonic implications

    NASA Astrophysics Data System (ADS)

    Li, Chun-Feng; Zhou, Zuyi; Li, Jiabiao; Hao, Hujun; Geng, Jianhua

    2007-03-01

    The northeastern part of the South China Sea is a special region in many aspects of its tectonics. Both recent drilling into the Mesozoic and new reflection seismic surveys in the area provide a huge amount of data, fostering new understanding of the continental margin basins and regional tectonic evolution. At least four half-grabens are developed within the Northern Depression of the Tainan Basin, and all are bounded on their southern edges by northwestward-dipping faults. One of the largest half-grabens is located immediately to the north of the Central Uplift and shows episodic uplift from the late Oligocene to late Miocene. Also during that period, the Central Uplift served in part as a material source to the Southern Depression of the Tainan Basin. The Southern Depression of the Tainan Basin is a trough structure with deep basement (up to 9 km below sealevel or 6 km beneath the sea bottom) and thick Cenozoic sedimentation (>6 km thick). Beneath the Southern Depression we identified a strong landward dipping reflector within the crustal layer that represents a significant crustal fault. This reflector coincides with a sharp boundary in crustal thicknesses and Moho depths. We show that the northeasternmost South China Sea basin, which may have undergone unique evolution since the late Mesozoic, is markedly different from the central South China Sea basin and the Huatung Basin, both geologically and geophysically. The Cenozoic evolution of the region was largely influenced by pre-existing weaknesses due to tectonic inheritance and transition. The South China Sea experienced multiple stages of Cenozoic extension.

  14. Mapping of the air-sea CO2 flux in the Arctic Ocean and its adjacent seas: Basin-wide distribution and seasonal to interannual variability

    NASA Astrophysics Data System (ADS)

    Yasunaka, Sayaka; Murata, Akihiko; Watanabe, Eiji; Chierici, Melissa; Fransson, Agneta; van Heuven, Steven; Hoppema, Mario; Ishii, Masao; Johannessen, Truls; Kosugi, Naohiro; Lauvset, Siv K.; Mathis, Jeremy T.; Nishino, Shigeto; Omar, Abdirahman M.; Olsen, Are; Sasano, Daisuke; Takahashi, Taro; Wanninkhof, Rik

    2016-09-01

    We produced 204 monthly maps of the air-sea CO2 flux in the Arctic north of 60°N, including the Arctic Ocean and its adjacent seas, from January 1997 to December 2013 by using a self-organizing map technique. The partial pressure of CO2 (pCO2) in surface water data were obtained by shipboard underway measurements or calculated from alkalinity and total inorganic carbon of surface water samples. Subsequently, we investigated the basin-wide distribution and seasonal to interannual variability of the CO2 fluxes. The 17-year annual mean CO2 flux shows that all areas of the Arctic Ocean and its adjacent seas were net CO2 sinks. The estimated annual CO2 uptake by the Arctic Ocean was 180 TgC yr-1. The CO2 influx was strongest in winter in the Greenland/Norwegian Seas (>15 mmol m-2 day-1) and the Barents Sea (>12 mmol m-2 day-1) because of strong winds, and strongest in summer in the Chukchi Sea (∼10 mmol m-2 day-1) because of the sea-ice retreat. In recent years, the CO2 uptake has increased in the Greenland/Norwegian Sea and decreased in the southern Barents Sea, owing to increased and decreased air-sea pCO2 differences, respectively.

  15. Quaternary active tectonic structures in the offshore Bajo Segura basin (SE Iberian Peninsula - Mediterranean Sea)

    NASA Astrophysics Data System (ADS)

    Perea, H.; Gràcia, E.; Alfaro, P.; Bartolomé, R.; Lo Iacono, C.; Moreno, X.; Masana, E.; Event-Shelf Team

    2012-10-01

    The Bajo Segura fault zone (BSFZ) is the northern terminal splay of the Eastern Betic shear zone (EBSZ), a large left-lateral strike-slip fault system of sigmoid geometry stretching more than 450 km from Alicante to Almería. The BSFZ extends from the onshore Bajo Segura basin further into the Mediterranean Sea and shows a moderate instrumental seismic activity characterized by small earthquakes. Nevertheless, the zone was affected by large historical earthquakes of which the largest was the 1829 Torrevieja earthquake (IEMS98 X). The onshore area of the BSFZ is marked by active transpressive structures (faults and folds), whereas the offshore area has been scarcely explored from the tectonic point of view. During the EVENT-SHELF cruise, a total of 10 high-resolution single-channel seismic sparker profiles were obtained along and across the offshore Bajo Segura basin. Analysis of these profiles resulted in (a) the identification of 6 Quaternary seismo-stratigraphic units bounded by five horizons corresponding to regional erosional surfaces related to global sea level lowstands; and (b) the mapping of the active sub-seafloor structures and their correlation with those described onshore. Moreover, the results suggest that the Bajo Segura blind thrust fault or the Torrevieja left-lateral strike-slip fault, with prolongation offshore, could be considered as the source of the 1829 Torrevieja earthquake. These data improve our understanding of present deformation along the BSFZ and provide new insights into the seismic hazard in the area.

  16. Occurrence and seismic characteristics of stacked Quaternary debris-flow deposits in the Ulleung Basin, East Sea

    NASA Astrophysics Data System (ADS)

    Yoo, Dong-Geun; Lee, Young-Mi; Kang, Nyeon-Keon; Yi, Bo-Yeon; Bahk, Jang-Jun; Kim, Gil-Young

    2015-04-01

    Analysis of multi-channel seismic reflection profiles collected from the Ulleung Basin, East Sea reveals that the Quaternary sequence in this area includes eighteen stacked debris flow deposits, which are variable in the geometry and spatial distribution. Each deposit is acoustically characterized by chaotic or transparent seismic facies without distinct internal reflections and shows wedge or lens-shaped external form. Based on distribution patterns, these deposits which form a succession of vertically and/or laterally stacked wedges are widely distributed on the southern slope and cover an area of more than 8,000 km2. Their general flow direction is from south to north and the thickness gradually decreases toward the basin plain. The results of seismic interpretation suggest that sedimentation during the Quaternary was controlled mainly by tectonic effects associated with sea-level fluctuations. The back-arc closure of the East Sea that began in the Miocene caused compressional deformation along the southern margin of the Ulleung Basin, resulting in regional uplift which continued until the Pliocene. Large amounts of sediments, eroded from the uplifted blocks, were supplied to the basin through the mass transport processes, leading to the formation of stacked debris-flow deposits. Consequently, the development of debris flow deposits in the Ulleung Basin is largely controlled by regional tectonic event associated with the back-arc closure of the East Sea.

  17. Assessment of circulation and inter-basin transport in the Salish Sea including Johnstone Strait and Discovery Islands pathways

    NASA Astrophysics Data System (ADS)

    Khangaonkar, Tarang; Long, Wen; Xu, Wenwei

    2017-01-01

    The Salish Sea consisting of Puget Sound and Georgia Basin in U.S and Canadian waters has been the subject of several independent data collection and modeling studies. However, these interconnected basins and their hydrodynamic interactions have not received attention as a contiguous unit. The Strait of Juan de Fuca is the primary pathway through which Pacific Ocean water enters the Salish Sea but the role played by Johnstone Strait and the complex channels northeast of Vancouver Island, connecting the Salish Sea and the Pacific Ocean, on overall Salish Sea circulation has not been characterized. In this paper we present a modeling-based assessment of the two-layer circulation and transport through the multiple interconnected sub-basins within the Salish Sea including the effect of exchange via Johnstone Strait and Discovery Islands. The Salish Sea Model previously developed using the finite volume community ocean model (FVCOM) was expanded over the continental shelf for this assessment encircling Vancouver Island, including Discovery Islands, Johnstone Strait, Broughton Archipelago and the associated waterways. A computational technique was developed to allow summation of volume fluxes across arbitrary transects through unstructured finite volume cells. Tidally averaged volume fluxes were computed at multiple transects. The results were used to validate the classic model of Circulation in Embracing Sills for Puget Sound and to provide quantitative estimates of the lateral distribution of tidally averaged transport through the system. Sensitivity tests with and without exchanges through Johnstone Strait demonstrate that it is a pathway for Georgia Basin runoff and Fraser River water to exit the Salish Sea and for Pacific Ocean inflow. However the relative impact of this exchange on circulation and flushing in Puget Sound Basin is small.

  18. Are the Basins of Tui Regio and Hotei Arcus Sites of Former Titanian Seas?

    NASA Technical Reports Server (NTRS)

    Moore, Jeffrey Morgan; Howard, Alan

    2012-01-01

    Features observed in the basins of Tui Regio and Hotei Arcus on Titan have attracted the attention of the Cassini-era investigators. At both locations, VIMS observed discrete 5-micron bright approx.500-km wide features described as lobate in shape. Several studies have proposed that these materials are cryo-volcanic flows; in the case of the Hotei Arcus feature this inference was buttressed with SAR RADAR images showing bright and dark patches with lobate margins. We propose an alternative explanation. First we note that all landforms on Titan that are unambiguously identifiable can be explained by exogenic processes (aeolian, fluvial, impact cratering, and mass wasting). Suggestions of endogenically produced cryovolcanic constructs and flows have, without exception, lacked conclusive diagnostic evidence. Recently published topographic profiles across Tui Regio and the lobate feature region north of Hotei Arcus indicate these features appear to occur in large regional basins, at least along the direction of the profiles. SAR images show that the terrains surrounding both 5-micron bright features exhibit fluvial networks that appear to converge and debauch into the probable basins. The 5-micron bright features themselves correspond to fields of discrete radar-bright depressions whose bounding edges are commonly rounded and cumulate in planform in SAR images. These fields of discrete radar-bright depressions strongly resemble fields of features seen at Titan s high latitudes usually attributed to be dry lakes. Thus the combination of (1) the resemblance to high-latitude dry lakes, (2) location in the centers of probable regional depressions, and (3) convergence of fluvial networks are inferred by us to best explain the 5-micron bright regions at Tui Regio and Hotei Arcus as sites of dry seas or at least paleolake clusters. Such equatorial seas, if real, may be evidence of substantially larger inventories of liquid alkanes in Titan s past.

  19. The Southern Adriatic Basin: A Key Area For The Climatic Monitoring of The Mediterranean Sea

    NASA Astrophysics Data System (ADS)

    Civitarese, G.; Gacic, M.; Saint, The

    The Southern Adriatic, the southernmost and deepest subbasin of the Adriatic Sea, is considered a major site of deep water formation and the origin of the semi-closed ther- mohaline cell in the Eastern Mediterranean. The dynamics of the area is dominated by the presence of a quasi-permanent cyclonic gyre that intensifies in the winter season creating the conditions for the production of dense and oxygenated waters that are exported to the rest of the Eastern Mediterranean through the Strait of Otranto. The at- mospheric forcing is transferred into the marine system by the winter convective water overturning, that is the key process generating new waters and triggering the biologi- cal pump. The other main forcing is the intermediate saline water advection across the Strait of Otranto, connecting the Adriatic Sea with the general basin-scale circulation of the Eastern Mediterranean. Both of them act in determining the occurrence and the magnitude of the convective events and the related biological processes. Due to the ac- tion of these forcing, the Southern Adriatic system is subject to a significant variability on temporal scale spanning from days to decades. Recent studies have demonstrated that the local thermal and haline surface forcing generates strong year-to-year varia- tions of the vertical convection and consequently of the primary production. On the other hand, the advective forcing changes the intermediate water thermohaline prop- erties as well as the nutrient content in the basin, again affecting both the vertical convection and the biological processes. The signals associated to these processes are particularly intense, and allow us to designate this relatively small basin as a suit- able field laboratory for the study of the relationships between ocean biogeochemical cycles and climate.

  20. Modelling the impacts of sea level rise on tidal basin ecomorphodynamics and mangrove habitat evolution

    NASA Astrophysics Data System (ADS)

    van Maanen, Barend; Coco, Giovanni; Bryan, Karin

    2016-04-01

    The evolution of tidal basins and estuaries in tropical and subtropical regions is often influenced by the presence of mangrove forests. These forests are amongst the most productive environments in the world and provide important ecosystem services. However, these intertidal habitats are also extremely vulnerable and are threatened by climate change impacts such as sea level rise. It is therefore of key importance to improve our understanding of how tidal systems occupied by mangrove vegetation respond to rising water levels. An ecomorphodynamic model was developed that simulates morphological change and mangrove forest evolution as a result of mutual feedbacks between physical and biological processes. The model accounts for the effects of mangrove trees on tidal flow patterns and sediment dynamics. Mangrove growth is in turn controlled by hydrodynamic conditions. Under stable water levels, model results indicate that mangrove trees enhance the initiation and branching of tidal channels, partly because the extra flow resistance in mangrove forests favours flow concentration, and thus sediment erosion in between vegetated areas. The landward expansion of the channels, on the other hand, is reduced. Model simulations including sea level rise suggest that mangroves can potentially enhance the ability of the soil surface to maintain an elevation within the upper portion of the intertidal zone. While the sea level is rising, mangroves are migrating landward and the channel network tends to expand landward too. The presence of mangrove trees, however, was found to hinder both the branching and headward erosion of the landward expanding channels. Simulations are performed according to different sea level rise scenarios and with different tidal range conditions to assess which tidal environments are most vulnerable. Changes in the properties of the tidal channel networks are being examined as well. Overall, model results highlight the role of mangroves in driving the

  1. The oscillatory nature of the flows in the system of straits and small semienclosed basins of the Baltic Sea

    NASA Astrophysics Data System (ADS)

    Otsmann, Mikk; Suursaar, Ülo; Kullas, Tiit

    2001-10-01

    The Gulf of Riga and the Väinameri are small semi-enclosed sub-basins connected to each other and to the open Baltic Sea by straits. Hydrographical features and configuration of the study area give an opportunity to build a forced oscillation model and to describe the system as a combination of five simple Helmholtz oscillators, each composed of a basin and a strait. The response to the wind stress and the open sea level is modelled using motion equations with a quadratic bottom friction for the narrow channel (Coriolis' effect is neglected). The flows in the straits and the sea levels within the sub-basins are calculated. The model was calibrated and verified against field measurements with a total duration of 6 months. The model behaviour has been analysed in both stationary and nonstationary conditions, and in both idealistic and realistic forcings. Using HIRLAM winds and open sea level data as input, the oscillations of currents in all the straits were calculated for 1995. It appeared that the system could be looked upon as a superposition of two Helmholtz oscillators with resonance periods of about 24 and 13 h. 24 h is the only resonance period for the flows in the Irbe Strait and for the sea level of the Gulf of Riga basin, the Suur, Hari and Soela straits have two roughly equal maxima at 24 and 13 h while the sea level in the Väinameri basin has the primary maximum at 13 h and the secondary one at 24 h. These oscillations appear as a response of the system both to rapid changes in the wind conditions and to the sea-level changes in the boundaries of the study area. The role of the tides is relatively small. The most effective forcing function for the system is the wind stress above the straits, having a considerable role in motions with time scale between 1 yr and 1-2 d. The seasonally pulsating component in the water exchange processes has major ecological consequences for the study area. This seasonality is governed by seasonal changes in the large

  2. Integrating river basin management and the coastal zone: the (blue) Danube and the (black) sea.

    PubMed

    Maksimović, C; Makropoulos, C K

    2002-01-01

    In order to effectively manage the wide variety of physical, chemical biological and ecological processes in a sensitive coastal environment such as the Black Sea, current environmental management objectives are no longer sufficient: a new management approach has to address the intimate functional linkage between the river basin and the costal environment. Current water quality legislation requires compliance to emission levels based on the chemical analysis of water samples taken at discharge points, such as treatment plants discharging into rivers. While such measures provide a relative indication of the water quality at the point of discharge, they fail to describe accurately and sufficiently the quality of the water received from the watershed or basin. As water flows through the catchment, rainfall run-off from urban and agricultural areas carries sediments, pesticides, and other chemicals into river systems, which lead to coastal waters. The impact of the Kosovo crisis on the Danube ecosystems provides a poignant example of the effects of such diffused pollution mechanisms and reveals a number of interesting pollution mechanisms. This paper discusses both the effects of diffused pollution on the Black Sea, drawing from state-of-the-art reports on the Danube, and proposes a framework for a decision support system based on distributed hydrological and pollution transport simulation models and GIS. The use of ecological health indicators and fuzzy inference supporting decisions on regional planning within this framework is also advocated. It is also argued that even the recently produced GEF document on Black Sea protection scenarios should benefit significantly if the concept of pollution reduction from both urban, industrial and rural areas should undergo a systematic conceptual update in the view of the recent recommendations of the UNEP IETC (2000) document.

  3. Geological evolution of the West Luzon Basin (South China Sea, Philippines)

    NASA Astrophysics Data System (ADS)

    Arfai, J.; Franke, D.; Gaedicke, C.; Lutz, R.; Schnabel, M.; Ramos, E. G.

    2010-05-01

    Interpretation of new multichannel seismic data sheds insights into the geologic evolution of the West Luzon Basin (WLB), Philippines. The basin stretches for about 200 km in north-south direction and for up to 50 km in east-west direction. The West Luzon Basin is a sediment-filled trough that is located between the island of Luzon and the outer arc high of the eastward directed subduction of the South China Sea oceanic crust at the Manila Trench. However, at the southern end of the Manila Trench, where its trend changes from N-S to NW-SE and projects towards Mindoro, continental collision occurs (e.g. Lewis & Hayes, 1985). In 2008 approximately 1000 line-kilometres of regional multichannel seismic (MCS) data were obtained in the area of the WLB during a cruise with the German research vessel SONNE. In our MCS data six major unconformities in the WLB separate major stratigraphic units. We interpret high-amplitude, low-frequency reflection bands as acoustic basement that is dissected by normal faults. In the deep parts (4.5-5 s; TWT) of our E-W running seismic profiles we can trace a major fault system with a fault offset of 1-1.5 s (TWT). We suggest an initial development of the structure as a normal fault system, which later was inverted locally. A major change in the depositional regime occurs in the lower part of the sedimentary infill. A distinct bottom simulating reflector (BSR) is commonly observed. Grid calculations of the sediment thickness of the lower stratigraphic units give detailed values of deposition shifts and reveal variations in subsidence of the basin. Based on the depth of bottom simulating reflectors (BSR) heat flow values of 35-40 mW/m2 were calculated, which are typical for forearc basins. Two peculiarities of the WLB are not well in accordance with a forearc setting: The acoustic basement was affected by extensional deformation resulting in normal faulting with fault offsets up to 400 ms (TWT) but extension did not affect sedimentary layers

  4. Identity of Squalius (Actinopterygii, Cyprinidae) from Istra Peninsula in Croatia (Adriatic Sea basin).

    PubMed

    Zupancic, Primoz; Mrakovcic, Milorad; Marcic, Zoran; Naseka, Alexander M; Bogutskaya, Nina G

    2010-08-27

    A chub of previously ambiguous identity from the Boljunscica and Pazincica rivers (south-eastern Istra Peninsula) was studied and compared with geographically close Squalius squalus, Squalius zrmanja, and Squalius janae recently described from the Dragonja River drainage in the Adriatic Sea basin in Slovenia. It was shown that the chub from the south-eastern Istra Peninsula differs from all know species of Squalius but one: Squalius janae. Three samples examined from Boljunscica and Pazincica rivers and Squalius janae from its type locality, Dragonja River, show the following characters typical for the latter species: a long head (the head length 27-32% SL); a pointed conical snout with a clearly projecting upper jaw; a long straight mouth cleft, the lower jaw length (39-45% HL) exceeding the caudal peduncle depth; a large eye; commonly 9? branched anal-fin rays; commonly 44 total vertebrae (24+20 or 25+19); bright silvery colouration, scales easily lost; iris, pectoral, pelvic and anal fin pigmentation with yellow shades. The data on the distribution of Squalius chubs in the northern Adriatic basin support the assumption that the range of Squalius janae is determined by the geology of the Trieste Flysch Basin and the Pazin Flysch Basin forming the base of the Istra Peninsula. The distribution pattern of this species does not support a simple model of fish dispersal and a complete connectivity within the whole Palaeo-Po historical drainage. Indeed, it indicates a disrupted surface palaeohydrography that was heavily fragmented by karstification in the whole Dinaric area.

  5. Climatic change of sea ice mean thickness in the Arctic basin

    SciTech Connect

    Nagurny, A.P.

    1996-12-31

    A method for automatically monitoring sea ice thickness by measuring ice-plate vibration is proposed. Two energy maximums are clearly manifested in the spectrum of ice cover vibrations, corresponding to the resonant waves (the equality of ice eigen frequency as a plate and upper water layer without ice cover) and to the waves at the minimum of the dispersion curve of the ice-water system. The free vibrations of the resonant waves have low amplitudes and can be adequately described by linear theory of elastic gravity wave propagation. Data are presented for sea ice thickness determined by measuring elastic-gravity waves at points in the Arctic basin for the years 1970 through 1992. During this period, a linear decrease in sea ice thickness was observed. The thickness decreased by 12-14 centimeters, or 3 to 4% of average thickenss, overall. Taking into account the significant scattering of data, a trend of climatic warming in the atmosphere-Arctic Ocean system is indicated. 11 refs., 2 figs.

  6. New age control on a mid-shelf grounding event in Eastern Basin, Ross Sea

    NASA Astrophysics Data System (ADS)

    Cone, A. N.; Bart, P. J.

    2009-12-01

    It is widely accepted that the West Antarctic Ice Sheet (WAIS) was grounded at the continental shelf edge in the eastern Ross Sea during the Last Glacial Maximum (LGM), but the precise chronology is debated. Post-LGM ice retreat chronologies have been developed using radiocarbon dating, mainly of acid-insoluble organics (AIO). Foraminifer tests yield more accurate radiocarbon dates than AIO because forams are less likely to be contaminated by allochthonous carbon, but unfortunately forams are sparse in Antarctic marine sediment cores. Here we show four consistent radiocarbon dates from forams in cored intervals within the foreset of a mid-continental-shelf grounding-zone wedge in Eastern Basin, Ross Sea. Our new radiocarbon dates reveal that the WAIS was grounded on the mid continental shelf circa 32,000 14C yr B.P., suggesting that retreat from this position began more than 10,000 years prior to the maximum sea level fall and global cooling associated with LGM. The dates contradict previous studies, which concluded that the WAIS was at its maximum shelf edge extent during LGM.

  7. Unveiling microbial activities along the halocline of Thetis, a deep-sea hypersaline anoxic basin

    PubMed Central

    Pachiadaki, Maria G; Yakimov, Michail M; LaCono, Violetta; Leadbetter, Edward; Edgcomb, Virginia

    2014-01-01

    Deep-sea hypersaline anoxic basins (DHABs) in the Eastern Mediterranean Sea are considered some of the most hostile environments on Earth. Little is known about the biochemical adaptations of microorganisms living in these habitats. This first metatranscriptome analysis of DHAB samples provides significant insights into shifts in metabolic activities of microorganisms as physicochemical conditions change from deep Mediterranean sea water to brine. The analysis of Thetis DHAB interface indicates that sulfate reduction occurs in both the upper (7.0–16.3% salinity) and lower (21.4–27.6%) halocline, but that expression of dissimilatory sulfate reductase is reduced in the more hypersaline lower halocline. High dark-carbon assimilation rates in the upper interface coincided with high abundance of transcripts for ribulose 1,5-bisphosphate carboxylase affiliated to sulfur-oxidizing bacteria. In the lower interface, increased expression of genes associated with methane metabolism and osmoregulation is noted. In addition, in this layer, nitrogenase transcripts affiliated to uncultivated putative methanotrophic archaea were detected, implying nitrogen fixation in this anoxic habitat, and providing evidence of linked carbon, nitrogen and sulfur cycles. PMID:24950109

  8. Diseases and parasites of the sea lamprey, Petromyzon marinus, in the Lake Huron basin

    USGS Publications Warehouse

    McLain, Alberton L.

    1952-01-01

    Sea lampreys from the Lake Huron basin carried no external parasites and showed a fairly low degree of infection by internal parasites. The material examined represented three life-history stages of the sea lamprey. Recently transformed downstream migrants (215 specimens) harbored only nematodes belonging to the genus Camallanus. The percentage of infection was 2.3. Active feeders from the lake (29 lampreys) revealed the highest degree of parasitism (31.0 percent) with the following parasites present: Echinorhynchus coregoni Linkins; Triaenophorus crassus Forel; and Camallanus sp. Among the 257 sexually mature upstream migrants (14.8 percent infected) Echinorhynchus coregoni and E. leidyi Van Cleave were the most common. Only occasional nematodes and cestodes were found, which fact indicates a failure of the lamprey to carry these parasites to the end of its natural life. Of the parasites observed, only the nematodes gave evidence of serious damage to the host. The study suggests that the role played by parasites in the natural control of the sea lamprey in its new habitat in the upper Great Lakes is of minor importance.

  9. Water mass transformation in the deep basins of the Nordic Seas: Analyses of heat and freshwater budgets

    NASA Astrophysics Data System (ADS)

    Latarius, K.; Quadfasel, D.

    2016-08-01

    In the Arctic Mediterranean a transformation of Atlantic Water, flowing in near the surface, into overflow water, which leaves the area at depth, takes place. For this transformation the Nordic Seas are of particular importance, as they are largely ice-free and thus heat loss to the atmosphere during winter is strong. Since 2001 Argo-type profiling float measurements have been carried out in the region and enable the observation of hydrography during the whole year. The measurements concentrate on the deep basins, the Norwegian Basin, Lofoten Basin, Greenland Sea and Icelandic Plateau. They are analysed with special emphasis on the seasonal cycle in hydrography. Based on the mean seasonal cycle of temperature and salinity and atmospheric fluxes from reanalysis products for the first decade of this century heat and freshwater budgets are calculated. The residuum in the budgets gives the lateral exchange of water between the inner basins and the boundary current, circumnavigating the whole area. This lateral exchange is identified with the contribution of the deep basins to the water mass transformation within the Nordic Seas. Budget calculations, using atmospheric flux data from NCEP with corrections for high latitudes, yield a contribution of 18% to the total temperature decrease and 6% to the total salinity decrease in the Arctic Mediterranean, although the basins account for only 4% of the total area. The density increase nearly exclusively takes place in the eastern basins, whereas the Greenland Sea plays an important role in matching the temperature and salinity characteristic of the overflow water. An increasing amount of freshwater in the surface layer will have only minor effects on the strength of the overflows across the Greenland-Iceland-Scotland Ridge.

  10. Geometry and subsidence history of the Dead Sea basin: A case for fluid-induced mid-crustal shear zone?

    USGS Publications Warehouse

    ten Brink, U.S.; Flores, C.H.

    2012-01-01

    Pull-apart basins are narrow zones of crustal extension bounded by strike-slip faults that can serve as analogs to the early stages of crustal rifting. We use seismic tomography, 2-D ray tracing, gravity modeling, and subsidence analysis to study crustal extension of the Dead Sea basin (DSB), a large and long-lived pull-apart basin along the Dead Sea transform (DST). The basin gradually shallows southward for 50 km from the only significant transverse normal fault. Stratigraphic relationships there indicate basin elongation with time. The basin is deepest (8-8.5 km) and widest (???15 km) under the Lisan about 40 km north of the transverse fault. Farther north, basin depth is ambiguous, but is 3 km deep immediately north of the lake. The underlying pre-basin sedimentary layer thickens gradually from 2 to 3 km under the southern edge of the DSB to 3-4 km under the northern end of the lake and 5-6 km farther north. Crystalline basement is ???11 km deep under the deepest part of the basin. The upper crust under the basin has lower P wave velocity than in the surrounding regions, which is interpreted to reflect elevated pore fluids there. Within data resolution, the lower crust below ???18 km and the Moho are not affected by basin development. The subsidence rate was several hundreds of m/m.y. since the development of the DST ???17 Ma, similar to other basins along the DST, but subsidence rate has accelerated by an order of magnitude during the Pleistocene, which allowed the accumulation of 4 km of sediment. We propose that the rapid subsidence and perhaps elongation of the DSB are due to the development of inter-connected mid-crustal ductile shear zones caused by alteration of feldspar to muscovite in the presence of pore fluids. This alteration resulted in a significant strength decrease and viscous creep. We propose a similar cause to the enigmatic rapid subsidence of the North Sea at the onset the North Atlantic mantle plume. Thus, we propose that aqueous fluid flux

  11. Education and Raising Awareness of Seismic Risk in the Black Sea Basin

    NASA Astrophysics Data System (ADS)

    Florin Balan, Stefan; Alcaz, Vasile; Trifonova, Petya; Uker, Nalan; Tataru, Dragos

    2014-05-01

    The Project "Black Sea Earthquake Safety Net(work)" ESNET has the intention to educate and raise awareness of seismic risk in the Black Sea Basin in four countries: Moldova, Romania, Bulgaria and Turkey. The project is financed through "The Black Sea Basin Joint Operational Programme", an EU operational programmes under European Neighborhood & Partnership Instrument (ENPI). The programme is financed by ENPI. The participation of Turkey is financed by Instrument for Pre-accession Assistance. It is implemented during the period 2007 - 2013. The project wants to contribute to the prevention of natural disasters generated by earthquakes in Black Sea Basin by developing a joint monitoring and intervention concept. All the countries involved in the project have their own studies, strategies, prevention and intervention systems in case of earthquakes, but until now there has not been an integrated approach so far in the Black Sea Basin. Given the cross-border character of seismic activity, it is necessary to have a cross-border approach on prevention, monitoring and intervention in case of earthquakes. Main objectives : 1. The assessment of the disaster potential, with accent on the seismic risk degree and the earthquakes effects in the intervention area. For achieving the main objective is to have an accurate and up-to-date assessment of the potential of disasters provoked by earthquakes in the project area/regions. This assessment will be carried out at national level and will be used in designing the common concept/approach for dealing with earthquakes at regional level, thus ensuring the cross-border character of the objective. 2.To develop an integrated seismic monitoring and intervention concept. This integrated concept, built on the basis of the previous objective, will have a cross-border relevance and is at the core of the action. The monitoring and intervention in case of earthquakes will be coordinated among the participating countries based on this, thus a

  12. Stratigraphic correlation for the IODP Expedition 347 - toward an integrated Baltic Sea Basin stratigraphy

    NASA Astrophysics Data System (ADS)

    Kotilainen, Aarno; Hyttinen, Outi; Andrén, Thomas; Cotterill, Carol; Hale, Walter; IODP Expedition 347 Science Party, the

    2014-05-01

    The IODP Expedition 347 - "Baltic Sea Paleoenvironment" completed in September - November 2013 (offshore phase) was the 5th and the final mission-specific platform (MSP) expedition of the Integrated Ocean Drilling Program. The expedition used a geotechnical drillship, the Greatship Manisha equipped with a Geoquip Marine coring rig, to core and wireline-log several sub-basins within the Baltic Sea, aiming to produce new information on the history of the Baltic Sea and climate change during the last glacial cycle. During the IODP Expedition 347 altogether over 1900 meters were successfully drilled at 8 Sites (M0059 - M0067) in the Lille Belt, Kattegat, Ångermanälven Estuary, Landsort Deep, Hanö Basin and Bornholm Basin with core recovery of approximately 1600 m (expansion adjusted core recovery of 91.46%). In this presentation, we show the preliminary results of regional stratigraphic correlation and splice results for the Expedition. That information provides a solid base for stratigraphic and high-resolution paleoenvironmental studies. Stratigraphic correlation consisted of the following: (1) ensuring the maximum core recovery on site, (2) seismic-core (sedimentary facies) correlation and (3) generating composite depth scales and splice records to each site. To obtain a complete sedimentary record, multiple adjacent holes were cored with an offset in depth of 0.5-1.5 m between cores from different holes. The continuity of recovery was assessed by generating composite sections that align prominent features in physical property data from adjacent holes. With the information gained by Fast Track Multi-Sensor Core Logger (MSCL) data, it was possible to adjust coring plan before the new hole, to ensure that intervals missing in previous cores could be recovered from an adjacent hole. Correlation between seismic profiles and cores used a simple estimation sound velocity vs. sediment type. Acquired depth was tested by comparison with major core surfaces, downhole logs

  13. Assessment of undiscovered oil and gas resources of the North Caspian Basin, Middle Caspian Basin, North Ustyurt Basin, and South Caspian Basin Provinces, Caspian Sea Area, 2010

    USGS Publications Warehouse

    Klett, T.R.; Schenk, Christopher J.; Charpentier, Ronald R.; Gautier, Donald L.; Brownfield, Michael E.; Pitman, Janet K.; Cook, Troy A.; Tennyson, Marilyn E.

    2010-01-01

    The U.S. Geological Survey estimated mean volumes of technically recoverable, conventional, undiscovered petroleum resources at 19.6 billion barrels of crude oil, 243 trillion cubic feet of natural gas, and 9.3 billion barrels of natural gas liquids for the Caspian Sea area, using a geology-based assessment methodology.

  14. Buried paleo-sedimentary basins in the north-eastern Black Sea-Azov Sea area and tectonic implications (DOBRE-2)

    NASA Astrophysics Data System (ADS)

    Starostenko, Vitaly; Stephenson, Randell; Janik, Tomasz; Tolkunov, Anatoly

    2014-05-01

    A number of independent but inter-related projects carried out under the auspices of various national and international programmes in Ukraine including DARIUS were aimed at imaging the upper lithosphere, crustal and sedimentary basin architecture in the north-eastern Black Sea, southern Crimea and Kerch peninsulas and the Azov Sea. This region marks the transition from relatively undisturbed Precambrian European cratonic crust and lithosphere north of the Azov Sea to areas of significant Phanerozoic tectonics and basin development, in both extensional as well as compressional environments, to the south, including the eastern Black Sea rift, which is the main sedimentary basin of the study area. The wide-angle reflection and refraction (WARR) profile DOBRE-2, a Ukrainian national project with international participation (see below), overlapping some 115 km of the southern end of the DOBREfraction'99 profile (that crosses the intracratonic Donbas Foldbelt) in the north and running to the eastern Black Sea basin in the south, utilised on- and offshore recording and energy sources. It maps crustal velocity structure across the craton margin and documents, among other things, that the Moho deepens from 40 km to ~47 km to the southwest below the Azov Sea and Crimean-Caucasus deformed zone. A regional CDP seismic profile coincident with DOBRE-2, crossing the Azov Sea, Kerch Peninsula and the north-eastern Black Sea southwest to the Ukraine-Turkey border, acquired by Ukrgeofisika (the Ukrainian national geophysical company) reveals in its inferred structural relationships the ages of Cretaceous and younger extensional and subsequent basin inversion tectonic events as well as the 2D geometry of basement displacement associated with post mid-Eocene inversion. A direct comparison of the results of the WARR velocity model and the near-vertical reflection structural image has been made by converting the former into the time domain. The results dramatically demonstrate that

  15. Sources and pathways of polycyclic aromatic and saturated hydrocarbons in the Arkona Basin (Southern Baltic Sea, Central Europe)

    SciTech Connect

    Schulz, H.M.

    1996-12-31

    The Baltic Sea (Central Europe) is surrounded by coastal regions with long histories of industrialization. The heavy metal profiles in the sediments in the center of the Arkona Basin, one of the depressions of the southern Baltic Sea area, clearly reflect the historical anthropogenic influence. The Arkona Basin-is the final sink for materials derived from the Oder river which drains a highly polluted industrial area of Eastern Europe. Surficial muddy sediments from a close-meshed field of sampling-points were analyzed for distribution patterns of aliphatics and quantities and ratios of selected polycyclic aromatic hydrocarbons (PAH). These compounds are thought to reflect anthropogenic pollution related to emissions from traffic, heating, etc. We use these marker substances to test if the basin sediments reflect riverine input, and if additional sources can be identified.

  16. Creeping Environmental Problems and Sustainable Development in the Aral Sea Basin

    NASA Astrophysics Data System (ADS)

    Glantz, Michael

    1999-05-01

    Environmental degradation in the Aral Sea basin in Central Asia has been a touchstone for increasing public awareness of environmental issues. The Aral crisis has been touted as a "quiet Chernobyl" and as one of the worst human-made environmental catastrophes of the twentieth century. This multidisciplinary book is the first to comprehensively describe the slow onset of low grade but incremental changes (i.e., creeping environmental change) that affected the region and its peoples. Through a set of case studies, it describes how the region's decision-makers allowed these changes to grow into an environmental and societal nightmare. It outlines many lessons to be learned for other areas undergoing detrimental creeping environmental change, and provides an important example of how to approach such disasters for students and researchers of environmental studies, global change, political science and history.

  17. Gas hydrates in the deep water Ulleung Basin, East Sea, Korea.

    NASA Astrophysics Data System (ADS)

    Ryu, Byong-Jae

    2016-04-01

    Studies on gas hydrates in the deep-water Ulleung Basin, East Sea, Korea was initiated by the Korea Institute of Geoscience and Mineral Resources (KIGAM) to secure the future energy resources in 1996. Bottom simulating reflectors (BSRs) were first identified on seismic data collected in the southwestern part of the basin from 1998 to 1999. Regional geophysical surveys and geological studies of gas hydrates in the basin have been carried out by KIGAM from 2000 to 2004. The work included 12,367 km of 2D multi-channel seismic reflection lines and 38 piston cores 5 to 8 m long. As a part of the Korean National Gas Hydrate Program that has been performed since 2005, 6690 km of 2D multi-channel reflection seismic lines, 900 km2 of 3D seismic data, 69 piston cores and three PROD cores were additionally collected. In addition, two gas hydrate drilling expeditions were performed in 2007 and 2010. Cracks generally parallel to beddings caused by the dissociation of gas hydrate were often observed in cores. The lack of higher hydrocarbons and the carbon isotope ratios indicate that the methane is primarily biogenic. The seismic data showed clear and wide-spread bottom-simulating reflectors (BSRs). The BSR was identified by (a) its polarity opposite to the seafloor, (b) its seafloor-parallel reflection behavior, and (c) its occurrence at a sub-bottom depth corresponding to the expected base of gas hydrate stability zone. Several vertical to sub-vertical chimney-like blank zones up to several kilometers in diameter were also identified in the study area. They are often associated with velocity pull-up structures that are interpreted due to higher velocity in gas hydrate-bearing deposits. Seismic velocity analysis also showed a high velocity anomaly within the pull-up structure. Gas hydrate samples were collected from the shallow sedimentary section of blanking zone by piston coring in 2007. BSRs mainly occur in the southern part of the basin. They also locally observed in the

  18. Seismic blanking zones in the deep-water Ullung Basin, East Sea of Korea.

    NASA Astrophysics Data System (ADS)

    Ryu, Byong-Jae; Riedel, Michael; Yoo, Dong-Geun

    2015-04-01

    A total 12366.395 L.km of 2D multichannel seismic data were acquired by the Korea Institute of Geoscience and Mineral Resources (KIGAM) for detecting and mapping seismic indicators for the presence of gas hydrate in the deep-water Ulleung Basin, East Sea of Korea. The seismic data were acquired using Trilogy System of Geco-Prakla, Bolt Air-gun System onboard the R/V TAMHAE II of KIGAM during the years of 2000 to 2004. The seismic faices of shallow sediments were also analyzed to understand the sedimentary strata developed in the basin. Seismic data were processed to define gas hydrate indicators such as bottom simulating reflectors (BSRs) and seismic blank zones. The BSR was identified by (a) its polarity opposite to the seafloor, (b) its seafloor-parallel reflection behavior, and (c) its occurrence at a sub-bottom depth corresponding to the expected base of gas hydrate stability zone, on heat flow and other thermal data for the region and on seismic velocity data. The seismic velocity analysis was also conducted for determining the velocity deviation effect of high-velocity gas hydrate and underlying low-velocity free gas. The BSRs occur mainly in the southern part of the basin where mass transport deposits are widely occurring. A number of vertical to sub-vertical seismic blanking zones were identified in the basin. The blanking zones are near-vertical broad chimney-like structures of reduced seismic reflectivity. They may be formed by gas and/or fluid upwelling through fractures and faults. Many of the blanking zones show apparent velocity pull-up effects of sediment layering structures that are interpreted to be a result of higher velocity gas hydrate. The presence of substantial amounts of gas hydrate in the blank zones were first found by piston coring in 2007, and subsequently confirmed by two deep-drilling expeditions in 2007 and 2010. Most of the blanking zones occur in well-bedded turbidite/hemi-pelagic sediments in the northern deep basin. The

  19. Unraveling the hydrocarbon charge potential of the Nordkapp Basin, Barents Sea: An integrated approach to reduce exploration risk in complex salt basins

    NASA Astrophysics Data System (ADS)

    Schenk, Oliver; Shtukert, Olga; Bishop, Andrew; Kornpihl, Kristijan; Milne, Graham

    2014-05-01

    The Nordkapp Basin, Barents Sea, is an intra-continental syn-rift basin containing many complex salt structures. The salt is late-Carboniferous to Early Permian in age, with regional extension in the Triassic initiating the salt movement resulting in formation of sub- and mini-basins with significant subsidence (especially in the northeastern part of the basin). Subsequent tectonic phases allowed growth and distortion of salt diapirs that were later affected by uplift and erosion during Tertiary resulting in the formation of salt-related traps in Triassic and Lower Jurassic strata. During Plio-Pleistocene, glacial erosion removed additional Mesozoic and Cenozoic strata. This basin is regarded as a frontier salt province. A small hydrocarbon discovery (Pandora well) in the southwestern part of the basin points to the presence several functioning petroleum systems. The primary play type is related to salt traps below overhangs. Such structures are however, very difficult to image with conventional seismic techniques due to i) generation of multiples from sea floor and top of shallow salt bodies and ii) seismic shadow zones within the salt (possibly resulting from shale and carbonate stringers) which cause severe diffractions so that prospective areas adjacent to the salt remain elusive. Arctic exploration is expensive and the ability to focus on the highest potential targets is essential. A unique solution to this challenging subsurface Arctic environment was developed by integrating petroleum system modeling with full azimuth broadband seismic acquisition and processing. This integrated approach allows intelligent location of seismic surveys over structures which have the maximum chance of success of hydrocarbon charge. Petroleum system modeling was conducted for four seismic sections. Salt was reconstructed according to the diapiric evolution presented in Nilsen et al. (1995) and Koyi et al. (1995). Episodes of major erosion were assigned to Tertiary (tectonic) and

  20. Fate of copper complexes in hydrothermally altered deep-sea sediments from the Central Indian Ocean Basin.

    PubMed

    Chakraborty, Parthasarathi; Sander, Sylvia G; Jayachandran, Saranya; Nath, B Nagender; Nagaraju, G; Chennuri, Kartheek; Vudamala, Krushna; Lathika, N; Mascarenhas-Pereira, Maria Brenda L

    2014-11-01

    The current study aims to understand the speciation and fate of Cu complexes in hydrothermally altered sediments from the Central Indian Ocean Basin and assess the probable impacts of deep-sea mining on speciation of Cu complexes and assess the Cu flux from this sediment to the water column in this area. This study suggests that most of the Cu was strongly associated with different binding sites in Fe-oxide phases of the hydrothermally altered sediments with stabilities higher than that of Cu-EDTA complexes. The speciation of Cu indicates that hydrothermally influenced deep-sea sediments from Central Indian Ocean Basin may not significantly contribute to the global Cu flux. However, increasing lability of Cu-sediment complexes with increasing depth of sediment may increase bioavailability and Cu flux to the global ocean during deep-sea mining.

  1. An attempt to deconstruct recent climate change in the Baltic Sea basin

    NASA Astrophysics Data System (ADS)

    Barkhordarian, A.; Storch, H.; Zorita, E.; Gómez-Navarro, J. J.

    2016-11-01

    We investigate whether the recently observed temperature and precipitation trends over the Baltic Sea Basin are consistent with state-of-the-art regional climate model projections. To address this question we use several data sources: (1) multidecadal trends derived from various observational data sets, (2) estimates of natural variability provided by a 2000 year paleoclimatic model simulation, and (3) response to greenhouse gas forcing derived from regional climate simulations driven by the A1B and RCP4.5 scenarios (from ENSEMBLES and CORDEX projects). Results indicate that, over the past decades, the climate in the Baltic Sea Basin has undergone a change that is beyond the estimated range of natural variability. We test the hypothesis that this change may be understood as a manifestation of global warming due to increasing concentrations of greenhouse gases (GHGs). We find that changes in near-surface temperature support our hypothesis that the effect of GHG is needed to simulate the observed changes. The pattern correlation and regression results clearly illustrate the concerted emergence of an anthropogenic signal consistent with the GHG signal in summer and autumn in the 21st century. However, none of the 19 regional climate simulations used in this study reproduce the observed warming. The observed trends in precipitation and surface solar radiation are also partially inconsistent with the expected changes due to GHG forcing. We conclude that, besides the regional response to GHG forcing, other human-made drivers have had an imprint. Regional emission of industrial aerosols has been strongly reduced in this region, and we suggest that this reduction may be the missing driver.

  2. Magnitude-frequency distribution of submarine landslides in the Gioia Basin (southern Tyrrhenian Sea)

    NASA Astrophysics Data System (ADS)

    Casas, D.; Chiocci, F.; Casalbore, D.; Ercilla, G.; de Urbina, J. Ortiz

    2016-12-01

    Regional inventories and magnitude-frequency relationships provide critical information about landslides and represent a first step in landslide hazard assessment. Despite this, the availability of accurate inventories in the marine environment remains poor because of the commonly low accessibility of high-resolution data at regional scales. Evaluating high-resolution bathymetric data spanning the time interval 2007-2011 for the Gioa Basin of the southern Tyrrhenian Sea yielded a landslide inventory of 428 events affecting an area of >85 km2 and mobilizing approximately 1.4 km3 of sediment. This is the first time that this area is studied in such detail, justifying comparison with other areas both onland and offshore. Statistical analyses revealed that the cumulative distribution of the dataset is characterized by two right-skewed probability distributions with a heavy tail. Moreover, evidence of a rollover for smaller landslide volumes is consistent with similar trends reported in other settings worldwide. This may reflect an observational limitation and the site-specific geologic factors that influence landslide occurrence. The robust validation of both power-law and log-normal probability distributions enables the quantification of a range of probabilities for new extreme events far from the background landslide sizes defined in the area. This is a useful tool at regional scales, especially in geologically active areas where submarine landslides can occur frequently, such as the Gioia Basin.

  3. Forming factors of gas hydrate chimney in the Ulleung Basin, East Sea

    NASA Astrophysics Data System (ADS)

    Kang, Dong-Hyo; Chun, Jong-Hwa; Koo, Nam-Hyng; Kim, Won-Sik; Lee, Ho-Young; Lee, Joo-Yong

    2016-04-01

    Seismic chimneys ranging in width from 200 m to 1,000 m are observed in the seismic sections obtained in the Ulleung Basin, East Sea. In consequence of Ulleung Basin Gas Hydrate Expedition 1 and 2, concentrations of gas hydrates were identified. Especially, 6 chimney sites were drilled and the occurrence of gas hydrate was identified at all wells. Through the interpreting seismic section, three factors affect the formation of gas hydrate chimney; mass transport deposit, fault, igneous intrusion. These three factors result in three case of forming gas hydrate chimney. Firstly, gas hydrate chimney appears predominantly in the fault zone. Deep-rooted fault reach to mass transport deposit and gas hydrate chimney which is mostly rooted in mass transport deposit is formed. Secondly, Gas hydrate chimney appears linked to igneous intrusion. Igneous intrusion result in forming fault in overlying strata. Similar to first case, this fault traverses mass transport deposit and gas hydrate chimney rooted in mass transport deposit is created. Thirdly, gas hydrate chimney is formed at thick mass transport deposit without fault. In this case, chimney is not reach to seabed in contrast with first and second case. The thickness of mass transport deposit is 0.2 second in two-way travel times. Overburden load cause to pressure at the upper part of mass transport deposit. This leads to fracture in overlying sediments and form gas hydrate chimney.

  4. Estimating the regional climate responses over river basins to changes in tropical sea surface temperature patterns

    NASA Astrophysics Data System (ADS)

    Tsai, Chii-Yun; Forest, Chris E.; Wagener, Thorsten

    2015-10-01

    We investigate how to identify and assess teleconnection signals between anomalous patterns of sea surface temperature (SST) changes and climate variables related to hydrologic impacts over different river basins. The regional climate sensitivity to tropical SST anomaly patterns is examined through a linear relationship given by the global teleconnection operator (GTO, also generally called a sensitivity matrix or an empirical Green's function). We assume that the GTO defines a multilinear relation between SST forcing and regional climate response of a target area. The sensitivities are computed based on data from a large ensemble of simulations using the NCAR Community Atmospheric Model version 3.1 (CAM 3.1). The linear approximation is evaluated by comparing the linearly reconstructed response with both the results from the full non-linear atmospheric model and observational data. The results show that the linear approximation can capture regional climate variability that the CAM 3.1 AMIP-style simulations produce at seasonal scales for multiple river basins. The linear method can be used potentially for estimating drought conditions, river flow forecasting, and agricultural water management problems.

  5. A review and assessment of gas hydrate potential in Çınarcık Basin, Sea of Marmara

    NASA Astrophysics Data System (ADS)

    Sile, Hande; Akin, Cansu; Ucarkus, Gulsen; Namik Cagatay, M.

    2016-04-01

    The Sea of Marmara (NW Turkey), an intracontinental sea between the Mediterranean and Black Seas, is located in a tectonically active region with the formation of shallow gas hydrates and free gas. It is widely known that, Sea of Marmara sediments are organic-rich and conducive to production of methane, which is released on the sea floor through active fault segments of the North Anatolian Fault (Geli et al., 2008). Here we study the gas hydrate potential of the Çınarcık Basin using published data and our core analyses together with gas hydrate stability relations. The gas sampled in the Çınarcık Basin is composed mainly of biogenic methane and trace amounts of heavier hydrocarbons (Bourry et al., 2009). The seafloor at 1273 m depth on the Çınarcık Basin with temperature of 14.5oC and hydrostatic pressure of 127.3 atm corresponds to the physical limit for gas hydrate formation with respect to phase behavior of gas hydrates in marine sediments (Ménot and Bard, 2010). In order to calculate the base of the gas hydrate stability zone in Çınarcık Basin, we plotted T (oC) calculated considering the geothermal gradient versus P (atm) on the phase boundary diagram. Below the seafloor, in addition to hydrostatic pressure (10 Mpa/km), we calculated lithostatic pressure due to sediment thickness considering the MSCL gamma ray density values (~1.7 gr/cm3). Our estimations show that, gas hydrate could be stable in the upper ~20 m of sedimentary succession in Çınarcık Basin. The amount of gas hydrate in the Çınarcık Basin can be determined using the basinal area below 1220 m depth (483 km2) and average thickness of the gas hydrate stability zone (20 m) and the sediment gas hydrate saturation (1.2 % used as Milkov, 2004 suggested). The calculations indicate the potential volume of gas hydrate in Çınarcık Basin as ~11.6x107 m3. Such estimates are helpful for the consideration of gas hydrates as a new energy resource, for assessment of geohazards or their

  6. Neodymium isotopes in the Mediterranean Sea: comparison between seawater and sediment signals

    NASA Astrophysics Data System (ADS)

    Tachikawa, K.; Roy-Barman, M.; Michard, A.; Thouron, D.; Yeghicheyan, D.; Jeandel, C.

    2004-07-01

    Nine depth-profiles of dissolved Nd concentrations and isotopic ratios (ɛ Nd) were obtained in the Levantine Basin, the Ionian, the Aegean, the Alboran Seas and the Strait of Gibraltar. Thirteen core-top sediments and Nile River particle samples were also analyzed (leached with 1 N HCl, acetic acid or hydroxylamine hydrochloride). The seawater ɛ Nd values become more radiogenic during the eastward circulation in the Mediterranean Sea. The relationship between salinity and the seawater ɛ Nd shows that the Nd isotopic signature is more conservative than salinity in the Mediterranean Sea. The water mass with the highest ɛ Nd (-4.8) is found at about 200 m in the easternmost Levantine basin. The average ɛ Nd value for deep waters is -7.0 in the eastern basin, 2.5 ɛ-units higher than in the western basin. By examining the sensitivity of seawater ɛ Nd to Nd inputs from the Nile, we conclude that the most significant radiogenic Nd source is partially dissolved Nile River particles. The Nd flux from the Nile River water has a minor influence on the Mediterranean seawater ɛ Nd. Except for the easternmost Levantine Basin, the leachate ɛ Nd values are consistent with the seawater values. In the easternmost Levantine Basin, the leachate ɛ Nd values obtained with HCl leaching are systematically higher than the seawater values. The relationship between leachate and residual ɛ Nd values indicates that the HCl leaching partially dissolves lithogenic Nd, so the dissolution of Nile River particles is the cause of the observed shift. Some ɛ Nd values obtained with hydroxylamine hydrochloride leaching are higher than those obtained with HCl leaching. Although the reason for this shift is not clear, 87Sr/ 86Sr successfully detects the presence of a nonmarine component in the leachate. Our results suggest that leaching performance may vary with the mineralogy of marine sediments, at least in the case of the Mediterranean Sea.

  7. Propagated rifting in the Southwest Sub-basin, South China Sea: Insights from analogue modelling

    NASA Astrophysics Data System (ADS)

    Ding, Weiwei; Li, Jiabiao

    2016-10-01

    How the South China Sea rifted has long been a puzzling question that is still debated, particularly with reference to the Southwest Sub-basin (SWSB). Analogue modelling remains one of the most useful tools for testing rift models and processes. Here, we present and discuss a series of analogue modelling experiments designed to investigate the rifting process of the SWSB. Convincing geophysical results were compiled to provide realistic constraints to test the experimental results and interpretations. A heterogeneous lithosphere model with a varied lithospheric structure showed tectono-morphological features similar to the natural case of the SWSB, indicating that the initial thermal condition and rheological stratification of the lithosphere should have a dominant effect on the rifting process of the SWSB. Rigid tectonic blocks existed in the continental margin, such as the Macclesfield Bank and the Reed Bank, and they played important roles in both the shaping of the continent-ocean boundary and the coupling between the crust and mantle. The initial thermal condition and rheological stratification of the lithosphere under the South China Sea controlled the propagated rifting process of the SWSB. Extension was centred on the deep troughs between the rigid blocks, and the break-up occurred in these areas between them. The westward rifting propagation is best explained with a heterogeneous lithosphere model characterized by varied lithospheric structure, and it was responsible for producing the V-shaped configuration of the SWSB.

  8. Seismic stratigraphy and sedimentation of Magdalena Fan, Southern Colombian Basin, Caribbean Sea

    SciTech Connect

    Kolla, V.; Buffler, R.T.; Ladd, J.W.

    1984-03-01

    Analysis of all available seismic data from the Magdalena Fan in the southern Colombian basin, Caribbean Sea, allows subdivision of the sedimentary section into six seismic sequences (units). Although sediments were deposited in the present-day Magdalena Fan region since about Late Cretaceous, terrigenous sedimentation became significant only in the late Cenozoic during deposition of the upper three sequences associated with the uplifts of the Andes. These upper three sequences comprise the Magdalena Fan proper. The uppermost sequence probably represents the last main phase of sedimentation subsequent to the major uplift of the Andes in the Pliocene. The morphologic and shallow acoustic (3.5 kHz) characteristics of this fan unit are: upper fan, 1:60-1:110 gradients, channels having well-developed levees, and several subbottom reflectors in all areas except in channels; middle fan, 1:110-1:200 gradients, numerous channels with very subdued levees, and several to few subbottom reflectors; lower fan, < 1:250 gradients, small channels, relatively smooth sea floor, and few or no subbottom reflectors.

  9. Basin-wide N2 fixation in the deep waters of the Mediterranean Sea

    NASA Astrophysics Data System (ADS)

    Benavides, Mar; Bonnet, Sophie; Hernández, Nauzet; Martínez-Pérez, Alba María.; Nieto-Cid, Mar; Álvarez-Salgado, Xosé Antón; Baños, Isabel; Montero, María. F.; Mazuecos, Ignacio P.; Gasol, Josep M.; Osterholz, Helena; Dittmar, Thorsten; Berman-Frank, Ilana; Arístegui, Javier

    2016-06-01

    Recent findings indicate that N2 fixation is significant in aphotic waters, presumably due to heterotrophic diazotrophs depending on organic matter for their nutrition. However, the relationship between organic matter and heterotrophic N2 fixation remains unknown. Here we explore N2 fixation in the deep chlorophyll maximum and underneath deep waters across the whole Mediterranean Sea and relate it to organic matter composition, characterized by optical and molecular methods. Our N2 fixation rates were in the range of those previously reported for the euphotic zone of the Mediterranean Sea (up to 0.43 nmol N L-1 d-1) and were significantly correlated to the presence of relatively labile organic matter with fluorescence and molecular formula properties representative for peptides and unsaturated aliphatics and associated with the presence of more oxygenated ventilated water masses. Finally, and despite that the aphotic N2 fixation contributes largely to total water column diazotrophic activity (>50%), its contribution to overall nitrogen inputs to the basin is negligible (<0.5%).

  10. New insights into the organic carbon export in the Mediterranean Sea from 3-D modeling

    NASA Astrophysics Data System (ADS)

    Guyennon, A.; Baklouti, M.; Diaz, F.; Palmieri, J.; Beuvier, J.; Lebaupin-Brossier, C.; Arsouze, T.; Béranger, K.; Dutay, J.-C.; Moutin, T.

    2015-12-01

    The Mediterranean Sea is one of the most oligotrophic regions of the oceans, and nutrients have been shown to limit both phytoplankton and bacterial activities, resulting in a potential major role of dissolved organic carbon (DOC) export in the biological pump. Strong DOC accumulation in surface waters is already well documented, though measurements of DOC stocks and export flux are still sparse and associated with major uncertainties. This study provides the first basin-scale overview and analysis of organic carbon stocks and export fluxes in the Mediterranean Sea through a modeling approach based on a coupled model combining a mechanistic biogeochemical model (Eco3M-MED) and a high-resolution (eddy-resolving) hydrodynamic simulation (NEMO-MED12). The model is shown to reproduce the main spatial and seasonal biogeochemical characteristics of the Mediterranean Sea. Model estimations of carbon export are also of the same order of magnitude as estimations from in situ observations, and their respective spatial patterns are mutually consistent. Strong differences between the western and eastern basins are evidenced by the model for organic carbon export. Though less oligotrophic than the eastern basin, the western basin only supports 39 % of organic carbon (particulate and dissolved) export. Another major result is that except for the Alboran Sea, the DOC contribution to organic carbon export is higher than that of particulate organic carbon (POC) throughout the Mediterranean Sea, especially in the eastern basin. This paper also investigates the seasonality of DOC and POC exports as well as the differences in the processes involved in DOC and POC exports in light of intracellular quotas. Finally, according to the model, strong phosphate limitation of both bacteria and phytoplankton growth is one of the main drivers of DOC accumulation and therefore of export.

  11. Sea Level and Paleoenvironment Control on Late Ordovician Source Rocks, Hudson Bay Basin, Canada

    NASA Astrophysics Data System (ADS)

    Zhang, S.; Hefter, J.

    2009-05-01

    Hudson Bay Basin is one of the largest Paleozoic sedimentary basins in North America, with Southampton Island on its north margin. The lower part of the basin succession comprises approximately 180 to 300 m of Upper Ordovician strata including Bad Cache Rapids and Churchill River groups and Red Head Rapids Formation. These units mainly comprise carbonate rocks consisting of alternating fossiliferous limestone, evaporitic and reefal dolostone, and minor shale. Shale units containing extremely high TOC, and interpreted to have potential as petroleum source rocks, were found at three levels in the lower Red Head Rapids Formation on Southampton Island, and were also recognized in exploration wells from the Hudson Bay offshore area. A study of conodonts from 390 conodont-bearing samples from continuous cores and well cuttings from six exploration wells in the Hudson Bay Lowlands and offshore area (Comeault Province No. 1, Kaskattama Province No. 1, Pen Island No. 1, Walrus A-71, Polar Bear C-11 and Narwhal South O-58), and about 250 conodont-bearing samples collected from outcrops on Southampton Island allows recognition of three conodont zones in the Upper Ordovician sequence, namely (in ascendant sequence) Belodina confluens, Amorphognathus ordovicicus, and Rhipidognathus symmetricus zones. The three conodont zones suggest a cycle of sea level changes of rising, reaching the highest level, and then falling during the Late Ordovician. Three intervals of petroleum potential source rock are within the Rhipidognathus symmetricus Zone in Red Head Rapids Formation, and formed in a restricted anoxic and hypersaline condition during a period of sea level falling. This is supported by the following data: 1) The conodont Rhipidognathus symmetricus represents the shallowest Late Ordovician conodont biofacies and very shallow subtidal to intertidal and hypersaline condition. This species has the greatest richness within the three oil shale intervals to compare other parts of Red

  12. Spatial and temporal habitat partitioning by zooplankton in the Bornholm Basin (central Baltic Sea)

    NASA Astrophysics Data System (ADS)

    Schulz, Jan; Peck, Myron A.; Barz, Kristina; Schmidt, Jörn Oliver; Hansen, Frank C.; Peters, Janna; Renz, Jasmin; Dickmann, Miriam; Mohrholz, Volker; Dutz, Jörg; Hirche, Hans-Jürgen

    2012-12-01

    The deep basins in the Baltic Sea such as the Bornholm Basin (BB) are subject to seasonal changes in the strength of physico-chemical stratification. These depth-related changes in key abiotic factors are strong drivers of habitat partitioning by the autochthonous zooplankton community. Species-specific ecophysiological preferences often result in both seasonal and inter-annual changes in vertical abundance that, when combined with depth-specific water currents, also lead to horizontal differences in spatial distribution. The present study documented the seasonal and depth-specific changes in the abundance and species composition of zooplankton in the BB based upon broad-scale survey data: 832 vertically-resolved (10 m) multinet samples collected at nine stations between March 2002 and May 2003. Changes in the zooplankton community were significantly correlated with changes in ambient hydrography. Each of five taxa (Bosmina coregoni maritima, Acartia spp., Pseudocalanus spp., Temora longicornis, Synchaeta spp.) contributed >10% to the zooplankton community composition. The appearance of cladocerans was mainly correlated with the phenology of thermocline development in the spring. The cladoceran B. coregoni maritima was a dominant member of this community during the warmest periods, preferring the surface waters above the thermocline. Copepods exhibited distinct, ontogenetic and seasonal changes in their distribution. The rotifers (Synchaeta sp.) were the most abundant zooplankton in May. Based on a multivariate approach and the evaluation of vertical distribution patterns, five major habitat utilisation modes were identified that were based, to a large extent, on the dynamics of thermal and haline stratification of the Baltic Sea. Our statistical analysis of one of the most thorough datasets collected on Baltic zooplankton in recent decades reveals some of the factors that make this stratified system highly dynamic with respect to the spatial overlap between

  13. Anomalous bathymetry and palaeobathymetric models of the Mozambique Basin and Riiser Larsen Sea

    NASA Astrophysics Data System (ADS)

    Castelino, Jude A.; Eagles, Graeme; Jokat, Wilfried

    2016-12-01

    In this study we introduce a palaeobathymetric model for the conjugate Mozambique Basin and Riiser-Larsen Sea built by employing backstripping techniques, compensating for dynamic topography and plate motions. The model is presented at 0.2 ° × 0.2 ° grid resolution, making it suitable for future oceanographic and climate simulation model experiments aimed at a better understanding of the climatic and oceanographic relevance of oceanic gateways in the southern ocean. At the present day, the seafloor next to the Mozambican continental margin is around 300 m shallower, and that in the central Mozambique Channel is almost 1300 m shallower, than their conjugate areas or the predictions of oceanic thermal subsidence models. The cause of this anomalous depth is difficult to determine confidently because of sparse data, in particular concerning sediment thickness, and because of the wide range of amplitudes in modelled present-day dynamic topography. The distribution of shallow seafloor suggests that it might be attributed to the presence of thicker-than-usual oceanic crust, which in turn can be attributed to the Paleogene passage of the Quathlamba plume beneath the basin. We portray these effects in our palaeobathymetric models. In contrast, the Riiser-Larsen Sea has experienced fairly stable subsidence since its formation in Jurassic times, with only slight observable changes attributable to the onset of Antarctic glaciation and during the middle Miocene climate transition. Both basins display flexure over half-wavelengths of ∼60-80 km with amplitudes of 1500 m towards their continental margins. This plays an important role in models of palaeobathymetry for times older than 100 Ma. Near the margins, isolated areas of transitional or debatable crustal composition, including Beira High and Gunnerus Ridge, are depicted to subside in a similar fashion to oceanic crust. Further into the Indian Ocean, oceanic lithosphere younger than 100 Ma on both plates has subsided to

  14. Integrated interpretation to improve subsalt imaging: a case study from the Nordkapp Basin, Norwegian Barents Sea

    NASA Astrophysics Data System (ADS)

    Olaf Müller, Christian; Brönner, Marco; Götze, Hans-Jürgen

    2015-04-01

    Seismic imaging of subsalt structures is still a difficult task and remaining uncertanties in the salt geometries makes exploration in the vicinity of such complex structures challenging. Gravity and magnetic data have proofed in the past their potential in combination with seismics to better delineate the shape of such salt structures. The current work deals with the improvement of subsalt imaging by combined interpretation of seismic and potential field data examined at a case study from the southern Nordkapp Basin. The Nordkapp Basin is a deep, narrow saliferous basin located in the southwestern Barents Sea. It comprises more than 30 salt diapirs, which are likely to create traps for hydrocarbons at their flanks and overhangs. Consequently exploration of the Nordkapp Basin with seismic methods started already in the 1980s, but until today solely seismics was not sufficient to reveal the nature and geometry for large parts of the basin. Therefore 2D and 3D seismic data were interpreted and used as stratigraphic constraints for the potential field modeling. For this purpose high resolution gravity and full tensor gravity gradient (FTG) data as well as a regional magnetic dataset were available. After processing the potential field data the 3D modeling was conducted by means of the interactive gravity and magnetic modeling software IGMAS+. Furthermore constraints for the rock properties, provided by well logs and susceptibility measurements of adjacent sedimentary well cores, were integrated. The favoured models indicate for both major salt structures a bulky base and a small root. The depth of the base of salt can vary in a range of about ± 300 m. Remaining mother salt is found in the northern part of the survey area and has no connection to the diapiric salt. Due to its higher sensibility to shallower sources the FTG data was used to model the flanks of the salt diapirs. In agreement with adjacent diapirs and encountered sequences a cap rock coverage was

  15. Cyclone trends constrain monsoon variability during Late Oligocene sea level highstands (Kachchh Basin, NW India)

    NASA Astrophysics Data System (ADS)

    Reuter, M.; Piller, W. E.; Harzhauser, M.; Kroh, A.

    2013-01-01

    Important concerns about the consequences of climate change for India are the potential impact on tropical cyclones and the monsoon. Herein we present a sequence of fossil shell beds from the shallow-marine Maniyara Fort Formation (Kachcch Basin) as an indicator of tropical cyclone activity along the NW Indian coast during the Late Oligocene warming period (~27-24 Ma). Direct proxies providing information about the atmospheric circulation dynamics over the Indian subcontinent at this time are important since it corresponds to a major climate reorganization in Asia that ends up with the establishment of the modern Asian monsoon system in the Early Miocene. The vast shell concentrations comprise a mixture of parautochthonous and allochthonous assemblages indicating storm-generated sediment transport from deep to shallow water during third-order sea level highstands. Three distinct skeletal assemblages were distinguished each recording a relative storm wave base depth. (1) A shallow storm wave base is shown by nearshore mollusks, corals and Clypeaster echinoids; (2) an intermediate storm wave base depth is indicated by lepidocyclind foraminifers, Eupatagus echinoids and corallinaceans; and (3) a deep storm wave base is represented by an Amussiopecten-Schizaster echinoid assemblage. Vertical changes in these skeletal associations give evidence of gradually increasing tropical cyclone intensity in line with third-order sea level rise. The intensity of cyclones over the Arabian Sea is primarily linked to the strength of the Indian monsoon. Therefore and since the topographic boundary conditions for the Indian monsoon already existed in the Late Oligocene, the longer-term cyclone trends were interpreted to reflect monsoon variability during the initiation of the Asian monsoon system. Our results imply an active monsoon over the Eastern Tethys at ~26 Ma followed by a period of monsoon weakening during the peak of the Late Oligocene global warming (~24 Ma).

  16. Possible connection between large volcanic eruptions and level rise episodes in the Dead Sea Basin

    NASA Astrophysics Data System (ADS)

    Bookman, Revital; Filin, Sagi; Avni, Yoav; Rosenfeld, Daniel; Marco, Shmuel

    2014-04-01

    The June 1991 Pinatubo volcanic eruption perturbed the atmosphere, triggering short-term worldwide changes in surface and lower troposphere temperatures, precipitation, and runoff. The following winter was anomalously wet in the Levant, with a ˜2-m increase in the Dead Sea level that created a distinct morphological terrace along the lake's shore. Given the global radiative and chemical effects of volcanogenic aerosols on climatic systems, we tested the hypothesis that the 1991-92 winter shore terrace is a modern analogue to the linkage between past volcanic eruptions and a sequence of shore terraces on the cliffs around the Dead Sea Basin (DSB). Sixteen shore terraces, detected using airborne laser scanning data, were interpreted as indicating short-term level rises due to episodes of enhanced precipitation and runoff during the dramatic drop in Lake Lisan's (palaeo-Dead Sea) level at the end of the Last Glacial Maximum. The terraces were compared with a dated time series of volcanogenic sulfate from the GISP2 ice core, and similar numbers of sulfate concentration peaks and shore terraces were found. Furthermore, a significant correlation was found between SO4 concentration peaks and the heights of the terraces. This correlation may indicate a link between the explosivity of past eruptions, the magnitude of stratospheric injection, and their impact on the northern hemisphere water balance. The record of such short-term climato-hydrological effects is made possible by the dramatic desiccation of Lake Lisan. Detailed records of such events, albeit rare because of their vulnerability and short longevity, provide an important demonstration of global climatic teleconnections.

  17. Deep-sea coral record of human impact on watershed quality in the Mississippi River Basin

    NASA Astrophysics Data System (ADS)

    Prouty, Nancy G.; Roark, E. Brendan; Koenig, Alan E.; Demopoulos, Amanda W. J.; Batista, Fabian C.; Kocar, Benjamin D.; Selby, David; McCarthy, Matthew D.; Mienis, Furu

    2014-01-01

    One of the greatest drivers of historical nutrient and sediment transport into the Gulf of Mexico is the unprecedented scale and intensity of land use change in the Mississippi River Basin. These landscape changes are linked to enhanced fluxes of carbon and nitrogen pollution from the Mississippi River, and persistent eutrophication and hypoxia in the northern Gulf of Mexico. Increased terrestrial runoff is one hypothesis for recent enrichment in bulk nitrogen isotope (δ15N) values, a tracer for nutrient source, observed in a Gulf of Mexico deep-sea coral record. However, unambiguously linking anthropogenic land use change to whole scale shifts in downstream Gulf of Mexico biogeochemical cycles is difficult. Here we present a novel approach, coupling a new tracer of agro-industrialization to a multiproxy record of nutrient loading in long-lived deep-sea corals collected in the Gulf of Mexico. We found that coral bulk δ15N values are enriched over the last 150-200 years relative to the last millennia, and compound-specific amino acid δ15N data indicate a strong increase in baseline δ15N of nitrate as the primary cause. Coral rhenium (Re) values are also strongly elevated during this period, suggesting that 34% of Re is of anthropogenic origin, consistent with Re enrichment in major world rivers. However, there are no pre-anthropogenic measurements of Re to confirm this observation. For the first time, an unprecedented record of natural and anthropogenic Re variability is documented through coral Re records. Taken together, these novel proxies link upstream changes in water quality to impacts on the deep-sea coral ecosystem.

  18. Deep-sea coral record of human impact on watershed quality in the Mississippi River Basin

    NASA Astrophysics Data System (ADS)

    Prouty, N.; Roark, B.; Koenig, A.; Batista, F. C.; Kocar, B. D.; Selby, D. S.; Mccarthy, M. D.; Mienis, F.; Ross, S. W.; Demopoulos, A. W.

    2015-12-01

    One of the greatest drivers of historical nutrient and sediment transport into the Gulf of Mexico is the unprecedented scale and intensity of land use change in the Mississippi River Basin. These landscape changes are linked to enhanced fluxes of carbon and nitrogen pollution from the Mississippi River, and persistent eutrophication and hypoxia in the northern Gulf of Mexico. Increased terrestrial runoff is one hypothesis for recent enrichment in bulk nitrogen isotope (δ15N) values, a tracer for nutrient source, observed in a Gulf of Mexico deep-sea coral record. However, unambiguously linking anthropogenic land use change to whole scale shifts in downstream Gulf of Mexico biogeochemical cycles is difficult. Here we present a novel approach, coupling a new tracer of agro-industrialization to a multiproxy record of nutrient loading in long-lived deep-sea corals collected in the Gulf of Mexico. We found that coral bulk δ15N values are enriched over the last 150-200 years relative to the last millennia, and compound-specific amino acid δ15N data indicate a strong increase in baseline δ15N of nitrate as the primary cause. Coral rhenium (Re) values are also strongly elevated during this period, suggesting that 34% of Re is of anthropogenic origin, consistent with Re enrichment in major world rivers. However, there are no pre-anthropogenic measurements of Re to confirm this observation. For the first time, an unprecedented record of natural and anthropogenic Re variability is documented through coral Re records. Taken together, these novel proxies link upstream changes in water quality to impacts on the deep-sea coral ecosystem.

  19. Deep-sea coral record of human impact on watershed quality in the Mississippi River Basin

    USGS Publications Warehouse

    Prouty, Nancy G.; Roark, E. Brendan; Koenig, Alan E.; Demopoulos, Amanda W. J.; Batista, Fabian C.; Kocar, Benjamin D.; Selby, David; McCarthy, Matthew D.; Mienis, Furu

    2014-01-01

    One of the greatest drivers of historical nutrient and sediment transport into the Gulf of Mexico is the unprecedented scale and intensity of land use change in the Mississippi River Basin. These landscape changes are linked to enhanced fluxes of carbon and nitrogen pollution from the Mississippi River, and persistent eutrophication and hypoxia in the northern Gulf of Mexico. Increased terrestrial runoff is one hypothesis for recent enrichment in bulk nitrogen isotope (δ15N) values, a tracer for nutrient source, observed in a Gulf of Mexico deep-sea coral record. However, unambiguously linking anthropogenic land use change to whole scale shifts in downstream Gulf of Mexico biogeochemical cycles is difficult. Here we present a novel approach, coupling a new tracer of agro-industrialization to a multiproxy record of nutrient loading in long-lived deep-sea corals collected in the Gulf of Mexico. We found that coral bulk δ15N values are enriched over the last 150–200 years relative to the last millennia, and compound-specific amino acid δ15N data indicate a strong increase in baseline δ15N of nitrate as the primary cause. Coral rhenium (Re) values are also strongly elevated during this period, suggesting that 34% of Re is of anthropogenic origin, consistent with Re enrichment in major world rivers. However, there are no pre-anthropogenic measurements of Re to confirm this observation. For the first time, an unprecedented record of natural and anthropogenic Re variability is documented through coral Re records. Taken together, these novel proxies link upstream changes in water quality to impacts on the deep-sea coral ecosystem.

  20. The surface circulation in the eastern basin of the Mediterranean Sea

    NASA Astrophysics Data System (ADS)

    Hamad, N.; Millot, C.; Taupier-Letage, I.

    2003-04-01

    The POEM-schema of the Atlantic Water (AW, http://ciesm.org/events/RT5-WaterMassAcronyms.pdf) circulation in the eastern basin of the Mediterranean Sea widely referred to nowadays (Robinson et al., 1991, completed by Robinson and Golnaraghi, 1993, and by Malanotte-Rizzoli et al., 1997) represents, in particular, a jet meandering offshore across the whole basin. No information is given on the southern part of the basin and no mention is made of a possible overall alongslope anticlockwise flow there, as suggested by a contemporaneous analysis of infrared satellite images (Le Vourch et al., 1992; Millot, 1992). A roughly similar controversy was elucidated in the western basin where such imagery was proven reliable. This has motivated the detailed analysis of daily and weekly composite images (about 1000) during the period 1996-2000, and of monthly composites available since 1985. Our analysis shows that AW circulates alongslope and anticlockwise around the whole basin, as indicated by Nielsen (1912) who considered the Coriolis effect as dominant. This circulation, which is permanent from Tunisia to Turkey, exists more or less temporarily in the Aegean, in the Ionian around Greece and in the Adriatic, due to the Etesians. However, a branch having spread for years (up to early 1998) from the channel of Sicily towards the northern Ionian before vanishing represents marked interannual (not seasonal) variability. Being unstable during most of its circuit, the AW flow generates mesoscale eddies which had not been correctly described before and which represent a relatively large amount of AW. Other eddies are known to be generated by orographic effects on the wind field, especially the Etesians. Both kinds of eddies play a fundamental role in spreading AW from alongslope towards the open basin. Although these eddies have characteristics almost specific to each subbasin and/or generation mechanism, the largest ones are anticyclonic, both kinds reach diameters of a few 100s km

  1. Bottom melting of Arctic Sea Ice in the Nansen Basin due to Atlantic Water influence

    NASA Astrophysics Data System (ADS)

    Muilwijk, Morven; Smedsrud, Lars H.; Meyer, Amelie

    2016-04-01

    Our global climate is warming, and a shrinking Arctic sea ice cover remains one of the most visible signs of this warming. Sea Ice loss is now visible for all months in all regions of the Arctic. Hydrographic and current observations from a region north of Svalbard collected during the Norwegian Young Sea Ice Cruise (N-ICE2015) are presented here. Comparison with historical data shows that the new observations from January through June fill major gaps in available observations, and help describing important processes linking changes in regional Atlantic Water (AW) heat transport and sea ice. Warm and salty AW originating in the North Atlantic enters the Arctic Ocean through the Fram Strait and is present below the Arctic Sea Ice cover throughout the Arctic. However, the depth of AW varies by region and over time. In the region north of Svalbard, we assume that depth could be governed primarily by local processes, by upstream conditions of the ice cover (Northwards), or by upstream conditions of the AW (Southwards). AW carries heat corresponding to the volume transport of approximately 9 SV through Fram Strait, varying seasonally from 28 TW in winter to 46 TW in summer. Some heat is recirculated, but the net annual heat flux into the Arctic Ocean from AW is estimated to be around 40 TW. The Atlantic Water layer temperature at intermediate depths (150-900m) has increased in recent years. Until recently, maximum temperatures have been found to be 2-3 C in the Nansen Basin. Studies have shown that for example, in the West Spitsbergen Current the upper 50-200m shows an overall AW warming of 1.1 C since 1979. In general we expect efficient melting when AW is close to the surface. Previously the AW entering through Fram Strait has been considered as less important because changes in the sea ice cover have been connected to greater inflow of Pacific Water through Bering Strait and atmospheric forcing. Conversely it is now suggested that AW has direct impact on melting of

  2. Assessment of Plio-Pleistocene Sea Surface Temperature Evolution Across Ocean Basins, Hemispheres, and Latitudes

    NASA Astrophysics Data System (ADS)

    Peterson, L.; Lawrence, K. T.; Mauriello, H.; Wilson, J.; Holte, L.

    2015-12-01

    New sea surface temperature (SST) records from the southern Pacific and southern Atlantic Oceans allow assessment of similarities and differences in climate evolution across ocean basins, hemispheres, and latitudes over the last 5 million years. Our high-resolution, alkenone-derived SST records from ODP Sites 1088 (South Atlantic, 41°S) and 1125 (South Pacific, 42°S) share strong structural similarities. When compared with SST records from the mid-latitudes of the northern hemisphere, these records provide compelling evidence for broadly hemispherically symmetrical open-ocean temperature evolution in both ocean basins as tropical warm pools contracted over the Plio-Pleistocene. This symmetry in temperature evolution occurs despite strong asymmetries in the development of the cryosphere over this interval, which was marked by extensive northern hemisphere ice sheet growth. Parallel SST evolution across ocean basins and hemispheres suggests that on longterm (>105 yr) timescales, many regions of the world ocean are more sensitive to the global energy budget than to local or regional climate dynamics, although important exceptions include coastal upwelling zone SSTs, high latitude SSTs, and benthic δ18O. Our analysis further reveals that throughout the last 5 Ma, temperature evolution in the extra-tropical Pacific of both hemispheres is very similar to the evolution of SST in the eastern equatorial Pacific upwelling zone, revealing tight coupling between the growth of meridional and equatorial Pacific zonal temperature gradients over this interval as both the extra-tropics and the eastern equatorial Pacific cold tongue underwent cooling. Finally, while long term temperature evolution is broadly consistent across latitudes and ocean basins throughout the entire Plio-Pleistocene, we see evidence that climate coupling on orbital timescales strengthened significantly at 2.7 Ma, at which point obliquity-band coherence emerges among diverse SST records. We attribute this

  3. Hydrological variations of the intermediate water masses of the western Mediterranean Sea during the past 20 ka inferred from neodymium isotopic composition in foraminifera and cold-water corals

    NASA Astrophysics Data System (ADS)

    Dubois-Dauphin, Quentin; Montagna, Paolo; Siani, Giuseppe; Douville, Eric; Wienberg, Claudia; Hebbeln, Dierk; Liu, Zhifei; Kallel, Nejib; Dapoigny, Arnaud; Revel, Marie; Pons-Branchu, Edwige; Taviani, Marco; Colin, Christophe

    2017-01-01

    We present the neodymium isotopic composition (ɛNd) of mixed planktonic foraminifera species from a sediment core collected at 622 m water depth in the Balearic Sea, as well as ɛNd of scleractinian cold-water corals (CWC; Madrepora oculata, Lophelia pertusa) retrieved between 280 and 442 m water depth in the Alboran Sea and at 414 m depth in the southern Sardinian continental margin. The aim is to constrain hydrological variations at intermediate depths in the western Mediterranean Sea during the last 20 kyr. Planktonic (Globigerina bulloides) and benthic (Cibicidoides pachyderma) foraminifera from the Balearic Sea were also analyzed for stable oxygen (δ18O) and carbon (δ13C) isotopes. The foraminiferal and coral ɛNd values from the Balearic and Alboran seas are comparable over the last ˜ 13 kyr, with mean values of -8.94 ± 0.26 (1σ; n = 24) and -8.91 ± 0.18 (1σ; n = 25), respectively. Before 13 ka BP, the foraminiferal ɛNd values are slightly lower (-9.28 ± 0.15) and tend to reflect higher mixing between intermediate and deep waters, which are characterized by more unradiogenic ɛNd values. The slight ɛNd increase after 13 ka BP is associated with a decoupling in the benthic foraminiferal δ13C composition between intermediate and deeper depths, which started at ˜ 16 ka BP. This suggests an earlier stratification of the water masses and a subsequent reduced contribution of unradiogenic ɛNd from deep waters. The CWC from the Sardinia Channel show a much larger scatter of ɛNd values, from -8.66 ± 0.30 to -5.99 ± 0.50, and a lower average (-7.31 ± 0.73; n = 19) compared to the CWC and foraminifera from the Alboran and Balearic seas, indicative of intermediate waters sourced from the Levantine basin. At the time of sapropel S1 deposition (10.2 to 6.4 ka), the ɛNd values of the Sardinian CWC become more unradiogenic (-8.38 ± 0.47; n = 3 at ˜ 8.7 ka BP), suggesting a significant contribution of intermediate waters originated from the western basin

  4. Primary carbonates and Ca-chloride brines as monitors of a paleo-hydrological regime in the Dead Sea basin

    NASA Astrophysics Data System (ADS)

    Waldmann, Nicolas; Starinsky, Abraham; Stein, Mordechai

    2007-09-01

    Lakes Samra, Lisan and the Dead Sea occupied the Dead Sea basin during the Last Interglacial (˜140-75 ka BP), last glacial (˜70-14 ka BP) and Holocene periods, respectively. The age of Lake Lisan and Samra was determined by U-Th dating of primary aragonites comprising parts of the lacustrine sedimentary sequences. The lakes have periodically deposited sequences of layered calcitic marls (Lake Samra) or laminated primary aragonite (Lake Lisan). The deposition of aragonite as the primary carbonate phase reflects the contribution of the incoming freshwater (loaded with bi-carbonate) and high Mg-, Ca-chloride brine that originated from the subsurface vicinity of the Dead Sea basin. Deposition of calcitic marls suggests a minor effect of the brines. The Ca-chloride subsurface brine has been migrating in and out of the wall rocks of the Dead Sea basin, reflecting the regional hydrological conditions. During most of the last glacial period and during the late Holocene, sufficient precipitation above the Judea Mountains pushed the subsurface Ca-chloride brines into the lakes causing the deposition of aragonite. During the Last Interglacial period the rain that precipitated above the Judea Mountains was insufficient to induce brine flow toward Lake Samra. It appears that sporadic floods provided calcium, bicarbonate and detritus to produce the Samra calcitic marls. Travertines deposited at the Samra-Lisan boundary indicate the early stage in the resumption of groundwater (springs) activity that led to the resurgence of Ca-chloride brine and rise of Lake Lisan. Similar variations in the regional rain precipitation and hydrological activity probably characterized the long-term geochemical evolution of Pleistocene lacustrine water-bodies in the Dead Sea basin, enabling the use of the carbonates as paleo-hydrological monitors.

  5. Reconstruction of the Mesozoic subduction in the South China Sea and its implications on the opening of the South China Sea basins

    NASA Astrophysics Data System (ADS)

    Li, F.; Sun, Z.; Yang, H.

    2013-12-01

    Reconstruction of the Mesozoic subduction system in the South China Sea (SCS) can improve our understanding of the tectonic evolution in the region and holds important implications on the opening of the SCS basins. Here we report the locations of the Mesozoic volcanic arc and trench in the SCS based on satellite-derived magnetic and gravimetric data, as well as drilling data from the China National Offshore Oil Corporation. The magnetic data allows us to identify the volcanic arc, which is characterized as high positive magnetic anomaly (HPMA) due to serpentinization. Furthermore, the volcanic arc is verified by distributions of intermediate rocks that are determined from the drilling data. The gravimetric data is used to determine the locations of the Mesozoic trench. Our preliminary results show two distinct HPMA belts along the two sides of the SCS basins. The first one locates northwest to the ridge axis of the SCS basins and extends from Taiwan in the northeast to the Xisha Island in the southwest. The second one locates on the Nansha-Dangerous Ground, southeast to the opening axis of the southwest sub-basin of the SCS, and is nearly parallel to the orientation of the first one. In addition, the distribution of intermediate rocks within the two HPMA belts indicates that the two belts represent the present locations of the Mesozoic volcanic arc. Furthermore, we recognize the corresponding Mesozoic trench by peak gross horizontal gradient of bouguer gravity anomaly in the northeastern SCS. It is located northwest to the ridge axis of the SCS basins and southeast to the Mesozoic arc. Moreover, drilling sample MZ-1-1 from the area between the Mesozoic arc and trench has shown clear signatures of forearc basin sediments, providing additional support to our arc and trench locations. Based on the opening direction of the SCS basins, we interpret that the two HPMA belts belong to the same Mesozoic volcanic arc that is located on the Eurasia continental crust. The arc

  6. Assessment and intercomparison of numerical simulations in the Western Mediterranean Sea

    NASA Astrophysics Data System (ADS)

    Juza, Mélanie; Mourre, Baptiste; Renault, Lionel; Tintoré, Joaquin

    2014-05-01

    The Balearic Islands Coastal Observing and Forecasting System (SOCIB, www.socib.es) is developing high resolution numerical simulations (hindcasts and forecasts) in the Western Mediterranean Sea (WMOP). WMOP uses a regional configuration of the Regional Ocean Modelling System (ROMS, Shchepetkin and McWilliams, 2005) with a high spatial resolution of 1/50º (1.5-2km). Thus, theses simulations are able to reproduce mesoscale and in some cases sub-mesoscale features that are key in the Mediterranean Sea since they interact and modify the basin and sub-basin circulation. These simulations are initialized from and nested in either the Mediterranean Forecasting System (MFS, 1/16º) or Mercator-Océan simulations (MERCATOR, 1/12º). A repeated glider section in the Ibiza Channel, operated by SOCIB, has revealed significant differences between two WMOP simulations using either MFS or MERCATOR (hereafter WMOP-MFS and WMOP-MERC). In this study, MFS, MERCATOR, WMOP-MFS and WMOP-MERC are compared and evaluated using available multi-platform observations such as satellite products (Sea Level Anomaly, Sea Surface Temperature) and in situ measurements (temperature and salinity profiles from Argo floats, CTD, XBT, fixed moorings and gliders; velocity fields from HF radar and currentmeters). A quantitative comparison is necessary to evaluate the capacity of the simulations to reproduce observed ocean features, and to quantify the possible simulations biases. This will in turn allow to improve the simulations, so as to produce better ocean forecast systems, to study and better understand ocean processes and to address climate studies. Therefore, various statistical diagnostics have been developed to assess and intercompare the simulations at various spatial and temporal scales, in different sub-regions (Alboran Sea, Western and Eastern Algerian sub-basins, Balearic Sea, Gulf of Lion), in different dynamical zones (coastal areas, shelves and "open" sea), along key sections (Ibiza and

  7. Basin-scale estimates of pelagic and coral reef calcification in the Red Sea and Western Indian Ocean

    PubMed Central

    Steiner, Zvi; Erez, Jonathan; Shemesh, Aldo; Yam, Ruth; Katz, Amitai; Lazar, Boaz

    2014-01-01

    Basin-scale calcification rates are highly important in assessments of the global oceanic carbon cycle. Traditionally, such estimates were based on rates of sedimentation measured with sediment traps or in deep sea cores. Here we estimated CaCO3 precipitation rates in the surface water of the Red Sea from total alkalinity depletion along their axial flow using the water flux in the straits of Bab el Mandeb. The relative contribution of coral reefs and open sea plankton were calculated by fitting a Rayleigh distillation model to the increase in the strontium to calcium ratio. We estimate the net amount of CaCO3 precipitated in the Red Sea to be 7.3 ± 0.4·1010 kg·y−1 of which 80 ± 5% is by pelagic calcareous plankton and 20 ± 5% is by the flourishing coastal coral reefs. This estimate for pelagic calcification rate is up to 40% higher than published sedimentary CaCO3 accumulation rates for the region. The calcification rate of the Gulf of Aden was estimated by the Rayleigh model to be ∼1/2 of the Red Sea, and in the northwestern Indian Ocean, it was smaller than our detection limit. The results of this study suggest that variations of major ions on a basin scale may potentially help in assessing long-term effects of ocean acidification on carbonate deposition by marine organisms. PMID:25368148

  8. Basin-scale estimates of pelagic and coral reef calcification in the Red Sea and Western Indian Ocean.

    PubMed

    Steiner, Zvi; Erez, Jonathan; Shemesh, Aldo; Yam, Ruth; Katz, Amitai; Lazar, Boaz

    2014-11-18

    Basin-scale calcification rates are highly important in assessments of the global oceanic carbon cycle. Traditionally, such estimates were based on rates of sedimentation measured with sediment traps or in deep sea cores. Here we estimated CaCO3 precipitation rates in the surface water of the Red Sea from total alkalinity depletion along their axial flow using the water flux in the straits of Bab el Mandeb. The relative contribution of coral reefs and open sea plankton were calculated by fitting a Rayleigh distillation model to the increase in the strontium to calcium ratio. We estimate the net amount of CaCO3 precipitated in the Red Sea to be 7.3 ± 0.4·10(10) kg·y(-1) of which 80 ± 5% is by pelagic calcareous plankton and 20 ± 5% is by the flourishing coastal coral reefs. This estimate for pelagic calcification rate is up to 40% higher than published sedimentary CaCO3 accumulation rates for the region. The calcification rate of the Gulf of Aden was estimated by the Rayleigh model to be ∼1/2 of the Red Sea, and in the northwestern Indian Ocean, it was smaller than our detection limit. The results of this study suggest that variations of major ions on a basin scale may potentially help in assessing long-term effects of ocean acidification on carbonate deposition by marine organisms.

  9. The linkage between longitudinal sediment routing systems and basin types in the northern South China Sea in perspective of source-to-sink

    NASA Astrophysics Data System (ADS)

    Su, Ming; Hsiung, Kan-Hsi; Zhang, Cuimei; Xie, Xinong; Yu, Ho-Shing; Wang, Zhenfeng

    2015-11-01

    Using bathymetric and seismic data, this study describes the morpho-sedimentary features in Qiongdongnan basin and southwest Taiwan collision basin, northern South China Sea and reveals the linkages between sediment routing system and basin types. The modern Central Canyon in the Qiongdongnan basin is located along the rift margin, and subparallel to the shelf-break southeast of Hainan Island. The modern Central Canyon develops along the basin axis (i.e., Xisha Trough) and longitudinally transports sediments eastward which are mainly supplied by northern continental slope. The Penghu Canyon in the southwest Taiwan collision basin is located along the collision boundary parallel to the strike of the adjacent uplifted Taiwan orogen. The Penghu Canyon develops along the tilting basin axis transporting sediments longitudinally southward to the deep-sea basin and Manila Trench. The Penghu Canyon is supplied with sediments from both flank Kaoping and South China Sea slopes where tributary canyons and channels transport sediments down-slope and feed the axial canyon. The certain basin types may be occupied by particular styles of sediment routing system. By comparing the morpho-sedimentary features and basin characteristics associated with the modern Central Canyon to that of the Valencia Channel in NW Mediterranean Sea, the longitudinal sediment routing system in rift basin type can be determined. In contrast, the longitudinal sediment routing systems in collision setting can be represented by the comparable examples of Penghu Canyon in southwest Taiwan collision basin and Markham Canyon in western Solomon Sea. The rift type sediment routing system is characterized by an axial canyon with a single sediment supply from land drainage margin. In contrast, sediment routing system in collision type basins consists of an axial canyon and dual sediment supplies from flank adjacent slopes. The axial canyons in collision basins are more active than that of the rift basin due to

  10. Large-scale patterns of recent sedimentation along the Cayman Troughpull-apart basin, Caribbean Sea

    SciTech Connect

    Debalko, D.; Mann, P. )

    1990-05-01

    The North American-Caribbean plate boundary zone consists of a broad zone of active strike-slip deformation that extends 3,200 km from Middle America to the Lesser Antilles. An 1,100-km-long, 100-km-wide pull-apart basin the Cayman Trough is the dominant structural element of the submerged central part of the plate boundary zone between Jamaica and Honduras. In order to investigate large-scale patterns of recent sedimentation in a fully marine pull-apart setting, the authors surveyed a 90,000-km{sup 2} area along the southern edge of the Cayman Trough using SeaMARC II side-scan sonar, 3.5 KHz, and digital single-channel reflection techniques. These data allow them to divide the southern margin of the Cayman Trough pull-apart into three provinces of recent sedimentation: (1) an eastern terrigenous province characterized by straight short canyon systems (average 1-3 km wide and 10-15 km long) and associated small, lobate fans; canyon-fan systems are sourced by clastic spillover from filled borderland-type basins and by erosion of emergent fault-block islands; (2) a central carbonate province characterized by periplatform carbonate detritus fringing four isolated carbonate banks which collectively make up the Nicaraguan Rise; canyon systems (1-3 km wide, 15-80 km long) are highly meandering when unfaulted and straight when faulted; and (3) an eastern carbonate and terrigenous province characterized by both carbonate sediments shed off the easternmost bank of the Nicaraguan Rise bank and by terrigenous sediment derived from Jamaica.

  11. Physical and geoacoustic properties of surface sediments in the southwestern Ulleung Basin, East Sea of Korea

    NASA Astrophysics Data System (ADS)

    Kim, S.; Kim, D. C.; Lee, G.; Kim, S. P.; Bae, S.

    2012-12-01

    To investigate the physical and geoacoustic properties of surface sediments in the southwestern Ulleung Basin, East Sea of Korea, eighty-two piston cores and sixty-six box cores were analyzed for sediment texture (grain size, sand, silt and clay contents), physical properties (porosity, water content, bulk density, grain density and shear strength), and acoustic properties (compressional wave velocity and attenuation). We conducted mapping the distribution of sediment texture, each physical properties, and compressional wave velocity. According to the distribution map of sediment texture, the inner shelf area is consists of fine-grained sediments that are interpreted as recent sediments deposited under the present environment condition. Ulleung Basin also dominated fine-grained sediments consist of hemi-pelagic mud. On the mid-shelf, fine materials are mixed with fine-grained sediments and relict coarse sediments. Some part of the relict sediments on the mid-shelf were continuously reworked under the present environmental conditions forming the palimpsest sediments. The outer shelf area is composed of very coarse-grained sediments that are considered relict sediments deposited during the last glacial periods when the sea level was lower than the present. Based on geoacoustic property analyzed from this study, the study area is divided into five different geoacoustic provinces: (1) Province I is composed of muddy sediments that are directly affected by the Nakdong River discharge (1486 m/s, 8.1Φ, 1.32 g/cm3, and 80 %), (2) Province II is generally characterized by hemi-pelagic muds and partially mixed with intermittent sandy sediments originated from the outer shelf and upper slope (1495 m/s, 8.4Φ, 1.27 g/cm3, and 82 %), (3) Province III is comprised of muddy sand sediments that are corresponding to the boundary between recent sediments and relict sediments (1539 m/s, 5.8Φ, 1.52 g/cm3, and 69 %), (4) Province IV is dominated by coarse-grained relict sediments

  12. Weather types across the Caribbean basin and their relationship with rainfall and sea surface temperature

    NASA Astrophysics Data System (ADS)

    Moron, Vincent; Gouirand, Isabelle; Taylor, Michael

    2016-07-01

    Eight weather types (WTs) are computed over 98.75°W-56.25°W, 8.75°N-31.25°N using cluster analysis of daily low-level (925 hPa) winds and outgoing longwave radiation, without removing the mean annual cycle, by a k-means algorithm from 1979 to 2013. The WTs can be firstly interpreted as snapshots of the annual cycle with a clear distinction between 5 "wintertime" and 3 "summertime" WTs, which account together for 70 % of the total mean annual rainfall across the studied domain. The wintertime WTs occur mostly from late November to late April and are characterized by varying intensity and location of the North Atlantic subtropical high (NASH) and transient synoptic troughs along the northern edge of the domain. Large-scale subsidence dominates the whole basin but rainfall can occur over sections of the basin, especially on the windward shores of the troughs associated with the synoptic waves. The transition between wintertime and summertime WTs is rather abrupt, especially in May. One summertime WT (WT 4) is prevalent in summer, and almost exclusive around late July. It is characterized by strong NASH, fast Caribbean low level jet and rainfall mostly concentrated over the Caribbean Islands, the Florida Peninsula, the whole Central America and the tropical Eastern Pacific. The two remaining summertime WTs display widespread rainfall respectively from Central America to Bermuda (WT 5) and over the Eastern Caribbean (WT 6). Both WTs combine reduced regional scale subsidence and weaker Caribbean low-level jet relatively to WT 4. The relationships between WT frequency and El Niño Southern Oscillation (ENSO) events are broadly linear. Warm central and eastern ENSO events are associated with more WT 4 (less WT 5-6) during boreal summer and autumn (0) while this relationship is reversed during boreal summer (+1) for central events only. In boreal winter, the largest anomalies are observed for two WTs consistent with negative (WT 2) and positive (WT 8) phases of the

  13. Effects of neotectonic and sedimentary processes on the seafloor geomorphology of the Tekirdag Basin of the western Marmara Sea (Turkey)

    NASA Astrophysics Data System (ADS)

    Ergin, Mustafa; Yigit-Faridfathi, Füsun

    2010-05-01

    This study forms part of a project (TUBITAK YDABCAG 101Y071) with the main purpose of investigation of late Quaternary slope stability, sediment mass movements and turbidite formations in the tectonically active Tekirdag Basin and its margins from the western Marmara Sea. The results were also intended to relate to the major earthquakes and sea-level changes. During this project, in 2001 aboard the former R/V MTA Sismik-1, a total of 100 km seismic reflection profiles were obtained along three tracklines representing from shelf to slope to deep basin environments. A multichannel airgun seismic system and well-known methods and principles of seismic stratigraphy was used for interpretations. At 11 sites from 29 to 1111 m water depths gravity sediment cores were taken having 100 to 359 cm recoveries and textural and structural characteristics were determined using standard petrographic methods. The NEE-SWW directed seismic profile (TKD-01) which runs parallel to the North Anatolian Fault zone displayed syntectonic sedimentation with negative flower structure that increased in thickness toward the Ganos Fault and pinched out in the east. ENE section of this profile also bears structures of underwater landslides with slump facies. Seismic profile TKD-02 which crosses the Tekirdag Basin in WNW-ESE direction most likely displays major 3 fault segments of the NAF zone. Many faults and syntectonic sedimentation structure can be recognized on this profile. A morphological feature of a sediment wedge or former lowstand delta at the present shelf edge can be related to the effects of last sea-level change. Mounded and chaotic seismic reflection configurations which indicate channel and slope-front fill as well as slump facies are thought to reflect submarine slides and slumps. Other morphological features such as incised submarine valleys or channels running E-W direction are also present on this profile. The seismic profile (TKD-03) runs from NNW to SSE across the basin and

  14. Sea-level and tectonic control of middle to late Pleistocene turbidite systems in Santa Monica Basin, offshore California

    USGS Publications Warehouse

    Normark, W.R.; Piper, D.J.W.; Sliter, R.

    2006-01-01

    Small turbidite systems offshore from southern California provide an opportunity to track sediment from river source through the turbidity-current initiation process to ultimate deposition, and to evaluate the impact of changing sea level and tectonics. The Santa Monica Basin is almost a closed system for terrigenous sediment input, and is supplied principally from the Santa Clara River. The Hueneme fan is supplied directly by the river, whereas the smaller Mugu and Dume fans are nourished by southward longshore drift. This study of the Late Quaternary turbidite fill of the Santa Monica Basin uses a dense grid of high-resolution seismic-reflection profiles tied to new radiocarbon ages for Ocean Drilling Program (ODP) Site 1015 back to 32 ka. Over the last glacial cycle, sedimentation rates in the distal part of Santa Monica Basin averaged 2-3 mm yr-1, with increases at times of extreme relative sea-level lowstand. Coarser-grained mid-fan lobes prograded into the basin from the Hueneme, Mugu and Dume fans at times of rapid sea-level fall. These pulses of coarse-grained sediment resulted from river channel incision and delta cannibalization. During the extreme lowstand of the last glacial maximum, sediment delivery was concentrated on the Hueneme Fan, with mean depositional rates of up to 13 mm yr-1 on the mid- and upper fan. During the marine isotope stage (MIS) 2 transgression, enhanced rates of sedimentation of > 4 mm yr-1 occurred on the Mugu and Dume fans, as a result of distributary switching and southward littoral drift providing nourishment to these fan systems. Longer-term sediment delivery to Santa Monica Basin was controlled by tectonics. Prior to MIS 10, the Anacapa ridge blocked the southward discharge of the Santa Clara River into the Santa Monica Basin. The pattern and distribution of turbidite sedimentation was strongly controlled by sea level through the rate of supply of coarse sediment and the style of initiation of turbidity currents. These two

  15. Cyclone trends constrain monsoon variability during late Oligocene sea level highstands (Kachchh Basin, NW India)

    NASA Astrophysics Data System (ADS)

    Reuter, M.; Piller, W. E.; Harzhauser, M.; Kroh, A.

    2013-09-01

    Climate change has an unknown impact on tropical cyclones and the Asian monsoon. Herein we present a sequence of fossil shell beds from the shallow-marine Maniyara Fort Formation (Kachcch Basin) as a recorder of tropical cyclone activity along the NW Indian coast during the late Oligocene warming period (~ 27-24 Ma). Proxy data providing information about the atmospheric circulation dynamics over the Indian subcontinent at this time are important since it corresponds to a major climate reorganization in Asia that ends up with the establishment of the modern Asian monsoon system at the Oligocene-Miocene boundary. The vast shell concentrations are comprised of a mixture of parautochthonous and allochthonous assemblages indicating storm-generated sediment transport from deeper to shallow water during third-order sea level highstands. Three distinct skeletal assemblages were distinguished, each recording a relative storm wave base. (1) A shallow storm wave base is shown by nearshore molluscs, reef corals and Clypeaster echinoids; (2) an intermediate storm wave base depth is indicated by lepidocyclinid foraminifers, Eupatagus echinoids and corallinacean algae; and (3) a deep storm wave base is represented by an Amussiopecten bivalve-Schizaster echinoid assemblage. These wave base depth estimates were used for the reconstruction of long-term tropical storm intensity during the late Oligocene. The development and intensification of cyclones over the recent Arabian Sea is primarily limited by the atmospheric monsoon circulation and strength of the associated vertical wind shear. Therefore, since the topographic boundary conditions for the Indian monsoon already existed in the late Oligocene, the reconstructed long-term cyclone trends were interpreted to reflect monsoon variability during the initiation of the Asian monsoon system. Our results imply an active monsoon over the Eastern Tethys at ~ 26 Ma followed by a period of monsoon weakening during the peak of the late

  16. Seismic Velocity and Thickness of Sediments Beneath the Aleutian Basin, Bering Sea

    NASA Astrophysics Data System (ADS)

    Scheirer, D. S.; Barth, G. A.; Sliter, R. W.; Hart, P. E.; Childs, J. R.

    2014-12-01

    The thickness and seismic velocity structure of sediments of the Aleutian Basin were mapped during a 2011 multichannel seismic (MCS) cruise of the R/V Langseth. Combined with legacy MCS, sonobuoy, and scientific drilling data, the Langseth observations allowed us to study the history of sedimentation in this area. Semblance velocity analyses from common-depth-point gathers of the 8-km-long streamer data were conducted at-sea every 6.25 km. Post-cruise, these semblance analyses were refined and supplemented with new analyses where significant basement topography is present. The flat-lying nature of both the seafloor and the within-sediment reflectors allowed determination of interval velocity and thickness values with high precision using the Dix equation. Two prominent bottom-simulating reflections (BSRs) are common within the sediment column: a shallower one inferred to represent the base of gas hydrate stability, and a deeper one inferred to represent the diagenetic transformation from opal-A to opal-CT. This latter transition was reached by the one deep hole (Site 190, DSDP Leg19) drilled into the Aleutian Basin, where the lithologic contrast prevented further penetration. The gas hydrate BSR is associated with subvertical velocity-amplitude anomalies, and the opal A/CT transition is associated with a large decrease in reflector amplitudes beneath it, indicating the decrease in acoustic impedance contrasts associated with diagenetic dewatering. Seismic interval velocities range from 1600 m/sec at the top of the sediment column to 2800-3500 m/sec at its base. The largest step in interval velocity occurs at the opal A/CT transition. Interval velocities are laterally continuous over many tens of kilometers, and this continuity allows the generation of seismic travel-time vs. sediment thickness relationships across the basin. A second-degree polynomial relationship between time and thickness, developed by regression of all of the semblance velocity analyses from the

  17. Structural differences between the western and eastern Qiongdongnan Basin: evidence of Indochina block extrusion and South China Sea seafloor spreading

    NASA Astrophysics Data System (ADS)

    Zhang, Cuimei; Wang, Zhenfeng; Sun, Zhipeng; Sun, Zhen; Liu, Jianbao; Wang, Zhangwen

    2013-12-01

    Located at the intersection between a NW-trending slip system and NE-trending rift system in the northern South China Sea, the Qiongdongnan Basin provides key clues for us to understand the proposed extrusion of the Indochina Block along with Red River Fault Zone and extensional margins. In this paper we for the first time systematically reveal the striking structural differences between the western and eastern sector of the Qiongdongnan Basin. Influenced by the NW-trending slip faults, the western Qiongdongnan Basin developed E-W-trending faults, and was subsequently inverted at 30-21 Ma. The eastern sector was dominated by faults with NE orientation before 30 Ma, and thereafter with various orientations from NE, to EW and NW during the period 30-21 Ma; rifting display composite symmetric graben instead of the composite half graben or asymmetric graben in the west. The deep and thermal structures in turn are invoked to account for such deformation differences. The lithosphere of the eastern Qiongdongnan Basin is very hot and thinned because of mantle upwelling and heating, composite symmetric grabens formed and the faults varied with the basal plate boundary. However, the Southern and Northern Uplift area and middle of the central depression is located on normal lithosphere and formed half grabens or simple grabens. The lithosphere in the western sector is transitional from very hot to normal. Eventually, the Paleogene tectonic development of the Qiongdongnan Basin may be summarized into three stages with dominating influences, the retreat of the West Pacific subduction zone (44-36 Ma), slow Indochina block extrusion together with slab-pull of the Proto-South China Sea (36-30 Ma), rapid Indochina block extrusion together with the South China Sea seafloor spreading (30-21 Ma).

  18. Taxonomic study of the Pagurus forbesii "complex" (Crustacea: Decapoda: Paguridae). Description of Pagurus pseudosculptimanus sp. nov. from Alborán Sea (Southern Spain, Western Mediterranean Sea).

    PubMed

    Muñoz, J Enrique García; Cuesta, Jose A; Raso, J Enrique García

    2014-01-03

    Study of hermit crabs from Alboran Sea has allowed recognition of two different morphological forms under what had been understood as Pagurus forbesii. Based on morphological observations with various species of Pagurus, and molecular studies, a new species is described as P. pseudosculptimanus. An overview of species of Pagurus from the eastern Atlantic and Mediterranean Sea is provided.

  19. Identifying a Sea Breeze Circulation Pattern Over the Los Angeles Basin Using Airborne In Situ Carbon Dioxide Measurements

    NASA Astrophysics Data System (ADS)

    Brannan, A. L.; Schill, S.; Trousdell, J.; Heath, N.; Lefer, B. L.; Yang, M. M.; Bertram, T. H.

    2014-12-01

    The Los Angeles Basin in Southern California is an optimal location for a circulation study, due to its location between the Pacific Ocean to the west and the Santa Monica and San Gabriel mountain ranges to the east, as well as its booming metropolitan population. Sea breeze circulation carries air at low altitudes from coastal to inland regions, where the air rises and expands before returning back towards the coast at higher altitudes. As a result, relatively clean air is expected at low altitudes over coastal regions, but following the path of sea breeze circulation should increase the amount of anthropogenic influence. During the 2014 NASA Student Airborne Research Program, a highly modified DC-8 aircraft completed flights from June 23 to 25 in and around the LA Basin, including missed approaches at four local airports—Los Alamitos and Long Beach (coastal), Ontario and Riverside (inland). Because carbon dioxide (CO2) is chemically inert and well-suited as a conserved atmospheric tracer, the NASA Langley Atmospheric Vertical Observations of CO2 in the Earth's Troposphere (AVOCET) instrument was used to make airborne in situ carbon dioxide measurements. Combining measured wind speed and direction data from the aircraft with CO2 data shows that carbon dioxide can be used to trace the sea breeze circulation pattern of the Los Angeles basin.

  20. Evidence for local shifting of the main fault and changes in the structural setting, Kinarot basin, Dead Sea transform

    SciTech Connect

    Rotstein, Y.; Frieslander, U. ); Bartov, Y. )

    1992-03-01

    Two new high-resolution seismic reflection profiles from the Kinarot Valley, Dead Sea rift, analyzed with older conventional oil exploration profiles, throw light on the Quaternary evolution of the African-Arabian transform-type plate boundary in the area. The present en echelon main faults of the Dead Sea transform are observed in the seismic data as wide zones of deformation rather than as distinct fault planes. A similar zone of deformation is observed in the center of the Kinarot basin and may be associated with an extinct trace of the main fault. The Zemah structure, previously mapped and drilled, is shown by the new data to be an inactive anticline. Compression within the basin is suggested as being the result of motion along the now inactive main fault observed in the center of the basin. Compression and shortening started some 2 m.y. ago and ended late in the Quaternary as a result of changes in the geometry of the transform. At present the Kinarot basin is subsiding.

  1. Facies analysis, sea level history, and platform evolution of Jurassic Smackover Formation, Conecuh basin, Escambia County, Alabama

    SciTech Connect

    Esposito, R.A. Jr.; King, D.T. Jr.

    1987-09-01

    The Smackover Formation (Jurassic, Oxfordian) in the Conecuh basin, Escambia County, Alabama, is divided into six carbonate sedimentary facies. In approximate stratigraphic order, they are (1) intertidal algal mudstone, (2) basinal carbonate mudstone and calcareous shale, (3) graded slope packstone and wackestone, (4) Tubiphytes-bearing, slope debris-flow grainstone and packstone, (5) distal-ramp wackestone, and (6) shoal-produced oolitic grainstone. Facies correlation and synthesis, using 11 key drill cores, show that the Smackover platform was profoundly affected by two rapid sea level rises during the Oxfordian transgression, as well as the late Oxfordian regression. The first rapid rise drowned in the inherited Norphlet clastic ramp, including the Smackover intertidal algal mudstone (facies 1). Subsequently, a Tubiphytes-rimmed shelf developed and its bypass-margin slope deposits (facies 3 and 4) and coeval basinal facies (facies 2) prograded in the basin. The second rapid sea level rise drowned the rimmed shelf, creating a distally steepened ramp. Facies developed on the ramp were distal-ramp deposits (facies 5) and higher energy updip oolitic shoals (facies 6). The late Oxfordian rapid regression caused widespread progradation of the oolitic shoals and coeval sabkha facies of the overlying Buckner anhydrite.

  2. Possible connection between large volcanic eruptions and level rise episodes in the Dead Sea Basin

    NASA Astrophysics Data System (ADS)

    Bookman, R.; Filin, S.; Avni, Y.; Rosenfeld, D.; Marco, S.

    2014-12-01

    The June 1991 Pinatubo volcanic eruption perturbed the atmosphere, triggering short-term worldwide changes in climate. The following winter was anomalously wet in the Levant, with a ~2-meter increase in the Dead Sea level that created a morphological terrace along the lake's shore. Given the global effects of volcanogenic aerosols, we tested the hypothesis that the 1991-92 shore terrace is a modern analogue to the linkage between past volcanic eruptions and a sequence of shore terraces in the Dead Sea Basin. Analysis of precipitation series from Jerusalem showed a significant positive correlation between the Dust Veil Index (DVI) of the modern eruptions and annual rainfall. The DVI was found to explain nearly 50% of the variability in the annual rainfall, such that greater DVI means more rainfall. Other factors that may affect the annual rainfall in the region as the Southern Oscillation Index (SOI) and the North Atlantic oscillations (NAO) were incorporated along with the DVI in a linear multiple regression model. It was found that the NAO did not contribute anything except for increased noise, but the added SOI increased the explained variability of rainfall to more than 60%. Volcanic eruptions with a VEI of 6, as in the Pinatubo, occurred about once a century during the Holocene and the last glacial-interglacial cycle. This occurrence is similar to the frequency of shore terrace build-up during the Lake Lisan desiccation. Sixteen shore terraces, detected using airborne laser scanning data, were interpreted as indicating short-term level rises due to episodes of enhanced precipitation and runoff during the dramatic drop in Lake Lisan's (palaeo-Dead Sea) level at the end of the LGM. The terraces were compared with a time series of volcanogenic sulfate from the GISP2 record, and similar numbers of sulfate concentration peaks and terraces were found. Furthermore, a significant correlation was found between SO4 concentration peaks and the terraces heights. This

  3. Parascolymia (Scleractinia: Lobophylliidae) in the Central Paratethys Sea (Vienna Basin, Austria) and its possible biogeographic implications

    PubMed Central

    Reuter, Markus; Wiedl, Thomas; Piller, Werner E.

    2015-01-01

    Palaeobiogeographical and palaeodiversity patterns of scleractinian reef corals are generally biased due to uncertain taxonomy and a loss of taxonomic characters through dissolution and recrystallization of the skeletal aragonite in shallow marine limestones. Herein, we describe a fossil lobophylliid coral in mouldic preservation from the early middle Miocene Leitha Limestone of the Central Paratethys Sea (Vienna Basin, Austria). By using grey-scale image inversion and silicone rubber casts for the visualization of the original skeletal anatomy and the detection of distinct micromorphological characters (i.e. shape of septal teeth, granulation of septocostae) Parascolymia bracherti has been identified as a new species in spite of the dissolved skeleton. In the recent era, Parascolymia like all Lobophylliidae is restricted to the Indo-Pacific region, where it is represented by a single species. The new species proves the genus also in the Miocene Mediterranean reef coral province. A review of the spatio-temporal relationships of fossil corals related to Parascolymia indicates that the genus was probably rooted in the Eastern Atlantic‒Western Tethys region during the Paleocene to Eocene and reached the Indo-Pacific region not before the Oligocene. The revealed palaeobiogeographical pattern shows an obvious congruence with that of Acropora and tridacnine bivalves reflecting a gradual equatorwards retreat of the marine biodiversity center parallel to the Cenozoic climate deterioration. PMID:26201071

  4. Assessment of big floods in the Eastern Black Sea Basin of Turkey.

    PubMed

    Yüksek, Ömer; Kankal, Murat; Üçüncü, Osman

    2013-01-01

    In this study, general knowledge and some details of the floods in Eastern Black Sea Basin of Turkey are presented. Brief hydro-meteorological analysis of selected nine floods and detailed analysis of the greatest flood are given. In the studied area, 51 big floods have taken place between 1955-2005 years, causing 258 deaths and nearly US $500,000,000 of damage. Most of the floods have occurred in June, July and August. It is concluded that especially for the rainstorms that have caused significantly damages, the return periods of the rainfall heights and resultant flood discharges have gone up to 250 and 500 years, respectively. A general agreement is observed between the return periods of rains and resultant floods. It is concluded that there has been no significant climate change to cause increases in flood harms. The most important human factors to increase the damage are determined as wrong and illegal land use, deforestation and wrong urbanization and settlement, psychological and technical factors. Some structural and non-structural measures to mitigate flood damages are also included in the paper. Structural measures include dykes and flood levees. Main non-structural measures include flood warning system, modification of land use, watershed management and improvement, flood insurance, organization of flood management studies, coordination between related institutions and education of the people and informing of the stakeholders.

  5. Parascolymia (Scleractinia: Lobophylliidae) in the Central Paratethys Sea (Vienna Basin, Austria) and its possible biogeographic implications.

    PubMed

    Reuter, Markus; Wiedl, Thomas; Piller, Werner E

    2015-01-01

    Palaeobiogeographical and palaeodiversity patterns of scleractinian reef corals are generally biased due to uncertain taxonomy and a loss of taxonomic characters through dissolution and recrystallization of the skeletal aragonite in shallow marine limestones. Herein, we describe a fossil lobophylliid coral in mouldic preservation from the early middle Miocene Leitha Limestone of the Central Paratethys Sea (Vienna Basin, Austria). By using grey-scale image inversion and silicone rubber casts for the visualization of the original skeletal anatomy and the detection of distinct micromorphological characters (i.e. shape of septal teeth, granulation of septocostae) Parascolymia bracherti has been identified as a new species in spite of the dissolved skeleton. In the recent era, Parascolymia like all Lobophylliidae is restricted to the Indo-Pacific region, where it is represented by a single species. The new species proves the genus also in the Miocene Mediterranean reef coral province. A review of the spatio-temporal relationships of fossil corals related to Parascolymia indicates that the genus was probably rooted in the Eastern Atlantic‒Western Tethys region during the Paleocene to Eocene and reached the Indo-Pacific region not before the Oligocene. The revealed palaeobiogeographical pattern shows an obvious congruence with that of Acropora and tridacnine bivalves reflecting a gradual equatorwards retreat of the marine biodiversity center parallel to the Cenozoic climate deterioration.

  6. Size distribution of absorbing and fluorescing DOM in Beaufort Sea, Canada Basin

    NASA Astrophysics Data System (ADS)

    Gao, Zhiyuan; Guéguen, Céline

    2017-03-01

    The molecular weight (MW) of dissolved organic matter (DOM) is considered as an important factor affecting the bioavailability of organic matter and associated chemical species. Colored DOM (CDOM) MW distribution was determined, for the first time, in the Beaufort Sea (Canada Basin) by asymmetrical flow field-flow fractionation (AF4) coupled with online diode array ultra violet-visible photometer and offline fluorescence detectors. The apparent MW ranged from 1.07 to 1.45 kDa, congruent with previous studies using high performance size exclusion chromatography and tangential flow filtration. Interestingly, a minimum in MW was associated with the Pacific Summer Waters (PSW), while higher MW was associated with the Pacific Winter Waters (PWW). The Arctic Intermediate Waters (AIW) did not show any significant change in MW and fluorescence intensities distribution between stations, suggesting homogeneous DOM composition in deep waters. Three fluorescence components including two humic-like components and one protein-like component were PARAFAC-validated. With the increase of MW, protein-like fluorescence component became more dominant while the majority remained as marine/microbially derived humic-like components. Overall, it is concluded that water mass origin influenced DOM MW distribution in the Arctic Ocean.

  7. Fluorine in the soils of the White Sea Basin and bioindication of pollution.

    PubMed

    Evdokimova, G A

    2001-01-01

    Assessment of the pollution level of soils and vegetation by fluorine and heavy metals and also of the state of the soil microflora in the impact zone of Kandalaksha aluminium factory is discussed. The significant pollution of natural media by fluorine in the basin of the White Sea is established. Concentration of the total fluorine in the organogenic horizon of the Al-Fe-humus podzol soil at a distance of 20 km in the northern direction from the source of emission exceeds the background level by a factor of 3. In the epicentre of emission the amount of total fluorine in the soil exceeds the background level by a factor of 7-8 (Tolerable Amount: 4-5-fold). It is noted that the soil becomes more alkaline under the influence of fluorine and the increased content of chromium along the soil profile exceeds PC by a factor of 3 in the vicinity of the factory. The differences in the dimensions of bacterial and fungi biomass along the gradient of pollution were not revealed in the impact zone. But the changes in the taxonomic structure of fungi and in the level of their domination along the gradient of pollution were estimated. Floristic composition of the soil algae is represented mainly by unicellular green algae with Chlamydomonas elliptica and Bracteacoccus minor predominating.

  8. Geologic evolution and aspects of the petroleum geology of the northern East China Sea shelf basin

    SciTech Connect

    Lee, G.H.; Kim, B.Y.; Shin, K.S.; Sunwoo, D.

    2006-02-15

    Analysis of multichannel seismic reflection profiles reveals that the northern East China Sea shelf basin experienced two phases of rifting, followed by regional subsidence. The initial rifting in the Late Cretaceous created a series of grabens and half grabens, filled by alluvial and fluviolacustrine deposits. Regional uplift and folding (Yuquan movement) in the late Eocene-early Oligocene terminated the initial rifting. Rifting resumed in the early Oligocene, while alluvial and fluviolacustrine deposition continued to prevail. A second phase of uplift in the early Miocene terminated the rifting, marking the transition to the postrift phase. The early postrift phase (early Miocene-late Miocene) is characterized by regional subsidence and westward and northwestward marine transgression. Inversion (Longjing movement) in the late Miocene interrupted the postrift subsidence, resulting in an extensive thrust-fold belt in the eastern part of the area. The entire area entered a stage of regional subsidence again and has become a broad continental shelf. Source rocks include synrift lacustrine facies, fluvial shales, and coal beds. Synrift fluvial, lacustrine, and deltaic deposits, postrift littoral and/or shallow-marine sandstones, and fractured basement have the potential to provide reservoirs. Various types of hydrocarbon traps (e.g., faulted anticlines, overthrusts, rollover anticlines, faults, unconformity traps, combination structural-stratigraphic traps, weathered basement, and stratigraphic traps) are recognized, but many of these traps have not been tested.

  9. Geoacoustic model of surface sediments in the southwestern Ulleung basin, the East Sea of Korea

    NASA Astrophysics Data System (ADS)

    Kim, S. H.; Kim, D. C.; Lee, G. S.; Kim, S. P.; Bae, S. H.

    2012-04-01

    To realization of geoacoustic model in the southwestern Ulleung basin, the East Sea of Korea, eighty-two piston core samples and sixty-six box core samples were collected. Sediment texture (mean grain size and sand, silt, and clay contents), physical properties (porosity, water content, bulk density, and grain density), and acoustic properties (compressional wave velocity and attenuation) were measured using surface sediments below 40 cm from the surface. As the results, the study area is divided into five sub-areas based on acoustic property of sediments: (1) Area I is composed of muddy sediments that affected directly by the Nakdong River discharge. The velocity is almost 1490 m/s. (2) Area II is generally characterized by hemi-pelagic muds and partially mixed with intermittent sandy sediments originated from the outer shelf and upper slope. The velocity approximately ranges from 1490 to 1500 m/s. (3) Area III is comprised of muddy sand sediments that are corresponds to the boundary between recent sediments and relict sediments. The velocity ranges from 1500 to 1600 m/s. (4) Area IV is dominated by coarse-grained relict sediments. The velocity ranges from 1600 to 1700 m/s. And (5) Area V consists of very coarser sediments. The velocity is higher than 1700 m/s. The sediment velocity generally decreases with increasing porosity or decreasing mean grain size and bulk density.

  10. Was the Aleutian basin more enclosed. Its deep oxygen deficient, and the geothermal gradient steepened in the middle Tertiary Implications for the petroleum potential of the Bering Sea

    SciTech Connect

    Scholl, D.W.; Stevenson, A. )

    1990-06-01

    Circulation of north Pacific waters through the Aleutian Basin of the deep Bering Sea (3,500-4,000 m) is presently vigorous and affects all depths. Energetic currents enter and exit the Bering Sea via deepwater (1,000-4,000 m) passes in the Aleutian Ridge. But geologic evidence suggests that in the middle Tertiary (or earlier), the basin was possibly stagnant or poorly ventilated. A sequence of undeformed sedimentary deposits typically more than 4 km thick underlies the south-central bathymetric deep of the basin. The basinal sequence includes hundreds of velocity-amplitude anomalies (VAMPs), which are deep-water bright spots associated with underlying velocity pull-downs. The VAMPs are thought to record the pooling of thermogenic gas at subbottom depths of 800 to 1,000 m. Because VAMPs are largely confined to the basin's bathymetric low, subsurface source beds that supplied the gases must be located here. Favorable preservation of organic matter over the basin deep may reflect a former oxygen-poor bottom-water environment. Tectonic reconstructions indicate that prior to the middle Tertiary a more laterally continuous Aleutian Ridge restricted circulation with the north Pacific, a circumstance that would have favored incomplete deep basin ventilation. New information concerning the paleoceanographic history of the Bering Sea, the prospect that organic-rich source beds have been deposited, and the likelihood that an episode of early Tertiary backarc spreading enhanced the basin's geothermal gradient, combine to improve the petroleum potential of the Aleutian basin.

  11. Changes in ventilation of the Mediterranean Sea during the past 25 year

    NASA Astrophysics Data System (ADS)

    Schneider, A.; Tanhua, T.; Roether, W.; Steinfeldt, R.

    2014-01-01

    Significant changes in the overturning circulation of the Mediterranean Sea has been observed during the last few decades, the most prominent phenomena being the Eastern Mediterranean Transient (EMT) in the early 1990s and the Western Mediterranean Transition (WMT) during the mid-2000s. During both of these events unusually large amounts of deep water were formed, and in the case of the EMT, the deep water formation area shifted from the Adriatic to the Aegean Sea. Here we synthesize a unique collection of transient tracer (CFC-12, SF6 and tritium) data from nine cruises conducted between 1987 and 2011 and use these data to determine temporal variability of Mediterranean ventilation. We also discuss biases and technical problems with transient tracer-based ages arising from their different input histories over time; particularly in the case of time-dependent ventilation. We observe a period of low ventilation in the deep eastern (Levantine) basin after it was ventilated by the EMT so that the age of the deep water is increasing with time. In the Ionian Sea, on the other hand, we see evidence of increased ventilation after year 2001, indicating the restarted deep water formation in the Adriatic Sea. This is also reflected in the increasing age of the Cretan Sea deep water and decreasing age of Adriatic Sea deep water since the end of the 1980s. In the western Mediterranean deep basin we see the massive input of recently ventilated waters during the WMT. This signal is not yet apparent in the Tyrrhenian Sea, where the ventilation seems to be fairly constant since the EMT. Also the western Alboran Sea does not show any temporal trends in ventilation.

  12. Propagated rifting in the Southwest Sub-basin, South China Sea: Insights from 3D analogue modeling

    NASA Astrophysics Data System (ADS)

    Ding, Weiwei; Li, Jiabiao

    2015-04-01

    Most of earth scientists agree that the South China Sea is a rifted marginal sea in the western Pacific. How and when the South China Sea rifted has long been a puzzling question and still debated, especially in the Southwest Sub-basin (SWSB). Analog modeling remains one of the useful tools for testing rift model and process. Here we present and discuss a series of analog modeling experiments designed to investigate the rifting process of the SWSB. Convincing geophysical data were compiled to provide truthful constraints to test the experimental results and interpretations. The results show that rigid tectonic blocks existed in the continental margin, such as the Zhongsha Islands and the Reed Bank, and played an important role in shaping up the continent-ocean boundary (COB) and the coupling between the crust and mantle. Our data suggest that the initial thermal condition and rheologial stratification of the lithosphere under the South China Sea controlled the rifting process of the SWSB. The first-stage seafloor spreading has weakened the lithosphere surrounding the East Sub-basin, and the extension was centered on the deep troughs between the rigid blocks. Rifting bagan in these deep troughs in the east part of the SWSB, and the break-up occurred in localized areas between the rigid blocks. The V-shaped configuration of the SWSB also argues for a propagated rifting model.

  13. BASINS

    EPA Pesticide Factsheets

    Better Assessment Science Integrating Point and Nonpoint Sources (BASINS) is a multipurpose environmental analysis system designed to help regional, state, and local agencies perform watershed- and water quality-based studies.

  14. Cenozoic evolution of the Pamir plateau recorded in surrounding basins, implications on Asian climate and land-sea distribution

    NASA Astrophysics Data System (ADS)

    Dupont-Nivet, Guillaume; Yang, Wei; Blayney, Tamsin; Proust, Jean-Noel; Guo, Zhaojie; Grothe, Arjen; Mandic, Oleg; Fionori, Chiara; Bougeois, Laurie; Najman, Yanina

    2015-04-01

    The Cenozoic Pamir orogen formed in response to the India-Asia collision. Existing datasets shows that the range grew since ca. 25 Ma, however the early Cenozoic history remains particularly enigmatic. In that peculiar period, global climate changed from greenhouse to icehouse, the proto-Paratethys sea retreated out of Asia and continental aridification as well as monsoons established over Asia. These environmental changes are held responsible for major floral and faunal crises including the emergence of plant communities and the dispersion of key mammal groups from Asia onto other continents. However, the causal relationships between these events remains to be established because of the lack of accurate age constraints on their geological records. Here, we provide well-dated stratigraphic records using magneto- and bio-stratigraphy from the basins surrounding the Pamir. Southeast of the Pamir, along the Kunlun Shan into the southwestern Tarim Basin, Eocene marine deposits are continuously overlain by 41 to 15 Ma continental redbeds themselves overlain by conglomerates in a classic foreland sequence with upward increasing grain-size, accumulation rates and provenance proximity. However, North of the Pamir along the southwestern Tian Shan and West of the Pamir into the Afghan-Tadjik Basin, the entire Oligocene period appears to be missing from the record between the last marine and the first continental sediments dated to the Early Miocene. This supports a simple basin evolution model in response to initial Pamir indentation with Eocene foreland basin activation in the Southeast related to the Kunlun Shan northward thrusting, followed much later by early Miocene activation of the northern foreland basin related to the southwestern Tian Shan overthrusting. The coeval activation of a lithospheric right-lateral strike-slip system along the Pamir/Tarim boundary may have enabled to transfer deformation from the India-Asia collision zone to the Tian Shan and possibly the

  15. Constraining back-arc basin formation in the eastern Coral Sea: preliminary results from the ECOSAT voyage

    NASA Astrophysics Data System (ADS)

    Seton, M.; Williams, S.; Mortimer, N. N.; Meffre, S.; Moore, J.; Micklethwaite, S.; Zahirovic, S.

    2013-12-01

    The eastern Coral Sea region is an underexplored area at the northeastern corner of the Australian plate, where long-lived interaction between the Pacific and Australian plate boundaries has resulted in an intricate assemblage of deep oceanic basins and ridges, continental fragments and volcanic products. A paucity of marine geophysical and geological data from this complex region has resulted in the lack of a clear conceptual framework to describe its formation, ultimately affecting our understanding of the connection between the plate boundaries of the SW Pacific and SE Asia. In particular, the tectonic relationship between two back-arc basins, the Santa Cruz and d'Entrecasteaux Basins, and the South Rennell Trough, has yet to be resolved. In October-November, 2012, we collected 6,200 km of marine magnetic, 6,800 km of gravity and over 13,600 km2 of swath bathymetry data from the eastern Coral Sea onboard the RV Southern Surveyor. A complementary dredging program yielded useful samples from 14 seafloor sites. Our preliminary geochemical interpretation of the dredge samples obtained from the South Rennell Trough reveal volcanic rocks resembling MORB or BABB-type basalts, similar in composition to the recently re-analysed and dated ORSTOM dredges from the area that yielded ~28 Ma MORB-like basalts. Swath bathymetry profiles from the Santa Cruz Basin reveal that the South Rennell Trough extends into this basin, with seafloor spreading fabric being parallel to the trough. Preliminary analysis of the three full and four partial new magnetic anomaly profiles across the Santa Cruz Basin, coupled with limited existing profiles, reveals that the basin may have formed between Chrons 13-18 (~32-38 Ma), with an extinct spreading ridge along the inferred continuation of the South Rennell Trough, consistent with ORSTOM age dates. Our results suggest that the South Rennell Trough is an extinct southwestward propagating spreading ridge, which may have initiated along a pre

  16. Palaeoenvironment and its control on the formation of Miocene marine source rocks in the Qiongdongnan Basin, northern South China Sea.

    PubMed

    Li, Wenhao; Zhang, Zhihuan; Wang, Weiming; Lu, Shuangfang; Li, Youchuan; Fu, Ning

    2014-01-01

    The main factors of the developmental environment of marine source rocks in continental margin basins have their specificality. This realization, in return, has led to the recognition that the developmental environment and pattern of marine source rocks, especially for the source rocks in continental margin basins, are still controversial or poorly understood. Through the analysis of the trace elements and maceral data, the developmental environment of Miocene marine source rocks in the Qiongdongnan Basin is reconstructed, and the developmental patterns of the Miocene marine source rocks are established. This paper attempts to reveal the hydrocarbon potential of the Miocene marine source rocks in different environment and speculate the quality of source rocks in bathyal region of the continental slope without exploratory well. Our results highlight the palaeoenvironment and its control on the formation of Miocene marine source rocks in the Qiongdongnan Basin of the northern South China Sea and speculate the hydrocarbon potential of the source rocks in the bathyal region. This study provides a window for better understanding the main factors influencing the marine source rocks in the continental margin basins, including productivity, preservation conditions, and the input of terrestrial organic matter.

  17. Palaeoenvironment and Its Control on the Formation of Miocene Marine Source Rocks in the Qiongdongnan Basin, Northern South China Sea

    PubMed Central

    Li, Wenhao; Zhang, Zhihuan; Wang, Weiming; Lu, Shuangfang; Li, Youchuan; Fu, Ning

    2014-01-01

    The main factors of the developmental environment of marine source rocks in continental margin basins have their specificality. This realization, in return, has led to the recognition that the developmental environment and pattern of marine source rocks, especially for the source rocks in continental margin basins, are still controversial or poorly understood. Through the analysis of the trace elements and maceral data, the developmental environment of Miocene marine source rocks in the Qiongdongnan Basin is reconstructed, and the developmental patterns of the Miocene marine source rocks are established. This paper attempts to reveal the hydrocarbon potential of the Miocene marine source rocks in different environment and speculate the quality of source rocks in bathyal region of the continental slope without exploratory well. Our results highlight the palaeoenvironment and its control on the formation of Miocene marine source rocks in the Qiongdongnan Basin of the northern South China Sea and speculate the hydrocarbon potential of the source rocks in the bathyal region. This study provides a window for better understanding the main factors influencing the marine source rocks in the continental margin basins, including productivity, preservation conditions, and the input of terrestrial organic matter. PMID:25401132

  18. Eustatic and climatic control on the Upper Muschelkalk Sea (late Anisian/Ladinian) in the Central European Basin

    NASA Astrophysics Data System (ADS)

    Franz, M.; Kaiser, S. I.; Fischer, J.; Heunisch, C.; Kustatscher, E.; Luppold, F. W.; Berner, U.; Röhling, H.-G.

    2015-12-01

    The Upper Muschelkalk in the Central European Basin (CEB) is a key example of eustatic and climatic controls on inland seas. The late Anisian rapid transgression from Tethyan waters culminated in a large semi-enclosed inland sea stretching across the CEB. Subsequently, the slow but successive retreat in the early Ladinian resulted in a small remnant sea. The pronounced stratal pattern architectures are translated into a framework of 3rd- and 4th-order T-R sequences. The latest Illyrian 3rd-order maximum flooding surface corresponds to maximum abundances of carbonates and marine phytoplankton. An euryhaline marine ecology is indicated by prasinophycean algae dominating over acritarchs and δ18OP values of 18.9-22.4‰ VSMOW corresponding to Tethyan references. During the 3rd-order regressive phase successive freshening up to hyposaline conditions is indicated by up to 3‰ depleted δ18OP values, shifts to more radiogenic 87Sr/86Sr ratios and maximum abundances of terrestrial palynomorphs. Likewise, 4th-order T-R sequences are constrained by commutated stratal pattern architectures, palynofacies and geochemistry. The favourable correlation of middle Triassic 3rd-order sequences of Tethyan and peri-Tethyan basins demonstrate the principle control of circum-Tethyan eustatic cycles. 4th-order sequences are evident and, although not yet correlatable in detail, indicate 106-year scale eustatic cycles which may be attributed to glacioeustatic sea-level changes. The subordinated control of arid to semiarid low latitude and semihumid to humid temperate mid latitude climates affected the Upper Muschelkalk Sea in particular during 4th-order sea-level lowstands. Substantial fresh water input from Scandinavian sources caused temporal stratification leading to stagnant bottom waters and/or sediments as indicated by palynofacies and U/Th and Ni/Co redox indices. The herein reconstructed middle Triassic zonal climates are in agreement to previously published Late Triassic zonal

  19. The tectonic framework of a complex pull-apart basin: Seismic reflection observations in the Sea of Galilee, Dead Sea transform

    USGS Publications Warehouse

    Hurwitz, S.; Garfunkel, Z.; Ben-Gai, Y.; Reznikov, M.; Rotstein, Y.; Gvirtzman, H.

    2002-01-01

    A multi-channel seismic reflection survey consisting of 20 lines with a total length of 180 km was conducted in the Sea of Galilee. The data provide new insights into the Pliocene-Quaternary evolution of the Kinarot-Beit-Shean pull-apart basin (KBSB) along the Dead Sea transform. Two distinct zones are defined beneath the lake: (1) a graben that underlies most of the lake, bounded by steep north-south longitudinal strike-slip faults and (2) shallow pre-rift units underlying the northwestern wider part of the lake. We suggest that before approximately 4 Ma, the KBSB grew due to northward movement of the Korazim Plateau and by crustal stretching along the rift axis. Since the Pliocene (??? 4 Ma), lateral slip has been transferred from the southern segment of the basin's western marginal fault to normal faults in the Galilee, and to the eastern margin of the Korazim Plateau by the newly formed, Almagor fault, which makes a restraining bend along the transform. N-S lithospheric stretching below the KBSB has diminished and the Korazim Plateau has changed from being a detached block to a compressional saddle. A phase of rapid subsidence, and formation of a half-graben structure in the northern part of the basin approximately 1 Ma ago was coeval with major deformation in areas adjacent to the KBSB, indicating major reorganization of the plate boundary in the region. Currently, most transform motions are probably taken up along a single fault on the eastern side of the KBSB, implying that the main trough under the Sea of Galilee is in a late stage of growth as a pull-apart. ?? 2002 Elsevier Science B.V. All rights reserved.

  20. Development of Tertiary Basins of SE Asia from the South China Sea to the Andaman Sea region ; a comparative view on structure and timing

    NASA Astrophysics Data System (ADS)

    Pubellier, Manuel; Sautter, Benjamin

    2016-04-01

    Basins of SE Asia have developed since the end of Cretaceous times to the detriment of a Mesozoic andean arc which surrounded Sundaland. The arc was broader in the Eastern part along the Pacific Subduction Zone including theSouth China Sea (SCS), than in the Western part along the Sumatra Subduction Zone (Myanmar, Andaman Sea (AS), Malay Peninsula). By the end of the Upper Cretaceous, this arc died out and a widespread rifting with astonishing resemblances started in the whole Sundaland. We compare and discuss the basins similarities and differences in structure and timing between the two sides. A relaxation stage is evidenced in Western Sunda, represented by poorly exposed Late Cretaceous red beds filling the pre-existing morphostructures without clear fault-controlled basins. These deposits are also observed on seismic data offshore in the Gulf of Thailand and AS). On the opposite side along the Chinese margin, thick molasse-type deposits of Late Cretaceous age are on the contrary well expressed offshore and restricted to narrow valleys, indicating that stretching had already begun. There, the Paleogene is marked by strong extension with large crustal blocks rotated by often counter-regional normal faults creating half grabens. Crust was extended and extremely thinned particularly around the SCS. Basins reached the spreading stage in the Celebes Sea, the North Makassar basin and the SCS. On the western side, this period corresponds to narrow deep grabens (e.g. Mergui basins and part of western Malacca) with continental deposits, meaning that the stretching was localized. There, thinning of the crust took place during the Oligocene up to the Middle Miocene where large basins develop mostly to the outer edges of the Yenshanian Arc. Extension resumed in the Pliocene with the opening of the Andaman basin in an even more external position. To the eastern side the uppermost Miocene and the Pliocene were marked mostly by a deepening of the margins and the SCS ocean

  1. An adjusted one year sea surface heat and water budget for the Northwestern Mediterranean basin

    NASA Astrophysics Data System (ADS)

    Caniaux, Guy; Prieur, Louis; Giordani, Hervé

    2015-04-01

    The problem of heat and salt budget closure is an important subject in operational and research oceanography. The closure depends crucially on surface fluxes, as they are one of the most important processes in terms of the evolution of the heat and salt content in the oceanic top layers. However, in this problem, two points have to be considered. First, surface fluxes are affected by a variety of errors: those associated with the algorithms used for computing the turbulent fluxes, those due to the data used as input of bulk algorithms and the errors associated with the time and space resolution of the fluxes themselves. The second problem is that no surface flux dataset exists, that can be used as the truth, or as a reference, i.e. that can be used for closing observed heat and water budgets at various time and space scales. Here we address the question of adjusting surface heat and water fluxes so that they are in agreement with the evolution of the thermal and salt contents deduced from the extended dataset collected during the HyMex campaigns. These experiments were conducted in the North-western Mediterranean basin in 2012 and 2013. The method is based: (1) on the one-dimensional column modelling of the experimental area, by solving specific temperature and salinity equations and (2) on the optimization of adjustable coefficients with a genetic algorithm. The surface forcings, calculated from a mix of satellite retrievals, in-situ data, numerical weather prediction model observables and a bulk algorithm are also adjusted with the genetic algorithm. Finally, the adjusted fluxes allows to simulate the domain average sea surface temperature and salinity with errors less than 0.2 percent (or 0.03°C) and 0.08 percent (or 0.03 psu) respectively over one year. The adjusted fluxes are finally compared with various NWP models over the North-western Mediterranean basin and also locally with fluxes estimated at a mooring site (LION buoy).

  2. Distribution and species diversity of deep-sea nematodes in the Venezuela Basin

    NASA Astrophysics Data System (ADS)

    Tietjen, John H.

    1984-02-01

    In three sedimentary regions in the deep (>3400 m) Venezuela Basin, nematode abundance and dry weight biomass (ean ±1 S.E.) were higher in hemipelagic sediments (94 ± 1.5 individuals, 88 ± 2.5 μg per 10 cm -2) than in pelagic (67 ± 3 individuals, 32 ±33 μg per 10 cm -2) or turbidite (36 ± 3 individuals, 30 ± 3 μg per 10 cm -2) sediments. Abundance of nematodes appears to be at least partially related to geographic position within the basin; hemipelagic sediments lie closer to an area of elevated surface production near the Lesser Antilles than do the pelagic or turbidite sediments. Abundance of nematodes is also directly correlated with macrofauna abundance and presence of sedimentary lipids. Normal hierarchical classification indicates the presence of two faunal groups in the sediments: a 'sand' fauna in coarser pelagic sediments (median grain size, 65 μm) and a 'silt-clay' fauna in the finer hemipelagic and turbidite sediments (median grain size in both, 0.65 μm). Animals among the two faunal groups differ mostly in their feeding morphology: selective deposit feeding species, unable to utilize large, pelagically derived particles (mainly foraminiferan tests) are more abundant in finer hemipelagic and turbidite sediments, whereas species capable of rasping food particles off large sedimentary particles (epistrate feeders) are more abundant in pelagic sands than in finer sediments. Species diversity is higher in the hemipelagic than turbidite and pelagic sediments. Two reasons postulated for this are (1) the possible input of relatively fresh, surface-derived organic matter that might permit a large number of species to exist in hemipelagic sediments than in the other two, and (2) an optimally heterogeneous grain size distribution that might allow the species to coexist equitably. All three sediments support more diverse nematode assemblages than those in the North Carolina slope region, probably reflecting the greater physical stability of the abyssal

  3. Feedbacks of sedimentation on crustal heat flow - New insights from the Vøring Basin, Norwegian Sea

    NASA Astrophysics Data System (ADS)

    Theissen, S.; Ruepke, L. H.

    2009-04-01

    Information on the nature and origin of rift basins is preserved in the presently observed stratigraphy. Basin modeling aims at recovering this information with the goal of quantifying a basin's structural and thermal evolution. Decompaction and backstripping analysis is a classic and still popular approach to basin reconstruction [Steckler and Watts, 1978]. The total and tectonic subsidences, as well as sedimentation rates are calculated by the consecutive decompaction and removal of individual layers. The thermal history has to be computed separately using forward thermal models. An alternative is coupled forward modeling, where the structural and thermal history is computed simultaneously. A key difference between these reconstruction methods is that feedbacks of sedimentation on crustal heat flow are often neglected in backstripping methods. In this work we use the coupled basin modeling approach presented by Rüpke et al. [2008] to quantify some of the feedbacks between sedimentation and heat flow and to explore the differences between both reconstruction approaches in a case study from the Vøring Basin, Norwegian Sea. In a series of synthetic model runs we have reviewed the effects of sedimentation on basement heat flow. These example calculations clearly confirm the well-known blanketing effect of sedimentation and show that it is largest for high sedimentation rates. Recovery of sedimentation rates from the stratigraphy is, however, not straightforward. Decompaction-based methods may systematically underestimate sedimentation rates as sediment thickness is assumed to not change/thin during stretching. We present a new method for computing sedimentation rates based on forward modeling and demonstrate the differences between both methods in terms of rates and thermal feedbacks in a reconstruction of the Vøring basin (Euromargin transect 2). We find that sedimentation rates are systematically higher in forward models and heat flow is clearly depressed during

  4. Deep sea three component magnetic survey using ROV in the hydrothermal vent of the Lau Basin

    NASA Astrophysics Data System (ADS)

    Kim, C.; Park, C.

    2011-12-01

    We conducted magnetic survey at Apr., 2011 in the western slope of the caldera of TA25, the Lau Basin, the southwestern Pacific using IBRV(Ice Breaker Research Vessel) ARAON of KORDI(Korea Ocean Research and Development Institute), ROV(Remotely Operated Vehicle) of Oceaneering Co. and three component magnetometer(Fig. 1,Fig. 2). The deep-sea three component magnetic survey lines are the 13 N-S lines(100 m spacing) and the 2 E-W lines(Fig. 2). The depth ranges of the survey area are from about 900 m to 1200 m, below sea level. For the magnetic survey, the magnetometer sensor and the data logger was attached with the upper part and lower part of ROV, respectively(Fig. 2). We wanted to make the distance between the magnetometer sensor and ROV over 2 m long to reduce the noise effect of ROV. But, for the safe of deployment and recovery of ROV, the distance between the magnetometer sensor and ROV was 126 cm(Fig. 2). In the magnetic survey, ROV followed the planning tracks at 25~30 m above seafloor using the altimeter and USBL(Ultra Short Base Line) of ROV. IBRV ARAON accompanied ROV on the magnetic survey. The three component magnetometer measure the X(North), Y(East) and Z(Vertical) vector components of a magnetic field. A motion sensor(Oxtans) provided us the data of pitch, roll, yaw for the correction of the magnetic data to the motion of ROV. The data of the magnetometer sensor and the motion sensor were recorded on a notebook through the optical cable of ROV and the network of ARON using magnetometer software. The precision positions of magnetic data were merged by the post-processing of USBL of ROV. Hydrothermal fluids over Curie temperature can quickly alter or replace the iron-rich magnetic minerals, reducing the magnetic remanence of the crustal rocks, in some cases to near 0A/m magnetization. So, the obtained three component magnetic data are fully utilized by finding possible hydrothermal vents of the survey area.

  5. Prediction of sea surface temperatures in the western Mediterranean Sea by neural networks using satellite observations

    NASA Astrophysics Data System (ADS)

    Garcia-Gorriz, Elisa; Garcia-Sanchez, Joan

    2007-06-01

    We use artificial neural networks (ANNs) to predict sea surface temperatures (SSTs) in the western Mediterranean Sea. The ANNs are trained with meteorological variables as input and concurrent satellite-derived SSTs as target. The trained ANNs predict well both the seasonal and the interannual variability of SST in that region. We also reproduce the impact of the heat wave that occurred during the summer of 2003 on the SSTs of the western Mediterranean Sea. The ANN technique allows us to predict SST maps in the western Alboran Sea for time coordinates before SST satellite availability. The presence and later partial collapse of the western Alboran gyre throughout 1980 is detected with good agreement by both the ANN predictions and the concurrent results from a 3-D circulation model. The same methodology is used to reconstruct incomplete SST satellite images.

  6. 6 ka anoxic condition in the Sibuyan Sea Basin, Philippines - possible link with an explosive eruption event?

    NASA Astrophysics Data System (ADS)

    Catane, S. G.; Fernando, A.; Peleo-Alampay, A.; Tejada, M. G.

    2010-12-01

    Marine tephra layers in Philippine inland seas were studied to evaluate the history of explosive volcanism in the region and their impact on the marine environment. Two discrete andesitic (SiO*blc*2*elc* = 55-63 wt%) tephra layers were found at depths 446.5-448.4 cm and 454.9-455.8 cm in the gravity core MD 3057 recovered during the Marion Dufresne Marco Polo 2 cruise in 2006. The 7m-long core was retrieved from the northern portion of the Sibuyan Sea Basin at 1660 m below sea level. A C-14 age of 6 ka was obtained for the lower tephra using benthic foraminifera collected immediately below the tephra layer. The tephra layers have similar major element compositions and follow the same fractionation trend on the basis of glass geochemistry. Compositions are distinct from the nearby active andesitic volcanoes, Taal and Mayon. Microprobe imaging showed the occurrence of authigenic pyrite within the lower andesitic tephra layer. Pyrite occurs as euhedral crystals or granular masses (framboids), which are isolated particles or foraminiferal infillings. Framboidal pyrite is associated with anoxic environments where anaerobic bacteria reduces SO*blc*4*elc* dissolved in sea water, initiating the formation of H*blc*2*elc*S. H2S reacts with iron in sediments to form pyrite. Anoxic conditions occur in ocean basins with restricted water exchange due to a physical barrier (sill), density stratification or where input of organic material is high. Alternatively, anoxic conditions may have been caused by the death of benthic organisms due to tephra deposition by depriving the organisms of their food supply. The effect of this apparent anoxic event on benthic foraminifera will be analyzed in detail. It is postulated that these anoxic conditions may cause a decline in the benthic foraminifera occurrence. The extent and duration of anoxic condition of the northern part of the Sibuyan Sea Basin 6 ka needs to be clarified because present-day water condition in the basin is normal. If

  7. Investigaton of ÇINARCIK Basin and North Anatolian Fault Within the Sea of Marmara with Multichannel Seismic Reflection Data

    NASA Astrophysics Data System (ADS)

    Atgın, O.; Çifçi, G.; Sorlien, C.; Seeber, L.; Steckler, M.; Sillington, D.; Kurt, H.; Dondurur, D.; Okay, S.; Gürçay, S.; Sarıtaş, H.; Küçük, H. M.

    2012-04-01

    The Sea of Marmara is becoming a natural laboratory for structure, sedimentation, and fluid flow within the North Anatolian fault (NAF) system. Much marine geological and geophysical data has been collected there since the deadly 1999 M=7.2. Izmit earthquake. The Sea of Marmara occupies 3 major basins, with the study area located in the eastern Cinarcik basin near Istanbul. These basins are the results of an extensional component in releasing segments between bends in this right-lateral tranmsform. It is controversial whether the extensional component is taken up by partitioned normal slip on separate faults, or instead by oblique right-normal slip on the non-vertical main northern branch of the NAF. High resolution multichannel seismic reflection (MCS) and multibeam bathymetry data collected by R/V K.Piri Reis and R/V Le-Suroit as part of two different projects respectively entitled "SeisMarmara", "TAMAM" and "ESONET". 3000 km of multichannel seismic reflection profiles were collected in 2008 and 2010 using 72, 111, and 240 channels of streamer with a 6.25 m group interval. The generator-injector airgun was fired every 12.5 or 18.75 m and the resulting MCS data has 10-230 Hz frequency band. The aim of the study is to investigate continuation of North Anatolian Fault along the Sea of Marmara, in order to investigate migration of depo-centers past a fault bend. We also test and extend a recently-published age model, quantify extension across short normal faults, and investigate whether a major surface fault exists along the southern edge of Çınarcık Basin. MCS profiles indicate that main NAF strand is located at the northern boundary of Çınarcık Basin and has a large vertical component of slip. The geometry of the eastern (Tuzla) bend and estimated right-lateral slip rates from GPS data requires as much of ten mm/yr of extension across Çınarcık Basin. Based on the published age model, we calculate about 2 mm/yr of extension on short normal faults in the

  8. Occurrence, distribution and transport of pesticides into the Salton Sea Basin, California, 2001-2002

    USGS Publications Warehouse

    LeBlanc, L.A.; Kuivila, K.M.

    2008-01-01

    The Salton Sea is a hypersaline lake located in southeastern California. Concerns over the ecological impacts of sediment quality and potential human exposure to dust emissions from exposed lakebed sediments resulting from anticipated shrinking of shoreline led to a study of pesticide distribution and transport within the Salton Sea Basin, California, in 2001-2002. Three sampling stations-upriver, river mouth, and offshore-were established along each of the three major rivers that discharge into the Salton Sea. Large-volume water samples were collected for analysis of pesticides in water and suspended sediments at the nine sampling stations. Samples of the bottom sediment were also collected at each site for pesticide analysis. Sampling occurred in October 2001, March-April 2002, and October 2002, coinciding with the regional fall and spring peaks in pesticide use in the heavily agricultural watershed. Fourteen current-use pesticides were detected in water and the majority of dissolved concentrations ranged from the limits of detection to 151 ng/l. Diazinon, EPTC and malathion were detected at much higher concentrations (940-3,830 ng/l) at the New and Alamo River upriver and near-shore stations. Concentrations of carbaryl, dacthal, diazinon, and EPTC were higher in the two fall sampling periods, whereas concentrations of atrazine, carbofuran, and trifluralin were higher during the spring, which matched seasonal use patterns of these pesticides. Current-use pesticides were also detected on suspended and bed sediments in concentrations ranging from detection limits to 106 ng/g. Chlorpyrifos, dacthal, EPTC, trifluralin, and DDE were the most frequently detected pesticides on sediments from all three rivers. The number of detections and concentrations of suspended sediment-associated pesticides were often similar for the river upriver and near-shore sites, consistent with downstream transport of pesticides via suspended sediment. While detectable suspended sediment

  9. Possible connection between large volcanic eruptions and level rise episodes in the Dead Sea Basin

    NASA Astrophysics Data System (ADS)

    Bookman, Revital; Filin, Sagi; Avni, Yoav; Rosenfeld, Daniel; Marco, Shmuel

    2014-05-01

    The June 1991 Pinatubo volcanic eruption perturbed the atmosphere, triggering short-term worldwide changes in surface and lower troposphere temperatures, precipitation, and runoff. The following winter was anomalously wet in the Levant, with a ~2-meter increase in the Dead Sea level that created a distinct morphological terrace along the lake's shore. Given the global radiative and chemical effects of volcanogenic aerosols on climatic systems, we tested the hypothesis that the 1991-92 winter shore terrace is a modern analogue to the linkage between past volcanic eruptions and a sequence of shore terraces on the cliffs around the Dead Sea Basin. Analysis of historical annual precipitation series from Jerusalem showed a significant positive correlation between the Dust Veil Index (DVI) of the modern largest eruptions and corresponding annual rainfall. The DVI was found to explain nearly 50% of the variability in the annual rainfall, such that greater DVI means more rainfall. Other factors that may affect the annual rainfall in the region as the Southern Oscillation Index (SOI) and the North Atlantic oscillations (NAO) were incorporated along with the DVI in a linear multiple regression model. It was found that the NAO did not contribute anything except for increased noise, but the added SOI increased the explained variability of rainfall to more than 60%. The atmospheric effect of the volcanic aerosol cloud produced after the Mt. Pinatubo eruption shows responses in the climate system on a hemispherical to global scale. Volcanic eruptions with a VEI of 6, as in the Pinatubo, occurred about once a century during the Holocene period at a rate that persisted throughout the last glacial-interglacial cycle, though with large variations in the mean. This occurrence is similar to the frequency of shore terrace build-up during the Lake Lisan desiccation. Sixteen shore terraces, detected using airborne laser scanning data, were interpreted as indicating short-term level rises

  10. Mid-1980s distribution of tritium, 3He, 14C and 39Ar in the Greenland/Norwegian seas and the Nansen basin of the Arctic ocean

    SciTech Connect

    Schlosser, P.; Bonisch, G.; Kromer, B.; Loosli, H.H.; Buehler, R.

    1995-12-31

    The distributions of tritium/3He, 14C and 39Ar observed in the period between 1985 and 1987 in the Greenland/Norwegian Seas and the Nansen Basin of the Arctic Ocean are presented. The data are used to outline aspects of the large-scale circulation and the exchange of deep water between the Greenland/Norwegian Seas and the Nansen Basin. Additionally, semi-quantitative estimates of mean ages of the main water masses found in these regions are obtained. Apparent tritium/3He ages of the upper waters (depth <500m) vary from close to zero in the Norwegian Current to about 15 years at the lower boundary of the Arctic halocline. The deep waters (>1,500m depth) of the Greenland/ Norwegian Seas show apparent tritium/3He ages between about 17 years in the Greenland Sea and 30 years in the Norwegian Sea.

  11. Causes of different impact of Major Baltic Inflows on cod reproduction in the Gotland Basin of the Baltic Sea

    NASA Astrophysics Data System (ADS)

    Karaseva, E. M.; Zezera, A. S.

    2016-09-01

    The impact of the Major Baltic Inflows (MBIs) of 1976, 1993, and 2003 on cod reproduction in the Gotland Basin of the Baltic Sea is considered based on calculations of the eastern Baltic cod egg abundance and offspring survival indices. The reproductive success (1976-1977) was defined by the elevation of the 11 psu isohaline and deepening of the 2 mL/L isooxygene surface, which provided the formation of a water layer suitable for cod spawning at a depth of 90-130 m. Prerequisites of the appearance of the reproductive layer in 1976-1977 were a previously high salinity level and penetrating two successive MBIs in one year. The cause of the weak MBI impact in 1993 was the previous salinity minimum; in 2003 it was rapid oxygen depletion due to an increase in temperature. As a result of their weaker influence, small and fragmented cod spawning biotopes appeared in the Gotland Basin.

  12. Late quaternary depositional systems and sea level change-Santa Monica and San Pedro Basins, California continental borderland

    SciTech Connect

    Nardin, T.R.

    1983-07-01

    A suite of seismic reflection data that provides different degrees of resolution and penetration was used to map the depositional systems that have developed in Santa Monica and San Pedro basins during the late Quaternary. Submarine fan growth, particularly at the mouths of Hueneme and Redondo Canyons, has been the dominant mode of basin filling. Mass movement processes, ranging from creep to large-scale catastrophic slumping, have been important locally. In general, large-scale fan growth fits Normark's model in which the suprafan is the primary locus of coarse sediment deposition. Smaller scale morphologic and depositional patterns on the Hueneme and Redondo fans (e.g., distributary channels and coarse sediment concentrations basinward of the inner suprafan) suggest that a significant amount of coarse sediment presently bypasses the suprafans, however. Long-distance coarse sediment transport was particularly pronounced during late Wisconsinan lowstand of sea level and resulted in progradation of lower mid-fan and lower fan deposits.

  13. Carbon dioxide production in surface sediments of temporarily anoxic basins (Baltic Sea) and resulting sediment-water interface fluxes

    NASA Astrophysics Data System (ADS)

    Böttcher, M. E.; Al-Raei, A. M.; Winde, V.; Lenz, C.; Dellwig, O.; Leipe, T.; Segl, M.; Struck, U.

    2009-04-01

    Organic matter is mineralized in marine sediments by microbial activity using predominantly oxygen, sulfate, and metal oxides as electron acceptors. Modern euxinic basins as found in the Baltic Sea or the Black Sea are of particular importance because they may serve as type systems for anoxia in Earth's history. We present here results from biogeochemical investigations carried out in the Baltic deeps (Gotland Basin, Landsort Deep) during the first scientific cruise of RV M.S. MERIAN in 2006, additionally during RV Prof. Penck cruises in 2006 and 2007. Short sediment cores were obtained with a multi-corer and analyzed for particulate and dissolved main, minor and trace elements, pH, DIC, methane alkalinity, besides the stable carbon isotopes of dissolved inorganic carbon (DIC). Microsensors were applied to analyze steep gradients of oxygen, sulphide and sulphate. Pore water profiles are evaluated in terms of process rates and associated element fluxes using the PROFILE software (Berg et al., 1998, L&O). Gross and net anaerobic mineralization rates were additionally obtained from core incubations with 35S. Steep gradients in DIC are associated with a strong enrichment of the light stable isotope resulting in the Gotland basin from oxidized OM. Element fluxes across the sediment-water interface are compared with literature data and show for the Baltic Sea a dependence from bottom water redox conditions, and sediment compositions and formation conditions (e.g., accumulation rates). DIC in the anoxic part of the water column in the Landsort Deep and the Gotland Deep show relatively similar isotope values, close to the bottom water value, but steep gradients towards heavier values above the pelagic redoxcline. Acknowledgements: The research was supported by Leibniz IO Warnemünde, DFG (Cruise RV MSM MERIAN 01), and MPG. Thanks to B. Schneider and F. Pollehne stimulating discussions, and S. Lage and A. Schipper for technical support.

  14. Holocene fluvial terraces in the Gangkou River Basin of Hengchun Peninsula, Taiwan: implications for sea-level and tectonic controls

    NASA Astrophysics Data System (ADS)

    Chen, Jia-Hong; Chyi, Shyh-Jeng; Ho, Lih-Der; Jen, Chia-Hung; Yen, Jiun-Yee; Lüthgens, Christopher

    2016-04-01

    The Gangkou River basin is the largest basin in the eastern Hengchun Peninsula, which is the most latest emerged region of the Taiwan orogen. The width of the active channel of Gangkou River is narrow but the valleys from middle to downstream are remarkably wide, which indicates the features of underfit stream. Based on the 14C dates of buried tree trunk and terrace sediments, the preliminary model for the geomorphic evolution of Gangkou River is proposed as: Stage I: The wide spread fine-grained sediments of more than 30-meter-thick was found in the downstream area of drainage basin. The large-scale aggradation event was formed between 12000 to 7000 yr BP in response to the rapid sea-level rise during the late Pleistocene and early Holocene. Stage II: The 15 to 20-meter-high terraces of Gangkou River were formed by the incision and lateral erosion between 7000 to 400 yr BP. The 14C dates of marine terraces, beach rocks and sand dune near the estuary also indicate this erosional stage which could be related to the mid-Holocene climatic shift, tectonic uplift and the stabilized sea-level. Stage III: The 3 to 5-meter-high terraces were formed around 400 yr BP which indicated the low incision rate and the modern fluvial processes. The uplift rates are estimated by the height of river and marine terraces as 1.0 to 1.5 and 1.5 to 2.5 mm/yr respectively. The results indicate the low uplift rate maybe contributed to the underfit stream feature, and the fluvial terraces are responding to sea-level, tectonic and climate controls with different timescale in the Gangkou River. The low uplift rate found in the Gangkou River contradicted to the idea of high tectonic uplift rate in Taiwan.

  15. Subduction initiation and recycling of Alboran domain derived crustal components prior to the intra-crustal emplacement of mantle peridotites in the Westernmost Mediterranean: isotopic evidence from the Ronda peridotite

    NASA Astrophysics Data System (ADS)

    Varas-Reus, María Isabel; Garrido, Carlos J.; Bosch, Delphine; Marchesi, Claudio Claudio; Acosta-Vigil, Antonio; Hidas, Károly; Barich, Amel

    2014-05-01

    During Late Oligocene-Early Miocene different domains formed in the region between Iberia and Africa in the westernmost Mediterranean, including thinned continental crust and a Flysch Trough turbiditic deposits likely floored by oceanic crust [1]. At this time, the Ronda peridotite likely constituted the subcontinental lithospheric mantle of the Alboran domain, which mantle lithosphere was undergoing strong thinning and melting [2] [3] coevally with Early Miocene extension in the overlying Alpujárride-Maláguide stacked crust [4, 5]. Intrusive Cr- rich pyroxenites in the Ronda massif records the geochemical processes occurring in the subcontinental mantle of the Alboran domain during the Late Oligocene [6]. Recent isotopic studies of these pyroxenites indicate that their mantle source was contaminated by a subduction component released by detrital crustal sediments [6]. This new data is consistent with a subduction setting for the late evolution of the Alboran lithospheric mantle just prior to its final intracrustal emplacement in the early Miocene Further detailed structural studies of the Ronda plagioclase peridotites-related to the initial stages of ductile emplacement of the peridotite-have led to Hidas et al. [7] to propose a geodynamic model where folding and shearing of an attenuated mantle lithosphere occurred by backarc basin inversion followed by failed subduction initiation that ended into the intracrustal emplacement of peridotite into the Alboran wedge in the earliest Miocene. This hypothesis implies that the crustal component recorded in late, Cr-rich websterite dykes might come from underthrusted crustal rocks from the Flysch and/or Alpujárrides units that might have been involved in the earliest stages of this subduction initiation stage. To investigate the origin of crustal component in the mantle source of this late magmatic event recorded by Cr-pyroxenites, we have carried out a detail Sr-Nd-Pb-Hf isotopic study of a variety of Betic

  16. Crustal metamorphic fluid flux beneath the Dead Sea Basin: constraints from 2-D and 3-D magnetotelluric modelling

    NASA Astrophysics Data System (ADS)

    Meqbel, Naser; Weckmann, Ute; Muñoz, Gerard; Ritter, Oliver

    2016-12-01

    We report on a study to explore the deep electrical conductivity structure of the Dead Sea Basin (DSB) using magnetotelluric (MT) data collected along a transect across the DSB where the left lateral strike-slip Dead Sea transform (DST) fault splits into two fault strands forming one of the largest pull-apart basins of the world. A very pronounced feature of our 2-D inversion model is a deep, subvertical conductive zone beneath the DSB. The conductor extends through the entire crust and is sandwiched between highly resistive structures associated with Precambrian rocks of the basin flanks. The high electrical conductivity could be attributed to fluids released by dehydration of the uppermost mantle beneath the DSB, possibly in combination with fluids released by mid- to low-grade metamorphism in the lower crust and generation of hydrous minerals in the middle crust through retrograde metamorphism. Similar high conductivity zones associated with fluids have been reported from other large fault systems. The presence of fluids and hydrous minerals in the middle and lower crust could explain the required low friction coefficient of the DST along the eastern boundary of the DSB and the high subsidence rate of basin sediments. 3-D inversion models confirm the existence of a subvertical high conductivity structure underneath the DSB but its expression is far less pronounced. Instead, the 3-D inversion model suggests a deepening of the conductive DSB sediments off-profile towards the south, reaching a maximum depth of approximately 12 km, which is consistent with other geophysical observations. At shallower levels, the 3-D inversion model reveals salt diapirism as an upwelling of highly resistive structures, localized underneath the Al-Lisan Peninsula. The 3-D model furthermore contains an E-W elongated conductive structure to the northeast of the DSB. More MT data with better spatial coverage are required, however, to fully constrain the robustness of the above

  17. Food for the deep sea: utilization, dispersal, and flux of nekton falls at the Santa catalina basin floor

    NASA Astrophysics Data System (ADS)

    Smith, Craig R.

    1985-04-01

    The role of large food falls in the ecology of deep-sea benthos has been the topic of much speculation and little direct study. The submersible Alvin and free vehicles were used to assess experimentally the fate and flux of nekton falls at a depth of 1310 m in the Santa Catalina Basin. Parcels of dead fish (1 to 40 kg) placed on the basin floor rapidly attracted large aggregations of fish and invertebrate scavengers, which consumed the bulk of the carrion within hours to days. The most strongly attracted megafaunal scavenger was the ophiuroid Ophiophthalmus normani, the dominant megabenthic species in the background epifaunal assemblage. O. normani attained densities of 700 m -2 in aggregations containing thousands of individuals, and remained at elevated abundance around baitfalls for weeks. Six other megafaunal species also appeared to feed directly on carrion, including two of the next ten most abundant megabenthic organisms. Several of these species exhibited roosting behavior near baitfalls; this is probably an adaptation for exploiting rich but unpredictable food resources. Scavengers consumed bait parcels so rapidly and then dispersed so broadly that energy from nekton falls apparently reaches infaunal benthos only in very attenuated form, yielding at most minor community enhancement. Necrophagy was not the sole cause of megafaunal attraction to bait parcels; there is evidence that three predacious species were drawn to high concentrations of their ophiuroid prey. Benthic standing-crop and turnover-rate estimates for nekton falls suggest that perhaps 11% of benthic community respiratory requirements are met by nekton carcasses reaching the basin floor; the flux of energy to the deep sea through such fall events thus merits further study. These energy bonanzas occur frequently enough that O. normani, and other common necrophages, are likely to encounter at least one nekton fall per year. Such windfalls thus could influence the life histories of several

  18. Comparison of vertical distributions of prokaryotic assemblages in the anoxic Cariaco Basin and Black Sea by use of fluorescence in situ hybridization.

    PubMed

    Lin, Xueju; Wakeham, Stuart G; Putnam, Isabell F; Astor, Yrene M; Scranton, Mary I; Chistoserdov, Andrei Y; Taylor, Gordon T

    2006-04-01

    Individual prokaryotic cells from two major anoxic basins, the Cariaco Basin and the Black Sea, were enumerated throughout their water columns using fluorescence in situ hybridization (FISH) with the fluorochrome Cy3 or horseradish peroxidase-modified oligonucleotide probes. For both basins, significant differences in total prokaryotic abundance and phylogenetic composition were observed among oxic, anoxic, and transitional (redoxcline) waters. Epsilon-proteobacteria, Crenarchaeota, and Euryarchaeota were more prevalent in the redoxclines, where previous studies reported high rates of chemoautotrophic production relative to those in waters above and below the redoxclines. Relative abundances of Archaea in both systems varied between 1% and 28% of total prokaryotes, depending on depth. The prokaryotic community composition varied between the two anoxic basins, consistent with distinct geochemical and physical conditions. In the Black Sea, the relative contributions of group I Crenarchaeota (median, 5.5%) to prokaryotic communities were significantly higher (P < 0.001; n = 20) than those of group II Euryarchaeota (median, 2.9%). In contrast, their proportions were nearly equivalent in the Cariaco Basin. Beta-proteobacteria were unexpectedly common throughout the Cariaco Basin's water column, accounting for an average of 47% of 4',6'-diamidino-2-phenylindole (DAPI)-stained cells. This group was below the detection limit (<1%) in the Black Sea samples. Compositional differences between basins may reflect temporal variability in microbial populations and/or systematic differences in environmental conditions and the populations for which they select.

  19. Interactions of near-coastal and basin-wide features of the Mediterranean Sea in the surface colour and temperature historical record

    SciTech Connect

    Barale, V.; Filippi, P.

    1997-08-01

    Sea surface colour and temperature images, derived from time series of CZCS (1978-1986) and AVHRR (1982-1990) data, have been used to assess the interactions of near-coastal and basin-wide features in the Mediterranean basin. Individual images were processed to apply sensor(s) calibration, to correct for atmospheric contamination, and to estimate chlorophyll-like pigment concentration and surface temperature. Long-term composites show marked differences between western and eastern sub-basins, inshore and offshore domains, northern and southern near-coastal areas. Continental runoff and wind-driven mixing, as well as geomorphology and meteorology of the (northern) basin margins, appear to influence both water dynamics and bio-geo-chemistry. The major sub-basins present a distinct seasonality, superimposed to that of the basin.

  20. Interannual Variation of the Summer Rainfall in the Taipei Basin Caused by the Impact of ENSO on the Land-Sea Breeze Activity

    NASA Astrophysics Data System (ADS)

    Chen, Tsing-Chang; Tsay, Jenq-Dar; Takle, Eugene S.

    2015-04-01

    The Taipei Basin, located in northern Taiwan, is formed by the intersection of the Tanshui River Valley (~30km) and the Keelung River Valley (~60km). Summer is the dry season in northern Taiwan, but the maximum rainfall in the Taipei Basin occurs during the summer. The majority of summer rainfall (75%) in this Basin is produced by afternoon thunderstorms triggered by the sea breeze interactions with the mountains to the south of this Basin. Environmental conditions for the roughly three million people living in the Taipei Basin are greatly affected by the land-sea breeze and afternoon thunderstorm activities. Thus, the water supply, air-land traffic, and pollution for this extremely urbanized basin can be profoundly affected by interannual variations of thunderstorm days and rainfall. A systematic analysis was made of thunderstorm days and rainfall for the past two decades. Opposite the interannual variation of the sea surface temperature (SST) anomalies over the NOAA NINO3 - 4 region, ΔSST (NINO3 - 4), clear interannual variations of these two variables emerge. Occurrence days of afternoon thunderstorm and rainfall amount in the Taipei Basin are double during the cold ΔSST(NINO3 - 4) phase compared to the warm phase. During the latter (former) El Niño-Southern Oscillation (ENSO) phase, the Taipei Basin needs a stronger (weaker) warm/moist monsoon southwesterly flow channeled through the land-sea breeze to trigger thunderstorm activity. In contrast, the convergence of water vapor flux over the southeast/east Asian monsoon region toward Taiwan is enhanced more (less) to maintain rainfall over the Taipei Basin during the cold (warm) ENSO phase.

  1. Seismites in continental sand sea deposits of the Late Cretaceous Caiuá Desert, Bauru Basin, Brazil

    NASA Astrophysics Data System (ADS)

    Fernandes, Luiz Alberto; de Castro, Alice Bonatto; Basilici, Giorgio

    2007-07-01

    Two large-scale sediment deformation structures, minor fold occurrences in cross-bedded sand dune deposits and complex convolute folds, are observed in red sandstones, in a zone about 1.5 km long in floodway cuts at the Sérgio Motta/Porto Primavera dam, São Paulo state, Brazil. The most important structures are confined to planar zones, up to 10 m thick, in undeformed dune foreset strata were they can be traced laterally for about 50-60 m. The sandstones are part of the Rio Paraná Formation, Caiuá Group, which accumulated in a great sand sea of about 100,000 km 2. The Caiuá Desert developed during the Late Cretaceous in the southern part of the Bauru Basin, an intracontinental subsiding area in the central-southern part of the South-American Platform. The basin was filled by a sandy sequence about 300 m thick. The sand sea deposits correspond to the Caiuá Group and comprise: a) deposits of dry sand sheets (Santo Anastácio Formation), b) deposits of medium-sized dunes and humid interdunes of the sand sea peripheral zones (Goio Erê Formation), and c) deposits of large-sized complex aeolian dunes and draas, that correspond to the central part of the inland sand sea (Rio Paraná Formation). The deformations in the sediments are attributed to the effects of fluidization, liquefaction and shear stress, which are interpreted as being earthquake-induced structures, mainly because: (1) the deformed horizons are confined between undeformed cross-bedded strata, (2) the complex convolute folds sometimes include nappe-like structures that overlie foreset facies, (3) during the Bauru Basin infilling there was tectonic activity associated with alkaline volcanism on the borders of the basin and related silicification in the central-southern part. The main silicification zones are aligned to regional lineaments that cross the area near the large-scale sedimentary deformation structures.

  2. Archive of bacterial community in anhydrite crystals from a deep-sea basin provides evidence of past oil-spilling in a benthic environment in the Red Sea

    NASA Astrophysics Data System (ADS)

    Wang, Yong; Li, Tie Gang; Wang, Meng Ying; Lai, Qi Liang; Li, Jiang Tao; Gao, Zhao Ming; Shao, Zong Ze; Qian, Pei-Yuan

    2016-11-01

    In deep-sea sediment, the microbes present in anhydrite crystals are potential markers of the past environment. In the Atlantis II Deep, anhydrite veins were produced by mild mixture of calcium-rich hydrothermal solutions and sulfate in the bottom water, which had probably preserved microbial inhabitants in the past seafloor of the Red Sea. In this study, this hypothesis was tested by analyzing the metagenome of an anhydrite crystal sample from the Atlantis II Deep. The estimated age of the anhydrite layer was between 750 and 770 years, which might span the event of hydrothermal eruption into the benthic floor. The 16S/18S rRNA genes in the metagenome were assigned to bacteria, archaea, fungi and even invertebrate species. The dominant species in the crystals was an oil-degrading Alcanivorax borkumensis bacterium, which was not detected in the adjacent sediment layer. Fluorescence microscopy using 16S rRNA and marker gene probes revealed intact cells of the Alcanivorax bacterium in the crystals. A draft genome of A. borkumensis was binned from the metagenome. It contained all functional genes for alkane utilization and the reduction of nitrogen oxides. Moreover, the metagenomes of the anhydrites and control sediment contained aromatic degradation pathways, which were mostly derived from Ochrobactrum sp. Altogether, these results indicate an oxic, oil-spilling benthic environment in the Atlantis II basin of the Red Sea in approximately the 14th century. The original microbial inhabitants probably underwent a dramatic selection process via drastic environmental changes following the formation of an overlying anoxic brine pool in the basin due to hydrothermal activities.

  3. Evaluating Rifean Corridor Closure using Detrital Zircon Sediment Provenance of the Taza-Guercif Basin, Morocco

    NASA Astrophysics Data System (ADS)

    Pratt, J. R.; Barbeau, D. L.; Emran, A.

    2013-12-01

    In the late Miocene, the connection between the Mediterranean Sea and Atlantic Ocean was tectonically severed leading to severe evaporative draw down of Mediterranean sea level such that the entire basin was desiccated or near desiccated in an event from ~5.96-5.33 Ma known as the Messinian Salinity Crisis (MSC). The MSC sequestered 6% of global ocean salinity into evaporite deposits, created a deep, dry and hot basin that altered global atmospheric circulation, opened passageways for mammal migration between Europe, Africa and Arabia and ended in the largest flood observed in the geologic record. The combined effects of the Messinian Salinity Crisis make it the most important oceanic event in the last 20 million years, yet despite the dramatic ramifications of the MSC, the exact nature of its cause has remained both elusive and controversial. By examining the sedimentary provenance of Rifean Corridor, this research evaluates the progression of corridor closure and the tectonic context of the initiation of the Messinian Salinity Crisis. The difficulty in evaluating the progression of closure is due to the tectonic complexity of the Africa-Eurasia convergent plate boundary in north-central Morocco. The shortening associated with the tectonic convergence is accommodated by two genetically and tectonically distinct orogenic systems, the Rif and Atlas mountain belts, which lie in juxtaposition to the slab-rollback dominated Alboran Sea. The basins of the Rifean corridor lie between these two orogens and as such shortening and uplift associated with either or both ranges could be the cause of the corridor closure. Several hypotheses have been posited for the tectonic controls on basin emergence including slab-rollback related delamination on the Alboran margin, domal uplift of the Middle Atlas as well as a more traditional propagation of the Rifean orogenic wedge. This research provides the first quantitative provenance data for the Taza-Guercif basin in the form of LA

  4. Temporal variation of genetic composition in Atlantic salmon populations from the Western White Sea Basin: influence of anthropogenic factors?

    PubMed Central

    2013-01-01

    Background Studies of the temporal patterns of population genetic structure assist in evaluating the consequences of demographic and environmental changes on population stability and persistence. In this study, we evaluated the level of temporal genetic variation in 16 anadromous and 2 freshwater salmon populations from the Western White Sea Basin (Russia) using samples collected between 1995 and 2008. To assess whether the genetic stability was affected by human activity, we also evaluated the effect of fishing pressure on the temporal genetic variation in this region. Results We found that the genetic structure of salmon populations in this region was relatively stable over a period of 1.5 to 2.5 generations. However, the level of temporal variation varied among geographical regions: anadromous salmon of the Kola Peninsula exhibited a higher stability compared to that of the anadromous and freshwater salmon from the Karelian White Sea coast. This discrepancy was most likely attributed to the higher census, and therefore effective, population sizes of the populations inhabiting the rivers of the Kola Peninsula compared to salmon of the Karelian White Sea coast. Importantly, changes in the genetic diversity observed in a few anadromous populations were best explained by the increased level of fishing pressure in these populations rather than environmental variation or the negative effects of hatchery escapees. The observed population genetic patterns of isolation by distance remained consistent among earlier and more recent samples, which support the stability of the genetic structure over the period studied. Conclusions Given the increasing level of fishing pressure in the Western White Sea Basin and the higher level of temporal variation in populations exhibiting small census and effective population sizes, further genetic monitoring in this region is recommended, particularly on populations from the Karelian rivers. PMID:24053319

  5. Genomic and Transcriptomic Resolution of Organic Matter Utilization Among Deep-Sea Bacteria in Guaymas Basin Hydrothermal Plumes

    PubMed Central

    Li, Meng; Jain, Sunit; Dick, Gregory J.

    2016-01-01

    Microbial chemosynthesis within deep-sea hydrothermal vent plumes is a regionally important source of organic carbon to the deep ocean. Although chemolithoautotrophs within hydrothermal plumes have attracted much attention, a gap remains in understanding the fate of organic carbon produced via chemosynthesis. In the present study, we conducted shotgun metagenomic and metatranscriptomic sequencing on samples from deep-sea hydrothermal vent plumes and surrounding background seawaters at Guaymas Basin (GB) in the Gulf of California. De novo assembly of metagenomic reads and binning by tetranucleotide signatures using emergent self-organizing maps (ESOM) revealed 66 partial and nearly complete bacterial genomes. These bacterial genomes belong to 10 different phyla: Actinobacteria, Bacteroidetes, Chloroflexi, Deferribacteres, Firmicutes, Gemmatimonadetes, Nitrospirae, Planctomycetes, Proteobacteria, Verrucomicrobia. Although several major transcriptionally active bacterial groups (Methylococcaceae, Methylomicrobium, SUP05, and SAR324) displayed methanotrophic and chemolithoautotrophic metabolisms, most other bacterial groups contain genes encoding extracellular peptidases and carbohydrate metabolizing enzymes with significantly higher transcripts in the plume than in background, indicating they are involved in degrading organic carbon derived from hydrothermal chemosynthesis. Among the most abundant and active heterotrophic bacteria in deep-sea hydrothermal plumes are Planctomycetes, which accounted for seven genomes with distinct functional and transcriptional activities. The Gemmatimonadetes and Verrucomicrobia also had abundant transcripts involved in organic carbon utilization. These results extend our knowledge of heterotrophic metabolism of bacterial communities in deep-sea hydrothermal plumes. PMID:27512389

  6. Genomic and Transcriptomic Resolution of Organic Matter Utilization Among Deep-Sea Bacteria in Guaymas Basin Hydrothermal Plumes.

    PubMed

    Li, Meng; Jain, Sunit; Dick, Gregory J

    2016-01-01

    Microbial chemosynthesis within deep-sea hydrothermal vent plumes is a regionally important source of organic carbon to the deep ocean. Although chemolithoautotrophs within hydrothermal plumes have attracted much attention, a gap remains in understanding the fate of organic carbon produced via chemosynthesis. In the present study, we conducted shotgun metagenomic and metatranscriptomic sequencing on samples from deep-sea hydrothermal vent plumes and surrounding background seawaters at Guaymas Basin (GB) in the Gulf of California. De novo assembly of metagenomic reads and binning by tetranucleotide signatures using emergent self-organizing maps (ESOM) revealed 66 partial and nearly complete bacterial genomes. These bacterial genomes belong to 10 different phyla: Actinobacteria, Bacteroidetes, Chloroflexi, Deferribacteres, Firmicutes, Gemmatimonadetes, Nitrospirae, Planctomycetes, Proteobacteria, Verrucomicrobia. Although several major transcriptionally active bacterial groups (Methylococcaceae, Methylomicrobium, SUP05, and SAR324) displayed methanotrophic and chemolithoautotrophic metabolisms, most other bacterial groups contain genes encoding extracellular peptidases and carbohydrate metabolizing enzymes with significantly higher transcripts in the plume than in background, indicating they are involved in degrading organic carbon derived from hydrothermal chemosynthesis. Among the most abundant and active heterotrophic bacteria in deep-sea hydrothermal plumes are Planctomycetes, which accounted for seven genomes with distinct functional and transcriptional activities. The Gemmatimonadetes and Verrucomicrobia also had abundant transcripts involved in organic carbon utilization. These results extend our knowledge of heterotrophic metabolism of bacterial communities in deep-sea hydrothermal plumes.

  7. Diazotroph Diversity in the Sea Ice, Melt Ponds, and Surface Waters of the Eurasian Basin of the Central Arctic Ocean.

    PubMed

    Fernández-Méndez, Mar; Turk-Kubo, Kendra A; Buttigieg, Pier L; Rapp, Josephine Z; Krumpen, Thomas; Zehr, Jonathan P; Boetius, Antje

    2016-01-01

    The Eurasian basin of the Central Arctic Ocean is nitrogen limited, but little is known about the presence and role of nitrogen-fixing bacteria. Recent studies have indicated the occurrence of diazotrophs in Arctic coastal waters potentially of riverine origin. Here, we investigated the presence of diazotrophs in ice and surface waters of the Central Arctic Ocean in the summer of 2012. We identified diverse communities of putative diazotrophs through targeted analysis of the nifH gene, which encodes the iron protein of the nitrogenase enzyme. We amplified 529 nifH sequences from 26 samples of Arctic melt ponds, sea ice and surface waters. These sequences resolved into 43 clusters at 92% amino acid sequence identity, most of which were non-cyanobacterial phylotypes from sea ice and water samples. One cyanobacterial phylotype related to Nodularia sp. was retrieved from sea ice, suggesting that this important functional group is rare in the Central Arctic Ocean. The diazotrophic community in sea-ice environments appear distinct from other cold-adapted diazotrophic communities, such as those present in the coastal Canadian Arctic, the Arctic tundra and glacial Antarctic lakes. Molecular fingerprinting of nifH and the intergenic spacer region of the rRNA operon revealed differences between the communities from river-influenced Laptev Sea waters and those from ice-related environments pointing toward a marine origin for sea-ice diazotrophs. Our results provide the first record of diazotrophs in the Central Arctic and suggest that microbial nitrogen fixation may occur north of 77°N. To assess the significance of nitrogen fixation for the nitrogen budget of the Arctic Ocean and to identify the active nitrogen fixers, further biogeochemical and molecular biological studies are needed.

  8. Diazotroph Diversity in the Sea Ice, Melt Ponds, and Surface Waters of the Eurasian Basin of the Central Arctic Ocean

    PubMed Central

    Fernández-Méndez, Mar; Turk-Kubo, Kendra A.; Buttigieg, Pier L.; Rapp, Josephine Z.; Krumpen, Thomas; Zehr, Jonathan P.; Boetius, Antje

    2016-01-01

    The Eurasian basin of the Central Arctic Ocean is nitrogen limited, but little is known about the presence and role of nitrogen-fixing bacteria. Recent studies have indicated the occurrence of diazotrophs in Arctic coastal waters potentially of riverine origin. Here, we investigated the presence of diazotrophs in ice and surface waters of the Central Arctic Ocean in the summer of 2012. We identified diverse communities of putative diazotrophs through targeted analysis of the nifH gene, which encodes the iron protein of the nitrogenase enzyme. We amplified 529 nifH sequences from 26 samples of Arctic melt ponds, sea ice and surface waters. These sequences resolved into 43 clusters at 92% amino acid sequence identity, most of which were non-cyanobacterial phylotypes from sea ice and water samples. One cyanobacterial phylotype related to Nodularia sp. was retrieved from sea ice, suggesting that this important functional group is rare in the Central Arctic Ocean. The diazotrophic community in sea-ice environments appear distinct from other cold-adapted diazotrophic communities, such as those present in the coastal Canadian Arctic, the Arctic tundra and glacial Antarctic lakes. Molecular fingerprinting of nifH and the intergenic spacer region of the rRNA operon revealed differences between the communities from river-influenced Laptev Sea waters and those from ice-related environments pointing toward a marine origin for sea-ice diazotrophs. Our results provide the first record of diazotrophs in the Central Arctic and suggest that microbial nitrogen fixation may occur north of 77°N. To assess the significance of nitrogen fixation for the nitrogen budget of the Arctic Ocean and to identify the active nitrogen fixers, further biogeochemical and molecular biological studies are needed. PMID:27933047

  9. Micromechanics of sea ice frictional slip from test basin scale experiments

    NASA Astrophysics Data System (ADS)

    Sammonds, Peter R.; Hatton, Daniel C.; Feltham, Daniel L.

    2017-02-01

    We have conducted a series of high-resolution friction experiments on large floating saline ice floes in an environmental test basin. In these experiments, a central ice floe was pushed between two other floes, sliding along two interfacial faults. The frictional motion was predominantly stick-slip. Shear stresses, normal stresses, local strains and slip displacement were measured along the sliding faults, and acoustic emissions were monitored. High-resolution measurements during a single stick-slip cycle at several positions along the fault allowed us to identify two phases of frictional slip: a nucleation phase, where a nucleation zone begins to slip before the rest of the fault, and a propagation phase when the entire fault is slipping. This is slip-weakening behaviour. We have therefore characterized what we consider to be a key deformation mechanism in Arctic Ocean dynamics. In order to understand the micromechanics of sea ice friction, we have employed a theoretical constitutive relation (i.e. an equation for shear stress in terms of temperature, normal load, acceleration, velocity and slip displacement) derived from the physics of asperity-asperity contact and sliding (Hatton et al. 2009 Phil. Mag. 89, 2771-2799 (doi:10.1080/14786430903113769)). We find that our experimental data conform reasonably with this frictional law once slip weakening is introduced. We find that the constitutive relation follows Archard's law rather than Amontons' law, with ? (where τ is the shear stress and σn is the normal stress) and n = 26/27, with a fractal asperity distribution, where the frictional shear stress, τ = ffractal Tmlws, where ffractal is the fractal asperity height distribution, Tml is the shear strength for frictional melting and lubrication and ws is the slip weakening. We can therefore deduce that the interfacial faults failed in shear for these experimental conditions through processes of brittle failure of asperities in shear, and, at higher velocities

  10. Sedimentary and structural controls on seismogenic slumping within mass transport deposits from the Dead Sea Basin

    NASA Astrophysics Data System (ADS)

    Alsop, G. I.; Marco, S.; Weinberger, R.; Levi, T.

    2016-10-01

    Comparatively little work has been undertaken on how sedimentary environments and facies changes can influence detailed structural development in slump sheets associated with mass transport deposits (MTDs). The nature of downslope deformation at the leading edge of MTDs is currently debated in terms of frontally emergent, frontally confined and open-toed models. An opportunity to study and address these issues occurs within the Dead Sea Basin, where six individual slump sheets (S1-S6) form MTDs in the Late Pleistocene Lisan Formation. All six slumps, which are separated from one another by undeformed beds, are traced towards the NE for up to 1 km, and each shows a change in sedimentary facies from detrital-rich in the SW, to more aragonite-rich in the NE. The detrital-rich facies is sourced predominantly from the rift margin 1.5 km further SW, while the aragonite-rich facies represents evaporitic precipitation in the hyper saline Lake Lisan. The stacked system of MTDs translates downslope towards the NE and follows a pre-determined sequence controlled by the sedimentary facies. Each individual slump roots downwards into underlying detrital-rich layers and displays a greater detrital content towards the SW, which is marked by increasing folding, while increasing aragonite content towards the NE is associated with more discrete thrusts. The MTDs thin downslope towards the NE, until they pass laterally into undeformed beds at the toe. The amount of contraction also reduces downslope from a maximum of 50% to < 10% at the toe, where upright folds form diffuse 'open-toed' systems. We suggest that MTDs are triggered by seismic events, facilitated by detrital-rich horizons, and controlled by palaeoslope orientation. The frequency of individual failures is partially controlled by local environmental influences linked to detrital input and should therefore be used with some caution in more general palaeoseismic studies. We demonstrate that MTDs display 'open toes' where

  11. Gas hydrate environmental monitoring program in the Ulleung Basin, East Sea of Korea

    NASA Astrophysics Data System (ADS)

    Ryu, Byong-Jae; Chun, Jong-Hwa; McLean, Scott

    2013-04-01

    As a part of the Korean National Gas Hydrate Program, the Korea Institute of Geoscience and Mineral Resources (KIGAM) has been planned and conducted the environmental monitoring program for the gas hydrate production test in the Ulleung Basin, East Sea of Korea in 2014. This program includes a baseline survey using a KIGAM Seafloor Observation System (KISOS) and R/V TAMHAE II of KIGAM, development of a KIGAM Seafloor Monitoring System (KIMOS), and seafloor monitoring on various potential hazards associated with the dissociated gas from gas hydrates during the production test. The KIGAM also plans to conduct the geophysical survey for determining the change of gas hydrate reservoirs and production-efficiency around the production well before and after the production test. During production test, release of gas dissociated from the gas hydrate to the water column, seafloor deformation, changes in chemical characteristics of bottom water, changes in seafloor turbidity, etc. will be monitored by using the various monitoring instruments. The KIMOS consists of a near-field observation array and a far-field array. The near-field array is constructed with four remote sensor platforms each, and cabled to the primary node. The far-field sensor array will consists of four autonomous instrument pods. A scientific Remotely Operated Vehicle (ROV) will be used to deploy the sensor arrays, and to connect the cables to each field instrument package and a primary node. A ROV will also be tasked to collect the water and/or gas samples, and to identify any gas (bubble) plumes from the seafloor using a high-frequency sector scanning sonar. Power to the near-field instrument packages will be supplied by battery units located on the seafloor near the primary node. Data obtained from the instruments on the near-field array will be logged and downloaded in-situ at the primary node, and transmitted real-time to the support vessel using a ROV. These data will also be transmitted real-time to

  12. Benthic nutrient fluxes in the Eastern Gotland Basin (Baltic Sea) with particular focus on microbial mat ecosystems

    NASA Astrophysics Data System (ADS)

    Noffke, A.; Sommer, S.; Dale, A. W.; Hall, P. O. J.; Pfannkuche, O.

    2016-06-01

    Benthic fluxes and water column distributions of dissolved inorganic nitrogen (DIN) and total dissolved phosphate (PO43 -) were measured in situ at 7 sites across a redox gradient from oxic to anoxic bottom waters in the Eastern Gotland Basin (Baltic Sea). The study area was divided into the oxic zone (60 to ca. 80 m water depth, O2 > 30 μM), the hypoxic transition zone (HTZ, ca. 80 to 120 m, O2 < 30 μM) and the deep anoxic and sulfidic basin (> ca. 120 m). Sediments in the HTZ were covered by mats of vacuolated sulfur bacteria. Ammonium (NH4+) fluxes in the deep basin and the HTZ were elevated at 0.6 mmol m- 2 d- 1 and 1 mmol m- 2 d- 1, respectively. Nitrate (NO3-) fluxes were directed into the sediment at all stations in the HTZ and were zero in the deep basin. PO43 - release was highest in the HTZ at 0.23 mmol m- 2 d- 1, with a further release of 0.2 mmol m- 2 d- 1 in the deep basin. Up-scaling the benthic fluxes to the Baltic Proper equals 109 kt yr- 1 of PO43 - and 266 kt yr- 1 of DIN. This is eight- and two-fold higher than the total external load of P (14 kt yr- 1) and DIN (140 kt yr- 1) in 2006 (HELCOM 2009b). The HTZ makes an important contribution to the internal nutrient loading in the Baltic Proper, releasing 70% of P (76 kt yr- 1) and 75% of DIN (200 kt yr- 1) despite covering only 51% of area.

  13. Extreme drying event in the Dead Sea basin during MIS5 from the ICDP Dead Sea Deep Drill Core

    NASA Astrophysics Data System (ADS)

    Goldstein, S. L.; Stein, M.; Ben-Avraham, Z.; Agnon, A.; Ariztegui, D.; Brauer, A.; Haug, G. H.; Ito, E.; Kitagawa, H.; Torfstein, A.; Yasuda, Y.; The Icdp-Dsddp Scientific Party

    2011-12-01

    The ICDP funded Dead Sea Deep Drilling Project (DSDDP) recovered the longest and most complete paleo-environmental record in the Middle East, drilling holes of ~450 and ~350 meters in length in deep (~300 m below the lake level) and shallow sites (~3 mbll) respectively. The Dead Sea expands during the glacials and contracts during interglacials, and the sediments comprise a geological archive of the evolving environmental conditions (e.g. rains, floods, dust-storms, droughts). Dead Sea sediments include inorganic aragonite, allowing for dating by U-series (e.g. Haase-Schramm et al. GCA 2004). The deep site cores were opened and described in June 2011. The cores are composed mainly of alternating intervals of marl (aragonite, gypsum and detritus) during glacials, and salts and marls during interglacials. From this stratigraphy we estimate that the deep site core spans ~200 kyr (to the boundary of MIS 6 and 7). A dramatic discovery is a ~40 cm thick interval of partly rounded pebbles at ~235 m below the lake floor. This is the only clean pebbly unit in the entire core. It appears to be a beach layer, near the deepest part of the Dead Sea, lying above ~35 meters of mainly salt. If it is a beach layer, it implies an almost complete dry-down of the paleo-Dead Sea. The pebble layer lies within the last interglacial interval. Our initial attempt to more precisely estimate the age of the possible dry down shows an intriguing correlation between the salt-mud stratigraphy of the Dead Sea core and the oxygen isotope record of Soreq Cave, whereby excursions to light oxygen in the speleothems correspond to periods of salt deposition. Through this comparison, we estimate that the possible dry down occurred during MIS 5e. The occurrence of ~35 meters of mainly salt along with the pebble layer demonstrates a severe dry interval during MIS 5. This observation has implications for the Middle East today, where the Dead Sea level is dropping as all the countries in the area use the

  14. Comparative population structure of two deep-sea hydrothermal-vent-associated decapods (Chorocaris sp. 2 and Munidopsis lauensis) from southwestern Pacific back-arc basins.

    PubMed

    Thaler, Andrew David; Plouviez, Sophie; Saleu, William; Alei, Freddie; Jacobson, Alixandra; Boyle, Emily A; Schultz, Thomas F; Carlsson, Jens; Van Dover, Cindy Lee

    2014-01-01

    Studies of genetic connectivity and population structure in deep-sea chemosynthetic ecosystems often focus on endosymbiont-hosting species that are directly dependent on chemical energy extracted from vent effluent for survival. Relatively little attention has been paid to vent-associated species that are not exclusively dependent on chemosynthetic ecosystems. Here we assess connectivity and population structure of two vent-associated invertebrates--the shrimp Chorocaris sp. 2 and the squat lobster Munidopsis lauensis--that are common at deep-sea hydrothermal vents in the western Pacific. While Chorocaris sp. 2 has only been observed at hydrothermal vent sites, M. lauensis can be found throughout the deep sea but occurs in higher abundance around the periphery of active vents We sequenced mitochondrial COI genes and deployed nuclear microsatellite markers for both species at three sites in Manus Basin and either North Fiji Basin (Chorocaris sp. 2) or Lau Basin (Munidopsis lauensis). We assessed genetic differentiation across a range of spatial scales, from approximately 2.5 km to more than 3000 km. Population structure for Chorocaris sp. 2 was comparable to that of the vent-associated snail Ifremeria nautilei, with a single seemingly well-mixed population within Manus Basin that is genetically differentiated from conspecifics in North Fiji Basin. Population structure for Munidopsis lauensis was more complex, with two genetically differentiated populations in Manus Basin and a third well-differentiated population in Lau Basin. The unexpectedly high level of genetic differentiation between M. lauensis populations in Manus Basin deserves further study since it has implications for conservation and management of diversity in deep-sea hydrothermal vent ecosystems.

  15. Comparative Population Structure of Two Deep-Sea Hydrothermal-Vent-Associated Decapods (Chorocaris sp. 2 and Munidopsis lauensis) from Southwestern Pacific Back-Arc Basins

    PubMed Central

    Thaler, Andrew David; Plouviez, Sophie; Saleu, William; Alei, Freddie; Jacobson, Alixandra; Boyle, Emily A.; Schultz, Thomas F.; Carlsson, Jens; Van Dover, Cindy Lee

    2014-01-01

    Studies of genetic connectivity and population structure in deep-sea chemosynthetic ecosystems often focus on endosymbiont-hosting species that are directly dependent on chemical energy extracted from vent effluent for survival. Relatively little attention has been paid to vent-associated species that are not exclusively dependent on chemosynthetic ecosystems. Here we assess connectivity and population structure of two vent-associated invertebrates—the shrimp Chorocaris sp. 2 and the squat lobster Munidopsis lauensis—that are common at deep-sea hydrothermal vents in the western Pacific. While Chorocaris sp. 2 has only been observed at hydrothermal vent sites, M. lauensis can be found throughout the deep sea but occurs in higher abundance around the periphery of active vents We sequenced mitochondrial COI genes and deployed nuclear microsatellite markers for both species at three sites in Manus Basin and either North Fiji Basin (Chorocaris sp. 2) or Lau Basin (Munidopsis lauensis). We assessed genetic differentiation across a range of spatial scales, from approximately 2.5 km to more than 3000 km. Population structure for Chorocaris sp. 2 was comparable to that of the vent-associated snail Ifremeria nautilei, with a single seemingly well-mixed population within Manus Basin that is genetically differentiated from conspecifics in North Fiji Basin. Population structure for Munidopsis lauensis was more complex, with two genetically differentiated populations in Manus Basin and a third well-differentiated population in Lau Basin. The unexpectedly high level of genetic differentiation between M. lauensis populations in Manus Basin deserves further study since it has implications for conservation and management of diversity in deep-sea hydrothermal vent ecosystems. PMID:24983244

  16. The world’s earliest Aral-Sea type disaster: the decline of the Loulan Kingdom in the Tarim Basin

    PubMed Central

    Mischke, Steffen; Liu, Chenglin; Zhang, Jiafu; Zhang, Chengjun; Zhang, Hua; Jiao, Pengcheng; Plessen, Birgit

    2017-01-01

    Remnants of cities and farmlands in China’s hyperarid Tarim Basin indicate that environmental conditions were significantly wetter two millennia ago in a region which is barren desert today. Historical documents and age data of organic remains show that the Loulan Kingdom flourished during the Han Dynasty (206 BCE–220 CE) but was abandoned between its end and 645 CE. Previous archaeological, geomorphological and geological studies suggest that deteriorating climate conditions led to the abandonment of the ancient desert cities. Based on analyses of lake sediments from Lop Nur in the eastern Tarim Basin and a review of published records, we show that the Loulan Kingdom decline resulted from a man-made environmental disaster comparable to the recent Aral Sea crisis rather than from changing climate. Lop Nur and other lakes within the Han Dynasty realm experienced rapidly declining water levels or even desiccation whilst lakes in adjacent regions recorded rising levels and relatively wet conditions during the time of the Loulan Kingdom decline. Water withdrawal for irrigation farming in the middle reaches of rivers likely caused water shortage downstream and eventually the widespread deterioration of desert oases a long time before man initiated the Aral Sea disaster in the 1960s. PMID:28240223

  17. The world’s earliest Aral-Sea type disaster: the decline of the Loulan Kingdom in the Tarim Basin

    NASA Astrophysics Data System (ADS)

    Mischke, Steffen; Liu, Chenglin; Zhang, Jiafu; Zhang, Chengjun; Zhang, Hua; Jiao, Pengcheng; Plessen, Birgit

    2017-02-01

    Remnants of cities and farmlands in China’s hyperarid Tarim Basin indicate that environmental conditions were significantly wetter two millennia ago in a region which is barren desert today. Historical documents and age data of organic remains show that the Loulan Kingdom flourished during the Han Dynasty (206 BCE–220 CE) but was abandoned between its end and 645 CE. Previous archaeological, geomorphological and geological studies suggest that deteriorating climate conditions led to the abandonment of the ancient desert cities. Based on analyses of lake sediments from Lop Nur in the eastern Tarim Basin and a review of published records, we show that the Loulan Kingdom decline resulted from a man-made environmental disaster comparable to the recent Aral Sea crisis rather than from changing climate. Lop Nur and other lakes within the Han Dynasty realm experienced rapidly declining water levels or even desiccation whilst lakes in adjacent regions recorded rising levels and relatively wet conditions during the time of the Loulan Kingdom decline. Water withdrawal for irrigation farming in the middle reaches of rivers likely caused water shortage downstream and eventually the widespread deterioration of desert oases a long time before man initiated the Aral Sea disaster in the 1960s.

  18. The world's earliest Aral-Sea type disaster: the decline of the Loulan Kingdom in the Tarim Basin.

    PubMed

    Mischke, Steffen; Liu, Chenglin; Zhang, Jiafu; Zhang, Chengjun; Zhang, Hua; Jiao, Pengcheng; Plessen, Birgit

    2017-02-27

    Remnants of cities and farmlands in China's hyperarid Tarim Basin indicate that environmental conditions were significantly wetter two millennia ago in a region which is barren desert today. Historical documents and age data of organic remains show that the Loulan Kingdom flourished during the Han Dynasty (206 BCE-220 CE) but was abandoned between its end and 645 CE. Previous archaeological, geomorphological and geological studies suggest that deteriorating climate conditions led to the abandonment of the ancient desert cities. Based on analyses of lake sediments from Lop Nur in the eastern Tarim Basin and a review of published records, we show that the Loulan Kingdom decline resulted from a man-made environmental disaster comparable to the recent Aral Sea crisis rather than from changing climate. Lop Nur and other lakes within the Han Dynasty realm experienced rapidly declining water levels or even desiccation whilst lakes in adjacent regions recorded rising levels and relatively wet conditions during the time of the Loulan Kingdom decline. Water withdrawal for irrigation farming in the middle reaches of rivers likely caused water shortage downstream and eventually the widespread deterioration of desert oases a long time before man initiated the Aral Sea disaster in the 1960s.

  19. Enzymatic microbial Mn(II) oxidation and Mn biooxide production in the Guaymas Basin deep-sea hydrothermal plume

    NASA Astrophysics Data System (ADS)

    Dick, Gregory J.; Clement, Brian G.; Webb, Samuel M.; Fodrie, F. Joel; Bargar, John R.; Tebo, Bradley M.

    2009-11-01

    Microorganisms play important roles in mediating biogeochemical reactions in deep-sea hydrothermal plumes, but little is known regarding the mechanisms that underpin these transformations. At Guaymas Basin (GB) in the Gulf of California, hydrothermal vents inject fluids laden with dissolved Mn(II) (dMn) into the deep waters of the basin where it is oxidized and precipitated as particulate Mn(III/IV) oxides, forming turbid hydrothermal "clouds". Previous studies have predicted extremely short residence times for dMn at GB and suggested they are the result of microbially-mediated Mn(II) oxidation and precipitation. Here we present biogeochemical results that support a central role for microorganisms in driving Mn(II) oxidation in the GB hydrothermal plume, with enzymes being the primary catalytic agent. dMn removal rates at GB are remarkably fast for a deep-sea hydrothermal plume (up to 2 nM/h). These rapid rates were only observed within the plume, not in background deep-sea water above the GB plume or at GB plume depths (˜1750-2000 m) in the neighboring Carmen Basin, where there is no known venting. dMn removal is dramatically inhibited under anoxic conditions and by the presence of the biological poison, sodium azide. A conspicuous temperature optimum of dMn removal rates (˜40 °C) and a saturation-like (i.e. Michaelis-Menten) response to O 2 concentration were observed, indicating an enzymatic mechanism. dMn removal was resistant to heat treatment used to select for spore-forming organisms, but very sensitive to low concentrations of added Cu, a cofactor required by the putative Mn(II)-oxidizing enzyme. Extended X-ray absorption fine structure spectroscopy (EXAFS) and synchrotron radiation-based X-ray diffraction (SR-XRD) revealed the Mn oxides to have a hexagonal birnessite or δ-MnO 2-like mineral structure, indicating that these freshly formed deep-sea Mn oxides are strikingly similar to primary biogenic Mn oxides produced by laboratory cultures of bacteria

  20. Structure and tectonic evolution of the Tornquist Zone and adjacent sedimentary basins in Scania and the southern Baltic Sea area

    NASA Astrophysics Data System (ADS)

    Erlström, M.; Thomas, S. A.; Deeks, N.; Sivhed, U.

    1997-04-01

    Southernmost Sweden, Bornholm and the surrounding Baltic Sea region are located on a large-scale releasing bend in the dextral strike-slip system of the Tornquist Zone, with its resulting pull-apart basins. The well constrained geology of Scania and Bornholm has been combined with detailed on- and offshore borehole data and three proprietary marine seismic surveys. This in conjunction with supplementary BABEL deep seismic reflection findings allows a combined 3D interpretation of sediment/structure interactions. As a result, a regional interpretation has emerged which gives a new understanding of the interplay between structural movement on a complex strike-slip fault system (Tornquist Zone) and its intrazonal depressions (Vomb Trough and Colonus Shale Trough) as well as the sedimentation history of associated areas of sediment accumulation (Rønne and Arnager Grabens, Höllviken Halfgraben, Hanö Bay Basin and Skurup Platform). Detailed sequential litho- and seismo-stratigraphic descriptions have been possible by combination of the various data sets. This resulted in the clarification or recognition of previously unknown structural limits to sub-basins and highs in the study area. A 3D chronological (4D) model for the development of the region is proposed. This model takes into account the long-lived structural history combining elements of strike-slip, extension and inversion tectonics. The deep-seated faulting controlling these structures is integrated with the deep structure as revealed by the BABEL line in this area.

  1. Diversity and distribution of diazotrophic communities in the South China Sea deep basin with mesoscale cyclonic eddy perturbations.

    PubMed

    Zhang, Yao; Zhao, Zihao; Sun, Jun; Jiao, Nianzhi

    2011-12-01

    The South China Sea (SCS) is an oligotrophic subtropical marginal ocean with a deep basin and a permanently stratified central gyre. Upwelling and nitrogen fixation provide new nitrogen for primary production in the SCS. This study was aimed at an investigation of phylogenetic diversity and quantification of the diazotroph community in the SCS deep basin, which is characterized by frequent mesoscale eddies. The diazotroph community had a relatively low diversity but a distinct spatial heterogeneity of diversity in the SCS deep basin. The potential for nitrogen fixation consistently occurred during cyclonic eddies, although upwelling of nutrient-replete deep water might have alleviated nitrogen limitation in the SCS. However, diazotrophic proteobacteria were dominant, but neither Trichodesmium nor heterocystous cyanobacterial diatom symbionts. Quantitative PCR analysis using probe-primer sets developed in this study revealed that the nif H gene of the two dominant alpha- and gammaproteobacterial groups was at the highest abundance (up to 10(4) to 10(5)  copies L(-1) ). Trichodesmium thiebautii was detected with an average density of 10(2)  trichomes L(-1) in the euphotic waters, while Richelia intracellularis was observed sporadically under the microscope. The unicellular cyanobacterial groups A and B were not detected in our libraries. Our results suggested that diazotrophic proteobacteria were significant components potentially contributing to nitrogen fixation in this oligotrophic marginal ocean ecosystem.

  2. A new species of Cottus from the Onega River drainage, White Sea basin (Actinopterygii: Scorpaeniformes: Cottidae).

    PubMed

    Sideleva, Valentina G; Naseka, Alexander M; Zhidkov, Zakhar V

    2015-04-29

    Cottus gratzianowi, a new cottid species, is described from material collected in the Ukhtomitsa River in the Onega River drainage, White Sea basin. It differs from its congeners in Europe east of the Meuse except C. koshewnikowi by having no transverse dark bands on the pelvic fin, a single chin canal pore, an incomplete lateral line not reaching behind the anal-fin insertion, and the position of the lateral line which is located considerably above the mid-line of the flank. From C. koshewnikowi distributed in the Volga (Caspian basin), Pechora, and Northern Dvina rivers (Arctic basin), C. gratzianowi sp. nov. can be distinguished by a combination of character states, the most differentiating are as follows: a larger eye (horizontal diameter 23-28% HL, equal to or exceeding snout length vs. 16-25% HL, less than snout length), a rounded caudal fin (vs. commonly truncated), frequent presence of one to three branched rays in median part of the pectoral fin (vs. usual absence), an interrupted supratemporal canal commissure with 4 pores (vs. non-interrupted, with 3 pores), abdominal vertebrae commonly 10 (vs. 11), and contrasting black blotches on all fins including pelvic and anal fins (vs. no blotches on pelvic and anal fins).

  3. Protistan community patterns within the brine and halocline of deep hypersaline anoxic basins in the eastern Mediterranean Sea.

    PubMed

    Edgcomb, Virginia; Orsi, William; Leslin, Chesley; Epstein, Slava S; Bunge, John; Jeon, Sunok; Yakimov, Michail M; Behnke, Anke; Stoeck, Thorsten

    2009-01-01

    Environmental factors restrict the distribution of microbial eukaryotes but the exact boundaries for eukaryotic life are not known. Here, we examine protistan communities at the extremes of salinity and osmotic pressure, and report rich assemblages inhabiting Bannock and Discovery, two deep-sea superhaline anoxic basins in the Mediterranean. Using a rRNA-based approach, we detected 1,538 protistan rRNA gene sequences from water samples with total salinity ranging from 39 to 280 g/Kg, and obtained evidence that this DNA was endogenous to the extreme habitat sampled. Statistical analyses indicate that the discovered phylotypes represent only a fraction of species actually inhabiting both the brine and the brine-seawater interface, with as much as 82% of the actual richness missed by our survey. Jaccard indices (e.g., for a comparison of community membership) suggest that the brine/interface protistan communities are unique to Bannock and Discovery basins, and share little (0.8-2.8%) in species composition with overlying waters with typical marine salinity and oxygen tension. The protistan communities from the basins' brine and brine/seawater interface appear to be particularly enriched with dinoflagellates, ciliates and other alveolates, as well as fungi, and are conspicuously poor in stramenopiles. The uniqueness and diversity of brine and brine-interface protistan communities make them promising targets for protistan discovery.

  4. 3D seismic analysis of the Collyhurst Sandstone: implications for CO2 sequestration in the East Irish Sea Basin

    NASA Astrophysics Data System (ADS)

    Gamboa, Davide; Williams, John; Kirk, Karen; Gent, Christopher; Bentham, Michelle; Fellgett, Mark; Schofield, David

    2016-04-01

    Carbon Capture and Storage (CCS) is a vital technology towards low-carbon energy resources and the mitigation of global warming trends induced by rising CO2 levels in the atmosphere. The East Irish Sea Basin (EISB) is a key area for CCS in the western UK, having high CO2 storage potentials in explored hydrocarbon fields and in saline aquifers within the Permo-Triassic Sherwood Sandstone Formation. However, the theoretical storage potential of the EISB could be poorly estimated as the reservoir-prone Lower Permian formations are not considered in detail by current estimations. This work aims to fill this gap, focusing on the characterisation of the Lower Permian Collyhurst Sandstone Formation as a viable storage unit. The potential for CO2 storage is estimated as the total volume/area of suitable closures that are isolated by structural traps, occurring at depths suitable for CO2 injection and containment (>800m). Detailed structural and stratigraphic interpretations were made using 3D seismic data to assess the storage potential of the Collyhurst Sandstone Formation in the southern EISB. The basin strata is compartmentalised by numerous N-S trending faults. A higher degree of compartmentalisation occurs within regional anticlines where elongated tilted blocks are observed, bound by predominantly west-dipping faults that induce a variable offset of the Collyhurst Sandstone strata. Contrastingly, higher lateral continuity of this formation is observed within graben basins were faults are less frequent and with minor offset, thus potentially creating larger storage closures. Fault dip orientation in the grabens is variable, with west and east dipping faults occurring as a function of large east-dipping listric faults. This study was complemented by the stress modelling of the interpreted faults in order to assess the risk of CO2 leakage. Analysis of borehole breakouts observed in four approximately vertical wells in the EISB suggest a maximum horizontal stress

  5. Mercury isotopic composition of hydrothermal systems in the Yellowstone Plateau volcanic field and Guaymas Basin sea-floor rift

    USGS Publications Warehouse

    Sherman, L.S.; Blum, J.D.; Nordstrom, D.K.; McCleskey, R.B.; Barkay, T.; Vetriani, C.

    2009-01-01

    To characterize mercury (Hg) isotopes and isotopic fractionation in hydrothermal systems we analyzed fluid and precipitate samples from hot springs in the Yellowstone Plateau volcanic field and vent chimney samples from the Guaymas Basin sea-floor rift. These samples provide an initial indication of the variability in Hg isotopic composition among marine and continental hydrothermal systems that are controlled predominantly by mantle-derived magmas. Fluid samples from Ojo Caliente hot spring in Yellowstone range in δ202Hg from - 1.02‰ to 0.58‰ (± 0.11‰, 2SD) and solid precipitate samples from Guaymas Basin range in δ202Hg from - 0.37‰ to - 0.01‰ (± 0.14‰, 2SD). Fluid samples from Ojo Caliente display mass-dependent fractionation (MDF) of Hg from the vent (δ202Hg = 0.10‰ ± 0.11‰, 2SD) to the end of the outflow channel (&delta202Hg = 0.58‰ ± 0.11‰, 2SD) in conjunction with a decrease in Hg concentration from 46.6pg/g to 20.0pg/g. Although a small amount of Hg is lost from the fluids due to co-precipitation with siliceous sinter, we infer that the majority of the observed MDF and Hg loss from waters in Ojo Caliente is due to volatilization of Hg0(aq) to Hg0(g) and the preferential loss of Hg with a lower δ202Hg value to the atmosphere. A small amount of mass-independent fractionation (MIF) was observed in all samples from Ojo Caliente (Δ199Hg = 0.13‰ ±1 0.06‰, 2SD) but no significant MIF was measured in the sea-floor rift samples from Guaymas Basin. This study demonstrates that several different hydrothermal processes fractionate Hg isotopes and that Hg isotopes may be used to better understand these processes.

  6. Late Pleistocene evolution of the Rhine-Meuse system in the southern North Sea basin: imprints of climate change, sea-level oscillation and glacio-isostacy

    NASA Astrophysics Data System (ADS)

    Busschers, F. S.; Kasse, C.; van Balen, R. T.; Vandenberghe, J.; Cohen, K. M.; Weerts, H. J. T.; Wallinga, J.; Johns, C.; Cleveringa, P.; Bunnik, F. P. M.

    2007-12-01

    High-resolution continuous core material, geophysical measurements, and hundreds of archived core descriptions enabled to identify 13 Late Pleistocene Rhine-Meuse sedimentary units in the infill of the southern part of the North Sea basin (the Netherlands, northwestern Europe). This sediment record and a large set of Optical Stimulated Luminescence dates, 14C dates and biostratigraphical data, allowed to establish detailed relationships between climate change, sea-level oscillation, glaciation history and the sedimentary development of the Rhine fluvial system during the last glacial cycle (Marine Isotope Stages 5e-2, Eemian-Weichselian). A well-preserved Eemian sediment record was encountered as the infill of a Late Saalian (MIS6) subglacial basin. Part of this record reflects groundwater rise controlled (fine-grained) sedimentation as a result of postglacial (early) Eemian sea-level rise. It shows strong analogy to developments known from the Holocene Rhine-Meuse delta. Outside of the glacial depressions near coastal deposits are only fragmentarily preserved. The Early Glacial Rhine sediment record is dominated by organic debris and peat layers, marking landscape stability and low fluvial activity. Part of this record may have been formed under near coastal conditions. Significant amounts of reworked marine biomarkers in the lag-deposits of Early Pleniglacial (MIS4) fluvial systems indicate that this period is characterized by extensive reworking of older (MIS5) near-coastal sediments. Despite the marked Early Pleniglacial climatic cooling, input of new sediment from the drainage basin was relatively low, a feature that is related to the presence of regolith protective relic soil complexes in the basin. During the early Middle Pleniglacial, a major Rhine avulsion indicates the system was in an aggrading mode and that sediment supply into the lower reaches of the Rhine had strongly increased. This increase in sediment supply coincided with the timing of major

  7. Salish Sea

    EPA Pesticide Factsheets

    The Health of the Salish Sea Report is a collaboration between EPA and Environment Canada to examine the health of the Salish Sea ecosystem in Washington and British Columbia, encompassing the Puget Sound and Georgia Basin.

  8. Low Bacterial Diversity and High Labile Organic Matter Concentrations in the Sediments of the Medee Deep-Sea Hypersaline Anoxic Basin

    PubMed Central

    Akoumianaki, Ioanna; Nomaki, Hidetaka; Pachiadaki, Maria; Kormas, Konstantinos Ar.; Kitazato, Hiroshi; Tokuyama, Hidekazu

    2012-01-01

    Studies in the center and margin of the Medee Basin, a Mediterranean deep-sea hypersaline anoxic basin, and at a reference site during Penelope cruise (2007), revealed the existence of a 7 m-thick halocline, with high salinity (328 psu), and high sedimentary organic carbon and biopolymer concentrations. The 194 16S rRNA sequences retrieved were grouped into 118 unique phylotypes. Pseudomonas gessardii, dominated in the center, while 33 phylotypes were detected at the margin and 73 at the reference site. The study suggested conditions hostile to bacteria in the sediments of the Medee Basin and preservation of sedimentary labile organic matter. PMID:22504432

  9. Subduction- vs- Intraplate-Type Melt Migration in the Alboran Lithospheric Mantle: Insights From the Tallante Xenoliths (Betic Cordillera, SE Spain)

    NASA Astrophysics Data System (ADS)

    Rampone, E.; Vissers, R. L.; Poggio, M.; Scambelluri, M.; Zanetti, A.

    2008-12-01

    The Alboran Sea region has been affected since the late Oligocene by widespread eruption of tholeiitic to calc-alkaline magmas followed by Late Neogene alkaline basalts. These magmatic episodes are related to Neogene lithospheric extension beneath the Alboran domain, as a consequence of slab roll-back. According to recent models, subduction of oceanic lithosphere caused continental-edge delamination of subcontinental lithosphere, associated with upwelling of plume-type mantle sources. The Alboran lithospheric mantle thus constitutes a unique setting to investigate the effects of subduction- and intraplate-type metasomatism. Here we present a microstructural and geochemical study of mantle xenoliths from the Cabezo Tallante Late Neogene alkaline volcanic center (SE Spain). These xenoliths record multiple episodes of reactive porous melt percolation, and melt entrapment, tracking their progressive extension-related uplift from P > 20 Kb to 7-10 Kb. This is documented by i) crystallization of undeformed olivine replacing pyroxene porphyroclasts, and unstrained opx overgrowing undeformed olivine and pyroxene porphyroclasts, in porphyroclastic spinel peridotites, ii) development of annealed equigranular structure, likely enhanced by heating during melt percolation, iii) crystallization of interstitial (plag±ol±opx) aggregates between mantle minerals in porphyroclastic and equigranular xenoliths. Cpx in equigranular peridotites have smooth trace element spectra characterized by slight LREE depletion; computed equilibrium liquids have a tholeiitic-transitional affinity. Diffuse melt percolation was followed by intrusion of melts with distinct chemical affinity. The first event is documented by the intrusion of cm-sized gabbronoritic veins, showing a fine-grained opx reaction rim against the host peridotite. Similar gabbronoritic lithotypes were previously documented and ascribed to slab-derived melts. A quite remarkable textural feature in these veins is the occurrence

  10. Ichnological trends along an open-water transect across a large marginal-marine epicontinental basin, the modern Baltic Sea

    NASA Astrophysics Data System (ADS)

    Virtasalo, Joonas J.; Bonsdorff, Erik; Moros, Matthias; Kabel, Karoline; Kotilainen, Aarno T.; Ryabchuk, Daria; Kallonen, Aki; Hämäläinen, Keijo

    2011-11-01

    Late Holocene sediments in the Baltic Sea provide an opportunity to study lateral changes in the assemblages of identifiable biogenic sedimentary structures (ichnofossils) in a large, high-latitude semi-enclosed sea with instrumentally determined gradients in biodiversity and environmental factors such as salinity and oxygen availability. Integrated sedimentological and ichnological analysis is carried out on 6 long cores collected along an open-sea, declining salinity transect across the basin. Muddy sediments in euhaline (Kattegat) and polyhaline (Mecklenburg Bight) sites are characterized by the archetypal Cruziana Ichnofacies, portrayed by subsurface deposit-feeding structures ( Scolicia and Planolites), surface deposit-feeding structures ( Skolithos), and structures that reflect both these feeding strategies ( Palaeophycus, Arenicolites/ Polykladichnus and unnamed biodeformational structures produced by bivalves). The ichnofossils are tiered to 3 levels. The Cruziana Ichnofacies is impoverished in the higher mesohaline Arkona Basin and even more so with declining salinity farther inland. The deepest, oxygen-restricted study sites (Gotland Deep and the western Gulf of Finland) below a permanent halocline are characterized by very small and shallow deposit-feeding structures ( Planolites and rare flat Arenicolites/ Polykladichnus), and poorly developed tiering. The nearly freshwater eastern Gulf of Finland is characterized by the Cenozoic archetypal Mermia Ichnofacies, dominated by narrow and shallow subsurface and surface deposit-feeding structures ( Planolites and flat Arenicolites/ Polykladichnus). Large Planolites (3-7 mm in diameter) at this site are untypical of Mermia Ichnofacies assemblages. These results confirm the earlier observations that marine forms dominate brackish-water ichnoassemblages, with the ichnofossil size and diversity decreasing with declining salinity. The results also confirm the predicted decreases in the ichnofossil size and

  11. The interplay between tectonics, sediment dynamics and gateways evolution in the Danube system from the Pannonian Basin to the western Black Sea.

    PubMed

    Matenco, Liviu; Munteanu, Ioan; ter Borgh, Marten; Stanica, Adrian; Tilita, Marius; Lericolais, Gilles; Dinu, Corneliu; Oaie, Gheorghe

    2016-02-01

    Understanding the natural evolution of a river-delta-sea system is important to develop a strong scientific basis for efficient integrated management plans. The distribution of sediment fluxes is linked with the natural connection between sediment source areas situated in uplifting mountain chains and deposition in plains, deltas and, ultimately, in the capturing oceans and seas. The Danube River-western Black Sea is one of the most active European systems in terms of sediment re-distribution that poses significant societal challenges. We aim to derive the tectonic and sedimentological background of human-induced changes in this system and discuss their interplay. This is obtained by analysing the tectonic and associated vertical movements, the evolution of relevant basins and the key events affecting sediment routing and deposition. The analysis of the main source and sink areas is focused in particular on the Miocene evolution of the Carpatho-Balkanides, Dinarides and their sedimentary basins including the western Black Sea. The vertical movements of mountains chains created the main moments of basin connectivity observed in the Danube system. Their timing and effects are observed in sediments deposited in the vicinity of gateways, such as the transition between the Pannonian/Transylvanian and Dacian basins and between the Dacian Basin and western Black Sea. The results demonstrate the importance of understanding threshold conditions driving rapid basins connectivity changes superposed over the longer time scale of tectonic-induced vertical movements associated with background erosion and sedimentation. The spatial and temporal scale of such processes is contrastingly different and challenging. The long-term patterns interact with recent or anthropogenic induced modifications in the natural system and may result in rapid changes at threshold conditions that can be quantified and predicted. Their understanding is critical because of frequent occurrence during

  12. Recurrent Mass-wasting in Sørvestsnaget Basin, SW Barents Sea: A test of multiple hypotheses

    NASA Astrophysics Data System (ADS)

    Omosanya, K. O.; Harishidayat, D.; Lolita, M.; Johansen, S. E.; Abrahamson, P.

    2015-12-01

    Mass-wasting on the NE Atlantic margin is commonly attributed to Cenozoic glaciations. Using high-quality and high-resolution seismic dataset, this study investigates the types and mechanisms driving mass-wasting in the Sørvestsnaget Basin, Southwestern Barents. Seven mass-transport deposits (MTDs) ranging in age from Late Miocene to Holocene are interpreted on seismic profiles. The MTDs are vertically stacked from about 1900 ms TWTT to the present seabed. MTD 5 (area ca.1.22 x 103 km2, volume ca.3.4 x 103 km3) is the largest deposit in the study area and is composed largely of debrites and rafted blocks underlain by thin layers of hemipelagic sediments. Miocene and Early Pliocene MTDs in the basin demonstrate tendency for initial translation through canyons and channels. The youngest MTDs in the area are composed of glacigenic sediments remobilized by ice streams during Late Neogene and Quaternary glaciations. In the southern part of the study area, deep-water sediments fed through V-shaped canyons and channels are widespread signifying the Stappen High as the main sediment source area prior to the Late Pliocene. The prevalence of shallow marine successions in the northern part of the study area is linked to the southwesterly propagation of the shelf break from Miocene to Recent times. In this study, the shelf break trajectory is important for reconstructing paleo-sediment routes and dispersal pattern. The older non-glacial MTDs are separated farther from their paleo-shelf break. Mass-wasting is a recurrent process in the Sørvestsnaget Basin. Triggering mechanisms for slope failure in the basin may include increased pore pressure as a result of sea level fall and high sedimentation rate, over-steepened slope, glaciation, volcanism, and gas hydrate dissociation. Mass-wasting in the study area occurred through progressive, retrogressive and whole body or coherent downslope failures.

  13. The geochemistry characteristic and dating of cold seepage carbonates of the Pearl River Mouth Basin, eastern of South China Sea

    NASA Astrophysics Data System (ADS)

    Fang, Yunxin; Fu, Shaoying

    2015-04-01

    Cold seepage carbonates are usually formed by the interaction of methane oxidizing archaea, sulfate reducing bacteria and cold seepage which contain abundant venting hydrocarbon gases. The presence of cold seepage carbonates on the seabed is one of the evidences that the area exist venting hydrocarbon gases, which are usually result by the dissociation of gas hydrate. The cold seepage property and fluid flow rate can influence the oxidation-deoxidation environment of the bottom water and sediment. Many previous studies focused on the mineral composition, microstructure, elemental composition, isotope composition of the cold seepage carbonates and isotopic dating for the cold seepage carbonates. The isotopic dating for the cold seepage carbonates can provide the information of the gas hydrate formation and dissociation in some area of the South China Sea. High precision TIMS-U dating and 14C dating are used as routine method for the dating of the Quaternary carbonates and fossils. The cold seepage carbonates in the study include the samples collected by ROV on the seabed and the drilling for gas hydrate in the Pearl River Mouth Basin, eastern of the South China Sea. The authigenic carbonate occurred in different depth in the A, B and C drilling site. They may be represent different events of gas hydrate formation and dissociation in the Quaternary. The dating study for all the cold seepage carbonates can provide the relative accurate eras of the gas hydrate dissociation events in certain area of the South China Sea.

  14. Sea surface temperature and salinity variability in the Levantine Basin during the last decade, 1996 to 2006

    NASA Astrophysics Data System (ADS)

    Samuel-Rhoads, Y.; Iona, S.; Zodiatis, G.; Hayes, D.; Gertman, I.; Georgiou, G.

    2009-04-01

    The reality of global warming since the industrial era is manifested in part by changes in global surface temperatures. Regional temperature increases have also been reported in the Mediterranean Sea, where sea surface temperatures (SSTs) across the Mediterranean as a whole, have been rising about twice as much as those of the global oceans. Here we analyse and compare satellite remote sensing SST data with in-situ data for the period 1996-2006 in the Levantine Basin. Satellite data were collected by the NOAA/NASA Advanced Very High Resolution Radiometers (AVHRR) and processed by the SST Pathfinder program. For our analyses we obtained monthly averaged Level 3, version 5.0, global SST data from the nighttime pass of the satellite at a 4-km resolution and an equal-angle grid of 8192 pixels/360° from January 1996 through December 2006. Monthly quality control flag files for the SST data were also obtained from January 1996 through December 2006 from the same source. Further, 23,000 vertical profiles of temperature and salinity from 160 oceanographic cruises were extracted from the MEDAR/MEDATLAS, WDC-A and the Coriolis databases for the period 1996-2006, in order to study the interannual variability in this basin at the surface layer (0-10m). Annual gridded fields were calculated by averaging the top 10m of the in-situ data, and then interpolated horizontally by the Variational Inverse Method (VIM) and a finite element technique using the SeaDataNet Geostatistical Analysis Tool - DIVA. Satellite SST data indicate that over the last 11 years a general warming has occurred over the Levantine Basin, both at interannual and seasonal time scales. This increase in average SSTs is also seen in the seasonal averages, especially during the spring and summer. Moreover, the averages from the top 10m of in-situ SST, using the relevant data from the above oceanographic databases, show a correlation with the satellite SST data particularly at seasonal time scales. Satellite

  15. Lithospheric deformation in the Africa-Iberia plate boundary: Improved neotectonic modeling testing a basal-driven Alboran plate

    NASA Astrophysics Data System (ADS)

    Neres, M.; Carafa, M. M. C.; Fernandes, R. M. S.; Matias, L.; Duarte, J. C.; Barba, S.; Terrinha, P.

    2016-09-01

    We present an improved neotectonic numerical model of the complex NW Africa-SW Eurasia plate boundary segment that runs from west to east along the Gloria Fault up to the northern Algerian margin. We model the surface velocity field and the ongoing lithospheric deformation using the most recent version of the thin-shell code SHELLS and updated lithospheric model and fault map of the region. To check the presence versus the absence of an independently driven Alboran domain, we develop two alternative plate models: one does not include an Alboran plate; another includes it and determines the basal shear tractions necessary to drive it with known velocities. We also compare two alternative sets of Africa-Eurasia velocity boundary conditions, corresponding to geodetic and geological-scale averages of plate motion. Finally, we perform an extensive parametric study of fault friction coefficient, trench resistance, and velocities imposed in Alboran nodes. The final run comprises 5240 experiments, each scored to geodetic velocities (estimated for 250 stations and here provided), stress direction data, and seismic strain rates. The model with the least discrepancy to the data includes the Alboran plate driven by a basal WSW directed shear traction, slightly oblique to the westward direction of Alboran motion. We provide estimates of long-term strain rates and slip rates for the modeled faults, which can be useful for further hazard studies. Our results support that a mechanism additional to the Africa-Eurasia convergence is required to drive the Alboran domain, which can be related to subduction processes occurring within the mantle.

  16. Responses of a deltaic system to minor relative sea level variations (Middle Jurassic, Cleveland basin, England): Consequences on the reservoir geometry

    SciTech Connect

    Eschard, R.; Ravenne, C. )

    1990-05-01

    In the Middle Jurassic series of the Cleveland basin (England), an accurate three-dimensional reconstruction of depositional sequences from outcrops, cores, and wireline logs show that minor sea level variations control the evolution of a deltaic system. Because of low subsidence and sediment supply rates, rapid sea level rises induce several landward shifts of the shoreline, whereas minor sea level drops produce the incision of small paleovalleys. The deltaic series, 200 m thick at the basin depocenter, are subdivided into five depositional sequences. During the first two sequences, the sediment supply rate exceeds the relative sea level rate and the delta progrades. The delta aggrades during the third depositional sequence and retrogrades in the fourth depositional sequence when the relative sea level rise rate balances then exceeds the sediment supply rate. Finally, a relative sea level drop induces the incision of a paleovalley progressively infilled during the following sea level rise. Several orders of bathymetric cycles are deduced from detailed correlations of the unconformities and from the comparison of the vertical facies succession between low and high subsiding areas. The general evolution of the delta is related to a 5-m.y. bathymetric cycle due to a eustatic sea level rise and fall. Pne to 3-m.y. bathymetric cycles control the main aggradation patterns of the delta. These patterns are related to third-order eustatic cycles or to local tectonic events. Less than 0.5 m.y. bathymetric cycles are registrated by parasequences or minor depositional sequences which are correlated all over the basin. The controlling parameters of the sequences are discussed. Minor bathymetric cycles (0.2 m.y.) reflect small-scale sea level oscillations or autocyclic evolution of the sedimentary bodies. The authors focus on the reservoir geometry within each bathymetric cycle.

  17. Role of sea-level change in deep water deposition along a carbonate shelf margin, Early and Middle Permian, Delaware Basin: implications for reservoir characterization

    NASA Astrophysics Data System (ADS)

    Li, Shunli; Yu, Xinghe; Li, Shengli; Giles, Katherine A.

    2015-04-01

    The architecture and sedimentary characteristics of deep water deposition can reflect influences of sea-level change on depositional processes on the shelf edge, slope, and basin floor. Outcrops of the northern slope and basin floor of the Delaware Basin in west Texas are progressively exposed due to canyon incision and road cutting. The outcrops in the Delaware Basin were measured to characterize gravity flow deposits in deep water of the basin. Subsurface data from the East Ford and Red Tank fields in the central and northeastern Delaware Basin were used to study reservoir architectures and properties. Depositional models of deep water gravity flows at different stages of sea-level change were constructed on the basis of outcrop and subsurface data. In the falling-stage system tracts, sandy debris with collapses of reef carbonates are deposited on the slope, and high-density turbidites on the slope toe and basin floor. In the low-stand system tracts, deep water fans that consist of mixed sand/mud facies on the basin floor are comprised of high- to low-density turbidites. In the transgression and high-stand system tracts, channel-levee systems and elongate lobes of mud-rich calciturbidite deposits formed as a result of sea level rise and scarcity of sandy sediment supply. For the reservoir architecture, the fan-like debris and high-density turbidites show high net-to-gross ratio of 62 %, which indicates the sandiest reservoirs for hydrocarbon accumulation. Lobe-like deep water fans with net-to-gross ratio of 57 % facilitate the formation of high quality sandy reservoirs. The channel-levee systems with muddy calciturbidites have low net-to-gross ratio of 30 %.

  18. Nearshore half-grabens as analogues for offshore, early Carboniferous rift basins along the SW Barents Sea Margin

    NASA Astrophysics Data System (ADS)

    Koehl, Jean-Baptiste; Bergh, Steffen G.; Indrevær, Kjetil; Lea, Halldis; Bergø, Espen; Henningsen, Tormod; Forthun, Tore; Faleide, Jan-Inge

    2016-04-01

    The present study focuses on the onshore-offshore correlation of brittle faults along the SW Barents Sea Margin, northern Norway. Several studies indicate that the SW Barents Sea Margin experienced a pulse of extensional deformation in the Late Devonian?-early Carboniferous, shortly after the Caledonian contractional deformation ended. The formation of major brittle faults and associated offshore basins that represent targets for hydrocarbon exploration, such as the NE-SW trending Nordkapp Basin, are thought to have initiated during this rifting event. Half-graben structures similar in shape and orientation to the southern segment of the Nordkapp Basin have been identified on the Finnmark Platform and in nearshore areas in coastal Finnmark, northern Norway. Although relatively smaller, these half-graben structures display the same asymmetric, sigma-shaped to triangular architecture in map view as the Nordkapp Basin and also initiated in the earliest Carboniferous, as confirmed by fossiliferous assemblages from shallow cores. The triangular shape of these half-graben structures is related to the presence of possible fault segments of the Trollfjord-Komagelv Fault Zone that trend WNW-ESE and partly truncate the NE-SW trending, sometimes arcuate, extensional brittle faults that bound the half-graben structures. High-resolution bathymetry data show that these half-graben structures internally display minor, NE-SW trending brittle faults and relatively high seafloor relief, thus possible fault displacement, at the intersection between these minor faults and the major, arcuate bounding faults. Microstructural analysis of fault-rocks in nearby onshore fault zones showed multiple generations of cataclasite, suggesting several episodes of faulting in the region. A major goal for future work will be to constrain the exact timing of the faulting event(s) with K/Ar radiometric dating of onshore fault-rocks. This may help estimating the timing of potential fluid migration

  19. Cenozoic tectonic evolution and petroleum exploration in Perl River Mouth basin, South China Sea

    SciTech Connect

    Chi Yukun; Xu Shice )

    1990-06-01

    The Pearl River Mouth basin is a large Cenozoic continental margin basin that is rich in hydrocarbon potential. Fluvial-lake sequences were deposited before Oligocene, but all were covered by Miocene marine clastic and carbonate rocks. Both paleo-Pearl River delta system and reef/bank carbonate system were widely developed. At the early stage of the evolution, two subsidence belts and one uplift between them distributed in NE regional direction; grabens occurred in the north belt and depressions in the south belt. Tectonic movement was stronger in the east than the west. The main production zones have been drilled both in Miocene sandstone and carbonate rocks. As the exploration activities are developing, the basin will be one of the most significant China offshore oil production areas.

  20. Lithospheric-scale effects of a subduction-driven Alboran plate: improved neotectonic modeling

    NASA Astrophysics Data System (ADS)

    Neres, Marta; Carafa, Michele; Terrinha, Pedro; Fernandes, Rui; Matias, Luis; Duarte, João; Barba, Salvatore

    2016-04-01

    The presence of a subducted slab under the Gibraltar arc is now widely accepted. However, discussion still remains on whether subduction is active and what is its influence in the lithospheric processes, in particular in the observed geodesy, deformation rates and seismicity. Aiming at bringing new insights into the discussion, we have performed a neotectonic numerical study of a segment of the Africa-Eurasia plate boundary, from the Gloria fault to the Northern Algerian margin. Specifically, we have tested the effect of including or excluding an independently driven Alboran plate, i.e. testing active subduction versus inactive subduction (2plates versus 3plates scenarios). We used the dynamic code SHELLS (Bird et al., 2008) to model the surface velocity field and the ongoing deformation, using a new up-to-date simplified tectonic map of the region, new available lithospheric data and boundary conditions determined from two alternative Africa-Eurasia angular velocities, respectively: SEGAL2013, a new pole based on stable Africa and stable Eurasia gps data (last decades); and MORVEL, a geological-scale pole (3.16 Ma). We also extensively studied the variation within the parametric space of fault friction coefficient, subduction resistance and surface velocities imposed to the Alboran plate. The final run comprised a total of 5240 experiments, and each generated model was scored against geodetic velocities, stress direction data and seismic strain rates. The preferred model corresponds to the 3plates scenario, SEGAL2013 pole and fault friction of 0.225, with scoring results: gps misfit of 0.78 mm/yr; SHmax misfit of 13.6° and correlation with seismic strain rate of 0.62, significantly better than previous models. We present predicted fault slip rates for the recognized active structures and off-faults permanent strain rates, which can be used for seismic and tsunami hazard calculations (the initial motivation for this work was contributing for calculation of

  1. Late Pliocene and early Pleistocene sea-level timing and amplitudes derived from fossil ostracod assemblages: Canterbury Basin, New Zealand

    NASA Astrophysics Data System (ADS)

    Nakamura, M.; Kusunoki, S.; Yamada, K.; Hoyanagi, K.

    2013-12-01

    the Canterbury Basin sequences responded to global climate change. However, comparison with sea-level amplitude estimates from the North Island of New Zealand (Naish, 1997) suggests that sea-level amplitudes increased in the Canterbury Basin 200 thousand years earlier than in the North Island.

  2. Trend Analysis of Nitrogen Deposition to Baltic Sea and its sub basins

    NASA Astrophysics Data System (ADS)

    Semeena, V. S.; Jerzy, Bartnicki

    2009-04-01

    Since the beginning of last century, Baltic Sea has changed from a clear-water sea into a eutrophic marine environment. Eutrophication is the major problem in the Baltic Sea. Excessive nitrogen and phosphorus loads coming from land-based sources within and outside the catchment area of the bordering countries of the Baltic Sea are the main cause of the eutrophication in the sea. Even though a major part of nitrogen(75%) and phosphorus load(95%) enter the sea via rivers or as water-born discharges, 25% of the nitrogen load comes as atmospheric deposition. Numerical models are the best tools to measure atmospheric deposition into sea waters. We have used the latest version of the Unified EMEP model - which has been developed at the EMEP/MSC-W (Meteorological Synthesizing Centre - West of EMEP) for simulating atmospheric transport and deposition of acidifying and eutrophying compounds as well as photo-oxidants in Europe- to study the trends in atmospheric deposition of nitrogen into Baltic Sea for the period 1995-2006. The model domain covers Europe and the Atlantic Ocean. The model grid (of the size 170×133) has a horizontal resolution of 50 km at 60o N, which is consistent with the resolution of emission data reported to CLRTAP. Approximately 10 of these layers are placed below 2 km to obtain high resolution of the boundary layer which is of special importance to the long range transport of air pollution. EMEP model has been thouroughly validated (Fagerli et.al.[1], Simpson et.al.[2], Simpson et.al.[3] ) The contribution of deposition of nitrogen into Baltic Sea from each of the bordering countries of the Baltic Sea and the deposition trends for the period 1995-2006 has been analysed and the results will be presented. References: [1]. Fagerli H., Simpson D. and Aas W.: Model performance for sulphur and nitrogen compounds for the period 1980 to 2000. [In:] L. Tarraśon, (editor), Transboundary Acidification, Eutrophication and Ground Level Ozone in Europe. EMEP

  3. Seismic Reflection Moho Structure of Southwest Sub-basin of South China Sea and Implications for Continental Break-up and Seafloor Spreading Mechanisms

    NASA Astrophysics Data System (ADS)

    Zhang, Jinchang; Yan, Pin

    2016-04-01

    Across-basin Moho structure of South China Sea is important for understanding crustal evolution mechanisms of both continental break-up and seafloor spreading processes. Among all the basins in South China Sea, southwest sub-basin opened up the latest and has the closest continental margins, making it the best to study the across-basin structure. Multichannel seismic (MCS) reflection data of NH973-1 line that crosses southwest sub-basin in NW-SE direction were reprocessed in order to image Moho structure. In MCS data Moho reflectors are observed in places, which were not revealed in prior researches. The Moho generally shows symmetric structure on the both sides of the central rift valley. Beneath the oceanic crust in the middle of the basin, the Moho is ~2 seconds depth in two-way travel time (TWTT), which corresponds to ~7 km depth, showing normal oceanic crustal accretion during the seafloor spreading process. When getting close to continent-ocean boundary (COB), the Moho becomes shallow to <1 second depth in TWTT (~3.5 km), implying strongly crustal thinning. At south COB, the Moho depth almost reaches zero, which implies nearly no crust exists and probably the upper mantle could be exhumed. In addition, two low-angle, deep-penetrating normal faults are observed at south COB. The faults cut across the Moho into the upper mantle, which may have been caused by lithospheric hyper-stretching at COB during the continental break-up process.

  4. The formation and inversion of the western Greater Caucasus Basin and the uplift of the western Greater Caucasus: Implications for the wider Black Sea region

    NASA Astrophysics Data System (ADS)

    Vincent, Stephen J.; Braham, William; Lavrishchev, Vladimir A.; Maynard, James R.; Harland, Melise

    2016-12-01

    The western Greater Caucasus formed by the tectonic inversion of the western strand of the Greater Caucasus Basin, a Mesozoic rift that opened at the southern margin of Laurasia. Subsidence analysis indicates that the main phase of rifting occurred during the Aalenian to Bajocian synchronous with that in the eastern Alborz and, possibly, the South Caspian Basin. Secondary episodes of subsidence during the late Tithonian to Berriasian and Hauterivian to early Aptian are tentatively linked to initial rifting within the western, and possibly eastern, Black Sea and during the late Campanian to Danian to the opening of the eastern Black Sea. Initial uplift, subaerial exposure, and sediment derivation from the western Greater Caucasus occurred at the Eocene-Oligocene transition. Oligocene and younger sediments on the southern margin of the former basin were derived from the inverting basin and uplifted parts of its northern margin, indicating that the western Greater Caucasus Basin had closed by this time. A predominance of pollen representing a montane forest environment (dominated by Pinacean pollen) within these sediments suggests that the uplifting Caucasian hinterland had a paleoaltitude of around 2 km from early Oligocene time. The closure of the western Greater Caucasus Basin and significant uplift of the range at approximately 34 Ma is earlier than stated in many studies and needs to be incorporated into geodynamic models for the Arabia-Eurasia region.

  5. Modelling of oil spills in confined maritime basins: The case for early response in the Eastern Mediterranean Sea.

    PubMed

    Alves, Tiago M; Kokinou, Eleni; Zodiatis, George; Lardner, Robin; Panagiotakis, Costas; Radhakrishnan, Hari

    2015-11-01

    Oil spill models are combined with bathymetric, meteorological, oceanographic, and geomorphological data to model a series of oil spill accidents in the Eastern Mediterranean Sea. A total of 104 oil spill simulations, computed for 11 different locations in the Levantine Basin, show that oil slicks will reach the coast of Cyprus in four (4) to seven (7) days in summer conditions. Oil slick trajectories are controlled by prevailing winds and current eddies. Based on these results, we support the use of chemical dispersants in the very few hours after large accidental oil spills. As a corollary, we show shoreline susceptibility to vary depending on: a) differences in coastline morphology and exposure to wave action, b) the existence of uplifted wave-cut platforms, coastal lagoons and pools, and c) the presence of tourist and protected environmental areas. Mitigation work should take into account the relatively high susceptibility of parts of the Eastern Mediterranean.

  6. Petrology of basaltic sills from ocean drilling program sites 794 and 797 in the Yamato Basin of the Japan Sea

    NASA Technical Reports Server (NTRS)

    Thy, P.

    1992-01-01

    The basaltic sills from ocean drilling program sites 794 and 797 in the Yamato Basin of the Japan Sea are characterized petrographically on the basis of a detailed study of the composition of relict phenocryst and groundmass phases. The systematic variation in the rock compositions is discussed. Results of 1-atm melting experiments on a relatively primitive basalt from site 797 are reported. The sills are found to constitute two distinct groups of suites: primitive, olivine-bearing suites with low potassium and primitive olivine-bearing to evolved, olivine-free suites with relatively high potassium. A pseudoinvariant reaction relationship between olivine and augite and magnetite is inferred. Complex magmatic and tectonic evolutions in the region, perhaps reflecting a transitional stage between subduction zone activity and back arc spreading, are suggested.

  7. Use of GOES, SSM/I, TRMM Satellite Measurements Estimating Water Budget Variations in Gulf of Mexico - Caribbean Sea Basins

    NASA Technical Reports Server (NTRS)

    Smith, Eric A.

    2004-01-01

    This study presents results from a multi-satellite/multi-sensor retrieval system designed to obtain the atmospheric water budget over the open ocean. A combination of 3ourly-sampled monthly datasets derived from the GOES-8 5-channel Imager, the TRMM TMI radiometer, and the DMSP 7-channel passive microwave radiometers (SSM/I) have been acquired for the combined Gulf of Mexico-Caribbean Sea basin. Whereas the methodology has been tested over this basin, the retrieval system is designed for portability to any open-ocean region. Algorithm modules using the different datasets to retrieve individual geophysical parameters needed in the water budget equation are designed in a manner that takes advantage of the high temporal resolution of the GOES-8 measurements, as well as the physical relationships inherent to the TRMM and SSM/I passive microwave measurements in conjunction with water vapor, cloud liquid water, and rainfall. The methodology consists of retrieving the precipitation, surface evaporation, and vapor-cloud water storage terms in the atmospheric water balance equation from satellite techniques, with the water vapor advection term being obtained as the residue needed for balance. Thus, the intent is to develop a purely satellite-based method for obtaining the full set of terms in the atmospheric water budget equation without requiring in situ sounding information on the wind profile. The algorithm is validated by cross-checking all the algorithm components through multiple- algorithm retrieval intercomparisons. A further check on the validation is obtained by directly comparing water vapor transports into the targeted basin diagnosed from the satellite algorithms to those obtained observationally from a network of land-based upper air stations that nearly uniformly surround the basin, although it is fair to say that these checks are more effective m identifying problems in estimating vapor transports from a leaky operational radiosonde network than in verifying

  8. Monthly-Diurnal Water Budget Variability Over Gulf of Mexico-Caribbean Sea Basin from Satellite Observations

    NASA Technical Reports Server (NTRS)

    Smith, E. A.; Santos, P.

    2006-01-01

    This study presents results from a multi-satellite/multi-sensor retrieval system design d to obtain the atmospheric water budget over the open ocean. A combination of hourly-sampled monthly datasets derived from the GOES-8 5-channel Imager, the TRMM TMI radiometer, and the DMSP 7-channel passive microwave radiometers (SSM/I) have been acquired for the combined Gulf of Mexico-Caribbean Sea basin. Whereas the methodology has been tested over this basin, the retrieval system is designed for portability to any open-ocean region. Algorithm modules using the different datasets to retrieve individual geophysical parameters needed in the water budget equation are designed in a manner that takes advantage of the high temporal resolution of the GOES-8 measurements, as well as the physical relationships inherent to the TRMM and SSM/I passive microwave measurements in conjunction with water vapor, cloud liquid water, and rainfall. The methodology consists of retrieving the precipitation, surface evaporation, and vapor-cloud water storage terms in the atmospheric water balance equation from satellite techniques, with the water vapor advection term being obtained as the residue needed for balance. Thus, the intent is to develop a purely satellite-based method for obtaining the full set of terms in the atmospheric water budget equation without requiring in situ sounding information on the wind profile. The algorithm is validated by cross-checking all the algorithm components through multiple-algorithm retrieval intercomparisons. A further check on the validation is obtained by directly comparing water vapor transports into the targeted basin diagnosed from the satellite algorithms to those obtained observationally from a network of land-based upper air stations that nearly uniformly surround the basin, although it is fair to say that these checks are more effective in identifying problems in estimating vapor transports from a "leaky" operational radiosonde network than in

  9. Aminostratigraphy of Middle and Late Pleistocene deposits in The Netherlands and the southern part of the North Sea Basin

    NASA Astrophysics Data System (ADS)

    Meijer, T.; Cleveringa, P.

    2009-09-01

    A review of all available amino acid racemization D (alloisoleucine)/L (isoleucine) data from the whole shell of four molluscan species from Late and late Middle Pleistocene deposits of the Netherlands is presented. The data allow the distinction of 5 aminostratigraphical units, NAZ (Netherlands Amino Zone) A-E, each representing a temperate stage. The zones are correlated with marine isotope stages 1, 5e, 7, 9, and 11 respectively. Apart from NAZ-D (MIS 9), in all aminozones the marine transgression reached the present-day onshore area of the Netherlands. The transgression during NAZ-C (Oostermeer Interglacial: MIS 7) seems to be at least as widespread as its counterpart during NAZ-B (Eemian: MIS 5e) in the southern bight of the North Sea Basin. The stratigraphic position of the Oostermeer Interglacial is just below deposits of the Drente phase of the Saalian and because of this position the interglacial marine deposits have formerly erroneously considered to be of Holsteinian age. Neede, the 'classic' Dutch Holsteinian site, is dated in NAZ-E (MIS 11), like Noordbergum. Although the validity of these zones has been checked with independent data, some overlap between succeeding zones may occur. The relation between amino acid data from elsewhere in the North Sea Basin and the Netherlands amino zonation is discussed. The deposits at the Holsteinian stratotype Hummelsbüttel in North West Germany are dated in NAZ-D. This interglacial correlates with MIS 9. The Belvédère Interglacial, which is of importance for its archaeology, is in NAZ-D (MIS 9) and therefore of Holsteinian age as well. The lacustroglacial 'pottery clays' in the Noordbergum area are deposits from two glacial stages, which can be correlated with MIS 8 and 10 (the Elsterian). The pottery clay that is considered equivalent to the German 'Lauenburger Ton' correlates with MIS 10.

  10. Evaluation of the Gas Production Potential of Marine HydrateDeposits in the Ulleung Basin of the Korean East Sea

    SciTech Connect

    Moridis, George J.; Reagan, Matthew T.; Kim, Se-Joon; Seol,Yongkoo; Zhang, Keni

    2007-11-16

    Although significant hydrate deposits are known to exist in the Ulleung Basin of the Korean East Sea, their survey and evaluation as a possible energy resource has not yet been completed. However, it is possible to develop preliminary estimates of their production potential based on the limited data that are currently available. These include the elevation and thickness of the Hydrate-Bearing Layer (HBL), the water depth, and the water temperature at the sea floor. Based on this information, we developed estimates of the local geothermal gradient that bracket its true value. Reasonable estimates of the initial pressure distribution in the HBL can be obtained because it follows closely the hydrostatic. Other critical information needs include the hydrate saturation, and the intrinsic permeabilities of the system formations. These are treated as variables, and sensitivity analysis provides an estimate of their effect on production. Based on the geology of similar deposits, it is unlikely that Ulleung Basin accumulations belong to Class 1 (involving a HBL underlain by a mobile gas zone). If Class 4 (disperse, low saturation accumulations) deposits are involved, they are not likely to have production potential. The most likely scenarios include Class 2 (HBL underlain by a zone of mobile water) or Class 3 (involving only an HBL) accumulations. Assuming nearly impermeable confining boundaries, this numerical study indicates that large production rates (several MMSCFD) are attainable from both Class 2 and Class 3 deposits using conventional technology. The sensitivity analysis demonstrates the dependence of production on the well design, the production rate, the intrinsic permeability of the HBL, the initial pressure, temperature and hydrate saturation, as well as on the thickness of the water zone (Class 2). The study also demonstrates that the presence of confining boundaries is indispensable for the commercially viable production of gas from these deposits.

  11. Fog water collection under sea breeze conditions in the Western Mediterranean basin (Valencia region, Spain)

    NASA Astrophysics Data System (ADS)

    Azorin-Molina, C.; Corell, D.; Estrela, M. J.; Valiente, J. A.

    2010-07-01

    Orographic fog occurrences associated with sea breezes determine water collection potential over the mountain ranges near the Mediterranean coast of the Iberian Peninsula. Previous works have confirmed that the effect of sea breezes on cloud genera is to increase the frequency of low (Stratus) and convective (Cumulus) clouds. The primary impact of sea breeze flows corresponds to low stratiform clouds (Stratus, St, and Stratocumulus, Sc) formed in the convective internal boundary layer due to the inflow of moist sea air at lower levels. The formation of Sc clouds is caused by the rising and cooling of turbulent moist sea air over the highest slopes of the mountains at the end of the day. In the most Sc formation, we also observed dense fog banks of Stratus nebulosus (St neb) and dew during the early next morning, covering the inland topographical depressions. The aim of this study is to statistically analyze the impact of sea breezes on fog water collection in the convective internal boundary layer. The study area is located in the eastern of the Iberian Peninsula (Valencia region, Spain) and the survey corresponds to a 7-yr study period (2003-2009). This research is based upon a small network of eight passive fog water collectors distributed over 6 coastal- and 2 inland-mountain areas. A cylindrical fog water instrument (i.e. omnidirectional collection efficiency) based on the ASRC (Atmospheric Science Research Centre, State University of New York) string collector is used to sample fog water volumes on a daily basis. These stations also sampled temperature, humidity, wind speed and direction and precipitation measurements. The current study used these meteorological measurements to apply an automated and manual selection methodologies for identifying past sea breeze episodes. The dataset created by means of these selection techniques allows for the study of fog water volumes associated with sea breeze situations. A detailed statistical characterization of the

  12. Velocity-depth model estimation for a subsalt target from the Southern Gas Basin of the North Sea

    SciTech Connect

    Yilmaz, O.; Rutledge, J.; Sandvin, O.; Godfrey, B. )

    1996-01-01

    The Southern Gas Basin of the North Sea has been subjected to extensional tectonics, primarily in the east-west direction. Subsequent occurrence of the salt diapirism gave rise to the presence of complex structures. By doing a depth-domain analysis of a 3-D seismic survey data from an area in the Southern Gas Basin, we delineated the structural geometry of the top Rotliegendes formation beneath the complex Zechstein diapiric formation. This required an accurate estimate of the velocity-depth model above the Zechstein diapiric formation and removal of its deleterious effect on the underlying Permian sands of Rotliegendes and deeper targets. We conducted a layer-by-layer depth-domain analysis, and used coherency inversion to estimate layer velocities and 3-D poststack depth migration to delineate reflector geometries down to top Zechstein. We verified the accuracy of the velocity-depth model for the overburden above Zechstein by analyzing image gathers from prestack depth migration. We then analyzed constant-half-space image-gather stacks to estimate velocities for the substratum including Zechstein and the underlying Carboniferous sequence. Finally, we performed 3-D prestack depth migration to delineate the base Zechstein - top Rotliegendes geometry. This study demonstrates the need for depth-domain analysis of seismic data to derive accurate structure maps for targets beneath complex structures associated with salt and overthrust tectonics. The final output from depth-domain analysis -- a velocity-depth model, can then be used as a canvas for a reservoir model.

  13. Velocity-depth model estimation for a subsalt target from the Southern Gas Basin of the North Sea

    SciTech Connect

    Yilmaz, O.; Rutledge, J.; Sandvin, O.; Godfrey, B.

    1996-12-31

    The Southern Gas Basin of the North Sea has been subjected to extensional tectonics, primarily in the east-west direction. Subsequent occurrence of the salt diapirism gave rise to the presence of complex structures. By doing a depth-domain analysis of a 3-D seismic survey data from an area in the Southern Gas Basin, we delineated the structural geometry of the top Rotliegendes formation beneath the complex Zechstein diapiric formation. This required an accurate estimate of the velocity-depth model above the Zechstein diapiric formation and removal of its deleterious effect on the underlying Permian sands of Rotliegendes and deeper targets. We conducted a layer-by-layer depth-domain analysis, and used coherency inversion to estimate layer velocities and 3-D poststack depth migration to delineate reflector geometries down to top Zechstein. We verified the accuracy of the velocity-depth model for the overburden above Zechstein by analyzing image gathers from prestack depth migration. We then analyzed constant-half-space image-gather stacks to estimate velocities for the substratum including Zechstein and the underlying Carboniferous sequence. Finally, we performed 3-D prestack depth migration to delineate the base Zechstein - top Rotliegendes geometry. This study demonstrates the need for depth-domain analysis of seismic data to derive accurate structure maps for targets beneath complex structures associated with salt and overthrust tectonics. The final output from depth-domain analysis -- a velocity-depth model, can then be used as a canvas for a reservoir model.

  14. Sea Level and Ocean Bottom Pressure Variations From Altimetry, Mercator Model and GRACE Mission in the Argentine Basin

    NASA Astrophysics Data System (ADS)

    Garcia-Garcia, D.; Boy, J.; Chao, B. F.

    2008-12-01

    Sea Level Variations (SLV) in the Argentine basin, as already observed from space altimetry missions, show one of the most prominent variances in the oceans. Here we study two major signals in the Argentine basin, the annual and submonthly SLV signals, based on altimetry, various hydrographic data, and the time-variable gravity data from the GRACE mission. We demonstrate that the annual variation is mainly driven by density variations of the water column, that is the steric-SLV. In contrast, the submonthly SLV in the form of the so- called Argentine gyre, a barotropic counterclockwise gyre with a period around 25 days, is mainly mass- induced, that is, mostly produced by mass variations in the region [Fu et al. 2000]. The Argentine gyre signal is well reproduced by the MERCATOR ocean circulation (and bottom pressure) model, unlike the annual signal. We show that now the aliased form (into monthly sampling) is also captured in the GRACE time- variable gravity data after applying appropriated filters; further study awaits higher temporal-resolution GRACE data.

  15. Towards predicting basin-wide invertebrate organic biomass and production in marine sediments from a coastal sea.

    PubMed

    Burd, Brenda J; Macdonald, Tara A; van Roodselaar, Albert

    2012-01-01

    Detailed knowledge of environmental conditions is required to understand faunal production in coastal seas with topographic and hydrographic complexity. We test the hypothesis that organic biomass and production of subtidal sediment invertebrates throughout the Strait of Georgia, west coast of Canada, can be predicted by depth, substrate type and organic flux modified to reflect lability and age of material. A basin-wide database of biological, geochemical and flux data was analysed using an empirical production/biomass (P/B) model to test this hypothesis. This analysis is unique in the spatial extent and detail of P/B and concurrent environmental measurements over a temperate coastal region. Modified organic flux was the most important predictor of organic biomass and production. Depth and substrate type were secondary modifiers. Between 69-74% of variability in biomass and production could be explained by the combined environmental factors. Organisms <1 mm were important contributors to biomass and production primarily in shallow, sandy sediments, where high P/B values were found despite low organic flux. Low biomass, production, and P/B values were found in the deep, northern basin and mainland fjords, which had silty sediments, low organic flux, low biomass of organisms <1 mm, and dominance by large, slow-growing macrofauna. In the highest organic flux and biomass areas near the Fraser River discharge, production did not increase beyond moderate flux levels. Although highly productive, this area had low P/B. Clearly, food input is insufficient to explain the complex patterns in faunal production revealed here. Additional environmental factors (depth, substrate type and unmeasured factors) are important modifiers of these patterns. Potential reasons for the above patterns are explored, along with a discussion of unmeasured factors possibly responsible for unexplained (30%) variance in biomass and production. We now have the tools for basin-wide first

  16. Characterization of gas hydrate distribution using conventional 3D seismic data in the Pearl River Mouth Basin, South China Sea

    USGS Publications Warehouse

    Wang, Xiujuan; Qiang, Jin; Collett, Timothy S.; Shi, Hesheng; Yang, Shengxiong; Yan, Chengzhi; Li, Yuanping; Wang, Zhenzhen; Chen, Duanxin

    2016-01-01

    A new 3D seismic reflection data volume acquired in 2012 has allowed for the detailed mapping and characterization of gas hydrate distribution in the Pearl River Mouth Basin in the South China Sea. Previous studies of core and logging data showed that gas hydrate occurrence at high concentrations is controlled by the presence of relatively coarse-grained sediment and the upward migration of thermogenic gas from the deeper sediment section into the overlying gas hydrate stability zone (BGHSZ); however, the spatial distribution of the gas hydrate remains poorly defined. We used a constrained sparse spike inversion technique to generate acoustic-impedance images of the hydrate-bearing sedimentary section from the newly acquired 3D seismic data volume. High-amplitude reflections just above the bottom-simulating reflectors (BSRs) were interpreted to be associated with the accumulation of gas hydrate with elevated saturations. Enhanced seismic reflections below the BSRs were interpreted to indicate the presence of free gas. The base of the BGHSZ was established using the occurrence of BSRs. In areas absent of well-developed BSRs, the BGHSZ was calculated from a model using the inverted P-wave velocity and subsurface temperature data. Seismic attributes were also extracted along the BGHSZ that indicate variations reservoir properties and inferred hydrocarbon accumulations at each site. Gas hydrate saturations estimated from the inversion of acoustic impedance of conventional 3D seismic data, along with well-log-derived rock-physics models were also used to estimate gas hydrate saturations. Our analysis determined that the gas hydrate petroleum system varies significantly across the Pearl River Mouth Basin and that variability in sedimentary properties as a product of depositional processes and the upward migration of gas from deeper thermogenic sources control the distribution of gas hydrates in this basin.

  17. Pre-Variscan back-arc extension of Avalonia: The genesis of the Southern North Sea Basin

    NASA Astrophysics Data System (ADS)

    Smit, Jeroen; van Wees, Jan-Diederik; Cloetingh, Sierd

    2016-04-01

    The Devonian-Early Carboniferous was a period of intense rifting in the Avalonia microplate in between the Caledonian and the Hercynian-Alleghanian collision phases. This rifting phase created the typical horst-and-graben structure of much of East Avalonia's crust that is best known from the UK and Ireland where the horsts and the graben infill are located at or near the surface. In the Southern North Sea, the Netherlands and northwest Germany, the Late Devonian-Early Carboniferous rift structure and units are obliterated by the thick cover of Late Carboniferous-to-Recent basin fill and by the recurrent fault reactivation. Although this rifting created the basis for 350 Ma of lithospheric memory, its dynamics remains relatively unknown. Major open questions include the mode and total amount of extension as well as the age and origin of the Central Graben and the relation between structures located east and west of it. This study addresses these issues by integrating existing data from lithosphere to basin scales and a map-view restoration. We have revised the crustal map of the Thor Suture Zone. The newly defined northern margin of Avalonia and the Thor Suture Zone are key elements in the reconstruction of Devonian-Carboniferous rifting of Avalonian lithosphere. We present a revised map of Devonian-Carboniferous basin structures including the main horsts and grabens and the governing faults east of the Central Graben. Based on these maps, we present a new paleotectonic reconstruction and a novel geodynamic scenario for the Devonian- Carboniferous rifting. These findings are key for better understanding of long-lived tectonic compartmentalisation and post-rifting deformation phases.

  18. Towards Predicting Basin-Wide Invertebrate Organic Biomass and Production in Marine Sediments from a Coastal Sea

    PubMed Central

    Burd, Brenda J.; Macdonald, Tara A.; van Roodselaar, Albert

    2012-01-01

    Detailed knowledge of environmental conditions is required to understand faunal production in coastal seas with topographic and hydrographic complexity. We test the hypothesis that organic biomass and production of subtidal sediment invertebrates throughout the Strait of Georgia, west coast of Canada, can be predicted by depth, substrate type and organic flux modified to reflect lability and age of material. A basin-wide database of biological, geochemical and flux data was analysed using an empirical production/biomass (P/B) model to test this hypothesis. This analysis is unique in the spatial extent and detail of P/B and concurrent environmental measurements over a temperate coastal region. Modified organic flux was the most important predictor of organic biomass and production. Depth and substrate type were secondary modifiers. Between 69–74% of variability in biomass and production could be explained by the combined environmental factors. Organisms <1 mm were important contributors to biomass and production primarily in shallow, sandy sediments, where high P/B values were found despite low organic flux. Low biomass, production, and P/B values were found in the deep, northern basin and mainland fjords, which had silty sediments, low organic flux, low biomass of organisms <1 mm, and dominance by large, slow-growing macrofauna. In the highest organic flux and biomass areas near the Fraser River discharge, production did not increase beyond moderate flux levels. Although highly productive, this area had low P/B. Clearly, food input is insufficient to explain the complex patterns in faunal production revealed here. Additional environmental factors (depth, substrate type and unmeasured factors) are important modifiers of these patterns. Potential reasons for the above patterns are explored, along with a discussion of unmeasured factors possibly responsible for unexplained (30%) variance in biomass and production. We now have the tools for basin-wide first

  19. Sea level controls on the textural characteristics and depositional architecture of the Hueneme and associated submarine fan systems, Santa Monica Basin, California

    USGS Publications Warehouse

    Normark, W.R.; Piper, D.J.W.; Hiscott, R.N.

    1998-01-01

    Hueneme and Dume submarine fans in Santa Monica Basin consist of sandy channel and muddy levee facies on the upper fan. lenticular sand sheets on the middle fan. and thinly bedded turbidite and hemipelagic facies elsewhere. Fifteen widely correlatable key seismic reflections in high-resolution airgun and deep-towed boomer profiles subdivide the fan and basin deposits into time-slices that show different thickness and seismic-facies distributions, inferred to result from changes in Quaternary sea level and sediment supply. At times of low sea level, highly efficient turbidity currents generated by hyperpycnal flows or sediment failures at river deltas carry sand well out onto the middle-fan area. Thick, muddy flows formed rapidly prograding high levees mainly on the western (right-hand) side of three valleys that fed Hueneme fan at different times: the most recently active of the lowstand fan valleys. Hueneme fan valley, now heads in Hueneme Canyon. At times of high sea level, fans receive sand from submarine canyons that intercept littoral-drift cells and mixed sediment from earthquake-triggered slumps. Turbidity currents are confined to 'underfit' talweg channels in fan valleys and to steep, small, basin-margin fans like Dume fan. Mud is effectively separated from sand at high sea level and moves basinward across the shelf in plumes and in storm-generated lutite flows, contributing to a basin-floor blanket that is locally thicker than contemporary fan deposits and that onlaps older fans at the basin margin. The infilling of Santa Monica Basin has involved both fan and basin-floor aggradation accompanied by landward and basinward facies shifts. Progradation was restricted to the downslope growth of high muddy levees and the periodic basinward advance of the toe of the steeper and sandier Dume fan. Although the region is tectonically active, major sedimentation changes can be related to eustatic sea-level changes. The primary controls on facies shifts and fan growth

  20. Spatial and Temporal Strain Distribution Along the Central Red Sea Rift - A Study of the Hamd-Jizil Basin in Saudi Arabia

    NASA Astrophysics Data System (ADS)

    Szymanski, E.; Stockli, D.; Johnson, P.; Kattan, F. H.; Al Shamari, A.

    2006-12-01

    Numerous models exploring the rupturing modes and mechanisms of continental lithosphere are based on geological evidence from the Red Sea/Gulf of Suez rift system. Individually, the Red Sea basin is the prototype for many models of orthogonal continental rifting. Despite being a classic example of continental extension, many temporal and spatial strain distribution aspects, as well as the dynamic evolution of the rift architecture of the Red Sea, remain poorly constrained. Critical data come mostly from the Gulf of Suez and the Egyptian and Yemeni margins of the Red Sea; the rift flanks in Sudan and Saudi Arabia have remained largely unstudied, leaving a large information gap along the central portions of the rift system. Improving continental lithosphere rupture models requires an absolute understanding of the timing and magnitude of strain partitioning along the full rift flank. This study focuses on the development of extensional structures, syn- extensional sedimentary deposits, and rift-related Tertiary basaltic volcanism along the central flank of the rift system in Saudi Arabia. Geo- and thermochronometric techniques are used to elucidate the evolution of inboard and outboard strain markers manifested by structurally-controlled extensional basins that parallel the trend of the main Red Sea rift. Constraints on the dynamics of rift flank deformation are achieved through the collection of thermochronometric transects that traverse both the entire Arabian shield and individual normal faults that bound inland basins. Preliminary results show inland basins as asymmetric half-grabens filled by tilted Cenozoic sedimentary strata and separated by exhumed basement fault blocks. The most prominent extensional basin is the NW-trending Hamd-Jizil basin, located north of Madinah, measuring ~200 km along strike and up to 20 km in width. The Hamd-Jizil basin is structurally characterized by two half-grabens exposing a series of syn-rift siliciclastic sedimentary sections

  1. Petrology and isotopic composition of Quaternary basanites dredged from the Bering Sea continental margin near Navarin Basin

    USGS Publications Warehouse

    Davis, A.S.; Gunn, S.H.; Gray, L.-B.; Marlow, M. S.; Wong, F.L.

    1993-01-01

    Quaternary basanites were recovered from the continental margin of the Bering Sea near Navarin Basin. The basanites are highly vesicular flow rock and hyaloclastites similar to other alkalic volcanic rocks erupted repeatedly during the last Cenozoic on islands in the Bering Sea region and in mainland Alaska. K-Ar ages for the basanites indicate at least two episodes of volcanism at about 1.1 and 0.4 Ma. Trace-element data indicate these alkalic lavas have been generated by small, but variable, amounts of partial melting of a metasomatized lherzolite source. The relativley primitive compositions (MgO >9%), presence of mantle-derived xenoliths in some alkalic lavas, and presence of forsteritic olivine with low CaO and high NiO suggest that magma rose rapidly from great depth without spending time in large, long-lived magma chambers. Alkalic volcanism apparently resulted from upwelling and decompressional melting of small isolated mantle diapirs in response to local lithospheric attenuation associated with jostling of blocks during adjustment to regional stresses. -from Authors

  2. Evaluation of the toxicological properties of ground- and surface-water samples from the Aral Sea Basin.

    PubMed

    Bosch, K; Erdinger, L; Ingel, F; Khussainova, S; Utegenova, E; Bresgen, N; Eckl, P M

    2007-03-01

    In order to determine whether there is a potential health risk associated with the water supply in the Aral Sea Basin, ground- and surface-water samples were collected in and around Aralsk and from the Aral Sea in 2002. Water samples from Akchi, a small town close to Almaty, served as controls. Bioassays with different toxicological endpoints were employed to assess the general toxicological status. Additionally, the samples were analysed for microbial contamination. The samples were tested in the primary hepatocyte assay for their potential to induce micronuclei and chromosomal aberrations as cumulative indicators for genotoxicity. In parallel, the effects on cell proliferation evidenced by mitotic index and cytotoxicity such as the appearance of necrotic and apoptotic cells, were determined. Furthermore, samples were examined using the Microtox assay for general toxicity. Chemical analysis according to European regulations was performed and soil and water samples were analysed for DDT and DDE. The results obtained indicated no increased cyto- or genotoxic potential of the water samples, nor levels of DDT or DDE exceeding the thresholds levels suggested by WHO. Our data therefore do not support the hypothesis that the contamination of the drinking water in and around Aralsk is responsible for the health effects previously described such as increased rates of liver disease and in particular liver cancer. Microbiological analysis, however, revealed the presence of contamination in most samples analysed.

  3. Pb Concentration and Stable PB Isotopes in Dated-Core Sediments in the Ulleung Basin, East/japan Sea

    NASA Astrophysics Data System (ADS)

    Woo, J.; Choi, M.; Kim, D.

    2008-12-01

    This study investigated temporal and spatial variation of Pb and stable Pb isotopes accumulated in Ulleung Basin core sediments (12) using MC ICP/MS in order to identify the sources of anthropogenic Pb in the East/Japan Sea. Leached (1M HCl) Pb concentration and isotope ratios (207Pb/206Pb and 208Pb/206Pb) ware constant at around 20 mg/kg and 0.845 and 2.092 from 1700 to 1930 year, respectively and increased steadily up to 40 mg/kg and 0.873 to 2.129 at the beginning of 2000s, increased up to twice in concentration and as much as 3.31% and 1.64%. On the other hand, residual Pb concentrations were nearly constant for past 400 yrs. From the vertical profiles of Pb concentration and two end-members mixing model, anthropogenic Pb concentration and isotope ratios were estimated. The transport pathways of anthropogenic Pb could be estimated from 1) the comparison between the inventories of excess 210Pb in each sediment column and the input fluxes from the atmosphere and seawater column, 2) between the accumulation rate of anthropogenic Pb and mass accumulation rate of sediments. From the detailed evaluation for the pathways and isotope ratios of anthropogenic Pb, we proposed probable source of anthropogenic Pb. Pb emission by coal burning from the China and Korea initiated the accumulation of anthropogenic Pb in the sediments of East/Japan Sea from 1930s. The accumulation of Pb increased by the addition of anti-nocking agents from both countries untill beginning of 1990s, but from the middle of 1990s to the present, the phase-out of gasoline additives and the rapid increase of coal burning from China maintained the atmospheric Pb levels in the Ulleung basin nearly similar to before. However the local sources (e.g. ocean dumping) within this basin might take an important role in the rapid increase of anthropogenic Pb accumulation in slope areas from the middle of 1990s.

  4. Modeling the Effects of Transbasin Nonlinear Internal Waves Through the South China Sea Basin

    DTIC Science & Technology

    2013-06-01

    SCS basin in the presence of an internal ocean soliton was modeled and examined. The modeling entailed the integration of a raytracing program...presence of an internal ocean soliton was modeled and examined. The modeling entailed the integration of a raytracing program with an eigenray search...Joseph. Next, I would like to acknowledge Dr. Y. T. Lin, WHOI, for sharing his three-dimensional raytracing MATLAB program. Next, I would like to

  5. Analysis of South China Sea Shelf and Basin Acoustic Transmission Data

    DTIC Science & Technology

    2011-09-01

    this region ( Marburger , 2004, and Bernotavicius et al., 2010). The noise was then calculated as the sum of the distributed contributors (shipping... Marburger , J.M., “Estimation of geoacoustic properties in the South China Sea shelf using a towed source and vertical line hydrophone array,” Naval

  6. Large-scale single incised valley from a small catchment basin on the western Adriatic margin (central Mediterranean Sea)

    NASA Astrophysics Data System (ADS)

    Maselli, Vittorio; Trincardi, Fabio

    2013-01-01

    The Manfredonia Incised Valley (MIV) is a huge erosional feature buried below the Apulian shelf, on the western side of the Adriatic margin. The incision extends more than 60 km eastward, from the Tavoliere Plain to the outer shelf, not reaching the shelf edge. High-resolution chirp sonar profiles allow reconstruction of the morphology of the incision and its correlation at regional scale. The MIV records a single episode of incision, induced by the last glacial-interglacial sea level fall that forced the rivers draining the Tavoliere Plain to advance basinward, reaching their maximum extent at the peak of the Last Glacial Maximum. The valley was filled during a relatively short interval of about 10,000 yr during the Late Pleistocene-Holocene sea level rise and almost leveled-off at the time of maximum marine ingression, possibly recording the short-term climatic fluctuations that occurred. The accommodation space generated by the lowstand incision was exploited during the following interval of sea level rise by very high rates of sediment supply that allowed the preservation of up to 45 m of valley fill. High-resolution chirp sonar profiles highlight stratal geometries that are consistent with a typical transgressive valley fill of an estuary environment, including bay-head deltas, central basin and distal barrier-island deposits, organized in a backstepping configuration. The highest complexity of the valley fill is reached in the shallowest and most proximal area, where a kilometric prograding wedge formed during a period dominated by riverine input, possibly connected to high precipitation rates. Based on the depth of the valley margins during this interval, the fill was likely isochronous with the formation of sapropel S1 in the Mediterranean region and may have recorded significant fluctuations within the hydrological cycle.

  7. Distribution and inventories of polychlorinated biphenyls in the polar mixed layer of seven pan-arctic shelf seas and the interior basins.

    PubMed

    Carrizo, Daniel; Gustafsson, Örjan

    2011-02-15

    Assessment of the Arctic as a global repository of polychlorinated biphenyls (PCBs) and of uptake processes in the base of its marine food chain hinges on reliable information of PCB distribution in surface seawater, yet there is a scarcity of quality-assured PCB measurements in this key compartment. Here, surface seawater PCB concentrations and congener fingerprints are evaluated for all seven pan-Arctic shelf seas and for the interior basins. Particulate and dissolved PCBs were collected via trace-clean protocols on three basin-wide expeditions (AO-01, Beringia-2005, and ISSS-08). Concentrations of the sum of 13 abundant congeners (∑13PCB) were 0.13-21 pg/L, with higher concentrations in the shelf seas and lower concentrations in the Central Arctic Basin. Trichlorinated PCBs constituted about half of the total loadings in the Eastern Arctic (Beaufort, Chukchi, East Siberian, and Laptev Seas) and in the Central Basin, indicating an atmospheric source. In contrast, hexachlorinated PCBs were more abundant than tri-PCBs in the western sector, suggesting a role also for waterborne transport from regions of heavy PCB consumption in North America and Europe. Finally, the inventory of ∑13PCB in the polar mixed layer of the entire Arctic Ocean was 0.39 ton, which implies that only 0.0008% of historical PCB emissions are now residing in Arctic surface waters.

  8. Arctic Ocean stability: The effects of local cooling, oceanic heat transport, freshwater input, and sea ice melt with special emphasis on the Nansen Basin

    NASA Astrophysics Data System (ADS)

    Rudels, Bert

    2016-07-01

    The Arctic loses energy to space and heat is transported northward in the atmosphere and ocean. The largest transport occurs in the atmosphere. The oceanic heat flux is significantly smaller, and the warm water that enters the Arctic Ocean becomes covered by a low-salinity surface layer, which reduces the heat transfer to the sea surface. This upper layer has two distinct regimes. In most of the deep basins it is due to the input of low-salinity shelf water, ultimately conditioned by net precipitation and river runoff. The Nansen Basin is different. Here warm Atlantic water is initially in direct contact with and melts sea ice, its upper part being transformed into less dense surface water. The characteristics and depth of this layer are determined as functions of the temperature of the Atlantic water and for different energy losses using a one-dimensional energy balance model. The amount of transformed Atlantic water is estimated for two different sea ice melt rates and the assumption of a buoyant boundary outflow. To create the upper layer sea ice formed elsewhere has to drift to the Nansen Basin. With reduced ice cover, this ice drift might weaken and the ice could disappear by the end of winter. The surface buoyancy input would disappear, and the upper layer might eventually convect back into the Atlantic water, reducing the formation of less dense Polar water. The created ice-free areas would release more heat to the atmosphere and affect the atmospheric circulation.

  9. Eocene and Oligocene basins and ridges of the Coral Sea-New Caledonia region: Tectonic link between Melanesia, Fiji, and Zealandia

    NASA Astrophysics Data System (ADS)

    Mortimer, Nick; Gans, Phillip B.; Palin, J. Michael; Herzer, Richard H.; Pelletier, Bernard; Monzier, Michel

    2014-07-01

    This paper presents 34 geochemical analyses, 24 Ar-Ar ages, and two U-Pb ages of igneous rocks from the back-arc basins and submarine ridges in the Coral Sea-New Caledonia region. The D'Entrecasteaux Ridge is a composite structural feature. Primitive arc tholeiites of Eocene age (34-56 Ma) are present along a 200 km length of the ridge and arguably were part of the initial line of subduction inception between Fiji and the Marianas; substantial Eocene arc edifices are only evident at the eastern end where Bougainville Guyot andesite breccias are dated at 40 ± 2 Ma. The South Rennell Trough is confidently identified as a 28-29 Ma (early Oligocene) fossil spreading ridge, and hence, the flanking Santa Cruz and D'Entrecasteaux basins belong in the group of SW Pacific Eocene-Early Miocene back-arc basins that include the Solomon Sea, North Loyalty, and South Fiji basins. The rate and duration of spreading in the North Loyalty Basin is revised to 43 mm/yr between 28 and 44 Ma, longer and faster than previously recognized. The direction of its opening was to the southeast, that is, parallel to the continent-ocean boundary and perpendicular to the direction of coeval New Caledonia ophiolite emplacement. Medium- and high-K alkaline lavas of 23-25 Ma (late Oligocene) age on the northern Norfolk Ridge are an additional magmatic response to Pacific trench rollback.

  10. Seismic imaging of deep low-velocity zone beneath the Dead Sea basin and transform fault: Implications for strain localization and crustal rigidity

    USGS Publications Warehouse

    ten Brink, U.S.; Al-Zoubi, A. S.; Flores, C.H.; Rotstein, Y.; Qabbani, I.; Harder, S.H.; Keller, Gordon R.

    2006-01-01

    New seismic observations from the Dead Sea basin (DSB), a large pull-apart basin along the Dead Sea transform (DST) plate boundary, show a low velocity zone extending to a depth of 18 km under the basin. The lower crust and Moho are not perturbed. These observations are incompatible with the current view of mid-crustal strength at low temperatures and with support of the basin's negative load by a rigid elastic plate. Strain softening in the middle crust is invoked to explain the isostatic compensation and the rapid subsidence of the basin during the Pleistocene. Whether the deformation is influenced by the presence of fluids and by a long history of seismic activity on the DST, and what the exact softening mechanism is, remain open questions. The uplift surrounding the DST also appears to be an upper crustal phenomenon but its relationship to a mid-crustal strength minimum is less clear. The shear deformation associated with the transform plate boundary motion appears, on the other hand, to cut throughout the entire crust. Copyright 2006 by the American Geophysical Union.

  11. The sea-air exchange of mercury (Hg) in the marine boundary layer of the Augusta basin (southern Italy): concentrations and evasion flux.

    PubMed

    Bagnato, E; Sproveri, M; Barra, M; Bitetto, M; Bonsignore, M; Calabrese, S; Di Stefano, V; Oliveri, E; Parello, F; Mazzola, S

    2013-11-01

    The first attempt to systematically investigate the atmospheric mercury (Hg) in the MBL of the Augusta basin (SE Sicily, Italy) has been undertaken. In the past the basin was the receptor for Hg from an intense industrial activity which contaminated the bottom sediments of the Bay, making this area a potential source of pollution for the surrounding Mediterranean. Three oceanographic cruises have been thus performed in the basin during the winter and summer 2011/2012, where we estimated averaged Hgatm concentrations of about 1.5±0.4 (range 0.9-3.1) and 2.1±0.98 (range 1.1-3.1) ng m(-3) for the two seasons, respectively. These data are somewhat higher than the background Hg atm value measured over the land (range 1.1±0.3 ng m(-3)) at downtown Augusta, while are similar to those detected in other polluted regions elsewhere. Hg evasion fluxes estimated at the sea/air interface over the Bay range from 3.6±0.3 (unpolluted site) to 72±0.1 (polluted site of the basin) ng m(-2) h(-1). By extending these measurements to the entire area of the Augusta basin (~23.5 km(2)), we calculated a total sea-air Hg evasion flux of about 9.7±0.1 g d(-1) (~0.004 tyr(-1)), accounting for ~0.0002% of the global Hg oceanic evasion (2000 tyr(-1)). The new proposed data set offers a unique and original study on the potential outflow of Hg from the sea-air interface at the basin, and it represents an important step for a better comprehension of the processes occurring in the marine biogeochemical cycle of this element.

  12. Lithology and late postglacial stratigraphy of bottom sediments in isolated basins of the White Sea coast exemplified by a small lake in the Chupa settlement area (Northern Karelia)

    NASA Astrophysics Data System (ADS)

    Korsakova, O. P.; Kolka, V. V.; Tolstobrova, A. N.; Lavrova, N. B.; Tolstobrov, D. S.; Shelekhova, T. S.

    2016-05-01

    The complex lithological, geochemical, geochronological, and micropaleontological (diatoms, spores, pollen) investigations of stratified bottom sediments that constitute facies-variable sedimentary sequences in a small isolated lake located near the upper limit of the sea on the White Sea coast made it possible to define lithostratigraphic units (LSU) forming the complete sedimentary succession in deep parts of isolated basins. It is shown that stratigraphy of heterogeneous sequences is determined by two regional transgressive-regressive cycles in relative sea level fluctuations: alternating late Glacial and Holocene transgressions and regressions. The lower part of a clastogenic clayey-sandy-silty sequence successively composed of freshwater (LSU 1) and brackish-water (LSU 2) sediments of the ice-marginal basins and marine postglacial facies (LSU 3) was formed during the late Glacial glacioeustatic marine transgression. Its upper part formed in different isolated basins at different stages of the Holocene is represented depending on its altimetric position on the coastal slope by costal marine sediments (LSU 4) and facies of the partly isolated inlet (LSU 5). The organogenic sapropelic sequence, which overlies sediments of the marine basin and partly isolated bay, corresponds to lithostratigraphic units represented by Holocene sediments accumulated in the meromictic lake (LSU 6), onshore freshwater basin (LSU 7), and freshwater basin with elevated water mineralization (LSU 8) deposited during maximum development of Holocene transgression and lacustrine sediments (LSU 9) formed in coastal environments during terminal phases of the Holocene. The defined lithostratigraphic units differ from each other in lithological, micropaleontological, and geochemical features reflected in structural and textural properties of their sediments, their composition, inclusions, and composition of paleophytocoenoses and diatom assemblages.

  13. Transfer of deformation in back-arc basins with a laterally variable rheology: Constraints from analogue modelling of the Balkanides-Western Black Sea inversion

    NASA Astrophysics Data System (ADS)

    Munteanu, Ioan; Willingshofer, Ernst; Sokoutis, Dimitrios; Matenco, Liviu; Dinu, Corneliu; Cloetingh, Sierd

    2013-08-01

    The balance between extension and contraction in back-arc basins is very sensitive to a number of parameters related to on-going subduction and collision processes. This leads to complex back-arc geometries, where a lateral transition between crustal blocks with contrasting rheologies is often recorded. One good example is the back-arc region of the Balkanides-Pontides orogens, where lateral variations in rheologies are observed between the Balkanides-Moesian block and the Pontides-Western Black Sea Basin. The latter opened during Cretaceous-Eocene, and has been inverted together with the former starting during late Middle Eocene. The inversion generated contrasting geometries along the orogenic strike, with a narrow zone of high deformation in the Balkanides-Moesia region, wide areas of thrusting with low offsets in the Pontides-Western Black Sea Basin and a transitional zone characterized by highly curved geometries. This overall type of inversion is investigated here by the means of analogue modelling testing the role of inherited crustal geometries during inversion. Our modelling suggests that the contrasting architecture of inverted structures observed in the Balkanides-Pontides domain are the result of pre-existing crustal stretching geometries of various blocks inherited from the Cretaceous-Eocene extension. The stretched and weak back-arc basins can transfer contraction deformation at large distances, explaining structures derived by observational studies. The collisional deformation recorded in the Pontides was transmitted at large distances that are in the range of the contraction structures observed in the centre and northern part of the Western Black Sea. In the light of analogue modelling results we argue that the Western Black Sea was a rheologically weaker domain when compared with the adjacent western onshore at the beginning of the inversion, in contrast with previous results derived from numerical modelling studies that argued for a strong West

  14. Monterey Fan: Growth pattern control by basin morphology and changing sea levels

    USGS Publications Warehouse

    Normark, W.R.; Gutmacher, C.E.; Chase, T.E.; Wilde, P.

    1984-01-01

    Monterey Fan is the largest modern fan off the California shore. Two main submarine canyon systems feed it via a complex pattern of fan valleys and channels. The northern Ascension Canyon system is relatively inactive during high sea-level periods. In contrast, Monterey Canyon and its tributaries to the south cut across the shelf and remain active during high sea level. Deposition on the upper fan is controlled primarily by the relative activity within these two canyon systems. Deposition over the rest of the fan is controlled by the oceanic crust topography, resulting in an irregular fan shape and periodic major shifts in the locus of deposition. ?? 1984 Springer-Verlag New York Inc.

  15. Analysis of atmosphere-sea ice interactions in the Arctic basin using ESMR microwave data

    NASA Technical Reports Server (NTRS)

    Crane, R. G.; Barry, R. G.; Zwally, H. J.

    1982-01-01

    Data from the Electrically Scanning Microwave Radiometer (ESMR) on Nimbus-5 are used to determine the spatial and temporal patterns of change in microwave brightness signatures of Arctic sea ice during a full annual cycle (1973/74). Interactions of ice conditions with the atmosphere are examined using grid point data for surface air temperature and atmospheric pressure. Principal components analysis is used to examine the major elements present in the microwave and atmospheric data. Component scores from these analyses are then used in a canonical correlation analysis to determine interassociations present between the ice and atmosphere in the Beaufort Sea and the European sectors on a synoptic time scale. The synoptic weather conditions associated with the pattern of snow melt on the ice in spring 1974 are described, and a clarification of possible alternative interpretations of features identified as polynyi occurring at 80-85 deg N during the late summer 1974 is presented.

  16. Observed and simulated trophic index (TRIX) values for the Adriatic Sea basin

    NASA Astrophysics Data System (ADS)

    Fiori, Emanuela; Zavatarelli, Marco; Pinardi, Nadia; Mazziotti, Cristina; Ferrari, Carla Rita

    2016-09-01

    The main scope of the Marine Strategy Framework Directive is to achieve good environmental status (GES) of the EU's marine waters by 2020, in order to protect the marine environment more effectively. The trophic index (TRIX) was developed by Vollenweider in 1998 for the coastal area of Emilia-Romagna (northern Adriatic Sea) and was used by the Italian legislation to characterize the trophic state of coastal waters. We compared the TRIX index calculated from in situ data ("in situ TRIX") with the corresponding index simulated with a coupled physics and biogeochemical numerical model ("model TRIX") implemented in the overall Adriatic Sea. The comparison between in situ and simulated data was carried out for a data time series on the Emilia-Romagna coastal strip. This study shows the compatibility of the model with the in situ TRIX and the importance of the length of the time series in order to get robust index estimates. The model TRIX is finally calculated for the whole Adriatic Sea, showing trophic index differences across the Adriatic coastal areas.

  17. Tephrochronology of a 70 ka-long marine record in the Marsili Basin (southern Tyrrhenian Sea)

    NASA Astrophysics Data System (ADS)

    Tamburrino, S.; Insinga, D. D.; Pelosi, N.; Kissel, C.; Laj, C.; Capotondi, L.; Sprovieri, M.

    2016-11-01

    A sequence of tephra layers is studied in a 13.9 m-long deep-sea core (MD01-2474G) from the southern Tyrrhenian Sea. The chronology of the succession is provided by a high-resolution age-depth model based on isotope stratigraphy and AMS radiocarbon dating, which place the succession of events in a time interval spanning the last 70 ka. Based on a precise chronological framework and proximal-distal correlations, the Y-1, Y-6 and Y-7 main marker tephras were identified. Compositional data on fresh micro-pumice or glass shards of selected tephras were correlated with the coeval volcanic activity of Aeolian Arc (Vulcano and Salina), Mt. Etna, Phlegrean Fields Pantelleria and Ischia. The tephra sequence contains a number of deposits documenting recurrent activity on Vulcano Island at ca. 6.9 ka BP (MD3), ca. 16.7 ka BP (MD11), ca. 23.2 ka BP (MD14), ca. 29.6 ka BP (MD15), ca. 36.9 ka BP (MD22) and ca. 42.5 ka BP (MD27). The results presented in this study improve the southern Tyrrhenian Sea tephrostratigraphic framework and provide new insights into chemistry and dispersal area of Aeolian Arc pyroclastic deposits in this sector of the Central Mediterranean.

  18. Spectral and Geomorphic Evidence for a Past Inland Sea in Eridania Basin, Mars

    NASA Astrophysics Data System (ADS)

    Noe Dobrea, E. Z.; Moore, J.; Howard, A.; Catling, D.; Grant, J.

    2008-12-01

    Eridania basin is the name given to a depression in the southern highlands composed of many overlapping and highly degraded craters. It is located at the head of Ma"adim Vallis, and has been suggested by [1] to have contained its source waters. Geomorphic evidence presented in [1] for the presence of a paleosea includes 1) the origin of Ma"adim as a fully developed channel at the divide between it and Eridania basin; 2) the floor materials of the six largest craters that form Eridania Basin have an unusually high internal relief (~1 km) and slope (~0.5-1.5°) among degraded Martian craters, which are usually flat-floored; 3) fluvial valleys do not dissect the slopes of these deeper crater floor depressions, unlike similar slopes that are dissected at higher levels in the watershed. Additionally, we identify inward-facing escarpments that extend over large distances at near- constant topographic contours. CRISM Full Resolution Targeted (FRT) observations of outcrop units throughout the region show a preponderance of hydrous mineralogies, including Fe/Mg smectites (identified by 1.4, 1.9, and ~2.3 μm bands), hydrated silica (identified by 1.4, 1.9, and broad 2.2 μm bands), and kaolinite-group (identified primarily by at 1.4 μm band and a doublet at 2.2 μm) minerals. Focused spectral studies of the chaos units found in the three deepest portions of Eridania Basin (Ariadness Colles, Gorgonum Chaos, and Atlantis Chaos) show abundant hydrous minerals associated with the chaos hummocks, suggesting that these hummocks are the erosional remnants of a unit containing aqueously deposited minerals. The distribution of these minerals is found to vary spatially from hummock to hummock and they typically lack obvious bedding at HiRISE scales (50 cm/pixel). Analyses of other geomorphologically distinct indurated units in the region show that Fe/Mg-smectites are present in a large fraction of these units, suggesting a complex history of deposition, alteration, and erosion

  19. Timing, Structural Styles, and Tectonic Significance of Neogene Basin Inversion Across the South China Sea and Indonesian Back-Arc Region

    NASA Astrophysics Data System (ADS)

    Dorobek, S. L.; Olson, C. C.

    2005-12-01

    Basin inversion is a common phenomenon in many intracontinental extensional or transtensional settings that are subjected to later contractional deformation. Numerous examples of inverted Paleogene rift basins are found in the Indonesian back-arc region and southern and western parts of the South China Sea. Inversion was widespread across the broad region, mainly began in latest Oligocene-early Miocene time, and locally continues to the present day. Most basins were fully inverted in less than 15 Myr and inversion typically involved reactivation of preexisting extensional fault systems that formed during Paleogene rifting. We examined the tectonic styles and regional timing of basin inversion across this region in order to understand the tectonic and geodynamic reasons for the inversion. The timing of regional inversion and structural styles associated with inversion reflect roughly N-S to NNW-SSE oriented intraplate compressive stress, which suggests that incipient collision of Australian continental crust along the eastern Indonesian archipelago and `South Chinese/Vietnamese' crust along the Borneo/South Palawan margin were responsible for the widespread inversion. A fundamental change from uncoupled to coupled subduction along the Indonesian trench and Borneo/South Palawan margin, coincident with the incipient subduction of continental crust along these convergent margins during latest Oligocene-early Miocene time, may explain why intraplate compressive stress was transmitted across the Indonesian back-arc and southern South China Sea (Sunda Shelf) region. Prior to late Oligocene time, subduction was essentially uncoupled and Paleogene rift basins across the Indonesian backarc and Sunda Shelf region were thermally subsiding. The rheology of Sundaland and offshore Southeast Asian continental lithosphere also was especially conducive to widespread, nearly synchronous basin inversion during Neogene time, which likely reflects the low viscosity nature of the mantle

  20. Geochemical assessment of hydrocarbon migration phenomena: Case studies from the south-western margin of the Dead Sea Basin

    NASA Astrophysics Data System (ADS)

    Sokol, Ella; Kozmenko, Olga; Smirnov, Sergey; Sokol, Ivan; Novikova, Sofya; Tomilenko, Anatoliy; Kokh, Svetlana; Ryazanova, Tatyana; Reutsky, Vadim; Bul'bak, Taras; Vapnik, Yevgeny; Deyak, Michail

    2014-10-01

    with the existing views of maturation, migration, and accumulation of hydrocarbons, as well as basin fluid transport processes in the Dead Sea area.

  1. Late quaternary deltaic and carbonate sedimentation in the Gulf of Papua foreland basin: Response to sea-level change

    USGS Publications Warehouse

    Harris, P.T.; Pattiaratchi, C.B.; Keene, J.B.; Dalrymple, R.W.; Gardner, J.V.; Baker, E.K.; Cole, A.R.; Mitchell, D.; Gibbs, P.; Schroeder, W.W.

    1996-01-01

    The rivers that drain the wet, mountainous island of New-Guinea discharge about 1.5 billion tonnes/yr of sediments into the adjacent seas, including the foreland basin between New Guinea and Australia. Despite this huge sediment input, there appears to have been only limited deposition in the Gulf of Papua during the (Holocene) postglacial rise in sea level. Seismic and core data indicate that the transgressive systems tract in the Gulf of Papua is thin and patchy. It is confined to regions within and north of an incised, east-west-trending shelf-valley system. Of the possible explanations for the absence of a significant transgressive systems tract, inland storage and along- and off-shelf transport of the sediment are of greatest significance. Reef growth up to the latitude of the east-west-trending incised-valley system in the southern Gulf of Papua is considered to have been facilitated by a northward-flowing coastal boundary current, the Coral Sea Coastal Current. This current now sweeps turbid, brackish waters and terrigenous sediments discharged by the rivers northwards away from the reefs. An observed northward offset in transgressive sediments in relation to the axis of the shelf valleys suggests that such a northward-flowing shelf current operated during the late Pleistocene and early Holocene. The northern limit of the Great Barrier Reef could thus be controlled by the balance between fluvial sediment supply and northward advection of suspended sediment by the Coral Sea Coastal Current. This current may also be important in maintaining a supply of clear water to the eastern Gulf of Papua, thus enabling photosynthesis and the flourishing of calcareous-algae (Halimeda) bioherms or biostromes at depths of up to 100 m over much of the middle and outer shelf, directly offshore of the modern Fly Delta. These carbonate sediments represent the exposed maximum flooding surface and condensed section. Modern highstand delta deposits have begun to prograde over this

  2. Formation mechanism of the Qiongdongnan basin northwest of the South China Sea-dating the sinistral slip of the Red River Fault Zone

    NASA Astrophysics Data System (ADS)

    Sun, Z.; Jiang, J.; Xie, W.

    2010-12-01

    Locating on the northwestern margin of the South China Sea, the Qiongdongnan basin is a NE-trending rift zone in general. Bounding with the NW-trending Yinggehai basin and the Red River- East Vietnam Fault Zone to the west, the evolution of the Qiongdongnan basin bears large amounts of information about the slip of the Red River Fault zone. Combined the geological analysis with analogue modeling experiments, we suggest that the evolution of the Qiongdongnan is controlled not only by the southeastward to south southeastward extension, but also by the sinistral slip of the Red River Fault zone. The central depression of the Qiongdongnan basin is controlled mainly by the southeastward to south southeastward extension, while the southern depression developed under the combined stress filed of southeastward extension and the dextral slip along the NNW-trending Red River fault zone. The northern depression was formed by the combined effect of the sinistral slip along the Red River Fault Zone and the southeastward extension. According to the age of the shear fault starting to develop in the southwest of the Qiongdongnan basin, as well as the age for the northwestern part to develop, the sinistral slip of the Red River Fault zone began around early oligocene, later than the rifting of the Qiongdongnan basin. The sinistral slip rate of the Red River Fault zone during early Oligocene may be smaller than the displacement rate of the Qiongdongnan basin, but become reversed thereafter, which in turn caused tectonic inversion and folding along the western segment of the Qiongdongnan basin, and NW- to NNW-trending Rediel faults from late Oligocene to middle Miocene. Through the deformation history of the Qiongdongnan basin, we defined the sinistral slip stage Indochina along the Red River Fault zone from about 36Ma to 16Ma, and further a rapid slip occurring after 30Ma.

  3. Base of brackish-water mud as key regional stratigraphic marker of mid-Holocene marine flooding of the Baltic Sea Basin

    NASA Astrophysics Data System (ADS)

    Virtasalo, Joonas J.; Endler, Michael; Moros, Matthias; Jokinen, Sami A.; Hämäläinen, Jyrki; Kotilainen, Aarno T.

    2016-12-01

    Many modern epicontinental seas were dry land before their marine flooding by the mid-Holocene glacioeustatic sea-level rise, whereas the Baltic Sea Basin was covered by a huge postglacial lake. This change from a postglacial lake to the present-day semi-enclosed brackish-water sea is studied here in sediment cores and acoustic profiles from the Baltic Sea major sub-basins, based on novel datasets combined with information extracted from earlier publications. In shallow areas (<50m water depth), the base of the brackish-water mud is erosional and covered by a patchy, thin, transgressive silt-sand sheet resulting from decreased sediment supply, winnowing and the redistribution of material from local coarse-grained deposits during transgression. This erosional marine flooding surface becomes sharp and possibly erosional in deep areas (>50m water depth), where it may be locally less clearly expressed due to reworking and bioturbation. Both in the shallow and deep areas, the brackish-water mud is strongly enriched in organic matter compared to underlying sediments. Bioturbation type changes at the flooding surface in response to the increased sedimentary organic content, but no firm-ground ichnofacies were developed because of low erosion. It is concluded that the base of the brackish-water mud is a robust allostratigraphic bounding surface that is identifiable by the lithologic examination of cores over the Baltic Sea. The surface is a distinct reflector in seismic-acoustic profiles, which facilitates mapping and basin-wide stratigraphic subdivision. Detailed geochronologic studies are required to confirm if sediments immediately overlying the erosional flooding surface in shallow areas are younger than the basal part of the brackish-water mud in deep areas that is predicted to be time-equivalent to the erosion.

  4. Geophysical Investigations of Crustal Structure of Cenozoic Rifting Basin in Passive Continental Margin: The Pearl River Mouth Basin, South China Sea

    NASA Astrophysics Data System (ADS)

    Qiu, N.

    2015-12-01

    The Pearl River Mouth Basin (PRMB) initiated in the Cenozoic with rifting, and became a part of the South China Sea (SCS) rifted passive continental margin. Decades of industrial exploration in this proliferous region have produced lots of geological and geophysical data. In order to get the first order crustal scale structure, we integrate well data, multi channel seismic reflection, and the observed gravity field for a joint inversion. The Cenozoic sediment of PRMB comprises of several stratigraphic sequences, including the terrestrial facies, the marine facies and the transitional facies. The sedimentary model takes into account of two main parts that refer to the Paleogene to Neogene unit and the Neogene to Quaternary unit, which were respectively formed during the intercontinental rifting stage and the passive continental margin post-rifting stage. By integrating long cable seismic profiles, interval velocity and performing gravity modelling, we have modelled the sub-sedimentary basement. There are some high-density bodies in the lower part of crust (ρ> 2.8 g/cm3), most of which were probably made up by emplacement from the upper mantle into the lower crust. The crystalline continental crust spans from unstretched domains (as thick as about 25 km) near the continental shelf to extremely thinned domains (of less than 6 km thickness) in the sag center. The presented crust-scale structural model shows that the crystalline crust of the Liwan Sag (LWS) and Baiyun sag (BYS) are thinner than other parts of PRMB, especially, the crystalline crust thickness in BYS is even less than 6 km. we could preliminary infer that the crystalline crust may be more easily stretched and be thinned by the existence of hot and soft substances at the lower crust.

  5. Spring bloom dinoflagellate cyst dynamics in three eastern sub-basins of the Baltic Sea

    NASA Astrophysics Data System (ADS)

    Sildever, Sirje; Kremp, Anke; Enke, Annely; Buschmann, Fred; Maljutenko, Ilja; Lips, Inga

    2017-04-01

    Dinoflagellate cyst abundance and species composition were investigated before, during and after the spring bloom in the Gulf of Finland, north-eastern Baltic Proper and Gulf of Riga in order to detect spatial and temporal dynamics. Transport of newly formed cysts by currents was modelled to explore the possible distance travelled by cysts before sedimentation. The cyst community of the spring bloom dinoflagellates was dominated by the cysts of Biecheleria baltica in all basins, despite its marginal value in the planktonic spring bloom community in the Gulf of Riga. Dinoflagellate cyst abundance in the surface sediments displayed temporal dynamics in all basins, however, this appeared to be also influenced by physical processes. The model simulation showed that newly formed cysts are transported around 10-30 km from the point of origin before deposited. The latter suggests that transport of resting stages in the water column significantly affects spatial cyst distribution in the sediments and thus needs to be considered in the interpretation of temporal biological productivity patterns of a water body from cyst proxies.

  6. Examination of Global Seismic Tomography Images and Sea-Surface Magnetic Field Anomaly Profiles in the West Philippine Basin for the Large Clockwise Rotation of the Philippine Sea Plate during the Last 55 Million Years

    NASA Astrophysics Data System (ADS)

    Choe, H.; Lee, S. M.

    2014-12-01

    The Philippine Sea Plate is thought to have undergone a 90° clockwise rotation during the last 55 million years. However, evidences for such an argument are rather circumstantial. For instance, paleomagnetic measurements for the large rotation are derived largely from Halmahera, Indonesia which is quite close to the plate boundary. It is thus possible that this region may have undergone local deformation separate from the main parts of the Philippine Sea Plate. In this study, we examine the global seismic tomography images of the mantle beneath the Philippine Sea Plate and the marine magnetic field anomaly data at the sea surface from the West Philippine Basin to see whether they agree with the presumed motion of the Philippine Sea Plate. Our comparison between the plate reconstruction and global tomography suggests that the rotation of Philippine Sea Plate may not have been continuous but instead experienced a temporal break at around 32 Ma. The exact nature of this pause is uncertain, but it may be related to a sudden change in the configuration of subduction systems. A detail comparison with recent results from IODP Legs 350 and 351 is therefore necessary, including a search for a change in the depositional style of basin sediment. We also examined the detailed the shape of magnetic anomalies (such as skewness) and compare them with the previous model by allowing the magnetization to have direction corresponding to that during the opening of the West Philippine Basin. At this moment, it is too early to tell if the sudden change at around 32 Ma or other inferred breaks can be seen in the magnetic profiles as well.

  7. Late Pleistocene and Holocene palaeoenvironments in and around the middle Caspian basin as reconstructed from a deep-sea core

    NASA Astrophysics Data System (ADS)

    Leroy, Suzanne A. G.; López-Merino, Lourdes; Tudryn, Alina; Chalié, Françoise; Gasse, Françoise

    2014-10-01

    Late Pleistocene and/or Holocene high-resolution palynological studies are available for the south basin of the Caspian Sea (CS), the world's largest lake. However, the north and middle basins have not been the object of high-resolution palynological reconstructions. This new study presents the pollen, spores and dinoflagellate cysts records obtained from a 10 m-long sediment core recovered in the middle basin, which currently has brackish waters and is surrounded by arid and semi-arid vegetation. An age-depth model built based on six radiocarbon dates on ostracod shells indicates that the sequence spans the period from 14.47 to 2.43 cal. ka BP. The present palaeoenvironmental study focuses on the top 666 cm, or from 12.44 to 2.43 cal. ka BP. At the vegetation level, the Younger Dryas is characterised by an open landscape dominated by desert vegetation composed by Amaranthaceae with shrubs and salt-tolerant plants. However, although the Early Holocene is also characterised by desert vegetation, it is enriched in various shrubs such as Ephedra and Calligonum, but tree expansion is not important at the Holocene onset. After a major shift at 8.19 cal. ka BP, the Middle Holocene displays now both the character of desert and of steppe, although some trees such as Quercus and Corylus slightly spread. The Late Holocene records steppe vegetation as dominant, with more tree diversity. Regarding the lacustrine signal, the dinocyst assemblage record fluctuates between slightly brackish conditions highlighted by Pyxidinopsis psilata and Spiniferites cruciformis, and more brackish ones - similar to the present day - with the dominance of Impagidinium caspienense. The Late Pleistocene is characterised by low salinities, related to the Khvalynian highstand. From 11.56 cal. ka BP, slightly more saline waters are reconstructed with an increase of I. caspienense for a period of 1000 years, which could be attributed to the Mangyshlak lowstand. From 10.55 cal. ka BP, low salinity

  8. Geophysical evidence and inferred triggering factors of submarine landslides on the western continental margin of the Ulleung Basin, East Sea

    NASA Astrophysics Data System (ADS)

    Cukur, Deniz; Kim, Seong-Pil; Kong, Gee-Soo; Bahk, Jang-Jun; Horozal, Senay; Um, In-Kwon; Lee, Gwang-Soo; Chang, Tae-Soo; Ha, Hun-Jun; Völker, David; Kim, Jung-Ki

    2016-12-01

    Submarine landslides form very complex depositional and erosional features on the seafloor, and their dynamics and triggering processes are yet to be understood completely. Numerous studies are being undertaken both because of the scientific significance but also for their potential harm to seafloor infrastructure and coastal areas. This study investigates the styles and causes of landsliding along the western margin of the Ulleung Basin in the East Sea, based on multiple sparker, subbottom profiler, multibeam echosounder and sediment core datasets collected in 2015. The bathymetric analyses indicate that the southern slope of the Ulleung Basin has experienced at least seven submarine failures. These failures left clear arcuate-shaped scarps that initiated at water depths of 600 m. The observed headwall scarps have heights that exceed 60 m and appear to be the result of retrogressive-type failures. Seismic reflection data clearly image the basal sliding surface that is characterized by a prominent high-amplitude reflector. Chaotic-to-transparent seismic facies occur immediately downslope of the headwall scarps; these represent 20 m thick landslide deposits. Gravity cores taken from areas adjacent to the scars suggest that these slides are older than ca. 97 ka. Interpretation of the present data shows that faults appear to cut recent sediments upslope of scarps, and that the slope may still be in an active phase of failure. Seismic data also image various overpressurized gases and/or gas fluids, as evidenced by the occurrence of pockmarks and seismic chimneys in upslope or adjacent areas of the scarps. Hence, earthquakes associated with tectonic activity and development of fluid overpressure may have acted as the main conditioning factor for destabilizing the slope sediments. Geotechnical stability analyses indicate that the sampled slope sediments are exceptionally stable under present-day conditions, even under seismic loading. This finding points to additional

  9. Linking River Basin Modifications and Rural Soil and Water Management Practices in Tropical Deltas to Sea Level Rise Vulnerability

    NASA Astrophysics Data System (ADS)

    Rogers, K. G.; Brondizio, E.; Roy, K.; Syvitski, J. P.

    2015-12-01

    The increased vulnerability of deltaic communities to coastal flooding as a result of upstream engineering has been acknowledged for decades. What has received less attention is the sensitivity of deltas to the interactions between river basin modifications and local scale cultivation and irrigation. Combined with reduced river and sediment discharge, soil and water management practices in coastal areas may exacerbate the risk of tidal flooding, erosion of arable land, and salinization of soils and groundwater associated with sea level rise. This represents a cruel irony to smallholder subsistence farmers whose priorities are food, water and economic security, rather than sustainability of the environment. Such issues challenge disciplinary approaches and require integrated social-biophysical models able to understand and diagnose these complex relationships. This study applies a new conceptual framework to define the relevant social and physical units operating on the common pool resources of climate, water and sediment in the Bengal Delta (Bangladesh). The new framework will inform development of a nested geospatial analysis and a coupled model to identify multi-scale social-biophysical feedbacks associated with smallholder soil and water management practices, coastal dynamics, basin modification, and climate vulnerability in tropical deltas. The framework was used to create household surveys for collecting data on climate perceptions, land and water management, and governance. Test surveys were administered to rural farmers in 14 villages during a reconnaissance visit to coastal Bangladesh. Initial results demonstrate complexity and heterogeneity at the local scale in both biophysical conditions and decision-making. More importantly, the results illuminate how national and geopolitical-level policies scale down to impact local-level environmental and social stability in communities already vulnerable to coastal flooding. Here, we will discuss components of the

  10. Sediment-water exchange of nutrients in the Marsdiep basin, western Wadden Sea: Phosphorus limitation induced by a controlled release?

    NASA Astrophysics Data System (ADS)

    Leote, Catarina; Epping, Eric H. G.

    2015-01-01

    To quantify the release of inorganic phosphorus from the sediments and assess its contribution to present primary production, a basin-wide study of the Marsdiep (western Wadden Sea, The Netherlands) was performed. Two distinct sedimentary zones were identified: a depositional area characterized by a high content of silt and organic carbon and a small grain size and the majority of the area, composed of fine/medium sand and a low organic carbon content. The sediment-water exchange was higher in the fine grained depositional area and based on a relationship found between the release of inorganic phosphorus and the silt content, a total annual release of 1.0×107 mol P was estimated for the whole Marsdiep basin. A spatial variability in the processes controlling the nutrient release was found. The exchange in the depositional area resulted mainly from molecular diffusive transport, with mineralization and sorption determining the concentration of inorganic phosphorus in the porewater. For the coarser sediment stations the activity of macrofauna clearly enhanced the fluxes. Given the relative demand of nutrients (N:P:Si) for phytoplankton growth, the release was phosphorus deficient during most of the year. Nevertheless, it increased from February until September, in parallel with the increase in temperature and light, thus having the potential to fuel primary production during their seasonal growth period. In terms of absolute values, our results show that the present exchange, enhanced by the activity of macrofauna has the potential to fuel a significant fraction of the recent levels of primary productivity.

  11. The Biodiversity of the Mediterranean Sea: Estimates, Patterns, and Threats

    PubMed Central

    Coll, Marta; Piroddi, Chiara; Steenbeek, Jeroen; Kaschner, Kristin; Ben Rais Lasram, Frida; Aguzzi, Jacopo; Ballesteros, Enric; Bianchi, Carlo Nike; Corbera, Jordi; Dailianis, Thanos; Danovaro, Roberto; Estrada, Marta; Froglia, Carlo; Galil, Bella S.; Gasol, Josep M.; Gertwagen, Ruthy; Gil, João; Guilhaumon, François; Kesner-Reyes, Kathleen; Kitsos, Miltiadis-Spyridon; Koukouras, Athanasios; Lampadariou, Nikolaos; Laxamana, Elijah; López-Fé de la Cuadra, Carlos M.; Lotze, Heike K.; Martin, Daniel; Mouillot, David; Oro, Daniel; Raicevich, Saša; Rius-Barile, Josephine; Saiz-Salinas, Jose Ignacio; San Vicente, Carles; Somot, Samuel; Templado, José; Turon, Xavier; Vafidis, Dimitris; Villanueva, Roger; Voultsiadou, Eleni

    2010-01-01

    Gibraltar and the adjacent Alboran Sea), western African coast, the Adriatic, and the Aegean Sea, which show high concentrations of endangered, threatened, or vulnerable species. The Levantine Basin, severely impacted by the invasion of species, is endangered as well. This abstract has been translated to other languages (File S1). PMID:20689844

  12. The biodiversity of the Mediterranean Sea: estimates, patterns, and threats.

    PubMed

    Coll, Marta; Piroddi, Chiara; Steenbeek, Jeroen; Kaschner, Kristin; Ben Rais Lasram, Frida; Aguzzi, Jacopo; Ballesteros, Enric; Bianchi, Carlo Nike; Corbera, Jordi; Dailianis, Thanos; Danovaro, Roberto; Estrada, Marta; Froglia, Carlo; Galil, Bella S; Gasol, Josep M; Gertwagen, Ruthy; Gil, João; Guilhaumon, François; Kesner-Reyes, Kathleen; Kitsos, Miltiadis-Spyridon; Koukouras, Athanasios; Lampadariou, Nikolaos; Laxamana, Elijah; López-Fé de la Cuadra, Carlos M; Lotze, Heike K; Martin, Daniel; Mouillot, David; Oro, Daniel; Raicevich, Sasa; Rius-Barile, Josephine; Saiz-Salinas, Jose Ignacio; San Vicente, Carles; Somot, Samuel; Templado, José; Turon, Xavier; Vafidis, Dimitris; Villanueva, Roger; Voultsiadou, Eleni

    2010-08-02

    Gibraltar and the adjacent Alboran Sea), western African coast, the Adriatic, and the Aegean Sea, which show high concentrations of endangered, threatened, or vulnerable species. The Levantine Basin, severely impacted by the invasion of species, is endangered as well. This abstract has been translated to other languages (File S1).