Contourite depositional system after the exit of a strait: Case study from the late Miocene South Rifian Corridor, Morocco

Idealized facies of bottom current deposits (contourites) have been established for fine-grained contourite drifts in modern deep-marine sedimentary environments. Their equivalent facies in the ancient record however are only scarcely recognized due to the weathered nature of most fine-grained deposits in outcrop. Facies related to the erosional elements (i.e. contourite channels) of contourite depositional systems have not yet been properly established and related deposits in outcrop appear non-existent. To better understand the sedimentary facies and facies sequences of contourites, the upper Miocene contourite depositional systems of the South Rifian Corridor (Morocco) is investigated. This contourite depositional system formed by the dense palaeo-Mediterranean Outflow Water. Foraminifera assemblages were used for age-constraints (7.51 to 7.35 Ma) and to determine the continental slope depositional domains. Nine sedimentary facies have been recognized based on lithology, grain-size, sedimentary structures and biogenic structures. These facies were subsequently grouped into five facies associations related to the main interpreted depositional processes (hemipelagic settling, contour currents and gravity flows). The vertical sedimentary facies succession records the tectonically induced, southward migration of the contourite depositional systems and the intermittent behaviour of the palaeo-Mediterranean Outflow Water, which is mainly driven by precession and millennial-scale climate variations. Tides substantially modulated the palaeo-Mediterranean Outflow Water on a sub-annual scale. This work shows exceptional examples of muddy and sandy contourite deposits in outcrop by which a facies distribution model from the proximal continental slope, the contourite channel to its adjacent contourite drift, is proposed. This model serves as a reference for contourite recognition both in modern environments and the ancient record. Furthermore, by establishing the hydrodynamics of overflow behaviour a framework is provided that improves process-based interpretation of deep-water bottom current deposits

The Barra Fan: a bottom-current reworked, glacially-fed submarine fan system

On the basis of sedimentary structures, textures and ichofauna, seven depositional facies have been recognised in cores from the Barra Fan region of the Hebrides slope. Sedimentary facies are combined into three genetic groups A–C that represent their primary mode of deposition: (A) sandy to muddy contourite facies A, A1, and A2, which represent an overall coarsening upward sequence caused by an increase in bottom-current velocity over time; (B) disorganised glaciomarine deposits, including the glaciomarine dumpstone of facies B and facies B1 deposited as a result of ice-rafting and glaciomarine sedimentation; and (C) hemipelagite facies C and C1 which are the result of normal marine hemipelagic settling. It is most likely that all contourite facies (A–A2) identified in this study are Holocene (<10,000 y) in age and that the underlying glaciomarine and hemipelagite facies (groups B and C) were deposited during the last glacial period.In terms of its diverse morphological elements and varied facies, this high latitude submarine fan is truly composite in nature. However, a broad three-stage glacial to post-glacial evolutionary system is recognised, during which different processes and process combinations were dominant. During the last glacial period (low stand system tract), downslope processes, including debris flows and minor turbidity currents, sculpted an irregular slope topography. Little in the way of bottom current activity was evident. Staged deglaciation was accompanied by rising sea level and high sedimentation rates across the region. This created an unstable margin prone to extensive sliding and slumping, that masked any effects of an incipient alongslope current. The present high stand system tract is dominated by a strong slope current that became fully active during the early part of the Holocene. Low sedimentation rates, diminished sediment supply and strong bottom current activity led to development of the sandy contourite sheeted drift system across the mid-slope region. Little downslope movement is evident during this period, so that the slope topography is being slowly smoothed and remoulded by active bottom currents

Assessment of automated multitemporal image co-registration using repeat station imaging techniques

Repeat station imaging (RSI) is a method for specialized image collection and co-registration that facilitates rapid change detection with aerial imagery for time-critical analyses. Our previously reported research has defined methods for automated multitemporal image co-registration and demonstrated the utility of RSI for achieving precise co-registration, but without actually automating the technique. For this paper, we developed a custom software implementing specific procedures for automated RSI-based image co-registration, processed 252 image pairs containing diverse scenes and collection conditions, and evaluated the performance of RSI and the auto-registration tool. We found that the average root-mean-square error of image co-registration ranged between 1.3 and 1.9 pixels for aerial RSI images with 8–14 cm spatial resolution captured at the same time of day. The implications of these findings are that automated multitemporal co-registration and automated change detection could be performed in near real-time onboard an aircraft as it flies, opening up a range of new monitoring applications, particularly with unmanned aircraft systems. However, results with our custom software also indicate that images captured at different times of day with varying illumination and shadow conditions yield poor co-registration, and in some instances fail to register

Petroleum potential of the Falkland Islands offshore area

Rocks of Precambrian, Palaeozoic and Early Mesozoic ages are present on the Falkland Islands. The islands are surrounded by extensive Mesozoic-Cenozoic basins that developed as failed rift systems during the initial stages of Gondwana separation. Large tracts of acreage in three of these basins (the Falkland Plateau Basin, South Falkland Basin and North Falkland Basin) were opened for licensing for the first time in October, 1995. The area has undergone little exploration other than the acquisition of regional seismic data, and interpretations of stratigraphy and basin history are therefore somewhat conjectural. The basins are believed to contain Jurassic to earliest Cretaceous syn-rift sediments. Probable marine and lacustrine source rocks, and reservoir rocks eroded from clean Palaeozoic quartzites, are predicted to occur within this syn-rift succession. Thick argillaceous intervals probably accumulated during a post-Valanginian thermal sag phase. This sag phase was interrupted by regional uplift, particularly during the Early Cenozoic. A variety of “play” concepts can be established within each basin, and potentially large structural targets can be defined on the reconnaissance seismic data available from the area. The region is considered to be one of the World's last true “frontier” exploration areas, where large, deep, Mesozoic failed-rift basins remain to be drilled and explored