1,721,007 research outputs found
Submarine slope degradation and aggradation and the stratigraphic evolution of channel-levee systems
Full text linkTwo seismic-scale submarine channel–levee systems exposed in the Karoo Basin, South Africa provide insights into slope conduit evolution. Component channel fills in a levee-confined channel system (Unit C) and an entrenched channel system (Unit D) follow common stacking patterns; initial horizontal stacking (lateral migration) is followed by vertical stacking (aggradation). This architecture is a response to an equilibrium profile shift from low accommodation (slope degradation, composite erosion surface formation, external levee development, sediment bypass) through at-grade conditions (horizontal stacking and widening) to high accommodation (slope aggradation, vertical stacking, internal levee development). This architecture is likely common to other channel–levee systems
Intrinsic controls on the range of volumes, morphologies, and dimensions of submarine lobes
No full textStratigraphic architecture of an outcropping ancient slope system: Tres Pasos Formation, Magallanes basin, Southern Chile
No full textAge control on the Tanqua and Laingsburg deep-water systems: New insights on the evolution and sedimentary fill of the Karoo basin, South Africa
No full textSLOPE Phase 2: sponsors’ third field workshop, Laingsburg Karoo, South Africa
No full textOutcrops of the Permian ecca Group in the southwestern Karoo basin are outstandingly well exposed and easily accessible. Present day erosion allows viewing of laterally continuous (tens of kilometres) outcrops in the Tanqua and Laingsburg depocentres. Key objectives of this report are:
-To illustrate the downdip and across-strike changes in facies, incisional styles, channel dimensions,in-complex and out-of-complex net:gross variations and the internal stratigraphy of Unit C and D;
-Discussion of seismically resolvable surfaces, geometries and volumes and uncertainties in estimating facies, net:gross and reservoir quality from seismic alone;
to build further on the Vischkuil story, variability of MTDs, run out distances, etc. and to discuss the effects of depositional vs tectonic topography on facies, geometries and thichness of lower Fan A;
-Examination of different types of channel, channel complex, and channel complex set, related to different profile positions. Discussion on the relative amounts of lateral spill vs bypass vs in-channel aggradation and the implications for axis to margin to overbank sand connectivity;
-To introduce and debate a sequence stratigraphic hierarchy for the slope succession
SLOPE Phase 2: sponsors’ second field workshop, Laingsburg Karoo, South Africa
No full textOutcrops of the Permian ecca Group in the southwestern Karoo basin are outstandingly well exposed and easily accessible. Present day erosion allows viewing of laterally continuous (tens of kilometres) outcrops in the Tanqua and Laingsburg depocentres. Key objectives of this report are:
-Discussion of seismically resolvable surfaces, geometries and volumes and uncertainties in estimating facies, net:gross and reservoir quality from seismic alone;
-Assesment of the role of depositional topography (related to mass-transport deposits) compared to active growth of topography during episodic deformation of the seabed;
-Differentiation of lower slope from basin floor settings and characterisation of lower and middle slope channel-overbank complexes;
-development of criteria to recognise and assess bypass processes in slope settings and implications for down-dip sand supply;
-Examination of different types of channel, channel complex, and channel complex set, related to different profile positions. Discussion on the relative amounts of lateral spill vs bypass vs in-channel aggradation and the implications for axis to margin to overbank sand connectivity;
-Recognition of facies and facies associations, based on depositional processes, vertical succession and geometry, using outcrop, core and wireline logs;
-Appreciation of the strong stratigraphic control on distribution of reservoir permeability extremes and their capture in reservoir models;
-Discussion of approaches to building reservoir models of deep-water systems
U-PB zircon tuff geochronology from the Karoo Basin, South Africa: implications of zircon recycling on stratigraphic age controls
No full textU-Pb zircons ages from the southwestern Karoo Basin, South Africa – Implications for the Permian-Triassic boundary
No full textDecoupling seasonal fluctuations in fluvial discharge from the tidal signature in ancient deltaic deposits: an example from the Neuquén Basin, Argentina
Full text linkFluvial discharge fluctuations are a fundamental characteristic of almost all modern rivers and can produce distinctive deposits that are rarely described from ancient fluvial or mixed-energy successions. Large-scale outcrops from the Middle Jurassic Lajas Formation (Argentina) expose a well-constrained stratigraphic succession of marginal-marine deposits with a strong fluvial influence and well-known tidal indicators. The studied deposits show decimetre-scale interbedding of coarser- and finer-grained facies with mixed fluvial and tidal affinities. The alternation of these two types of beds forms non-cyclic successions that are interpreted to be the result of seasonal variation in river discharge, rather than regular and predictable changes in current velocity caused by tides. Seasonal bedding is present in bar deposits that form within or at the mouth of minor and major channels. Seasonal bedding is not preserved in channel thalweg deposits, where river flood processes were too powerful, or in floodplain, muddy interdistributary-bay, prodelta and transgressive deposits, where the river signal was weak and sporadic. The identification of sedimentary facies characteristic of seasonal river discharge variations is important for accurate interpretation of ancient deltaic process regime
- …
