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Slope sediments on passive and active margins deform and fail across a broad range of scales ranging from loading and sediment remobilization near the sediment–water interface to submarine landslides and mass movements that incorporate significant volumes of slope deposits. Deformational styles are characterized by updip extension and downdip compressional features that occur above a detachment surface. Conditions for failure and deformation include the presence of weak layer(s) that serve as a detachment surface, competency contrasts that allow for detachment and downslope movement, deformation above a detachment surface, and a triggering mechanism(s) that initiates failure. Slope failure processes and products are well documented at scales resolvable by seismic-reflection surveys and in instances of extensive downslope failure, but the processes and products associated with intermediate-scale slope deformation are poorly understood. Intrastratal deformation is defined as stratigraphically isolated zones of deformation bounded above and below by concordant and undeformed strata. In this study, outcrop examples of intrastratal deformation from the Upper Cretaceous Tres Pasos Formation are used to elucidate the influence of depositional architecture on slope deformation. The facies distribution associated with compensational stacking of lobe deposits is shown to have a first-order control on the location and style of deformation. Detachment planes that form in mudstone deposits associated with lobe fringe and interlobe deposits are spatially limited and deformation is restricted to interbedded sandstone and mudstone associated with off-axial lobe positions. Downslope translation was arrested by stratigraphic buttresses associated with more sandstone-prone axial deposits. Emplacement of a regionally extensive mass transport deposit is interpreted as the triggering mechanism for contemporaneous intrastratal deformation of > 60 m of underlying stratigraphy. A vertical increase in ductile deformation through the deformation interval indicates the role of burial depth and compaction. Distinguishing synburial intrastratal deformation (10s of m below seafloor) from tectonic or at-seafloor deformation has important implications for interpretations of burial history, slope stability, and potential triggering mechanisms. [ABSTRACT FROM AUTHOR]

This study investigates the depositional architecture of turbidite lobes from the Southern Laga Basin (Lower Messinian, Central Apennines) and the external controls on its development. Physical stratigraphy and facies analysis on a 1700 m thick interval enabled us unraveling the hierarchical partitioning and internal arrangement of lobes from four units with different degree of topographic confinement. A four-fold hierarchy of depositional bodies was recognized including: i) event beds deposited by single turbidity currents: ii) single lobes, consisting of bed sets with variable degree of sand amalgamation; iii) lobe sets, i.e. depocentre-wide stacks of single lobes and iv) lobe complexes, representing high rank units of greater internal complexity. Field mapping of the studied lobes highlighted a significant change in size and morphology of the receiving depocentre resulting from sediment filling and onlapping of basinal slopes. The lobe depocentre evolved from a funnel-shaped trough with an initial size of ∼150 km 2 to a wider basin reaching a maximum extent of over 500 km 2 , which implies decreasing degree of confinement from older to younger lobes. Comparison of depositional architectures across the studied units points out two end-members: i) confined sheet-like lobes, consisting of topography contained sandbodies with flat geometry and little facies variability in their axial part and ii) semi-confined lobes with a ‘jigsaw’ architecture, comprised of shingled to compensated depositional bodies with lobate to sigmoidal planform and highly variable facies partitioning. The former architecture is interpreted as the product of flow containment of incoming flows by lateral basinal slopes with consequent deposition under confined accommodation space, whereas the latter would record sedimentation within a wider depocentre allowing for free flow expansion and lateral migration of lobes. The different architecture of confined vs. semi-confined lobes has important implications for the hydrocarbon industry as it results in significantly dissimilar structures of permeability and connectivity. [ABSTRACT FROM AUTHOR]

Coastal areas contain interfaces between complex depositional systems as a consequence of the convergence of marine and continental environments. The knowledge of such complex depositional systems is important in understanding of coastal evolution and for coastal management. The present study deals with the subsurface identification of interfaces between fluvial and beach/shallow marine systems, using Ground Penetrating Radar (GPR). GPR profiles were measured along dip direction, at two sites on the coastal plain of Santa Catarina state (Pinheira and Passo de Torres), where deposits of fluvial and beach/foredune ridge systems occur. GPR data showed that fluvial and beach deposits are interdigitated in subsurface, with reflectors showing different downlap directions. The results of this study allow a more complete knowledge of the complex interfaces between marine and continental systems. Also, the identification of hidden older fluvial deposits in the subsurface of coastal plains gives important geotechnical information to be considered in the use and occupation of coastal areas and during prospection for placer deposits. [ABSTRACT FROM AUTHOR]

According to the different geometries and reflected characteristics in the seismic sections, the carbonate platform margin of the northern slope can be summarized as three basic depositional architectures in the Late Ordovician Lianglitage (良里塔格) Formation of the Tazhong (塔中) uplift. The type one mainly located in the west of the carbonate platform margin, and it showed obvious imbricate progradation from the interior to the margin of the platform. The type two was in the middle of the carbonate platform margin, which showed retrogradational stacking pattern in the same transgressive systems tract period, and the slope strata of the platform margin showed progradational sequence in the highstand systems tract period. The type three located in the east of the carbonate platform margin, and it showed the parallel aggradational architecture. The crossing well section along the northern slope of the Tazhong carbonate platform showed that the depositional thickness became thinner from the east to the west. The thickest belt located in the east of the platform margin, and became thinner rapidly towards the basin and the platform interior. These indicated that the paleogeomorphology of the Tazhong uplift was probably high in the west and low in the east during the period of the Late Ordovician Lianglitage Formation. According to the interpretation of seismic profiles and the computer modelling result, the depositional architectures of sequence O l-2 showed aggradation, retrogradation and progradation from the east to the west of the carbonate platform margin during the transgression period. This meant that the accommodation became smaller gradually from the east to the west along the northern carbonate platform margin of the Tazhong uplift. The difference of the accommodation was probably caused by the difference of tectonic subsidence. Also, computer-aided modelling can be used to deeply understand the importance of various control parameters on the carbonate platform depositional architectures and processes. [ABSTRACT FROM AUTHOR]