Subduction consequences along the Andean margin : thermal and topographic signature of an ancient ridge subduction in the Marañón Basin of Perú

All along the eastern border of the Andes lie foreland basins that are among the most prolific hydrocarbon provinces of the world. Their Cenozoic evolution was controlled by the Andean uplift and its consequences on deformation and sedimentation. In turn, the Andean uplift results from the interplay between the subducting Nazca oceanic plate and the South American continental plate. Although the process exists all along the margin, the subducting plate is not regular including bathymetric anomalies and segments that result in different response in the deformation and active volcanism of the overriding plate. In the Marañón Basin of Peru, evidences allow documenting the consequences of a topographic anomaly subduction on the thermal regime and deformation of the Andean foreland during the Neogene. In this basin, a maturity anomaly is difficult to explain by considering only the present day thermal regime. However, it spatially coincides with the trace of a lost subducting ridge, the Inca Plateau. Other features like differential uplift and erosion can be related to the same event in the area. We review the consequences of oceanic ridge subduction along the Andean margin. Their effects on the deformation and volcanism of the forearc and arc regions have been extensively described. Their influence on the present day foreland topography is testified by the existence of giant alluvial fans and displaced terraces. Their effect on magmatism and ore deposits formation has also been demonstrated. The example illustrated here shows that their influence on thermal regime, deformation, erosion and ultimately on petroleum systems must also be taken into account in the search for hydrocarbons in subduction related basins

Subduction consequences along the Andean margin: thermal and topographic signature of an ancient ridge subduction in the Marañón Basin of Perú

All along the eastern border of the Andes lie foreland basins that are among the most prolific hydrocarbon provinces of the world. Their Cenozoic evolution was controlled by the Andean uplift and its consequences on deformation and sedimentation. In turn, the Andean uplift results from the interplay between the subducting Nazca oceanic plate and the South American continental plate. Although the process exists all along the margin, the subducting plate is not regular including bathymetric anomalies and segments that result in different response in the deformation and active volcanism of the overriding plate. In the Marañón Basin of Peru, evidences allow documenting the consequences of a topographic anomaly subduction on the thermal regime and deformation of the Andean foreland during the Neogene. In this basin, a maturity anomaly is difficult to explain by considering only the present day thermal regime. However, it spatially coincides with the trace of a lost subducting ridge, the Inca Plateau. Other features like differential uplift and erosion can be related to the same event in the area. We review the consequences of oceanic ridge subduction along the Andean margin. Their effects on the deformation and volcanism of the forearc and arc regions have been extensively described. Their influence on the present day foreland topography is testified by the existence of giant alluvial fans and displaced terraces. Their effect on magmatism and ore deposits formation has also been demonstrated. The example illustrated here shows that their influence on thermal regime, deformation, erosion and ultimately on petroleum systems must also be taken into account in the search for hydrocarbons in subduction related basins.All along the eastern border of the Andes lie foreland basins that are among the most prolific hydrocarbon provinces of the world. Their Cenozoic evolution was controlled by the Andean uplift and its consequences on deformation and sedimentation. In turn, the Andean uplift results from the interplay between the subducting Nazca oceanic plate and the South American continental plate. Although the process exists all along the margin, the subducting plate is not regular including bathymetric anomalies and segments that result in different response in the deformation and active volcanism of the overriding plate. In the Marañon Basin of Peru, evidences allow documenting the consequences of a topographic anomaly subduction on the thermal regime and deformation of the Andean foreland during the Neogene. In this basin, a maturity anomaly is difficult to explain by considering only the present day thermal regime. However, it spatially coincides with the trace of a lost subducting ridge, the Inca Plateau. Other features like differential uplift and erosion can be related to the same event in the area.We review the consequences of oceanic ridge subduction along the Andean margin. Their effects on the deformation and volcanism of the forearc and arc regions have been extensively described. Their influence on the present day foreland topography is testified by the existence of giant alluvial fans and displaced terraces. Their effect on magmatism and ore deposits formation has also been demonstrated.This example illustrated here shows that their influence on thermal regime, deformation, erosion and ultimately on petroleum systems, must also be taken into account in the search for hydrocarbons in subduction related basins

Subduction consequences along the Andean margin: thermal and topographic tignature of an ancient ridge subduction in the Marañon Basin of Perú

The detailed analysis of a dense 2D seismic reflection dataset and data from 8 exploration wells, allowed us to identify, map out and characterize possible indications of past and present-day hydrocarbon leakage (i.e. gas chimneys, gas pockets, and seafloor mounds and pockmarks) on the continental shelf and slope of the Colorado Basin, offshore Argentina, where Permian, Jurassic and Early Cretaceous source rocks are potentially present and may be currently mature. Identified gas leakage features, developed both in the syn-rift and post-rift successions, were also analysed in relation to the structural the stratigraphic elements of the basin. A family of seabed pockmarks, located close to an array of submarine channels, was identified on the distal slope of the basin. These pockmarks are overlying a series of sub-vertical to vertical seismic chimneys in the subsurface. A calibrated basin-wide 3D petroleum system model comprising generation and migration of hydrocarbons was carried out and compared with the observations from the seismic analysis. Preliminary results from this model indicate that although synrift and early Cretaceous source rock (SR) intervals may be depleted in the central areas of the basin, an active kitchen from the Aptian SR may be present below the slope areas. Hydrocarbon migration pathways predicted by the 3D model (Hybrid method) coincide with the interpreted seismic chimneys underlying the observed seabed slope pockmarks. Hence, our results indicate that thermogenic gas may be currently generated in the distal slope of the basin from mature early post-rift source rocks within the Early Cretaceous (Aptian) sequences and migrates vertically, due to seal failure, through the stratigraphic column. This migrating thermogenic gas is feeding the seafloor pockmarks identified in the distal slope of the basin, although up-dip lateral migration along stratigraphic layers to the more proximal slope areas cannot be ruled out. The present work represents the first published study integrating detailed seismic analysis and 3D basin modelling linking observed gas-leakage indicators and associated seepage pathways, to their relative abundance, distribution and feeding systems offshore Argentina's continental margin

Subduction consequences along the Andean margin : thermal and topographic signature of an ancient ridge subduction in the Marañón Basin of Perú

All along the eastern border of the Andes lie foreland basins that are among the most prolific hydrocarbon provinces of the world. Their Cenozoic evolution was controlled by the Andean uplift and its consequences on deformation and sedimentation. In turn, the Andean uplift results from the interplay between the subducting Nazca oceanic plate and the South American continental plate. Although the process exists all along the margin, the subducting plate is not regular including bathymetric anomalies and segments that result in different response in the deformation and active volcanism of the overriding plate. In the Marañón Basin of Peru, evidences allow documenting the consequences of a topographic anomaly subduction on the thermal regime and deformation of the Andean foreland during the Neogene. In this basin, a maturity anomaly is difficult to explain by considering only the present day thermal regime. However, it spatially coincides with the trace of a lost subducting ridge, the Inca Plateau. Other features like differential uplift and erosion can be related to the same event in the area. We review the consequences of oceanic ridge subduction along the Andean margin. Their effects on the deformation and volcanism of the forearc and arc regions have been extensively described. Their influence on the present day foreland topography is testified by the existence of giant alluvial fans and displaced terraces. Their effect on magmatism and ore deposits formation has also been demonstrated. The example illustrated here shows that their influence on thermal regime, deformation, erosion and ultimately on petroleum systems must also be taken into account in the search for hydrocarbons in subduction related basins

A scenario for late Neogene Andean shortening transfer in the Camisea Subandean zone (Peru, 12 degrees S) : Implications for growth of the northern Andean Plateau

Precise knowledge of the timing of deformation in the Subandean zone of the Andean Plateau is a prerequisite for deciphering the late Neogene growth of the Andean Plateau. In this paper, we report new apatite fission-track (AFT) and vitrinite reflectance (Ro) data for a regional balanced cross section of the Camisea Basin in the central Peruvian Subandean zone, adjacent to the northern Andean Plateau. The balanced cross section shows that the structure of this basin is characterized by a broad internal passive roof duplex and external thrust-related anticlines. The balanced cross-section restoration shows 53 km (39%) of total horizontal shortening. We sampled Paleozoic to Cenozoic sedimentary strata for AFT and Ro analyses along the similar to 4-km-thick vertical profile of the Mainique back thrust (passive roof thrust), the innermost preserved Subandean structure. Young components of AFT ages are spread between ca. 6 Ma and ca. 24 Ma. A break in the slope in the AFT ages determines the geometry of the Miocene partial annealing zone and the exhumation of the Mainique back thrust at ca. 6 Ma. Sequential restoration calibrated by AFT and Ro data indicates that the last similar to 23 km horizontal shortening were accommodated by the Camisea thrust system over the past similar to 6 m.y., giving a mean shortening rate of 3.8 mm/yr. Using this shortening rate for the first similar to 30 km horizontal shortening, we calculate that the Andean shortening transfer into the Peruvian Subandean zone initially started at ca. 14 Ma. This result suggests that the transfer of shortening from the northern Andean Plateau to the Subandean zone occurred prior to the removal of dense lithosphere previously reported to have occurred between ca. 10 Ma and ca. 7 Ma. We rather propose that the late Neogene growth of the northern Andean Plateau mostly resulted from a continuous crustal shortening combined with lower-crustal flow

A scenario for late Neogene Andean shortening transfer in the Camisea Subandean zone (Peru, 12°S) : implications for growth of the Northern Andean Plateau

International audienc

A scenario for late Neogene Andean shortening transfer in the Camisea Subandean zone (Peru, 12°S) : implications for growth of the Northern Andean Plateau

International audienc