Organic-rich, fine-grained contourites in an epicontinental basin: The Upper Jurassic-Lower Cretaceous Vaca Muerta Formation, Argentina

• Autores: Paz, Maximiliano; Buatois, Luis; Mángano, Gabriela; Desjardins, Patricio; Notta, Raul; Gonzalez Tomassini, Federico; Carmona, Noelia Beatriz; Minisini, Daniel
• Año de publicación: 2022
• Idioma: inglés
• Tipo de recurso: artículo
• Materia: Ciencias Ambientales y de la Tierra; Vaca Muerta; Organic Rich; Neuquén; Ciencias Ambientales y de la Tierra
• Institución: Universidad Nacional de Río Negro

Fil: Buatois, Luis. Department of Geological Sciences, University of Saskatchewan, Saskatoon, SK S7N 5E2, Canada
Fil: Mángano, Gabriela. Department of Geological Sciences, University of Saskatchewan, 114 Science Place, Saskatoon, SK S7N 5E2, Canada,
Fil: Carmona, Noelia Beatriz. Universidad Nacional de Río Negro. Instituto de Investigación en Paleobiología y Geología. Río Negro; Agentina.
Fil: Paz, Maximiliano. Department of Geological Sciences, University of Saskatchewan, Saskatoon, SK S7N 5E2, Canada
Fil: Desjardins, Patricio. Shell Exploration and Production Company, 150N Dairy Ashford St, TX, 77019, Houston, USA
Fil: Notta, Raul. Shell Exploration and Production Company, 150N Dairy Ashford St, TX, 77019, Houston, USA
Fil: Gonzalez, Tomassini, Federico. Phoenix Global Resources, Alem 855, C1001AAQ, Buenos Aires, Argentina
Fil: Minisini, Daniel. Shell Technology Center Houston, 3333 South HW 6, TX, 77082, Houston, USA
Over the last few years, recognition and characterization of sedimentary processes in fine-grained successions is receiving considerable attention in part due to the increased importance of unconventional reservoirs. Recent sedimentologic analyses of these successions have revealed abundant traction transport structures that suggest bottom current activity of different origins. The present study constitutes a detailed sedimentologic analysis of the Upper Jurassic-Lower Cretaceous Vaca Muerta Formation (Neuqu´en Basin, Argentina), which comprises organic-rich, fine-grained subaqueous clinoform deposits. Locally, intervals showing traction structures such as parallel lamination, ripple cross-lamination and cross-bedding, and displaying high bioturbation, occur. These intervals can be differentiated into three facies associations, namely crinoidal mixed to calcareous mudstone, mixed to calcareous mudstone, and calcareous to mixed mudstone interbedded with calcareous mudstone. These facies associations were deposited by contour currents showing semi-permanent activity, low sediment concentration, and generating long-term oxygen supply to the seafloor. Locally, some successions display an increasing to decreasing bioturbation intensity pattern that may have a similar origin to the bi-gradational sequence of contourites. The present sedimentologic analysis supports the idea that contour currents are associated with high bioturbation levels due to increased oxygenation, which controls the degree of preservation of traction structures, and consequently the possibility to delineate these processes in fine-grained successions. These currents occurred in relatively shallow water, probably as part of a weakened estuarine or anti-estuarine, basin-wide circulation system intensified by the enhanced action of dense water cascading during arid and cool climate periods.
Over the last few years, recognition and characterization of sedimentary processes in fine-grained successions is receiving considerable attention in part due to the increased importance of unconventional reservoirs. Recent sedimentologic analyses of these successions have revealed abundant traction transport structures that suggest bottom current activity of different origins. The present study constitutes a detailed sedimentologic analysis of the Upper Jurassic-Lower Cretaceous Vaca Muerta Formation (Neuqu´en Basin, Argentina), which comprises organic-rich, fine-grained subaqueous clinoform deposits. Locally, intervals showing traction structures such as parallel lamination, ripple cross-lamination and cross-bedding, and displaying high bioturbation, occur. These intervals can be differentiated into three facies associations, namely crinoidal mixed to calcareous mudstone, mixed to calcareous mudstone, and calcareous to mixed mudstone interbedded with calcareous mudstone. These facies associations were deposited by contour currents showing semi-permanent activity, low sediment concentration, and generating long-term oxygen supply to the seafloor. Locally, some successions display an increasing to decreasing bioturbation intensity pattern that may have a similar origin to the bi-gradational sequence of contourites. The present sedimentologic analysis supports the idea that contour currents are associated with high bioturbation levels due to increased oxygenation, which controls the degree of preservation of traction structures, and consequently the possibility to delineate these processes in fine-grained successions. These currents occurred in relatively shallow water, probably as part of a weakened estuarine or anti-estuarine, basin-wide circulation system intensified by the enhanced action of dense water cascading during arid and cool climate periods.