Assessing Deep Marine Sub-Environments Using Foraminifera: A Classification Model Based on Outcrop Analogues

Abstract

Deep marine sedimentary systems are globally important hydrocarbon reservoirs. Large-scale basin analysis of such systems can be seismically resolved; however, identifying the small-scale, complex depositional environments within these systems requires detailed sedimentary analysis. Outcrop analogues can be studied to help constrain the sub-environments of deep marine basins, providing a basis for interpretation of paleoenvironment and depositional setting. In this study we aim to provide a foraminiferal classification scheme based on analysis of outcrop analogues in France (Grès d'Annot), Italy (Marnoso-Arenacea) and Mexico (Rosario Formation), which can be applied to subsurface deposits. The outcrop analogues studied represent confined to ponded submarine fans (Grès d'Annot); a variably confined submarine fan to basin plain deposit (Marnoso-Arenacea); and a slope system including channels and levees (Rosario Formation). These systems have been chosen because of their comparability in age and depositional setting with deep marine sedimentary basin deposits offshore Brazil. The classification scheme will be developed with the purpose of improving knowledge of deep marine systems and related sub-environments. Foraminifera are ubiquitous in global oceans today and throughout much of the Phanerozoic, providing useful biostratigraphical and paleoenvironmental tool for the assessment of marine depositional environments. A classification scheme for use in identifying deep marine sub-environments has been established using planktic and benthic foraminifer species abundance and benthic morphogroup analysis (Jones & Charnock, 1985). This has been briefly tested on the submarine fan/channel sub-environments, Ainsa System, south-central Pyrenees, Spain (Jones et al., 2005). This study aims to fully test the morphogroup model in deep water depositional systems. Results presented here will examine the paleoenvironmental characteristics of sub-environmental facies and outline a classification model. Benthic morphogroup analysis will characterize the different benthic depositional environments, while key species of planktic and benthic foraminifera will give qualitative indications of water depth, oceanic environment and occurrences of downslope transport within the deposits. This paleoenvironmental assessment will be placed in the context of regional depositional, climatic and tectonic systems.

AAPG Datapages/Search and Discovery Article #90216 ©2015 AAPG Annual Convention and Exhibition, Denver, CO., May 31 - June 3, 2015