Forward Stratigraphic Modeling Of A Mixed Siliciclastic-Carbonate System: Mulichinco Formation, Neuquén Basin, Argentina
Event - AAPG ICE 2025
Abstract
Using 3D stratigraphic forward modeling to simulate diverse geological contexts provides quantitative tools for testing conceptual models of depositional sequences within sedimentary basins. Simulations quantify the impact of key sedimentation parameters (e.g., subsidence, sediment production, wave energy action and eustatic variations). As a result, it improves accuracy in predicting facies association distribution and geometries over the surveyed area. In this study, the mixed siliciclastic-carbonate rocks of the Mulichinco Formation in Neuquén Province, Argentina, were selected due to their complex context and an excellent outcrop exposure with extensive lateral and vertical continuity. The objective is to simulate the stratigraphic evolution of a mixed system evolving from siliciclastic paralic to offshore environments with mixed carbonate deposits, characterizing the lithostratigraphy of depositional systems in three dimensions based on one-dimensional outcrop data. Five sedimentological profiles from the Chos Malal area, Argentina were correlated, focusing on layer geometry, sedimentary facies association, stacking patterns, and stratigraphy, to create a conceptual depositional model. The units to be simulated consist of profiles ranging from 180 to 300 meters in thickness, which include deltaic, tidal, shoreface, mixed, carbonate and offshore facies associations with ages between 136 and 134.5 Ma. A proposed depositional model was used to define logical rules for the dispersion of these facies association, using proxies for paleobathymetry and wave energy to differentiate between various depositional environments. The model framework space to be filled in the simulation was generated using the backstripping method on outcrop profile thicknesses derived from the chronostratigraphic markers. Paleobathymetric maps and sea-level curve oscillation were based on paleogeographic reconstructions from previous studies in the area. The grid resolution, initial and final simulation ages, duration of each time step, and wave directions and heights were defined to calculate wave energy and run the proposed simulation. The resulting 3D facies model accurately represented the transition from deltaic and tidal facies associations of the lowstand system tract to carbonate facies of the transgressive system tract. Shoreface and offshore deposits overlie the entire area in the highstand system tract. Overall geometry and dispersion of the facies association observed in the outcrops were simulated, along with changing paleocurrents and migrating depocenters. The 3D simulation of mixed systems based on outcrop data is crucial for supporting the prediction of key properties to reproduce the heterogeneity observed in these complex geological settings.
