Aeolian and fluvial interactions from the cretaceous in the Neuquén Basin, Argentina: Examples from outcrop and subsurface

JOAQUÍN PÉREZ MAYORAL; AGUSTÍN ARGÜELLO SCOTTI; GONZALO D VEIGA

Beijing

Congreso; 21st International Sedimentological Congress; 2022

International Asossiation of Sedimentologists

The close interaction between aeolian and fluvial processes is seen often in the accumulation systems linked to arid to hyper-arid conditions, especially in the margin sectors of dune fields or erg systems (Al-Masrahy & Mountney, 2015). The results of these interactions can be observed in different both spatial and temporal scales, generated by the contraction and expansion of this erg system due to external changes such as climate variations (Langford y Chan, 1989). However, the sedimentary record generated by these hybrid accumulation systems is far from being fully understood. The aim of this work is to study several units which are known to record fluvial and aeolian interaction processes; and characterize the record of distinct types and scales of fluvio-aeolian interaction, suggesting possible analogous processes in modern environments. The studied units all belong to the Mesozoic record of the Neuquén Basin. The Candeleros Formation (Candia Halupczok et al., 2018; Pérez Mayoral et al., 2021) and the Troncoso Member from Huitrín Formation (Argüello Scotti, 2018) were studied on outcrop; while the Avilé Member from Agrio Formation (Veiga et al., 2002) was studied at the subsurface. The latter two are important because they are reservoirs, so the identification of lateral variations that the architectural elements have is important to measure the compartmentation and the heterogeneities of the reservoirs associated with this type of depositional systems. In addition, the comprehension of the variety these have in comparison to modern systems, how they are transferred to the geological record and what is the extent of their impact on the record on a detailed scale are topics that need to be further discussed. Hence, a classical sedimentological analysis was performed, including the logging of sedimentary sections; facies and architectural analysis; and the identification of the hierarchies of unconformities (Kocurek, 1988, Clemmensen & Tirsgard, 1990). More than 800 meters of logs at a 1:20 scale were collected. A photogrammetry model made in one of the units, allowed to measure the extension of some of the architectural elements and bounding surfaces. As a result, a unit-independent facies and architectural elements scheme was developed, which included at least 3 aeolian-related facies and 11 facies related to fluvial or water presence-related processes. The architectural elements identified were: aeolian dune elements, sheet mantle elements, wet interdune elements, damp interdune elements, channelized fluvial elements, nonchannelized proximal fluvial elements, non-channelized distal fluvial elements, and playa-lake elements. Thisstudy was conducted to partially recognize at least two different scales of interaction both spatially and temporally. The comprehension of the nature and expression of these fluvial and aeolian interactions is useful for the prediction and interpretation of similar deposits in the subsurface (Taggart et al., 2010; Fryberger et al., 2011) such as the Avilé Mb example studied. Therefore, it provides relevant inputs for reservoir modeling for hydrocarbon development or CO2 storage purposes. Furthermore, the identification of geometries and spatial/temporal relationships between the elements that constitute the record analyzed allows finding modern analogs that can also help understand the way these sedimentary systems operate.