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Characterization of Deepwater Channel System Architecture With Previous HitPalynofaciesNext Hit: An Outcrop Example From the Rosario Formation, Baja California, Mexico


Identification of architectural elements in deepwater systems is problematic without high resolution data. Here we propose a novel method to identify specific architectural elements with Previous HitpalynofaciesNext Hit, hypothesizing that organic matter will not be uniformly spread in turbidite successions. This study utilizes an integrated sedimentological and palynological dataset from outcrops of a channelized deepwater system, with the objective to classify architectural elements, e.g. confined levee or terrace deposits, based upon their Previous HitpalynofaciesNext Hit. World class outcrops of an Upper Cretaceous – Palaeocene channel-levee complex, of the Rosario Fm., Baja California, comprise the study material. System architecture is well constrained by previous work, allowing certainty in placement within the system. Architecture reflects a lateral progression from channel axis to distal elements, via overbank-terrace; confined levees internal to the channel belt; the channel-bounding external levee, with an inner and outer component, grading into hemipelagites. Combined with sedimentological logging, three hundred samples were collected from mudstones across the system. Only 10 g of sediment per sample is required for Previous HitanalysisTop of three hundred pieces of palynodebris. Samples display a wide range of palynodebris, with allochthonous terrestrial and relatively autochthonous marine materials. Results show a decrease in sorting of palynodebris away from the channel axis, where dense humic materials (e.g. degraded wood) are dominant. Lighter particles (e.g. miospores and plant cuticle) were retained in suspension at lower energy, being deposited in greater abundances in channel distal settings. The primary mechanism inferred for this distribution is hydrodynamic sorting, as the capacity of turbidity currents to transport particles reduces with distance from the sediment conduit. This result demonstrates the role of primary sediment dispersal mechanisms in controlling density stratification and distribution of organic matter in channel-levee systems. Variation in palynodebris observed in the architectural elements allows a classification scheme to be developed, enabling recognition of the depositional setting within deepwater systems. Crucially this scheme can be applied to subsurface samples to assist characterization of subsurface deepwater stratigraphic hierarchy, understanding of which is vital for prospect risking and well planning.