Architecture, internal heterogeneity and vertical evolution within a deep-water channel-levee complex: a spectacularly well-exposed outcrop from the Taza-Guercif Basin (NE Morocco)

Recent advances in high-resolution 3D seismic studies provide unprecedented imaging of deep-water sedimentary systems. However, numerous research questions persist regarding detailed facies complexity and depositional element relationships within channel-levee complexes. Hence, outcrop analysis is crucial for understanding and predicting sedimentary variability. This work focuses on a 500-meter-wide, ca. 35-meter-thick, well-exposed outcrop of a late Tortonian channel-levee complex (Complex 7) in the Tachrift Turbidite System, Taza-Guercif Basin (NE Morocco). This outcrop presents an excellent opportunity to investigate internal sedimentary heterogeneity and the vertical evolution of a channel belt at outcrop scale. Through the collection of thirty-five closely spaced stratigraphic logs, physical correlation, hierarchical arrangement of main boundary surfaces, and statistical analysis of key sedimentological variables (e.g., grain size, bed thickness, S/M ratio, etc.), three depositional units (unit 1, 2, and 3) have been identified. Different facies associations within each unit are attributed to the lateral transition between channel fills (in which lateral accreting elements and cut-and-fill elements have been distinguished) and their correlative levee deposits. The study allows the reconstruction of the stratigraphic evolution of the channel-belt: (i) a first phase is identified (Unit 1), during which lateral accreting elements follow a common migration pathway of the channel axis towards the east. Subsequently (ii), a deep erosion with sediment bypass took place, followed by the infilling of the channel and consequent vertical aggradation by cut and fill elements (Unit 2). (iii) In the final stage (Unit 3), lateral accreting elements resumed their migration pathway toward the east, preceding the deactivation of Complex 7. This study offers a detailed sedimentological characterization of different architectural element relationships within a channel-levee complex, providing valuable insights into vertical stacking development and facilitating sub-seismic lithological calibration for seismic analogues.