SEDIMENTARY ARCHITECTURE AND INTERNAL HETEROGENEITY OF TURBIDITE CHANNEL-LEVEE DEPOSITS: THE TACHRIFT TURBIDITE SYSTEM (LATE TORTONIAN, TAZA-GUERCIF BASIN, NE MOROCCO)

Turbidite channel-levee deposits have been studied for over fifty years, both in modern and ancient deep-water systems. Recent advances in 3D seismic imaging have improved our understanding of these systems, yet the internal facies complexity remains elusive. Studying well-exposed outcrops is essential to fill this gap, offering detailed insights into sedimentary heterogeneity. This knowledge is not only crucial for scientific research but also for hydrocarbon exploration and groundwater management, and carbon capture industry as these systems serve as significant reservoirs. Despite recent advancements, understanding the detailed internal structure and evolution of turbidite channel-levee deposits is limited due to the low resolution of subsurface data. The lack of continuous outcrop exposures showing the relationship between channel-fills and levee deposits further complicates model calibration. This thesis aims to address these gaps through detailed documentation of well-exposed ancient channel-levee deposits. The study area is located in the Taza-Guercif Basin, northeastern Morocco and was part of the Rifian Corridor, a key marine connection between the paleo-Mediterranean Sea and the Atlantic Ocean during the Late Miocene. The basin preserves a series of late Tortonian to early Messinian turbidite systems, including the Tachrift Turbidite System, which features multiple channel-levee deposits. This PhD work is part of a larger project called the 'Tachrift Project’, which focuses on the sedimentary characterization of the nine superimposed channel-levee deposits within the Tachrift Turbidite System (late Tortonian to early Messinian) in the Taza-Guercif Basin, NE Morocco. As part of this broad research project involving numerous researchers from different universities, the thesis focuses on Complexes 5 and 7, two of the nine superimposed channel-levee deposits within the Tachrift Turbidite System. The exceptional outcrop quality offers valuable data on channel-fill and levee deposits, providing a rare opportunity to study these features at a sub-seismic resolution. This research contributes to refining models of sedimentary heterogeneity and improving our understanding of similar subsurface analogs. A classical sedimentological approach was applied, including geological mapping, facies analysis, and physical stratigraphic correlation. Over 130 stratigraphic logs were collected across multiple outcrops oriented along strike and along dip and covering both lateral and vertical facies variability. Key sedimentary parameters were used to assess sedimentary heterogeneity. These data provide a basis for reconstructing the evolution, architecture and sedimentary heterogeneity of channel-levee deposits. This detailed study, integrated with previous research conducted within the turbidite system, has enabled the identification of two main depositional styles of channel-levee deposits, each characterized by different architectural elements and facies associations. The first depositional style, termed 'Erosional channel-fills,' is characterized by a symmetrical distribution of facies relative to the channel axis and is the product of high-energy flows that incise and progressively fill conduits that range from straight to low-sinuosity. The second style refers to 'Laterally accreting channels,' which exhibit high sinuosity with asymmetrical facies distributions and geometries, along with lateral migration, reflecting lower energy conditions. Both studied Complexes 5 and 7 displayed a similar depositional evolution, beginning with the deposition of highly sinuous, ephemeral, and small-scale channels, followed by phases of progressively increasing flow energy and magnitude, leading first to the development of distributary channels with significant lateral expansion and low aggradation (Laterally accreting elements), and later to straighter, more incisional channels (Erosional channel-fills). During the deposition of each channel-levee complex, these conditions of lateral expansion versus aggradation can alternate, creating a highly complex stacking pattern. The deactivation of both complexes is abrupt and marked by the presence of thick marlstone intervals. This thesis, which also involved the quantification of key sedimentological variables such as bed thickness, grain size, and net-to-gross ratios, contributes to a deeper understanding of turbidite channel-levee complexity and offers important analogues for subsurface exploration and resource management.