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This study describes an integrated workflow designed to quantify detrital input into lacustrine deposits in terms of regional extent and total organic carbon content. This workflow includes (a) organic geochemical data such as Rock Eval and palynofacies and (b) palaeogeographical maps. This workflow was applied to the immature Barremian source rocks from the Lower Congo Basin because of a large available data set describing a complex sedimentary record. From palynofacies analysis, it was demonstrated that lacustrine organic matter corresponds to a hydrogen index higher than 600 mg/g C whereas detrital input corresponds to a hydrogen index lower than 300 mg/g C. The range seen in the hydrogen index of between 300 and 600 mg/g C corresponds to mixtures of organic matter. The correlation between the hydrogen index and detrital content was then applied to 50 wells which allowed the extent of detrital input to be mapped at local and regional scales. The geochemical data were plotted on high‐resolution palaeogeographic maps for four stratigraphic intervals, BA2, BA2‐BA3, BA3‐PN and BA3‐PI. Results confirm the periodic presence of lacustrine turbiditic systems allowing strong detrital inputs into the palaeolake under the tropical palaeoclimate, especially in the BA2‐BA3 and BA3‐PI intervals. These inputs of continental‐derived organic material degrade the quality and richness of the lacustrine source rock leading to a decrease of the initial hydrogen index values. These detrital influxes were related to coastal rivers whereas, in the deepest parts of the basin, the autochthonous organic matter is well‐preserved and not diluted, which allowed the deposition of exceptional source rocks especially during the BA2 and BA2‐BA3 intervals. All of these geochemical diagnostics are consistent with available palaeogeographic maps. This study demonstrated the importance of integrating geochemical data into the palaeo‐reconstruction of the source rock depositional environment. It enables palaeogeographic maps to be constrained in terms of both detrital input and preservation at both regional and local scales for a given source rock.

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A buried system was observed using seismic data along the northern side of the Roussillon coastal plain and inner shelf (Western Gulf of Lion, Mediterranean Sea) far from the nearest Agly and Têt rivers. It was interpreted as an example of a ''compound'' type, which is subject to controversy.A core 60 meters long was obtained on the sandy beach barrier between sea and lagoon approximately on the axis of the basal surface of erosion mapped from seismic data and long core logs obtained previously on the coastal plain.In the lower part of the core (264 m to 226 m b.p.s.l.) the main estuarine muddy-silt facies and thin levels of fluvial gravels intercalated in the mud suggest that successive cycles of base-level and sea-level falls and rises were recorded. This interpretation is confirmed by pollen diagrams showing several successive warming periods during climatic changes (differentiated as ''interglacial'' phases) recorded by the estuarine muds. Owing to these correlated data we can attest that this incised-valley system is of a ''compound'' type.Every vertical succession of fluvial gravels and estuarine muddy silts represents a fundamental depositional sequence typical of the ''simple'' model of wave-dominated incised-valley filling, truncated at the top by a subsequent base-level fall. Several depositional sequence remnants are stacked upon each other.The chronostratigraphic benchmark is based on microforaminiferal biomarkers which indicate that the time period covered by the successive phases of base-level and sea-level cycles extends from MIS 16 (about 600,000 years B.P.) to MIS1 (present day). The exact correlation of base level and sea level cycles with identified climate cycles remains partly approximate, but the cycles which contain well-known plant associations are quite reliable.The internal geometry of the incised-valley system, based upon high-resolution seismic data, shows that the lateral migration of the successive phases of incision and filling explains both the preservation of several cycles and the incomplete preservation of the typical facies due to the reworking of the upper part of all individual depositional sequences.Eustasy is the dominant controlling factor, and differential subsidence, an important factor on the mid and outer shelf, has a reduced impact at this location. The preservation of the ''compound'' system depends upon the variable maximum depth of erosion reached at each maximum sea-level lowstand. We propose that different interglacial conditions took place in the drainage basins, rather than differences in the lowstand-sea-level values. The transverse shape of the incisions, with lateral terraces and deeper channels, combined with a continuous lateral shift of the successive incisions, also contributed to preservation. The lateral shifting is partly due to a normal fault and substratum tilting, and partly to the oceanic regime.