Seismic geomorphology and stratigraphic evolution of Eocene and Oligocene–Miocene carbonate systems, offshore western Libya

Carbonate systems represent a major component of the Paleogene–Neogene sedimentary record along the southern Mediterranean margin; however, their three-dimensional geometry, spatial distribution, and seismic expression offshore western Libya remain insufficiently constrained. This study uses 3D seismic-reflection data calibrated with borehole-geophysical information to identify, characterize, and map buried carbonate systems in the Gabes–Tripoli Basin.

The analysis is based on approximately 1200 km² of post-stack migrated 3D seismic-reflection data tied to five industrial wells from Block NC41. Integrated seismic interpretation and seismic-geomorphological analysis reveal two principal phases of carbonate development. The Eocene interval is characterized by laterally discontinuous ramp-type carbonate bodies expressed by low- to moderate-amplitude internal reflections bounded by strong top and base reflectors. Seven recurring seismic-reflection associations (EC1–EC7) are identified and interpreted to represent nummulitic ramp limestones and associated dolomitized facies.

A second phase of carbonate development occurred during the Oligocene–Miocene and is distinguished by more localized platform growth and isolated build-up geometries. These carbonates display higher seismic relief, mound-shaped external morphologies, and pronounced reflection terminations, allowing the identification of several distinct carbonate build-ups (MC1–MC3). Compared to the Eocene ramp systems, the Oligocene–Miocene carbonates reflect a shift toward platform-dominated carbonate production influenced by changes in accommodation, relative sea level, and tectonic framework.

Seismic-attribute analysis demonstrates that amplitude-, phase-, and continuity-based attributes are effective for detecting and delineating buried carbonate geobodies and for discriminating between different carbonate system types. The results provide new insights into (i) the evolution of Tertiary carbonate systems offshore Libya, (ii) the seismic expression and reservoir-scale architecture of Eocene ramp carbonates, and (iii) the transition to localized carbonate platform development during the Neogene. More broadly, this study highlights the value of 3D seismic geomorphology and attribute-based workflows for reconstructing carbonate-system evolution along tectonically influenced continental margins.