Seismic Geomorphology of Karst in Cretaceous to Early Cenozoic Carbonates of North Kuwait

• Published in: Marine and petroleum geology 2021-06, Vol.128, p.104947, Article 104947
• Main Authors: Cross, Nigel E., van Veen, Leendert-Jan, Al-Enezi, Abdulmohsen, Singh, Sunil, van Beusekom, Govert
• Format: Article
• Language: English
• Subjects: Carbonate reservoir; Epigene; Hypogene; Karstification; Kuwait
• ISSN: 0264-8172; 1873-4073
• DOI: 10.1016/j.marpetgeo.2021.104947

The carbonate-dominated, mid-Cretaceous to early Cenozoic stratigraphy of north Kuwait exhibits seismic evidence for karstification at multiple stratigraphic levels. Seismic coherence and attribute data sculptured across mapped stratigraphic horizons, isochrons and cross-sections reveal a complex distribution of karstic geomorphology. Seismic facies have been rationalized into seismic facies associations (SFA) - SFA-1: small-scale dolines, sinkholes and polygonal channels, SFA-2: large-scale dissolution pipes and coalesced pipes, SFA-3: karst-modified faults and collapse zones, SFA-4: large fluvial channels and karst-related tributaries and SFA-5: massive undifferentiated karst. Karstification shows a strong link to the underlying structural framework, with intense karstification and partial collapse associated with transtensional/transpressional fault systems, and the common alignment of karst-related features along individual fault segments. Karstification is particularly focused across the top of the Campanian Hartha Formation, where it is manifested by small-scale dolines, sinkholes, and polygonal channels. Below, the Campanian to Santonian Mutriba Formation displays a complex array of large-scale dissolution pipes and coalesced pipes, which, together with karst-modified faults and collapse zones, penetrate several hundred meters into the underlying stratigraphy. Above the Hartha Formation, the top of the Maastrichtian Tayarat Formation is dissected by fluvial channels which drained the relative upland of the Dhabi Plateau situated in the south of the study area. Cross-sections showing local thickening of early Cenozoic Rus Formation stratigraphy suggest differential subsidence and superstratal sag linked to Paleocene collapse of the underlying karstified Cretaceous fault systems. Evidence for surface processes such as fluvial incisions suggest emergence and a dominance of epigene karstification in the latest Cretaceous (Hartha and Tayarat Formations). This suggests relative sea-level fall and emergence, probably linked to foreland deformation adjacent to the Zagros margin. A prominent structural control on karst distribution, together with seismically resolvable pipes that transcend entire carbonate formations for 100's of meters, also suggests that surface terrains were overprinted and enhanced in a burial environment. This was probably by hypogenic fluid, driven by large-scale basin circulation related to Late Cretaceous/early Cenozoic foreland defo