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The Eocene carbonate platforms of the westernmost Tethys: a review
According to the prevailing view in literature, two Eocene carbonate platform belts developed on northern and southern margins of the Tethys Ocean. However, Eocene platforms in the Malaguide −Ghomaride Units (Betic-Rifian Arc; Spain and Morocco, respectively) in intermediate position to the classic platform belts have been proposed in recent literature. A number of representative Ypresian to Priabonian stratigraphic sections have been revisited and empowered by new data collected for the scope. Ten lithobiofacies (consisting of limestones rich in Larger Benthic Foraminifera (LBF), algae, and corals) and ten microfacies (based on fossil assemblage and their relative abundance, texture, and fabric) were proposed for this intermediate platform belt. The paleoenvironmental reconstruction indicate inner to outer ramps (locally also the upper slope) arranged in two sedimentary sequences rich in LBF and corals. A great development of carbonate seagrass factories in most of the areas in which inner ramps developed has been identified. These factories correspond to a warm-temperate system with warm-water conditions mainly in low latitude settings. Trophic resources proposed in these works suggest oligo- to mesotrophic conditions in inner to mid ramp settings, which only evolve to eutrophic conditions in outer ramp and upper bathyal settings. A comparison of the three belts of carbonate platforms at the western Tethys scale has been performed, providing several important constraints in terms of the recorded time period according to the literature, tectonics, transgressive−regressive trendings, relative abundance of fossils, and paleoenvironmental conditions.
Environmental microfacies distribution for the Eocene marine Malaguide−Ghomaride Domains (modified from Maaté et al. 2000; Martín-Martín et al. 2020, 2021, 2023c; Tosquella et al. 2022). Ramp subdivision is based on Burchette and Wright (1992), while photic zones are modified from Pomar (2001); the new considered ‘mesophotic zone’ (zonation by Hottinger 1997) lies between the lower limit of occurrence of marine vegetation and the last occurrence of Larger Benthic Foraminifera, approximately coinciding with the storm wave base (swb). Key: Mf1, inner ramp lagoon, upper subtidal environment; Mf2, shoal, upper subtidal environment; Mf3, inner ramp seagrass, euphotic upper subtidal environment; Mf4, inner ramp coral-foralgal and acervulinid mounds, euphotic environment; Mf5, transgressive lag deposits in the transition between inner-to-mid ramp, euphotic to mesophotic environment; Mf6, mid ramp foralgal packstone–rudstone, mesophotic ma.rl environment; Mf7, proximal mid ramp LBF accumulations (nummulitids) in a mesophotic environment; Mf8, distal mid ramp LBF accumulations (orthophragminids) in a mesophotic to oligophotic environment; Mf9, outer ramp, oligophotic environment; Mf10, aphotic slope environment.
The Eocene platforms of the westernmost Tethys show a lacunose geological record registered from upper Ypresian (Cuisian) to Bartonian. It shows an important gap at the upper Ypresian (Cuisian)−Lutetian boundary. LBF remained the primary framework builders elsewhere until the Bartonian age, with zooxanthelle−coral build-ups playing a more significant role in the inner ramps than previously assumed.
Cite as: Martín-Martín, M., Tosquella, J., Guerrera, F., Maaté, A., and Martín-Algarra, A. (2024). The Eocene carbonate platforms of the westernmost Tethys: a review. International Geology Review, 1-33. https://doi.org/10.1080/00206814.2024.2397804
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