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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
New biostratigraphic data on the Paleocene-Eocene from the Prebetic
A biostratigraphic study of the Paleocene-Eocene of the stratigraphically continuous with the northern foreland (Iberian Meseta), Prebetic has been studied by using planktonic foraminifera, calcareous nannoplankton, and larger benthic foraminifera. Twelve sections have been studied along the chain: four sections in the Alicante Sector, four in the Murcia Sector, two in the Granada Sector, and two sections in the Jaén Sector.
The Paleocene-Eocene Prebetic succession can be divided into three stratigraphic formations related by lateral and diachronic changes of facies: limestones and calcarenites (rich in larger benthic foraminifera) in middle stratigraphic position, and two marly-clayey formations in lower and upper positions, respectively. The middle unit represents an internal marine platform, while the two marly-clayey represent the external platform (and the upper slope in a few cases). As a whole, above the unconformity, representing the missing interval which includes the Cretaceous-Paleocene boundary.
Cite as: Martín-Martín, M., Miclăuș, C., Serrano, F., Tosquella, J., Samsó, J.M., Tent-Manclús, J.E., and Martín-Pérez, J.A. (2023): New biostratigraphic data on the Paleocene-Eocene succession from the Prebetic domain (Betic Cordillera: South Spain).Abstract Book, Fourteenth Romanian Symposium on Palaeontology, Bucharest, 14-15 September 2023 / Zoltán Csiki-Sava, Alina Floroiu, Maria-Raluca Văcărescu, Iuliana Lazăr – Bucureşti : Editura Universităţii din Bucureşti -Bucharest University Press, 2023, 79-80 p.
The Eocene carbonate platforms of the Ghomaride Domain (Internal Rif Zone, N Morocco): a segment of the westernmost Tethys
The Eocene platform deposits in the Moroccan Ghomarides have been studied. These marine carbonate platforms were located in the westernmost Tethys approximately 30°N and 0°–10°W during the Cuisian to Bartonian. The study includes observations from fossiliferous assemblages (such as larger benthic foraminifera and colonial corals), their palaeoenvironment aswell as rock texture and fabric. Eight microfacieswere identified that represent different ramp environments in a ‘distally-steepened carbonate ramp’ type of platform. The studied deposits are organised into a transgressive succession composed of three sedimentary cycles: lower Cuisian, middle Cuisian and middle Lutetian to Bartonian. In the lower cycle, photic inner to mid ramp environments in mesotrophic conditions were prevalent. In the second cycle, photic inner ramp (sea-grass) to mid ramp environments inmesotrophic to oligotrophic conditions were observed. The upper cycle, which is more extensive and variable, represents mesophotic mid ramp to aphotic slope environments and changes gradually from oligotrophic to eutrophic conditions. During the Eocene, larger benthic foraminifera were dominant overtaking the zooxanthellate corals in the Tethys regions. Nevertheless, our study and the performed comparison with other Tethyan sectors have revealed that in some areas both coexisted in similar proportions. In some western Tethys regions close to the Atlantic Ocean, coinciding with areas influenced by upwelling currents, larger benthic foraminifera and coral build-ups were replaced by oyster reefs. The Ghomaride Domain represents an intermediate case between fossil assemblages of the northern Tethyan margin and eastern sector of the southern margin of the Tethys, with a dominance of larger benthic foraminifera but with a certain presence of corals as well. A good correlation exists between Eocene warm intervals and carbonate platform deposits in these domains. Contrarily, during cooling ones shallowing and gaps in the sedimentation are registered.
Two anomalies have been detected in the Ghomaride Domain during Ypresian and Bartonian times indicating particular climatic conditions or local tectonic interferences.
Cite as: Martín-Martín, M., Tosquella, J., Guerrera, F., Maaté, A., Hlila, R., Maaté, S., Tramontana, M., Le Breton, E., 2023. The Eocene carbonate platforms of the Ghomaride Domain (Internal Rif Zone, N Morocco): a segment of the westernmost Tethys. Sediment. Geol. 452, 106423. https://doi.org/10.1016/j.sedgeo.2023.106423
Eocene carbonate platform of the Malaguides of the westermost Tethys
The Eocene Peñicas (Almería) and Harania (Málaga) stratigraphic sections from the Malaguide Complex (Betic Cordillera, South Spain) belonging to the Mesomediterranean Microplate from the westernmost Tethys (about 35◦N) have been studied. The Eocene sections cover the Cuisian to middle Lutetian deposits, which show several lithofacies representing shallow marine platform realms. Based on the fossiliferous assemblage, texture and fabrics, eight microfacies related to inner to outer ramp settings were defined. In the inner ramp of the Harania section abundant colonial corals have been recognized. The Eocene deposits are arranged into a transgressive succession composed by three minor transgressive-regressive sedimentary cycles. The Eocene fossiliferous assemblage shows a mixture of photozoan (Larger Bentic Foraminifera, green and red calcareous algae and corals) and heterotrophic (mollusks, echinoids, bryozoans, small benthic and planktic foraminifers) elements, suggesting euphotic to mesophotic conditions in oligo-mesotrophic marine warm-waters at low-middle latitudes. This assemblage indicates a transition from photozoan to heterozoan carbonates and in particular a shift towards outer marine ramp settings.
During the Early Eocene, the widespread distribution of Larger Benthic Foraminifera leads in the Tethyan domains to disappearance or extreme reduction of coral constructions. Nevertheless, abundant corals associated to inner ramp realms have been observed in the Harania stratigraphic section indicating that corals could continue to develop in the westernmost Tethys at the transition to the Atlantic Ocean, in contrast with respect to other Tethyan sectors. Therefore, the Ypresian-Lutetian time-span is a transitional period for the global temperature during which corals locally survived only where optimal ecologic conditions occurred, preferably in marginal contexts, as it seems to have happened in the studied area.
Middle Eocene carbonate platforms of the westernmost Tethys
A study of the paleoenvironmental evolution of the middle Eocene platforms recognized in the westernmost Tethys has been carried out in the well exposed middle Eocene succession from Sierra Espuña-Mula basin (Betic Cordillera, S Spain). Eight microfacies (Mf1 to Mf8) have been recognized, based mainly on fossil assemblages (principally larger benthic foraminifera), and rock texture and fabric.
The fossiliferous assemblage can be asigned to the ‘subtropical’ heterozoan association or to the low-latitude ‘foralgal facies’ , which are dominated by non-framework building, light-dependent biota such as perforate larger benthic foraminifera, coralline algae, and sometimes green algae and solitary corals. Larger benthic foraminifer assemblages, corresponding from euphotic to oligophotic conditions and the large surface showed, suggest a progressive marine ramp under essentially oligotrophic conditions. Eventually, supply of detrital sediments from the continent and/or upwelling currents increasse the nutrients of marine waters. Comparision with other Tethyan sectors allows stating that coral-reef buildups (z-corals) were widespread on shallow platforms of the central and eastern Tethys Ocean, but that these were neither of great dimensions nor dominant because of the much more dominant presence of larger benthic foraminifera. Moreover, these coral constructions were completely absents in the westernmost Tethys. The dominance of larger benthic foraminifera and the absence of z-corals in the westernmost Tethys is explained by particular paleogeographic features due to the occurrence of a narrow and deep oceanic branch (i.e., the Maghrebian Flysch Basin) connecting the Tethys with the Atlantic Ocean.
The various issues regarding the morphological characters and evolution of larger benthic foraminifera in the study area, such as sizes of tests, specific diversity and/or intraspecific variability, number of appearances and last occurrences during the middle Eocene are analyzed and compared with those appearing in other Tethyan sectors. In addition, the early to late Bartonian boundary is recognized in the study area as critical for the biological change as in other shallow-marine environments along the Tethys margins.
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