Late Chattian Platform Carbonates With Benthic Foraminifera and Coralline Algae From the Se Iberian Plate

Abstract

The carbonate system studied represents an under-investigated sedimentary record formed in the western end of the Tethys during the Chattian relatively warm climate regime. These platform carbonates are examined with respect to rock fabrics, biostratigraphy, biostratinomy, paleoecology, and sequence stratigraphy. Dominant carbonate producers include scleractinian corals and echinoids, but the most prolific were symbiont-bearing benthic foraminifera and coralline algae. The presence of Miogypsinoides complanatus and Miogypsinoides formosensis indicates a late Chattian age (Shallow Benthic Zone 23). The depositional profile is consistent with a homoclinal ramp. The absence of a barrier margin and thus, of a lagoon, facilitated the transport and reworking of biogenic components throughout the platform. As a result, facies are rather homogeneous corresponding to a rudstone mainly formed by benthic foraminifera and coralline algae, which passes basinwards to deeper ramp to hemipelagic deposits rich in echinoids and planktonic foraminifera. Within this dominant facies, only subtle and gradual lateral variations on the relative abundance or absence of certain skeletal components or species are recognized, comprising two end members. A proximal biofacies of benthic foraminifera and coralline algae including corals in growth position, fragments of green algae, and seagrass dwellers where Eulepidina, Nummulites, and Operculina are absent, and a distal biofacies where corals, green algae, and seagrass dwellers are not present, but Eulepidina, Nummulites and Operculina are common. Carbonate deposition was controlled by long-term relative sea-level fluctuations including a Rupelian?-late Chattian transgression, a late Chattian regression, which ended in subaerial exposure of proximal ramp carbonates, and a latest Chattian to early Miocene transgression. The Chattian carbonate platform was finally drowned around the Oligocene/Miocene transition.

Coralline Algae in a Changing Mediterranean Sea: How Can We Predict Their Future, if We Do Not Know Their Present?

“…In the majority of localities, Oligocene corallines occur in coral reef deposits or in laterally associated sediments as rhodoliths, coralline debris, or as crusts directly growing on the soft sea floor (Fravega et al, 1987;Brandano, 2017). Occasionally, rhodoliths and algal debris have also contributed as important carbonate producers in late Oligocene homoclinal carbonate ramps in the western Tethys (Bover-Arnal et al, 2017). They also occur in deep-water, re-deposited carbonates (Rasser and Nebelsick, 2003).…”

Sedimentary environment and depositional sequences of the Qom Basin (north-eastern margin of the Tethyan seaway)

“…The taphonomic signatures (fragmentation, abrasion, encrustation, and bioerosion) were evaluated on the basis of Allison and Bottjer (2011), Silvestri et al (2011), Bover-Arnal et al (2017. The qualitative classification presented by Beavington-Penney (2004), was used to evaluate the damage to large benthic foraminifera tests.…”

“…Harzhauser and Piller (2007) and Reuter et al (2009) showed that the Qom sedimentary basin is located on the northern margin of the Neotethys basin. During the Oligocene, carbonate platforms dominated by coralline algae and benthic foraminifera developed along the margins of the Tethys Sea as well as in the Tethyan Seaway in the Iranian Plate and the Atlantic and Indo-Pacific realms (Bover-Arnal et al, 2017). Microfacies analysis and iD iD iD palaeoenvironmental interpretation of the Qom Formation show that Qom Formation was deposited in a variable depositional system (Mohammadi et al, 2011).…”

Reconstruction of the depositional sedimentary environment of Oligocene deposits (Qom Formation) in the Qom Basin (northern Tethyan seaway), Iran

“…5). Qualitative estimates of pre-burial taphonomic features were performed based on the research of Silvestri et al (2011) and Bover-Arnal et al (2017). Beavington-Penney (2004) introduced a qualitative evaluation of test degradation among benthic foraminifera.…”

“…Silvestri et al (2011) believed that coralline red algae and corals were fragmented and abraded by transport and reworking. High rates of encrustation can be observed in an environment with high energy and a low sedimentation rate (Silvestri et al, 2011;Ćosović et al, 2012;Bover-Arnal et al, 2017). The tests of large benthic foraminifera were damaged by wave action, which transported them to distant location (Beavington-Penny, 2004).…”