Lower Jurassic benthic foraminiferal assemblages from shallow-marine platform carbonates of Mallorca (Spain): stratigraphic implications

Abstract

The stratigraphic distribution of larger benthic foraminifera and other microfossils recognizable in thin sections has been investigated in three stratigraphic profiles (Son Maina, S'Heretat and Cuevas de Artà) along the Lower Jurassic shallow-water carbonate platform succession (Es Barraca Member) of the Llevant Mountains in the Mallorca Island. Here, the microfossil assemblage contains abundant benthic foraminifera and calcareous algae, including the microproblematic Thaumatoporella parvovesiculifera (Raineri) and the typical Liassic species Palaeodasycladus mediterraneus (Pia), which has allowed a better age constraint of the succession. Four consecutive biozones (scheme of Septfontaine 1984) have been recognized based on the stratigraphic distribution of imperforate foraminifera, which are documented by the first time in the Balearic Basin: Biozone A (interval Zone) is characterized by the occurrence of small Siphovalvulina sp. and Mesoendothyra sp. and some Lituosepta ancestors. Biozone B (lineage Zone), whose base is marked by the first occurrence of L. recoarensis Cati and the top by the first appearance of primitive forms of Orbitopsella. Biozone B/C1 transition, characterized by the presence of very primitive forms of Orbitopsella. Finally, Biozone C1 (lineage Zone) marked by the first occurrence of Orbitopsella aff. primaeva (Henson) but still with L. recoarensis. This distribution of foraminiferal zones is consistent with a Sinemurian age for the Es Barraca Member, with its top very unlikely penetrating into the Pliensbachian. The proposed biostratigraphic scheme is comparable with those established for other western Tethyan margins such the High Atlas of Morocco and the Betic Cordillera in southern Spain. The reconstruction of the depositional transect across these profiles shows the progressive lost of the upper biozones towards the northeast, evidencing the existence of significant hiatuses in some sections of the Llevant Mountains domain, and allowing to infer an intra-Pliensbachian early stage of platform fragmentation and erosion, or alternatively non-deposition, probably coeval with progradation of deltaic siliciclastics to the northwest part of the Mallorca island. The new biostratigraphic data presented here highlights the need to review and clarify the current stratigraphic scheme established for the Lower Jurassic of Mallorca.

Orbital cycles, differential subsidence and internal factors controlling the high-frequency sequence architecture in a Sinemurian shallow carbonate platform (Mallorca island, Spain)

“…5). This boundary is close to the boundary between the foraminifera biozones A and B recognized by Sevillano et al (2020) in S´Heretat and Son Maina sections (Fig. 2).…”

“…The foraminiferal assemblage in the Stage-1 of the Es Barraca Member shows the presence of Siphovalvulina sp., Meandrovoluta asiagoensis Fugagnoli and Rettori, Glomospira sp., Mesoendothyra sp., Duotaxis sp. and some textulariids in their lower part (Sevillano et al, 2019(Sevillano et al, , 2020, which is compatible with an early Sinemurian age (Velić, 2007). The upper part of this Stage-1 shows in addition Haurania sp., Journal Pre-proof J o u r n a l P r e -p r o o f 8 Everticyclammina praevirguliana Fugagnoli and Lituosepta recoarensis Cati (Sevillano et al, 2019(Sevillano et al, , 2020) that indicates a late Sinemurian age (Septfontaine, 1984;Boudagher-Fadel and Bosence, 2007;Velić, 2007;Fugagnoli and Bassi, 2015).…”

“…Therefore, the correlation of large-and medium-scale sequences proposed here has been based on the best fit regarding facies trends recorded in the sequences, and considering the short distances (few km) between three of the four logs studied. The available recent Journal Pre-proof J o u r n a l P r e -p r o o f biostratigraphic data from benthic foraminifera of Sevillano et al (2020) have also been taken into account for the correlation between sections, being aware of the existence of some uncertainty in the position of the limits between biozones A and B (Fig. 2), introduced by sampling bias and/or incompleteness of the fossil record.…”

“…The other two sections are incomplete. In S'Heretat section (70 m thick) the lower part of the succession is covered, whereas in Cuevas de Artà section (110 m thick) the succession is truncated on its top (Sevillano et al, 2019(Sevillano et al, , 2020.…”

“…The upper part of this Stage-1 shows in addition Haurania sp., Journal Pre-proof J o u r n a l P r e -p r o o f 8 Everticyclammina praevirguliana Fugagnoli and Lituosepta recoarensis Cati (Sevillano et al, 2019(Sevillano et al, , 2020) that indicates a late Sinemurian age (Septfontaine, 1984;Boudagher-Fadel and Bosence, 2007;Velić, 2007;Fugagnoli and Bassi, 2015). A recent, detailed biostratigraphic analysis (Sevillano et al, 2020) has attributed the studied interval to the biozone A (Siphovalvulina sp. and Mesoendothyra sp.…”