Lower Jurassic benthic foraminiferal assemblages from shallow-marine platform carbonates of Mallorca (Spain): stratigraphic implications Ana Sevillano, Michel Septfontaine, Idoia Rosales, Antonio Barnolas, Beatriz Bádenas, José María López-García To cite this version: Ana Sevillano, Michel Septfontaine, Idoia Rosales, Antonio Barnolas, Beatriz Bádenas, et al.. Lower Jurassic benthic foraminiferal assemblages from shallow-marine platform carbonates of Mallorca (Spain): stratigraphic implications. Journal of Iberian Geology, Springer Verlag, 2020, 46 (1), pp.77- 94. 10.1007/s41513-019-00117-9. hal-02947758 HAL Id: hal-02947758 https://hal.archives-ouvertes.fr/hal-02947758 Submitted on 24 Sep 2020 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. 1 LO W ER JURASSIC BENTHIC FORAMINIFERA L ASSEMBLAGES FROM 2 SHALLOW MARINE PLATFORM CARBONATES OF MALL ORCA ( SPAIN ): 3 STRATIGRAPHIC IM P LICATIONS 4 5 Ana Sevillano a , Michel Septfontaine b , Idoia Rosales c , Antonio Barnolas c , Beatriz 6 Bádenas d , José María López - García a 7 a Instituto Geológico y Minero de España (IGME), 07007 Palma de Mallorca, Spain 8 b University of Lausanne, CH - 1015 Lausanne, Switzerland 9 c Instituto Geológico y Minero de España (IGME), Ríos Rosas 23, 28003 Madrid, 10 Spain 11 d Departamento de Ciencias de la Tierra, Universidad de Zaragoza, 50009 12 Zaragoza, Spain 13 *Corresponding author. Tel: +34 971467020 14 E - mail address: [email protected] (A. Sevillano) 15 16 Abstract 17 The stratigraphic distribution of larger benthic foraminifera and other microfossils 18 recognizable in thin sections has been investigat ed in three stratigraphic profile s (Son 19 Maina , S’Heretat and Cuevas de Artà) along the Lower Jurassic shallow - water 20 carbonate platform succession ( Es Barraca M ember ) of the Llevant M ountains in the 21 Mall orca I sland . Here, the microfossil assemblage contains abundant benthic 22 foraminifera and calcareous algae, including the microproblematic Thaumatoporella 23 parvovesiculifera (Raineri) and the typical Liassic species Palaeodasycl adus 24 mediterrane us (Pia) , which has allow ed a better age constraint of the succession . F our 25 consecutive biozones (scheme of Septfontaine 1984 ) have been recognized based on the 26 stratigraphic distribution of imperforate foraminifera, which are documented by the first 27 time in the Balearic Basin : Bioz one A (interval Zone) is characterized by the occurrence 28 of small Siphovalvulina sp. and Mesoendothyra sp . a nd some Lituosepta ancestors . 29 Biozone B (lin eage Zone), whose base is marked by the first occurrence of L. 30 recoarensis Cati and the top by the fi r st appearance of primitive forms of Orbitopsella . 31 Biozone B/C1 transition , characterized by the presence of very primitive forms of 32 Orbitopsella . Finally, Biozone C1 (line age Zone) marked by the first occurrence of 33 Orbitopsella aff. p rimaeva (Henson) but still with L. recoarensis . This distribution of 34 foraminiferal zones is consistent with a Sinemurian age for the Es Barraca Member , 35 with its top very unlikely penetrating in to the Pliensbachian . The proposed 1 36 biostratigraphic scheme is comparabl e with those established for other western Tethyan 37 margins such the High Atlas of Morocco and the Betic Cordillera in southern Spain. 38 The reconstruction of the deposi ti onal transect across these profiles shows the 39 progressive lost of the upper biozones towards the northeast , evidencing the existence of 40 significant hiatuses in some sections of the Llevant Mountains domain , and allowing to 41 infer an intra - Pliensbachian early stage of platform fragmentation and erosion , or 42 alternatively non - deposition , probably coeval with progradation o f delta ic siliciclast ics 43 to the northwest part of the Mall orca island. The new biostratigraphic data presented 44 here highlights the need to review and clarify the current stratigraphic scheme 45 established for the Lower Jurassic of Mallorca. 46 47 Key words: Sinemurian earl iest Pliensbachian , benthic foraminifera, biozones, 48 carbonate platform, Es Barraca Member, Balearic Basin 49 1 Introduction 50 Shallow - marine carbonates of Early Jurassic age developed widely in the western 51 Tethyan margins (Fig. 1 ) . These shallow water carbonate environments experienced 52 important architectural and compositional cha nges in a context of rifting related with 53 the break - up of Pangea and associated with important circulation , environmental 54 changes a n d an eustatic sea - level rise ( e.g. Zempolich 1993 ; Ruiz - Ortiz et al. 2004; 55 Massetti et al. 2016 ; Preto et al. 2017 ; Rychlinski et a l. 2018 ; Franceschi et al. 2019 ) . 56 These changes are recorded in the lithostratigraphic and biostratigraphic record of the 57 Tethyan platforms. These events coincided also with t he faunistic turnover that occurred 58 in the Early Jurassic after the catastrophic Triassic - Jurassic (T/J) boundary m ass 59 extinction , which resulted in a gradual recovering and diversification o f the shallow - 60 water benthic communities , in which larger benthic foraminifera played a primordial 61 role . So that, t he poorly diversified benthic associations of the Hettangian evolved 62 during the early Sinemurian into a more diversified Siphovalvulina - and Textularia - 63 dominated assemblages , and finally into more com plicated lituolids during the late 64 Sinemurian – Pliensbachian , providing an important biostratigraphic tool (Fig. 2) 65 ( Septfontaine 1984, 1988 ; Bassoullet 1997 ; Fugagnolli and Loriga 1998 ; Kabal and 66 Tasli 2003 ; Mancinelli et al. 2005 ; Boudagher - Fadel and Bosence 2007 ; Velic 2007 ; 67 Gale 2014 ). 2 68 The Lower Jurassic succession of the Balearic Islands ( Fig. 3 ) is a good representative 69 of the evolution of one of these carbon ate platforms associated to all the above - 70 mentioned events ( Álvaro et al. 1989 ; Rosales et al. 2018 ; Sevillano et al. 2019 ). A 71 comprehensible study of facies analysis and platform evolution of the shallow - water 72 carbonates (Es Barraca Member) has been provided recently in Sevillano et al. (2019) . 73 The microfossil content of the Es Barraca Mb was studied in the past by Fallot (1922), 74 Colom (1966, 1970, 1980) , and Colom and Dufaure (1962 ), but not detailed 75 stratigraphic distribution of the recognized foraminifera taxa and biozones was given 76 before. This new micropaleontological study has three aims : First, to establish a 77 foraminiferal biostratigraphy of this shallow - water carbonate succession and to use the 78 distribution of biozones for improving the age resolution of the Es Barraca Member 79 (particular ly its top) and, therefore, its relationship with other Lower Jurassic 80 stratigraphic units, for a better definition of the current Lower Jurassic stratigraphic 81 scheme of the Mallorca island . Second, to follow changes, in the studied samples, of the 82 gradual evolution of the Orbitopsellids s.l. during the Lower Jurassic. Third, to use the 83 new biostratigraphic information for getting a better understanding of the 84 tec to nostratigraphic evolution of the area during the Lower Jurassic. In addition, t his 85 new study will improve the knowledge of the paleogeographical distribution of the 86 Lower Jurassic Foraminifera species in the western Tethys of the eastern Iberian 87 margin , allowing a better comparison with other Tethyan regions. 88 2 Geological setting 89 The Jurassi c sedimentary successions of Mall orca was deposited in a subsiding basin 90 ( Balearic Basin , BB) located in the southe aste rn margin of the Iberian P late , in a 91 paleogeographic position adjacent to the Ebro High , which was emerged in those t imes 92 according to recent paleogeographic reconstructions ( F ig. 1 ) ( Thierry 2000 ; Scotes e and 93 Schettino 2017 ). The sedimentary evolution of the Balearic basin during the Jurassic 94 accompanied the opening of the Central Atlantic Ocean and the tectonic evolution of the 95 western Tethyan rifting ( Dewey et al. 1973 ; Dercourt et al. 2000 ). Although the 96 Balearic archipelago has traditionally been considered as the northeastern prolongation 97 of the Betic Cordillera, new studies suggest that the geodynamic evolution of the area 98 seems to be closer to the early opening of Gulf of Valencia, where recent offshore 99 seismic surveys have brought out the existence of a thick, submerged Mesozoic rift 100 ba sin, of which, the Balearic archipelago represent the symmetrical southeastern basin 3 101 border ( Bourrouilh 2016 ; Etheve et al. 2018 ). In Mallorca, the biggest island of the 102 archipelago, the rifting evolution during the Jurassic recorded ( Á lvaro et al. 1989 ; 103 Barnolas et al. 2010 ) : ( 1) Lower Jurassic shallow - water carbonate platform successions 104 (Hettangian – Pliensbachian), ( 2) platform drowning facies during the Toarcian with 105 hardgrounds development, ( 3) hemipelagic sedimentation during the Toarcian - Aalenian, 106 and ( 4 ) typical ammonitico rosso, radiolarites, and mass - wasting