Abstract
The assemblages of Early Jurassic brachiopods (Pliensbachian - Toarcian) from Sierra Espuña (Murcia Province, SE Spain) are described. This is the only area in the Internal Zones of the Betic Cordillera, corresponding to the margins of the Alborán Terrane, where Jurassic brachiopods are known to occur. In the tectonic Unit of Morrón de Totana (more southward located) assemblage MT1 of Late Pliensbachian age has been characterized. This assemblage has been subdivided into three successive sub-assemblages: MT1a (Algovianum Zone), MT1b (Emaciatum Zone, Solare Subzone) and MT1c (Emaciatum Zone, Elisa Subzone). Northward, in the Perona tectonic Unit two distinct assemblages, P1 (Latest Sinemurian - Early Pliensbachian) and P2 (Early Toarcian, Serpentinum Zone) have been recognized. Differences between the assemblages from the two tectonic units are evident after the paleobiogeographical analysis. In the Morrón de Totana Unit, taxa with Mediterranean affinities occur. MT1 assemblage is very similar to assemblages previously known in the Eastern Subbetic as well as in other areas of the Mediterranean Province. In the Perona Unit the Mediterranean affinity of the assemblages is not so evident. P1 Assemblage consists of widely distributed taxa, lacking in the most characteristic elements of the Mediterranean Province which, however, are present in neighbouring Betic areas. P2 Assemblage belongs to the Spanish Province that develops in Western Tethys after the Early Toarcian Mass Extinction Event. The occurrence in this assemblage of Prionorhynchia aff. msougari Rousselle, until now only found in North Africa, indicates a closer connection of the Perona Unit with the African paleomargin of the Tethys than with the South Iberian paleomargin. The paleobiogeographical data suggest a more southern and marginal (close to epicontinental areas) position of the Perona Unit than the Morrón de Totana Unit.
Highlights
The Early-Middle Jurassic transition paleogeography of the westernmost Tethys area was characterized by two major plates separated by the Central Atlantic Ocean in a Red Sea-type stage
The Iberian Subplate was located in the southern margin of the northern plate, structuring the South Iberian margin (MartínAlgarra and Vera, 2004), which originated the External Betic Zone during the Alpine Orogenesis, and the northwestern margin of the African plate that evolved into the External Rif Zone
The paleolatitude of the South Iberian paleomargin was about 30o N, whereas the AlKaPeCa Microplate was probably situated at a similar paleolatitude, but more eastward (Ziegler, 1990; Bassoullet et al, 1993; Vera, 2001; Stampfli and Borel, 2004)
Summary
The Early-Middle Jurassic transition paleogeography of the westernmost Tethys area was characterized by two major plates separated by the Central Atlantic Ocean in a Red Sea-type stage. The northern plate one was the Laurasian and the southern one was the African Plate. The Iberian Subplate was located in the southern margin of the northern plate, structuring the South Iberian margin (MartínAlgarra and Vera, 2004), which originated the External Betic Zone during the Alpine Orogenesis, and the northwestern margin of the African plate that evolved into the External Rif Zone. In the Tethys Ocean, the AlKaPeCa Microplate (Alboran, Kabilyan, Peloritanian and Calabria; Bouillin et al, 1986), known as Mesomediterranean plate (Martín-Algarra et al, 1992; Guerrera et al, 1993), comprises the internal zones of the Betic-Rif, Tellian, Kabylian, Calabria-Peloritanian and Southern Apennine Chains. The Tertiary tectogenesis divided this microplate in different terranes separated by the extension of the Western Mediterranean Sea: Alboran, Kabilyan, Peloritanian, and Calabria
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