Late Ordovician conodonts from the Malaguide Complex, Betic Cordillera
|Category||Paleontology and Stratigraphy|
|Location||International Geological Congress,oslo 2008|
|Author||Martیn-Algarra, Agustیn۱; Rodrیguez-Caٌero, Rosario۱; Sarmiento, Graciela Noemی۲; Navas-Parejo, Pilar۱|
|Holding Date||08 October 2008|
Up to now, only Llandovery to Bashkirian deposits had been dated by fossils in the Malaguide Complex of the Betic Cordillera, Spain. The first malaguide Ordovician conodont association is here presented. It is also the first report of Ordovician conodonts in the Paleozoic of the Western Mediterranean Alpine Belts.
The association comes from the youngest Ordovician horizon dated by conodonts up to now discovered in the Iberian Peninsula. It was found at Ardales, Malaga, within a block of recrystallized bioclastic limestone included in siliceous-ferruginous-calcareous claystones. The conodont fauna has low diversity, with a reduced number of genera: Walliserodus, Scabbardella, Amorphognathus, Hamarodus and Protopanderodus?. Nonetheless, abundance is high (75 elements per kg). In general, specimens have quite small size but are very well preserved. Walliserodus (W. amplissimus) represents >50% of total classified specimens, whereas Scabbardella (S. altipes) is about 30%, and Amorphognathus (A. ordovicicus) aproximately 8%. The association is mainly formed by coniform elements and belongs to the Amorphognathus ordovicicus Zone of the Upper Ordovician.
It is totally different from other Spanish, European and North-African Upper Ordovician associations, but shows some similarity with those of the Hirnantian limestone member of the Uggwa Formation, Carnic Alps. Both associations have in common the small size of the conodonts, the increase in percentages of Walliserodus and, especially, the absence of Sagittodontina and Istorinus, which became extinct at that time in the Iberian Peninsula, due to the Hirnantian glaciation.
The available data are too scarce to satisfactorily explain the peculiarities of the malaguide conodont fauna, but a preliminary reasonable hypothesis suggests that it could be derived from lower paleolatitudes than those of other Spanish regions. Paleogeographic reconstructions locate most of the European terranes not far from the South Pole. The Carnic Alps, however, were located at less high paleolatitude, as it would be inferred for the Malaguide Complex in Late Ordovician time.
These new data reinforce classical hypothesis supporting close paleogeographical relationships between the Internal Domains of the Betic Cordillera and those of the Alps. It also confirms that, before the Alpine Orogeny, the Internal Domains of the Betic Cordillera were located far toward the east of their present location.