Boletín de la RSEHN. Sección Geológica

En este trabajo se realiza un estudio preliminar de la paleoflora y vegetación del sector Can Argilera del afloramiento plioceno de Camp dels Ninots, localizado en Girona (Cataluña, España). Sus materiales sedimentarios se han atribuido al Piacenziense, periodo en el cual comienza la instauración del clima mediterráneo en la Península Ibérica. Los sedimentos donde se han hallado los fósiles estudiados se depositaron en un maar, es decir, un volcán extinto cuyo cráter se inundó formando un lago. Se han estudiado 28 muestras que contienen 31 impresiones foliares de angiospermas, a partir de las cuales se han identificado siete taxones de dicotiledóneas y uno de monocotiledónea. La paleoflora de Can Argilera fue de tipo subtropical y estaba integrada por taxones arctoterciarios y paleotropicales en un contexto climático cálido y húmedo. En esta zona, la vegetación estuvo caracterizada por un bosque ripario y una laurisilva.

A study of the paleoflora and vegetation from Can Argilera sector of Camp dels Ninots Pliocene paleontological site (Girona, Spain) (fig. 1) has been carried out. Sedimentary materials dated from the Piacenzian. At this time, the Mediterranean climate established in the Iberian Peninsula. Camp dels Ninots is located on an extinct volcan filled with water and sediments, called maar. We have studied 28 samples which were collected in sandstones. They contain 31 foliar impressions of angiosperms. Eight taxa were identified: Laurophyllum sp., Daphnogene polymorpha, “Juglans” acuminata, Quercus drymeja, Alnus gaudinii, Populus populina, Caesalpinioideae gen. et sp. indet. and Poanae gen. et sp. indet. The most abundant taxon was Laurophyllum sp. This fact is possibly due as much a taphonomical overrepresentation because of its coriaceus leaves, as a botanical dominance around to the lake. From a taphonomical point of view, all identified taxa are parautochthonous, being ademic from a palaeobiological point of view except for the Poanae gen. et sp. indet. which was demic.

From a Palaeophytogeographical point of view, Laurophyllum sp., Daphnogene polymorpha and the Caesalpinioidea had a Palaeotropical origin, whereas “Juglans” acuminata, Alnus gaudinii and Populus populina have to be related to the Arctotertiary Geoflora. The flora of Can Argilera sector was integrated by a mixture of Arctoterciary and Palaeotropical taxa which lived in warm and wet environment. The vegetation of the zone could have been integrated by (1) Aquatic plants from the lake edge, (2) Broadleaved riparian forest with Alnus gaudinii, Populus populina and maybe Laurophyllum sp., and (3) Laurel forest with Laurophyllum sp., Daphnogene polymorpha and Quercus drymeja. At the end of the Pliocene the laurel forests became extinct in Iberian Peninsula. The forests of Camp dels Ninots were one of the last representations of these formations in Southwestern Europe. It is possible that the recent species Laurus nobilis and Quercus ilex subsp. ilex could be related to these old forests.

The leaf assemblages of Can Argilera sector were less taxonomical diverse than other Pliocene catalane palaeofloras. The most similar Iberian palaeofloras occurred in El Papiol, Siurana, Tortosa, Bajo Llobregat and Llano de Barcelona. In Italy and France, the Toscana and the Rhône Valley floras also show similarities although they always have higher diversity of taxa than the Can Argilera sector.