Javier Ramajo

Análisis de facies de la Capa de Oolitos ferruginosos de Arroyofrío en la Sierra de Arcos (Jurásico, Cordillera Ibérica septentrional)

In this work we have studied the Arroyofrio Bed. This is a classic and largely studied ironstone unit in the Iberian Range. The age of this bed ranges from the Lower Callovian to Middle Oxfordian. This is a complex lithologic unit formed by irregular sedimentary events and several discontinuities associated with stratigraphic gaps of variable extent. In this work five facies containing ferruginous ooids are described and a preliminary study of the carbonate cements and Fe oolite facies is presented. This ironstone bed was formed near to an emergent high (Ejulve high). The oolites formed in a shallow marine subtidal environment. The facies and cement analysis shows that there were no long episodes of subaereal exposure at the Callovian-Oxfordian boundary. These data also demonstrate that these sediments were not deposited in deep marine conditions. The most probable hypothesis is that Fe ooids were formed in shallow subtidal and perhaps intertidal conditions and that they were eventually transported into more distal and relatively deep basinal areas.

Callovian and the Callovian - Oxfordian transition sedimentary record in NE Iberian Chain: Taphonomic analysis and palaeogeography

A comparative study is made on Callovian to middle Oxfordian sequences along the Northeastern Iberian Chain (E. Spain). In the NW areas, from Veruela-Ricla to Tosos (SW-S of Zaragoza), Callovian deposits are represented by expanded carbonate sequences (mudstone and marls with a variable content in clastics) ranging from early Bullatus to Athleta Biozone. Farther East in the near area of Moneva-Arino (Sierra de Arcos) and in the area of Calanda (SE of Zaragoza), this stratigraphic interval is represented by a strongly condensed, 2-4 m thick, highly incomplete sequence. Bullatus to early Anceps biozones are partly represented under bioclastic or oolitic packstone facies. The Callovian-Oxfordian transition interval deposits are represented by a decimeter-thick ironooid fossiliferous limestone condensed sequence (low values of sedimentation rate) formed by expanded sediments (high values of instant rate of sediment accumulation). Ammonite recorded associations frequently show traces of reelaboration and clear evidence of taphonomic condensation. The palaeogeographic evolution of the platform is reconstructed on the basis of extensive sedimentologic studies and on the analysis of taphonomic gradients shown by ammonite associations. Such taphonomic gradients clearly show a shallowing trend of the platform during the Callovian, which would take place earlier in the SE areas (Sierra de Arcos-Calanda) from Gracilis Biozone onwards, and later, from Coronatum Biozone onwards, in the NW areas (Veruela-Ricla to Tosos), the SE area acting as a shallow to temporarily emerged palaeogeographic threshold. The shallowing process would lead to the widespread emersion of the platform from latest Callovian (Lamberti Biozone) to earliest Oxfordian (Mariae and Cordatum biozone, p.p.)

Anisotropy of magnetic susceptibility of the Pyrenean granites

ABSTRACT In this paper, we report on a compilation of more than 2200 sites (more than 10,000 individual measurements) where anisotropy of magnetic susceptibility (AMS) was studied in granites from the Variscan Pyrenees. The standardization and homogenization of this information has allowed us to produce three Main Maps that synthesize all the information related with the AMS of the Pyrenean granites. We also describe the problems found during the construction of the database (variable geo-positioning, different published information, etc.). The information derived from 21 granite bodies, the database, and the synthesis maps (magnetic susceptibility, Km, and the orientation of the magnetic foliation, plane perpendicular to k3, and of the magnetic lineation, k1) allow us to see for the first time a complete image of this important kinematic and petrographic indicator.

THE STRATIGRAPHY OF THE UPPER BATHONIAN TO MIDDLE OXFORDIAN SUCESSION OF THE ARAGONESE BRANCH OF THE CORDILLERA IBÉRICA (SPAIN) AND ITS EUROPEAN CONTEXT

The Upper Bathonian-Middle Oxfordian succession of the Aragonese branch of the Cordillera Iberica is one of the most completely developed in Europe and includes localities of international importance for Jurassic bio- and chronostratigraphy. Of particular importance are a potential stratotype for the Upper Bathonian of North West Europe and reference sections for a number of Submediterranean Province Middle Oxfordian biostratigraphic units. The intervening Callovian sequence, albeit locally strongly condensed, also includes faunas of key stratigraphical importance. The sequence of stratigraphically important ammonite faunas for this interval is here reviewed and placed in its European context.