Volcanosedimentary complex encompassing the Ediacaran- Cambrian boundary interval in the Oriental Pyrenees
Abstract
The Pyrenees are part of the northeastern margin of the Ibero-
Armorican Variscan Arc. They possess one of the most complete
uppermost Ediacaran–Cambrian successions in West Gondwana
which has been classically divided into two principal lithostratigraphic
units : the Canaveilles and Jujols Groups. In the southern
flank of the Canigou massif (Puigmal Variscan tectonostratigraphic
unit), a unique Fabert volcanic level is usually described at
the top of the Cabrils Formation (uppermost Canaveilles Group)
which was recently dated around ca. 570 Ma. The overlying Tregurà
Formation (Jujols Group) is divided into a lower volcanoclastic
breccia member with limestone olistoliths and strong thickness
variations, and an upper limestone member. The Tregurà Formation
has been considered to encompass the Ediacaran-Cambrian
transition, however, until now, no geochronological data have supported
this hypothesis. The present study has been aimed to provide
an up-to-date and detailed facies analyzes of the Ediacaran-
Cambrian formations from the Pyrenees, and to test previously
published dating of above-mentioned volcanic and breccia levels
through new LA-ICPMS U–Pb dating of zircons. Therefore, the
so-called Fabert volcanic level have been sampled in the Fabert
Village and the nearby Pic de la Clape, yielding respective ages
at ca.559.5 +1.7/-1.3 Ma and ca.542.9 +5/-1.3 Ma. The Tregurà
breccia, sampled at the Pic du Finestrelles and the Pic de
la Clape, have respectively yielded maximum depositional ages
of ca.556±7Ma and ca.532.9±6.1 Ma.. These new dating argue
for a long-lasting volcanic episode with multiple pulses during the
Ediacaran-Cambrian transition. As a consequence, an updated
stratigraphic framework is proposed.