Poster Number 136
The detailed stratigraphic and chemostratigraphic analysis in the La Laja Formation allows suggesting a strong similarity with the synchronous interval recorded in the southern Appalachians known as the Conasauga Group (from Tennessee to Alabama). This, points to a comparable geotectonic and depositional setting within this unique time interval. The stratigraphic pattern indicates a progressive stabilization of the margin after the rifting stage that produced the opening of the Iapetus ocean and the final detachment of the Precordillera. During the Early to Middle Cambrian, accommodation was controlled not only by continuous thermal subsidence and eustatism but also by some tectonic component (jerky subsidence). An abrupt change in the depositional pattern is recorded during the Middle to Upper Cambrian boundary, where peritidal dolomites of the Zonda Formation abruptly overlay the La Laja Formation. This is taken to represent the broadening of the carbonate sedimentation and development of a true epeiric sea atop the passive-margin in the drifting Precordillera terrane. A stratigraphic parallelism is observed within the southern Appalachians where the Knox Group dolomites cover the cyclic Conasauga Group.