The Jurassic – Cretaceous transition in the West Cameros Basin (Tera Group, Burgos, Spain): Sedimentological and palynostratigraphical insights

The Jurassic–Cretaceous boundary transition is widely distributed within the West Cameros Basin. This horizon constituted by Tera Group, consisting of two depositional sequences (DS1 and DS2) comprising four geological formations spanning Tithonian to Berriasian. Here, a combined sedimentological palynostratigraphic study was made covering Group. results for DS 1 differentiate three facies associations (FA 1-1, 1-2 1-3) corresponding floodplains braided channels distributive fluvial system shifting shallow lacustrine in semi-arid climate. For 2, FA were also differentiated 2-1, 2-2, 2-3), tidal-influenced meandering distal delta-plain that shifts facies. palynological only productive samples from Jaramillo Formation. record shows an assemblage dominated spores including Concavissimisporites, Leptolepidites Taurocusporites, as well Classopollis pollen. According stratigraphic ranges some selected taxa, suggested chronostratigraphic assignment lower Berriasian Fm. A comparison microfloras Tithonian–Berriasian recorded Iberian Peninsula carried out. following observations can be concluded: 1) change plant communities, already observed since Late Jurassic onwards, became more pronounced between late Berriasian; 2) noteworthy occurrence biostratigraphically important specifically interval.