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

侏罗纪-白垩纪边界过渡在西卡梅罗斯盆地内广泛分布。该层位由 Tera 组构成，由两个沉积序列（DS1 和 DS2）组成，包括从 Tithonian 到 Berriasian 的四个地质构造。在这里，对 Tera 群进行了沉积学和孢粉地层学联合研究。DS 1 的沉积学结果区分了三个相组合（FA 1-1、1-2 和 1-3），它​​们对应于在半干旱气候下向浅湖相转变的分布河流系统的漫滩和辫状河道。对于 DS 2，还区分了三种 FA（FA 2-1、2-2 和 2-3），对应于受潮汐影响的曲流河道和泛滥平原的远端河流到三角洲平原系统转移到浅湖相。孢粉学结果仅在 Jaramillo 组的样品中有效。孢粉记录显示以孢子为主的组合，包括Concavissimisporites、Leptolepidites和Taurocusporites，以及Classopollis花粉。根据一些选定分类群的地层范围，建议的年代地层分配为 Jaramillo Fm 的下 Berriasian。对伊比利亚半岛记录的 Tithonian-Berriasian 微生物区系进行了比较。可以得出以下观察结果： 1）自侏罗纪晚期以来已经观察到的植物群落变化在提通期-贝里亚期边界和贝里亚期晚期之间变得更加明显；2) 一些生物地层重要分类群的显着出现，特别是对于 Tithonian-Berriasian 间隔。