Geology of the Eastern Prebetic Zone at the Jumilla region (SE Iberia)

This article presents a geological map and cross-sections at 1:50,000 scale covering an area of 609 km² of the Eastern Prebetic Zone (SE Iberia). The structure of the studied area is characterized by an NW-directed fold-and-thrust belt and inactive salt diapirs that are parallel to the ENE- to NE-regional trend of the eastern Betic Cordillera. This regional trend is locally disrupted by the NW-trending Matamoros Basin, which is flanked by the active Jumilla and La Rosa diapirs. The geological map, the cross-sections and the outcrop observations support the hypothesis that the major Mesozoic rifting phase affecting the Eastern Prebetic Zone occurred during the Upper Jurassic to Santonian times coeval to the development of extensional basins in the Western Tethyan area. The proximal part of this passive margin was subsequently incorporated into the external part of the Betic thin-skinned fold-and-thrust belt. The Upper Cretaceous to Cenozoic tectonic evolution of the study area encompassed the following stages: a Campanian to Aquitanian NW-directed contraction; a Burdigalian to upper Miocene extensional reactivation of the main subsalt faults; and a Serravallian NW-directed contractional reactivation. In this scenario, the combined effect of the previous contractional reactivation of pre-existing salt structures together with the Miocene subsalt extension triggered passive salt extrusion of the La Rosa and Jumilla diapirs.

本文呈现了一套比例尺为1:5万的地质图与剖面图，覆盖伊比利亚半岛东南部东普雷贝蒂克带（Eastern Prebetic Zone）609平方千米的区域。研究区的构造以指向北西的褶皱冲断带，以及平行于贝蒂科山脉（Betic Cordillera）东部ENE至NE向区域走向的休眠盐底辟为特征。该区域走向局部被北西向的马塔莫罗斯盆地（Matamoros Basin）所打断，盆地两侧发育活动的胡米利亚（Jumilla）与拉罗萨（La Rosa）盐底辟。这套地质图、剖面图以及露头观测结果，佐证了如下假说：影响东普雷贝蒂克带的主要中生代裂谷作用发生于晚侏罗世至桑托期，与西特提斯域（Western Tethyan area）伸展盆地的发育同期。该被动大陆边缘的近源部分后续被并入贝蒂科薄皮褶皱冲断带的外部区域。研究区白垩纪至上新生代的构造演化包含以下阶段：坎潘期至阿基坦期的北西向挤压作用；布尔迪加期至晚中新世盐下主断层的伸展复活；以及塞拉瓦尔期的北西向挤压复活。在此背景下，先存盐构造的挤压复活与中新世盐下伸展的共同作用，触发了拉罗萨与胡米利亚盐底辟的被动盐体挤出。