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.

本文提供了伊比利亚半岛东南部（SE Iberia）东前贝蒂克带（Eastern Prebetic Zone）609平方千米范围的1:50000比例尺地质图与剖面。研究区构造以NW向褶皱冲断带（fold-and-thrust belt）以及与贝蒂科山脉（Betic Cordillera）东部ENE至NE向区域走向平行的不活动盐底辟（salt diapirs）为特征。该区域构造走向局部被NW向的马塔莫罗斯盆地（Matamoros Basin）打断，该盆地两侧发育活动的胡米利亚（Jumilla）与拉罗萨（La Rosa）盐底辟。本次研究的地质图、剖面图与露头观测结果支持如下假说：影响东前贝蒂克带的主要中生代裂谷作用阶段发生于晚侏罗世至桑托期（Santonian），与西特提斯洋域（Western Tethyan area）内伸展盆地的发育同期。该被动陆缘的近源区域随后被并入贝蒂科薄皮褶皱冲断带的外部区段。研究区晚白垩世至新生代的构造演化涵盖以下阶段：坎潘期至阿基坦期的NW向挤压作用；布尔迪加尔期至上中新世主盐下断层的伸展复活；以及萨拉维利期的NW向挤压复活。在此背景下，先期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挤出过程。