ABSTRACT

The Punta Bianca Unit (NW Italy) is a continent-derived metamorphic unit that experienced underthrusting and later exhumation in the hinterland sector of the Northern Apennines fold-and-thrust belt. We present a novel 1:5000 scale geological map that aims to illustrate the polyphase tectonic evolution of the Punta Bianca Unit and its relationships with non-metamorphic units. The geologic data presented in the map are coupled with the structural analysis of the main tectonic elements, lithostratigraphic, finite strain and microstructural data that allow to highlight the tectonic history of the study area. In particular, we recognized that the Punta Bianca Unit underwent an early phase of underplating (D1), followed by syn-orogenic exhumation to shallow crustal levels and coupling with the overlying Tuscan Nappe (D2), and nappe stacking/refolding (D3). Low-angle semibrittle (D4) and high-angle brittle (D5) faulting affected both the Punta Bianca Unit and the Tuscan Nappe during the latest stages of deformation.

摘要

蓬塔比安卡单元（意大利西北部）是源自大陆的变质单元，在北亚平宁山脉褶皱-冲断带的腹地部门经历了下冲作用和后来的发掘。我们提出了一种新颖的1：5000比例尺的地质图，旨在说明蓬塔比安卡单元的多相构造演化及其与非变质单元的关系。地图中显示的地质数据与主要构造元素的结构分析，岩石地层学，有限应变和微观结构数据相结合，可以突出研究区域的构造历史。特别是，我们认识到，蓬塔比安卡单元经历了早期的下垫层（D1），随后通过同造山法发掘到浅层地壳，并与上覆的托斯卡纳纳皮（D2）耦合，和尿布堆叠/重新折叠（D3）。低角度半脆性（D4）和高角度脆性（D5）断层在变形的最新阶段影响了Punta Bianca单元和Tuscan Nappe。