The Apennines are a retreating collisional belt where the foreland basin system, across large domains, is floored by a subaerial forebulge unconformity developed due to forebulge uplift and erosion. This unconformity is overlain by a diachronous sequence of three lithostratigraphic units made of (a) shallow-water carbonates, (b) hemipelagic marls and shales and (c) siliciclastic turbidites. Typically, the latter two have been interpreted regionally as the onset of syn-orogenic deposition in the foredeep depozone, whereas little attention has been given to the underlying unit. Accordingly, the rate of migration of the central-southern Apennine fold-thrust belt-foreland basin system has been constrained, so far, exclusively considering the age of the hemipelagites and turbidites, which largely post-date the onset of foredeep depozone. In this work, we provide new high-resolution ages obtained by strontium isotope stratigraphy applied to calcitic bivalve shells sampled at the base of the first syn-orogenic deposits overlying the Eocene-Cretaceous pre-orogenic substratum. Integration of our results with published data indicates progressive rejuvenation of the strata sealing the forebulge unconformity towards the outer portions of the fold-thrust belt. In particular, the age of the forebulge unconformity linearly scales with the pre-orogenic position of the analysed sites, pointing to an overall constant migration velocity of the forebulge wave in the last 25 Myr.

中文翻译：

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中南亚平宁褶皱冲断带（意大利）前陆盆地系统的前凸起迁移：新的高分辨率 Sr 同位素定年约束

亚平宁山脉是一条后退碰撞带，其中跨大域的前陆盆地系统被由于前凸起隆起和侵蚀而形成的地下前凸起不整合面所覆盖。这种不整合面被三个岩石地层单元的历时序列所覆盖，这些单元由 (a) 浅水碳酸盐岩、(b) 半远洋泥灰岩和页岩以及 (c) 硅质碎屑浊积岩组成。通常，后两者在区域上被解释为前渊沉积层中同造山沉积的开始，而对下伏单元的关注很少。因此，到目前为止，中南亚平宁褶皱冲断带-前陆盆地系统的迁移率受到限制，仅考虑半远洋岩和浊积岩的年龄，它们主要在前渊沉积层开始之后。在这项工作中，我们提供了新的高分辨率年龄，通过应用于方解石双壳类贝壳的锶同位素地层学，在覆盖始新世-白垩纪前造山地层的第一个同造山沉积物的底部取样。将我们的结果与已发表的数据相结合，表明地层正在逐步恢复，将前隆起不整合面朝褶皱冲断带的外部封闭。特别是，前隆起不整合面的年龄与分析地点的造山前位置成线性比例，表明前隆起波在最后 25 Myr 中的总体迁移速度是恒定的。将我们的结果与已发表的数据相结合，表明地层逐渐恢复年轻，将前隆起不整合面朝褶皱冲断带的外部封闭。特别是，前隆起不整合面的年龄与分析地点的造山前位置成线性比例，表明前隆起波在最后 25 Myr 中的总体迁移速度是恒定的。将我们的结果与已发表的数据相结合，表明地层正在逐步恢复，将前隆起不整合面朝褶皱冲断带的外部封闭。特别是，前隆起不整合面的年龄与分析地点的造山前位置成线性比例，表明前隆起波在最后 25 Myr 中的总体迁移速度是恒定的。