Gravity-Accommodated `Structural Wedges' AlongThrust Ramps: A Kinematic Scheme of Gravitational Evolution

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• 作者：Iovine ; Giulio ; Tansi ; Carlo
• 关键词：wedge ; shaped structure ; lateral spread ; deep ; seated gravitational slope deformations ; kinematic mechanisms ; structural setting ; meso ; structural statistical analyses ; Southern Apennine chain
• 刊名：Natural Hazards
• 出版时间：1998
• 出版年：1998
• 期刊代码：33_0921030X
• 类别：soc
• 卷：17
• 期：3
• 页码：195-224
• 数据来源：sp

摘要

In active geodynamic areas, such as the ItalianSouthern Apennines, the specific structural conditionshave a profound effect on both the superficial anddeep gravitational evolution of slopes. Chain sectorscommonly exhibit structural complexities due to thesuperimposition, in space and time, of diversetectonic stress fields. In this paper, attention isfocused on particular structural configurations,connected to the tectonic quaternary phases that haveaffected the Southern Apennines, constituting apeculiar type of lateral spread gravitationaldeformations – which have not been previouslydescribed.

The study area is characterized by regional roughlyeast-verging overthrusts (Holigo–Miocene).Superimposed on these, is a system of transpressivethrust ramps (Quaternary), connected to the activityof strike-slip faults. The latest tectonic phase,still active, has been characterized by an extensionalstress field, which has produced differentiateduplifts along normal faults. All these factors haveencouraged an intense and widespread processes oferosion, the creation of considerable relief energyand the development of both superficial and deepgravitational phenomena.

It has been ascertained that the late extensionalphases favoured gravitational reactivations (withnormal movements) along those most recent thrust rampswhose attitude was kinematically consistent with themain extension direction of the stress field. Suchreactivations were `accommodated' by antitheticneo-formational structures – these are also characterizedby normal kinematics. Overall, such mechanisms lead tothe individuation of wedge-shaped rock portionsdelimited by the normally reactivated thrust ramps, onone side, and by the antithetic structures, on theother.

Structural wedges represent a particular type oflateral spread phenomena. On the basis of theirorientation with respect to the orography, threetypical situations have been defined: (1) wedgeperpendicular to the ridge; (2) wedge parallel to theridge; (3) wedge oblique to the ridge.

In this paper three Calabrian case studies,exemplifying the above-mentioned situations, aredescribed. The same framework can be applied tosectors of chain with an analogous structural setting,for a better understanding of the kinematic featuresof observed gravitational phenomena.