Geomorphosites in Granitic Environments: An Example from Northern Sardinia (Italy)

Abstract

Abstract:A rare geomorphosite and a pillow-like structure appearing as mingling structures due to that mafic and acidic magma interactions are described. Despite the occurrence of spectacular forms in the granitic basement of Sardinia, the morphosites of geological interest linked to the complex evolution of pluton emplacement are still poorly understood. The Fizza Ona outcrop, located near the northeastern coast, is a good example of a geomorphosite in the inner zone developed at the edge of different plutonic units. This outcrop is a well-exposed, pillow-like horizon of less than 5 m in thickness, observable in the field for at least 200 m and underlined by the occurrence of a large tafoni form. In detail, the pillow-like horizon consists of sub-roundly to sub-rounded elements of granitic to micropegmatitic rocks of up to 100 cm in diameter, which is dispersed in the fine-grained granitic host-rock matrix. The outcrop represents a particular example of the emplacement mechanism of granitic magmas in the Sardinian batholith. One aim of this work is the construction of a document for the competent authorities to protection and preservation of this outcrop as a cultural heritage for the history of the geological evolution.