Abstract
In Central Sardinia (Italy), sub-economic concentrations of iron ore are diffuse along and close to the Middle Jurassic “Alpine Tethyan Unconformity”, featured by Variscan metamorphic rocks covered by the unconformable Middle Jurassic Genna Selole Fm. Sedimentological and paleopedological investigations have been carried out to assess the areal extent and the nature of those concentrations, their origins, and their paleoclimatic, paleoenvironmental, and paleotectonic meanings. Transformation processes showing complex features such as alteration halos, mineral dissolution, reprecipitation, or pedogenetic profiles have been documented. Thus, several processes suggesting phases of variable duration of uplift, exposition to the external agents and erosion of the Variscan basement, and periods of sediment starvation of the superposed Genna Selole Fm deposits have been noted. Additionally, pedological processes occurred during the slowing down of the superposed Genna Selole Fm sedimentation. The alteration deposits differ according to their stratigraphic location. They are from solid, discrete masses to thin beds, crusts, and veins of Fe oxides. They may be of supergenic origin or related to sedimentary processes. The paleosols are Plinthosols related to warm-humid climates with a short dry season. These results provide additional data to 1) better define the depositional environments of the Genna Selole Fm, 2) indicate the episodic presence of ephemeral subarid periods in a dominantly humid Jurassic climate, and 3) document the tectonic evolution of a well-delimited area during this period. This investigation shows how the interdisciplinary use of sedimentological and paleopedological data can be helpful for paleotectonic, paleoenvironmental, and paleoclimatic reconstructions.