The stratigraphic architecture of Macco (middle Pliocene) in the Tarquinia Basin as controlling factor in the Monterozzi Necropoli placement.

The Middle Pliocene shallow water deposits cropping out in Tuscany and Latium (Central Italy) are represented by a lithostratigraphic unit, known as “Macco” (Fazzini et al., 1972). In the Tarquinia basin, the Macco consists of poorly lithified bioclastic calcarenites intercalated with hybrid sandstones and sandstone often with lateral heteropic transitions. The skeletal assemblage is dominated by free living branches of coralline algae, molluscs and foraminifers deposited in a carbonate ramp environment. The terrigenous fraction is mainly composed of monocrystalline grains of quartz and subordinate detrital micas and feldspars, sedimentary lithoclasts (arenites, siltites, sparse limestones). Glaucony grains and opaques are also present. Based on new field survey in the area and on the comparison with previous works, a new geological map of Tarquinia area has been produced. Multiscale morphologic and structural analysis shows that morphostructural lineaments are fault-controlled mostly by E-W and NW-SE striking fault and fracture zones, locally interested by calcite-bearing veins. Widespread evidence of transtensive syn-sedimentary tectonics is documented by thickness and facies variations across faults, slumps and fault-related unconformable contacts. In the Tarquinia area, this lithostratigraphic unit hosts the Etruscan necropolis of Monterozzi, UNESCO site since 2004. The necropolis consists of more than 6000 burials of different typology (room tombs, pit tombs and hole tombs) spanning a chronological period from 7th to 2nd century BC (Cataldi 1993; 2001). The aim of this work is to evaluate how the stratigraphic architecture of Macco may have influenced the distribution of burials.