Sand Compositional Changes As A Key For Sequence-Stratigraphic Interpretation: The Pleistocene Tiber River Deltaic Succession (Italy)
The use of variation in sand composition as a tool in sequence stratigraphy is still in an early stage and requires more case studies to test its effectiveness in sequence interpretation. Depositional cycles and sequence boundaries are well defined for late Quaternary wave-dominated Tiber delta deposits that crop out along the Lazio coastal margin near Rome, Italy.The aim of this study is to define the relative contribution of autogenic and allogenic processes on the late Quaternary Ponte Galeria sequence and petrofacies development, as well as compositional trends from base to top of the succession. Integration of sand provenance with sequence stratigraphic interpretation will better constrain the contribution of tectonic uplift in the source region (e.g., higher sediment lithic proportions), volcanism (e.g., higher volcanic lithic proportions), and eustacy and coastal reworking (e.g., higher quartz content) in controlling the evolution of the Ponte Galeria depositional sequences.Sand samples collected from the Tiber River and its tributaries are being analyzed to evaluate the contribution of the geologic units that crop out in the drainage basin to the Tiber River sediment composition. Preliminary results show that modern sand samples from the Tiber River contain a high percentage of lithic sedimentary grains upstream (e.g. siltstone, limestone) with increasing volcanic lithic content downstream. Along the coastline dense mineral derived from the volcanic rocks are more abundant. Limestone lithics and quartz grains increase in roundness downstream and along the coast. This model of compositional trends along the modern river and river mouth will help to interpret detrital modes determined for 29 sand specimens sampled from two measured and correlated sections in the Pleistocene fluvial and coastal-barrier deposits related to Paleo-Tiber River wave-dominated succession.
AAPG Datapages/Search and Discovery © 2014 Pacific Section AAPG, SPE and SEPM Joint Technical Conference, Bakersfield, California, April 27-30, 2014