Depositional architectural elements in turbiditic channelled systems. An example from the Gorgoglione Flysch turbiditic system (Basilicata, Southern Italy)

The reconstruction of depositional geometries, architectures and vertical stratigraphic relationships in turbiditic channel systems is crucial to understand the overall basin evolution. A field-based case study is presented from an important stratigraphic interval in the upper portion of the Gorgoglione Flysch Formation,a syn-orogenetic Miocenic turbiditic succession of the Southern Apenninic thrust-and-fold belt. This unit is exposed in Basilicata Region (southern Italy),with spectacular outcrops of 10-to-100-m-thickcoarse-grainedamalgamatedsandstone bodies incised into tabular heterolithic deposits, with lateral continuity of several km. The outcrop analyzed in this work, named Staircase section,is characterized bya ~50 m thick coarse-grained body, consisting of a mud-clast conglomerate mixed with extra-basinal, polymictic conglomerate, resting erosionally on underlying, finer-grained tabular deposits. Multiple sole structures with different orientations characterize the basal part of the erosional surface. This section has been examinedthrough a detailed stratigraphic measurement to create vertical and lateral correlations. Using measurements from multiple basal scoured surfaces,a paleoflow analysis has been created. Also high resolution giga-pixel imagery with carefully constructed annotated line-drawings allows the recognition of bed-scale geometry of the different elements characterizing this channelsystem. This approach reveals a complex and irregular geometry of the basal channel surface, a varied range of paleoflow directions,probably related to a turbulent depositional process, and transition in depositional regime likely due to external controls such as sea level change. The collection of this data will provide useful results for comparative analysis with previous depositional models and interpretation of the evolution of the Gorgoglione Basin.