LITHOLOGIC CONTROL on EROSION IN THE DINARIDES: IMPLICATIONS FOR STRAIN DISTRIBUTION IN AN ACTIVE FOLD AND THRUST BELT

Active mountain ranges are shaped by the complex interplay between climate, tectonics and erosion. In active orogens, such as the Olympics, Northern Apennines, or Himalayas, the erosional component of this feedback loop is reflected as a dendritic surface drainage pattern; which can be quantified using physical characteristics such as slope, and catchment area. The Dinarides of Croatia and Bosnia-Herzegovina are the actively deforming Adria-Eurasia boundary; however, the Dinaric topography differs greatly from similar sized active orogens, such as the neighboring Apennines. The Dinarides include two distinct regions with contrasting surface drainage patterns: the surface drainage of the External Dinarides is a series of disconnected internally drained basins, whereas, the Internal Dinarides much more closely resembles the Northern Apennines with well connected basins and waterways. We used SRTM DEMs to characterize surface drainage in the Dinarides and found a strong correlation between rock-type and rface connectivity. Specifically, disconnected internally drained basins are restricted to lithologies highly susceptible to chemical dissolution, whereas, heterogenous rock types resulted in typical dendritic drainages.

Our results have several general and regional implications. First, the timing of Dinaric mountain building is debated, and while much of the literature regards the Dinarides as inactive since Eocene time, several lines of evidence suggest that instead mountain building here is ongoing (e.g. geodetically measured shortening rates, and Miocene micro-fossil assemblages in limited tectonic flysch basins). Fueling this debate is the lack of flysch deposition, a hallmark of active uplift and erosion, which can be accounted for by the absence of an efficient means of surface transport and the lithologies’ susceptibility to chemical dissolution. A more general implication is that since in the Dinarides lithology strongly influences distribution of erosion and, therefore, the tectonic-erosion feedback loop, it may be the case in the Dinarides that lithology directly influences strain distribution.