engleski

DEM–based morphometric analysis of Bilogora Mt. area (NE Croatia): landscape response to neotectonic activity

Earth’s surface as dynamic equilibrium system, consequently shaped by climatic conditions, active tectonics and erosional processes represent fundamental research objective for many geomorphic analysis performed using digital elevation models (DEMs). Here we analyze the drainage basins in Bilogora Mt. area identifying possible neotectonic signature by means of DEM based morphometric analysis. Composed of highly deformed and variable in thickness Pliocene-Quaternary clastic sediments, Bilogora Mt. represents young transpressional morphostructure related to the NW-striking Drava basin boundary fault (DBBF). Suggested by Prelogović et al. (1998), Bilogora Mt. was formed during Pliocene and Quaternary times at the SW margin of Drava basin as result of DBBF inversion from initial normal into dextral slip sense of motion. Still ongoing tectonic activity is reported trough historical and instrumental records of moderate earthquakes with intensity of VI°-VIII° MCS ((3, 5≤ML≤5, 6). Mostly concentrated in the northwestern part of Bilogora Mt., horizontal stress direction is orientated NE-SW indicating steeply NE-dipping, and S-SW dipping seismogenic structures with strike-slip and reverse motions (Herak et al., 2009). Possible landscape response to ongoing neotectonic activity was examined by ESRI ArcMap 9.x.x. software package with CalHypso, Spatial Analyst, ArcHydro 1.1 and StPro extensions. Utilizing 10m DEM raster, morphometric analysis was performed on 130 drainage basin units computing morphometric parameters of: hypsometric curves and hypsometric integral, Hi ; absolute asymmetry factor, AF(abs) and statistical parameters of longitudinal stream profiles, i.e. maximal concavity, Cmax ; distance from the source, Δl/L, concavity factor, Cf ; steepness index, ksn and concavity index, θ. Convex hypsometric curves, Hi≥0.50 values, AF(abs)≥0.25 values and statistical parameters of main longitudinal streams profiles (Cf≤32.16%, Cmax≤0.265 positioned in upper reach of streams, θ values between 0.73-1.01 ; and avg. ksn values between 10.05- 12.70) suggested that several drainage basins and streams dominantly in NW and central part of Bilogora Mt. (near towns of Koprivnica, Đurđevac and Bjelovar) and few of them on SW slopes in SE part (between towns of Virovitica and Daruvar) are probably experiencing on-going neotectonic deformation which is reflected in a present-day landscape. Consequently, delineated drainage basins are considered as areas in younger erosional stages characterized by stream rejuvenation following less gradation and non-equilibrium steady state, tectonic warping of main streams and active block tilting which correlate very well with subsurface folds produced by either normal-inverted or younger reverse faults Late Pontian-Quaternary in age.

Bilogora Mt.; DEM; morphometric indices; landscape; neotectonic activity

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