Modes and rates of horizontal deformation from rotated river basins: Application to the Dead Sea fault system in Lebanon

Abstract

Partitioning of horizontal deformation between localized and distributed modes in regions of oblique tectonic convergence is, in many cases, hard to quantify. Here we use the geometry of river basins and numerical modeling to evaluate modes and rates of horizontal deformation associated with the Arabia-Sinai relative plate motion in Lebanon. We focus on river basins that drain Mount Lebanon to the west and are bounded by the Yammouneh fault, a segment of the Dead Sea fault system that transfers left-lateral deformation across the Lebanese restraining bend. We quantify a systematic counterclockwise rotation of these basins and evaluate drainage area disequilibrium using the c metric. The analysis indicates a systematic spatial pattern whereby tributaries of the rotated basins appear to experience drainage area loss or gain with respect to channel length. A kinematic model reveals that since the late Miocene, 23%-31% of the relative plate motion parallel to the plate boundary has been distributed along a wide band of deformation to the west of the Yammouneh fault. Taken together with previous, shorter-term estimates, the model indicates little variation of slip rate along the Yammouneh fault since the late Miocene. Kinematic model results are compatible with late Miocene paleomagnetic rotations in western Mount Lebanon. A numerical landscape evolution experiment demonstrates the emergence of a similar pattern of drainage area disequilibrium in response to progressive distributed shear deformation of river basins with relatively minor drainage network reorganization.

Landscape ‘stress’ and reorganization from χ‐maps: Insights from experimental drainage networks in oblique collision setting

“…; Goren et al. ). Yet, when the crust deforms horizontally, the bedrock river network that is carved at its surface is expected to deform accordingly.…”

“…The deformation of the drainage network can also induce variations in upstream drainage area (Goren et al. ). As a result of these two processes, the χ value becomes higher at point A with respect to point B (Equation .…”

“…In this configuration, χ values are higher on one side of the divide separating adjacent basins compare to the other side (Figure ), as documented, for instance, along the western flank of Mount Lebanon (Goren et al. ). The divide between points A and B is affected by a gradient in χ (Δ χ ) and it is thus in an unstable configuration, hereafter named ‘stressed divide’.…”

Drainage reorganization and divide migration induced by the excavation of the Ebro basin (NE Spain)

“…The pursuit of such a long-term capture trend may be driven by tectonic and/or climatic forcing (Willett, 1999;Montgomery et al, 2001;Bonnet, 2009;Whipple, 2009;Castelltort et al, 2012;Kirby and Whipple, 2012;Goren et al, 2015;Van der Beek et al, 2016). However, such a long-term trend in drainage reorganization may also occur in tectonically quiescent domains, independent of external forcing (Prince et al, 2011).…”

Coupling slope–area analysis, integral approach and statistic tests to steady-state bedrock river profile analysis

“…How to retrieve such details has long been a focus in both geologic and geomorphologic studies (Flint, 1974;Wobus et al, 2006;Rudge et al, 2015). Most of these studies are based on a well-known power-law relationship between local channel gradient and drainage area (Flint, 1974;Hack, 1973;Howard and Kerby, 1983):…”