Spatial patterns of erosion and landscape evolution in a bivergent metamorphic core complex revealed by cosmogenic 10Be: The central Menderes Massif (western Turkey)

Abstract

In extensional provinces with low-angle normal faulting (such as the Aegean region), both tectonic processes and erosion induce landscape change, but their interaction during the evolution of topography and relief accompanying continental extension has rarely been addressed. Here we present local and catchment-wide 10Be erosion rates that document the spatial pattern of erosion in the central Menderes Massif, a metamorphic core complex consisting of two asymmetric mountain ranges (Bozdağ and Aydın) bound by detachment faults and active grabens. Catchment-wide erosion rates on the northern flank of the Bozdağ Range are rather low (40–110 mm/k.y.) but reach values of >300 mm/k.y. on the steep southern escarpment—a pattern that reflects both topography and bedrock lithology. In the Aydın Range, erosion rates are generally higher, with mean erosion rates of ∼190 and ∼260 mm/k.y. on the northern and southern flank, respectively, and more variable along strike. In both ranges, erosion rates of ridge crests derived from amalgamated clasts are 30–90 mm/k.y. The difference between local and catchment-wide erosion rates indicates that topographic relief increases in most parts of the massif in response to ongoing fault-related uplift and concomitant river incision. Our findings document that tectonic processes exert a significant control on landscape evolution during active continental extension and are reflected in both the topographic signature and the spatial pattern of erosion. In the Menderes Massif, rock susceptibility to weathering and erosion is a dominant factor that controls the erosional contribution to rock exhumation, which varies spatially between ∼10% and ∼50%.

Three-dimensional control of alluvial fans by rock uplift in an extensional regime: Aydın Range, Aegean extensional province

“…The relatively higher pattern of catchment-wide erosion rates in S3 and S5 likely confirms this view. The reason why previous 24 , 28 studies did not find any relationship between tectonics and catchment-wide erosion is probably that these earlier studies focused mostly on the western part of the range. Our new catchment-wide erosion data from the missing parts of the range have indicated that catchment-wide erosion mostly shows a pattern compatible with tectonic uplift across the range.…”

“…The alluvial fans are aligned along a segmented normal fault 23 , the catchments have not been glaciated over the duration of alluvial fan deposition 24 , the climate, and vegetation, within each catchment-alluvial fan system are very similar, and there is a mixture of mostly metamorphic and plutonic lithologies with some sedimentary rocks that are mapped 25 – 27 . Furthermore, the area offers a wide range of river incision and catchment-wide erosion rates 24 , 28 , as shown here. We interpret these as a function of differential rock uplift between the footwall catchments and hanging wall alluvial fan systems.…”

“…Catchment-wide erosion rates from 10 Be concentrations were calculated with the CRONUS-Earth online calculator ( http://hess.ess.washington.edu ) 68 using the primary calibration data set of Borchers et al 69 and the time-invariant production rate scaling model 70 , 71 . The new erosion rates are integrated with 16 previously published catchment-wide erosion rates 24 , 28 , 83 to examine spatial variability. We used the same cosmogenic production rate and scaling schema as the earlier studies in the study area to make an easy comparison.…”

“…To understand the spatial variations in erosion along the southern flank of the Aydın Range, we performed eight 10 Be-derived catchment-wide erosion rates. These new erosion rates were integrated with previously published 13 catchment-wide erosion rates 24 , 28 , 83 in the study area. To evaluate the possible role of lithology on erosion, lithological units for each catchment were reclassified into igneous, metamorphic, and sedimentary rocks.…”

Complex erosional response to uplift and rock strength contrasts in transient river systems crossing an active normal fault revealed by 10Be and 26Al cosmogenic nuclide analyses

“…Geological units are simplified from Kent et al (2021) with additional mapping of Holocene lake deposits from Süzen, Toprak and Rojay (2006). Numbers in bold indicate rivers sampled for cosmogenic radionuclides (CRN) either in this study (Table 1) or by Heineke et al (2019) or Buscher et al (2013) (Table 3) topographic graben (Çiftçi & Bozkurt, 2009). In the uplifted footwall of the active fault are friable sedimentary rocks deposited originally on the hanging wall of the Gediz detachment.…”