Mid- to Late Holocene geomorphodynamics in a long-term settled mountain catchment in the Pergamon micro-region, western Turkey

Abstract

From 300 BC to AD 300, the city of Pergamon underwent a profound transformation that impacted the rural settlement patterns and the concomitant geomorphodynamics. We present a geoarchaeological study in a long-term settled catchment in the Pergamon micro-region to disentangle the Holocene geomorphodynamics and triggering factors, for example, climate change and human activity. The analyses of eight radiocarbon-dated sediment profiles from the Tekkedere alluvial fan and its catchment indicate four principal sedimentation phases. Phase 1 (ca. 6.2 to 5–4 ka) is dominated by the floodplain aggradation of the receiving Bakırçay River, which is followed by the formation of floodplain soils (phase 2). Substantial geomorphodynamic changes occurred around 4 ka (phase 3), when the edge of the floodplain was buried by fan sediments of the tributary Tekkedere creek. This is attributed to supraregional aridization and rapid climate change events, superimposed by the onset of local human activities. Repeated cycles of coarse- and fine-textured fan sediments with age inversions after ca. 3.8 ka and valley infills younger than 1300 yr BP indicate the strong erosion and redeposition of sediments in phase 4. These increased geomorphodynamics may coincide with the changing settlement pattern and thus reflect human–environment interactions.

Holocene geomorphodynamics of a rural catchment in the Pergamon micro-region (eastern Mediterranean)

“…This, together with the ceramic remain found in Del-4, unit 5 (Supplemental Figure S4, available online), suggests human activities that likely affected the soil erosion. This is analogous to multiple studies in the Pergamon micro-region where the Middle to Late Holocene landscape shifted from natural to cultural, including processes of woodland clearing, pasture, and agriculture (Schneider et al, 2017; Shumilovskikh et al, 2016; Yang et al, 2023). Many findings all over the Mediterranean region also emphasize the interrelation between settlement activities and land degradation during the Bronze Age (e.g.…”

“…Mid-Holocene low geomorphodynamics were also observed at a regional scale, for example, in the nearby Tekkedere catchment around 5–4 cal ka BP (Yang et al, 2023) and the western lower Bakırçay plain (Pergamon micro-region) around 4.3–4 ka BP (Becker et al, 2020). Simultaneously, low accumulation rates are reported during ca.…”

“…This further denotes the lateral upslope extension of the alluvial fan (Table 4). These young sediments exposed in Del-6 were roughly deposited contemporaneously to the valley bottom sediments in the nearby Tekkedere catchment (Yang et al, 2023), probably corresponding to the “Younger Fill” (Vita-Finzi, 1969) in the Mediterranean valleys (Roberts, 2014; Roberts et al, 2019b). The time of erosion should take place after the beginning of the Late Holocene (phase 5: ca.…”

“…These sub-facies are summarized into facies B, alluvial fan facies, and facies C, floodplain facies (Table 2). The classification resembles the facies described in Tekkedere alluvial fan (Yang et al, 2023), following the conventional sedimentological terminology of alluvial fan (Blair and McPherson, 1994, 2009; Moscariello, 2018) and floodplain deposits (Miall, 2006, 2014).…”

“…This transformation increased the intensity of human impacts on land use both in and around the city and its villages (Günther et al, 2021; Laabs and Knitter, 2021). Beyond, sediment archives from the micro-region indicate local-scale changing geomorphodynamics during the Middle and Late Holocene (Schneider et al, 2013, 2014, 2015; Seeliger et al, 2019; Yang et al, 2023), roughly corresponding to the fluctuations in hydroclimate, vegetation, and settlement activities in the micro-region and its neighboring areas (Becker et al, 2020). The intensified geomorphodynamics, in essence, correspond to soil erosion processes, as pointed out also for many areas in the eastern Mediterranean (Dusar et al, 2011; Roberts et al, 2019a; Walsh et al, 2019).…”