A 3400 year lacustrine paleoseismic record from the North Anatolian Fault, Turkey: Implications for bimodal recurrence behavior

Abstract

High-resolution physical, geochemical, and geochronological analyses on the sedimentary sequence of Yeniçağa Lake, located in a fault-bounded basin along the North Anatolian Fault, reveal fingerprints of paleoearthquakes. A robust sediment chronology, spanning the last 3400 years, is constructed by radiocarbon dating and time-stratigraphical correlation with the precisely dated Sofular Cave speleothem record. Yeniçağa sedimentary sequence contains 11 seismically induced event deposits characterized by siliciclastic-enriched intervals. Some of the event deposits are also associated with implications of sudden lake deepening, which may be related to coseismic subsidence. The paleoearthquake series having an average recurrence interval of ca. 260 years are interrupted by two possible seismic gaps of ca. 420 and 540 years.

Seismically-triggered organic-rich layers in recent sediments from Göllüköy Lake (North Anatolian Fault, Turkey)

“…More recently, Avşar (2014) reported similar observations related to three earthquakes in Turkey; the 1998 Adana-Ceyhan Earthquake (Mw=6.2), the 1999 İzmit (Mw=7.4) and Düzce (Mw=7.2) earthquakes. This kind of change in sediment influx can be observed in lacustrine sedimentary sequences in terms of increase in sedimentation rates, content of clastic fraction, sediment density and mean grain-size (e.g., Doig, 1986;1990;Boes et al, 2010;Howarth et al, 2012;Hubert-Ferrari et al, 2012;Avşar et al, 2014).…”

“…Lacustrine sedimentary traces of earthquakes reported in the literature are summarized and illustrated as a stratigraphical columnar section in Figure 1 (Avşar, 2013). Consequences of earthquakes on sedimentation are subdivided into two main groups based on timing: i.e.…”

“…In addition to the geochemical properties of the sediments, raw ITRAX datasets bear traces of the physical properties of the sediments like water and organic matter content. In order to minimize these effects and to evaluate relative changes in elemental profiles, inter-element ratios are accepted as more reliable proxies for paleoenvironmental and paleoclimatic interpretations (e.g., Croudace et al, 2006;Kylander et al, 2011;Avşar, 2013). Figure 6 presents the inter-PC ratios along the Göllüköy piston core.…”

“…In order to determine the amount of reworking effect on our sediment chronology, we compare our proxy record with another precisely dated record from the region. Avşar et al (2014) showed that regional time-stratigraphic correlations between proxy records can be a strong tool to cross-check or even to improve age-depth models in Anatolia. Figure 9B presents the overlapped plots of the Göllüköy composite LOI 550 profile based on constant S.R.…”

“…Not only the LOI 550 profile but also the ratio of sulphur (S) to the detrital aluminosilicate elements (e.g., Si, K, Ti and Fe) correlates with the δ 18 O record of Nar Lake ( Figure 9E). Avşar et al (2014) demonstrated that this ratio can be used as a proxy to evaluate paleoclimatic conditions in Yeniçağa Lake, which is located ~ 470 km to the west of Göllüköy Lake. Accordingly, warmer and wetter climatic conditions favour high biogenic production in and around the lake, which results in organic S enrichments in the sedimentary sequence.…”