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

Abstract

Multi-proxy analyses on the sedimentary sequence of Göllüköy Lake, which is located on the eastern North Anatolian Fault (NAF), reveals a complete and high-resolution paleoseismic record for the last 650 years. Six sedimentary events are detected in a 3.1 m-long piston core. They form distinct organic-rich intercalations within the background sedimentation, which are characterized by strong anomalies on the loss-on-ignition (LOI) and total organic carbon (TOC) profiles, as well as by lighter colours on the X-ray radiographic images. Itrax micro-XRF core scanner data are also used to contribute to the detection and characterization of the event deposits. After the detection of the sedimentary events, their temporal correlation with the earthquakes in the historical seismicity catalogue of the NAF is tested. The youngest event is dated to 1940s by using 210 Pb and 137 Cs profiles in sediment, which coincides with the 1939 earthquake (M s = 7.7) on the NAF. The ages of the older five events are determined based on radiocarbon dating and regional time-stratigraphic correlation. Radiocarbon dating on the bulk sediment samples does not provide reliable results due to hard-water effect. On the other hand, dating on charcoals, Ephippia of Daphnia and phragmite remains significantly improves the results and implies a mean sedimentation rate of 0.28 cm/yr. Based on this preliminary sedimentation rate, we show that organic matter content variations through our record correlates with the varve-based δ 18 O record of Nar Lake, which is located 350 km southwest of Göllüköy Lake. Accordingly, high-precipitation/low-evaporation climatic episodes detected in Nar Lake are represented by higher organic matter content in Göllüköy sediments. Fine-tuning the Göllüköy LOI record to the Nar δ 18 O record reveals that the ages of the sedimentary events in Göllüköy match with well-known historical earthquakes that occurred around the lake. Finally, the origin of the organic-rich intercalations is discussed based on macroscopic observations and organic geochemistry. The events are attributed to reworked organic matter eroded from the lake's littoral zone by seismically-induced water oscillations (seiche), and their subsequent deposition at the middle parts of the lake. These seismically-induced events are atypical compared to the classic earthquake-triggered sedimentary processes in lacustrine environments, which are shortly reviewed in order to emphasize the unusual Göllüköy Lake record.

Quantified sensitivity of small lake sediments to record historic earthquakes: Implications for paleoseismology

“…Therefore also when MMDs occur in only one lake, an earthquake trigger cannot be excluded. Hence, we use the temporal assignment of MMDs to their triggering earthquakes as a complementary way to determine the MMD trigger [e.g., Beck , ; Boës et al ., ; Avşar et al ., ; Howarth et al ., ; Moernaut et al ., ; Talling , ]. MMD ages were then compared to (i) the dates of the regional historical earthquakes that generated epicentral MSK intensities larger than IV and that occurred closer than 150 km from the lake (database SisFrance) (Figure ) and to (ii) the dates of other historical events known from documentary evidence, which affected some of the lake catchments [ Lignier , ; Nomade et al ., ].…”

Sedimentary records of past earthquakes in Boraboy Lake during the last ca 600 years (North Anatolian Fault, Turkey)

“…In addition to the seismically-triggered MWDs, the presence of a very recent non-seismically-triggered MWD in the Boraboy sequence allows comparisons to be made of sedimentological imprints of single-versus multi-source MWDs. We will also compare the Boraboy record with the record of Göllüköy Lake, which is another lacustrine paleoseismic record located ca 120 km to the east along the NAF (Avşar et al, 2014b) in order to improve our knowledge on the locations of the historical earthquakes in the region during the last 600 years.…”

“…7, modified from Avşar et al (2014b) None of the remaining historical earthquakes were recorded in the lake sequences, implying that they cannot be large characteristic earthquakes of the NAF.…”

“…Moreover, seismicallyinduced water oscillations (i.e., seiche) may cause in-situ sediment resuspension and redeposition (e.g., Siegenthaler et al, 1987;Doig, 1990;1991;1998a;1998b), or transportation of material from lake shores (e.g., Avşar et al, 2014b). In addition to subaqueous mass-wasting, earthquakes may trigger landslides in lake catchments, which may enhance sediment flux into lakes and leave sedimentary traces in the sequence (e.g., Leroy et al, 2009;Hubert-Ferrari et al, 2012;Avşar et al, 2014a;Howarth et al, 2012;.…”

A multi-centennial record of past floods and earthquakes in Valle d'Aosta, Mediterranean Italian Alps

“…In the case of earthquakes, ground shaking may disturb lake sediments by triggering coseismic in situ deformation or post-seismic deposits related to subaquatic mass movements of slope sediments and resuspension (e.g. Avşar et al, 2014;Van Daele et al, 2015). Identification and dating of all "event layers" in sediment cores enable us to reconstruct past event occurrences over centuries to millennia.…”