Proceedings of the 12th International INQUA meeting on paleoseismology, active tectonic and archaeoseismology

Takhilt Lake Two core sediments were recovered (TAX23-01 and TAX23-02) from Takhilt Lake. The lake has a maximum length of 3 km and a maximum depth of 6 m. The lake has a main tributary to the northeast and some ephemeral tributaries to the west and south of the lake. The topography around the lake is quite gentle. The cores have lengths of 72.5 and 110 cm. Both are mainly composed of dark-brown mud interrupted by 4 laminates of 5-10 mm thick of grey- whitish (possibly silty) color. These laminates are located between 24 and 42 cm in depth within the cores and are more evident in core TAX23-01. The longest core (TAX23- 02) records the sedimentation history over the past ~1.7 kyr and yields an average sedimentation rate of 0.38 mm/yr. Silicates and Ti- profiles reveal four distinct layers, each approximately 20 mm thick, that display a relatively high contrast compared to the overall composition of the core samples, and with a gradual upward decrease of the elements within each layer. Oygon Lake Three cores were recovered from the western side of the lake. The lake has a maximum length of 15 km (east- west), with a gentle topography on the northern side, while steep slopes and escarpments are dominant along the southernsideof the lake(Figure2). Suchtopographic contrast is evident in the bathymetry, where a higher slope and the depocenter are localized in the proximities of the south shoreline. Cores Lake4-23-01, 02, and 03 are 59, 135.5, and 141 cm long, respectively. The cores are mainly composed of mud and silty sediments. Sedimentary laminae with thicknesses ranging from 1 mm to 10 mm exhibit a variety of colors including light gray, olive green, light brown, and dark tones (Figure 3). We believe that the wide variety of colors in these laminations is associated with varved sediment records and biological activity proper of salt lakes. These cores exhibit exceptional sediment preservation, allowing for the distinction of laminations associated with very recent sedimentation (likely last century, Figure 3). The sedimentary record of these cores spans over the last ~3kyr, yielding an average sedimentation rate of 0.4 mm/yr. This means that we should find a signature of the 1905 M8 earthquake within the first 4 cm. which is consistent with the most recent peak of Ti and silicates at 4.3 cm from the top of core Lake4-23-01 (Figure 4). Moreover, based on the Fe profile, we can identify up to four additional laminae deposits likely associated with earthquake-triggered turbidites. These peaks interestingly seem to be organized in two pairs, hence we took a 10 cm long sediment sample to prepare a thin section and characterize the facies associated with these peaks (ongoing work). Finally, in the last 25 cm toward the base of core Lake4-23-02, and 03, we observed a layer of grey clay-size material likely related to glacial sedimentation (Vasquez A & Foncea, 2013). Fig. 2: Field photo taken from the north side of the Oygon Lake, located 5 km south of the Bulnay fault. All three lakes share the same distinctive very-low relief. The nearest mountains are located 6-7km to the south.