Holocene mass-wasting events in Lago Fagnano, Tierra del Fuego (54°S): implications for paleoseismicity of the Magallanes-Fagnano transform fault

Abstract

High‐resolution seismic imaging and coring in Lago Fagnano, located along a plate boundary in Tierra del Fuego, have revealed a dated sequence of Holocene mass‐wasting events. These structures are interpreted as sediment mobilizations resulting from loading of the slope‐adjacent lake floor during mass‐flow deposition. More than 19 mass‐flow deposits have been identified, combining results from 800 km of gridded seismic profiles used to site sediment cores. Successions of up to 6‐m thick mass‐flow deposits, pond atop the basin floor and spread eastward and westward following the main axis of the eastern sub‐basin of Lago Fagnano. We developed an age model, on the basis of information from previous studies and from new AMS‐14C ages on cored sediments, which allows us to establish a well‐constrained chronologic mass‐wasting event‐catalogue covering the last ∼12 000 years. Simultaneously triggered, basin‐wide lateral slope failure and the formation of multiple debris flow and postulated megaturbidite deposits are interpreted as the fingerprint of paleo‐seismic activity along the Magallanes‐Fagnano transform fault that runs along the entire lake basin. The slope failures and megaturbidites are interpreted as recording large earthquakes occurring along the transform fault since the early Holocene. The results from this study provide new data about the frequency and possible magnitude of Holocene earthquakes in Tierra del Fuego, which can be applied in the context of seismic hazard assessment in southernmost Patagonia.

Eocene Paleoseismic Record of the Green River Formation, Fossil Basin, Wyoming, U.S.A.: Implications of Synsedimentary Deformation Structures In Lacustrine Carbonate Mudstones

“…Instability and failure of the slope can be triggered by processes intrinsic to the sedimentary environment itself, i.e., autogenic, or by external-allogenic-processes (e.g., G. Mastrogiacomo et al 2012). These include oversteepening or sedimentary overloading (e.g., Lewis 1971;Postma 1983;Stromberg and Bluck 1997;Owen and Moretti 2008), water-level changes (e.g., Rothwell et al 2000), tides (Wells et al 1980), storm waves (e.g., Osleger et al 2009), or earthquakes (e.g., Field et al 1982;Rossetti and Santos 2003;Monecke et al 2006;Carrillo et al 2006;Schnellmann et al 2007;Waldmann et al 2010;Marco 2011, 2012).…”

Mass movement deposits in the 3.6 Ma sediment record of Lake El'gygytgyn, Far East Russian Arctic

“…The lower density of the suspension leads to a turbid flow above the debris flow that is finally deposited in the lake basin as a normally graded turbidite, both on top and in front of the debris flow. Turbidites generated by and directly overlaying debris flows are common in lacustrine and marine settings (e.g., Schnellmann et al, 2005;Waldmann et al, 2010;Rothwell et al, 2000;Strachan, 2008). However, since the debris flows in most cases do not extend all the way to the lake center, the associated turbidites there are more widespread than other MMDs (Schnellmann et al, 2005;Juschus et al, 2009).…”

Holocene Event Record of Aysén Fjord (Chilean Patagonia): An Interplay of Volcanic Eruptions and Crustal and Megathrust Earthquakes

“…Moreover, epicenter locations and magnitudes of the responsible earthquakes have been estimated based on the appearance of simultaneously deposited landslides in different lakes (Kremer et al, 2017;Strasser et al, 2006). There is one study on prehistorical fault activity at Lago Fagnano (Waldmann et al, 2011) in the southern tip of Argentina, but this lake is located in a different tectonic setting. Wang et al, 2007), LOFZ, and volcanoes of south central Chile; (b) region around Aysén Fjord with indication of the Liquiñe-Ofqui Fault Zone (LOFZ) (after Cembrano et al, 2000;Melnick et al, 2009;Thomson, 2002;Vargas et al, 2013), volcanoes in the vicinity of the fjord, tephra, and pumice fallout isopachs of major Holocene eruptions in the area (H = Hudson, MEN = Mentolat and MAC = Macá) (after Naranjo & Stern, 1998, and the region of the 2007 seismic swarm and main shock (after Legrand et al, 2011;Mora et al, 2010); and (c) shaded relief map of the inner part of the fjord with indication of onshore and offshore mass movements that were triggered by the 2007 main shock of M w 6.2 on 21 April (after Sepúlveda et al, 2010;Van Daele et al, 2013).…”