Seismic stratigraphy, buried beach ridges and contourite drifts: the Late Quaternary history of the closed Lago Cardiel basin, Argentina (49°S)

Abstract

The results of a seismic stratigraphic analysis of a closed lake basin, Lago Cardiel, in southernmost South America are reported. Very few high‐resolution, continental records spanning the Late Quaternary have been obtained from this region. Seismic sequence stratigraphic analysis allows a reconstruction of lake level variations. Two major hiatuses of unknown age occurred during the early evolution of the basin with the deposition of an alluvial fan in a restricted area in the intervening time period. Following the development of a relatively shallow lake during the late Pleistocene and a short desiccation pulse around 11 220 14C yr BP, a transgression of over 135 m occurred at the beginning of the Holocene. The transgression was associated with the formation of beach ridges preserved in the lake stratigraphy on the floor of the modern Lago Cardiel at four different elevations. The preservation of largely unreworked beach ridges indicates a stepwise rise in the lake level. There is no seismic evidence of a major lowering of the lake below modern level during the entire Holocene. Deposition since the mid‐Holocene is marked by strong lateral differences in sediment accumulation with a depocentre slightly to the north of the basin midpoint and a pronounced mounded distribution. Seismic reflection geometries, as well as sedimentological characteristics indicate a lacustrine contourite drift covering an area of 80–100 km2. As Lago Cardiel is under the influence of westerly winds, these most likely drove lake circulation. The identification of drowned beach ridges and of contourite drifts illustrates that high‐resolution seismic stratigraphy is not only a powerful tool in reconstructing past lake level elevations for closed lake basins, but it can also provide information about the rate of lake level changes and the presence and strength of lake currents.

Transient simulations, empirical reconstructions and forcing mechanisms for the Mid-holocene hydrological climate in southern Patagonia

“…In this respect our simulations indicate a stronger seasonal variability of the SHWs throughout the whole mid-Holocene from 7 ka BP until 4.5 ka BP compared to preindustrial conditions, and thus do not support the hypothesis formulated in Markgraf (1993) and Markgraf et al (2003). The hypothesis of Gilli et al (2005a) and Markgraf (2005a) is only partly consistent with our simulations since stronger SHWs are only evident during DJF and SON (not shown), whereas during JJA and MAM (not shown) the SHWs are reduced. This result points towards the importance of seasonal differences in the strength and position of the SHWs during the midHolocene compared to pre-industrial conditions.…”

Quaternary lacustrine braid deltas on Lake General Carrera in southern Chile

“…8 and 15). Similar beach embayments, gently concave towards the lake, are characteristic of other lacustrine deltas in this region (Gilli et al, 2005). Bowman (1990) and Klinger et al (2003) illustrated comparable beaches alongside lacustrine fan deltas of the Dead Sea.…”

Holocene Hydroclimate Variability in Central Scandinavia Inferred from Flood Layers in Contourite Drift Deposits in Lake Storsjön

“…They can export sediment plumes containing river suspended load far away from the delta into deep basins. Lacustrine contourite deposits have been described in lakes with different basin shapes, depths and circulations patterns, e.g., in Lake Superior [41], East African Lakes [42], Lake Baikal [43], Lake Geneva [35] and Patagonian Lakes [38]. These drift deposits are either resulting from the influence of the Coriolis force on the displacement of sediment plumes at the lake floor, and/or from the interaction of hyperpycnal flood events (or turbidity currents) with currents at the lake floor generated by wind-induced internal waves or gyres.…”

“…Detrital layers have been explored to reconstruct flood occurrences, but such studies are essentially limited to smaller lakes or sites in the vicinity of tributary rivers [25,26,28,32]. For larger lakes, currents associated with flood events or linked to specific wind regimes can modify the distribution of flood layers [33][34][35][36][37][38][39][40]. Hyperpycnal flows during flood events are strongly controlled by and tend to maintain, the lake floor morphology (i.e., channels).…”