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Publisher Summary This chapter discusses high-resolution seismic profiling in lakes coupled with targeted coring that provides powerful tools for the comparative analysis of environmental change along the Pole-Equator-Pole: Americas (PEP 1) transect. Mapping seismic unconformities in Lake Titicaca, Lake Mascardi, Laguna Cari-Laufquen Grande, Laguna Miscanti, Great Salt Lake, and Yellowstone Lake builds the acoustic stratigraphic framework to interpret the history of lacustrine sedimentation, and choose optimal coring sites for multiproxy sediment studies. Most of these seismic unconformities are associated with past lake-level changes. Lake Mascardi exemplifies a proglacial lake sequence. Seismic, and coring evidence indicates two major phases of environmental change coinciding with the late glacial/Holocene transition, and a lower amplitude change within the mid- Holocene sequence. Lake Titicaca, and Laguna Cari-Laufquen Grande illustrates the acoustic character of relatively closed basins without direct glacial overprints. Laguna Miscanti describes acoustic layering in a small, groundwater-fed saline lake, and distinctive evidence for mid-Holocene desiccation phase. Great Salt Lake acoustic stratigraphy documents a cold playa to deep Lake Bonneville evolution, followed by drastic drawdown to variable Holocene depths from near desiccation to modern levels. Profiles document neotectonic faulting. Yellowstone Lake illustrates acoustic signatures in a large caldera. Results for these lacustrine basins of different origins, and latitudes show that paleoclimate patterns lead to characteristic acoustic packages. Lakes commonly have sediment sequences with high-impedance contrasts, and acoustic boundaries are equivalent to lithological changes related to environmental dynamics. A feature that stands out is a distinctive shift in seismic facies in each system corresponding to glacial/Holocene transition. |
