Abstract
The climate of the southwestern North America has experienced profound
changes between wet and dry phases over the past 200 kyr. To better
constrain the timing, magnitude and paleoenvironmental impacts of these
changes in hydroclimate, we conducted a multiproxy biomarker study from
samples collected from a new 76 m sediment core (SLAPP-SRLS17) drilled
in Searles Lake, California. Here, we use biomarkers and pollen to
reconstruct vegetation, lake conditions and climate. We find that δD
values of long chain n-alkanes are dominated by glacial to interglacial
changes that match nearby Devils Hole calcite δ18O variability,
suggesting both archives predominantly reflect precipitation isotopes.
However, precipitation isotopes do not simply covary with evidence for
wet-dry changes in vegetation and lake conditions, indicating a partial
disconnect between large scale atmospheric circulation tracked by
precipitation isotopes and landscape moisture availability. Increased
crenarchaeol production and decreased evidence for methane cycling
reveal a 10 kyr interval of a fresh, productive and well-mixed lake
during Termination II, corroborating evidence for a paleolake highstand
from shorelines and spillover deposits in downstream Panamint Basin
during the end of the penultimate (Tahoe) glacial (140–130 ka). At the
same time brGDGTs yield the lowest temperature estimates (mean months
above freezing = 9 ± 3°C) of the 200 kyr record. These limnological
conditions are not replicated elsewhere in the 200 kyr record,
suggesting that the Heinrich stadial 11 highstand was wetter than that
during the last glacial maximum and Heinrich 1 (18–15 ka).