by Donald T. Rodbell, Mark B. Abbott, Pedro Miguel Tapia Ormeño

Lake Junín, located at 4000 m asl in the inner-tropics of the Southern Hemisphere, is a prime target for drilling because it contains a thick (>125 m) sediment package deposited at a high rate (0.2 to 1.0 mm yr-1). Abundant research conducted on and around Lake Junín provides a compelling rationale for deep drilling. Moraine mapping coupled with cosmogenic radionuclide dating indicate that paleoglaciers reached the lake edge, but have not overridden the lake in as much as a million years. Lake Junín is one of the few lakes in the tropical Andes that predates the maximum extent of glaciation and is in a geomorphic position to record the waxing and waning of glaciers in nearby cordillera. Sediment coring of Lake Junín began in the 1970s; two cores spanning the past 50,000 years reveal that sedimentation has alternated between clastic sediments deposited during peak glacial periods and authigenic calcite (marl) precipitated from the water column during interglacial times. The lake also contains ideal sediments for multiproxy analysis that can be reliably dated using both the radiocarbon and U/Th methods. The oxygen isotopic composition of marl and ostracod carapaces demonstrate that it primarily records the isotopic composition of precipitation and secondarily the degree of evaporative enrichment of lake water. Lake Junín contains a continuous record of tropical hydroclimate over interglacial and interstadial intervals for much of the past several hundred thousand years that is both comparable to, and an extension of stable isotope records from regional ice cores and speleothems. New organic geochemical proxies compliment the marl isotope record and offer the potential for a truly continuous isotope paleoclimate record through glacial and interglacial intervals alike. Lake Junín is ideally situated, both from logistical and scientific standpoints, to provide continuous high-resolution, independentlydated, long-term records of glaciation, and the variability of phenomena such as ENSO, the South America Summer Monsoon, and the Intertropical Convergence Zone. Because of the strong, demonstrated U/Th dating potential of Junín marl, we will be able to address critical issues regarding the synchrony of climate change in the tropics with that in high latitude regions of both hemispheres, the rate and timing of ecosystem response to climatic perturbations, and the dynamics of the geomagnetic field from a tropical perspective. Lake Junín is a scientifically mature site that will yield critical scientific insights that only drilling coupled with analysis by a select international team of scientists can unlock.

• The primary objective of the proposed research is to develop the first continuous, high-resolution, accurately-dated late Quaternary record of climate change, glaciation, paleoecology and magnetic secular variation for the tropical Andes. Only two other long (>200,000 yr) late Quaternary sedimentary records from the tropical Andes exist, and these are not well dated beyond 40 ka. Specifically, our objective is to generate high-resolution multi-proxy records that can address key paleoclimatic, paleoecologic, and paleomagnetic questions that include:
• 1.What is the temporal relationship over multiple glacial-interglacial cycles between climate change in the tropics and that in extra-tropical regions of both hemispheres?
• 2.Do the Dansgaard-Oeschger cycles and Heinrich events that are evident in tropical Andean cave records over the past 50 ka persist through the last interglacial and prior glacial cycles, or are there intervals in which the southern tropics are forced more by climatic events in the Antarctic region?
• 3.Relative to the Holocene, was the frequency, duration, and magnitude of drought different during prior interglacials, and how does this inform us about forcing mechanisms such as ENSO, the South American Summer Monsoon, and strength and position of the ITCZ?
• 4.How do ecological communities respond to and recover from repeated climate change?
• 5.Have there been non-linear ecological responses to climate change?
• 6.Is there a causative link between paleomagnetic secular variation and precipitation in the tropics?

Carbonate Lakes, D18O, ICDP-2012/02, JUNIN, Lake Drilling, Lake Junin, Peru, South America, Tropical Climate Change

Latitude: -11.0365, Longitude: -76.1104