Beschreibung
Two outstanding high-resolution paleoclimate datasets spanning multiple glacial/interglacial cycles in the northern Neotropics are the ~400 ka-paleoenvironmental records of Lake Chalco, central Mexico, and Lake Petén Itzá, northern Guatemala. Despite their geographical vicinity, previous paleoclimate studies demonstrated significant inter-regional differences such as strongly contrasting climatic conditions during the Last Glacial Maximum and Heinrich Stadial 1 at both sites. Continuous and undisturbed sediment sequences obtained during ICDP projects “Petén Itzá Scientific Drilling Project (PISDP)” and “MEXIDRILL: The basin of Mexico Drilling Program” provide, for the first time, the opportunity for detailed studies of effects and causes of continental climate change in the northern Neotropics. In this project, we will generate high-resolution paleoclimate, paleoecological and paleoenvironmental records from both ICDP sites by combining bulk-geochemical and lipid biomarker analyses with aquatic paleobioindicators (such ostracodes) over the last glacial/interglacial cycles.
For this, modern ecological calibration datasets and temperature transfer functions from central Mexico to Central America and variance ratios, to precisely determine the effects of environmental variables, ecological interactions and random drift in structuring bioindicator communities will be established. Information from these modern training sets will be applied to Lake Chalco and Lake Petén Itzá sediments and used to quantify the magnitude and velocity of ecological changes in both aquatic ecosystems as a response to climate change. Ostracode distributions and abundances will allow reconstructing lake-specific environmental parameters (such as lake level variation and water conductivity), while lipid paleothermometers will provide detailed information on past paleoclimate change. The application of aquatic bioindicators and lipid biomarkers on the same sample sets will also provide novel insights on spatiotemporal variations in the aquatic community composition of both lake systems.
The analyses proposed in this project will thus significantly improve our understanding of
- the spatiotemporal variation of the neotropical climate system and its relation to change in the ITCZ as well as
- the response of the lakes’ aquatic ecosystems to climate change.
We will integrate our results with those from cooperation partners in order to place both lake records in a broader regional context by comparison with records from other continental and marine sites. Our results will ultimately allow disentangling the complex climate interactions in the northern Neotropics and thus contribute to the overall goals of the PISDP and MEXIDRILL projects. They will also provide valuable paleoenvironmental information for a region that currently lacks high-resolution paleoclimate datasets over glacial/interglacial time scales.