MEXIDRILL, THE BASIN OF MEXICO DRILLING PROJECT: UPDATES AND PROGRESS

In early 2016 the MexiDrill field expedition recovered over 1000 m of sediment drill cores from the Basin of Mexico at the Lake Chalco drilling site on the outskirts of Mexico City. Four holes were drilled, reaching a maximum depth of 520 m. The upper ~300 m of the sequence is composed of lacustrine mud alternating with discrete tephra layers, underlain by a basaltic volcaniclastic sequence to approximately 512 m depth. Below the volcaniclastic unit, the deepest hole penetrated a hydrothermally-altered colluvial breccia unit. Triple core recovery with offset core intervals in the lacustrine unit provided core overlap that allowed us create a composite sequence for continuous paleoenvironmental reconstructions for the past >500 kyr. The Chalco record is thus among the longest continuous climate records from tropical North America, and it will help to understand millennial scale variability, the climate during past interglacials and the relationships between rates of climate change, ecosystem response, and biodiversity. These MexiDrill cores also provide a long record of volcanic events, allowing determination of the magnitude and frequency relationships of the area’s explosive volcanic eruptions and improving risk assessment for future activity. These anticipated results are directly relevant to the >25 million people living in the Mexico City region, an area that is subject to a wide range of volcanic hazards and that is projected to become increasingly dry in the coming decades and centuries.