DETAILED 2000 YEAR CLIMATE RECORD IN THE MIXED CARBONATE/SILICICLASTIC BELIZE CENTRAL SHELF LAGOON

Although the mixed carbonate/siliciclastic Belize Central Shelf Lagoon (CSL) is not anoxic, it has been used as a potential analogue for the depositional sedimentary environment of the Eagle Ford Shales. Moreover, mixed shelfal sediment also can be excellent archives for the weathering rates in the adjacent hinterland, influenced by precipitation variability, and therefore climate fluctuations.

The main purpose of this research program focuses on the late Holocene mixed sediment partially filling the Rhomboid Reef lagoons (RRL), English Caye Channel (ECC), and the central shelf lagoon. The Belize climate is described as subtropical, influenced by the seasonal migration of the Intertropical Convergence Zone (ITCZ), triggering alternating winter dry and summer wet seasons. In the late Holocene, the ITZC has been reported to have reached higher latitudes during the Medieval Climate Anomaly (MCA) producing high precipitation on the Yucatan Peninsula, contrasting with periods when the ITCZ remained in low latitudes, generating years of low precipitation and even dramatic droughts, as during the Little Ice Age (LIA) and the couple of centuries just preceding the MCA, corresponding to the Mayan Terminal Classic Collapse (TCC).

9 vibro- and 2 gravity cores were retrieved from the Belize CSL. Their timeframe was established by dating, via radiocarbon, intact non-transported bivalves and benthic foraminifera (Quinqueloculina) fossils. Carbonate content values were determined by carbonate bomb and element (Ti, Si, K, Fe, Al, and Sr) counts via XRF scans. Values of carbonate content in the cores from the RRL vary from 84 to 90%, in the cores from ECC from 44 to 75%, and in the cores from the central shelf lagoon from 44 to 64%. As expected, the highest strontium counts (3600-4000) are observed in cores located in the RRL surrounded by continuous reefal rims.

3 of the 9 cores, with well-constrained radiocarbon timeframes, display detailed climatic records for the last 2000 yrs. The 800-950 A.D. interval preceding the MCA is characterized by a sudden decrease in Ti, Si, and K counts, related to a severe drought and overall low sedimentation rates which correspond rather well with the TCC. Systematic high element counts are observed during the MWP (950-1300 A.D.), while during the LIA (1300-1800 A.D.) these counts reach minimum values.