Last 2000 Year Climate Sediment Record from the Belize Central Shelf Lagoon: A Detailed Archive of Droughts and Floods Linked to the Collapse of the Mayan Civilization and Caribbean Historical Famines
Agar Cetin, Ayca
Droxler, Andre W
Master of Science
In the past several decades, climate change linked to increasing anthropogenic CO2 emission to the atmosphere, has resulted not only in steady global warming but also in extreme climate events. Heat and cold waves, flash floods and droughts, and catastrophic hurricanes, are some of the extreme climate events the Earth has been experiencing. In the future, those events are expected to become common rather than exceptional. Understanding processes linked to extreme climate is becoming more crucial and analyzing extreme climate paleo-records have become more important. This study is focusing on the last 2000 yr precipitation record archived in the mixed carbonate/siliciclastic sediments accumulated in the Belize Central Shelf Lagoon, partially filling the Rhomboid Reef lagoons and English Caye Channel. The Belize climate is described as subtropical, largely 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 couple of centuries just preceding the MCA, corresponding to the Mayan Terminal Classic (TCC) Collapse and the Little Ice Age (LIA). Two submersible vibrocores, BZE-RH-SVC-58 from Elbow Caye Lagoon, and BZE-ECC-SVC-68 from English Caye Channel, were retrieved, among several additional cores, from the Belize Central Shelf Lagoon. Carbonate content values were determined by carbonate bomb and element (Ti, Si, K, Fe, Al, and Sr) counts via X-Ray Fluorescence (XRF) scans. This study is mainly based upon the detailed analyses of two of these cores with well-constrained timeframe, established by accelerator mass spectrometry (AMS) radiocarbon dating of benthic foraminifera, Quinqueloculina. The mixed sediments in these two cores, based upon the variations in the past 2000 years of elements such as Ti and K counts, have recorded the weathering rate variations of the adjacent Maya Mountain, highly influenced by alternating periods of high precipitation and droughts, linked to large climate fluctuations and extreme events. The 800-900 CE century just preceding the MCA, characterized by unusually low Ti and K counts and interpreted to be triggered by low precipitation and resulting in severe droughts in the Yucatan Peninsula, corresponds well with the Mayan Terminal Classic collapse (TCC). High Ti and K counts, although highly variable, during the MCA (CE 900-1350) are interpreted as an unusually warm period characterized by two 100-to-250 years-long intervals of higher precipitation when the number of tropical storms peaked, separated by a century (CE 1000-1100) of severe droughts and low tropical storm frequency coinciding with the collapse of Chichen Itza (CE 1040-1100). During the LIA (CE 1400-1850), Ti and K counts reach minimum values, with extreme minima during two historical drought times and related Caribbean-wide famines in the year CE 1535 and the last third of the 18th century (CE 1765-1800).
Sedimentology: Carbonate Sedimentology; Mixed Carbonate/Siliciclastic Systems; Mayan Civilization