Late-Holocene Environmental History in the Northeastern Caribbean: Multi-proxy Evidence From Two Small Lakes on the Southern Slope of the Cordillera Central, Dominican Republic

This dissertation presents multi-proxy evidence of paleoenvironmental change preserved in sediment records recovered from two lakes on the southern (Caribbean) slope of the Cordillera Central in the Dominican Republic: Laguna Castilla (18^o47'51" N, 70^o52'33" W, 976 m) and Laguna de Salvador (18^o47'45" N, 70^o53'13" W, 990 m).

The Castilla and Salvador sediment records contain evidence of prehistoric forest clearance and agriculture, including abundant maize pollen, dating back to around A.D. 1060. These pollen grains constitute the earliest evidence of maize agriculture from the interior of Hispaniola, and represent some of the earliest evidence of maize agriculture from the Caribbean as a whole. This finding is significant geographically because it suggests that prehistoric humans that occupied the interior of the island may have relied more on maize than their coastal counterparts.

The abundance of maize pollen in the sediment records, and the high rates of sediment accumulation in the lakes, provide an ideal situation for testing the sensitivity of stable carbon isotope signatures of total organic carbon (δ¹³C_TOC) in lake sediments to variations in the spatial scale or intensity of agricultural activities. Close correspondence between δ¹³C_TOC values and maize pollen concentrations in the Castilla sediment record indicates a close relationship between δ¹³C_TOC signatures and the scale of maize cultivation. Correlations between δ¹³C_TOC signatures and mineral influx also highlight the sensitivity of the δ¹³C_TOC record to variations in allochthonous carbon delivery.

More detailed multi-proxy analyses of the Castilla and Salvador sediment records indicate extreme shifts in hydrology, vegetation, and disturbance regimes in response to climate change and human activity in the watersheds over the last ~3000 cal yr B.P. Close correspondence between the hydrological history of Castilla, Salvador, and other circum-Caribbean study sites indicates that much of the hydrologic variability was associated with variations in the mean boreal summer position of the Intertropical Convergence Zone. Human occupation of the Castilla and Salvador watersheds appears to be closely linked to severe drought events and may indicate larger scale cultural responses to severe precipitation variability on the island of Hispaniola.