New radiocarbon dates from a Holocene aeolianite, Isla Cancun, Quintana Roo, Mexico

This paper reports on nine new radiocarbon dates from marine shells collect ed at various heights within a Holocene aeolianite sequence on Isla Cancun in the Yucatan Peninsula, Mexico. The ages obtained from the shells provide an improved understanding of some of the geomorphological and sedimentolog ical processes operating during the upper mid-Holocene on Isla Cancun. Carb onate sand dunes were accreting at rates in the order of 0.28 cm yr(-1) bet ween about 3570 and 4000 years BP. By around 4000 years BP sea levels were close to present-day shorelines evidenced by the presence of marine shells (SRR-5790) within a small wedge of beach material cut into the Cancun aeoli anite at a height of +1.5 m above present-day sea levels. Cessation of dune growth is known to have occurred before 2500 years BP as shells (SRR-5793a , SRR-5793b, SRR-5794a and SRR-5794b) from a midden deposit overlying the a eolianite provide a minimum age for the end of dune activity. Dune formatio n appears, therefore, to be associated with the end of the postglacial tran sgression in sea level. At least one other sample is thought to be from a m idden and the dates obtained from this site provide information on localize d human occupation in the area during the Holocene between 4082 and 2349 ye ars BP.