A Coastal Yucatan Sinkhole Records Intense Hurricane Events

Brown, A.L.; Reinhardt, E.G.; van Hengstum, P.J., and Pilarczyk, J.E., 2014. A coastal Yucatan sinkhole records intense hurricane events. The potential of tropical sinkholes as archives for historical hurricane events has yet to be fully explored. This study uses high-resolution (1-cm interval) particle-size analysis to examine two sediment push cores from Laguna Chumkop, located on the Yucatan Peninsula, Mexico. Core CKC1 (62 cm) was collected from the base of a deep sinkhole located in Laguna Chumkop at 79.9 m (msl), while the second core, CKC2 (93 cm), was collected from the shallow peripheral margin at 6.4 m (msl). Two coarse fining upward sequences (12 to 35 cm, 46 to 62 cm) in CKC1 had mean particle sizes of approximately 1.5 (medium sand) with intervening intervals of lime mud (<4 ). Measured 137Cs activity in the bulk sediment (n 15) and radiocarbon dating (n 3) using bomb-carbon calibration determined that the lower coarse unit was deposited in the 1960s (after September 1957 AD), and the upper unit between January 1985 and August 1991 AD. Hurricane Gilbert struck the Yucatan on 15 September 1988 as a category 5 storm, generating the upper fining upward sequence. Hurricane Beulah (category 23) likely generated the lower unit when it struck on 18 September 1967. CKC2 revealed small textural changes, alternating between silt and sand-sized particles and radiocarbon ages dated to 6.7 to 7.1 ka. The rapid accumulation of sediment in the shallow lagoon likely occurred with rising sea level flooding the area at approximately 6.8 ka. Based on the sedimentary results, a depositional model is proposed for inland sinkholes, explaining the formation of hurricane deposits through density and debris flows along the shallow margin.