Quaternary Palm Fossils from Coastal Florida, USA: A 2016 Hurricane as a Tool for Paleontology Research

In October 2016, Hurricane Matthew passed along the east coast of Florida, USA. Intense coastal erosion by storm waves made sandy beaches to reveal a multitude of trunk molds of ancient palm trees that once flourished along what is now the intertidal zone. A combination of coastal engineering efforts and natural processes caused the ancient palms to be reburied by beach sand. Fortunately, two retired geologists quickly responded after the hurricane ended, conducting a detailed investigation of the fossil palms. The trunk molds occur in two adjacent parallel zones that have an overall length of 1.4 km. The seaward-facing zone contains trunk molds where wood has been mineralized by calcite, enclosed within a coquinoid outer zone. The molds are associated with areas of gray coquina. In contrast, the landward-facing zone is characterized by trunk molds that contain mummified wood tissues within a weakly cemented sand matrix. These molds have thin coquina outer boundaries, but they occur within loose beach sand. Geological and botanical characteristics suggest a Holocene age for the ancient palm groves; their occurrence and demise are associated with small-scale regression/transgression cycles. A 14C radiocarbon age of 160 yrs BP for one of the younger cycles suggests the possibility that the landward- facing coastal palm growth was related to tidal changes that were related to the temperature fluctuations of the Little Ice Age (1300–1850).