ABSTRACT

Carbonate dune rocks (eolianites) that line many mid to low-latitude coasts may contain indicators of the late Quaternary subtropical climate, because these limestones are deposited and lithified under the influence of the subaerial regime. Many eolianite belts are indicative of the early stage of glacio-eustatic lowering of sea level, which is accompanied by increased aridity. However, coastal eolianites may be deposited either during arid low stands of sea level or during humid high stands of sea level.

In late Pleistocene and again in Holocene time, carbonate dune rocks accumulated along the same part of the northeastern coast of the Yucatan Peninsula, Mexico. These eolianites have undergone different histories of cementation and mineralogical inversion. It is suggested that a difference in climate during and shortly after deposition of the Quaternary eolianites was the overriding factor in producing dissimilar diagenetic changes in the Yucatan dune rocks of different ages.

Appreciable retention of metastable Mg calcite and aragonite in the upper Pleistocene eolianites suggests that early diagenesis was controlled by limited rainfall, which resulted in a slow rate of percolation of vadose water. The more humid Holocene climate has produced eolianites which are losing aragonite and Mg calcite at a relatively fast rate.

Finely crystalline cement, microcrystalline root-hair tufa, needle-fiber cement, and caliche deposits in the older eolianites are indicators of early vadose diagenesis in an arid or semiarid late Pleistocene climate, in which intense evapotranspiration induced calcite precipitation. Generally coarser sparry calcite cement in the younger eolianites was produced under the influence of the more humid and moderate Holocene climate.