Spaceborne imaging radar-C (SIR-C) observations of groundwater discharge and wetlands associated with the Chicxulub impact crater, northwestern Yucatan Peninsula, Mexico

Analyses of spaceborne imaging radar-e (SLR-C) data and field data from the northwestern Yucatan Peninsula, Mexico, demonstrate that spaceborne multif requency polarimetric radars are excellent tools for characterizing pattern s of wetland flooding, Seasonal flooding can be detected in most types of f orest and marsh in the radar backscatter magnitude and phase data of both L and C band. Field observations made in the wet and dry seasons concurrent with the space missions and chemical analyses of floodwaters confirm that f looding is the product of discharge from the Yucatan aquifer, which consist s of a fresh-water lens floating on seawater, This discharge controls the d istribution of wetlands. Therefore, vegetation and flooding patterns, mappe d with SIR-C imagery, provide valuable information on the hydrogeology of t he region. Radar-image maps of wetlands and flooding indicate that there are three maj or zones of groundwater discharge that correlate with structures of the bur ied Chicxulub crater--zone 1 with the peak ring, zone 2 with the crater rim , and zone 3 with the exterior ring. Zone 1 has sulfate-poor discharge, unl ike the sulfate-rich discharge in zones 2 and 3, The highest discharge is i n zone 3, where the buried crater is closest to the surface. This groundwat er-discharge pattern can be explained by tidal pumping of fresh water to th e surface through high permeability zones developed in the Tertiary carbona tes overlying crater faults and escarpments.