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

摘要

Analyses of spaceborne imaging radar-C (SW-C) data and field data from the north-western Yucatan Peninsula, Mexico, demon-strate that spaceborne multifrequency polar-imetric radars are excellent tools for characterizing patterns of wetland flooding. Seasonal flooding can be detected in most types of forest and marsh in the radar back-scatter 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 flooding is the prod-uct of discharge from the Yucatan aquifer, which consists of a fresh-water lens floating on seawater. This discharge controls the dis-tribution of wetlands. Therefore, vegetation and flooding patterns, mapped with Sm-C imagery, provide valuable information on the hydrogeology of the region.Radar-image maps of wetlands and flooding indicate that there are three major zones of groundwater discharge that cor-relate with structures of the buried Chicxu-lub 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 dis-charge, unlike the sulfate-rich discharge in zones 2 and 3. The highest discharge is in zone 3, where the buried crater is closest to the surface. This groundwater-discharge pattern can be explained by tidal pumping of fresh water to the surface through highpermeability zones developed in the Tertia-ry carbonates overlying crater faults and escarpments.