New Mexico Geological Society Annual Spring Meeting — Abstracts

Natural ground water discharge occurs from a series of cenotes, or sinkhole lakes, along the east side of the Pecos River floodplain at Bottomless Lakes State Park, Chaves Co., NM. The lakes are fed by submarine spring discharge from the underlying San Andres artesian aquifer, which has caused subsurface dissolution and collapse of overlying gypsum and mudstones of the Artesia Group. The lakes are unique in that they occur in a semi-desert setting, where annual evaporation rates exceed mean annual precipitation by a factor of seven or more. An increase in spring discharge at Lea Lake in recent years reflects the combined effects of rising water levels in the artesian aquifer and enhanced spring flow due to mass wasting processes along the steep eastern margin of the lake. Although the Bottomless Lakes cenotes fonned prior to European settlement in New Mexico, catastrophic solution collapse and sinkhole fonnation remain active processes along this portion of the lower Pecos.