A variety of other sources provide data on past climates, but most of these are relatively minor compared to ice cores and ocean sediments. Devil’s Hole is an open fault zone adjacent to a major ground-water discharge area in south-central Nevada. This open fissure is lined with a dense calcite that has precipitated continuously from calcite-supersaturated groundwater over a time span of more than the past 500,000 years. The isotopic variations in atmospheric precipitation are believed to reflect changes in average winter-spring land surface temperature, the season during which recharge is most likely to have occurred. Dating was accomplished radiometrically with high precision. The results conflicted with those of ice cores and ocean sediments. This led to some rather bitter controversies. Speleothems are secondary mineral deposits in caves which may span tens of thousands of years. Other sources of data include rock magnetism, pollen records, coral terraces, mountain glaciers and Red Sea sediments.