Blackwater Draw Formation
The Blackwater Draw Formation is a geologic formation in the southern High Plains of eastern New Mexico and Texas. The formation was deposited between 1.8 million and 300,000 years ago, corresponding to the early to middle Pleistocene epoch.
Description
The formation is a very fine to fine red aeolian sandstone that rests on the resistant caprock calcrete of the Ogallala Formation. The formation is highly variable, but has a maximum thickness of. The sediments generally are less coarse to the northeast, indicating that they had their source in the Pecos River valley.The formation is interpreted as loess deposition on a grassland. Deposition was likely episodic, with peak deposition at times of more arid climate and soil formation during moister periods.
The lower part of the formation contains an ash bed of the Toledo eruption in the Jemez Mountains 1.61 million years ago. The formation also contains the 0.62 Ma Lava Creek B ash bed. The upper part of the formation has an infrared stimulated luminescence age of 300 to 350 thousand years, corresponding to the middle Pleistocene epoch.