- (geology) A harder or more resistant rock type overlying a weaker or less resistant rock type.
2009 September 3, James Glanz, “Energy Company Calls Halt to Drilling Project”, in New York Times:
- Last month, federal scientists said that the company had fallen far behind schedule because a huge rig hired to drill down about 12,000 feet, or more than two miles, on federal land had not been able to pierce surface formations called caprock.
- 2013, Philipp Meyer, The Son, Simon & Schuster 2014, p. 424:
- Meanwhile, there were houses going up within gunshot of the caprock.