How paleontologists estimate geologic time through radiometric dating Lookingforfreesitetowebcamtowebcamwithwomen
A thermal event that will leave most radioactive clocks relatively unaffected may have a drastic effect on the helium radioactive clock.
When they break and engulf chunks of sedimentary rocks, it's called stoping. The original rock layers around subsidence areas are called wall rocks and the layers that xenoliths came from are called parent rocks.
According to the law of superposition, as long as an area remains undeformed by outside forces, the deeper you go down through the layers of rock, the older they are.
So, if you know the ages of the layers in the parent and wall rocks, you can calculate the age of the layers in your subsided area or xenolith by matching them.
Sedimentary rocks form from soil and silt carried and deposited by moving water.
Over time, the accumulated deposits compress and harden.