Calcite crystal fiber vein in limestone, Monument Uplift, Utah


I collected this in ~1999 while working with Alex Bump along the  Comb Ridge monocline on the east flank of the Monument Uplift.  It was another beautiful day working on the Colorado Plateau, and we were positioned inside the steeply dipping limb of the giant Comb Ridge monocline.  Surrounded by such BIG structure, it was quite something to see the delicacy of small-scale tectonic adjustments within individual outcrops, and to be reminded again of how each lithology may have its own way (its own mechanisms) for accommodating and expressing deformation.  In this case we are seeing semi-brittle faulting.

Age & Formation
Lithographic limestone from the Jurassic Carmel Formation, ~165 Ma. Time of vein-filling of fracture/fault not known, but probably in the latest Cretaceous/earliest Tertiary (~65 Ma) or mid-Tertiary (~25 Ma).