41. The basement rocks have experienced metamorphism related to their original depth in the Earth's Variscan and Tertiary age. 42. Modern geologists have documented four major deformational events that basement rocks and occurred around 1, 700 million years ago. 43. The crater is believed to be caused by an impact event due to basement rocks found outside the crater. 44. Much of the western two-thirds of the country consists of the Pliocene Pleistocene volcanics deposited on Precambrian basement rocks . 45. All of the productive units are of Miocene age, and the underlying basement rocks date to the Jurassic period. 46. I put ( an electric ) pickup on my violin, played in basement rock bands and got into improvising. 47. Compressive forces detached sedimentary units across western Utah and Nevada from their Precambrian basement rocks and pushed them eastward. 48. Many monoclines ( a type of gentle upward fault in the Precambrian basement rocks hidden well below any exposed formations. 49. Hidden below a more than 6000 metre thick Mesozoic cover are probably more than 6000 m of Paleozoic basement rocks . 50. The Tonto Group units were deposited on an ancient erosion surface ( angular unconformity ) on the Vishnu Basement Rocks .
