These are former sedimentary and volcanic strata that have been transformed by heat and pressure, possibly during the intense upheavals when the dry land was formed on Day 3 of Creation Week.Among these metamorphosed volcanic strata are amphibolites, belonging to the Brahma Schist.Metamorphic rocks are not always easy to date using radio-isotopes.Results obtained usually signify the "date" of the metamorphism, but they may also yield the "age" of the original volcanic (or sedimentary) rock.These were originally basalt lava flows several meters to tens of meters thick.In some outcrops pillow structures have been preserved, testimony to the basalt lavas having originally erupted and flowed under water onto the Creation Week ocean floor.The "age" or "date" is calculated from the amount of the daughter isotope produced by radioactive decay of the parent isotope.In Grand Canyon, the "date" of metamorphism of the basalt lavas to form these Brahma amphibolites has been determined as 1690-1710 Ma (million years ago), based on U-Pb dating of minerals in the overlying Vishnu Schist and underlying Rama Schist that formed during the metamorphism.
Obviously, if radioisotope decay was accelerated, say during the Genesis Flood, then the radioisotope decay "clocks" could never be relied upon to "date" rocks as many millions of years old.
To the contrary, the rocks could still only be a few thousand years old.
The radioisotope methods, long touted as irrefutably dating the earth's rocks as countless millions of years old, have repeatedly failed to provide reliable and meaningful absolute ages for Grand Canyon rock layers.
The collections at Rancho La Brea are still at the core of late Pleistocene North American research today.
Staff, Research Associates, professional paleontologists, and graduate students frequent the collections throughout the year.