257) and partially based on Williams, Turner, and Gilbert (p. Sandstones that contain less than 10% clay matrix are called arenites (note that the Spanish word for sand is arena). Quartz wackes have predominantly quartz surrounded by a mud or clay matrix.
These can be subdivided based on the percentages of Quartz, Feldspar, and unstable lithic fragments (fragments of preexisting rock). In a feldspathic wacke, feldspar is more abundant, and in a lithic wacke, lithic fragments are more abundant.
In addition to being too young, the K–Ca ages are also highly variable, ranging in age from Silurian to Permian.
The K–Ca system is potentially useful as a low-temperature thermochronometer with closure temperatures Reliable dating of sedimentary rocks is important to the calibration of the geologic time scale and to the timing and cyclicity of depositional events.The following response, initially presented in three parts, is not as detailed as I would like to make it.This stems from the fact that I am currently enmeshed in research and also because I want to get this on Schimmrich's net before it closes down.The range of younger glauconite K–Ca ages is similar to the distribution of available apatite fission track ages for the Llano basement.K–Ca ages are interpreted as thermochronologic data reflecting partial retention of Ca in thermally fluctuating basin conditions.