Methods of absolute fossil dating Sex webcam chats
Failing that, the repetition of a certain layered sequence (e.g., a black shale sandwiched between a red sandstone and a white limestone) lends confidence to physical correlation.
Finally, the measurement of a host of rock properties may well be the ultimate key to correlation of separated outcrops.
In dating the past, the primary value of fossils lies within the principle of faunal succession: each interval of geologic history had a unique fauna that associates a given fossiliferous rock with that particular interval.
The basic conceptual tool for correlation by fossils is the index, or guide, fossil.
To this day, fossils are useful as correlation tools to geologists specializing in stratigraphy.
Such features as colour, ripple marks, mud cracks, raindrop imprints, and slump structures are directly observable in the field.
Properties derived from laboratory study include (1) size, shape, surface appearance, and degree of sorting of mineral grains, (2) specific mineral types present and their abundances, (3) elemental composition of the rock as a whole and of individual mineral components, (4) type and abundance of cementing agent, and (5) density, radioactivity, and electrical-magnetic-optical properties of the rock as a whole.
Correlation is, as mentioned earlier, the technique of piecing together the informational content of separated outcrops.
When information derived from two outcrops is integrated, the time interval they represent is probably greater than that of each alone.
In addition, its fossilized population should be sufficiently abundant for discovery to be highly probable.