It has involved tracing the related sedimentary rock layer horizontally from the place where the fossil in question was found to a place where it is underlain or overlain (or both) by igneous rock.Igneous rock layers can supposedly be directly dated, so sedimentary layers sandwiched between them are interpreted to have been deposited in between the "ages" assigned to the igneous rocks.
The results have now been published in Geology, the journal of the Geological Society of America.
The lack of rigorous protocols for assigning calibrations based on fossils raises serious questions about the credibility of divergence dating results (e.g., Shaul and Graur 2002; Brochu et al.
2004; Graur and Martin 2004; Hedges and Kumar 2004; Reisz and Müller 2004a, 2004b; Theodor 2004; van Tuinen and Hadly 2004a, 2004b; van Tuinen et al. We do not deny that a posteriori methods are a useful means of evaluating calibrations, but there can be no substitute for a priori assessment of the veracity of paleontological data.
Three geologists have reported what they called the first "successful" direct dating of dinosaur bone.
Will this new radioisotope dating (or radiodating) technique solve the problems that plagued older dating methods?