An Investigation of the Use of the Spectrograph for Correlation in Limestone Rock

Abstract

Published in Petroleum Transactions, AIME, Volume 204, 1955, pages 247–250. Basic Problem of Correlation In many areas where carbonate rocks form important parts of the stratigraphic sequence, stratigraphers have experienced varying degrees of difficulty in differentiating and correlating limestone and dolomite units in both surface and subsurface work. With early Paleozoic rocks of the Mid-Continent, insoluble residues yield a remarkable amount of stratigraphic data and relatively good correlations may be carried over broad distances. Unfortunately, neither such information nor electric logs and radioactive logs have been particularly helpful in interpreting the limestone sections of the Permian Basin of West Texas. This is because:the variations in the sections may be very slight;no completely satisfactory method of interpretation has been developed; andthe measurements themselves are not sensitive enough for small variations. Also, such logs are influenced by the fluid content. Paleontology and micro-paleontology remain the ultimate arbiters. As a routine tool, however, paleontological examination is slow and tedious. Chemical analysis may be used, but this, too, is extremely slow. Although rocks are not classified according to chemical composition, there is considerable variation with rock types. Correlation by chemical composition has two advantages, first, the characteristics determined are subject to minimum human error and interpretation, and secondly, the lithologic changes are not masked by fluid content as in the case of electric and radioactive logs. Some fossils concentrate certain elementswhich tentatively might be used to date rock units. Rapid chemical analysis by spectrographic means could be used as an adjunct to other means employed in correlation work, or might, in itself, present a suitable method.