2 - GEOLOGY

Summary

INTRODUCTION

Information regarding the geology of Iran is somewhat uneven. Many have contributed to make up the present sum of knowledge. Pioneers of the 1850s, like Loftus, and others of the late nineteenth century, like Blandford and Stahl, have been followed in this century by a number of geologists grouped around such leaders as De Böckh, Lees, and Gansser; while the few lone individuals have included Schröder, Rivière, and Furon. Until 1938 the geological surveys were done from the ground entirely but after that year aerial photographs became available as an additional tool. A few efforts to sink bore-holes were made during the nineteenth century, but “modern” drilling commenced only in the first decade of the twentieth century. This and geophysics, which has been evolving since the 1920s, have provided further aids to the interpretation of the geology. Part of the geological research carried out in Iran can be conveniently illustrated by maps, whose preparation is facilitated by the excellent exposures found in most of Iran and particularly in the mountains. Good reconnaissance maps are now available for much of the country, and there are also sheets in some detail designed to meet particular economic or academic needs.

Much stratigraphical detail has accumulated from special regions, but parts of Iran have barely been reconnoitred. As in most countries, the old formations are sparingly exposed and where they do crop out are liable to have experienced rough treatment, such as metamorphism, dyke-intrusion, and destructive jointing, which the younger beds may have escaped. Faulting and folding have also introduced uncertainties. The younger beds are widely distributed, and in undisturbed areas gradual facies variation can be followed. On the other hand, some young formations appear to have suffered widespread metamorphism around certain intrusions, and the parts subject to tight local folding have proved perplexing unless intermediate sections providing critical transitions happen to have been studied.