Remembering Our Ancestors Through Genealogy

A History of Iron County Michigan by Jack Hill Published in 1955, "A History of Iron County Michgan" gives the history and other interesting facts about this Upper Peninsula county. The book was originally printed in two columns. In order to improve the readability of the pages on a web browser it was converted to single column by combining every two original lines. With this exception the transcription was done without changes or corrections. Chapter 11 - Geology of Iron County

46     HISTORY OF IRON COUNTY, MICHIGAN     Chapter XI   GEOLOGY OF IRON COUNTY      For over forty years before Iron County came into being, the area was the object of extensive geologic studies. As far back as 1841, Dr. Douglas Houghton while engaged in a study of the state boun- dary between Lac Brule and the Montreal River, had opportunity to traverse the district and was thereby enabled to complete a geological section from the mouth of the Montreal to the mouth of the Menominee River.    In his report to the legislature in January 1842, he records the area examined as being highly interesting in its topographical and geological features. In 1846-47 came William A. Burt and his surveying crews who discovered and recorded the outcrops of iron ore and other relative geologic characteristics.    n 1848, the government dispatched geologists C. T. Jackson, J. D. Whitney, J. W. Foster and Dr. A. Randall into the region. Messrs. Whitney and Foster were joined by S. W. Hill who had un- dertaken some of the duties of Dr. Houghon upon the death of the latter and the trio proceeded with their studies of the Marquette Range, extending the work into eastern Iron County especially along the Michigamme River. Dr. Randalls work involved the areas further to the west and he is credited with bringing the Gogebic ores to the attention of the country. Mr. Whitney is well remembered for his outstanding works as State Geologist of Cali- fornia where one of the highest mountains was named in nis honor.    Among others that followed were the geologists T. B. Brooks,   HISTORY OF IRON COUNTY, MICHIGAN     47   F. Leverett, C. Rominger, I. C. Russell and R. C. Allen, former state geologist. In more recent years, crews under the supervision of C. O. Swanson 1932, C. E. Dutton 1945, and H. L. Tames 1947 to the present time.      Many valuable contributions to the work have also been made by Mr. Stephen Royce of Crystal Falls, the geologists of the local mining companies and the Geogolcal Survey Division of the State of Michigan.    The very complex nature of the geologic features of the county, have been and still continue to be a challenge. The heavy mantle of glacial debris, especially in the western part where till depth reaches 400 feet, quite effectively conceals the preglacial rock sur- faces upon which determinations are ordinarily based.    Exploratory work has been confined mainly to the areas of known iron ore formations and little is known of the strata underlying the volcanic greenstones that encompass the Iron River, Crystal Falls, Alpha and Amasa mining districts. The comparatively younger age of the local iron bearing strata than other regional iron ore formations, its complex folding and the presence of intrusive and extrusive volcanics have all combined to make the study of the local Pre-Cambrian rocks extremely arduous.    As reconstructed to date however, the geologic column of the county consists of the Laurentian granites of Archean Age, the Saunders quartzites, dolomites and shales and their probable equivalents of Lower Huronian time, the Hemlock and Mastodon greenstones of Middle Huronian; the Michigamme slates which form the bedrock series of the local iron formations being of Upper Huronian age, the questionable Keweenawan volcancis of unde- termined Keweenawan or Upper Huronian time, the sandstones of the Cambrian and the remant limestones which are mainly of Ordovician time.    That we may more readily understand the origin of the local geological formations, let us briefly review the earliest continental history of North America. Through studies of the continental geology, it has been determined that the first land to be elevated above the waters of the seas was the vast area of central Canada known as the Canadian Shield.    This is believed to have transpired during earliest Archean time. The rock formation of the Shield was mainly of volcanic origin, highly metamorphic and is known as the Keewatin. With the possible exception of the controversial Coutchiching sedimentary rocks of recent discovery in the Rainy Lake region of Ontario, the Keewatin is the oldest rock formation on the continent.    Upon this Keewatin base some 40,000 feet of igneous and sedi- mentary rocks have been laid in the local area through alternating epochs of land uplift which was ordinarily combined with volcanic activity, long periods of erosion and sedimentation and subsequent submergence.    Two definite periods of land uplift and mountain making have been determined in relation to the local rocks. The first disturbance occupied a large part of the Middle Archean age when the Laurentian uplands extending east to the Gulf of St. Laurence and including the vast area of Labrador were lifted above the seas.    This was a period of great volcanic activity when the ex- tensive Laurentian granitics were intruded into and upon the basic Keewatin rocks. It is believed that at the close of this period the Laurentian equalled in height the Rocky Mountains of the pre- sent day.