. Report of the geological exploration of the fortieth parallel . nt themountain slopes of a pre-Cambrian ridge. The range within the limits of our Exploration, as shown upon Atlas-Map III., is naturally divided into three portions: First, the great semicir-cular sweep of strata around the Archaean and granitic centre of LonePeak. Second, a similar mass curving around the Archaean body whichoccupies the summit of the range from a few miles north of Salt LakeCity to the region of Ogden. Third, the northward projection of thestrata from that point, which is depressed beneath the horizontal Terti
. Report of the geological exploration of the fortieth parallel . nt themountain slopes of a pre-Cambrian ridge. The range within the limits of our Exploration, as shown upon Atlas-Map III., is naturally divided into three portions: First, the great semicir-cular sweep of strata around the Archaean and granitic centre of LonePeak. Second, a similar mass curving around the Archaean body whichoccupies the summit of the range from a few miles north of Salt LakeCity to the region of Ogden. Third, the northward projection of thestrata from that point, which is depressed beneath the horizontal Tertiariesin latitude 41° 45. The dip of all these exposures is to the east, north,and south—never to the west. An immense axial fault has cleft down thecentre of the range from north to south, and the western half has been de-pressed and its rocks buried beneath the Pliocene and Quaternary exposuresof Salt Lake Valley. The range therefore represents half of a great foldwhich lias suffered much longitudinal compression and been faulted down .rallel PLATE VIII F P. < E- P < cc N < ; < PALEOZOIC EXPOSURES. 155 the axis. The interesting orographic details of this structure will be foundfully described in Chapter III., of Volume II., and their essential featuresagain treated in Chapter VIII. of this volume. A full description of the Palaeozoic outcrops of this range wouldoccupy more space than has been allotted to the whole of this volume, andI must content myself with a sufficient number of the great characteristicexposures to constitute a proof of their correlation into a generahzed sec-tion. In order that these sections may be better understood, I oflPer herea mere outlined statement of the chief beds, in the order of their super-position. Beginning at the top, we have: 1. Pernio-Carboniferous, composed partly of calcareous, partly of ^®®=- argillaceous, and partly of arenaceous materials, the wholegiving evidence of shallow-water origin, and characterizedfrom b
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