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Updated: May 25, 2025
After fairly entering upon the Plains, every stream begins to burrow and to wash, growing more and more turbid, until it is lost in 'Big Muddy, the most opaque and sedimentary of all great rivers.
They appear to have been erupted while the sedimentary strata were in a horizontal position, and to have suffered the same dislocations which those strata have subsequently undergone. In the volcanic tuffs of this age are found not only fragments of limestone, shale, flinty slate, and sandstone, but also pieces of coal.
Usually, from the broken interior edge of this slope or sedimentary plateau one descends a bluff or escarpment, and enters the central area of slates, granite, and quartzites, which is carved into high ridges and sharp peaks cut by many narrow and deep valleys and ravines and generally thickly timbered with the common pine of the Rocky Mountains.
This is peculiarly women's work, and some are well known to be better panners than others; they refuse to use salt-water, because, they say, it will not draw out the gold. The whole land is impregnated with the precious metal. I find it richer in sedimentary gold than California was in 1859.
Most of these sedimentary strata are much indurated, and no doubt have been partially metamorphosed: many of them are extraordinarily heavy and compact; others have agate and crystalline carbonate of lime disseminated throughout them. Some of the beds exhibit a singular concretionary arrangement, with the curves determined by the lines of fissure.
These are not made of cemented sedimentary grains, but of interlocking crystals which have crystallized from a molten mass. Examining a piece of granite, the most conspicuous crystals which meet the eye are those of feldspar. They are commonly pink, white, or yellow, and break along smooth cleavage planes which reflect the light like tiny panes of glass.
Some highly porphyritic though coarse-grained masses, evidently of sedimentary origin, and divided into thin layers, differing from each other chiefly in the number of embedded grains of quartz, interested me much from the peculiar manner in which here and there some of the layers terminated in abrupt points, quite unlike those produced by a layer of sediment naturally thinning out, and apparently the result of a subsequent process of metamorphic aggregation.
Rocks of the lowest series. A calcareous sedimentary deposit, with recent shells, altered by the contact of superincumbent lava, its horizontality and extent. Subsequent volcanic eruptions, associated with calcareous matter in an earthy and fibrous form, and often enclosed within the separate cells of the scoriae. Ancient and obliterated orifices of eruption of small size.
On the Babewendigash River seven miles east of Seal Lake is an exposure of highly metamorphosed ancient sedimentary rocks. The outcrop occurs at a height of four hundred feet above the river; and there is a well-marked stratification.
Nor was Virginia's Natural Bridge worn under in a year; nor, in geology, were the eternal Grampians upheaved in an age. And who shall count the cycles that revolved ere earth's interior sedimentary strata were crystalized into stone. Nor Peak of Piko, nor Teneriffe, were chiseled into obelisks in a decade; nor had Mount Athos been turned into Alexander's statue so soon.
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