Witte Hi Pt S P Geology

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Unformatted text preview: cial scour, striations, and crescentic marks. Bedrock - Shawangunk Formation, cross-bedding, and joints. OAD N TO MONUMENT park on gravel STOP 1 park 0.0 mile 23 crossbedding Stop 1 freeze and thaw Explanation - The overall streamlined and smoothed rock surface, faint striations, and crescentic marks are products of glacial erosion. The scratches and crescent-shaped marks on the outcrop east of Scenic Drive, show that the ice sheet (Kittatinny Valley lobe) flowed S 70o W. Several angular to subangular boulders of conglomerate, glacially transported from nearby locations, lie on the scoured rock surface. The many-sided pattern outlined by vegetation on the rock surface (fig. 14) follows joints and fractures in the bedrock. These features gradually widen over time by the action of freezing water, and root growth, eventually they fill with rock fragments that form a thin soil. The expansion of ice also breaks the rock apart along bedding surfaces as shown by the upward movement and change in position of some joint blocks (figure 14). 1 foot polygonal outline of joint-block boulder Figure 14. Stop 1: Outcrop of the Shawangunk Formation showing many joints and joint-block boulders. The Shawangunk Formation here consists of thin-to- thick layers of quartzite and conglomerate that slope gently to the southeast, forming the eastern limb of an anticline. Cross-bedding, visible on parts of the outcrop, consists of thin, stacked, and curved layers (fig. 5). The orientation of cross bedding shows the ancient river that laid down these deposits flowed in a northwesterly direction. Excellent examples of cross-beds are exposed on the northwest side of Scenic Drive on the slope just below the road surface. 25 Other Occurrences - Evidence of glacial scour, striations, and cresentic marks are found throughout the park where bedrock is exposed. In some places weathering has roughened the rock surface, obscuring these markings. The effects of such weathering may be seen wherever bedrock is exposed, and cross-bedding can generally be observed at most of the...
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