. Annals of the New York Academy of Sciences. Science. y. Fig, 4. Section No. I, taken along Bushkill Creek. (9 = Post-Algonkian dolo- mites'; 7"= Tremolite beds presumably altered form of C which =1 calcite-dolomite beds ; Gn = pre-Cambrian gneiss. pyroxene occur so abundantly in these beds as locally to replace all or nearly all the carbonates, so that locally they become al- tered to a nearly pure tremolite rock with streaks or patches of phlogopite or pyroxene or containing at time considerable amounts of the original carbonates. These tremolite beds are confined to the southeastern s
. Annals of the New York Academy of Sciences. Science. y. Fig, 4. Section No. I, taken along Bushkill Creek. (9 = Post-Algonkian dolo- mites'; 7"= Tremolite beds presumably altered form of C which =1 calcite-dolomite beds ; Gn = pre-Cambrian gneiss. pyroxene occur so abundantly in these beds as locally to replace all or nearly all the carbonates, so that locally they become al- tered to a nearly pure tremolite rock with streaks or patches of phlogopite or pyroxene or containing at time considerable amounts of the original carbonates. These tremolite beds are confined to the southeastern slope of Chestnut Hill, and at the southwestern extremity of the ridge lie for the most part at or near the contact of the post-Algonkian dolomites on the pre- Cambrian gneisses. Here, as can be seen in the cut made by the Bushkill Creek, all three, viz., the dolomites, the tremolite beds and the pre-Cambrian gneisses dip uniformly to the south- east and are apparently conformable. (See Fig. 4.) The explanation of the occurrence here of beds of tremolite would seem to be simple. In the first place the post-Algonkian dolomites are more or less silicious as the following analysis shows : SiO, =3-52 Fe and Al = CaCO^ =53-40 MgCOj = Immediately below them come the beds of carbonates which are usually highly dolomitic and may have contained original silica. Underlying these in turn are the pre-Cambrian gneisses which with their included quartz lenses and granite intrusions could furnish free quartz enough by infiltration to transform the beds. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original New York Academy of Sciences. New York, New York Academy of Sciences
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