. The Quarterly journal of the Geological Society of London. avas are extensively developed on thehigh ground between Borrowdale and Thirlmere, but very littleattention has been given to them. The garnet-lavas on the Dock-Tarn plateau greatly resemble the garnet-lava Xo. 10 of the Falcon-Crag Series (p. 87) : and it is quite possible that in them we havethe uppermost members of that series. The next great group of the Eycott Lavas and associatedashes occurs immediately to the south of them, and forms prominentescarpments on both sides of the valley. Garnets do not occur inthese lavas, except i
. The Quarterly journal of the Geological Society of London. avas are extensively developed on thehigh ground between Borrowdale and Thirlmere, but very littleattention has been given to them. The garnet-lavas on the Dock-Tarn plateau greatly resemble the garnet-lava Xo. 10 of the Falcon-Crag Series (p. 87) : and it is quite possible that in them we havethe uppermost members of that series. The next great group of the Eycott Lavas and associatedashes occurs immediately to the south of them, and forms prominentescarpments on both sides of the valley. Garnets do not occur inthese lavas, except in the neighbourhood of intrusive masses suchas the Carrock-Fell rocks, where they are doubtless the product ofcontact-metamorphism. VII. The • Streaky Rocks of the Central Mountain-District. We have next to deal with the group of streaky rocks. A goodidea of the mutual relations of these rocks may be gathered fromthe appended diagrammatic section through Rosthwaite Fell. x. Fig. 2.—Diagrammatic section through Rosthwaite Fell. StonethwaiteChurch : Wood. (//) = garnet-breccia. &=rasli and breccia. gl=garnet-lava. e — Eycott Lavas. s=intrusive sill. st = streaky rocks. gp=garnet-quartz-porphyry. The term streaky has been applied to these rocks from thecharacteristic appearance of the weathered surfaces. These showeither a series of parallel wavy lines, or a multitude of lenticularinclusions with the same orientation. Strictly speaking, rocksshowing this streaky character occur in all parts of the districtand at all geological horizons, but a well-developed band of themis generally found above the Eycott Lavas. This type of structure might arise in various ways. (1) By infiltration of substances along definite planes. This isfrequently noticed, not only in the typical streaky rocks, but inrocks of all geological horizons. The infiltrated substances belongto the following :—quartz, calcite, chlorite, epidote, and are often introduced along the bedding-planes,
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Keywords: ., bookcentury1800, bookdecade1840, booksubjectgeology, bookyear1845
