. Bulletin of the Department of Geology. Geology. 1917] Moody: Breccias of the Mariposa Formation 387 Part of the diabase is certainly irruptive, however; dikes of a por- phyritic facies clearly intrude the Calaveras limestone shown in sec- tion EF, and other dikes may be seen crossing the Mariposa contact where exposed by the excavations for the Bear River canal. Numerous diabase dikes are included wholly within the Mariposa formation. Serpentine, in dikes and masses, cuts the Mariposa and older formations. Its occurrence in dikes along contacts of both igneous and sedimentary rocks suggests
. Bulletin of the Department of Geology. Geology. 1917] Moody: Breccias of the Mariposa Formation 387 Part of the diabase is certainly irruptive, however; dikes of a por- phyritic facies clearly intrude the Calaveras limestone shown in sec- tion EF, and other dikes may be seen crossing the Mariposa contact where exposed by the excavations for the Bear River canal. Numerous diabase dikes are included wholly within the Mariposa formation. Serpentine, in dikes and masses, cuts the Mariposa and older formations. Its occurrence in dikes along contacts of both igneous and sedimentary rocks suggests that it represents a late phase of intrusion. The planes of schistosity of the Calaveras were, however, seen to pass obliquely across a serpentine dike near the Bear River,. AM. Amphibolite; DB, Diabase; SP, Serpentine; GB, Gabbro. Fig. 1. Generalized columnar section though other areas are wholly unsheared; the possibility of two periods of serpentine intrusion is thus indicated. The elliptical area of gabbro, northwest of Colfax, is a coarse granitic rock of basic aspect, which has invaded the Mariposa, the older diabase and the Calaveras. The mapping suggests that this gabbro was brought into its present position by anticlinal folding, but its irruptive nature is indicated by chilled margins and discordance with the strike of the sedimentary beds. The only other rocks in the vicinity of Colfax are the volcanic tuffs and river gravels of the superjacent series, which appear as outliers on the higher eminences of the 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 University of California, Berkeley. Dept. of Geology. Berkeley : The University Press
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