Bulletin of the Geological Society of America . Minne-sota which, having been sheared into rhombs, was further metamorphosedinto a pseudo-conglomerate containing elongated lenses like pebbles. All such structures are devoid of definite bedding which has anygeneral relationship to the shape of the mass, whereas each boudin is 5 B. N. Beach, John Horne, and others : Geological Structure of the Northwest High-lands of Scotland, 1907. Memoirs of the Geol. Survej^ of Great Britain, p. 67.«Idem, p. 263.^ Idem, p. 504.« C. K. Leith : Structural Geologj, 1913, p. 66. 658 T. T. QUIRKE BOUDIXAGE- AX UXU
Bulletin of the Geological Society of America . Minne-sota which, having been sheared into rhombs, was further metamorphosedinto a pseudo-conglomerate containing elongated lenses like pebbles. All such structures are devoid of definite bedding which has anygeneral relationship to the shape of the mass, whereas each boudin is 5 B. N. Beach, John Horne, and others : Geological Structure of the Northwest High-lands of Scotland, 1907. Memoirs of the Geol. Survej^ of Great Britain, p. 67.«Idem, p. 263.^ Idem, p. 504.« C. K. Leith : Structural Geologj, 1913, p. 66. 658 T. T. QUIRKE BOUDIXAGE- AX UXUSUAL PHEXOMEXOX composed of symmetrical arches, grading from those of a high cun-atiireat the periphery to those of no curvature along the axial plane. Furthermore, the j^hacoidal structures are commonly surrounded bythe envelojDing layers of schistose rock wrapped about them. The boudinsof a bed are side by side, unseparated except by quartz veins; never sepa- r>^^>«* I »-iC-orT\pe>f«^r>t Cor>^pQ,-1* Figure 8.—Boudins rated by the schistose rock above and below them (figure 9). We mustconclude that boudins differ from all other folds and structural must come as a result of some unusual type of a series of boudin beds, we seem to recognize great shorten-ing in the incompetent layers and apparently no shortening along theaxes of the boudin beds. This shortening of the incompetent beds must C3<oo c? ^ <:::7 I ^ Co r-K p^^,r:f
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectgeology, bookyear1890
