THE CRETACEOUS PERIOD 



753 



General movements. In the closing stages of the period, the 

 sea which had lapped over the Coastal Plains of the Atlantic and 

 the Gulf of Mexico was withdrawn toward the abysmal basin. At 

 about the same time, the Appalachian Mountains, which had been 

 reduced to a peneplain by this time, were bowed up again. This 

 later movement was chiefly vertical, while the Permian deformation 

 was primarily horizontal, a folding movement. 



In the western interior, the sea had abandoned the area of the 

 Great Plains, and other tracts in the mountains farther west, be- 

 fore the close of the Laramie. It is probable that most of the 

 Cordilleran region was elevated bodily at this time, though not to 



Fig. 508. Section showing the position of the Cretaceous beds in western 

 Oregon. Mg, meta-gabbro of unknown age; sp, serpentine; as, am- 

 phibolite schist; Jr, Jurassic (?); Km (Myrtle formation), Cretaceous, 

 and Kmw, lentils of limestone in the Myrtle formation; Eu (Umpqua 

 formation), Eocene; Ed, Eocene diabase. (Diller, Roseburg, Ore., 

 folio, U. S. Geo. Surv.) 



Fig. 509. Section showing position of Cretaceous beds at. one point in the 

 vicinity of Livingston, Montana. & = Archean; -, Cambrian (Galla- 

 tin and Flathead formations); D, Devonian (Jefferson formation); 

 C, Carboniferous (Quadrant and Madison formations); /, Jurassic 

 (Ellis formation); Kd, Dakota formation; Kc, Colorado series; Km, 

 Montana series, and Kl, Laramie series; bbr, basic igneous rock, and 

 apt, acidic rock. Length of section about 11 miles. (Livingston, 

 Mont., folio, U. S. Geol. Surv.) 



a great height. Without further details, it may be said that 

 enough is known to make it probable that a large part of the con- 

 tinent was affected by deformative movements of a gentle sort. 



Orogenic movements. The growth of mountains locally by 

 folding was probably in progress in the closing stages of the Creta- 

 ceous period from Alaska on the north to Cape Horn on the south, 

 more than a quarter of the circumference of the earth. Folding 



