Bulletin of the Geological Society of America . anner ofmountain-making as to time and place, and are therefore valuable guidehorizons in unraveling the genesis of a decken mountain system. The con-ditions of sedimentation become increasingly complicated with the evolutionof decken. Out of the rubbish of the decken, strata may form on the sea-floor, which in turn are made into decken. The decken movement is from the inner parts of the geosyncline outward,and it advances continually against the rigid plates of the foreland. Thisalso may be included more or less in the powerful movement and draw
Bulletin of the Geological Society of America . anner ofmountain-making as to time and place, and are therefore valuable guidehorizons in unraveling the genesis of a decken mountain system. The con-ditions of sedimentation become increasingly complicated with the evolutionof decken. Out of the rubbish of the decken, strata may form on the sea-floor, which in turn are made into decken. The decken movement is from the inner parts of the geosyncline outward,and it advances continually against the rigid plates of the foreland. Thisalso may be included more or less in the powerful movement and drawn intothe whirlpool of the orogenic field of force. The more the geosyncline iscompressed, the more will it rise as mountains and become terra follows the phase of arching up the decken ranges into lofty mountain,chains. Steinmann has designated this phase as positive to Heim, this phase is followed by a further one, which is char-acterized by the sinking of the mountain chain, immersed like an iceberg ViGVRK 8.—Schaita des Grahen-HorsitypusKobers figure 1, page 51. the sea, as a consequence of its enormous size and weight. This is a sort ofclosing phase in the making of a young decken mountain system. Perhapsthis may be designated as the negative phase. The positive phase is char-acterized by the division of the mountain system into blocks (Schollen). Themountain chains rising out of the sea remain for a long time near sealevel,and undergo there widespread planation, as is seen in the East Alps (pre-Miocene, pre-glacial surfaces). The Alps at that time had not the characterof a high mountain system. They were rather a hill country or mountains ofmoderate height. Only positive mountain-making forced the Alps to greatheights. It is said that these movements are epeirogenic. As a matter of fact,they are expressed chiefly in fractures and flexures, in arching of the old landsurface. But these epeirogenic movements, as was stated previou
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