proceedings: geological society 11 



physiooraiihic contrast with th(> deoply-fiorded coast line of the south- 

 eastern Alaska and Prince William Sound regions on either side of it. 

 This contrast is further accentuated by the much higher relief and re- 

 juvenated recent glaciation of Alpine type, so strongly developE-d in the 

 extensive area dominated by the great mountain masses of St. Elias and 

 Logan, whose heights are about 18,000 and 19,500 feet respectively. 

 The physiographic evidence clearly indicates that the Mount St. Elias 

 province has not passed thru the same episodes of Quaternary develop- 

 ment as have the deeply fiorded provinces which characterize the re- 

 mainder of the Pacific continental shores of Alska to the southeast and 

 southwest of its central part. The geologic evidence in this regard ap- 

 pears to prove that the relief of the Mount St. Elias region has been pro- 

 foundly rejuvenated in late Pleistocene time, and to indicate the strong 

 probability that this deformational uplift has continued thruout Re- 

 cent up to present time. This evidence is in the form of a stratified 

 marine coastwise terrane, from 4000 to 5000 feet thick where well de- 

 veloped, which is quite fossiliferous to the westward in the Yakataga 

 district and in the Chaix Hills, where it is not altered by deformation 

 as it is about Yakutat Bay and eastward. This terrane comprises one 

 or more thick marine shale members that are remarkable from the fact 

 that they contain quantities of ice-borne and glaciated bowlders and 

 cobbles of a great variety of metamorphic rocks in unassorted arrange- 

 ment. Blocks of these 5 to 10 feet in diameter are common in the 

 shale matrix and give a most distinctive lithologic character to the 

 terrane thruout its distribution, Avhich enables it to be recognized where 

 the shales are too much mashed to yield fossil remains. The fossils 

 appear to be of early Pleistocene age. The whole terrane has been 

 uplifted and deformed, so that it now stands at elevations from 3000 to 

 6000 feet above present sea level and forms the foothill mountains 

 along the south flank of the St. Elias range. 



The Cretaceous-Eocene contact in the Atlantic and Gulf Coastal Plain. 

 L. W. Stephenson. The Cretaceous deposits of the Atlantic and Gulf 

 Coastal Plain are separated from the overlying Eocene and younger for- 

 mations by an unconformity of regional extent. Several authors, includ- 

 ing Harris, Vaughan, Hill and Vaughan, and Dall, have stated some of 

 the important facts in regard to the differences exhibited by the faunas 

 on either side of the contact, but the magnitude of these differences has 

 not been sufficiently recognized by geologists. 



During the time represented by the unconformity separating the Cre- 

 taceous and Eocene strata some very important changes took place in 

 the molluscan life of the area. A preliminary stud}' of the mollusks of 

 the upper part of the Cretaceous (Exogyra costata zone) of the eastern 

 Gulf region, where the hiatus is as narrow as it is anywhere in the At- 

 lantic and Gulf Coastal Plain, has showm that of 168 identified species 

 practically all became extinct before the Eocene ]\lidway formation be- 

 gan to be deposited. These species represent 89 genera, of which at 

 least 16 of the more common genera, including one whole order — the 

 Ammonoidea — became extinct. These faunal differences are greater 



