NOV. 4, 1921 proceedings: geological society 44.") 



occupying at least much of central and northern Texas, southern Oklalioma, 

 and southern Arkansas, and for short periods it may have extended eastward 

 across the lower Mississippi Valley and joined the southwest end of the Appa- 

 lachian area. It furnished most of the sediments that formed the clastic rocks 

 of Pennsylvanian age in north-central Texas, and for those of Ordovician, 

 Silurian, Mississippian, and Pennsylvanian age in the Ouachita Mountains 

 and Arkansas Valley of Arkansas and Oklahoma. At times, as during the 

 Devonian period, it had very little relief, but at other times, as during the 

 Ordovician and Silurian periods and the Mississippian and Pennsylvanian 

 epochs, it was mountainous. It was depressed and entirely submerged 

 during Lower Cretaceous time and later depressions carried the sea across 

 it during Upper Cretaceous and Tertiary time, so that its rocks are now 

 covered and entirely concealed by deposits of these ages. The discover}'- 

 of pre-Cambrian schists directly beneath Cretaceous strata at Waco, George- 

 town, Maxwell, San Antonio, and Leon Springs, Texas, suggests that the 

 rocks of this old buried land area were similar to the crystalline rocks now 

 exposed in the Piedmont Plateau of the eastern United States. If so, such 

 rocks underlie the Cretaceous strata over much of Louisiana, eastern Texas, 

 and perhaps adjoining areas to the south and east. Prominent structural 

 features of the Gulf Coastal Plain, including the Preston anticline and Sabine 

 uplift, may mark the location of some of the folds that were produced in the 

 rocks on the old land area but that have undergone further movement since 

 they were buried by Cretaceous and later sediments. 



The results of future deep drilling in the Gulf Coastal Plain and further 

 study of the Paleozoic and older rocks that are exposed around the borders 

 of the Gulf Plain will add greatly to our imperfect knowledge of the old land 

 area considered in this abstract. Laurence LaForge, Secretary. 



354th meeting 



The 354th meeting was held in the lecture room of the Cosmos Club at 

 8 p.m. on Wednesday, January 20, 1921. 



Regular Program 



D. F. Hewett and E. V. Shannon: Orientite, a new silicate of manganese 

 and calcium. A. — Chemical properties (Shannon). B. — Genesis and signifi- 

 cance (Hewett). 



As Mr. Shannon was out of the city the entire paper was presented by Mr. 

 Hewett. - 



Charles Butts: General results of recent work on the Mississippian of the 

 Mississippi and Ohio valleys. 



J. B. Reeside and Harvey Bassler: Phases of the Carboniferous and 

 Triassic of southwestern Utah. 



The geologic section of southwestern Utah includes rocks assigned to the 

 Redwall limestone of Pennsylvanian age, the Supai and Coconino sandstones 

 and Kaibab limestone of Permian age, the Moenkopi formation of Lower 

 Triassic age, the Shinarump conglomerate and Chinle formation of Upper 

 Triassic age. Comparison with the formations of areas to the southeast 

 in Arizona and to the west and north in Nevada and Utah warrant the follow- 

 ing conclusions: The Supai formation, passing from east to west and north- 

 west, loses its red color and its shale members and merges with the Coconino 

 to form a continuous massive yellow sandstone. The Kaibab limestone 

 becomes thicker but has everywhere two cliff-forming limestone members 

 separated by g^^psiferous beds. The red continental deposits of the Moen^ 



