678 PROCEEDINGS OF THE BALTIMORE MEETING 



already given to support this view, we have also the increasing or decreasing 

 prominence of the strata of different periods as we cross the Neuse River 

 valley. North of the Neuse river the Eocene is wanting for a considerable 

 distance, and when it appears in the northern part of Virginia presents a dis- 

 tinctive glauconitic character and extends northward through Maryland, but 

 with a thickness scarcely exceeding 200 feet. South of the Neuse river the 

 Eocene appears, presenting a calcareous phase, and gradually increases in 

 importance until in the Gulf region, particularly in Alabama, it becomes of 

 very great importance. The Miocene formations throughout Maryland, Vir- 

 ginia, and the northern part of North Carolina are especially well developed 

 and have received much attention. South of the Neuse river, in North Caro- 

 lina, they are still represented, but with greatly decreased importance, and 

 throughout the Gulf region the Miocene is distinctly subordinate in thickness 

 and areal extent to the Eocene. The Pliocene period also shows similar char- 

 acteristics. As already stated, the marine Pliocene, so far as we know, is 

 entirely absent north of the Neuse river, but southward it appears in isolated 

 patches in North Carolina, and also is represented southward to the gulf and 

 becomes increasingly more important. 



"Hattekas Axis" 



Earlier workers have discussed the so-called "Hatteras axis" separating the 

 Coastal plain in two portions, though the evidence was somewhat meager. 

 The study of the Tertiary strata of North Carolina furnishes data for drawing 

 this line of separation between the North and South Atlantic Coastal plains 

 much more definitely. In general this line is followed by the Neuse river, as 

 stated on a previous page. This line may be considered as an axis, in that 

 denudation and sedimentation during each of the Tertiary periods were unlike 

 on the two sides, and in most instances denudation south of the axis seems to 

 have occurred at approximately the same time that deposition was taking 

 place to the northward, and vice versa. The faunal studies which are now 

 being carried on are expected to throw additional light on this problem. 



Then was presented orally by the senior author 



CHARACTER AND STRUCTURAL RELATIONS OF THE LIMESTONES OF THE 

 PIEDMONT IN MARYLAND AND VIRGINIA 



BY EDWARD B. MATHEWS AND J. S. GBASTY 



[Abstract] 



A study of the small bodies of crystalline limestones and marbles found along 

 the western edge of the Piedmont from Pennsylvania to North Carolina shows 

 that their occurrences mark the tops of tightly compressed anticlines. The 

 deposits on either side are usually metamorphosed volcanics — flows and tuffs — 

 which in the normal section lie far beneath the limestones. The areal distribu- 

 tion, contacts, and structural lines point to a strong overthrust fault of wide 

 extent 



This paper was discussed by J. Barrell. 



