ARUNDEL FORMATION 195 



more or less sandy. They often carry logs of coniferous lignite, usually 

 lying in horizontal position and strongly compressed. Occasionally 

 large upright stumps are encountered, standing where they grew, with 

 the roots and trunks more or less replaced by iron carbonate and iron 

 sulphide. The logs of lignite are not infrequently massed together 

 into a well denned bed of considerable thickness and extent, which has 

 been locally utilized by the miners for fuel (plate 25). The foliaceous 

 remains and seeds of plants are apt to be found in the vicinity of these 

 beds. At times the clay is charged with comminuted lignite, when it is 

 known as " charcoal clay.' 1 This clay is apt to be rich in "charcoal 

 ore," and at a few points bears osseous remains. It was one of these 

 beds, situated near Muirkirk, Maryland, from which Mr Hatcher obtained 

 for the late Professor Marsh a considerable collection of dinosaurian and 

 other remains. In the upper portions of the formation, which have 

 long been exposed to atmospheric influences, the carbonate ores have 

 sometimes to a considerable depth changed to hydrous oxides of iron, 

 known to the miners as "brown" or "red" ore. Under these condi- 

 tions the originally drab-colored clays have suffered a like chemical 

 change, resulting in red or variegated clays. When the Arundel clays 

 at other levels contain scant vegetable matter, they are frequently highly 

 colored, and if they contain ore it is of the red or brown variety and 

 sometimes a red ocher (" Venetian red "). Red ocher generally occurs 

 near the base or summit of the formation, but at times within the main 

 body of the same. To the landward the formation is often arenaceous, 

 and at times exhibits considerable lenses of sand. 



^Organic remains. — The flora of the Arundel formation includes algae, 

 fungi, lycopods, ferns, cycads (apparently fronds only), many conifers 

 and monocotyledons, as well as a considerable showing of dicotyledons, 

 which, though not specially advanced in type, are far beyond those of 

 the Patuxent formation in grade as well as in variety and numbers. 

 There is therefore a well defined contrast between the dicotyledonous ele- 

 ments of these two formations. 



The fauna of the Arundel formation includes worms (or possibly the 

 borings of insect larvae), lamellibranchs, gastropods, fishes, and reptiles, 

 including turtles and dinosauria, remains of the latter being compara- 

 tively common. Bones of cetaceans are alleged to have been found by 

 Tyson, but the report lacks confirmation. Notwithstanding this, the 

 faunal contrasts between the Arundel and Patuxent are seen to be 

 strongly marked. 



Strike, dip, and thickness. — The strike and direction of dip of the Arundel 

 formation within the zone of its occurrence are practically identical with 

 those of the Patuxent formation. 



XXIX— Bull. Geol. Soc. Am., Vol. 13, 1901 



