MARYLAND GEOLOGICAL SURVEY S'.) 



The section exposed at the Muirkirk iron mine, where the best 

 dinosaurian remains thus far obtained from this formation were 

 found, is as follows : 



Section at iron mine. Miiirkirk. Md. 

 Recent: Feet. 



Surface wash, consisting of loam and gravel 10 



Patapsco: 



Sands and gravel, indurated in places by iron oxide and 



containing silicified trunks of conifers and cycads. ... 10 



Massive and stratified, mottled and variegated clays and 

 sandy clays with redeposited nodules of iron carbon- 

 ate and some limonite, pebbly at base, flanking the 



subjacent member 5 to 15 



Arundel: 



Massive blue clay with flakes and nodules of iron car- 

 bonate and containing bones and teeth of dinosaurs 



at base 20 to 40 



Highly lignitic lens of clay ("charcoal ore") 2 



Tough blue clay containing iron carbonate 15 



Patuxent : 



White sand ; amount exposed 10 



72 to 102 



Paleontologic Character. — The fossil flora of the Arundel forma- 

 tion includes ferns, cycads, conifers, and possibly dicotyledons. By 

 far the most common of these are the conifers, with whose lignitized 

 trunks the clays are, in places, densely packed, forming local beds 

 of lignite. Leaf impressions are also present in the iron ores. 



The animal remains, while nowhere abundant, represent a variety 

 of forms. They include worm or insect borings, pelecypods, gastro- 

 pods, dinosaurs, turtles, and crocodiles. The Dinosauria, of which 

 a number of species have been recognized, greatly predominate. 



Strike, Dip, and Tliichness. — The strike and dip of the Arundel 

 formation are approximately the same as those of the Patuxent. 

 The usual dip is 40 to 50 feet to the mile, but there is a well-marked 

 increase near the 'Tall line," where the average is about 72 feet to 

 the mile. At Washington it is 66 feet to the mile. The maximum 

 thickness of the Arundel is 125 feet or more and the formation thins 

 out and disappears in some areas. 



StratigrapJiic Relations. — The Arundel overlies the Patuxent un- 

 conformably and is overlain unconf<irmably by tlie Patapsco. 



