410 iV T . H. Darton — Magothy Formation of Maryland. 



The Magothy Formation. 



Distribution. — As is shown on the accompanying map the 

 Magothy formation extends from the Delaware line to a point 

 just southwest of Bowie, where it disappears in the overlap of 

 the Severn onto the Potomac formation. I have not traced 

 its eastward continuation through Delaware but the formation 

 undoubtedly extends some distance at least, probably included 

 in the sand marls described by Chester as the base of the 

 glauconitic series. * 



Bast of Chesapeake Bay the Magothy formation extends in 

 a nearly straight line from near Chesapeake City to below 

 Worten's Point and outcrops below the Columbia deposits in 

 the face of river and bay bluffs and in stream cuts. Its range 

 of altitude is not great except in the outlying area of Maulden 

 Mountain where it lies in greater part above one hundred feet 

 above tide. Its dip is to the east-southeast at from 20 to 30 

 feet per mile. 



West of the bay the formation begins a short ways below 

 Bodkin Point at the mouth of the Patapsco, and crosses the roll- 

 ing country and three or four intersecting valleys, south-west- 

 ward to its termination. Its inclination of from 30 to 40 feet 

 per mile carries it far westward up the long slopes of the ridges 

 in irregular sheets and outliers but it descends below the Severn 

 formation at tide level eastward along a line essentially con- 

 tinuous with its course on the eastern shore of the bay. The 

 altitudes attained in the ridges westward are 130 feet on the 

 neck between the Magothy and Patapsco Rivers, 240 feet in a 

 far western outlier near Severn Station on the Magotby- 

 Severn divide, 250 feet east of Odenton, 160 feet between 

 the forks of the Patuxent and 190 feet on the ridge just east 

 of Bow T ie. 



General Features. — The Magothy formation consists mainly 

 of white and buff sands wdth local beds of brown sandstone, 

 and limonitic streakings both in plates and discoloration s. 

 South westward it becomes gravelly for some distance and some 

 portions are locally lithified into loose conglomerates or harder, 

 more or less pebbly, brown sandstones. The ferrugination 

 which gives rise to the brown sandstones is by no means con- 

 fined in this region to the Magothy formation for brown sand- 

 stone and limonitic masses and crusts are scattered locally in 

 the Potomac, Pamunkey and Columbia formations and also 

 but more rarely in the Severn, Chesapeake and Lafayette 

 formations. The sands of the Magothy formation are mode- 

 rately coarse and at some localities they are very coarse. They 

 consist of quartz grains which vary in shape from rounded to 

 subangular with a greater or less admixture of angular grains. 



