98 THE CRYSTALLINE ROCKS OF CECIL COUNTY 



in width striking K 40 °E. South of this locality at the first 

 road to the northeast there are five small dikes striking parallel to 

 the others. About a quarter of a mile south of this and opposite the 

 Episcopal church of Port Deposit, there is a dike ten and a quarter 

 feet wide striking X 25° E and dipping 45° southeast. Close by it 

 is a very small dike. 



There are doubtless others in the town of Port Deposit concealed 

 by the houses which crowd against the granite bluff. 



An eighth of a mile south of the southern end of Port Deposit 

 there is a fresh coarse-grained diabase dike some fifty feet wide. 

 This rock is very unlike the green hornblendic rock of the other 

 dikes and it is thought to be a much more recent intrusive of 

 Triassic age. Its petrography is discussed on page 140. 



Between this dike and the stream known as Happy Valley Branch, 

 one fourth of a mile to the south, there are 13 basic dikes, approxi- 

 mately, 3 ft., 8 ft, 1 ft., 4 ft., 12 ft., 12 ft., 10 ft., 11 ft., 4 ft, 2 ft. 

 6 ft. and 6 ft. wide, respectively. 1 They strike 1ST ± 45° E. 



South of Happy Valley Branch there occur successively a two- 

 foot dike, a four-£oot dike, another two-foot dike, and a dike about 

 30 feet wide, opposite the track-watchman's box. Then follows an 

 intrusion of a fine-grained dark-colored yet quartz-bearing and acid- 

 appearing rock which continues a short distance beyond the creek. 

 On the south bank of the creek this is exposed in an abandoned 

 quarry; while north of the run it is penetrated by two hornblendic 

 dikes. 



The quarry rock shows a southeast dip due to creep. 



Immediately south of this quarry a fine-grained granite is pene- 

 trated by a basic dike (meta-gabbro) three or four feet wide and fol- 

 lowed by 200 feet of meta-gabbro. South of this the acid intrusive 

 (meta-rhyolite) again appears. This formation is here amygdaloidal. 

 Some 200 feet south of the meta-gabbro another dike of that rock 

 appears of the same width. 



1 These and all other estimates of the width of dikes were made by pacing, and are, 

 of course, approximate. 



