Xii CONTENTS. 



Chapter XIII. — The Triassic eruptive rocks — Continued. Page. 

 The bedded and contemporaneous eruptives — Continued. 

 The Deerfleld sheet — Continued. 



Contact on the sandstone below, etc — Continued. 

 Petrographical description — Continued. 



Glass-breccia 433 



Anygdaloidal sandstone 435 



Contact material 436 



Lithophysoe 436 



Chemical discussion 436 



Origin of tlie glass and minerals 437 



Contact of the sandstone upon tlie diabase 439 



Fall River fault 439 



The unity of the sheet 440 



Petrographical description 441 



Parageuesis of secondary minerals 444 



The Holyoke sheet 446 



The faults at Mount Tom and southward 449 



General characteristics of the sheet 451 



Normal contacts of diabase on sandstone 452 



Contacts of uuderrolled diabase inclusions of limestone 452 



Petrographical description 453 



Normal contact of the sandstone on the diabase 455 



Contacts of sandstone on diabase which is kneaded full of limestone and shale 456 



Section of trap filled with limestone fragments on the Westtield-Holyokc Railroad . . 456 



Magmatic difterentiation 459 



Origin of the clay and marl deposits 459 



On the uuderroUing of the solidified surface of the trap 460 



Petrographical description of the normal diabase 461 



Chemical composition of the trap 463 



The upper or posterior sheet and its feeding dikes 464 



The great widening of the trap area and the feeding throat beneath 467 



SiUs intruded in the sandstones below the posterior sheet 469 



Delaney's quarry, near the north line of Holyoke 470 



The Roaring Brook fault and the disappearance of the posterior sheet 473 



The blending of the tufl' with the surface of the posterior bed 474 



A tufi'aceous sandstone containing white trap 474 



The posterior dike across Hampden County 475 



The Talcot t sheet 476 



The tuif and tuifaceons agglomerates 476 



The UeerBeld l>ed 476 



The Gran liy bed 476 



The isolated mass of tuff north of the seventh core 479 



Source of the material of the tuff bed 480 



A hollow bomb from Delaney's quarry, Northampton 480 



Petrograjihical description 480 



The newer series of cores and short dikes 481 



1 



