Northampton City

The Twelfth Or Burnt Mill Core

Beneath the railroad bridge over the brook which crosses the railroad a mile above Smiths Ferry the contact of the sandstone dips steeply southeast beneath the postei'ior trap, and this contact can be followed, clearly exposed, along the south side of the brook beneath the road bridge and past the ruined leather mill, and along the south side of the mill pond. The conformable posterior trap bed extends southeast of this line. (See p. 465.) Just north of the brook and below the dam one sees the outcrops of an intrusive dike or plug, which comes up apparently along a transverse fault that can be traced west across the mountain from this point. The trap cuts across the strata of sandstone that underlie the posterior trap bed at every angle, and adjacent to the north end of the dam bakes the sandstone for 6 or 8 feet, so that the line of contact between trap and sandstone is seen with difficxilty.

A long ridge of the trap extends west along the northwest side of the pond, and appears also on its south side, and can be followed thence south for 20 rods. At the water's edge trap and sand are confusedly blended. In the bluff above, just south of the head of the pond, appears a well-marked fault. The posterior trap abuts on the sandstone. It is the continuation of the Mount Tom fault, and the newer trap comes up at the intersection of the two faults. A large part of the trap is fresh, compact, and breaks with sharp splintery fracture; a portion of the surface is crumbly and much weathered. This represents a part of the surface of the old laccolith.

The trap of the plug may be followed down the brook on its north side to the road, and just east of the road several offshoots from it appear on both sides of the brook. On the north is a 4-foot dike, on the south a 4-inch dike at the water's edge and a 1-foot dike a few feet up. The latter continues under the road to the dam. A few rods farther east one comes upon the most southern of two outcrops of trap at the Lyman railroad crossing, which is doubtless the eastern edge of the plug, since it is com- posed of the same type of trap aud contains as inclusions portions of coarsely araygdaloidal trap, derived doubtless from the posterior trap sheet, or the tuff, through which it has been intruded.

The Smiths Ferry Core

Directly opposite the Smiths Ferry station and at the edge of the low ten-ace sands just south of the extensive dog kennels the tuff is interrupted by an area of trap, about 6 rods on a side, which seems to be intruded through the tuif, since it has angular masses of the tuff 6 inches across included in its mass. It does not rise above the level of the tuff, as is usual with the more compact plug trap, and I at first considered it a portion of the surface of the posterior sheet exposed where the tuff had been worn tlirough, but the inclusions of trap are foreign to the posterior sheet and the erosion of the old lake shore-line may have lowered the plug at this point. (See, however, page 474.)

Where the Holyoke Electric Railroad track leaves the main road to go to Forest Park it crosses Roaring Brook. Just south of this crossing is a surface of trap, exposed by the excavations for the road, which is weathered and breaks up into spheres at the surface and rests on the sandstone in the brook just below. This is the south exposure of the posterior trap sheet. Just across the brook the raih'oad cutting exposes a splintery trap of fine grain and perfect freshness, which seems to be the southernmost of the small plugs accompanying the posterior sheet.

The mountain-making forces which folded up the Appalachian chains acted against the mass of the Archean rocks in the Adirondacks, as seen by the great curve which these chains make as they run southward beyond its influence. The outlines of the Connecticut Basin were laid in pre- Devonian time, since the Bernardston Devonian is bordered by shore conglomerates which coincide with the borders of the basin and the later Hmits of the Trias. The sinking of the great block south of the Connecticut shore-line, which broke this curve of the Appalachian chains, prepared the way, perhaps, for the second admission of the waters into this narrow channel, which in shape and position resembled the Bay of Fundy.

The tides of this bay were ou a scale which for a bay of this width have no counterpart at the present time. They passed strongly np the west side and down the east side, and were here reenforced by the prevailing west winds, so that they formed very coarse conglomerates on the east. The currents sweeping up the west side, past shores and over bottoms of coarse and deeply decomposed granites, swept granitic debris far north, over the area of black schists. Those passing south swept argillite and quartzite debris far south along the pegmatite shore-line of the east side, and the pegmatite material south along the tonalite and schist terrane, and only where the bay widened was there in its center an elaboration of quartz sand to form the brownstones. In the narrower parts of the bay the two shore conglomerates meet along a central suture, so to speak, and this ends so abruptly at the north end of the basin as to suggest that it extended much farther north and was perhajDS a strait opening into a larger area to the north.

The network of faults which bounds and intersects this basin permitted the sinking of its bottom, in which movement the block from Amherst to Northfield participated in a much less degree than did the rest. In the great transgression which followed, the waters slowly rose upon the bottom and the slopes of the basin and found a great abundance of material ready for transportation and redistribution, because the rocks had become deeply disintegrated during the long period of emergence which was now brought to a close.

I have examined both shores of the Bay of Fundy as well as the fiords of Norway and Scotland, and in comparison the work done here seems to me to indicate stronger currents, a larger amount of material, more rapid change of level of the sea, and more rapid deposition, than can be found in any modem examples. The sea seems to have risen over the flats and slopes of deeply softened rock more rapidly than it could remove the material, and therefore advanced without forming a fixed and deep-cut coast line. It often moved the softened d^bi'is in such large quantity to its present resting place that it is scarcely sorted or rounded even when quite coarse gravel. Indeed, the study of this Triassic transgression has thrown more light upon the ancient and more widespread Cambrian transgression (Chapter V) than I have gained from the examination of more modern instances.

Summary Of Histoky Op The Triassio Beds

\vlioll\- removed troTU the basin during the deposition ol" beds of so great thickness. At a certain time in the midst of this rapid deposition came the great eruptions, apparently synchronous, of the Deerfiekl and Holyoke beds. The bottom of the bay at this time presented a surface covered in (Hfterent parts by beds of every degree of coarseness along its borders and grading toward the center into finer beds, as is indicated by the character of tlie substratum on vs^hich the trap beds rest.

Along beneath the trap of the Holyoke range from west of Mount Holyoke to beyond Mount Tom much argillaceous limestone is inclosed in the trap at its base, and in Holyoke, at Ashley's pond, the same limestone occurs in the inclusions at the surface of the same trap sheet.

I explain the above structure by the imder-rolling of the surface of the sheet. A limited amoimt of calcareous mud was washed by the strong convection currents onto the submerged surface of the advancing sheet (which was superficially solidified) and blended more or less with this surface, which by the continued advance of the mass became in part underrolled, like the surface of an unrolling carpet, thus protecting the sand below from baking, and bringing the highly vesicular trap loaded with limestone to the base of the bed. A similar structure occurs at the base of the trap sheet east of Greenfield, but not at its surface. This was caused by the frothing up of the muddy bottom into the liquid trap.

It is quite probable that these trap sheets were poured out through fissures - the Holyoke sheet through an east-west fissure passing beneath the line of small volcanic cores a mile south of the main outcrop of the main bed, and continuing as a north-south fissure passing tlii-ough the same series of plugs west of the Connecticut. The focus of most intense and long-continued action was about a mile south of the point where the river cuts through the main ridge and where these fissures intersect. The Deei-field fissure can not be exactly located. It was beneath or east of the present outcrop, because artesian wells at Turners Falls cross the trap sheet just east of this outcrop, and there is no trace of intrusive trap west of the present western bluffs. Its focus was probably just east of Greenfield. These sheets produced no disturbance in the distribution of sediments and almost no tuffs, and the arkose which covers them is often buff and nearly free from iron and lime. .

Mon Xxix 32

sheets, and then a second period of volcanic activity followed. The lava broke out at a point on the fissure through which the older lava had come, and flowed in a broad sheet down the bottom of the valley. The place where the lava came up is preserved in Little Mountain, east of Mount Tom, and the outcrop of the lava sheet extends north and south from here, and has been described as the posterior sheet.

The next episode in the history, following immediately on this outflow of lava, was an explosive eruption of diabase forming the beds of tuff from the Belchertown ponds to Holyoke. The center of eruption seems to have been at the focus mentioned above, not far from Smiths Ferry, since the bombs there are a foot across and decrease in size in both directions. The tuffs produced a marked change in the fucoidaP beds (the Longmeadow sandstone) above, into which they grade, as compared with the older beds beneath the tuff. By shallowing of the water the beds are rendered finer, and they are made deep-red and calcareous from the decomposition of the tuff. These red beds extend south from the lunate band of tuff, but this tuff only accelerated and intensified a process which extended far south beyond its influence, and which had its cause in the width of the basin, its shallowness, and the presence of northward cuiTents along its west side and southward cvirrents along its east side. These cm-rents kept the sides of the basin deeper and made them a seat of coarser sedimentation, and between them was a central area of conflicting and shifting currents - a sort of Sai'gasso Sea, in which the finer fucoidal sandstones were deposited and so frequently exposed by the retreating tides that almost every part shows mud-cracks, rain-drops, tracks, thin films of coal, or some trace of exposure.

The northern or Montague basin reached only this stage, the broad development of the central fucoidal sandstones, and there was no tuff outburst or development of shales. In the wider southern or Springfield basin a central area of still greater quiet developed with the widening of the channel, in which at last marly sediments were retained within the area, marked by numerous salt pseudomorphs, and in wliich a later circulation of the waters has concentrated the lime into bands of concretionary limestone.

' These paragraphs were written when the rodlike markings in the "fucoidal" sandstones were supposed to be plant remains. I now think them to be concretions, as explained under "Plants," p. 395. There may thus be added to the effects of the impregnation with iron the abundant rod-shaped concretions which have been mistaken for plant remains and called "fucoids."

Summary Op History Of The Triassio Beds

The beds coutaiuing' reptile tracks are almost without exception above the great trap sheets, and in most cases not very far above them vertically. Some of the localities situated far to the east have been brought up by faulting. These central exposed mud flats seem to have been caused by shallowing of the waters, which resulted from the flowing of the great sheet out over the bottom.

(1) Deposition upon an inclined plane, especially that between the central shallower portion and the deeper portion on the border. This seems to be the case across Hatfield and Deerfield, on the western side of the basin, where the finer central beds dip slightly west toward the coarser beds near the shore, and across South Hadley, Springfield, and farther south, where the finer central beds have a low dip eastward toward the shore beds. In these cases the beds have been moved but little since their deposition.

(2) A slight excess of sinking on the eastern side or an increment in the strength of the eastern currents, or both, by which the finer central beds were in their eastern portion encroached upon and covered by a broad transgression of the eastern conglomerates, so that all down the east side the fine-grained beds dip normally beneath the coarse.

(3) Later tilting, largely to the east, but bending to the south in the Holyoke range, and generally of the monoclinal type, the important exception being at the mouth of Millers River, where there is a great syncline whose axis pitches sharply a few degrees south of west. By this later monoclinal tilting the covered bed of fucoidal sandstone is brought up several times in the mass of Mount Toby.

A third period of volcanic activity occurred in the southern basin about the time of the close of sedimentation and the final tilting of the sandstones. Nearly a score of volcanoes formed a chain running from the Belchertown ponds first west to the Connecticut River and then south to Holyoke, apparently caused by the reopening of weak points along the great fissures which had supplied the material of the earher sheet. One of these shows indications of having been a laccolith sending out a long fissure-filling in the sandstone. Another is diabase filled with granitic inclusions. The rest are small plugs.

basin, and has here a large component of north-south motion, and thus of east-west strikes. The limit of this severe action is the east-west fault mai-ked by the line of craters just mentioned. Many baryta-lead veins in the sandstone and the crystalline rocks on its borders seem to have been formed at this period.

In his review of the question whether the rocks of the Connecticut Valley were deposited in a separate basin, as has been maintained in the preceding pages, or were connected across western Massachusetts and Connecticut and eastern New York with the New Jersey Triassic, which culminates in the Palisade range. Professor RusselP still maintains the opinion he had advanced in earlier papers. The localities described in the preceding pages where coarse conglomerates and coarse, unworn arkose beds rest on the crystalline rocks along the western border, and the relation of these beds to the great granite areas directly west, make it quite certain that the upper end of the bay in Massachusetts had its western shore- line quite exactly at the present western border of the Triassic beds. These latter are mainly formed from bottom to top of the coarse ddbris of muscovite-granites such as now form their western border, while if they had transgressed but a few miles westward they would have covered entirely all this coarse granite area, and there is no similar area from which the arkose could have been derived farther west, where the shore-line must have been.

The Use Of The Trap As Road Material

It is well known that the trap furnishes the best material for road making, and as the legislature of Massachusetts has wisely entered upon an extensive and carefully arranged scheme looking to the extension of macadamized roads throughout the State those places where the trap is found in large quantity and of good quality and near to railroads will be of economic value. The city of Springfield has for a long time worked a quarry at the point in Westfield where the Boston and Albany Railroad crosses the main or Holyoke trap sheet. Recently (1895) the Massachusetts Stone Crushing Company has established an extensive plant on the south side of the Deerfield River at Cheapside, with a capacity of about 100 tons per diem. The company has spur tracks to the Turners Falls branch of the Canal Railroad and can distribute its product readily by rail fi'om Nortliampton or Greeniield. This work is on the main Deerfield tru}) sheet. The New England Trap Rock Company, of Westfiekl, has opened another laa-ge quarry on the west line of West Springfield, on the Ilolyoke- Westfiekl road, with a spur track to the railroad which connects these towns. It has two large crushers with a capacity of 700 tons per diem, and can deliver the rock on the cars at 65 to 75 cents per ton. A crusher has also been set up at the west foot of Mount Tom, in Easthampton, which supplies this town with road material. It is directly under the most picturesque portion of the palisaded bluff, and although it is at present working in the trap talus, later the operations may seriously mar the north wall of the mountain. The great dike beside the spur track of the quarries of W. N. Flynt & Co., in Monson, has been opened by that company, and will supply material of the very best quality.

The city of Northampton has for several years established its cruslaing works near the north line of the town and at a distance from railroads, and works the Hatfield tonalite or hornblendic granite, which is a partly decomposed rock, more brittle than the trap, and in many ways an inferior rock for road ballast. The city has access beside the road or railroad within its own limits to several better ledges than the one it works now. In 1897 the city of Ware opened a quarry on the Coys Hill dike on the mountain side east of the railroad station. The dike is here 5 rods wide, favorably situated for quanying, and will furnish the best material in inexhaustible quantity.

The other localities where the rock occurs in good quantity and qiiality and convenient of access to the railroad are : Where the Fitchburg Railroad crosses the Deerfield trap sheet, on the north side of the Deerfield River and directly opposite to the present works; along the Connecticut River Railroad below Mount Tom station, especially at the first crossing, and at Delaney's quarry on the north line of Holyoke; at Tatham Cutting, in West Springfield; and finally, all the later volcanic cores marked on the map, and especially the dikes of the trap marked in the crystalline rocks on the east of the Triassic area, furnish a rock more fresh and firm than the trap of the main sheet.

. West of the Triassic no beds of trap are found and the hornblendeschist of Chester or the Becket gneiss will be the best substitute for local use.