Part 7

Pl. 8. Trap ridges, near and far.

The columns on Titan's Pier lie across the river from the Northampton-Holyoke road in the narrow gap at Mount Tom station. The basalt flow is inclined 15° southeastward, and the columns stand perpendicular to the surface--hence they are inclined with respect to the water level. Doubtless the devil docked his boat on the gently inclined rock surface of the cove on the downstream side of the pier.

Titan's Piazza is situated east of the road to the Mount Holyoke House. It is an extremely narrow ledge backed by a stockade of columns. The front of the piazza is literally strewn with wreckage from the house, for a slope over 100 feet high is covered with angular pieces of basalt which have fallen from the back wall. The lower ends of the columns break off into shallow hexagonal saucers with the concave sides up. Many have slid down the slope, to the delight of the birds that bathe in them. Higher up the cliff, the saucers become deeper, and towards the top the columns scale on into bullet shaped masses.

Westfield Marble Quarry

Anyone who drives westward on the Jacob's Ladder route from Springfield passes first through the open, rolling country of the Connecticut Lowland. Hills are in sight, but they seem remote until he leaves Westfield, and there the upland rises before him like a 900-foot wall. The road uses the gateway cut in the wall by the Westfield River, and the drive westward towards the headwaters of the river is one of the best known scenic attractions in western Massachusetts. But a greater treat awaits the person who will venture southward on the road along the Little Westfield River. It follows the canyon brink about 500 feet above the stream. Near the hilltop, a side road turns north to the Westfield Marble quarry, which provides a vantage point overlooking fifty miles of country to the north, east and south.

The Westfield River meanders eastward across the flat lowland. Its banks are terraced, each level cut in the lake beds or in the delta which the river built in glacial Lake Springfield. The scalloped margins of the terraces are the extremities of meander loops which developed when the river was not entrenched as deeply in the unconsolidated deposits as it is today.

The flatness of the twenty-mile strip of lowland is impressive, for it ends only at the Wilbraham Mountains, eight miles east of Springfield. Beneath the lowland lie soft and gently dipping sandstones and sandy shales, capped by a thin veneer of lake clays and river sands. The shales are the youngest Triassic beds remaining in the region, and they outcrop between Thompsonville and Windsor Locks, Connecticut. Younger shales above them succumbed to Tertiary erosion.

The Wilbraham Mountains are granite and gneiss which formed the roots of the ancient Triassic ranges. Their present accordant summits are a tribute to the leveling activities which running water performed on a quiescent land, whereas the deep V-shaped valleys incised in the level summits record uplift and quickened erosion in Tertiary and glacial time. Indeed, the lowland itself owes its existence to the power of rejuvenated streams working on non-resisting rocks.

The Holyoke and Mount Tom ranges are visible far to the northeast, and a chain of low hills connects Tom with the ridges between Hartford and Avon, Connecticut. These linear hills surmount the lowland because they are made of basaltic lava, which is better able to resist the rain and the weather than the sandstones and shales above and below. Scattered flat-topped hills between Southwick and Granby are sheets of basalt-like rock called diabase, which was inserted between a sandstone roof and floor. Nowhere can one better appreciate the highly individualized imprint which each geological element has made upon the central New England landscape.

The Old Lead Mines

The colonial period in our nation's history was characterized by an ignorance of its mineral wealth and a dependence upon Europe for most raw materials, especially essential metals. During the War for Independence, European supplies were cut off, and Yankee ingenuity had to make the most of local deposits of metallic minerals. It was not long before mines were in operation on several lead veins in the Connecticut Valley, yielding a supply of lead for the duration of the war. But the mines were small, and most of them were soon abandoned, remaining only as historical sites, or as collecting localities for the mineralogist. Five of these old deposits are still accessible: four lie west of the valley at Loudville, West Farms, Hatfield, and Williamsburg; an important one is situated east of the valley at Leverett. All are very similar in geology and mineralogy, yet each possesses its own individuality.

The Loudville vein was worked intermittently as late as 1861. It follows a fault fracture between walls of gneiss, but at the southwest end of the vein some of the minerals are disseminated through the Triassic sandstone and conglomerate. This feature indicates that the sediments were unconsolidated at the time of mineralization. The fault zone resembles many analogous fissures which give forth hot mineral-bearing waters in the Basin and Range region of Nevada, for the charged waters have impregnated the sands which cover the fissures.

The Loudville vein contains numerous well-formed crystals. Barite was the first mineral deposited, and it is readily recognized as a heavy, easily scratched substance with one set of cleavage planes at right angles to two others. Gray metallic galena and resinous cleavable sphalerite or zinc blende occupy much of the space between the barite plates. Hard hexagonal crystals or white masses of quartz coat and even replace the barite plates. Spike-shaped crystals of calcite and siderite line many of the cavities and coat the quartz. A patient search will be rewarded by the finding of other minerals, including pyrite, chalcopyrite, pyromorphite, wulfenite, malachite and azurite.

The old shaft has been closed and the tunnel at the river level has collapsed, hence the only exposures are in the open cuts. The most interesting is the one at the south end, where the barite plates are disseminated through the sandstone.

Another series of pits can be found easily about 100 yards west of the road to West Farms and about one mile north of the Loudville deposit. The vein attains a maximum width of three feet between walls of gneiss, and it occupies a fault fracture which seems to be continuous with the Loudville zone. Included in the vein are many fragments of a black phyllite resembling the Leyden argillite, as well as pieces of gneiss. The minerals are identical with those found in the Loudville deposit, but the specimens of quartz, galena and sphalerite are more spectacular.

The Hatfield vein occurs in a rock of igneous origin, known as the Williamsburg granodiorite. It is exposed at the west edge of the valley, about 200 feet from Federal Highway 5, at the northern limit of the settlement called West Hatfield. The workings are full of water, and the very thorough mining activities carried on by mineral collectors and by Smith College and Amherst classes have reduced the waste pile to negligible proportions. Early collections and records reveal that the vein is essentially like those farther south. At Hatfield, West Farms and Loudville the fractures do not parallel the systems in the Triassic sediments and lavas.

A galena-bearing vein outcrops near the Whately-Williamsburg town line at the north end of the Northampton reservoir. Leyden argillite forms the walls of a fault fissure. Barite is absent from this vein, but fine quartz, pyrite and chalcopyrite coat the walls. Coarse comb quartz encrusts the older minerals, together with breccia fragments and cubes of galena. The vein is remote from the valley and differs in mineralogy and texture from those within the valley. Other deposits like it have been found in the nearby hills.

1. Only barite in these veins 2. Best mineral locality 3. Best place to see fault 4. Slickensides and tension cracks show direction of movement on fracture making opening for vein 5. Best place to see quartz replacing barite along crush zones in vein

The Leverett lead vein is the most interesting of the group because it is so well exposed that the nature of the vein system is admirably displayed. The deposit lies in a series of overlapping, nearly vertical fault fissures in gneiss. Slickensides and tension cracks on the walls of the veins indicate that the movement was nearly horizontal from northeast to southwest. Wherever a fracture begins to narrow and close up, another begins to widen and become conspicuous a few feet to the northwest of it. Several different fissures appear along the length of the mineral zone.

The same minerals are present as are found in the Loudville, West Farms and Hatfield veins, but barite is more abundant and quartz less so. Numerous cavities lined with crystals indicate that the vein formed close to the earth's surface. Apparently the minerals entered fractures situated near the front of a range that bordered the basin in Triassic time. A fault zone so located would lack the great thickness of rock that once lay over the gneiss and would be free from any appreciable overburden of outwash within the Triassic basins.

The Dinosaur Tracks Near Holyoke

People still write from as far away as the Rocky Mountains to ask if the dinosaur footprints beside the Connecticut River are still in place. They are. Anyone may see them in that triangular area between the Boston and Maine tracks and Federal Highway 5 about one-quarter mile north of the entrance to Mountain Park. Marvelous as their preservation from the assaults of man may seem, it is even more amazing that they should have been preserved in rock at all.

The footprint beds are shaly sandstones about thirty feet above the Granby tuff--a bed of volcanic ash formed in late Triassic time. They are inclined 15° towards the river, and even the higher strata which form the "Riffles" are footprint-bearing. The sandstones are ripple-marked, and they contain worm trails and a few casts of salt crystals. Some beds have impressions of reeds. The footprints range from half an inch to ten inches in length, and the stride of the larger animals was from five to eight feet. Most of the tracks are headed up the present slope, but a few are going in the opposite direction.

The sandstones were laid down as almost horizontal beds of sand which were occasionally covered and rippled by moving but rather shallow water. Rushes and reeds, which have left stray impressions in the rock, grew seasonally in the shallow waters, but in between the periodic rains and floods, the local climate seems to have been quite dry--and probably very warm. The sedimentary record suggests a lowland much like some of the tropical valleys in the West Indies, lying in the rain shadow of adjacent mountains.

The large tracks invariably have impressions of three toes. Even a careful search does not disclose the double tracks which would have been left by quadrupeds, and for years the bipedal impressions were called bird tracks. But birds have spurs which leave a mark behind the middle toe; these animals had no spurs and were not birds, but reptiles. Gregarious animals generally follow a leader, and only an occasional individual strays from the beaten path. The tracks at Holyoke suggest that these Triassic reptiles traveled in small herds.

The modern silts of the Connecticut Valley are not a good medium for the preservation of tracks because they lack coherence, and they drift with the wind as soon as they dry. Clays in a region of seasonal aridity are different. They are baked hard in the hot sun, and the water contains dissolved mineral matter which crystallizes in the clay and sand as the water evaporates, cementing the particles into a rock-like aggregate. Impressions in this sort of mud are preserved. The Connecticut Valley had the right kind of sediment and climate in Triassic time; impressions of salt crystals can be found in the shales where the tracks are clearest, not only in this locality but elsewhere in the neighborhood of Holyoke and West Springfield. These precipitated salts helped hold the clays together until they were effectively buried, and afterwards a firmer cement was deposited around the particles.

Footprints are known near South Hadley, at Turners Falls, at Gill, and along the highway to the French King Bridge; but they do not portray the character of the animals, their habits and the mode of preservation of their tracks as effectively as the tracks north of Holyoke. Certainly no occurrence of tracks in situ is as accessible, and no geological exhibit in New England has received so many visitors.

Fossil Fishing