Green sandstone is interbedded with thin shale beds, which coat the surface in the north part of the exposure, and conglomerate is seen in the south part. Pebbles in the conglomerate are rounded and consist of several different rock types (grey-brown sandstone, red jasper, greenish-grey chert, white granite).
The rocks were compressed when they were tilted. A rock cleavage can be seen as cracks running down the flat bedding surfaces, which dip southwesterly and face the road. Look on top of the southern-most exposure to see the intersection of cleavage with the bedding plane between sandstone on the outside and conglomerate on the inside; the angle is about 40.
From Twillingate, follow the road for Twillingate North and Crow Head, and continue until just before climbing the last hill to Long Point Lighthouse. (You will want to visit it anyway because the view is spectacular!). Turn left into Sea Breeze Municipal Park, and walk down into Sleepy Cove.
Most of the cliff at the back of the cove is dark-green basalt. Stand back on the beach and observe the rounded shape of pillows about 50 cm across. Pillows show as bulbous shapes in the green exposure in the middle of the beach, and can also be seen in the rocky shelf along the north side of the cove.
In the cliff at the back of the cove, volcanic rock is cut by rusty- and dark-red-weathering, light grey dykes of rhyolite containing glassy quartz crystals and pyrite. Both the lava and rusty dykes are cut by a dark brown-weathering diabase dyke. Along the south side of the cove, the lava has been flattened along a fault and has developed a good cleavage.
The lava is intruded nearby by white Twillingate Granite, which is exposed in several places south of Twillingate, but is not seen here. The granite is known to be about 507 million years old, so the lava must be even older and therefore among the oldest volcanic rocks in central Newfoundland. It was probably erupted from a volcanic island-arc in the Iapetus Ocean (see Plate Tectonics panel).
Note the pieces of old mining equipment collected and preserved in the park. There is a short adit (tunnel) just beyond the cove, and timbers from an early wharf protrude from the beach. The mine produced a small amount of copper between 1908 and 1917.
Drive to Moreton's Harbour, and take the road that circles the east side of the harbour. Turn left off this road onto a gravel road that continues around the harbour, and park where a picket fence encloses two satellite dishes. Walk along the path between the fence and the high rocky hill; it crosses the neck to Little Harbour and follows the shore around to some old fenced fields. Old paths continue around the coast for some distance, and the views are wonderful.
As you enter Little Harbour, note the rough flow texture of the lava on your right, and the smooth, glacially polished and fluted diabase outcrops on your left down by the shore. Beyond the fields on the shore, and best seen at low tide, are pillows, and splattered volcanic ash and lava fragments. The small holes in some of the rocks were once gas bubbles in the molten lava. These features indicate an explosive volcanic environment.
Up behind the field, through an opening in the woods is an old antimony mine that was developed sporadically between 1892 and 1916, producing a total of 140 or so tons of ore. There is a trench leading up the hill, ending in a water-filled shaft of unknown depth. Warning! Be careful when approaching the shaft. The waste pile yields good samples of coarsely crystalline pyrite and silvery stibnite, the mineral that contains antimony.
Newfoundland and Labrador Traveller's Guide to the Geology
Edited by: S. Colman-Sadd and S.A. Scott, 91 pp. + map, 1994