The Manuels River trail meanders for over 5 kilometers along one of the oldest and stunningly picturesque river valleys in eastern Newfoundland. The main entrance is located adjacent to the visitor's chalet on Route 60, just west of Manuels River bridge. The visitor's chalet is open during the summer months and offers a variety of trail maps, brochures and wildlife pamphlets relating to the Linear Park and it's environment. Visitor's can also find information on local tourism venues such as restaurants and boat tours.
This is an outline of two geological trails leading from the chalet: one upstream from the Manuels River bridge and one downstream. Areas of interest are noted on the map, and are detailed below. More information on the geology exposed along the Manuels River is available in the chalet.
Regular footwear, a camera and binoculars will enable the trail user to enjoy the environmental treasures of the river system. Each trail can be typically walked in about 45 minutes, however, visitors are advised to allow about two hours for each trail if they plan on stopping by all the points of interest on the map, as well as some possible "rock-hopping". Persons touring the Manuels River do so at their own risk.
Manuels River: Upstream Geological Trail
1. Conglomerate (Brigus Formation): A 550 million year old beach rock. An ancient shore line ran through this spot and its beach is now exposed in the waterfall below the bridge. The beach was formed from debris eroded from nearby cliffs made of volcanic rocks and granite (see stops 2 and 3).
2. The Holyrood Granite formed deep below the Earth's surface 620 million years ago. It is now exposed as large outcrops divided by sub-horizontal fractures. Exposures near the campfire site show fresh surfaces of coarse crystalline rock with colorless quartz, pink-orange feldspar, dark green hornblende and black biotite. The granite also contains blocks of pre existing volcanic rock which fell into it from the roof of the volcanic magma chamber.
3. Volcanic rocks (Harbour Main Group) intruded by the younger Holyrood Granite, and baked by it so that they are very hard, close to the contact. The baking makes it difficult to see the structure of the volcanic rocks but, upstream, their fragmentary nature can be seen: most of them are ashes, rather than lavas, deposited mainly in water, after being blown out from explosive volcanoes. Explosive volcanism is characteristic of eruptions of magmas observed in continental mountains such as the Andes.
4. The valley upstream from the trestle is broad and gently rounded, in contrast to the narrow gorge below the visitor's chalet. Here the valley was molded more than 10,000 years ago by a valley glacier draining the Avalon ice cap. Post-glacial river action has removed much of the evidence of glacial erosion on the rock surfaces. Abundant potholes and channels were cut in bedrock by the fast-flowing, debris laden melt water river.
5. The rock exposures here show steep bedding of the volcanic ashes, with their angular volcanic fragments. There are also several 'dykes' of basaltic lava: they fill old fissures that cut up through the layers of ash and fed magma from below to later volcanic eruptions. Here some of the rock surfaces have escaped the effects of recent river erosion and preserve the glacially-smoothed, grooved and streamlined form produced by ice moving downstream.
6. This locality shows further examples of the volcanic ashes of the Harbour Main Group, together with excellent examples of feeder dykes cutting vertically up through them.
7. This locality shows further examples of the volcanic ashes of the Harbour Main Group, together with excellent examples of feeder dykes cutting vertically up through them. The canyon originated from river erosion cutting a channel along the joints in the bedrock of the gently U-shaped valley cross-section that was produced by ice flow.
Manuels River: Downstream Geological Trail
1. Conglomerate (Brigus Formation): a 550 million year old lithified beach rock. An ancient shoreline ran through this spot and is now exposed at the base of the 6 meter thick beach layers by the bridge. The beach deposit was formed from debris eroded from nearby cliffs made of volcanic rock, with some granite. Notice how well rounded the beach rock pebbles and cobbles are, just like those in modern beaches (see stop 7). Conglomerate beds dip at 10° downstream (NNW) and are overlain by poorly exposed, pink, red and green fossiliferous limestone and shale; all of these rocks form the Brigus Formation.
2. Downstream from the hard, weathering-resistant conglomerate, granite and volcanic rocks, the river winds its way through a narrow, steep-sided gorge cut in easily eroded shales. Manganese-rich nodular limestone beds are exposed in the river and mark the base of the overlying Chamberlains Brook Formation. The rock has been dissolving in the water to produce the pitted and cleft rock surface.
3. The flat areas of the river valley (stops 3-5) are formed from alluvium: sediment with a wide range of grain sizes deposited from the river when in flood. Note that the river meanders, and the meander has cut down ('incised') into the soft shale bedrock. The Chamberlains Brook Formation is mainly greenish-grey shale, a fine-grained sediment laid down in an ancient shallow sea. The shales weather quickly and are easily broken along their bedding planes, so that the bedding is easily seen in the cliff sections. Notice that the dip of the beds is consistently downstream, so that, proceeding towards the beach; we are walking across progressively younger rocks, and up the geological succession.
4. The Manuels River Formation is mainly dark grey to black shale. It contains the most fossils, especially trilobites, though it is much more common to find bits of trilobites than whole specimens. Search among the loose debris for specimens. Hammering intact rock for specimens is not permitted. Note that the base of the Formation is marked by an ancient volcanic ash layer, a few centimeters of clayey material that was deposited from the ash of a distant volcanic eruption.
5. "The Flats". The elongate lagoon between here and the beach (stop 7) contains fine-grained, organic-rich muds, presently accumulating under more stagnant conditions.
6. Rusty weathering 'rottenstones' mark the transition to the youngest rock formation in the river section - the Elliot Cove Formation. This is another shale sequence but with sandstone bands increasing in frequency towards the mouth of the river, indicating that coarser sediment was carried into the sea in this area at that time.
7. The mouth of the Manuels River widens to form a lagoon fronted by a barachois beach. The beach was formed by movement of material westward along the shore from the slowly eroding cliffs. These cliffs are almost vertical and made of glacial sediments. Notice the similarity in rock types between the cliffs and the beach. The shape of the beach is continually changing, most rapidly during storms. The barachois beach is cut at the west end by a narrow channel which is usually easily crossed. Sometimes the outlet is closed and the lagoon drains through the beach gravels. Before the headwaters of the Manuels River were diverted, there was a wider, deeper breach of the barachois beach.