Geomorphologic Analysis of Forillon National Park, Quebec, Canada Murray A

Document generated on 09/29/2021 7:26 p.m. Atlantic Geology Geomorphologic Analysis of Forillon National Park, Quebec, Canada Murray A. Roed Volume 15, Number 2-3, Fall 1979 URI: https://id.erudit.org/iderudit/ageo15_2_3rep03 See table of contents Publisher(s) Maritime Sediments Editorial Board ISSN 0843-5561 (print) 1718-7885 (digital) Explore this journal Cite this article Roed, M. A. (1979). Geomorphologic Analysis of Forillon National Park, Quebec, Canada. Atlantic Geology, 15(2-3), 47–54. All rights reserved © Maritime Sediments, 1979 This document is protected by copyright law. Use of the services of Érudit (including reproduction) is subject to its terms and conditions, which can be viewed online. https://apropos.erudit.org/en/users/policy-on-use/ This article is disseminated and preserved by Érudit. Érudit is a non-profit inter-university consortium of the Université de Montréal, Université Laval, and the Université du Québec à Montréal. Its mission is to promote and disseminate research. https://www.erudit.org/en/ 47 GEOMORPHOLOGIC ANALYSIS OF FORILLON NATIONAL PARK, QUEBEC, CANADA MURRAY A. ROED Geo-analysis Limited, 1725 St. Laurent Blvd., Ottawa, Ontario, CANADA K1G 3V4 INTRODUCTION interval = 50 ft.). In addition, low level oblique colour transparencies of the sea cliffs of the This paper summarizes the geomorphology of peninsula were examined and all geomorphic features Forillon National Park, Quebec, The work is pri- were identified on the film and then located and marily a photo geologic interpretation in conjunction shown in Figure 1. with a literature review conducted during the All relevant data from a review of principal period March 20 to April 20, 1978. scientific publications were also transferred onto A geomorphic map at a scale of 1:100 000 Figure 1, Especially that compiled by Cumming (1976). accompanies the paper and for the first time presents Colour slides on file with Parks Canada were a comprehensive inventory of principal geomorphic examined. These depict principally post-glacial features of the park classified according to age geomorphic features. and process. Also, the mapping has developed new information with regard to glacial and pre-glacial Previous Work geomorphic features. Despite a great many past studies in the park few have concentrated on the Geological work in the park has been reviewed geomorphology and, therefore, little quantitative by Cumming (1976) . Prest (in Douglas 1970), data exists. McGerrigle (1952) and Maldague (1973) are the main It is important to point out that this work references for glacial geology. The majority of has been completed without the benefit of a field work in Forillon Park has concentrated on the check. A considerable amount of field work would stratigraphy and paleontology of the Paleozoic be necessary to map the park adequately and to bedrock whereas surprisingly little specific data establish the ground truth on which it is based. are available on the surficial geology, considerably Therefore, this paper is considered to be prelimin- less on the geomorphology, and nothing on ary. engineering geology. Physiographic Setting GEOMORPHIC PROCESSES Forillon National Park consists- of an area of The geomorphic processes that have been at about 240 km2, located at the eastern tip of the work in Forillon National Park can be divided into Gaspe Peninsula, Quebec. It is bounded on the those that occurred in pre-glacial time, those that south by Gaspe Bay, on the north by the St. occurred in glacial time, and those that are post- Lawrence River and on the west by Highway 197 and glacial or occurring now and immediately following Renard River. Topography is generally mountainous glacial times. Each of these time divisions is with elevations ranging from sealevel to 550 m. discussed below, and the features in the park that The area is dominated by a southerly trending represent examples of the processes in each of these part of the Schishock range of the Appalachian time intervals are shown in Figure 1. Mountain system. The mountains comprise two dis- tinct groups of rocks: one is a sequence of sand- Post-glacial stone and limestone of Devonian age that dips uni-' formly to the southwest and forms a resistant spine Features formed by post-glacial processes in- or hogback adjacent to Gaspe Bay, and the other clude present coastal erosion and sedimentation, is a series of highly folded less resistant schists alluvial erosion and sedimentation, colluvium and phyllites of Ordovician-Cambrian age that formation, and development of organic terrain. occupies the northeastern part of the park and un- Features formed in immediately post-glacial time conformably underlies the Devonian rocks. The (an alpine glacial phase) are included in glacial northern boundary of the Appalachian Mountains occurs processes. The possibility of permafrost pockets just to the northeast of the park along the St. exists in upland localities, especially in organic Lawrence River marked by Logan's Line. depressions as inferred from McGerrigle (1952, p. In general, the park is well drained due to its 48) in Cummings (1976, p. 254). high topographic relief and the occurrence of near- surface bedrock and a thin mantle of dominantly Coastal Processes granular soil. Most streams including two larger rivers, the Griffon Cove and Renard Rivers, drain The best examples of landforms formed by to the St. Lawrence River, whereas a series of coastal processes include the formation of a tombola- smaller but higher gradient streams drain to Gaspe spit landform at Baie de Penouille and the sea Bay. cliffs of Forillon Peninsula. Development of Baie de Penouille and the Method of Study associated peninsula is an example of tombola formation by the interaction of coastal processes Geomorphic features of Forillon Park have been and alluvial processes. The interpretation pre- mapped using aerial photographs at a scale of 1: sented here is that the tombola formed by deposition 50 000 taken in 1976. This information was trans- of alluvium into the sea (a delta) at the mouth of ferred directly onto a planimetric base of the area Ruisseau Ascah which must have interfered with west- with the aid of a topographic overlay (contour ward longshore drift along Gaspe Bay and caused a MARITIME SEDIMENTS, Vol. 15, Nos. 2 and 3, August-December, 1979, pp. ^7-54 48 spit to be formed. Eventually the spit grew and kind. Specific setbacks from scarp edges may be merged with the deltaic deposits to form a tombola. required for construction of camp sites adjacent The abrupt straight edge on the western part of the to alluvial terrain. tombola may be explained by the unique interaction of tidal currents and river currents from both Dart- Organic Deposition mouth and York Rivers. This interpretation means that the lagoon is slowly filling due to deltaic Organic terrain is not common in the park but sedimentation and overwash along the spit and, occurs in poorly drained depressions in lowland and in time, the tombola will merge with the shore com- upland localities. The principal process of form- pletely to form a broad sand bar. ation is the anaerobic breakdown of vegetation and Sea cliffs are the most striking geomorphic gradual accumulation of sphagnum moss. Samples of coastal feature in the area. The coast between Cap peat at the base of such terrain may yield material Gaspe and Cap Rosier with cliffs up to 200m high is that could be dated and thus provide a. minimum age a high wave-energy zone with a wind fetch of 300 km of deglaciation of the area. (Owen and Harper 1972). Three basic erosional pro- All organic and alluvial terrain should be cesses occur along the coast and include under- avoided for development due to poor drainage, poor cutting by wave erosion, subsequent rock fall and foundation conditions and possible erosion. landslide due to removal of support, and rock fall as a result of frost action. Direct abrasion of Colluvial Processes the shoreline by shifting and shorefast ice is one aspect of ice erosion, and the other is that material Rockfalls and landslides due to undercutting falls onto the ice and is removed by the ice during are manifested by large and small piles of broken break-up. The shorefast ice also acts as a defense angular rock that occur in colluvial deposits along against wave action. slopes and at the base of steep rock faces. Talus Wave erosion results in the formation of sea fans occur where frost action is an on-going pro- caves and pot holes, differential erosional features, cess. Colluvium formed by solid creep is common shoreline retreat, and the sedimentation of beach in the park. sand the gravel. The beach deposits along Forillon Peninsula are almost entirely due to reworking of Landslides talus deposits and, to a very minor degree, to head- land erosion of the small resistant outcropts such Minor rockslides are present along the sea as Cap Bon Ami. cliff of Forillon Peninsula, and can be expected Along the eastern coast, shoreline erosion is anywhere the ocean is actively undercutting the not to be underestimated and should receive con- cliff. siderably more quantitative study. Specifically, A possible large deep seated landslide may it "should be possible to determine the rate of have created the terrace on which the Cap Bon Ami erosion "using instruments for monitoring present facilities are located. A detailed investigation erosion, by the examination and study of air photos of this possibility has not been conducted to the and maps, by the analysis of offshore morphology writer's knowledge. Certain features of this land- (marine geomorphology), and by interviewing long- form, none of which is conclusive, suggest a land- time residents of the area. slide origin. First, it is an anomolous landform in Erosion by waves and frost along Gaspe Bay is em otherwise high steep bedrock shoreline.

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