| Monteregian Hills | |
|---|---|
 Three of the central Monteregian Hills (from left:Mont Saint-Hilaire,Mont Rougemont andMont Yamaska) viewed from space | |
| Highest point | |
| Peak | Mont Megantic |
| Elevation | 1,110 m (3,640 ft)[1] |
| Coordinates | 45°27′21″N71°09′10″W / 45.455775°N 71.152744°W /45.455775; -71.152744[2] |
| Geography | |
  Monteregian Hills Location in Quebec | |
| Country | Canada |
| Province | Quebec |
| Range coordinates | 45°29′N73°03′W / 45.483°N 73.050°W /45.483; -73.050 |
| Geology | |
| Rock age | Early Cretaceous |
TheMonteregian Hills (French:Collines Montérégiennes) is a linear chain of isolated mountains inMontreal andMontérégie, between theLaurentian Mountains and theAppalachians.
The first definition of the Monteregian Hills came about in 1903 when Montreal geologistFrank Dawson Adams began referring toMount Royal (Latin,Mons Regius) and mountains of similar geology in theSaint Lawrence Lowlands as the "Royal Mountains" (French:montagnes royales).[3] Other mountains in the chain includedMont Saint-Bruno,Mont Saint-Hilaire,Mont Saint-Grégoire,Mont Rougemont,Mont Yamaska,Mont Shefford, andMont Brome.
It was only later thatMont Mégantic,[4] the Oka Hills, as well as the Saint-André and d'Iberville formations, were added to the list.[5]
Each mountain in the chain consists of an erosional remnant ofCretaceousintrusiveigneousrock and associatedhornfels, which are more resistant toweathering than the surroundingsedimentary rock. All of the mountains have dark-colouredmafic rock such asgabbro andessexite; some also have large areas ofpulaskite,syenite, and other light-coloured rock.[citation needed]
The Monteregian Hills are part of theGreat Meteor hotspot track, formed as a result of theNorth American Plate sliding westward over the long-livedNew England hotspot,[6] and are theeroded remnants of intrusivestocks. These intrusive stocks have been variously interpreted as the feeder intrusions of longextinct volcanoes, which would have been active about 125 million years ago,[7][8] or as intrusives that never breached the surface in volcanic activity.[9] The lack of an obvious track west of the Monteregian Hills may be due either to failure of the plume to penetrate theCanadian Shield, to the lack of recognizable intrusions, or to strengthening of the plume when it approached the Monteregian Hills region. However, there is evidence the hotspot track extends northwestwards, includingepeirogenic uplift,mantle velocity anomalies andkimberlitic volcanic features (e.g. theAttawapiskat,Kirkland Lake andLake Timiskaming kimberlite fields) that become older away from the Monteregian Hills.[10]
The shallow, rocky sandy loam soils of the summits are mostly covered inforest. Where the underlying rock is rich inolivine, as over large areas of Mont Saint-Bruno and Mont Rougemont, these soils are classed asdystric brunisol.Podzol tends to develop over rock which lacks olivine, although many of these podzols lack an eluvial (Ae) horizon. Lower slopes are covered with aprons of gravel or sand. The sandy soils are usually podzols with classic Ae development; they often have subsoil hardpan and are undesirable for agriculture. The free-draining gravels are preferred forapple orchards, which grow in thermal belts where cold air can drain to the valley floor.[11][12]
| Name | Height | Age | Coordinates | Location |
|---|---|---|---|---|
| St. Andrews formation | 130 metres (430 ft) | n/a | 45°55"N, 74°31'W | Saint-André-d'Argenteuil |
| Oka Hills | 249 metres (817 ft)[13] | n/a | 45°28'N, 74°5'W | Oka |
| Mount Royal | 233 metres (764 ft) | 118-138myr | 45°30'23"N, 73°35'20"W | Montreal |
| Mont Saint-Bruno | 218 metres (715 ft) | 118-136 myr | 45°33'18"N, 73°18'36"W | Saint-Bruno-de-Montarville |
| Mont Saint-Hilaire | 411 metres (1,348 ft) | 135 myr | 45°33'8"N, 73°9'50"W | Mont-Saint-Hilaire |
| Mont Saint-Grégoire | 251 metres (823 ft) | 119 myr | 45°21'29"N, 73°9'8"W | Mont-Saint-Grégoire |
| Mont Rougemont | 381 metres (1,250 ft) | 137 myr | 45°28'36"N, 73°3'17"W | Rougemont |
| Mont Yamaska | 416 metres (1,365 ft) | 120-140 myr | 45°27'25"N, 72°52'19"W | Saint-Paul-d'Abbotsford |
| Mont Shefford | 526 metres (1,726 ft) | 120-130 myr | 45°21'49"N, 72°37'33"W | Shefford |
| Mont Brome | 553 metres (1,814 ft) | 118-138 myr | 45°17'21"N, 72°38'16"W | Bromont |
| Mont Mégantic | 1,110 metres (3,640 ft) | 128-133 myr | 45°27'21"N, 71°9'10"W | Notre-Dame-des-Bois |
Avec le progrès des connaissances géologiques, le mont Mégantic, les roches intrusives d'Iberville, d'Oka, et de Saint-André se sont progressivement ajoutés à la liste.
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