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Stratigraphy of the Aroostook-Percé Anticlinorium in the Gaspé Peninsula, Quebecl
MICHEL MALO
Groupe interuniversitaire de recherches géologiques en analyse de bassins (GIRGAB), Département de géologie, Université Laval, Cité Universitaire, Québec (Qué.), Canada GIK 7P4 and INRS-Géoressources, Complexe Scienti$que,
C. P. 7500, Sainte-Foy (Qué. ) , Canada G1 V 4C7
Received April 8, 1987
Revision accepted August 20, 1987
In Quebec, the Aroostook-Percé Anticlinorium exposes two stratigraphic groups: the Honorat and the Matapédia. The terrigenous units of the Honorat Group form the core of the anticlinorium and are overlain by the carbonate sequence of the Matapédia Group. Each group comprises two formations. The Honorat is herein divided into two new formations, the Arsenault and the Garin, which are defined for the first time. The Matapédia Group includes the Pabos and White Head for- mations. The Pabos Formation, a transitional unit between the noncalcareous strata of the Honorat Group and the carbonate facies of the White Head Formation, is here redefined. The White Head Formation comprises four members. These two groups represent continuous sedimentation from the Late Ordovician (Caradocian) to the Early Silurian (Llandoverian).
The lithostratigraphy of the type areas of the Honorat Group (Honorat Township region) and Pabos Formation (Chandler region) are fully described, whereas the lithostratigraphy of the type area of the White Head Formation (Percé area) is summa- rized only. The Arsenault, Garin, and Pabos formations and the Burmingham, Côte de la Surprise, L'Irlande, and Des Jean members of the White Head Formation constitute the stratigraphic sequence in the eastern part of the Aroostook-Percé Anti- clinorium. These units are extended to the western part of the anticlinorium in Quebec and in New Brunswick, and also to other Late Ordovician - Early Silurian rocks in the Chaleur Bay and Gaspé - Connecticut Valley synclinoria.
Rocks of the Aroostook-Percé Anticlinorium are interpreted as having been deposited by turbidity currents in a relatively deep water basin. Deposition evolved through time from terrigenous to limestone, reflecting a change in source areas.
The Grand Pabos fault divides the Aroostook-Percé Anticlinorium between Percé and Carleton into two areas with strati- graphically different sequences. The northern area is dominated by carbonate rocks of the Matapédia Group, whereas the southern area is composed mainly of terrigenous facies of the Honorat Group. Carbonate sedimentation of the White Head Formation started during Late Ordovician time in the northern area but only during Early Silurian times in the southem area. The thickness of the carbonate strata, which reaches 2000 m in the northern area, diminishes to 150 m in the southern area.
Au Québec, l'anticlinorium d'Aroostook-Percé se divise en deux groupes : Honorat et Matapédia. La séquence terrigène du Groupe d'Honorat constituent le coeur de I'anticlinorium; elle est suivie par les carbonates du Groupe de Matapédia. Ces deux groupes comprennent chacun deux formations. L'Honorat est ici divisé en deux formations, Arsenault et Garin, qui sont définies pour la première fois. Le Groupe de Matapédia comprend les formations de Pabos et de White Head. Le Pabos, une unité de roches terrigènes calcareuses entre les strates non calcareuses du Groupe d'Honorat et les faciès carbonatés de la Formation de White Head, est ici redéfinie. Le White Head est constitué de quatre membres définis précédemment. Ces strates représentent une sédimentation continue de l'ordovicien tardif (Caradocien) au Silurien hâtif (Llandoverien).
La lithostratigraphie des régions-type du Groupe d'Honorat (région d'Honorat) et de la Formation de Pabos (région de Chandler) sont décrites en détail, tandis que celle de la région-type de la Formation de White Head (région de Percé) est résumée seulement. Les formations d'Arsenault, de Garin et de Pabos de même que les membres de Burmingham, de Côte de la Surprise, de L'Irlande et de Des Jean de la Formation de White Head constituent la séquence lithostratigraphique de la partie orientale de l'anticlinorium d'Aroostook -Percé. Ces unités sont étendues à la partie occidentale de l'anticlinorium au Québec et au Nouveau Brunswick, mais aussi aux autres roches de l'ordovicien tardif et du Silurien hâtif des synclinoria de la Baie des Chaleurs et de Gaspé - Connecticut Valley.
Les roches de l'anticlinorium d'Aroostook-Percé sont interprétées comme des dépôts par courant de turbidité dans un bas- sin relativement profond. La déposition a évolué à travers le temps de terrigènes à carbonates, ce qui réflète un changement dans les régions~sources.
La faille du Grand Pabos divise l'anticlinorium d'Aroostook-Percé, entre Percé et Carleton, en deux régions ayant des séquences stratigraphiques différentes. La région septentrionale est dominée par les carbonates du Groupe de Matapédia, tan- dis que la région méridionale est surtout composée des roches terrigènes du Groupe d'Honorat. La sédimentation carbonatée du White Head a débuté à l'ordovicien tardif dans la région septentrionale, mais seulement au Silurien hâtif dans la région méridionale. L'épaisseur des carbonates atteint 2000 m dans la région septentrionale mais diminue à 150 m dans la région méridionale.
Can. J. Earth Sci. 25, 893-908 (1988)
Introduction the core of the anticlinorium and are overlain by the calcareous
The A ~ ~ ~ ~ ~ ~ ~ ~ - P ~ ~ ~ ~ ~ ~ ~ i ~ l i ~ ~ ~ i ~ ~ ( ~ é l ~ ~ d et al. 1979) Sequence of the Matapédia Group. The Matapédia Group corn-
is a major structural feature of the northern Appalachians prises the Pabos and White Head formations. stratigraphic
that includes sedimentary rocks from the L~~~ ordovician relationships between the Honorat and Matapédia groups have
(Caradocian) to the Early Silurian (Llandoverian) (Fig. 1). In never been clear (Skidmore 1965, 1967; Ayrton 1967). The
Quebec, these rocks belong to two groups, the Honorat and the relationship between the Pabos and White Head formations
Matapédia. The terrigenous rocks of the ~~~~~~t Group form WaS also obscure (Alcock 1935; Kindle 1936; McGerrigle 1950; Sanschagrin 1963; Ayrton et al. 1969). stratigraphic
'Published by permission of the ministère de l'Énergie et des Res- studies by Malo (1979, 1986a), Skidmore and Lespérance sources du Québec. (1981), and Lespérance et al. (1987) in the eastern part of the Printed in Canada i Imprimé au Canada
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CAN. J . EARTH SCI. VOL. 25. 1988
+ * + + + + * + + e t + + +
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Carboniferaus
Siiurian and Devonian
1 Siegas area
2 Northwestern New Brunswick
FIG. 1. Location of the Aroostook-Percé Anticlinorium in the northern Appalachians. Modified from Douglas (1969, Map 1250-A).
Aroostook - Percé Anticlinorium between Percé and New Richmond suggested a new lithostratigraphic framework that proved to be useful and applicable to the entire Quebec part of the anticlinorium. Mapping by Lachance (1974, 1975, 1977, 1979), Gosselin and Simard (1983), Gosselin (1984, 1985), Gauthier (1986), Kirkwood (1986), Ma10 (1986b, in press a, in press b), and Simard (1986) reinforced this litho- stratigraphic framework.
The principal deformation of the Aroostook -Percé Anticli- norium is Acadian (Malo and Béland 1985), and it is clear that
some rocks of the anticlinorium were deposited during the final stage of the Taconian orogeny. In fact, the Honorat Group in southern Gaspé Peninsula is the same age as rock units (Cloridorme Formation) deformed by the Taconian orogeny in the northern part of the peninsula (Riva and Malo 1988). Comprehension of the Aroostook -Percé Anticli- norium is particularly important in the global history of the northern Appalachians because of this. A good lithostrati- graphic framework will allow a better understanding of the Aroostook-Percé Anticlinorium as well as of its role in the
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tectonic evolution of the northern Appalachians. It is one of the aims of this contribution to formalize the
lithostratigraphy of the Late Ordovician - Early Silurian strata of the Aroostook-Percé Anticlinorium in the Gaspé Peninsula. This will be done by erecting two new formations (Arsenault and Garin) for the Honorat Group, by revising the concept of the Pabos Formation, and by extending the mem- bers of the White Head Formation described by Lespérance et al. (1987) to the entire Quebec part of the anticlinorium. The stratigraphy of the Aroostook-Percé Anticlinorium will be summarized by describing the Late Ordovician - Early Silurian sequence in two main regions of the Quebec part of the anticlinorium. One is the Honorat Township region (Fig. 2), where we divided the Honorat into two formations. The other is the Chandler region (Fig. 2), where the type area and a principal reference section of the Pabos Formation are located. Correlations will be made with other areas in the Gaspé and in northwestern New Brunswick. The actual nomenclature is different in each area, and it is very important to have a good lithostratigraphic framework for future work on the structural geology , sedimentology , and paleogeography of the anticlinorium.
Geological setting The Aroostook - Percé Anticlinorium, previously called the
Aroostook-Matapédia Anticlinorium (Pavlides et al. 1964), runs from Percé to Matapédia in the Quebec part of the oro- gen, crosses northwestern New Brunswick, and extends to Aroostook County in Maine (Fig. 1). The anticlinorium is bor- dered by two synclinoria of Silurian - Devonian rocks: the Gaspé - Connecticut Valley Synclinorium to the north and the Chaleur Bay Synclinorium to the south (Fig. 1). The Aroostook-Percé Anticlinorium corresponds to the Mata- pédia belt as described by Bourque et al. (in press), whereas the Gaspé - Connecticut Valley and Chaleur Bay synclinoria correspond, respectively, to the Gaspé and Chaleurs belts of the same authors (Bourque et al., in press).
The northern limit of the Aroostook-Percé Anticlinorium, where its rocks are in contact with the Silurian-Devonian rocks of the Gaspé - Connecticut Valley Synclinorium, is usually a conformable stratigraphic contact, but in places it is faulted. The southern limit of the anticlinorium, between its rocks and those of the Chaleur Bay Synclinorium, is also a conformable contact, but again faulted contacts occur locally. In Quebec, the Aroostook- Percé Anticlinorium is transected by a major strike-slip fault, the Grand Pabos fault, which runs east-west from Chandler to the Nouvelle River area (Skid- more and McGerrigle 1967), where it merges with the Risti- gouche fault.
The foundations of the Aroostook -Percé Anticlinorium are poorly known. At one locality in the Percé area (Fig. 2), rocks of the anticlinorium lie unconformably above older units deformed by the Taconian orogeny; the Honorat Group is absent, and a monoclinal sequence of Late Ordovician - Early Silurian strata, beginning with the Pabos Formation, overlies the Cambrian strata of the Murphy Creek and Corner of the Beach formations (Fig. 3). However, elsewhere in the anticlinorium, the Honorat Group is known to be the sarne age as a number of rock units deformed by the Taconian orogeny, such as the Cloridorme Formation of northern Gaspé Penin- sula and possibly the Mictaw Group of southern Gaspé Penin- sula. On both sides of the Aroostook-Percé Anticlinorium,
the top of the Matapédia Group is usually in stratigraphic con- tinuity with the Chaleurs Group.
Previous work
The earliest significant work on the rocks of the anticli- norium in the Percé area was carried out by Clarke (1908), Schuchert and Cooper (1930), and Cooper and Kindle (1936) and concerned the White Head Formation. Most of these studies were paleontological, but Clarke (1908) described for the first time the type section of the White Head Formation.
The type section of the Matapedia Series was first described by Crickmay (1932) in the Matapédia Valley. Alcock (1935) referred to these rocks as the Matapédia Group and recognized that they might be equivalent to those of the White Head For- mation in the Percé area. McGerrigle (1946) then showed that the northwestern part of Crickmay's (1932) type section of the Matapedia Series belonged to the Devonian Fortin Group.
Kindle (in Alcock 1935; and 1936) was the first to describe the Pabos Formation. Al1 the Ordovician rocks north of the Chaleur Bay Synclinorium, from the Grande Rivière in the east to the Petite Cascapédia River in the West, were included in the Pabos Formation (Kindle in Alcock 1935). Ordovician rocks located West of the Petite Cascapédia River were part of the Matapédia Group (Alcock 1935), and the White Head Formation was restricted to rocks of the Percé area, east of the Grande Rivière (Alcock 1935). McGerrigle (1950) considered the Pabos Formation a less calcareous facies of the Matapédia Group below the White Head Formation. Sanschagrin (1963) remapped some part of Kindle's (1936) region and included the strata originally assigned to the Pabos Formation in the Matapédia Group without using the term "Pabos." Skidmore (1965) assigned the Ordovician rocks of Honorat and Reboul townships to two groups on either side of the eastward-trend- ing Grand Pabos fault: the Matapédia Group to the north of the fault and the Honorat Group, defined for the first time, south of the fault (Fig. 4). Skidmore (1965) preferred using the Honorat and Matapédia groups even though the Ordovician strata in his region were north of the Chaleur Bay Syncli- norium and were part of the Ordovician Pabos Formation as defined by Kindle (in Alcock 1935). Since then, rocks typical of the Pabos Formation and its type area were considered as being in the region mapped by Kindle (1936) (Ayrton et al. 1969; Ma10 1986a, in press a ; Lespérance et al. 1987).
Distinct Ordovician and Silurian trilobite faunas in the White Head Formation of the Percé area were described for the first time by Lespérance (1968). Since then, many other paleontological studies have been conducted in the Percé area (Lespérance 1974, 1985; Lespérance and Sheehan 1976; Sheehan and Lespérance 1979, 1981; Martin 1980; Lespé- rance and Letendre 1981 ; Lespérance et al. 1981; Nowlan 1981; Riva 1981; Lespérance and Tripp 1985). The type sec- tion of the White Head Formation at Cap Blanc, in Percé, was briefly described by Bourque (1977). He divided the formation into three units: a lower calcilutite member, a middle mud- stone member, and an upper calcilutite member.
Malo (1979) described six superposed lithostratigraphic units in the Aroostook-Percé Anticlinorium north of Chand- ler. The terrigenous rocks immediately north of the Grand Pabos fault were assigned to the Honorat Group (Ayrton 1967; Malo 1979), as well as those at the base of the sequence in the core of the anticlinorium farther north (Fig. 5) (Malo 1979). The second and third units were correlated with the Pabos For-
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MALO
H O N O R A T A R E A (MALO , IN PRESS b )
C H A N D L E R A R E A (MALO, IN PRESS u
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FIG. 3. Lithostratigraphic correlations of the Percé area, Chandler and Honorat Township regions.
mation as described by Kindle (1936), whereas the last three units were correlated with the White Head Formation. The fourth unit was considered equivalent to the lower calcilutite member of Bourque (1977) at the type section, whereas the fifth unit was recognized as equivalent to the middle mudstone member; the sixth, to the upper calcilutite member. Al1 six of these units were seen to be in conformable contact, clearly demonstrating the normal conformable stratigraphic relation- ship between the Honorat and Matapédia groups and also between the Pabos and White Head formations of the latter group.
The Percé area (area 9, Fig. 2; column 9, Table 1) is divided into two areas on either side of the northwestward-trending major fault. The southwest area contains a monoclinal sequence of Late Ordovician - Early Silurian strata resting unconform- ably on Cambrian strata. The Cambrian strata are cut by the fault, to the northeast of which lie slivers of Ordovician, Devonian, and Carboniferous rocks. Skidmore and Lespé- rance (1981) divided the White Head Formation in the south- West area of Percé into nine lithostratigraphic units. Later on, Ma10 (1986~) assigned the three lower, terrigenous-dominated units to the Pabos Formation and showed that the contact between the Pabos and White Head formations should be defined in terms of the change from predominantly terrigenous (calcareous mudstone) rocks to predominantly limestone (calcilutite). Malo (1986~) thus extended the Pabos Forma- tion, previously known only north of Chandler, to the Percé area. The retracing of the Pabos - White Head contact from Chandler to Percé necessitated a revision of the lithostratigra-
phy in the Percé area (Lespérance et al. 1987). The White Head Formation is now restricted to the upper limestone- dominated sequence of the southwest area and is divided into four members: a lower calcilutite member, the Burmingham Member; a middle mudstone member, the Côte de la Surprise Member; an upper calcilutite member, the L'Irlande Member; and an argillaceous limestone member, the Des Jean Member. The Pabos strata in the Percé area are included in a new mem- ber, the Rouge Member. Ordovician strata of the northeastern area have been assigned to two assemblages: the Honorat Group and the Grande Coupe beds of the Matapédia Group (Lespérance et al. 1987). In the Grande Coupe beds, some facies correlative with the Pabos Formation of the Chandler region and with the Burmingham Member (Kirkwood 1986; Ma10 1986a) can be recognized. For a better description of these lithostratigraphic units, their distribution in the Percé area, and their faunal content, the reader is referred to Les- pérance et al. (1987). We will use these names to describe the White Head Formation in other areas.
The Honorat Township region
The Honorat Group was first defined by Skidmore (1965) in the Honorat-Reboul area. Skidmore (1965) divided the Ordo- vician rocks of the Honorat Township region (area 5, Fig. 2; column 5, Table 1) into two zones, located north and south of an easterly trending fault. This fault was later named the Grand Pabos Nord fault, east of the Honorat-Reboul area, by Ayrton (1967) and is now usually called Grand Pabos fault.
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898 CAN. J. EARTH SCI. VOL. 25 , 1988
STRUCTURAL CROSS SECTION
S T R A T I G R A P H Y S l L U R l A N AND D E V O N I A N
C H A L E U R GROUP
O R D O V l C l A N AND S l L U R l A N
[IYHI WHITE H E A D FM. (L.IRLAIIDE RB)
PABOS FM. (UNIT 3 1
P A B O S F M . ( U N I T 2 )
PAElOS FM. ( U N I T l 1
'-2-3 U N l T S D E S C R I B E D I N APPENDIX 4-5
\ S T R A T O T Y P E S
FIG. 4. Geological map of the Honorat Township region and locations of the stratotypes of the Arsenault and Garin formations. Location given in Fig. 2. Same symbols as in Fig. 5. Modified from Ma10 (in press b).
Skidmore (1965) assigned the limestones north of the fault to eous dark mudstone of the Honorat Group to a calcareous the Matapédia Group and introduced the Honorat Group for mudstone unit is the same as the transition between the the terrigenous rocks south of the fault. In the type area of the Honorat Group and the Pabos Formation as defined in the Honorat Group, Ma10 (1986a, in press b) recognized calcare- principal reference section of the Pabos Formation (see ous rocks similar to the rocks of the Pabos and White Head below). The presence of lithostratigraphic units assigned to the Formations of the Matapédia Group to the south of and over- Pabos and White Head formations in the original type area of lying the terrigenous rocks. The transition from the noncalcar- the Honorat Group necessitates a revision of the lithostrati-
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graphy of this area (Fig. 4). As understood here, the Honorat Group is restricted to the noncalcareous terrigenous rocks as proposed by Skidmore (1965).
The Honorat Group as redefined can be divided into two lithostratigraphic units. The first unit, composed mainly of greenish grey lithic wacke with clay slate interbeds, is restricted to the northern part of the Honorat Township region and is bordered to the north by the Grand Pabos fault. This first unit is overlain to the south by a second unit of terrige- nous rocks comprising mudstone, sandstone, and conglomer- ate (Fig. 4). These two lithostratigraphic units correspond to two new formations introduced here for the first time. The first unit, the Arsenault Formation, crops out in a northerly trending brook that runs from Arsenault Lake, from which it takes its name, to the Grand Pabos fault (Fig. 4). The Arse- nault Formation is also well exposed along an east - West road in the northern part of the area (Mer Road, Fig. 4). The second unit, the Garin Formation, crops out dong a northerly trending road in Garin Township, from which it takes its name (Fig. 4). The best section of the Garin Formation, however, is exposed in a brook that runs south from the east -West Mer Road to the Garin River (Fig. 4).
The division of the Honorat Group into two formations allows us to better understand the Ordovician rocks in the southern part of the Gaspé Peninsula. Strata assigned to the Honorat Group in other areas (Matapédia, Carleton, New Richmond, Chandler, and Percé) belong to the Garin Forma- tion, whereas the oldest unit, the Arsenault Formation, is restricted to its type area. Rocks similar to those of the Arse- nault Formation have been described by De Broucker (1986) in the "Neckwick Formation" (sensu De Broucker 1986) of the Mictaw Croup. Correlation between the Arsenault and Neckwick formations has been suggested by Ma10 (1986~) and De Broucker (1986). However, the upper formation of the Mictaw Group, the "Ruisseau à Dubuc Formation" (sensu De Broucker 1986) has lithologies similar to those of the Garin Formation (Malo 1986a; De Broucker 1986). It should be mentioned that the Mictaw Group is composed of three lithostratigraphic units according to De Broucker (1986) and that the Neckwick and the Ruisseau à Dubuc formations are separated by a mélange, the "Rivière du Milieu Mélange" (sensu De Broucker 1986).
No fossil collections have been made in the type area of the Honorat Croup. The Garin Formation yields graptolites of the Climacograptus spiniferus Zone in the New Richmond area (Riva 1981; Riva and Malo 1988) as well as in the Chandler region (Malo 1986~; Riva and Ma10 1988) (see below). The age of the Arsenault Formation is unknown but obviously has to be no younger than the C. spiniferus Zone. The Neckwick Formation of the Mictaw Group yields graptolites from the Didymograptus murchisoni Zone (De Broucker and Riva 1985), which suggests that the Arsenault Formation could be as old as Llanvirnian.
Stratigraphy In the Honorat Township region, both the Honorat and the
Matapédia groups are present, and the four formations that constitute the Aroostook-Percé Anticlinorium in the Gaspé Peninsula can be recognized (Fig. 4).
The Arsenault Formation (Appendix) is composed mainly of greenish grey lithic wacke with black to olive-green, locally red, claystone and minor grey to black, fine-grained tuff inter- beds and calcareous sandstone. The wacke is thick bedded, usually massive, but graded bedding may occur at the base of
some beds. The tuff is composed of shards of volcanic glass. Minor amounts of very fine grained calcareous sandstone in 2 - 5 cm thick beds are present locally . The Arsenault Forma- tion crops out only to the south of the Grand Pabos fault in this area, and its minimum thickness is estimated to be 600 m. The underlying rocks are unknown.
The Garin Formation is composed of various terrigenous rocks (Appendix, units 2, 3 ,4 , and 5) ranging from very fine- grained pelite to coarse-grained conglomerate. Fine-grained rocks-black claystone, dark mudstone, and greenish grey siltstone-constitute the major part of the formation. Calcare- ous siltstone, calcareous quartz wacke, and lithic and feld- spathic wacke, as well as conglomerate and dolomitic limestone, are interbedded in the noncalcareous dark pelites. The wacke and conglomerate occur in the lower part of the formation (Appendix, units 3 and 4), whereas the calcareous siltstone, calcareous wacke, and dolomitic limestone can be found in the upper part (Appendix, units 4 and 5).
Laminated dark mudstone and dark green siltstone represent more than 50% of the formation. Laminae are brown, silty, 2 -5 mm thick, and usually calcareous. Slumps occur locally in the laminated mudstone. These small (decimetre size) folds of erratic geometry are associated with 1-2 m thick conglo- meratic zones in which quartz fragments are disseminated in an argillaceous matrix. Other conglomerate beds, forming approximately 5% of the formation, are thick bedded and composed of various lithic fragments (dark laminated mud- stone, greenish grey lithic wacke, calcareous wacke, very fine grained calcareous arenite, silty limestone, igneous rocks, and green chert) in a silty to arenaceous matrix. Most of the clasts have a diameter of 5 - 10 cm and come from the Arsenault and Garin formations. The igneous fragments and chert must be derived from another source. Some medium-thick and graded- bed lithic and feldspathic wackes are associated with the conglomerate. Greenish grey lithic and feldspathic wackes represent approximately 20% of the formation. They are thin to medium bedded and fine to medium grained and exhibit graded bedding, parallel and cross-laminations, and flute casts. Siltstone and quartz wacke (20% of the formation) are thin bedded and display parallel and cross-laminations. Lime- Stones (5% of the formation) are silty, thin bedded, and usu- ally dolomitic.
The Garin Formation conformably overlies the Arsenault Formation. The first occurrence of dark mudstone and silt- stone defines the base of the formation. At its top, the dark mudstone is replaced rapidly by brown to beige calcareous mudstone of the Pabos Formation. The Garin Formation is widespread throughout the Aroostook - Percé Anticlinorium, and its thickness is estimated to be 1200 m in the Honorat Township region.
The Pabos Formation in the Honorat Township region con- sists of three lithologic units. The lower unit (Pl, Fig. 4) is made up to 300 m of calcareous laminated mudstone inter- bedded with very thin siltstones and rare calcilutite. The middle unit (P2, Fig. 4) is composed mainly of greenish grey mudstone and siltstone, sometimes calcareous, and is quite similar to the fine-grained terrigenous rocks of the Garin For- mation. Sandstone and conglomerate also occur in this unit, which reaches a thickness of 300 m. The upper unit (P3, Fig. 4) is made up of 100 m of argillaceous limestone and a few beds of calcilutite near the top of the unit.
The White Head Formation is composed of medium-bedded calcilutite with shale interbeds. Calcareous fine-grained quartz sandstones are found locally as interbeds. The lower contact
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UNIT
S DE
SCRI
BED
IN A
PPEN
DIX
\ RE
FERE
NCI
SECT
lON
OF
THE
PABO
S FM
.
SlLU
RlAN
AN
D DE
VONI
AN
CHAL
EUR
GROU
P
ORDO
V IC
I AN
AND
SlLU
RlAN
[csl
COT
E DE
L
A SU
RPR~
SE
BURM
INGH
AM
MB.
UNCO
IIFûR
MITI
F2
SYN
CLIN
E (U
PRIG
HT)
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with the Pabos Formation is placed at 50% of the calcilutite beds. The Clemville Formation conformably overlies the White Head Formation and begins with very fine grained sandstone. In the Honorat Township region, the White Head Formation consists of only one 150 m thick unit, whereas in the Chandler region four members are present and their thick- ness totals 2000 m (see below). The unit of the White Head Formation in the Honorat Township region is correlative with the L'Irlande Member of the Chandler region (Fig. 3).
Ages and faunas The precise age of the Arsenault Formation is unknown but
has to be older than the Clirnacograptus spiniferus Zone,' because the overlying Garin Formation yielded a graptolitic fauna typical of this zone (Riva 1981; Malo 1986a; Riva and Ma10 1988). The middle unit of the Pabos Formation yielded brachiopods of the Late Ordovician (Boucot in Ma10 1986a), and this brachiopod fauna is of probable Hirnantian age (Lespérance in Ma10 1986~). The age of the White Head For- mation is bracketed by the underlying latest Ordovician Pabos Formation and the overlying Llandoverian A3-4 Clemville Formation (Bourque and Lachambre 1980). In the Carleton area, West of the Honorat Township region, the occurrence of the trilobite Acernaspis sp. in the calcilutite beds of the same unit indicates a Silurian age for the White Head Formation (P. J. Lespérance, persona1 communication, 1985).
Chandler region - This area (area 8, Fig. 2; Fig. 5; column 8, Table 1)
includes the original area mapped by Kindle (1936), which is considered the type area of the Pabos Formation (see above), comprising the southern part of Raudin Township, Pabos Seig- neury (from which it takes its name), Grande Rivière Town- ship, and the western part of Rameau Township. The best exposures of the Pabos Formation in this area are located in the southern parts of the Grande Rivière and Petit Pabos val- ley s, northeast of Chandler.
As originally described by Kindle (1936), the Pabos Forma- tion in this region was composed of a terrigenous unit at the base and a limestone unit at the top, separated by a transitional unit, the overall sequence being too heterogeneous to consti- tute a single formation. Recent mapping (Ayrton 1967; Malo 1979) assigned the basal terrigenous rocks to the Honorat Group and the limestone to the White Head Formation. There- fore, it was proposed (Malo 1986a, in press a) that only the transitional unit constitutes the Pabos Formation. Since then, the Pabos Formation has been recognized in the type area of the Honorat Group (Malo, in press b) (see above).
There are numerous faults in the southern part of the area, and 1 propose a principal reference section in the northern part of the Chandler region where contacts with the underlying Honorat Group and the overlying White Head Formation can be observed. In this section, the Pabos Formation is well developed (1400 m, Appendix) and comprises four principal divisions (units 2, 3, 4, and 5, Appendix), although only two are easily mapped (lower and upper Pabos, Fig. 5). This prin- cipal reference section, on the Grande Rivière Ouest just north of the major anticline made up of the Honorat Group (Fig. 5), will be described. This description will permit a better under- standing of the Pabos Formation.
'A graptolite faunule recovered at the end of the surnrner of 1987 indicates a Llanvernian age (see Riva and Ma10 1988).
In the Chandler region, three fossil localities have given an Ashgillian age to the Pabos Formation (McGerrigle 1950; Ma10 1979). the first locality includes brachiopods, in which P. J. Lespérance recognized Epitomyona americana Sheehan and Lespérance, Dalrnanella sp., and cf. Glypthorthis robusta Sheehan and Lespérance (in Ma10 1979). The two other local- ities furnished the trilobite Novaspis elevata (McGerrigle 1950; Malo 1979).
Stratigraphy Both the Honorat and the Matapédia groups are present in
the Chandler region. The upper formation of the Honorat, the Garin Formation, crops out in the core of the anticlinorium and is followed by the Pabos and White Head formations of the Matapédia Group.
Only the upper part (800 m) of the Garin Formation is exposed. It consists of dark greenish grey noncalcareous mud- stone interbedded with thin- to thick-bedded, fine- to medium- grained lithic wacke and thin-bedded, fine-grained calcareous quartz wacke. The sandstone exhibits numerous sedimentary structures (graded bedding, parallel and cross-laminations, and load and flute casts).
The lower part of the Pabos Formation (Appendix, unit 2) consists of calcareous mudstone interbedded with very thin bedded calcareous siltstone. There are several slumps in this lower part of the formation. The upper part of the formation consists of various calcareous rocks (Appendix, units 3 and 4); mudstone, siltstone, sandstone, conglomerate, argillaceous and silty limestone, sandy calcarenite,-and calcilutite. The cal- careous mudstone and argillaceous limestone are thin bedded and interlayered with very thin bedded calcareous siltstone, silty limestone, and calcilutite. Calcarenites are thin to thick bedded or lenticular. Calcarenite lenses are graded, and their bases contain sandy quartz grains. The calcilutites are very thin bedded and are present in the top of the formation (Appen- dix, unit 5). The calcareous sandstones are medium bedded and exhibit parallel and cross-laminations and flute casts. The calcareous conglomerates occur in thick beds and contain clasts of sericite and chlorite schists, milky quartz, and foli- ated sandstones.
The first occurrence of calcareous mudstone marks the base of the Pabos Formation. This lower contact with the dark mud- stone of the underlying Honorat Group is gradational. The upper contact with the overlying White Head Formation is also gradational, and the base of the White Head Formation has been traced arbitrarily where the sequence is at least 50 % cal- cilutite beds. The thickness of the Pabos Formation is esti- mated to be 1400 m in the Chandler region.
The four members of the White Head Formation as defined in the Percé area can be followed West to the Chandler region (Malo 1986a; Lespérance et al. 1987) and also north of the Grand Pabos fault, as far as the New Richmond area (Malo 1986a, 1986b).
In the Chandler region the first member, the Burmingham Member, consists of thin-bedded grey calcilutite with thinner interbeds of brown calcareous mud shale and a few thin beds of calcarenite. The second member, the Côte de la Surprise Member, is composed mainly of dark green calcareous mudstone containing a few thin- to medium-bedded, fine- to medium-grained quartz arenites. The third member, the L'Irlande Member, consists of regularly bedded, 7-15 cm thick grey calcilutites, with 2-5 cm thick calcareous mud shale interbeds; a few thin-bedded bioclastic calcarenites are
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902 CAN. 1. EARTH SCI. VOL. 25, 1988
present locally. Some 10- 15 m thick zones of dark clay shale quartz-pebble conglomerate with a calcareous matrix occur are present locally. The fourth member, the Des Jean locally. Its upper part is made up of massive calcareous mud- Member, is made up of thinly bedded, silty and argillaceous stone and argillaceous limestone interbedded with thin-bedded limestone, calcareous shale, and lenticular calcarenite, with calcareous siltstone. The overlying White Head Formation local thick beds of limestone conglomerate. The White Head consists of 4000 m of carbonate rocks (S. Lachance, persona1 Formation is overlain by the clay shale of the Burnt Jam Brook communication, 1984), in which the four members of the Formation of the Chaleurs Group. Percé area were recognized (Malo 1986~).
Ages and faunas The age of the sequence in the Chandler region is based on
graptolites, brachiopods, and conodonts. The Garin Forma- tion contains two graptolite assemblages (Riva and Ma10 1988). The older assemblage contains the species Climaco- graptus spiniferus, typical of the C. spiniferus Zone of Cara- docian age (Riva 1974). The younger assemblage ranges from the Climacograptus pygmaeus to the Paraclimacograptus manitoulinensis zones, indicating a Caradocian to Ashgillian age. The Pabos Formation has yielded brachiopods of Ashgil- lian age (Lespérance in Ma10 1979). The Burmingham Member of the White Head Formation is also Ashgillian, since it contains conodonts of fauna 13, especially the species Gamachignathus ensifer (Nowlan in Ma10 1986~). The Côte de la Surprise Member is nonfossiliferous, but it is considered Hirnantian, the same age it is in the Percé area (Lespérance 1974; Sheehan and Lespérance 1979). The L'Irlande and Des Jean members of the White Head Formation are Llandoverian in age, not younger than C,-,, since they contain conodont assemblages of the Distomodus kentuckyensis Zone (Nowlan in Ma10 1986~). On the other hand, the Des Jean Member also contains the graptolite Metaclimacograptus undulatus Kurk, known to range from the Coronograptus cyphus Zone to the Monograptus convolutus Zone (Llandoverian A,-B,) (Riva and Malo 1988). The Des Jean Member is in turn overlain by the Burnt Jam Brook Formation, which yields the graptolite Monograptus sedgwicki of Llandoverian Cl-, age (Bourque and Lachambre 1980); thus, the graptolitic faunas constrain the upper age limit of the Des Jean Member to Llandoverian B,. In the Percé area, the L'Irlande Member contains cono- donts of the D. kentuckyensis Zone (Nowlan 1981), and the recovery of the conodont species Aulacognathus bullatus in the Des Jean Member indicates an upper age limit of Llando- verian C, for this member and for the White Head Formation in this area. It seems that the upper age limit of the White Head Formation is younger in the Percé area than in the Chandler region (Table 1). It should be pointed out that the upper age limit is based on conodonts in the Percé area and on graptolites in the Chandler region.
Correlations with other areas Matapédia area
Both the Honorat and the Matapédia groups are recognized in the Matapédia area (area 3, Fig. 2; column 3, Table 1) (Lachance 1974, 1975, 1977, 1979). The Honorat Group is represented by the Garin Formation only; it is composed of dark grey noncalcareous mudstone interbedded with thin- to medium-bedded siltstone and medium- to thick-bedded wacke (Lachance 1974, 1975). Its thickness is estimated to be 800 m (S. Lachance, personal communication, 1984). Both forma- tions of the Matapédia Group are present. The Pabos Forma- tion consists of 3000 m of calcareous terrigenous rocks (S. Lachance, persona1 communication, 1984). Its lower part consists of fine- to coarse-grained lithic sandstone with inter- beds of calcareous to noncdcareous mudstone: thick beds of
The Honorat roufa and the Pabos Formation are not dated in the Matapédia area. Nowlan (1981) reported conodonts of Late Ordovician age from the White Head Formation in the roadcut section dong the Matapédia River and Restigouche River east of Matapédia, whereas the White Head Formation also yields the graptolite Glyptograptus persculptus (Salter) in the roadcut dong the Matapédia River, indicating a latest Ordovician age (Riva and Ma10 1988). The presence of the ostracode Bolbineossia sp. and the trilobite Acernaspis sp. (P. J. Lespérance, persona1 communication, 1985) in rocks of the White Head Formation indicates a Silurian age for the upper White Head Formation.
Saint-Jean River Anticline A Late Ordovician - Early Silurian rock assemblage crops
out in the core of the Saint-Jean River anticline (area 7, Fig. 2; column 7, Table 1) within the Gaspé - Connecticut Valley Synclinorium. This assemblage belongs to the White Head Formation and has been divided into two members (Bourque 1975, 1977): a lower mudstone member made up of dark green mudstone and an upper limestone member composed of grey to brownish grey thinly bedded calcilutite with shaly interbeds and containing local clay shale units. The lower member is correlated with the Côte de la Surprise Member of the White Head Formation of the Percé area, whereas the upper member consists of the L'Irlande and Des Jean members of the Percé area.
Based on brachiopods and trilobites, the White Head Forma- tion is early Llandoverian in the Saint-Jean River Anticline (Ayrton et al. 1969). The Des Jean Member yields Llan- doverian conodonts of the D. kentuckyensis Zone (G. S. Nowlan, persona1 communication, 1986).
Gastonguay Anticline Rocks belonging to the White Head Formation of the
Matapédia Group occur in the core of the Gastonguay Anti- cline (area 4, Fig. 2; column 4, Table 1) within the Gaspé - Connecticut Valley Synclinorium (Bernard and St-Julien 1986; Bourque and Gosselin 1986). Only the Des Jean Member of the White Head Formation is exposed. It consists of thinly bedded silty and argillaceous limestone and calcareous shale.
There are no fossil collections from the Gastonguay Anti- cline, but the Des Jean Member is presumed to be early Llan- doverian, as elsewhere.
Duval Anticline A Late Ordovician - Early Silurian rock assemblage con-
sisting of two units crops out in a subsidiary anticline (area 6, Fig. 2; column 6, Table 1) in the Quebec part of the Chaleur Bay synclinorium. The lower unit is a mudstone and siltstone assemblage with which a few 3-5 m thick sandstones and conglomerates are interbedded. The upper unit consists of cal- cilutite in 4-5 cm thick regular layers interbedded with thin argillaceous limestones. Minor nodular wackestones occur in the lower part of the unit. The calcilutite unit assigned to the Matapédia Group by Bourque and Lachambre (1980) belongs to the White Head Formation and is correlated with the
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TA
BL
E 1.
Cor
rela
tion
ch
an
of
the
Lat
e O
rdov
icia
n - E
arly
Sil
uria
n ro
cks
in t
he G
aspé
Pen
insu
la a
nd n
orth
wes
tern
New
Bru
nsw
ick
H :
Hirn
anüa
n St
age
G : G
amac
hian
Sta
ge
A-B
-C :
Bra
chio
pod
Zon
es
NO
TE
S: G
rapt
olit
e zo
nes
from
Ber
ry a
nd B
ouco
t (19
70) a
nd R
icka
rds a
nd R
iva
(198
1); c
onod
ont z
ones
fro
m N
owla
n (1
983b
): S
iega
s ar
ea f
rom
Ham
ilton
-Sm
ith (
1970
, 198
0):
nort
hwes
tern
New
Bru
nsw
ick
area
fro
m S
t. Pe
ter
(197
7);
Per
cé a
rea
mod
ifie
d fr
om L
espé
ranc
e et
al.
(19
87).
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SIEGAS AREA (Hamilton-Smith 1970,1980)
CAN. 1. EARTH SCI. VOL. 25, 1988
QUEBEC (this study)
NORTHWESTERN
NEW BRUNSWICK (St. Peter 1977)
I
0 P
shale P
member a k a a
GROG BROOK
$ W P
2 , a a
k a a O z O x
> cc a O
FIG. 6. Lithostratigraphic correlations between the Quebec and New Brunswick parts of the Aroostook-Percé Anticlinorium.
slate
lover calcitutite
Silurian part of the White Head Formation in the Honorat Township region (L'Irlande Member). The lower unit was assigned to the Honorat Group by Bourque and Lachambre (1980), but it is better correlated with the terrigenous unit of the Pabos Formation of the Honorat Township region. Sand- Stones yield the brachiopod Hirnantia sagittiferra (M'Coy), suggesting that this unit is of Hirnantian age (P. J. Lespérance, persona1 communication, 1985).
C3
5 I W t
s
unnamed unit or
MADAWASKA LAKE
New Brunswick-Siegas area The Carys Mills Formation, defined in Maine by Pavlides
(1968), was extended to the Siegas area (area 1, Fig. 1; column 1, Table 1) by Hamilton-Smith (1970). The ribbon limestone of this formation overlies a terrigenous unit that Hamilton-Smith (1970) referred to as the unnamed unit and, later on, correlated with the Madawaska Lake Formation (Hamilton-Smith 1980).
The unnamed unit, or the Madawaska Lake Formation, of the Siegas area is composed mainly of dark grey noncalcare- ous mudstone interbedded with fine-grained calcareous sand- stone and reaches an approximate thickness of 600 m. The unit has been correlated with the Grog Brook Group by St. Peter (1977) (see below). Recent work by the author in the area sug- gests a correlation of this unit with the Garin Formation of the Honorat Group of the Gaspé sequence (Fig. 6). This terri- genous unit is overlain by the Carys Mills Formation (Hamil- ton-Smith 1970), which comprises three members: a lower and an upper limestone member made up of thin- to medium- bedded argillaceous calcilutite with shale interbeds, and a middle slate member composed of slate with minor quartz sandstone. The thickness of the formation is estimated to be 400 m.
The contact traced by Hamilton-Smith (1970) between the limestone of the Carys Mills Formation and the underlying ter- rigenous unit corresponds to that defined between the Honorat and Matapédia groups in Gaspé; therefore, the Carys Mills
Des Jean
L'Irlande
Cote de la Surprise
Burmingham
Formation corresponds to the Matapédia Group in Quebec. The middle slate member of the Carys Mills Formation can be correlated with the Côte de la Surprise Member of the White Head Formation (Fig. 6); the lower calcilutite member is likely to be equivalent to both the Burmingham Member and the entire Pabos Formation, whereas the upper limestone member would be equivalent to the L'Irlande Member (Fig. 6).
The age of the Madawaska Lake Formation in the Siegas area ranges from late Middle Ordovician to Late Ordovician, and that of the Carys Mills Formation ranges from Late Ordo- vician to Early Silurian (Hamilton-Smith 1970, 1980).
PABOS
GARlN
ARSENAULT
New Brunswick-northwestern area St. Peter (1977) divided the strata of the Aroostook-Percé
Anticlinorium in northwestern New Brunswick (area 2 , Fig. 1; column 2, Table 1) into two groups: the Grog Brook Group, defined for the first time, and the Matapédia Group. He correlated the Matapédia Group with the Carys Mills Formation of the Siegas area; the Grog Brook Group, with the Honorat Group of the Gaspé Peninsula and the unnamed unit of the Siegas area.
The Grog Brook Group is made up of various terrigenous rocks: slate, siltstone, sandstone, and conglomerate (St. Peter 1977). Its thickness is estimated to be 7600 m. Although St. Peter (1977) considered the Grog Brook Group a litho- stratigraphic equivalent of the Honorat Group of the Gaspé Peninsula, careful examination of Lachance's (1974, 1975) and St. Peter's (1977) maps and recent investigations by the author in the Restigouche River area suggest rather that the Grog Brook Group is equivalent not only to the Honorat Group but also to the Pabos Formation of the Matapédia Group (Fig. 6). The Grog Brook Group is overlain by the Matapédia Group (sensu St. Peter 1977), which is composed of various carbonate rocks (argillaceous limestone, calcareous shale, sandy limestone, and limestone conglomerate) and
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whose thickness ranges from 1250 to 2750 m. It is possible to recognize in the carbonate sequence some of the facies of the Pabos and White Head formations of the Gaspé sequence. St. Peter (1977) noted the occurrence in places of a 10 m thick unit of brown- to green-weathering calcareous shale, locally interbedded with calcareous sandstones, mappable as a sepa- rate internal member of the Matapédia Group. It is quite pos- sible that this shale member correlates with the Côte de la Surprise Member of the White Head Formation and the slate member of the Carys Mills Formation in the Siegas area (Fig. 6).
The age of the Grog Brook Group ranges from late Middle Ordovician to Late Ordovician (St. Peter 1977). Nowlan (1983~) reported conodonts indicating a probable Gamachian age. Graptolites collected from the same section as Nowlan's (1983~) have been identified by Riva (Riva and Ma10 1988) as being the species Dicellograptus cf. complanatus Lapworth, which indicates an Ashgillian age for this part of the Grog Brook Group.
Depositional environments and provenance Sandstones of the Honorat and Grog Brook groups and of
the Pabos Formation commonly possess internal sedimen- tary structures typical of turbidite facies (St. Peter 1977; Ducharme 1979; Ma10 1986~). These sedimentary structures also characterize the silty limestones and the calcarenites of the White Head Formation in the Chandler region of the Gaspé Peninsula (Malo 1986a), as well as the rocks of the Matapédia Group and the Carys Mills Formation of New Brunswick (Hamilton-Smith 1970; St. Peter 1977). The Late Ordovi- cian - Early Silurian strata of the Percé area are fossiliferous (Lespérance et al. 1987); however, shelly fossils are usually uncommon elsewhere in the sequence, and graptolites are only found locally (Riva and Ma10 1988), thus reflecting a deep- water environment. Trace fossils of the Grog Brook and Mata- pédia groups of northern New Brunswick indicate a deep-sea environment (Pickerill 1980). Therefore, as a whole, rocks of the Aroostook-Percé Anticlinorium are interpreted as having been deposited by turbidity currents in a relatively deep water basin.
Deposition evolved through time from terrigenous (Honorat and Grog Brook) to limestone (Matapédia and Carys Mills) facies. This change from terrigenous to limestone facies reflects a change in the source area. Tuffs beds of the Arse- nault Formation together with abundant rocks fragments in the sandstones and conglomerate of the Arsenault and Garin for- mations suggests an active volcanic source area during the ini- tial phase of the sedimentation. This initial phase was possibly contemporaneous with the final stage of the Taconian oro- geny, since rocks of the same age as the Cloridorme Forma- tion in the northern Gaspé Peninsula (Riva and Ma10 1988) are involved in the Taconian deformation. As a whole, the compo- sition of the Honorat Group suggests a source area composed of volcanic, metamorphic, sedimentary, plutonic, and ultra- basic rocks (Malo 1986~). The Maquereau inlier in southern Gaspé Peninsula, including the small serpentinite massif to the northwest (Weir Township serpentinite of Ayrton 1967), and the Elmtree inlier and the Miramichi Anticlinorium in New Brunswick are thought to be the source area (Malo 1986a), implying that these terranes were emergent during sedimenta- tion of the Honorat Group. Rast and Stringer (1980) proposed the Pointe Verte Formation of the Fournier Group as a pos- sible source area for mafic volcanic rocks of the Grog Brook
conglomerates. Therefore, it seems likely that infilling of the Aroostook - Percé Anticlinorium basin first occurred with ter- rigenous material from a southern source area (see also Neuman 1984).
By the end of Ordovician time in the Chandler region and the beginning of Silurian time in the Honorat Township region, the composition of the material infilling the basin changed from terrigenous to carbonate sediments. The Anti- costi-shelf area, where carbonate sedimentation was very active during that time (Bolton 1981; Petryk 1981), is con- sidered the source area of the thick lime mud sequence of the White Head Formation (Lespérance et al. 1987; Bourque et al., in press), as there is no other active carbonate shelf known south of the basin. By the beginning of Silurian time, the Aroostook-Percé Anticlinorium basin was entirely covered by carbonate and sediments. This carbonate sedimen- tation stopped in Llandoverian time in the Chandler region, where the White Head Formation is covered by the s i rn t Jam Brook Formation, and in Llandoverian A,-, time in the Honorat Township region, where the White Head Forma- tion is covered by the Clemville Formation (Fig. 3).
Summary and conclusions
In Quebec, the Aroostook - Percé Anticlinorium is tran- sected by the Grand Pabos fault, defining two areas with strati- graphically different sequences (Fig. 3). The sequence of the Chandler region is characteristic of the northern area. This area (Fig. 2) is dominated by calcareous rocks of the Mata- pédia Group (Pabos and White Head formations) (Fig. 4), whereas the Honorat Group is restricted to the core of the anti- clinorium. The four members of the White Head Formation are recognized throughout the area from Percé to the longitude of New Richmond (Malo 1986b). The sequence of the Honorat Township region is typical of the southern area, which is com- posed mainly of terrigenous facies. Only one unit of the White Head Formation is present (L'Irlande Member) (Fig. 3); the three other members are totally absent. The stratigraphy of the southern area (Fig. 2) extends from the Honorat Township region to the New Richmond (Gosselin 1985; Ma10 19863) and Carleton areas (Simard 1986). Therefore, the carbonate sedimentation of the White Head Formation started during Late Ordovician time in the northern area but only in Early Silurian time in the southern area. Moreover, the thickness of the carbonate facies, which reaches 2000 m in the Chandler region, diminishes to 150 m in the Honorat Township region (Fig. 3). Therefore, the stratigraphic sequence of the Aroo- stook- Percé Anticlinorium between Percé and Carleton sig- nificantly differs on either side of the Grand Pabos fault (Fig. 3).
West of the Carleton area, the structurally complex Nou- velle and Escuminac areas are crosscut by numerous faults. However, it is still possible to identify the Garin Formation, the Pabos Formation, and the four members of the White Head Formation (Malo 1987). This situation is similar in the Mata- pédia area (see above), and future work (in progress) will help to clarify the structure and stratigraphy of this western part of the anticlinorium in Quebec.
The Aroostook-Percé Anticlinorium in Quebec and adja- cent New Brunswick is composed of two main rock assem- blages: (1) a lower siliciclastic assemblage, consisting of the Honorat and Grog Brook groups, and (2) an upper carbonate assemblage, consisting of the Matapédia Group and the Carys Mills Formation. A transitional assemblage, the Pabos Forma-
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tion of the Matapédia Group, is clearly identified in the Appalachian-Caledonian region: Canada and Greenland. Edited Quebec part of the anticlinorium. by H . Williams. Geological Society of America, Decade of North
American Geolopv. Vol. F-1 .
Acknowledgments 1 would like to thank Brian Skidmore of the ministère de
l'Énergie et des Ressources du Québec, who supervised the fieldwork and critically reviewed this manuscript. This work represents part of a Ph .D. thesis at the Université de Montréal, and 1 gratefully acknowledge Jacques Béland's suggestions as my advisor. Thanks are extended to Pierre J . Lespérance of the Université de Montréal for his advise on the paleontology of the Ordovician and Silurian strata of the Gaspé Peninsula and also for identifying the brachiopods and the trilobites. 1 a m also grateful to Arthur J . Boucot (Oregon State University), Godfrey S . Nowlan (Geological Survey of Canada), and John Riva (Université Laval) for their identification of brachiopods, conodonts, and graptolites. My appreciation is also extended to Pierre-André Bourque and Donna Kirkwood for critically reviewing this manuscript.
This work would not,have been possible without the support of the ministère de 1'Energie et des Ressources du Québec, which has defrayed the field expenses and permitted the use of the data. 1 would also like to thank the Natural Sciences and Engineering Research Council of Canada for a scholarship. Thanks are also due to Yvon Houle and Luce Dubé of INRS- Géoressources for drafting the figures.
ALCOCK, F. J. 1935. Geology of Chaleur Bay region. Geological Sur- vey of Canada, Memoir 183.
AYRTON, W. G. 1967. Chandler - Port Daniel area. Quebec Depart- ment of Natural Resources, GR 120.
AYRTON, W. G., BERRY, W. B. N., BOUCOT, A. J., LAJOIE, J., LES- PÉRANCE, P. J., PAVLIDES, L., and SKIDMORE, W. B. 1969. Lower Llandovery of the northern Appalachians and adjacent regions. Geological Society of America Bulletin, 80: 459-484.
BÉLAND, J., HUBERT, C., DUCHARME, D., THEBERGE, R., and VENNAT, G. 1979. Un segment de l'anticlinorium d'Aroostook- Percé en Gaspésie, Québec. Geological Association of Canada, Program with Abstracts, 4: 39.
BERNARD, D., and ST-JULIEN, P. 1986. Analyse structurale du Siluro- Dévonien du centre de la Gaspésie et du Carbonifère du sud et de l'est de la Gaspésie. Quebec Department of Energy and Resources, MB 86-36.
BERRY, W. B. N., and Bouco~, A. J. 1970. Correlation of the North American Silurian rocks. Geological Society of America, Special Paper 102.
BOLTON, T. E. 1981. Ordovician and Silurian biostratigraphy, Anti- costi Island, Québec. In Field meeting, Anticosti-Gaspé, 1981. Vol. II: Stratigraphy and paleontology. Edited by P. J. Lespérance. IUGS Subcommission on Silurian Stratigraphy and Ordovician- Silurian Boundary Working Group, Département de géologie, Uni- versité de Montréal, Montréal, Que., pp. 41 -59.
BOURQUE, P. A. 1975. Lithostratigraphic framework and unified nomenclature for Silurian and basal Devonian rocks in eastern Gaspé Peninsula, Québec. Canadian Journal of Earth Sciences, 12: 858-872.
1977. Silurian and basal Devonian of northeastern Gaspé Peninsula. Quebec Department of Natural Resources, ES 29.
BOURQUE, P. A., and GOSSELIN, C. 1986. Stratigraphie du Silurien et du Dévonien basal de la Gaspésie, Québec. Quebec Department of Energy and Resources, MB 86-34.
BOURQUE, P. A., and LACHAMBRE, G. 1980. Le Silurien et le Dévonien basal du sud de la Gaspésie. Quebec Department of Natural Resources, ES 30.
BOURQUE, P. A., BRISEBOIS, D., and Mau>, M. In press. Middle Paleozoic rocks of Quebec and adjacent New Brunswick. In The
CLARKE, J. M. 190g: Éarly Devonic history of New York and eastern North America. New York State Museum of Natural History, Memoir 9.
COOPER, G. A., and KINDLE, C. H. 1936. New brachiopods and trilo- bites from the Upper Ordovician of Percé, Québec. Journal of Pale- ontology, 10: 348 -372.
CRICKMAY, G. W. 1932. Evidence of Taconic orogeny in the Mata- pedia Valley, Quebec. American Journal of Science, 24: 368 -386.
DE BROUCKER, G. 1986. Evolution tectonostratigraphique de la bou- tonnière Maquereau -Mictaw (Cambro-Ordovicien) , Gaspésie, (Québec). Ph.D. thesis, Université Laval, Québec, Que.
DE BROUCKER, G., and RIVA, J. 1985. Age and stratigraphy of the Mictaw Group, southern Gaspé Peninsula. Canadian Paleontology and Biostratigraphy Seminar, Université Laval, Québec, Que., Pro- gram with Abstracts.
DOUGLAS, R. J. W., compiler. 1969. Geology and mineral resources of Canada. Part C. Geological Survey of Canada, Map 1250-A.
DUCHARME, D. 1979. Pétrographie du flysch de l'ordovicien supé- rieur et du Silurien inférieur-anticlinorium d'Aroostook-Percé, Gaspésie, Québec. M.Sc. thesis, Université de Montréal, Mon- tréal, Que.
GAUTHIER, L. 1986. Analyse stratigraphique et structurale de I'anti- clinorium dlAroostook-Percé, au nord de Port-Daniel. M.Sc. thesis, Université d~ Montréal, Montréal, Que.
GOSSELIN, C. 1984. Evaluation du potentiel minéral des cantons de Power et Joncas, Gaspésie. Quebec Department of Energy and Resources, 84 DP-49.
1985. Géologie de la région de Maria, Gaspésie. Quebec Department of Energy and Resources, 85 MB-01.
GOSSELIN, C., and SIMARD, M. 1983. Evaluation du potential minéral de la région de Nouvelle. Quebec Department of Energy and Resources, DP 83-13.
HAMILTON-SMITH, T. 1970. Stratigraphy and structure of Ordovician and Silurian of the Siegas area, New Brunswick. Mineral Resources Branch, New Brunswick Department of Natural Resources, Report of Investigation 12.
1980. Stratigraphy and sedimentology of the Siegas Forma- tion (early Llandovery) of northwestem New Brunswick. In The geology of northeastern Maine and neighboring New Brunswick (guidebook). Edited by D. C. Roy and R. S. Naylor. 72nd Annual Meeting of the New England Intercollegiate Geological Confer- ence, Presque Isle, ME, pp. 1-21.
KINDLE, C. H. 1936. A geologic map of southeastern Gaspe. The Eastern Geologist, 1: 1 - 8.
KIRKWOOD, D. 1986. Géologie structurale de la région de Percé, Gaspésie. M.Sc. thesis, Université de Montréal, Montréal, Que.
LACHANCE, S. 1974. Région de l'Ascension-de-Patapédia, comté de Bonaventure. Quebec Department of Natural Resources, DP-273.
1975. Région de Saint-François-d'Assises, comté de Bona- venture. Quebec Department of Natural Resources, DP-328.
1977. Région de Saint-Alexis-de-Matapédia, comté de Bona- venture. Quebec Department of Natural Resources, DPV-458.
1979. Géologie de la région de Saint-André-de-Restigouche, comté de Bonaventure. Quebec Department of Natural Resources, DPV-667.
LESPÉRANCE, P. J. 1968. Ordovician and Silurian trilobite faunas of the White Head Formation, Percé region, Québec. Journal of Pale- ontology, 143: 81 1 -826.
1974. The Himantian fauna of the Percé area (Québec) and the Ordovician-Silurian boundary. American Journal of Science, 274: 10-30.
1985. Faunal distributions across the Ordovician-Silurian boundary, Anticosti Island and Percé, Québec, Canada. Canadian Journal of Earth Sciences, 22: 838 - 849.
LESPÉRANCE, P. J., and LETENDRE, J. 1981. Phacopid trilobites of the Anticostian Series of Anticosti Island and of the Matapédia Group
Can
. J. E
arth
Sci
. Dow
nloa
ded
from
ww
w.n
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com
by
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/11/
14Fo
r pe
rson
al u
se o
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in Gaspé (Québec). In Field meeting, Anticosti-Gaspé, 1981. Vol. II: Stratigraphy and paleontology. Edited by P. J. Lespérance. IUGS Subcommission on Silurian Stratigraphy and Ordovician- Silurian Boundary Working Group, Département de géologie, Uni- versité de Montréal, Montréal, Que., pp. 197 - 209.
LESPÉRANCE, P. J., and SHEEHAN, P. M. 1976. Brachiopods from the Hirnantian stage (Ordovician-Silurian) at Percé, Québec. Paleon- tology, 19: 719-731.
LESPÉRANCE, P. J., and TRIPP, R. P. 1985. Encrinurids (Trilobita) from the Matapédia Group (Ordovician), Percé, Québec. Canadian Journal of Earth Sciences, 22: 205 -213.
LESPÉRANCE, P. J., SHEEHAN, P. M., and SKIDMORE, W. B. 1981. Correlation of the White Head and related strata of the Percé region. In Field meeting, Anticosti-Gaspé, 1981. Vol. II: Strati- graphy and paleontology. Edited by P. J. Lespérance. IUGS Sub- commission on Silurian Stratigraphy and Ordovician-Silurian Boundary Working Group, Département de géologie, Université de Montréal, Montréal, Que., pp. 223-229.
LESPÉRANCE, P. J., MAU), M., SHEEHAN, P. M., and SKIDMORE, W. B. 1987. A stratigraphical and faunal revision of the Ordo- vician-Silurian strata of the Percé area, Québec. Canadian Journal of Earth Sciences, 24: 117- 134.
MAU), M. 1979. L'axe Aroostook-Matapédia au nord de Chandler, Gaspésie, Québec. M.Sc. thesis, Université Laval, Québec, Que.
1 9 8 6 ~ . Stratigraphie et structure de I'anticlinorium d'Aroo- stook-Percé en Gaspésie, Québec. Ph.D. thesis, Université de Montréal, Montréal, Que.
1986b. L'Anticlinorium d'Aroostook-Percé au nord de New- Richmond. Quebec Department of Energy and Resources, MB 86-33.
1987. L'anticlinorium dlAroostook-Percé au nord d'Escu- minac. Quebec Department of Energy and Resources, MB 87-35.
In press a. Stratigraphie et structure de l'anticlinorium d'Aroostook-Percé au nord de la faille du Grand Pabos, régions de Chandler et de Grande Rivière, Gaspésie. Quebec Department of Energy and Resources, ET 87-06.
In press b. Stratigraphie et structure de I'anticlinorium d'Aroostook-Percé au sud de la faille du Grand Pabos, cantons de Garin, Honorat, Weir et Raudin, Gaspésie. Quebec Department of Energy and Resources.
MALO, M., and BÉLAND, J. 1985. Évolution structurale du segment oriental de l'anticlinorium d'Aroostook-Percé, Gaspésie, Québec. Geological Association of Canada, Program with Abstracts, 10: A37.
MARTIN, F. 1980. Quelques Chitinozoaires et Acritarches ordoviciens supérieurs de la Formation de White Head en Gaspésie, Québec. Canadian Journal of Earth Sciences, 17: 106- 119.
MCGERRIGLE, H. W. 1946. A revision of the Gaspé Devonian. Trans- actions of the Royal Society of Canada, 3th Series, Section IV, XL: 41 -54.
1950. The geology of eastern Gaspé. Quebec Department of Mines, GR 35.
NEUMAN, R. B. 1984. Geology and paleobiology of islands in the Ordovician Iapetus Ocean: review and implications. Geological Society of America Bulletin, 95: 1188 - 1201.
NOWLAN, G. S. 1981. Late Ordovician - Early Silurian conodont biostratigraphy of the Gaspé Peninsula-a preliminary report. In Field meeting, Anticosti-Gaspé, 1981. Vol. II: Stratigraphy and paleontology. Edited by P. J. Lespérance. IUGS Subcommission on Silurian Stratigraphy and Ordovician-Silurian Boundary Working Group, Département de géologie, Université de Montréal, Mon- tréal, Que., pp. 257-291.
1983a. Biostratigraphic, paleogeographic, and tectonic impli- cations of Late Ordovician conodonts from the Grog Brook Group, northwestern New Brunswick. Canadian Journal of Earth Sciences, 20: 651-671.
19836. Early Silurian conodonts of eastern Canada. Fossils and Strata, 15: 95 - 110.
PAVLIDES, L. 1968. stratigraphic and facies relationship of the Carys
Mills Formation, northeast Maine adjoining New Brunswick. United States Geological Survey, Bulletin 1264.
PAVLIDES, L., MENCHER, E., NAYLOR, R. S., and Boucm, A. J. 1964. Outline of the stratigraphic and tectonic features of northeast- ern Maine. In Geological Survey research 1964. United States Geo- logical Survey, Professional Paper 501-C, pp. C28 -C38.
PETRYK, A. A. 1981. Stratigraphy, sedimentology and paleogeo- graphy of Upper Ordovician - Lower Silurian of Anticosti Island, Québec. In Field meeting, Anticosti-Gaspé, 1981. Vol. II: Strati- graphy and paleontology. Edited by P. J. Lespérance. IUGS Sub- commission on Silurian Stratigraphy and Ordovician-Silurian Boundary Working Group, Département de géologie, Université de Montréal, Montréal, Que., pp. 11 - 39.
PICKERILL, R. K. 1980. Phanerozoic flysch trace fossil diversity - observations on an Ordovician flysch ichnofauna from the Aroo- stook-Matapédia Carbonate Belt of northern New Brunswick. Canadian Journal of Earth Sciences, 17: 1259 - 1270.
RAST, N., and STRINGER, P. 1980. A geotraverse across a deformed Ordovician ophiolite and its Silurian cover, northern New Bruns- wick, Canada. Tectonophysics, 69: 221 -245.
RICKARDS, R. B., and RIVA, J. 1981. Glyptogruptus persculptus? (Salter), its tectonic deformation, and its significance for the Carys Mills Formation of N.E. Maine, U.S.A. Geological Journal, 16: 219-235.
RIVA, J. 1974. A revision of some Ordovician graptolites of eastern North America. Paleontology, 17: 1 -40.
1981. Graptolites from the Matapédia and Honorat groups of Gaspé. In Field meeting, Anticosti-Gaspé, 1981. Vol. II: Strati- graphy and paleontology. Edited by P. J. Lespérance. IUGS Sub- commission on Silurian Stratigraphy and Ordovician-Silurian Boundary Working Group, Département de géologie, Université de Montréal, Montréal, Que., pp. 293-298.
RIVA, J., and MALO, M. 1988. Age and correlation of the Honorat Group, southern Gaspé Peninsula. Canadian Journal of Earth Sciences, 25. (In press.)
SANSCHAGRIN, R. 1963. Preliminary report on Grande-Rivière, Gaspé - South County. Quebec Department of Natural Resources, PR 487.
SCHUCHERT, C., and COOPER, G. A. 1930. Upper Ordovician and Lower Devonian stratigraphy and paleontology of Percé, Québec. American Journal of Science, 20: 16 1 - 176.
SHEEHAN, P. M., and LESPÉRANCE, P. J. 1979. Late Ordovician (Ash- gillian) brachiopods from the Percé region of Québec. Journal of Paleontology, 53: 950 -967.
1981. Brachiopods from the White Head Formation (Late Ordovician - Early Silurian) of the Percé region, Québec, Canada. In Field meeting, Anticosti-Gaspé, 1981. Vol. II: Stratigraphy and paleontology. Edited by P. J. Lespérance. IUGS Subcommission on Silurian Stratigraphy and Ordovician-Silurian Boundary Working Group, Département de géologie, Université de Montréal, Montréal, Que., pp. 247 -256.
SIMARD, M. 1986. Géologie et évaluation du potentiel minéral de Carleton. Quebec Department of Energy and Resources, ET 84-1 1.
SKIDMORE, W. B. 1965. Honorat-Reboul area. Quebec Department of Natural Resources, GR 107.
1967. The Taconic unconformity in the Gaspé Peninsula and neighbouring regions. In Appalachian tectonics. Edited by T. H. Clark. Royal Society of Canada, Special Publication 10, pp. 26- 32.
SKIDMORE, W. B., and LESPÉRANCE, P. J. 1981. Percé area, the White Head Formation. In Field meeting, Anticosti-Gaspé, 1981. Vol. 1: Guidebook. Edited by P. J. Lespérance. IUGS Subcommission on Silurian Stratigraphy and Ordovician-Silurian Boundary Working Group, Département de géologie, Université de Montréal, Mon- tréal, Que., pp. 31 -40.
SKIDMORE, W. B., and MCGERRIGLE, H. W. 1967. Geologic map, Gaspé Peninsula, Québec. Quebec Department of Natural Resources, Map 1642.
ST. PETER, C. J. 1977. Geology of parts of Restigouche, Victoria and
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Madawaska counties, northwestern New Brunswick. Minera1 cross-laminations, convolute laminations, and slumps. Resources Branch, New Brunswick Department of Natural [200 m] Resources, Report of Investigation 17. Arsenault Formation
(1) Greenish grey fine- to coarse-grained lithic wacke in beds 5 -20 cm thick, interbedded with olive-green claystone;
Appendix coarse-grained to very coarse grained to microconglomeratic The following descriptions of the Arsenault and Garin for- beds of 10-20 cm; minor interbeds of fine-grained tuff.
mations come from the type localities of these units, which are [ 2 600 m exposed] in the original type area-of the Honorat Group of Skidmore (1967). The description of the Pabos Formation comes from (C) Pabos Formation
The principal reference section is located along the Grande a reference locality of the unit that is farther north of the type area of Kindle (1936). The thicknesses of the units are approx- Rivière Ouest, to the north of the anticlinorial structure
imate and are measured on the structural cross section. formed by the Garin Formation (Honorat Group) (Fig . 5). The lower contact with the Garin Formation can be seen in the
(A) Arsenault Formation The stratotype unit of the Arsenault Formation is located in
a northerly trending brook that runs from Arsenault Lake to the Grand Pabos fault (Fig. 4). The description of the lithology present in this book is representative of the formation, which is quite homogeneous.
Greenish grey medium- to coarse-grained lithic wacke in 10-30 cm thick beds (50%); greenish grey siltstone to fine- grained sandstone in 5-10 cm thick beds (20%); grey to olive-green clayslate and grey to greenish grey mudstone in 2-5 cm thick beds, sometimes laminated (30%). Minor
river; continuing north, the Pabos Formation, with a north- easterly trend, dips gently to the northwest and to the south- east. The White Head Formation crops out to the north of this area, and the gradational contact with this upper unit can be obsemed at two places: (1) on the Pabos Road and (2) in the Petit Pabos River (Fig. 5). The description of the principal reference section is not given metre by metre because the sec- tion measures more than 7 km and is affected by folding (Fig. 5). Four assemblages of the Pabos Formation (units 2, 3 ,4 , and 5 of Fig. 5) can be recognized in the section and are described in descending order: -
amount of very fine grained calcareous sandstone in 2 - 5 cm thick beds. White Head Formation (Pabos Road)
(6) Calcilutite in regular beds of 5 -6 cm interbedded with (B) Garin Formation calcareous mudstone beds of 1-2 cm.
The stratotype unit of the Garin Formation is located in a Pubos Formation-upper member (Pubos and small brook trending north. This brook is a tributary of the Rivière Ouest) Garin River to the south (Fig. 4). The base of the section starts (5) Argillaceous and silty light grey laminated limestone in UPstream, where the brook cari be reached by the Mer Road 10 cm thick beds. calcilutite in 3 -5 cm beds represents (Fig . 4). The description of the formation comprises four units 20 - 30% of the unit. Presence of slumps and bioturbation. (2-5, Fig. 4) and is in descending order: [350 ml
Pabos Formation (Garin River) (Grande Rivière Ouest) (6) Dark grey mudstone (50%) in 10-20 cm thick beds; (4) Grey to beige calcareous mudstone in 10 cm thick beds
light grey to beige (40%) in 3-4 cm interbedded with dark grey noncalcareous mudstone beds 2- thick beds; calcilutite (10%) in 2-4 cm thick beds. 5 cm thick. Light grey laminated calcareous siltstone, in
Garin Formation (small south-jlowing brook) (5) Dark grey to greenish mudstone with brown, calcare-
ous, millimetre-scale laminae; light grey silty limestone (10%) in 3-4 cm thick beds. [500 ml
(4) Dark grey to greenish mudstone and siltstone with milli- metre-scale larninae (50%); siltstone to fine-grained sandstone (25 %), grey greenish in 10 - 15 cm thick beds with parallel and cross-laminations, slumps, and convolute laminations; medium- to coarse-grained greenish grey sandstone (15%), sometimes calcareous, in 10-20 cm thick beds, with parallel and cross-laminations, load casts, graded bedding; light grey conglomerate (10%) in 5-30 cm thick beds, with quartz pebbles. [400 ml
(3) Polymictic conglomerate (25 m thick) containing lithic sandstone, calcareous laminated sandstone, fine-grained cal- careous sandstone with cross-laminations, silty limestone, calcilutite, dark grey mudstone, fine- to medium-grained grey laminated sandstone, and dark green medium-grained igneous rock; dark grey laminated mudstone and siltstone; medium-thick and graded-bedded lithic and feldspathic wacke.
[IO0 ml (2) Dark greenish grey massive siltstone and dark grey
mudstone with silty laminae; greenish grey siltstone, some- times calcareous, in 5-8 cm thick beds with parallel and
10 cm thick beds. Some zones of polymictic conglomerate beds 50- 100 cm thick. Presence of chlorite schist pebbles in the mudstone and some slumps. [500 ml
(3) Calcareous laminated mudstone, grey to greenish grey on weathered surface, in beds 10-20 cm thick. Fine to medium calcareous sandstone in 10-30 cm thick beds with sedimentary structures (graded bedding, parallel and cross- laminations, and convolute bedding). Light grey calcareous siltstone in 4 -8 cm thick beds. Some zones of polymictic con- glomerate in 50- 100 cm thick beds. Some beds of laminated argillaceous limestone 5 - 10 cm thick. Presence of slumps.
[250 m]
Pabos Formation-lower member (Grande Rivière Ouest) (2) Light brown to grey calcareous larninated mudstone in
5 - 10 cm thick beds interbedded with dark grey noncalcareous mudstone in 4-8 cm thick beds. Presence of slumps.
[300 m]
Garin Formation-Honorat Group (Grande Rivière Ouest) (1) Dark grey massive mudstone in 10-20 cm thick beds
interbedded with dark grey mud shale in 1-2 cm thick beds and some light grey calcareous limestone beds 2 -4 cm thick. Some silty dolomitic limestone, grey to brown, in 4-5 cm thick beds.
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