The term Racklan orogeny has been used over time to refer to different unconformities and folding
events. In this paper, we will use it to refer to uplifting and folding events between the deposition of
the Wernecke Supergroup and the Pinguicula Group as seen in the Wernecke Mountains.
In 1954, Wheelers first recorded the presence of an angular unconformity in the area around North
Racklan River and Pinguicula Creek. The name Racklan Orogeny was introduced by Gabrielse in
1967. He loosely defined it as the uplifting, folding and block faulting of the 'Purcell-like' rocks
bringing to an end the Proterozoic miogeosynclinal sedimentation in the eastern part of the northern
Cordillera (Gabrielse, 1967). The type area for the Racklan Orogeny was subsequently defined by
Eisbacher in 1978 as the angular unconformity between the Wernecke Supergroup and the
Pinguicula Group in the northeastern of the Rackla Range (Wernecke Mountains). The term was
then loosely used in the literature either referring to an unconformity  between the Rapitan Group (of
the Ekwi Supergroup)  and the Pinguicula Group or the unconformity between the Gillespie Lake
Group (of the Wernecke Supergroup) and the Pinguicula Group. Yeo et al., 1978 suggested the
introduction of Nadaleen orogeny to refer to the unconformity between the Gillespie Lake Group
and the Pinguicula Group and that the Racklan orogeny would refer to the unconformity between the
Rapitan Group and the Pinguicula Group. Young et al., 1979, then suggested that the term Racklan
orogeny refers exclusively to the "event recorded in the Rackla River area (that is, the disturbance
between the Wernecke Supergroup and the Pinguicula Group)" and introduced the term Hayhook
orogeny for later tectonic event. The name Corn Creek orogeny was introduced by Thorkelson
(2000) to differentiate between compresional (Corn Creek orogeny) and extensional (Hayhook
extension) events between the Hematite Group (formally unit D-F of the Pinguicula Group
(Thorkelson, 2000)) and the Rapitan Group.
 

Regional Correlation

This paper supports the Racklan orogeny being correlated with the Forward orogeny (Cook, D.G.
and MacLean, 1995) in the Coppermine Homocline region and with the Fifteenmile orogeny
(Mercier, 1989) in the Coal Creek Dome region of the Ogilvie Mountains. This suggests that these
orogenies can be correlated over a distance of a 1000 km and that they represent a major event in
the Paleoproterozoic.

The timing of the Racklan orogeny has always been the obstacle to any rigorous correlation. In
1967, Gabrielse first suggested that "the low-grade regional metamorphism of argillaceous rocks in
Ogilvie, Richardson, and northern Wernecke Mountains" could be correlative. Correlations of the
Racklan orogeny with the East Kootenay orogeny were once very appealing (Monger et al., 1972;
Stewart, 1976; Yeo et al., 1978). The two are now thought (Young et al., 1979; Hoy, 1992;
Thorkelson and Wallace, 1994; Abbott et al, 1997) to represent two separate events on the basis of
field relation with rocks of known ages.

F.A. Cook and his research associates (Cook, F.A., 1992; 1990; 1988a,b; Cook, F.A. and Taylor,
1991; Clark and Cook, F.A., 1991; Sevigny et al., 1991; Cook et al., 1992; Dredge Mitchelmore
and Cook F.A., 1994) studied extensively the subsurface geology of the Northwest Territories.
Their research consisted mainly of interpretation of geophysical reflection survey, but it also included
a few drill hole controls (Sevigny et al., 1991). They described deformation structures that could be
seen in the subsurface and suggested that they were correlative to the Racklan orogeny as seen in the
Wernecke Mountains (Cook, F.A., 1992; 1988a,b, Sevigny et al, 1991; Dredge Mitchelmore and
Cook, F.A., 1994).

Knowledge of the stratigraphy of northern Canada has been refined since 1994. Rainbird et al.,
(1994) proposed revision of the nomenclature in the Amundsen Basin wherein they suggested that all
of the groups and formations that were part of the sequence B (from Young et al., 1979) and found
in the Amundsen Basin be included in the Shaler Supergroup (Rainbird et al., 1994). The Shaler
Supergroup was then divided in two. The lower part of it was given the name Rae Group and the
upper part was given the name Reynolds Point Group (Rainbird et al, 1994). In 1995, D.G. Cook
and MacLean proposed that the Dismal Lakes Assemblage seen in the Colville (Anderson Hills) was
correlative with the Dismal Lakes Group seen in the Coppermine Homocline area. The unconformity
between the Hornby Bay Group and the Dismal Lakes Group that had been recognised in the
Homocline area by F.A. Cook (1988a) was later thought to represent a significant event of uplift,
deformation and erosion that was termed the Forward orogeny (Cook, D.G. and MacLean, 1995;
Cook, D.G. and Mayers, 1990). A possible correlation between the Forward orogeny and the
Racklan orogeny was suggested (Cook, D.G. and MacLean, 1995) with the limitation that the age
of the Racklan orogeny was not well constrained. Thorkelson et al., (1998) later supported this
hypothesis when they got a better control the age of the Racklan orogeny in the Wernecke
Mountain. Rainbird et al., (1996) correlated the upper units of the Pinguicula group (of the Eastern
Ogilvie and Wernecke Mountains) with the Mackenzie Mountains Supergroup (of the Mackenzie
Mountains). Their correlation was based on detrital zircon U/Pb isotope data from quartzarenites
collected in those regions (Rainbird et al, 1997). D.G. Cook and MacLean (1992) and later
Thorkelson et al., (1998) suggested that the Dismal Lakes Group and the Dismal Lakes Assemblage
(Northwest Territories) were correlative with the lower part of the Pinguicula Group and the units
R1-R4 of the Lower Fifteenmile Group. The unit D-F of the Pinguicula Group in the Wernecke
Mountains has been separated into its own group called the Hematite Group by Thorkelson (2000).
Only the Hematite Group is now thought to be correlative to the lower Mackenzie Mountains
Supergroup in the Mackenzie Mountains and to the Shaler Group in the Coppermine Homocline
region (Ross et al., 2001; Thorkelson, 2000). Breccia bodies are not thought to be present in the
Fifteenmile and Pinguicula Group anymore (Thorkelson et al., 1998). The Nor Breccia dated to
1267±40 Ma by Parrish and Bell (1987) is considered by Thorkelson et al. (2001b) to be part of a
localized hydrothermal reactivation to the Wernecke Breccia, which is dated around Slab Mountain
to 1600 Ma (U-Pbtitanite) (Thorkelson et al., 2001b).

In 1998, Villeneuve et al. reported having extracted Greville-age zircons (ca. 1000 Ma) from the
lowermost two units of the Proterozoic sedimentary section exposed at Cap Mountain in the Interior
Plains (Northwest Territories). This changed the previous correlation with the Hornby Bay Group
(Aitken and Pugh, 1984) to an unresolved relation with the Mackenzie Mountains Supergroup and
the Shaler Group (Villeneuve et al., 1998). This was supported by Samuelson et al. (2001) who
found Neoproterozoic fossils in outcrop at Cap Mountain. These findings were important because
they challenged what Dredge Mitchelmore and Cook (1994) established in their paper. The Cap
Mountain study area cannot support the presence in outcrop of Dismal Lakes or Hornby Bay Group
westward of the Coppermine region anymore. The Cap Mountain study area cannot support the
theory that all of Sequence A (of Young et al, 1979) thicken westward and represent a Proterozoic
miogeocline.
With all this new data available, the deformation event following the deposition of the Dismal Lakes
and Hornby Bay groups that F.A. Cook and associates described in their papers represents a
younger event than the Racklan orogeny. This was also the conclusion that Thorkelson et al. (1998)
reached.

The Ogilvie Mountains are located about 300 km to the East of the Wernecke Mountains. Several
unconformities have been recorded in the Ogilvie Mountains (Thompson and Roots, 1982) and
correlation of the Wernecke Supergroup assemblage with the Paleoproterozoic rocks seen in the
Ogilvie Mountains is generally accepted (Mercier, 1989; Cook and MacLean, 1995; Rainbird et al.,
1996; Abbott et al., 1997, Thorkelson et al., 1998, Thorkelson, 2000; Ross et al., 2001). Mercier
(1989) studied weakly metamorphosed rocks in the Coal Creek Dome area of the Ogilvie
Mountains. He gave the name Fifteenmile orogeny to the event responsible for those deformations
structures (Mercier, 1989). He also suggested that the Fifteenmile orogeny could be correlative with
the Racklan orogeny as seen in the Wernecke Mountains (Mercier, 1989). In the Upper Hart River
Area of the Eastern Ogilvie, Abbott (1997) could not see conclusive evidence of the Racklan
orogeny, however, he saw parts of large-scale features that he thought could be related to the
Racklan orogeny (Abbott, 1997).
 

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