Lower Cretaceous and Jurassic rocks of McDougall Pass area and some adjacent areas of north-central Richardson Mountains, northern Yukon Territory and northwestern District of Mackenzie, N.W.T. (NTS-116P/09 and 116P/10): a reappraisal
Authors: Jeletzky J A 
Published: March 2017

Jurassic and Lower Cretaceous rocks of the Mc Dougall Pass area of north-central Richardson Mountains include (ascending order): a. The 70 to 100 m thick, shallow marine Bug Creek Sandstone of mid-Bajocian to ?early Callovian age. b. ? Mid-Callovian to Berriasian
Husky Formation which is completely developed, open marine but thin (98-137 m) and largely argillaceous in the northeastern part of the area. In the southwest the Husky is, in contrast, largely arenaceous and 335 to 900 m thick in spite of the absence of its upper part. This Arenaceous facies
consists of (ascending order): b1. Prodeltaic, shallow marine Lower marine member; b2. Deltaic to alluvial Mount Millen Member (new); and b3 . Postdeltaic, open marine Upper marine member which is only preserved in the extreme southwestern corner of the area. The presence of 25 to 60 km wide belts
of contemporary marine facies east, west, and south of the high constructive Little Bell deltaic lobe (new) of Mount Millen Member indicates its derivation from a northern source area. This presumably cordillera-like White Island (new) apparently was confined between McDougall Pa ss in the south,
headwaters of Cache Creek in the north, upper Bell River in the west and the eastern flank of White Mountains in the east. White Island appears to be the previously unrecognized Late Jurassic generation of the Cache Creek Uplift which is re-interpreted as a westward-tilted, north-trending horst. The
above described facies pattern of the Husky Formation was controlled by the Late Jurassic movements of this horst and the flanking grabens. c. The Late Hauterivian to Late Barremian Upper shale-siltstone division overlaps the Husky Formation disconformably and probably regionally discordantly. The
normally intervening Lower sandstone and Coal-bearing divisions are absent by nondeposition. The area evidently formed part of strongly uplifted crestal zone of the Rat Uplift of Aklavik Arch from the early Valanginian to mid-Hauterivian. The Lower member of Upper shale-silstone division is
represented by about 610 m thick Arenaceous facies (= southern facies) in the northeastern part of the area. This facies extends southeastward into the Stony Creek - Vittrekwa River area and northward into the White Mountain area. It appears to be a northwest-trending belt of shoals and barrier
islands derived from the Barrier River - Stony Creek deltaic lobe (new) by a northward-flowing current which was reworking its western flank. The Arenaceous facies grades laterally into entirely argillaceous, open marine Shelf facies (formerly eastern facies) . The latter outcrops in the
southwestern corner of the area (and farther west in Bell Ba sin) and to the east in the Canoe Depression. The Arenaceous f acies of Upper shale-siltstone division was deposited on top of the previously unrecongized late Hauterivian to ?earliest Barremian generation of the Cache Creek Horst. This
horst continued to separate the main trough of the Richardson Mountains - Porcupine Plain Aulacogene situated immediately to the west from the structurally negative fault block of the Canoe Depression situated to the east. The 195 to 260 m thick Upper member of Upper shale- siltstone division is
represented largely by argillaceous, commonly flysch-like, predominantly neritic rocks. This member does not exhibit any major facies changes in north-central Richardson Mountains evidently because of a far reaching bevelling and subsidence of the whole area in the Barremian. d. Only small, 15.5 to
100 m thick erosional remnants of the Upper sandstone division occur in the Mc Dougall Pass area. These shallow marine rocks do not exhibit major facies changes anywhere in north-central Richardson Mountains. Therefore the whole area must have remained tectonically inactive in the early
Aptian.