|
|
|
Cretaceous (T. Hadlari)
|
Cretaceous rocks in the southern Peel region at the front of the Mackenzie Mountains are sub-divided into Martin House, Arctic Red, and Trevor formations (Mountjoy and Chamney, 1969; Yorath and Cook, 1981). These formations represent a basal transgressive sandstone, marine mudstone, and an upper sandstone, respectively, composing a stratigraphic section 2000 metres thick.
Field work was conducted in the summer of 2006 and 2007 in the Snake River (NTS 106 F), Upper Ramparts River (NTS 106 G), and Sans Sault Rapids (NTS 106 H) map sheets.
Sections were measured along Flyaway, monument, and Shortcut creeks and Cranswick, Hume, Mountain, and Imperial rivers.
Martin House Formation of Peel Plateau and Plain region is a composite marine sandstone, including mudstone intervals. The Formation is 10 to 50 m thick and unconformably overlies the Late Devonian Imperial Formation.
Martin House Formation is subdivided into three facies. 1) Mudstone facies record deposition in an offshore environment. 2) Complexly cross-stratified sandstone facies contain hummocky and swaley cross-stratification representing a wave-dominated lower to upper shoreface environment. 3) Cross-stratified, strongly bioturbated sandstone facies record upper shoreface deposition in a wave and possibly tide influenced setting devoid of major storm events.
The overall facies succession of Martin House Formation is transgressive, from upper shoreface through lower shoreface to offshore. There is a lateral facies change shoreward from east to west indicated by sedimentary structures, thickness, and occurrence of sandstone bodies.
Preliminary sedimentology of Martin House Formation is available within NTGO Open Report 2007-010.
Arctic Red Formation is a marine mudstone unit that reaches up to a kilometre in thickness (measured on Hume River). It gradationally overlies the Martin House Fm. In the eastern part of the field area, including Hume River, the formation comprises mudstone with rare, thin sandstone beds, interpreted as distal storm deposits. There is a shoreward facies transition westward and up to 5 m thick shoreface sandstone bodies are intercalated with much thicker intervals of offshore mudstone, such as at Sans Sault Rapids, Mountain River, and Imperial River.
More than 700 m of Trevor Formation is outcropped along Hume River. Trevor Formation gradationally overlies the mudstone of the Arctic Red Fm and consists of a series of storm-dominated offshore to middle shoreface parasequences:
A) Trevor Formation is subdivided into four facies: mudstone; interbedded sandstone and mudstone; amalgamated hummocky cross-stratified (HCS) sandstone; and parallel-laminated sandstone. Mudstone facies is composed of poorly indurated mudstone, siltstone, and very minor sandstone interpreted as offshore deposits. Interbedded sandstone and mudstone facies contains storm beds of HCS, parallel lamination and combined flow ripples that alternate with interlaminated mudstone and ripple cross-laminated sandstone. Interbedded facies is interpreted as transitional to lower shoreface. Superimposed storm deposits of HCS swaley cross-stratified sandstone (SCS)and parallel laminated very fine to fine grained sandstone comprise the amalgamated sandstone facies, interpreted as middle shoreface. Parallel laminated sandstone facies is dominated by horizontal parallel lamination with minor scours. The association of horizontal parallel lamination in fine to medium-grained sandstone is interpreted to represent a storm-dominated upper shoreface.
B) Trevor Formation parasequences, 20-60 m thick, are bounded by flooding surfaces commonly associated with a transgressive lag. A typical upward-coarsening succession is from mudstone, through interbedded sandstone and mudstone, to amalgamated sandstone facies. Associated HCS increases in wavelength from small (10-30 cm) to large scale (1-3 m).
Sedimentology of the Trevor Formation is contained within NTGO Open Report 2006-008.
Danielle Thomson (dthomso2@connect.carleton.ca) is working on a Master’s thesis at Carleton University under supervision of Prof. Claudia Schroder-Adams. Her research is focused on biostratigraphy of Foraminifera and will provide much needed age constraints on the Martin House, Arctic Red, and Trevor formations.
|
Photo gallery
|
|
Diplocraterion burrow from the base of the Martin House Formation. |
|
|
Humocky cross-stratification from upper Martin House Formation |
|
|
|
Martin House Formation outcrop at Imperial River. Note three sandstone units. |
|
|
Swale bedform from upper Trevor Formation |
|
|
|
Small-scale HCS overlain by ripple cross-lamination. Lower shoreface interbedded sandstone and mudstone facies, Trevor Formation, Hume River. |
|
|
3-d ripples in the foreground. HCS bedforms with 1.5 m wavelength in the background (near the flowers). Middle shoreface amalgamated sandstone facies, Trevor Formation, Hume River. |
|
|
|
|
|
|
Lower shoreface interbedded sandstone and mudstone capped by a transgressive lag overlain by mudstone. This forms the top of a parasequence near the base of the Trevor Formation, Hume River. |
|
|
A section of alternating shoreface sandstones and offshore mudstones of the Trevor Formation at Cranswick River. Helicopter for scale. |
|
|
|
|
|
|
Outputs
|
|
Hadlari et al. presented Cretaceous Evolution of a Northern Cordilleran Foreland Basin Inferred from Stratigraphy, Seismic Sections, and Detrital Zircons, Mackenzie Mountains, Canada, a talk at Yellowknife Geoscience Forum November 18-20, 2008.
Thomson et al. presented Foraminiferal Biostratigraphic Framework for the Cretaceous of the Peel Plateau Region, a talk at Yellowknife Geoscience Forum November 18-20, 2008. Contact Danielle Thomson for a copy.
Hadlari, T. and Zantvoort, W.G., 2007. Preliminary shallow marine sedimentology of the Cretaceous Martin House Formation, Peel Plateau and Plain, NWT; Northwest Territories Geoscience Office, NWT Open Report 2007-010, 22 p. Download now.
Sedimentology of Cretaceous wave-dominated parasequences, Trevor Formation, Peel Plateau, NWT; presentation by Hadlari at Yellowknife Geoscience Forum (November 21-23, 2006). Download now.
Hadlari, T., 2006. Sedimentology of Cretaceous wave-dominated parasequences, Trevor Formation, Peel Plateau, NWT; Northwest Territories Geoscience Office, NWT Open Report 2006-008, 16 p. Download now.
|
|
|
|
|
