Franklin Bay and Malloch Hill map-areas, District of Mackenzie
Authors: Yorath C J , Balkwill H R , Klassen R W 
Published: August 2015

Franklin Bay and Malloch Hill map-areas lie mainly within Anderson Plain, a division of the northernmost part of the Interior Plains physiographic region, and partly within the Arctic Coastal Plain. Rocks exposed on Anderson Plain belong to the Ordovician,
Cretaceous and Tertiary Sys t ems; unconsolidated Quaternary sediments mantle bedrock on the Arctic Coastal Plain. The borehole at Elf Horton River G-02 well provides significant information about the subsurface configuration of Paleozoic rocks. The borehole penetrated about 6,300 feet (1,910 rn) of
Paleozoic rocks, ranging from probable Middle Devonian to possible Upper Cambrian. These Paleozoic strata consist mainly of thick intervals of dolomite and limestone and , near the top, some black Devonian shale . From youngest to oldest, the Hare Indian, Hume, Gossage, Mount Kindle, and Franklin
Mountain Format ions can be recognized in this succession. Cretaceous rocks in the region are mainly marine shale and siltstone but, at their base, locally include an interval of fluvial, quart rose sandstone. Lower Cretaceous s t rata overstep progressively older Paleozoic rocks from west to east ;
they lie on probable Middle Devonian rocks in the subsurface at the western margin of the area, and in surface exposures lie on probable Lower Ordovician (or possibly Upper Cambrian) rocks near the eastern margin. New stratigraphic nomenclature is proposed herein for the Cretaceous strata of the
region to replace existing informal nomenclature. The proposed nomenclature is based on surface and subsurface data. Lower Cretaceous strata are termed herein the Darnley Bay Group, consisting of the Langton Bay Formation (possibly Berriasian to Albian), and the Horton River Formation (Middle
Albian). The Langton Bay Formation is divided into a sandstone -dominated Gilmore Lake Member , and a shale-dominated Crossley Lakes Member. Upper Cretaceous rocks are termed the Amundsen Gulf Group, and are separated into the Smoking Hills Formation (probably Santonian to Carnpanian) and the Mason
River Formation (probable l y Campanian and ~ l aastrich tian). A hiatus, representing part of the Albian, the Cenornanian, Turonian, Coniacian , and part of the Santonian Stages, separates the Lower and Upper Cretaceous Series, and is evident in some out crops as a disconforrnity. Sparsely
distributed, thin deposits of unconsolidated sand and gravel (Beaufort Formation), of possible Late Tertiary age, lie on the Cretaceous rocks. Structural elements in Franklin Bay and Mallock Hill map-areas include regional unconformities (most significantly at the base of Upper Ordovician, Devonian,
and Cretaceous successions), broad-limbed folds, and long fracture traces. No large faults or high-amplitude local folds were observed. A broad structural terrace, formed by lower Paleozoic carbonate strata, with outliers of Cretaceous beds, occupies the eastern and central part s of the rnap areas.
Paleozoic and Cretaceous rocks in the western part of the region are part of a westward -dipping homocline , which is interrupted locally by a broad, northeast-trending syncline (herein termed the Ander son Plain Syncline) . Prospective hydrocarbon reservoirs include partly porous intervals in the
Paleozoic succession, and porous sands tones, which are developed locally at the base of the Cretaceous succession. Small amount s of low-grade coal from Lower Cretaceous rocks have been used by the sparse native population for many years.