This unit is named after the city of Utica, New York, where it was first identified (Emmons, 1842). According to Globensky et al. (1993): “The term Utica was used by Emmons (1842) to mean a black shale between the Trenton and Lorraine in the Utica basin in the United States. In Canada, Logan (1863), Ami (1900) and Raymond (1913b) referred to the “Utica shale” as an analogous sequence. Clark (1947) introduced the term “Utica Group”, in which he placed the Lotbinière Formation, located between the Trenton Group and the Leclercville Formation, at the base of the Lorraine. Clark and Globensky (1973) called “Lotbinière” all shales of Utica age in the Portneuf area. Clark and Globensky (1976a), in agreement with the redefinition of the Utica Shale at the type locality in New York State, proposed that the term Lotbinière be restricted to flyschic rocks related to Appalachian sedimentation, and that the name Utica applies to typical shale of platform sedimentation (St. Lawrence Lowlands).”

The current Lotbinière Formation, which belongs to the Sainte-Rosalie Group, is locally overlying the Utica Shale (Globensky, 1987; Lebel and Hubert, 1996; Amortegui et al., 2010; Hubert et al., 2012), for example at the Montmorency Falls in the Quebec City area.

Based on drilling data (logging, mineralogical and geochemical composition), Thériault (2008a, 2008b, 2009, 2012a, 2012b) subdivided the Utica Shale into two separate informal units, the upper Utica Shale and the lower Utica Shale.

The Utica Shale has strong potential for natural gas, as indicated by the numerous drilling performed since the late 1800s (see Thériault, 2012a b).

Shale contains 14-26% carbonate (Belt et al., 1979), while the remaining fraction is a terrigenous mud that originates from Appalachian erosion (Globensky 1987). Some quartz and mica crystals are visible to the naked eye in shale, although they are generally indistinguishable. The abundance of detrital mica gives shale a brighter appearance than limestone (Clark and Globensky, 1975). Shale is very fine grained (probably caused by anoxic dissolution) and is rich in organic matter and graptolites, but may also contain trilobites and cephalopods. These characteristics, combined with the absence of bioturbation, suggest a medium to very deep depositional medium (Belt et al., 1979).

According to Logan et al. (1863), an outcrop (approximate location) along the Sainte-Anne River displays the most complete section of the Utica Shale for almost 96 m, from bottom to top: 

• 5.5 m of black bituminous and fissile shale with indeterminate Lingula, and Graptolithus pristis;
• 2.4 m of black bituminous and fissile shale with two beds of altered yellow limestone, black inside, probably magnesian, suitable for hydraulic purposes;
• 7 m of black bituminous and fissile shale;
• 3.3 m of black bituminous and fissile shale, broken into small fragments due to imperfect cleavage independent of bedding;
• 74.6 m of black bituminous and fissile shale with Graptolithus pristis;
• 1.5 m grey and hard silt, stratified in black shale strips;
• 2.1 m of black bituminous and fissile shale interstratified with silt beds.

Thickness and distribution

Shale can be observed up to NE Ontario, where it corresponds to the Witby Formation, and into New York State (Globensky, 1987). In Quebec, the Utica Shale extends along the north shore of the St. Lawrence River from Quebec City to the south shore of Montreal and deepens towrad the SE to a depth of ~2.5 km along the Logan Line, covering a surface and sub-surface area of ~10 000 km² (Thériault, 2012b).

According to Globensky et al. (1993), “The thickness of the Utica shale remains fairly constant at 30 m in the Quebec City area; it reaches 80 m in Neuville. South of Montreal, in the Saint-Jean-Lacolle area, the thickness of the Utica is estimated at 1300 m. The Utica Shale occurs mainly in the immediate area of Montreal, as well as from the city of Sainte-Anne-de-la-Pérade to the Sainte-Anne du Nord River and the Baie-Saint-Paul area, NE of Quebec City. It also outcrops NE of Terrebonne, at Île des Soeurs, around the municipality of Candiac, and north of Lake Champlain along a NE strip extending to the Yamaska Mountain.”

According to Thériault (2012b): “The Utica Shale typically ranges in thickness from 100 to 250 m, reaching up to 750 m in the southern part of the area. From drilling wells, the average thickness of the Utica Shale is estimated to be 105 m west of the Yamaska Fault, increasing to 220 m east of the fault. The average thickness of the Utica in the southern portion of the St. Lawrence Lowlands (Richelieu and Lake Champlain area) is around 640 m.”

The depth of the Utica Shale increases abruptly along the Yamaska Fault from ~800 m deep to ~1200 m east of it (Thériault, 2012b). The base of the Utica Shale, which corresponds to the roof of the Trenton Group (transitional contact), displays similar deepening to the SE, from ~900 m deep west of the Yamaska Fault to ~1400 m to the east, to finally reach a depth of nearly 3000 m along the Logan Line (Thériault, 2012b).

Logan et al. (1863) mapped the Utica Shale over a thickness of 98 m at the reference outcrop between the fall of the Sainte-Anne River and the mouth of the Jean-Larose River. At the Sainte-Anne-du-Nord River, the shale is visible over a thickness of 80 m, while at Montmorency Falls the thickness is estimated at 60 m but reduced to 30 m by faulting (Belt et al., 1979). Near Lake Champlain, the Utica Shale is >120 m thick (Globensky, 1987). InTrois-Rivières, the unit thickness was observed and calculated between 22 and 30 m (Clark and Globensky, 1976).

Dating

None.