The La Coulée Formation, a new post-Acadian continental clastic unit bearing groundwater calcretes, Gaspé Peninsula, Quebec

Abstract

A 1 km2 erosional remnant of the La Coulee Formation, a previously unrecognized stratigraphic unit, has been studied in the Percd area of the Gaspe Peninsula. It unconformably overlies folded Cambrian to Devonian rocks and is unconformably overlain by the mid-Carboniferous Bonaventure Formation. The erosional remnant includes the lowest 60 m of this newly identified formation of unknown thickness. Original sedimentary facies are limited to 50 m of breccia debris flows passing stratigraphically upward into 10 m of conglomeratic debris flows. Groundwater calcrete formation has partially or completely transformed the lowest 30 m of the sequence. The depositional environment is interpreted as being related to a proximal continental alluvial fan. The nearby presence of a saline body of water is inferred to account for thick and massive groundwater calcrete formation and water-saturated debris flows in a relatively arid climatic context. Most of the formation was eroded prior to deposition of the Bonaventure Formation. However, the basal groundwater calcretes were more widely preserved. They underlie the Bonaventure Formation in most of the Percd area and in the Saint-Elzear area, close to a hundred kilometres to the southwest. Post-sedimentary faulting has affected both the La Coulde and Bonaventure formations.La Formation de La Coulee, une unite stratigraphique nouvellement repertoride, a etd etudiee a l'interieur d'une masse residuelle de lkm2 dans la region de Percd en Gaspdsie. La sequence recouvre en discordance des roches plissees du Ddvonien Inferieur et elle est recouverte en discordance par la Formation de Bonaventure qui est attribude au Carbonifdre moyen. La masse residuelle inclue les 60 premiers mdtres de cette formation nouvellement identifide et d'une dpaisseur inconnue. Les facids sedimentaires originels sont limitds k cinquante metres de coulees de ddbris brdchiques, passant a une dizaine de mdtres de couldes de ddbris conglomdratiques. La formation d'une calcrete phrdatique affecte les premiers 30 mdtres de la sdquence, lesquels sont en partie ou compldtement transformds. L'environnement sddimentaire est interprdtd comme dtant lid k un c6ne de ddjection continental dans sa partie proximale, mais la prdsence non-lointaine d'un plan d'eau salde est suggdrde pour expliquer la formation de calcretes phrdatiques epaisses et massives, ainsi que la saturation en eau des couldes de ddbris dans un contexte climatique relativement aride. La formation a presqu'entidrement dtd drodde avant que ne survienne la sddimentation de la Formation de Bonaventure. Toutefois, la base de calcrete a dtd plus largement prdservde, ce qui fait qu'on la retrouve sous la Formation de Bonaventure presque partout dans la rdgion de Percd ainsi que dans la rdgion de Saint-Elzdar, k presqu'une centaine de kilomdtres au sud-ouest. Des failles post-sedimentaires ont affectd a la fois la Formation de La Coulde et la Formation de Bonaventure.

Complex interplay of faulting, glacioeustatic variations and halokinesis during deposition of upper Viséan units over thick salt in the western Cumberland Basin of Atlantic Canada

“…() proposed to formally correlate the Hopewell Cape Formation with the Bonaventure Formation of Logan (), which has precedence, but this stratigraphic simplification has not been adopted by other workers in the Cumberland Basin (e.g., St. Peter & Johnson, ). Because Logan mapped as Bonaventure Formation many units that were subsequently removed from it (e.g., the Middle Devonian Malbaie Formation of McGerrigle, ; the Upper Devonian to lower Mississippian St‐Jules Formation of Jutras & Prichonnet, ; the middle Viséan La Coulée Formation of Jutras et al ., ; the Serpukhovian Pointe Sawyer and Chemin‐des‐Pêcheurs formations of Jutras et al ., ), and because his reference section at Bonaventure Island (eastern Quebec) is incomplete and was never formally measured, we herein propose to abandon this unit and correlate it with the better constrained Hopewell Cape Formation of St. Peter & Johnson ().…”

Sedimentology of the lower Serpukhovian (upper Mississippian) Mabou Group in the Cumberland Basin of eastern Canada: tectonic, halokinetic, and climatic implications

“…Since our paleocurrent data differ so much from those of previous authors (Hamblin 2001;Allen et al 2013), and since data from the latter authors also differ substantially from each other, an assessment of data reliability is here called for. In our experience of collecting broadly distributed paleocurrent measurements from braided fluvial systems (Jutras et al 1999(Jutras et al , 2001(Jutras et al , 2007(Jutras et al , 2015Jutras and Prichonnet, 2002, we now consider data collected from channel-fills (clast imbrications, ripple marks, planar-cross bedding and parting lineations) as highly unreliable, because deposition of the latter can be from weak secondary currents that were strongly influenced by the geometry of the channels, whereas scours are the products of stronger currents that reflect better the direction of the source area. Two-thirds of the paleocurrent measurements in Hamblin (2001) are from ripple mark orientations, which we consider as unreliable.…”

Carbonate melting and peperite formation at the intrusive contact between large mafic dykes and clastic sediments of the upper Palaeozoic Saint‐Jules Formation, New‐Carlisle, Quebec

“…* The carbon isotope ratios of the carbonate matrix are not diluted enough compared to those of non-dissociated carbonate (Figure 6c and samples C7a-c on Figure 10) to support the hypothesis of mineral replacement by infiltrating hydrothermal waters that show significantly lighter isotopic ratios (samples C1-2 on Figure 10). For instance, sub-surface mineral replacement by meteoric groundwaters leaves carbon isotope ratios in the resulting calcrete that contrast sharply with those of their host rock remnants (Jutras et al 1999).…”