Flute casts and related structures on moulded silt injection surfaces in continental sandstone of the Boss Point Formation: southeastern New Brunswick, Canada

Flute, load and groove casts occur widely at the sharp Interfaces of siltstone diapirs, Injection lenses, and pods la fluvial sandstone of the Boas Point Formation of southeastern New Brunswick. These concordant and discordant Injection features range from approximately 20 centimetres (pods) to many metres (injection lenses) In diameter. They are confined to "brecclform Intervals" that can be traced along strike and dip for a hundred metres or more. The flute, load and groove casts on the Injection surfaces, have evidently not been formed by any primary sedimentary process but are the result of liquefaction, sediment Injection and flow moulding during post-depositonal compaction of the strata. The term "rheoplasis" Is proposed to denote this process, and the general term "rhaoplastic structures" or "rheoplasts" refers to the range of sole-marking like structures formed as a result of this process. The realization that flute costs can form as a result of post-depostional processes is of great significance In the classification of sedimentary structures and the Interpretation of depositional environments and attendant sedimentary processes. RESUME Au sud-est du Nouveau-Brunawlck, dans les gres fluvlatiles de la formation de Boss Point, on peut voir de nombreax exemples de flutes, empreintes de charge et cannelures aux interfaces distlncts de diapirs de siltstone, de lentilles d'injection, de mottes et de loupes. Ces elements d'injection sont concordance ou discordants et possedent un dlametre allant de 20 cm (pour les loupes) jusqu'a plualeurs metres (pour les lentilles d'injection). Ils sont egalemenr restraints a des "intervalles brechiques" que l'on peut suivre sur des cencaines de metres et plus, le long de la direction et du pendage de la stratification. Les flutes, cannelures et empreintes de charge que l'on retrouve aur les surfaces d'injection ne resultent evideoment pas d'un processus sedimentalre primaire male plutot de la liquefaction, de l’injection du sediment et du moulage des coulees durant la compaction apres la deposition de la strate. Pour marquer ce procede, on propose le terme "rheoplasle" alors que le terme plus global "structures rheoplastiquea" (ou "rheoplaates") a'appllque lux empreintes de toutes sortes qui resultent de ce meme procede et que l'on retrouve sur la surface inferieutre d'une strate. La classification des structures sedimentaires ainsi que l'interpretation des envlronnements de deposition et des procedee sediment aires connexes aeront grandetnent influenced par le fait que des flutes peuvent resulter d'un procede post-deposltionnel. [Tradult par le Journal]