Flute casts and related structures on moulded silt injection surfaces in continental sandstone of the Boss Point Formation: southeastern New Brunswick, Canada
DOI:
https://doi.org/10.4138/1372Abstract
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. RÉSUMÉ Au sud-est du Nouveau-Brunawlck, dans les grès fluvlatiles de la formation de Boss Point, on peut voir de nombreax exemples de flûtes, empreintes de charge et cannelures aux interfaces distlncts de diapirs de siltstone, de lentilles d'injection, de mottes et de loupes. Ces éléments d'injection sont concordance ou discordants et possèdent un dlamètre allant de 20 cm (pour les loupes) jusqu'à plualeurs mètres (pour les lentilles d'injection). Ils sont égalemenr restraints à des "intervalles bréchiques" que l'on peut suivre sur des cencaines de mètres et plus, le long de la direction et du pendage de la stratification. Les flûtes, cannelures et empreintes de charge que l'on retrouve aur les surfaces d'injection ne résultent évideoment pas d'un processus sédimentalre primaire male plutôt de la liquéfaction, de l’injection du sédiment et du moulage des coulées durant la compaction après la déposition de la strate. Pour marquer ce procede, on propose le terme "rhéoplasle" alors que le terme plus global "structures rhéoplastiquea" (ou "rhéoplaates") a'appllque lux empreintes de toutes sortes qui résultent de ce même procédé et que l'on retrouve sur la surface inférieutre d'une strate. La classification des structures sédimentaires ainsi que l'interprètation des envlronnements de déposition et des procédée sédiment aires connexes aeront grandetnent influenced par le fait que des flûtes peuvent résulter d'un procédé post-déposltionnel. [Tradult par le Journal]Downloads
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