Cambrian shelf deposits of the King Square Formation, Saint John Group, southern New Brunswick

Authors

  • Saifullah K. Tanoli Department of Geology, University of New Brunswick, Fredericton, New Brunswick E3B 5A3, Canada; Present address: Department of Geology, University of Peshawar, Peshawar, Pakistan
  • Ron K. Pickerill Department of Geology, University of New Brunswick, Fredericton, New Brunswick E3B 5A3, Canada

DOI:

https://doi.org/10.4138/1678

Abstract

The upper Middle Cambrian to early Late Cambrian King Square Formation, Saint John Group, southern New Brunswick, is an approximately 380 m thick silicilastic sequence of interbedded fine-grained sandstones and siltstones and shales. On the basis of sandstone to shale/siltstone ratios, bed thickness and characteristics, sedimentary structures and degree of bioturbation three lithofacies are recognized. These are facies KS1, thin bedded sandstone and shale lithofacies; KS2, thick bedded sandstone lithofacies; and KS3, bioturbatcd shale and siltstone with interbedded sandstone lithofacies. These lithofacies are interpreted to havebeen deposited on a wave- and storm-influenced marine subtidal shelf. Facies KS 1 was deposited essentially below wave base though in its upper horizons, deposition may have occurred above storm wave base. Facies KS2 was essentially deposited in a shallower subtidal inner- to mid-shelf environment above storm wave base and facies KS3 initially above and latterly below storm wave base. The exact nature of the currents responsible for transportation and deposition of the storm-related sandstones (geostrophic flows or turbidity currents) is impossible to determine and therefore palaeocurrent data must be interpreted with caution. The stratigraphic arrangement of the lithofacies, with facies KS1 being the oldest and KS3 the youngest, suggests that the King Square Formation represents a regressive-transgressive sequence. RÉSUMÉ La Formation de King Square (Groupe de Saint John, Nouveau-Brunswick, fin du Cambrien moyen—début du Cambrien tardif) est une série terrigène d'environ 380 m d'épaisseur, constitutée d'un interlitage de grès fins, de siltstones et de shales. Les rapports grès/shale et grès/siltstone, les caractéristiques et l’épaisseur des lits, les structures sédimentaires ainsi que le degré de bioturbation permettent de reconnaitre trois lithofaciès. Ce sont les faciès KS1 (grès et shale finement lité), KS2 (grès en bancs épais) et KS3 (grès interim de shale et siltstone bioturbes). On interprète ces lithofacies comme ayant été déposés sur une plate-formé marine subtidale influencée par la houle et les tempetes. Le dépôt du faciès KS 1 s'effectua essentiellement sous la zone d'amortissement de la houle quoique ses horizons supérieurs puissent refléter une sédimentation au-dessus de la profondeur d' amortisscment des ondes liées aux tempetes. Le milieu de dépôt du faciès KS2 correspond à un site moins profond, soit la plate-formé infralittorale interne ou moyenne, exposée à faction des ondes de tempêtes. Le dépôt du faciès KS3 débuta au-dessus de la profondeur d'amortissement des ondes liées aux tempêtes et continue en-dessous de celle-ci. On ne peut guère déterminer la nature exacte des courants géostrophiques ou de turbidité responsables du transport et du dépôt des grès lies aux tempetes; la prudence est done de mise lors de l'interprètation des données sur les paieocouranls. Le faciès KS 1 étant le plus ancien et le faciès KS3 lc plus recent, l'agcncemenl des lithofaciès suggère que la Formation de King Squarere présente une série d'abord régressive puis transgressive. [Traduit par le journal]

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Published

1989-08-01

How to Cite

Tanoli, S. K., & Pickerill, R. K. (1989). Cambrian shelf deposits of the King Square Formation, Saint John Group, southern New Brunswick. Atlantic Geoscience, 25(2). https://doi.org/10.4138/1678

Issue

Vol. 25 No. 2 (1989)

Section

Articles

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