Résumés
Abstract
The Cradle Brook fault zone in southern New Brunswick separates highly deformed Precambrlan terranes reflecting radically different geological environments. The zone is comprised of major southward directed thrusts and is interpreted to represent, in part, the boundary between the Central and Eastern volcanic belts of the Caledonia Highlands.
The Precambrlan rocks north of the fault reflect subaerlal and. locally, subaqueous deposition whereas those south of the fault reflect marine deposition. In addition to the differences in Precambrlan stratigraphy, extensive areas south of the fault are underlain by felsic and mafic Intrusive bodies of probable late Precambrian age, and by Cambrian rocks that rest unconformably on the stratigraphy of the Eastern Volcanic Belt. Based on a limited number of chemical analyses, the volcanic piles exhibit cale alkaline and weakly tholelitic affinities south and north of the fault, respectively.
The structural and stratigraphic relationships imply that the subaerlal rocks are older than the marine rocks and that the latter are probably near the top of the local Precambrian sequence. The abundance of intrusive rocks in the subaqueous sequence substantiate juxtaposition of very different geological regimes.
RESUME
Au Nouveau-Brunswick meridional, la zone de failles de Cradle Brook separe des lanieres precambriennes f ortement def ormees qui temoignent d' envir onnements geologiques radlcalement differents. Cette zone s'organise en chevauchements majeurs de direction sud-est. On croit qu'elle represente, en partle, la frontiere entre les ceintures volcaniques centrale et orlentale des Honts Caledonia.
Au nord de la faille, les roches precambriennes relevent essentiellement d'une accumulation subaerienne et, localement, subaquatlque, alors qu'au sud de la faille, elles trablssent un depot marln. On doit ajouter aux differences dans la stratigraphie precambrienne de vastes etendues au sud de la faille qui comprennent des appareils intrusifs felsiques et mafiques. probablement tardi-precamhriens, et des assises cambriennes qui recouvrent en discordance la stratigraphie de la ceinture volcanique orientale. La prise en compte d'un nombre limite d'analyses chimiqut>s revele les affinites calco-alcalines et falblement tholeiitlques des empllcmunLu volcaniques sis, respectivement, au sud et au nord de la faille.
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