麻豆传媒

The Wolfville Formation, which is overlain by the Blomidon Formation, has limited exposed area relative to its wide subsurface extension beneath the Bay of Fundy, where it is underlain by the Horton Bluff Formation in the Minas Basin area, and by Meguma and/or Avalon Zones in the southwestern parts of the Bay of Fundy. The sandstones of the Triassic Wolfville Formation at Cambridge Cove exposed at the southern coast of the Bay of Fundy were investigated petrographically. The study included grain size analysis, diagenesis, porosity, and heavy mineral analysis and reservoir characteristics depending on these properties. These fluvial sandstones are calcite cement- supported feldspathic litharenites to lithic felsarenites. They consist of cement (dominated by calcite and minor iron oxide and clays) (36.4%), quartz (31.5%), lithics (13.0%), feldspars (9.9%), heavy minerals (0.9%), mica & chlorite (0.5%) and the rest is pore spaces. The average ratio of plagioclase/alkali feldspars is 10.8%. The sandstones have a recycled orogenic provenance derived from metasedimentary and granitic rocks postdating the collision type setting and during the early stages of rifting. Their heavy minerals consist of iron oxides (75.9%), garnet (13.6%), apatite (3.3%), chlorite (3.3%), zircon (1.4%), tourmaline (1.3%), biotite (1%) and few others. The main sources of these sediments are the Paleozoic rocks which are now underlying the Wolfville Formation. The probably source of arenaceous rocks (siltstone, sandstone, chert and quartz) and metaseidments (slates, schists, and quartzites) are Meguma Supergroup, Horton Group, Windsor Group, Torbrook, Canso and Kentville formations, that of granitoids, quartz and feldspars is dominantly South Mountain Batholith (SMB), while those of limestone are Windsor Group and Canso (Mabou) Formation. The provenance of opaques (Fe and Fe-Ti oxides) are possibly the SMB and iron formations of Torbrook Formation, while the main source of the garnets are the Meguma Group and SMB, and those of the zircon-tourmaline-rutile (ZTR), apatite and micas are mostly the SMB with minor contributions from the other formations. The Meguma, Horton and Windsor Groups and SMB, which were and still are dominant rock units in the area, are the main source of the Wolfville Formation sediments. Minor contribution from the Appalachian Mountain exposures to the north of the Bay of Fundy in New Brunswick can not be excluded but the absence of volcanics in the studied sediments minimizes that possibility. The Wolfville sandstones have a porosity ranging from 2.6 to 16.6% (6% on average) which gives it the potential to be a moderate to good reservoir rocks for hydrocarbons, especially where it overlies the potential source rocks such as the organic-rich shales of Horton Bluff Formation, or other younger shales within the Mesozoic rocks in the subsurface section beneath the Bay of Fundy.

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Pages: 71
Supervisor: Grant Wach