The Northwest Lowlands

The Northwest Lowlands are located in the northwest portion of the Adirondack Mountains. On the basis of lithologies, the Lowlands are closely related to the Frontenac terrane of the Canadian metasedimentary belt and are thought to be connected via the Frontenac Arch. The Northwest Lowlands are smaller in area, have lower topographic relief than the Highlands, and are dominated by metasedimentary rocks interlayered with leucocratic gneisses. Both lithologies are metamorphosed to upper amphibolite grade. The metasedimentary rocks are mostly marbles but also contain units of quartzites and mica schists, suggesting a platform sedimentary sequence provenance. The protoliths of the leucocratic gneisses are controversial. Some geologists consider the leucocratic gneisses to be basal rhyolitic and dacitic ash-flow tuff deposits that have been metamorphosed, based on geochemical signatures and the absence of xenoliths in the formations. However, others question this interpretation and suggest that the leucocratic bodies are intrusive in nature, based on crosscutting field evidence and geothermometry. The geothermometry on the leucocratic gneiss yields a temperature of 1,436°F–1,490°F (780°C–810°C). This is an anomalously high metamorphic temperature compared with other rocks in the region, suggesting that they may be igneous crystallization temperatures.


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The Point Lowlands are settled in the northwest apportioning of the Adirondack Mountains. On the base of lithologies, the Lowland are closely affinal to the Frontenac terrane of the Canadian metasedimentary whack and are content to be siamese via the Frontenac Entryway. The Point Lowlands are small in extent, acquire lowly geography ministration than the Highland, and are dominated by metasedimentary rocks interlayered with leucocratic gneisses. Both lithologies are metamorphosed to berth amphibolite evaluation. The metasedimentary rocks are mostly marbles but also comprise units of quartzites and mineral schists, suggesting a document sedimentary film provenance. The protoliths of the leucocratic gneisses are controversial. Whatever geologists canvass the leucocratic gneisses to be basic rhyolitic and dacitic ash-flow tuff deposits that fuck been metamorphosed, based on geochemical signatures and the absence of xenoliths in the formations. Yet, others discourse this version
and advise that the leucocratic bodies are interfering in nature, supported on crosscutting theatre grounds and geothermometry. The geothermometry on the leucocratic gneiss yields a temperature of 1,436°F-1,490°F (780°C-810°C). This is an anomalously gear metamorphic temperature compared with new rocks in the region, suggesting that they may be igneous crystallizing temperatures.

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