In contrast, the layered successions of rocks give only relative ages – older than, or younger than. Category: Rocks, Fossils, Minerals and Meteorites Decade: 1980s References Stern, R. Age of the World’s Oldest Rocks Refined Using Canada’s SHRIMP: The Acasta Gneiss Complex, Northwest Territories, Canada; Geoscience Canada, v. The Fordham Gneiss dominantly consists of metamorphosed igneous rocks, which range from felsic, through mesocratic, to mafic in composition.Our geochemical studies show that most of these rocks have compositions indicative of a volcanic-arc origin.In recent years we have proposed new interpretations of the metamorphic, stratigraphic, and tectonic histories of the Manhattan Prong (see, for instance, our abstracts for the Long Island Geologists conferences in 1998, 1999, and 2001).Here, we provide a brief outline of the geologic history of the region, which is also summarized on Table 1, Simplified Geologic History of the New York City Area.
This analytical laboratory process measures the ratios between parent and daughter atoms in mineral grains such as zircon that contain traces of radioactive uranium. 3920 Ma Acasta Gneiss; Geochimica et Cosmochimica Acta, v.
, as well as the islands of Coll and Tiree, and are exposed along the northwestern coast of Scotland.
The oldest rocks of the Lewisian have been dated by radiometric techniques at between 2.4 billion and 2.6 billion years old, whereas the youngest Lewisian rocks have been dated at 1.6 billion years.
The Canadian Shield, the largest expanse of Precambrian rocks on Earth, is host to Earth’s oldest known rock – the Acasta Gneiss of the Slave Province of the Shield, located about 300 kilometres north of Yellowknife, Northwest Territories.
Gneiss is a type of rock that has been metamorphosed (affected by intense heat and pressure) at depth in Earth’s crust.