when did the current geologic epoch begin and what event marked its beginning
Holocene The Holocene ( /ˈhɒləˌsiːn, ˈhoʊ-/)[2][3] is the current geological epoch. It began approximately 11,650 years before present, after the last glacial period.[4] The Holocene and the preceding Pleistocene[5] together form the Quaternary period. The Holocene has been identified with the current warm period, known as MIS 1, and is considered by some to be an interglacial period.
Oldest dated rocks The oldest dated rocks on Earth, as an aggregate of minerals that have not been subsequently broken down by erosion or melted, are more than 4 billion years old, formed during the Hadean Eon of Earth's geological history. Such rocks are exposed on the Earth's surface in very few places. Some of the oldest surface rock can be found in the Canadian Shield, Australia, Africa and in a few other old regions around the world. The ages of these felsic rocks are generally between 2.5 and 3.8 billion years. The approximate ages have a margin of error of millions of years. In 1999, the oldest known rock on Earth was dated to 4.031 Â±0.003 billion years, and is part of the Acasta Gneiss of the Slave craton in northwestern Canada.[1] Researchers at McGill University found a rock with a very old model age for extraction from the mantle (3.8 to 4.28 billion years ago) in the Nuvvuagittuq greenstone belt on the coast of Hudson Bay, in northern Quebec;[2] the true age of these samples is still under debate, and they may actually be closer to 3.8 billion years old.[3] Older than these rocks are crystals of the mineral zircon, which can survive the disaggregation of their parent rock and be found and dated in younger rock formations.