Mudstone
Mudstone, a type of mudrock, is a fine-grained sedimentary rock whose original constituents were clays or muds. Mudstone is distinguished from shale by its lack of fissility (parallel layering).[1][2]
The term mudstone is also used to describe carbonate rocks (limestone or dolomite) that are composed predominantly of carbonate mud.[3] However, in most contexts, the term refers to siliciclastic mudstone, composed mostly of silicate minerals.[2]
The
Definition
There is not a single definition of mudstone that has gained general acceptance,
The lack of fissility or layering in mudstone may be due to either original texture or the disruption of layering by burrowing organisms in the sediment prior to lithification. Mudstone looks like hardened clay and, depending upon the circumstances under which it was formed, it may show cracks or fissures, like a sun-baked clay deposit.[1]
When the mineral composition of mudstones has been determined, using such techniques as
Carbonate mudstone
In the Dunham classification (Dunham, 1962[11]) system of limestones, a mudstone is defined as a mud-supported carbonate rock that contains less than 10% grains. Most recently, this definition has been clarified as a matrix-supported carbonate-dominated rock composed of more than 90% carbonate mud (<63 μm) component.[3]
The identification of carbonate mudstone
A recent study by Lokier and Al Junaibi (2016)[3] has highlighted that the most common problems encountered when describing a mudstone is to incorrectly estimate the volume of 'grains' in the sample - in consequence, misidentifying mudstone as wackestone and vice versa. The original Dunham classification (1962)[11] defined the matrix as clay and fine-silt size sediment <20 μm in diameter. This definition was redefined by Embry & Klovan (1971[12]) to a grain size of less than or equal to 30 μm. Wright (1992[13]) proposed a further increase to the upper limit for the matrix size in order to bring it into line with the upper limit for silt (63 μm).
Mudstone mineralogy on Mars
On December 13, 2016, NASA reported further evidence supporting habitability on the planet Mars as the Curiosity rover climbed higher, studying younger layers, on Mount Sharp.[15] Also reported, the very soluble element boron was detected for the first time on Mars.[15] In June 2018, NASA reported that Curiosity had detected kerogen and other complex organic compounds from mudstone rocks approximately 3.5 billion years old.[4][16][17][18][19][20][21][22]
See also
References
- ^ ISBN 0-7167-2438-3
- ^ ISBN 0131547283.
- ^ ISSN 1365-3091.
- ^ a b Brown, Dwayne; Wendel, JoAnna; Steigerwald, Bill; Jones, Nancy; Good, Andrew (June 7, 2018). "Release 18-050 - NASA Finds Ancient Organic Material, Mysterious Methane on Mars". NASA. Retrieved June 11, 2018.
- ^ a b c Boggs 2006, p.143
- ISBN 978-3-319-61185-3.
- ^ ISBN 0-914696-14-9. Archived from the originalon 2006-02-14. Retrieved 2 October 2020.
- ^ ISBN 0387904301.
- .
- ^ Boggs 2006, pp.140-143
- ^ a b Dunham, R.J., 1962. Classification of carbonate rocks according to depositional texture. In: W.E. Ham (Ed.), Classification of Carbonate Rocks. American Association of Petroleum Geologists Memoir. American Association of Petroleum Geologists, Tulsa, Oklahoma, pp. 108-121.
- ISSN 0007-4802.
- .
- ^ Staff (December 13, 2016). "PIA21146: Mudstone Mineralogy from Curiosity's CheMin, 2013 to 2016". NASA. Retrieved December 16, 2016.
- ^ a b Cantillo, Laurie; Brown, Dwayne; Webster, Guy; Agle, DC; Tabor, Abigail; Mullane, Laura (December 13, 2016). "Mars Rock-Ingredient Stew Seen as Plus for Habitability". NASA. Retrieved December 14, 2016.
- ^ NASA (June 7, 2018). "Ancient Organics Discovered on Mars - video (03:17)". NASA. Archived from the original on 2021-12-13. Retrieved June 11, 2018.
- ^ Wall, Mike (June 7, 2018). "Curiosity Rover Finds Ancient 'Building Blocks for Life' on Mars". Space.com. Retrieved June 11, 2018.
- ^ Chang, Kenneth (June 7, 2018). "Life on Mars? Rover's Latest Discovery Puts It 'On the Table' - The identification of organic molecules in rocks on the red planet does not necessarily point to life there, past or present, but does indicate that some of the building blocks were present". The New York Times. Retrieved June 11, 2018.
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