Shale

Sedimentary rock
Shale
Composition
Clay minerals and quartz

Shale is a fine-grained, clastic sedimentary rock composed of mud that is a mix of flakes of clay minerals and tiny fragments (silt-sized particles) of other minerals, especially quartz and calcite. The ratio of clay to other minerals is variable.^[1] Shale is characterized by breaks along thin laminae or parallel layering or bedding less than one centimeter in thickness, called fissility.^[1] Mudstones, on the other hand, are similar in composition but do not show the fissility.

Texture[link]

Shale typically exhibits varying degrees of fissility breaking into thin layers, often splintery and usually parallel to the otherwise indistinguishable bedding plane because of parallel orientation of clay mineral flakes.^[1] Non-fissile rocks of similar composition but made of particles smaller than 0.06 mm are described as mudstones (1/3 to 2/3 silt particles) or claystone (less than 1/3 silt). Rocks with similar particle sizes but with less clay (greater than 2/3 silt) and therefore grittier are siltstones.^[1] Shale is the most common sedimentary rock.^[2]

Sample of drill cuttings of shale while drilling an oil well in Louisiana. The sand grain is 2 mm in diameter.

Composition and color[link]

Shales are typically composed of variable amounts of clay minerals and quartz grains and the typical color is gray. Addition of variable amounts of minor constituents alters the color of the rock. Black shale results from the presence of greater than one percent carbonaceous material and indicates a reducing environment.^[1] Black shale can also be referred to as black metal.^[3] Red, brown and green colors are indicative of ferric oxide (hematite – reds), iron hydroxide (goethite – browns and limonite – yellow), or micaceous minerals (chlorite, biotite and illite – greens).^[1]

Clays are the major constituent of shales and other mudrocks. The clay minerals represented are largely kaolinite, montmorillonite and illite. Clay minerals of Late Tertiary mudstones are expandable smectites whereas in older rocks especially in mid to early Paleozoic shales illites predominate. The transformation of smectite to illite produces silica, sodium, calcium, magnesium, iron and water. These released elements form authigenic quartz, chert, calcite, dolomite, ankerite, hematite and albite, all trace to minor (except quartz) minerals found in shales and other mudrocks.^[1]

Shales and mudrocks contain roughly 95 percent of the organic matter in all sedimentary rocks. However, this amounts to less than one percent by mass in an average shale. Black shales which form in anoxic conditions contain reduced free carbon along with ferrous iron (Fe²⁺) and sulfide (S^2-). Pyrite and amorphous iron sulfide along with carbon produce the black and purple coloration.^[1]

Formation[link]

Limey shale overlaid by limestone, Cumberland Plateau, Tennessee

The process in the rock cycle which forms shale is compaction. The fine particles that compose shale can remain suspended in water long after the larger and denser particles of sand have deposited. Shales are typically deposited in very slow moving water and are often found in lakes and lagoonal deposits, in river deltas, on floodplains and offshore from beach sands. They can also be deposited on the continental shelf, in relatively deep, quiet water. This process could have taken millions of years to complete.

'Black shales' are dark, as a result of being especially rich in unoxidized carbon. Common in some Paleozoic and Mesozoic strata, black shales were deposited in anoxic, reducing environments, such as in stagnant water columns. Some black shales contain abundant heavy metals such as molybdenum, uranium, vanadium, and zinc.^[4][5][6] The enriched values are of controversial origin, having been alternatively attributed to input from hydrothermal fluids during or after sedimentation or to slow accumulation from sea water over long periods of sedimentation.^[5][7][8]

Splitting shale with a large knife to reveal fossils

Fossils, animal tracks/burrows and even raindrop impact craters are sometimes preserved on shale bedding surfaces. Shales may also contain concretions consisting of pyrite, apatite, or various carbonate minerals.

Shales that are subject to heat and pressure of metamorphism alter into a hard, fissile, metamorphic rock known as slate. With continued increase in metamorphic grade the sequence is phyllite, then schist and finally to gneiss.

See also[link]

References[link]

for the rugby union footballer, see Michael Stephenson (rugby union)

Michael "Mike" Stephenson, also commonly known as Stevo, (born 27 January 1947 in Dewsbury, West Yorkshire) is an English Rugby League World Cup winning Rugby League, and presenter/commentator on British satellite television channel Sky Sports who also represented Great Britain in the sport.^[1]

Stevo, the nickname that he is commonly known as on TV and in rugby league circles, played at club level for English club Dewsbury and Australian side Penrith, and also played representative rugby league for the Yorkshire county team. Stephenson played in the specialist Hooker role for the vast majority of his playing career.

Mike Stephenson was responsible for the setting-up of the Rugby League Heritage Centre at the George Hotel, Huddersfield.

Playing career[link]

Stephenson began his professional playing career at his hometown club Dewsbury in 1966, after being signed from local amateur club Shaw Cross. He went on to make his Great Britain debut in Castleford in 1971, against the touring New Zealand side. His greatest moment in international rugby league, however, was being a member of Great Britain's victorious 1972 World Cup-winning side that won the trophy in France; Stevo scored a try against Australia in the final.

Stephenson won caps for Great Britain while at Dewsbury in 1971 against New Zealand, in 1972 against France, and in the 1972 World Cup against Australia, France, New Zealand, and Australia.^[2]

Stephenson's time in the Dewsbury first team coincided with an upturn in the club's fortunes on the pitch, culminating with the team winning the British Rugby Football League Championship in the 1972–73 season. He left Dewsbury after their championship winning season in 1973 to join Australian Rugby League outfit Penrith. He played 169 games for the Panthers 1974-78, scoring 21 tries. Stevo was also player-coach of the side for a brief, unsuccessful spell. He ended his playing career in 1978 and settled in Sydney.

Broadcasting career[link]

Stevo began his broadcasting career in Australia with brief spells at radio and television stations in Sydney. He first appeared on British airwaves in 1988, when he was invited to co-commentate on the rugby league Ashes series in Australia for BBC Radio 2 with Eddie Hemmings.

"Stevo" presenting for Sky Sports during the 2008 Rugby League World Cup

In 1990, Stevo joined the new UK satellite television broadcaster BSB as a match summariser for its Rugby League coverage. At BSB, he joined up again with Hemmings, who had also been signed up by the broadcaster. The pairing were kept together when BSB and Sky Television merged to form BSkyB in 1991; the combined satellite TV network inherited BSB's rugby league TV contract.

Stevo was a massive supporter of the creation of Super League, the elite northern hemisphere club rugby competition which started in the British spring of 1996.

Eddie & Stevo are still the main presenters and commentators on Sky Sports' Super League coverage.

References[link]

Stevo: Looking Back, by Mike Stephenson ISBN 978-1-904091-23-3

External links[link]

• International Statistics at englandrl.co.uk
• Statistics at rugbyleagueproject.org
• Penrith Points
• Playing at Smales pace sank champions - article at yorkshirepost.co.uk
• When Great Britain won the World Cup
• Tracking down the heroes of 1972

Timothy Don Carr (May 30, 1970 – January 25, 2005), a 34-year-old white male, was executed by lethal injection at the Georgia Diagnostic and Classification Prison in Jackson, Georgia on January 25, 2005. Carr was found guilty of the 1992 murder of Keith Patrick Young, a 17-year-old white male. Carr, who was 22-years old when he committed the capital crime, was sentenced to death on April 28, 1994.

On October 7, 1992, Carr was at a party in Macon, Georgia with his girlfriend, Melissa Leslie Burgeson, a 22-year-old white female, and Keith Young. The people at the party consumed alcohol and the juice from boiled hallucinogenic mushrooms and some also smoked marijuana. Later autopsy reports showed that Keith Young had no drugs other than alcoholic beverages in his system at the time of his death. Carr and Burgeson discussed robbing Young at the party.

In the early hours of the following day Burgeson took Young's car keys and talked him into letting her drive him home. Burgeson obtained Young's car keys claiming that he was too intoxicated to drive. She and Carr discussed robbing Young of his gold 1986 Pontiac Grand Prix. They also knew that Young had just cashed his paycheck.

That morning Burgeson, Carr, Young, and a 16-year-old boy and girl left the party in Young's Grand Prix. Burgeson was driving, Young was in the front passenger seat, and the others were in the back seat. During the drive Carr displayed a knife to one of the juveniles and whispered to her that he was going to kill Young. There was also a baseball bat in the back seat of the car.

Burgeson later stopped the car on a dirt road some 15 miles northwest of Macon under the pretense that they were going to look for mushrooms and everyone exited except for the female juvenile. When Young was looking in the trunk Burgeson whispered to Carr to "do it now" whereupon Carr grabbed Young from behind and cut his throat twice. Burgeson said, "that ain't enough," and Carr stabbed Young several times in the chest. Young pleaded for his life but Carr laughed and said, "I'm going to kill you, boy."

After Young had fallen to the ground Carr rolled him over on his stomach and stabbed him several times in the lower back. The male juvenile then handed Carr the baseball bat and Carr beat Young in the head, fracturing his skull. Burgeson took $125 from Young's pockets and they returned to Macon where they dropped off the male juvenile and then drove to Tennessee where Carr, Burgeson, and the female juvenile were arrested after they crashed following a high-speed chase.

After receiving medical treatment at a local hospital Carr and Burgeson were placed in the back of a police car in which police had activated a hidden tape recorder. Their recorded conversation, in which Carr admitted killing Young, was introduced into evidence at Carr's trial. The knife used to stab Young was also discovered in Burgeson's purse and presented as evidence.

Following a jury trial in Monroe County, Carr was sentenced to death for the Young murder and to 20 years’ imprisonment for the theft of Young’s car. The day before his execution the state Board of Pardons and Paroles denied clemency. Accomplice Burgeson was convicted of malice murder and sentenced to life in prison.

See also[link]

• List of individuals executed in Georgia
• Capital punishment in the United States

References[link]

• Timothy Don Carr. The Clark County Prosecuting Attorney. Retrieved on 2008-04-15.
• Michelangelo Delfino and Mary E. Day, Death Penalty USA 2005 - 2006, (2008), 31-32.
• Carr v. State (1997) 480 S.E.2d 583.
• Head v. Carr (2001) 544 S.E.2d 409.