Closeup of glacial till. Note that the larger grains (pebbles and gravel) in the till are completely surrounded by the matrix of finer material (silt and sand), and this characteristic, known as matrix support, is diagnostic of till.

Glacial till with tufts of grass

Till after avalanche, Norway

Till or glacial till is unsorted glacial sediment. Glacial drift is a general term for the coarsely graded and extremely heterogeneous sediments of glacial origin. Glacial till is that part of glacial drift which was deposited directly by the glacier. Its content may vary from clays to mixtures of clay, sand, gravel and boulders. This material is mostly derived from the subglacial erosion and entrainment by the moving ice of the glaciers of previously available unconsolidated sediments. Bedrock can also be eroded through the action of glacial plucking and abrasion and the resulting clasts of various sizes will be incorporated to the glacier's bed. Eventually, the sedimentary assemblage forming this bed will be abandoned some distance down-ice from its various sources. This is the process of glacial till deposition. When this deposition occurs at the base of the moving ice of a glacier, the sediment is called lodgement till. Rarely, eroded unconsolidated sediments can be preserved in the till along with their original sedimentary structures. More commonly, these sediments lose their original structure through the mixture processes associated to the subglacial transport and they solely contribute to form the more or less uniform matrix of the till.

Till is deposited at the terminal moraine, along the lateral and medial moraines and in the ground moraine of a glacier. As a glacier melts, especially a continental glacier, large amounts of till are washed away and deposited as outwash in sandurs by the rivers flowing from the glacier and as varves in any proglacial lakes which may form. Till may contain detectable concentrations of gems or other valuable ore minerals picked up by the glacier during its advance, for example the diamonds found in the American states of Wisconsin, Indiana, and in Canada. Prospectors use trace minerals in tills as clues to follow the glacier upstream to find kimberlite diamond deposits and other types of ore deposits.

Tillite[link]

In cases where till has been indurated or lithified by subsequent burial into solid rock, it is known as the sedimentary rock tillite. Matching beds of ancient tillites on opposite sides of the south Atlantic Ocean provided early evidence for continental drift. The same tillites also provide some support to the Precambrian Snowball Earth glaciation event hypothesis.

Types of till[link]

There are various types of classifying tills:

• primary deposits – these were laid down directly by glacier action
• secondary deposits – these have undergone reworking (e.g. fluvial transport, erosion, etc.)

Traditionally (e.g. Dreimanis, 1988^[1]) a further set of divisions has been made to primary deposits, based upon the method of deposition.

• Lodgement tills – sediment which has been deposited by plastering of glacial debris from a sliding glacier bed.
• Deformation tills – Sediment which has been disaggregated and (usually) homogenised by shearing in the sub glacial deformed layer.
• Melt out tills – Released by melting of stagnant or slowly moving debris-rich glacier ice and deposited without subsequent transport or deformation. Split up into sub glacial melt out till (melting of debris rich ice at the bottom of the glacier) and supraglacial melt-out till (melting of ice on the glacier surface).
• Sublimation till – similar to melt out till, except the ice is lost through sublimation rather than melt. Often occurs only in extremely cold and arid conditions, mainly in Antarctica.

Van der Meer et al. 2003^[2] have suggested that these till classifications are outdated and should instead be replaced with only one classification, that of deformation till. The reasons behind this are largely down to the difficulties in accurately classifying different tills, which are often classified based on inferences of the physical setting of the till rather than till fabric or particle size analysis data.

See also[link]

Look up till in Wiktionary, the free dictionary.

Wikimedia Commons has media related to: Till

• Moraine
• Boulder clay
• Diamictite

References[link]

Daniel Trevor Christian (born 4 May 1983 in Camperdown, New South Wales) is an Australian cricketer who currently plays for Australia and South Australia.On 5 June 2010 he joined Hampshire Royals for the Friends Provident T20. Christian is known as a powerful hitter, and also bowls medium pace occasionally, CricInfo's Peter English described him as a "natural all-rounder." His inclusion is seen as a landmark to Aboriginal inclusiveness in Australian cricket.^[1]

Early life[link]

Born in 1983, Christian grew up in the town of Narrandera in the Riverina region of New South Wales and is of indigenous ancestry (Wiradjuri).^[1] He lived in Narrandera until he completed Primary School and then he moved to Sydney and attended St Gregory's College, Campbelltown.

Cricket career[link]

In 2003 Christian attended the Australian Cricket Academy.^[2]

Christian played List A cricket for New South Wales in 2006 and 2007. After he was not offered a new contract for the 2007-08 season he moved to South Australia where he soon found himself playing first-class cricket for the state team .^[3]

In 2009 Christian captained an Indigenous Australian cricket team that toured England.^[4] Cricinfo noted that "With the bat Christian can be brutal, particularly when aiming at Adelaide's square boundaries, and he is one of those rare strikers whose eyes don't need a warm-up ball."^[1] He was brought into Australia's Twenty20 "following a series of brutal, clever and consistent performances."^[1]

On 23 February 2010, he made his Twenty20 International debut against the West Indies and was a member of Australia's squad for the 2010 ICC World Twenty20.

Christian played for Hampshire in their victorious 2010 Twenty20 Cup campaign.

Additionally, Christian is a part of the Deccan Charger's team which competes annually in the DLF IPL - he was purchased for 900,000 USD.^[5]

On 2 March 2012, he took figures of 5/39 which included a hat-trick in an ODI match against Sri Lanka at the MCG. Despite his impressive figures, Australia were unable to win the match.

References[link]

External links[link]

• Player profile: Daniel Christian from ESPNcricinfo

v t e Australia squad – 2010 ICC World Twenty20 (runners-up) 7 White 11 Nannes 23 Clarke (c) 25 Johnson 29 D. Hussey 31 Warner 32 Tait 33 Watson 36 Paine 43 Hauritz 48 M. Hussey 49 Smith 54 Christian 57 Haddin 45 Harris Coach: Nielsen Brett Lee was injured at the beginning of the tournament and was replaced by Ryan Harris.

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