User:Smith609/Gotland

==Laufield 1974 ==


 * Succession of Limestones and Shales
 * Shallow shelf above thin (75-125m) Ord. succession
 * 500-200m thick, thickest in south. Oldest @ NW.


 * Shallow epicontinental sea
 * Near equator (Creer 1973)
 * Water depth never > 175-200m (Gray, Laufield & boucot, 1974)
 * Dominated by reefs, starting to grow in Llandovery (sea then 50-100m deep.
 * NW shelf becomes shallower, from bioherm detritus and terriginous infilling. Migration of reef zone to SW, but complicated by sea level change.


 * Burgsvik group:
 * Thin → v thick beds, light grey, fine grained, slightly calcareous, argillaceous sst - intercalated w/ v. thin bedded blue-grey claystone.
 * The sst in places overlain by the "Upper Burgsvik Beds": thin-bedded, light-to-bluish grey, oolitic lst with, in places, alternating sandy beds. These are the ones containing problematic structures (Manten 1966).
 * Strong lateral variation - correltation difficult.

==Manten 1966 ==

Re. the Upper Burgsvic Beds. Age is probably lowermost Devonian (Downtonian)


 * Formed close to the shoreline on a beach "faintly sloping towards the open sea" affected by tides.
 * Evidence
 * Cross-bedding
 * Ripple marks
 * Offshore bars
 * oolites
 * rounded oolite pebbles in ssts and oolites
 * slightly rounded fossils, sorted by size, between sst and uppermost oolite
 * lamellibranch (molluscs?) with thick shells
 * Rare burrows
 * clay lenses (deposited behind low barriers?)
 * erosion channels
 * Pothole-like escavations
 * mud cracks
 * "dendritic patterns of rill marks" - suggest form on beach/unvegetated ground which periodically ran dry.

Manten 1971
Divides Burgsvic beds into 3 members, based on bore-hole. Upper bed varies a little along strike but can be recognised across whole outcrop belt, with distinctive lower contact. Lower beds are exposed at Kullunde 1 & Glasskär 1-3

==Long 1993 ==

Thorough sedimentological analysis. Surmises and challenges sedimentary descriptions:


 * Near-shore sands: Munthe 1910, Manten 1966
 * Locally emergent, offshore bars: Agterberg 1958, Manten 1971
 * beach deposits: Stel & de Coo 1977, Laufield & Bassett
 * Intertidal exposure: Grey et al 1974, Laufield & Martinsson 1981
 * tidal influence: Manten 1966, Stel & de Coo 1977

Contains logs of cores

Microbial origin of unusual wrinkle structures described by Manten 1966.

Lithofacies

 * &rarr; zst-s/mst : Poor exposure. Interbeds in middle, thick seq. in lower.
 * &rarr; f-vf. ssf
 * &rarr; biofacies - oo, onco, bioclastic

Problematic structures

 * wrinkles are kinneyia ripples (Martinsson 1965) or Runzel-marken (Reineck 1969, or wrinkle marks (Reineck & Sing 1973, Allen 1984).
 * Wind stress on freshly deposited seds? Not nec.. soft sed failure of sand beds over mud.

Interpretation
Shoaling sequence - migration of storm dominated sandbanks, or sand-wave complexes.
 * Formation: detatched offshore bars (Swift & Field 1981, Brenner et al 1985)? Isolated bars in mid-shelf (La Fon 1981)?
 * Cross stratification abundant. so can't be tide-dominated.
 * Storm beds abundant. So Storms probably created bars.
 * Prod & scour marks etc irregularly aligned - waves influenced sea floor.

==Stel & de Coo == Detailed Petrographic and paleæoecological analysis of top few metres. sst at top of middle member, and in upper member, deposited @ beach to lower foreshore. Oolites & oncolites in upper strate form, in "agitated shallow marine setting" - minor tidal influence

Calner 2005

 * Anachronistic facies found near Lau event in Late Silurian.
 * Basal Eke Fm. contiains flat-pebble conglomerates

Cherns 1983
In a SGU we don't have.

Jux & Stauber
==Bassett et al 1989 ==

Assign a Mid-Ludfordian (Upper Ludlow) age to the Burgsvik. Positive excursion during Eke and Burgsvik beds. Could be interpreted as climate (arid vs. wet) controling facies distribution, sea level shifts less important; high observed in arid deposits.

==Sherwood-Pike and Grey == Key text.

See

 * Agterberg 1958:254-256 ==1958, Agterberg, F.P.: An undulation of the rate of sedimentation in southern Gotland: Geologie en Mijnbouw, New Series Vol. 20, pp. 253-260.