User:Smith609/Gotland

Laufield 1974^[1]

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^[2]

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

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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^[3]

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

→ zst-s/mst: Poor exposure. Interbeds in middle, thick seq. in lower.
→ f-vf. ssf
→ 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^[4]

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

^[5]

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^[6]

Assign a Mid-Ludfordian (Upper Ludlow) age to the Burgsvik. Positive $δ$ ¹³C_org excursion during Eke and Burgsvik beds. Could be interpreted as climate (arid vs. wet) controling facies distribution, sea level shifts less important; high $δ$ ¹³C observed in arid deposits.

Sherwood-Pike and Grey^[7]

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.

Reflist

^ Laufeld, S. (1974). Silurian Chitinozoa from Gotland. Fossils and Strata. Universitetsforlaget.
^ Manten, A.A. (1966). "Some problematic shallow-marine structures". Marine Geol. 4 (3): 227–232. doi:10.1016/0025-3227(66)90023-5. Retrieved 2007-06-18.
^ Long, D.G.F. (1993). "The Burgsvik beds, an Upper Silurian storm generated sand ridge complex in southern Gotland". Geologiska Föreningens i Stockholms Förhandlingar (Now GFF). 115 (4): 299–309. doi:10.1080/11035899309453917. ISSN 0016-786X.
^ Stel, J.H. (1977). The Silurian Upper Burgsvik and Lower Hamra-Sundre Beds, Gotland. Rijksmuseum van Geologie en Mineralogie. {{cite book}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
^ Calner, M. (2005-04-01). "A Late Silurian extinction event and anachronistic period". Geology. 33 (4): 305–308. doi:10.1130/G21185.1. {{cite journal}}: Check date values in: |date= (help)CS1 maint: date and year (link)
^ Bassett; et al. (1989). "The Wenlock-Ludlow carbon isotope trend in the Vidukle core, Lithuania, and its relations with oceanic events" (PDF). {{cite journal}}: Cite journal requires |journal= (help); Explicit use of et al. in: |author= (help)
^ Sherwood-pike, M.A. (1985). "Silurian fungal remains: probable records of the class Ascomycetes". Lethaia. 18: 1–20. doi:10.1111/j.1502-3931.1985.tb00680.x. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)

[Laufeld1974-1] Laufeld, S. (1974). Silurian Chitinozoa from Gotland. Fossils and Strata. Universitetsforlaget.

[2] Manten, A.A. (1966). "Some problematic shallow-marine structures". Marine Geol. 4 (3): 227–232. doi:10.1016/0025-3227(66)90023-5. Retrieved 2007-06-18.

[Long1993-3] Long, D.G.F. (1993). "The Burgsvik beds, an Upper Silurian storm generated sand ridge complex in southern Gotland". Geologiska Föreningens i Stockholms Förhandlingar (Now GFF). 115 (4): 299–309. doi:10.1080/11035899309453917. ISSN 0016-786X.

[Stel1977-4] Stel, J.H. (1977). The Silurian Upper Burgsvik and Lower Hamra-Sundre Beds, Gotland. Rijksmuseum van Geologie en Mineralogie. {{cite book}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)

[Calner2005-5] Calner, M. (2005-04-01). "A Late Silurian extinction event and anachronistic period". Geology. 33 (4): 305–308. doi:10.1130/G21185.1. {{cite journal}}: Check date values in: |date= (help)CS1 maint: date and year (link)

[Bassett-6] Bassett; et al. (1989). "The Wenlock-Ludlow carbon isotope trend in the Vidukle core, Lithuania, and its relations with oceanic events" (PDF). {{cite journal}}: Cite journal requires |journal= (help); Explicit use of et al. in: |author= (help)

[Sherwood-pike1985-7] Sherwood-pike, M.A. (1985). "Silurian fungal remains: probable records of the class Ascomycetes". Lethaia. 18: 1–20. doi:10.1111/j.1502-3931.1985.tb00680.x. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)

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Laufield 1974[1]

Manten 1966[2]