Tvaren - Hypervelocity Impact Crater

Alternate Names Tvaren Bay
Local Language
Coordinates 58° 46' 31" N; 17° 25' 12" E
Notes
  1. ~70 km SSW of Stockholm in a bay.
Country Sweden
Region Södermanland
Date Confirmed 1994
Notes
  1. Crater structure revealed through continuous seismic reflection profiling (Floden et al., 1986), but first confirmed evidence for shock was in 1994 (Lindström et al., 1994).
Buried? Yes
Notes
  1. Underwater
Drilled? Yes
Notes
  1. 2 drill holes.
Target Type Mixed
Notes
  1. Impact penetrated sediments into basement. Ordovician limestones, Proterozoic migmatites and dolerites (Lindstom, 1992). (Ormö et al., 2007) reconstructs a target of 0.020-0.030km of Cambrian sand and 0.030-0.040km of Ordovician limestone atop Precambrian crystalline basement. See Fig. 5 therein.
Sub-Type Carbonate, Dolerite, Limestone, Migmatite
Apparent Crater Diameter (km) 3.1 km
Age (Ma) 456 - 458
Notes :
  1. ~458 Ma based on biostratigraphic constraints (Örmo, 1994) (Grahn et al., 1996). The age can also be constrained based on fossils in infilling sediments (Lindstom and Sterkell, 1992) (Grahn and Nolvak, 1993). *Maximum age is poorly constrained. (Holm-Alwmark, 2021) places youngest age at 456 Ma based on updated International Chronostratigraphic Chart (Cohen et al., 2013).

Method :
  1. Stratigraphy
Impactor Type Unknown

Advanced Data Fields

Notes

Erosion
4
  1. Impact in area of sedimentation. Crater buried after impact. No topographic expression of a rim today (Holm-Alwmark, 2021).
Final Rim Diameter
2 km
Apparent Rim Diameter
3.1 km
  1. Continuous seismic reflection of 2000 m wide circular depression (Floden et al., 1986). The fractured part of the structure has a diameter of almost 3.1 km which reaches 500 m outside the present underwater topographic perimeter (Henkel et al., 2010).
Rim Reliability Index
2
  1. Depression surrounded by a wall (Floden et al., 1986).
Crater Morphology
Simple
Central Uplift Diameter
km
Central Uplift Height
Unknown
Uplift Reliability Index
Structural Uplift
Unknown
Thickness of Seds
0.05-0.07
Target Age
Precambrian Palaeozoic
Marine
No
Impactor Type
Other Shock Metamorphism
No
Shatter Cones
No
Planar Fractures
No
Planar Deformation Features
Yes
  1. PDF in quartz and feldspar (Lindstrom et al., 1994).
Diaplectic Glass
Yes
  1. (Ormo and Tornberg, 1994)
Coesite
No
Stisovite
No
Crater Fill
LB, MB
  1. Melt has been found as tiny fragments. Crater-fill polymict lithic breccias are reported (Tornberg and Sturkell, 2005 and references therein).
Proximal Ejecta
Distal Ejecta
Dykes
Volume of Melt
Depth of Melting

References

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T Flodén, P Tunander, F E Wickman (1986) The Tvären Bay structure, an astrobleme in Southeastern Sweden, GFF 108(3), p. 225-234, doi:10.1080/11035898609454687

L B Pedersen, T M Rasmussen, D Dyrelius (1990) Construction of component maps from aeromagnetic total field anomaly maps from aeromagnetic total field anamoly maps 1, Geophysical Prospecting 38(7), doi:10.1111/j.1365-2478.1990.tb01875.x

H Henkel, L J Pesonen (1992) Impact craters and craterform structures in Fennoscandia, Technophysics 216, p. 31-40

Y Grahn, J Nölvak (1993) Chitinozoan dating of Ordovician impact events in Sweden and Estonia. A preliminary note, GFF 115(3), p. 263-264, doi:10.1080/11035899309452758

M Lindström, T Flodén, Y Grahn, B Kathol (1994) Post-impact deposits in Tvären, a marine Middle Ordovician crater south of Stockholm, Sweden, Geological Magazine 131(1), p. 91-103, doi:10.1017/S0016756800010529

J Ormö (1994) The pre-impact Ordovician stratigraphy of the Tvären Bay impact structure, SE Sweden, GFF 116(3), p. 139-144, doi:10.1080/11035899409546176

E L Tullborg, S A Larson, L Bjorklund, L Samuelsson, J Stigh (1995) Thermal evidence of Caledonide foreland, molasse sedimentation in Fennoscandia: Technical Report 95-18, p. 1-46, url

Jens Ormö, G Blomqvist (1996) Magnetic modelling as a tool in the evaluation of impact structures, with special reference to the Tvären Bay impact crater, SE Sweden, Tectonophysics 262(1-4), p. 291-300, Elsevier, Amsterdam

Y Grahn, J Nolvak, F Paris (1996) Precise chitinozoan dating of Ordovician impact events in Baltoscandia, Journal of Micropalaeontology 15, Part 1, p. 21-35, British Micropalaeontological Society, London, doi:http://dx.doi.org/10.1144/jm.15.1.21

M Lindström, J Ormö, E F F Sturkell, R Törnberg (1996) Geological information from Ordovician marine impact craters, GFF 118(sup004), p. 99-100, Informa UK Limited, doi:10.1080/11035899609546419

R Törnberg (1996) Impact‐related resurge sedimentology as exemplified by the Lockne, Tvären and Kärdla structures, GFF 118(sup004), p. 103-103, Informa UK Limited, doi:10.1080/11035899609546424

Å Wallest, S E Hagenfeldt (1996) Biostratigraphical investigation of middle ordovician acritarchs in the post-impact sequence in the tvären-2 core, Sweden, GFF 118(2), p. 79-82, doi:10.1080/11035899609546232

R Törnberg, E F F Sturkell (2005) Density and magnetic susceptibility of rocks from the Lockne and Tvären marine impact structures, Meteoritics & Planetary Science 40(4), p. 639-651, Meteoritical Society, Fayetteville, AR

B W H Hendriks, T F Redfield (2005) Apatite fission track and (U-Th)/He data from Fennoscandia: an example of underestimation of fission track annealing in apatite, Earth and Planetary Science Letters 236(1-2), url, doi:10.1016/j.epsl.2005.05.027

Å M Frisk, J Ormö (2007) Facies distribution of post-impact sediments in the Ordovician Lockne and Tvären impact craters; indications for unique impact-generated environments, Meteoritics & Planetary Science 42(11), Jens Ormo, Alexander Deutsch (ed.), p. 1971-1984, Meteoritical Society, Fayetteville, AR

J Ormö, E Sturkell, M Lindström, A Lepinette (2007) Resurge dynamics at the Lockne and Tvären marine-target impact craters analysed with sedimentological and numerical methods, Lunar and Planetary Science XXXVIII

J Ormö, E Sturkell, M Lindström (2007) Sedimentological analysis of resurge deposits at the Lockne and Tvären craters: Clues to flow dynamics, Meteoritics & Planetary Science 42(11), p. 1929-1943, url

J Ormö, A Lepinette, E Sturkell, M Lindstrom, K R Housen, K A Holsapple (2010) Water resurge at marine-target impact craters analyzed with a combination of low-velocity impact experiments and numerical simulations, Special Paper - Geological Society of America 465, Roger L Gibson, Wolf Uwe Reimold (ed.), p. 81-101, Geological Society of America (GSA), Boulder, CO, url, doi:http://dx.doi.org/10.1130/2010.2465(06

H Henkel, T C Ekneligoda, S Aaro (2010) The extent of impact induced fracturing from gravity modeling of the Granby and Tvären simple craters, Tectonophysics 485(1-4), p. 290-305, doi:10.1016/j.tecto.2010.01.008

J Ormö, A C Hill, J M Self-Trail (2010) A chemostratigraphic method to determine the end of impact-related sedimentation at marine-target impact craters (Chesapeake Bay, Lockne, Tvären), Meteoritics and Planetary Science 45(7), p. 1206-1224, University of Arkansas, url, doi:10.1111/j.1945-5100.2010.01084.x

M E Eriksson, Å M Frisk (2011) Polychaete palaeoecology in an early Late Ordovician marine astrobleme of Sweden, Geological Magazine 148(2), p. 269-287, Cambridge University Press, London, url, doi:http://dx.doi.org/10.1017/S0016756810000579

Å M Frisk, D A T Harper (2011) Palaeoenvironmental aspects of Late Ordovician Sericoidea shell concentrations in an impact crater, Tvären, Sweden, Lethaia 44(4), p. 383-396, doi:10.1111/j.1502-3931.2010.00250.x

Å M Frisk, D A T Harper (2013) Late Ordovician brachiopod distribution and ecospace partitioning in the Tvären crater system, Sweden, Palaeogeography, Palaeoclimatology, Palaeoecology 369, p. 114-124, url, doi:10.1016/j.palaeo.2012.10.008

E Flamini, A Coletta, M L Battagliere, M Virelli (2019) Tvären, Sweden, Encyclopedic Atlas of Terrestrial Impact Craters, p. 435-437, Springer International Publishing, doi:10.1007/978-3-030-05451-9_118