Jump to content

Engadine Line

Add links
This is a good article. Click here for more information.
From Wikipedia, the free encyclopedia

This is an old revision of this page, as edited by Legobot (talk | contribs) at 19:01, 11 November 2020 (Adding Good Article icon). The present address (URL) is a permanent link to this revision, which may differ significantly from the current revision.

View northwestward towards Maloja Pass. In the foreground passes the Orlegna River, which is deflected southwestwards (left) by the Engadine Line

The Engadine Line is an over 50 kilometres (30 mi) long strike-slip fault in the Swiss canton of Graubünden, which extends into Italy and Austria. It runs along the Engadine Valley (which formed on the fault) and the Bregaglia Valley and offsets Austroalpine and Penninic units in sinistral direction. The western end of the fault appears to peter out into ductile deformation in the Bregaglia Valley or continues as the Gruf Line to the southwest; the eastern end is buried by the Ötztal tectonic block and may continue as the "Inntal fault", "Isar fault" or "Loisach fault".

Total offset along the Engadine Line is about 4–20 kilometres (2–12 mi), decreasing southwest. It began in the Oligocene, but there is evidence of recent neotectonic activity, which resulted in the collapse of the Maloja Pass area at the beginning of the Holocene. Seismic activity occurs along the Engadine Line, and springs and carbon dioxide exhalations in the Engadine are linked to the fault.

Geology

Tectonic map of the Alps, the Engadine Line is marked with "L.E."

The Engadine Line is an over 50 kilometres (30 mi) long[1] northeast-trending fault in southeastern Switzerland.[2] It is a steeply dipping[3] left-lateral strike-slip fault[4] that cuts to a depth of 10 kilometres (6 mi).[5] The total slip on the Engadine Line decreases from 20 kilometres (12 mi) in the Lower Engadine to 3–6 kilometres (2–4 mi) in the Upper Engadine[4] and 1–2 kilometres (0.6–1.2 mi) at Sils, Maloja.[6] The towns of Bever, Maloja, Nauders, S-chanf, Samedan, Sils, St. Moritz, Vicosoprano and Zernez are located along the Engadine Line,[7] as is the Albigna Dam.[8]

The fault trace is generally not recognizable on the surface, as it is buried beneath alluvium; the only outcrops are found at Maloja[9] and at Stragliavita close to Zernez.[10] Parts of the Engadine Line were already recognized by 1914, but it was only in 1977 that they were identified as belonging to a single fault zone,[11] reportedly after a suggestion by a Chinese geologist.[12] Sometimes the names "Nassereith-Silz fault" and "Scuols-Vils fault" are used for the Engadine Line,[13] which was originally also known as Engadiner Spalte.[14]

The Engadine Line deforms the Austroalpine and Penninic nappes[3] and also appears in magnetic anomaly maps.[15] It is responsible for the geologic differences between Graubünden north and south of the Engadine.[12] The Engadine Line is sometimes considered to be a branch of the Periadriatic Fault System.[16] The movement on the Engadine Line is part of a larger tectonic process in the Alps, whereby the mountain range is compressed in north-south direction and is thus squeezed upwards and eastwards.[17] Of the numerous fault zones in the Eastern Alps, the Engadine Line and its northeastern extensions are the longest.[18]

Evidence for a vertical component in fault motion and its interpretation is conflicting;[19] the block southeast of the fault has a down-to-the-east component[4] with normal slip in the northeastern sector of the Engadine Line[20] that may be part of east-west extension in the Alps,[21] while the sector in the Bregaglia Valley features an uplifting northwestern block[22] with reverse slip[20] that may be a recent change in fault motion.[23] Vertical offset on the Engadine Line appears to have opposite direction east and west of Samedan–St. Moritz[24] and has been interpreted as a rotational movement of tectonic blocks.[25] The Churer uplift influenced the western side of the Engadine Line and generated eastward tilting.[26]

Geomorphology

Map showing some toponyms associated with the Engadine Line

In the Lower Engadine, the Engadine Line delimits the Silvretta covers and the Engadine Window from the Ötztal Alps block,[17] which appears to bury the Engadine Line in part.[27] The movement along the Engadine Line may have generated the Engadine Window by exposing Penninic rock units.[28] The Schlining Thrust, which separates the Austroalpine Ötztal unit in the east from the Sesvenna-Campo-Silvretta units in the west,[7] joins the Engadine Line in Austria. On its eastern end the Engadine Line may reach into the Northern Calcareous Alps[29] and can be traced as far as the town of Imst in Austria;[30] it may reach as far as Innsbruck.[31] The Inntal fault is probably the northeastern continuation of the Engadine Line[32] and has a maximum offset of 48 kilometres (30 mi), reaching the Molasse basin.[33] The Loisach[34] and the Isar faults are other candidate prolongations of the Engadine Line;[35] alternatively, the former has been interpreted as a parallel fault that splits up in the Wetterstein Mountains.[18] Later movements in the Ötztal Alps area may have overprinted the trace of the Engadine Line there.[36] It is conjugated with dextral strike-slip faults in the Northern Calcareous Alps.[37]

The Inn River valley formed along the Engadine Line.[16] There, the fault runs e.g between the villages La Punt and St. Moritz.[30] In the Samedan area, geologic research has found evidence of releasing bends and restraining bends associated with Miocene movement along the Engadine Line,[38] as well as of normal faults linked to the Engadine Line.[39] At Zernez the river departs the Engadine Line before returning at Scuol.[40] The Engadine Line might form the northwestern border of the Scarl-Campo rock units.[41] The combined effects of glacial erosion and slip along the Engadine Line generated the Lej da Segl, Lej da Silvaplauna, Lej da Champfèr and Lej da San Murezzan lakes which are traversed by the Inn River.[26]

In the Upper Engadine and the Maloja Pass area the Engadine Line is represented by 0.5–9 kilometres (0.3–5.6 mi) long northeast-trending and 0.3–2 kilometres (0.2–1.2 mi) long east-west trending fault segments which form scarps. Depressions located between the fault traces are occupied by lakes such as Silsersee, Silvaplanersee and St. Moritzsee, which do not appear to be moraine-dammed[42] and may have been formed by the activity of the Engadine Line.[16] Close to the Maloja Pass the Engadine Line forms a single fault.[43] In the Forno Valley the fault crops out in the form of polished surfaces, scarps and striations along with fault gouge.[43] The course of the Orlegna River is diverted by a shutter ridge at the intersection with the Engadine Line.[22] There, the Engadine Line runs along the southern side of the Inn and Bregaglia Valleys and is accompanied by deep-seated mass failures; eventually it disappears under sediments[43] close to Promontogno.[31] As with the Inn Valley, the Bregaglia Valley is the surface expression of the Engadine Line.[11]

The Engadine Line continues as the "Gruf Line", which runs along the southern side of the valley, accompanied by deep-seated mass failures[43] which obscure the surface presentation of the Gruf Line,[44] and crosses into Italian territory.[2] The Gruf Line appears to be based in deeper, more ductile crustal domains than the Engadine Line, and it is possible that part of the offset is taken up by ductile stress along the Bregaglia Valley.[4] Alternative interpretations see the Gruf Line as a mylonite zone,[3] identify another lineament between Maloja and Chiavenna, or prolong the Engadine Line to Chiavenna and even farther.[31] The Gruf line separates the Gruf migmatites from the Chiavenna ophiolites and the Tambo nappe.[43] It and the Gruf Line accommodate the exhumation of the Bergell pluton,[45][46] which was tilted to the east between the Engadine Line and the Periadriatic Line.[3]

A transition from brittle faulting on the Engadine Line to ductile deformation in the western Bregaglia Valley might explain why the Engadine Line does not appear to continue there.[9] Deformation in rock formations of the Bregaglia Valley may related to activity of the Engadine Line.[47] Structural lineaments related to the Engadine Line can be traced as far as the Valle San Giacomo west of the Bregaglia.[48]

Geologic history

Geology of the Alps
The Alps
The Alps
Tectonic subdivision
Formation and rocks
Geological structures
Paleogeographic terminology

icon Alps portal

icon Geology portal

Movement along the Engadine Line commenced during or before the late Oligocene[49] but post-dates the cooling of the Bergell pluton 28 million years ago.[3] Movement took place during the Oligocene[50] before probably ceasing during the Miocene[51] and has been attributed to the so-called "Turba phase" of extensional development of the Alps.[52] The movement along the Engadine Line and Inntal faults influenced the course of the Inn River,[49][53] allowed its watershed to expand southwestwards,[54] and altered drainages during the Sarmatian.[55]

Neotectonics

There is very little information on the recent activity of the Engadine Line.[56] Detecting faults in the Alps is difficult, as glacial and fluvial erosion as well as gravitational processes and landslides quickly erase evidence of tectonic processes.[2] Earthquakes are often poorly documented in the thinly populated Alps; they tend to be weak and often cannot be linked to specific faults.[57]

There are only few indications of recent activity, and it is not agreed upon that it was active during the Upper Pleistocene-Holocene,[56] although evidence of Quaternary movement is widely found.[58] The Engadine Line and other lineaments delimit a fast uplifting area of the Central Alps.[59] In the Val Laschadura, close to Zernez, post-glacial faulting is recorded.[40][60] Traces of multiple glaciations are preserved in the Forno Valley. Deposits left by the most recent glaciation are unaffected by tectonic activity at the Engadine Line,[61] but the Orlegna River has not yet recovered from the impact of faulting, implying that movement along the Engadine Line there took place before 14,500 years ago but in the Late Pleistocene. Fault scarps in the Inn Valley associated with the Engadine Line have been degraded by glaciation.[44] On the other hand, sackungen in the Bregaglia Valley which post-date the last glacial maximum have been linked to tectonic activity on the Gruf Line,[61] which otherwise shows no evidence of Quaternary activity.[44] The deformation in the western Inn Valley-Bregaglia Valley may be of gravitational origin, however,[62] although earthquakes on the Engadine Line may have triggered their movement.[23]

The "beheading" of the Inn Valley at Maloja Pass, which took place between 29,400–14,500 years before present,[44] is one of the major geologic events in the Quaternary of this sector of the Alps. Three valleys that formerly presumably fed the Inn Glacier were redirected into the Bregaglia Valley by a large collapse that caused the "beheading". Tectonic stresses exercised by movements along the Engadine Line may have caused the collapse,[62] which left a steep escarpment at Maloja Pass and a large elevation difference between the Inn and Bregaglia valleys.[23]

Seismicity

It is possible, but unproven, that the Engadine Line may generate earthquakes.[63] Minor seismic activity occurs in the Engadine[64] and appears to relate, in part, to northeast-southwest trending structures[65] such as the Engadine Line.[66] Earthquakes have been localized to the Engadine Line, but they are not intense, and seismicity disappears into the Inn Valley, where the Engadine Line fault continues.[2] It decreases southwestwards away from the central and eastern Engadine.[62] Seismic activity in the Venosta Valley may be related to the intersection between the Engadine Line and a north-south trending fault.[67]

Turbidites in Lake Como and Lake Sils, dated to have occurred in AD 700, may relate to Engadine earthquakes.[68] In the Ötz River valley in Austria, the Engadine Line and the Inntal fault have been related to increased earthquake activity, which may explain the occurrence of frequent landslides in the area.[69] Research published in 1979 indicated that earthquakes on the Engadine Line might reach a maximum magnitude of M 5.5[13] or 6.9 with a break length of 40 ± 10 kilometres (24.9 ± 6.2 mi).[70]

Exhalations and springs

Hydrothermal activity has been associated with recent activity on the Engadine Line.[56] In the Scuol-Tarasp area, mineral water and carbon dioxide rise to the surface (the latter forming mofettes)[71] along the Engadine Line and its intersection with more local geologic lineaments.[72] The waters most likely form along the plane of the fault.[73]

References

  1. ^ Wexsteen, Pierre; Jaffé, Felice C.; Mazor, Emanuel (30 December 1988). "Geochemistry of cold CO2-rich springs of the Scuol-Tarasp region, Lower Engadine, Swiss Alps". Journal of Hydrology. 104 (1): 82. doi:10.1016/0022-1694(88)90158-8. ISSN 0022-1694.
  2. ^ a b c d Tibaldi & Pasquarè 2008, p. 475.
  3. ^ a b c d e Ciancaleoni & Marquer 2008, p. 5.
  4. ^ a b c d Tibaldi & Pasquarè 2008, p. 477.
  5. ^ Schlüchter, Lozza & Haller 2021, p. 252.
  6. ^ Ring 1994, p. 823.
  7. ^ a b Schmid & Froitzheim 1993, pp. 570–571.
  8. ^ Gimenes, Evandro; Fernández, Gabriel (2006-03-01). "Hydromechanical analysis of flow behavior in concrete gravity dam foundations". Canadian Geotechnical Journal. 43 (3): 248. doi:10.1139/t05-095. ISSN 0008-3674.
  9. ^ a b Schmid & Froitzheim 1993, p. 573.
  10. ^ Schmid & Froitzheim 1993, p. 574.
  11. ^ a b Schmid & Froitzheim 1993, p. 571.
  12. ^ a b Şengör, A. M. Celâl; Bernoulli, Daniel (July 2011). "How to stir a revolution as a reluctant rebel: Rudolf Trümpy in the Alps". International Journal of Earth Sciences. 100 (5): 927. doi:10.1007/s00531-011-0648-0. S2CID 129649579.
  13. ^ a b Drimmel, J. (10 June 1979). "On the assessment of maximum earthquakes in the alps and adjacent areas". Tectonophysics. 55 (3): T4. doi:10.1016/0040-1951(79)90176-8. ISSN 0040-1951.
  14. ^ MATTMÜLLER 1996, p. 47.
  15. ^ Gurk, Marcus (October 1999). "Magnetic distortion of GDS transfer functions: An example from the Penninic Alps of Eastern Switzerland revealing a crustal conductor". Earth, Planets and Space. 51 (10): 1031. doi:10.1186/BF03351576. S2CID 129098757.{{cite journal}}: CS1 maint: unflagged free DOI (link)
  16. ^ a b c Ilyashuk, Boris; Gobet, Erika; Heiri, Oliver; Lotter, André F.; van Leeuwen, Jacqueline F. N.; van der Knaap, Willem O.; Ilyashuk, Elena; Oberli, Florencia; Ammann, Brigitta (1 June 2009). "Lateglacial environmental and climatic changes at the Maloja Pass, Central Swiss Alps, as recorded by chironomids and pollen". Quaternary Science Reviews. 28 (13): 1341. doi:10.1016/j.quascirev.2009.01.007. ISSN 0277-3791.
  17. ^ a b Frisch, Dunkl & Kuhlemann 2000, p. 248.
  18. ^ a b Tollmann 1977, p. 6.
  19. ^ Schmid & Froitzheim 1993, p. 572.
  20. ^ a b Ring 1994, p. 815.
  21. ^ Selverstone, Jane (31 May 2005). "Are the Alps Collapsing?". Annual Review of Earth and Planetary Sciences. 33 (1): 120. doi:10.1146/annurev.earth.33.092203.122535. ISSN 0084-6597.
  22. ^ a b Tibaldi & Pasquarè 2008, p. 479.
  23. ^ a b c Tibaldi & Pasquarè 2008, p. 486.
  24. ^ Schmid & Froitzheim 1993, p. 580.
  25. ^ Ring 1994, p. 813.
  26. ^ a b Gobet, E.; Tinner, W.; Hochuli, P. A.; van Leeuwen, J. F. N.; Ammann, B. (1 October 2003). "Middle to Late Holocene vegetation history of the Upper Engadine (Swiss Alps): the role of man and fire" (PDF). Vegetation History and Archaeobotany. 12 (3): 144. doi:10.1007/s00334-003-0017-4. S2CID 53964424.
  27. ^ Linzer et al. 2002, p. 220.
  28. ^ Frisch, Dunkl & Kuhlemann 2000, p. 259.
  29. ^ JANOSCHEK, WERNER R.; MATURA, ALOIS (1980). "Outline of the Geology of Austria" (PDF). Abb.. Geol. B.-A. 26e C. G. I. 34. Wien: 35.
  30. ^ a b Hornung, J.; Pflanz, D.; Hechler, A.; Beer, A.; Hinderer, M.; Maisch, M.; Bieg, U. (1 March 2010). "3-D architecture, depositional patterns and climate triggered sediment fluxes of an alpine alluvial fan (Samedan, Switzerland)". Geomorphology. 115 (3): 204. doi:10.1016/j.geomorph.2009.09.001. ISSN 0169-555X.
  31. ^ a b c Sciesa 1991, p. 24.
  32. ^ Linzer et al. 2002, p. 212.
  33. ^ Linzer et al. 2002, p. 221.
  34. ^ Mählmann, Rafael Ferreiro; Morlok, Jürgen (1992). "DAS WETTERSTEINGEBIRGE, WIDERLAGER DER ALLOCHTHONENINNTALDECKE, UND DIE ÖTZTALMASSE, MOTOR TERTIÄRER POSTHUMERNW-BEWEGUNGEN IM MIEMINGER GEBIRGE(NORDTIROL, ÖSTERREICH)" (PDF). Geol. Paläont. Mitt. Innsbruck (in German). 18: 22. ISSN 0378-6870.
  35. ^ MATTMÜLLER 1996, p. 67.
  36. ^ Schmid & Froitzheim 1993, p. 590.
  37. ^ Ratschbacher, Lothar; Frisch, Wolfgang; Linzer, Hans-Gert; Merle, Olivier (1991). "Lateral extrusion in the eastern Alps, PArt 2: Structural analysis". Tectonics. 10 (2): 259. doi:10.1029/90TC02623.
  38. ^ Handy, M. R. (1 December 1996). "The transition from passive to active margin tectonics: a case study from the zone of Samedan (eastern Switzerland)". Geologische Rundschau. 85 (4): 839. doi:10.1007/BF02440114. ISSN 1432-1149. S2CID 129703854.
  39. ^ Masini, Emmanuel; Manatschal, Gianreto; Mohn, Geoffroy; Unternehr, Patrick (1 September 2012). "Anatomy and tectono-sedimentary evolution of a rift-related detachment system: The example of the Err detachment (central Alps, SE Switzerland)". GSA Bulletin. 124 (9–10): 1538. doi:10.1130/B30557.1. ISSN 0016-7606.
  40. ^ a b Schlüchter, Lozza & Haller 2021, p. 257.
  41. ^ Gosso, Guido; Spalla, Maria; G.B, Siletto; Berra, Fabrizio; Bini, Alfredo; Forcella, F (2012). "Note illustrative della Carta Geologica d'Italia alla scala 1:50.000. Foglio 057 - Malonno" (in Italian). I.S.P.R.A. p. 16 – via ResearchGate.
  42. ^ Tibaldi & Pasquarè 2008, pp. 477–478.
  43. ^ a b c d e Tibaldi & Pasquarè 2008, p. 478.
  44. ^ a b c d Tibaldi & Pasquarè 2008, p. 484.
  45. ^ Schmid & Froitzheim 1993, p. 588.
  46. ^ Ciancaleoni & Marquer 2008, p. 4.
  47. ^ Sciesa 1991, p. 23.
  48. ^ Ferrari, F.; Apuani, T.; Giani, G. P. (2011). "Applicazione di modelli cinematici per lo studio di frane di crollo in media Val San Giacomo (SO)" (in Italian). p. 56 – via ResearchGate.
  49. ^ a b Brügel et al. 2003, p. 555.
  50. ^ Linzer et al. 2002, p. 233.
  51. ^ Bernoulli, Daniel; Laubscher, Hans Peter; Trümpy, Rudolf; Wenk, Eduard (1 January 1974). "Central Alps and Jura Mountains". Geological Society, London, Special Publications. 4 (1): 89. doi:10.1144/GSL.SP.2005.004.01.06. ISSN 0305-8719. S2CID 129463690.
  52. ^ Ferreiro Mählmann, Rafael; Giger, Matthias (July 2012). "The Arosa zone in Eastern Switzerland: oceanic, sedimentary burial, accretional and orogenic very low- to low grade patterns in a tectono-metamorphic mélange" (PDF). Swiss Journal of Geosciences. 105 (2): 206. doi:10.1007/s00015-012-0103-7. S2CID 140725911.
  53. ^ Skeries 2007, p. 229.
  54. ^ Brügel et al. 2003, p. 556.
  55. ^ Skeries 2007, p. 233.
  56. ^ a b c Onida et al., p. 6.
  57. ^ Tibaldi & Pasquarè 2008, pp. 475–476.
  58. ^ Tollmann 1977, p. 7.
  59. ^ Sternai, Pietro; Sue, Christian; Husson, Laurent; Serpelloni, Enrico; Becker, Thorsten W.; Willett, Sean D.; Faccenna, Claudio; Di Giulio, Andrea; Spada, Giorgio; Jolivet, Laurent; Valla, Pierre; Petit, Carole; Nocquet, Jean-Mathieu; Walpersdorf, Andrea; Castelltort, Sébastien (1 March 2019). "Present-day uplift of the European Alps: Evaluating mechanisms and models of their relative contributions". Earth-Science Reviews. 190: 591. doi:10.1016/j.earscirev.2019.01.005. hdl:10281/229017. ISSN 0012-8252.
  60. ^ Schlüchter, Ch.; Clausen, M.; Stadelmann, F.; Kissling, E. (2013). "Tektonik. Das bewegte und gestapelte Gebirge". In Haller, H.; Eisenhut, A.; Haller, R. (eds.). Atlas des Schweizerischen Nationalparks. Die ersten 100 Jahre. Nat.park.-Forsch. Schweiz. Vol. 99. Bern: Haupt Verlag.
  61. ^ a b Tibaldi & Pasquarè 2008, p. 480.
  62. ^ a b c Tibaldi & Pasquarè 2008, p. 485.
  63. ^ Wiemer, Stefan; García-Fernández, Mariano; Burg, Jean-Pierre (May 2009). "Development of a seismic source model for probabilistic seismic hazard assessment of nuclear power plant sites in Switzerland: the view from PEGASOS Expert Group 4 (EG1d)". Swiss Journal of Geosciences. 102 (1): 196. doi:10.1007/s00015-009-1311-7. hdl:20.500.11850/381002. S2CID 128683508.
  64. ^ Carulli & Slejko 2009, p. 213.
  65. ^ Onida et al., p. 11.
  66. ^ Agliardi, Federico; Crosta, Giovanni B.; Zanchi, Andrea; Ravazzi, Cesare (1 January 2009). "Onset and timing of deep-seated gravitational slope deformations in the eastern Alps, Italy". Geomorphology. 103 (1): 116. doi:10.1016/j.geomorph.2007.09.015. ISSN 0169-555X.
  67. ^ Carulli & Slejko 2009, p. 2002.
  68. ^ Fanetti, Daniela; Anselmetti, Flavio S.; Chapron, Emmanuel; Sturm, Michael; Vezzoli, Luigina (24 March 2008). "Megaturbidite deposits in the Holocene basin fill of Lake Como (Southern Alps, Italy)". Palaeogeography, Palaeoclimatology, Palaeoecology. 259 (2): 337–338. doi:10.1016/j.palaeo.2007.10.014. ISSN 0031-0182.
  69. ^ Ostermann, Marc; Prager, Christoph. "Holozäne "Bergstürze" in der Region Oberinntal-Ötztal (Tirol, Österreich)" [Major Holocene rock slope failures in the Upper Inn- and Ötz valley region (Tyrol, Austria)]. p. 118 – via ResearchGate.
  70. ^ Schmid, Stefan M.; Slejko, Dario (May 2009). "Seismic source characterization of the Alpine foreland in the context of a probabilistic seismic hazard analysis by PEGASOS Expert Group 1 (EG1a)" (PDF). Swiss Journal of Geosciences. 102 (1): 144. doi:10.1007/s00015-008-1300-2. S2CID 128955838.
  71. ^ Schotterer et al. 1987, p. 277.
  72. ^ Schotterer et al. 1987, p. 278.
  73. ^ Schotterer et al. 1987, p. 283.

Sources

Retrieved from "https://en.wikipedia.org/w/index.php?title=Engadine_Line&oldid=988202973"