Solund Basin
| Solund Basin | |
|---|---|
 Геологическая карта бассейна Солунд (NSD = отряда Nordfjord-Sogn ) | |
| Координаты | 61 ° 08´N 4 ° 53IBRATED / 61,14 ° N 4,88 ° E |
| Этимология | Солуд |
| Область | Вестленд |
| Страна | Норвегия |
| Характеристики | |
| ВКЛ/Оффшор | На берегу |
| Область | 800 км 2 (310 кв. МИ) |
| Геология | |
| Age | Devonian |
| Faults | Solund Detachment |
Бассейн Солунд представляет собой осадочный бассейн, содержащий по меньшей мере 6 км в основном грубых конгломератов возраста девонского . Это самая южная из группы бассейнов аналогичного возраста, обнаруженного вдоль юго-западного побережья Норвегии между Согнефьордом и Нордфьордом , разработанным в подвесной стене отряда Нордфьорда-Сона . Он был сформирован в результате удлиненной тектоники во время построгенного коллапса коры, утолщенного во время каледонской орогеники , к концу силурийского периода . Он назван в честь муниципалитета Солунд в Вестленде .
Тектоническая настройка
[ редактировать ]During the later part of the Silurian period, the western margin of the Baltic Plate was affected by the main collisional event of the Caledonian orogeny, known as the Scandian phase. This led to large-scale thrusting and the development of a mountain belt similar in scale to the Himalayas. Soon after the collision finished during the Early Devonian, the thickened crust began to extend. Initially the extension took place by reactivation of Caledonian thrust faults, known as Mode 1 extension. The uplift and exhumation led to a reduction of dip in these reactivated thrusts, making them progressively less mechanically viable. At this point Mode II extension took over, with development of large extensional shear zones that cross-cut the Caledonian thrust pile, such as the Nordfjord-Sogn Detachment.[1]
Extent
[edit]The preserved part of the Solund Basin covers about 800 km2, including most of the islands of Ytre Sula, Steinsundøyna, Sula, Losna, many other smaller islands and the mainland peninsula on which the mountain of Lihesten lies.[2]
Basin fill
[edit]The dominant lithology is conglomerate, with some breccia and subordinate amounts of sandstone, organised into somewhat irregular cycles of coarsening up and then fining on a scale of tens of metres up to more than 100 m.[3] The conglomerate is typically very coarse, consisting of cobble to boulder sized clasts. A strong depositional fabric is present with clast long axes showing a marked preferred orientation of northwest–southeast, often with well-developed imbrication.[2]
Hersvik landslides
[edit]In the area around Hersvikbygda, towards the north of the island of Sula, a series of large exotic lenticular bodies are found within the conglomerates towards the base of the sequence. They consist of a wide range of lithologies, including mafic and felsic volcanics, granite, diorite, gabbro and metasediments. When they were first described in 1926, they were interpreted as small thrust sheets involving the emplacement of slices of the underlying upper allochthon rocks beneath the basal unconformity into the conglomerate sequence. Later investigations failed to find any evidence for tectonic contacts at the base of the lenses and one large body of monomict brecciated gabbro was interpreted as a debris flow. At the base of one of the lenses a body of rhyolite was interpreted as a contemporaneous Devonian lava flow, the only example of volcanism of that age described from Norway. A reappraisal of these deposits, including dating the rhyolite body as Silurian, has interpreted all of these bodies as landslides, probably derived from rocks of the Solund-Stavfjord Ophiolite Complex on the basin margin to the north.[4]
Similar landslide deposits have also been recognised from the southeastern boundary of the basin near Kråkevåg, at the highest preserved stratigraphic level, demonstrating that such landslides were active throughout the deposition of the preserved part of the basin.[4]
Structure
[edit]In the southeastern part of the basin, the conglomerate sequence dips 20–25° to the southeast. The main fold structure is the Lågøyfjorden anticline which runs southwest–northeast. To the northwest of the fold hinge the dip is towards the north or northwest. The southeastern margin of the basin is formed by the low-angle Solund Fault or Solund Detachment, part of the Nordfjord-Sogn Detachment. Close to this margin small down-to-the-northwest listric normal faults are developed within the conglomerates, which merge with the detachment itself. At the fault contact, the lowermost metre of the conglomerates is strongly sheared, with a foliation parallel to the fault and the clasts become elongated in a direction parallel to the lineation in the underlying mylonite. The conglomerate is also noticeably deformed with well-developed cleavage in zone about 2.5 km wide parallel to the Solund Fault.[2] The conglomerates show evidence of very low-grade metamorphism with recognition of an assemblage of authigenic minerals that indicate temperatures in the range 230–330°C, consistent with maximum burial of up to 13 km.[3] The mylonites immediately beneath the Solund Fault appear to be a highly deformed version of the mafic rocks of the upper allochthon. These mylonites contain a suite of minor structures that show slightly oblique top-down-to-the-northwest movement.
Бассейн обрезается заметной серией почти на север -юг, которые интерпретируются как последнее палеозое до мезозойского возраста, связанного с расширением западного востока в районе Северного моря, которое началось во пермо -триаса время . [ 1 ]
Смотрите также
[ редактировать ]Ссылки
[ редактировать ]- ^ Jump up to: а беременный Fossen, H.; Хани, HF; Faleide, Ji; Ksienzyk, A.; Dunlap, WJ (2016). «Пост-калесонианское расширение в Западной Норвегии-Северное регион Северного моря: роль структурного наследования» (PDF) . В Childs, C.; Холдсворт, Re; Джексон, CA-L.; Manzocchi, T.; Уолш, JJ; Уход, Г. (ред.). Геометрия и рост нормальных разломов . Геологическое общество, Специальные публикации. Тол. 439. С. 465–486. doi : 10.1144/sp439.6 . S2CID 132839546 .
- ^ Jump up to: а беременный в Нильсен Т. Т. (1968). «Отношение седиментации к тектонике в районе Солунд Девоньян на юго -западе Норвегии». Norsk Geologisk Undersøkelse . 259 : 1–108.
- ^ Jump up to: а беременный Beinlich, A.; Austrheim, H.; Глодни, Дж.; Erambert, M.; Андерсен, Т.Б. (2010). «Секвестрация CO2 и экстремальное истощение Mg в серпентизированных перидотитных обломках из Девонского бассейна Solund, SW-Norway». Geochimica et Cosmochimica Acta . 74 (24): 6935–6964. doi : 10.1016/j.gca.2010.07.027 .
- ^ Jump up to: а беременный Харц, эх; Мартин, MW; Andresen, A.; Андерсен, Т.Б. (2002). «Вулканические породы в Девонском бассейне Солунд, Западная Норвегия: большие оползни силурийских (439 млн. Лету) риолитов» . Журнал геологического общества . 159 : 121–128. doi : 10.1144/0016-764901-063 . S2CID 55652501 .