Provenance of intra-Rodinian basin-fills: The lower Dalradian Supergroup, Scotland

• Published in: Precambrian research 2007-02, Vol.153 (1), p.46-64
• Main Authors: Banks, C.J., Smith, M., Winchester, J.A., Horstwood, M.S.A., Noble, S.R., Ottley, C.J.
• Format: Article
• Language: English
• Subjects: Dalradian Supergroup; Grampian Group; Laser ablation; Laurentia; Rodinia
• ISSN: 0301-9268; 1872-7433
• DOI: 10.1016/j.precamres.2006.11.004

Scotland occupied a unique position within the Neoproterozoic supercontinent Rodinia, lying close to the junction of Laurentian, Amazonian and Baltican continental blocks. During the attempted break-up of the supercontinent, a series of intracratonic rift basins were created along the Scottish sector of the future Laurentian margin. These basins were filled with the thick, siliciclasitc Torridonian, Moine and Dalradian Supergroups. Combined U–Pb detrital zircon geochronology and Nd-isotope analyses of whole rocks are used to compare the provenance of two contemporaneous lower Dalradian rift basin-fills. The main control on their provenance signature is sedimentary transport direction, which allows the relative palaeogeographical positions of surrounding basement terranes to be assessed. Westerly derived sedimentary systems supplied voluminous ca. 1.8 Ga aged detritus to the western Corrieyairack Basin. By contrast, sediment supplied from the east within the eastern Strathtummel Basin was dominated by ca. 0.9–1.0 Ga sources. Distal and further travelled basin-axial depositional systems supplied the basins with a greater variety of detritus, dominated by early Mesoproterozoic (1.4–1.6 Ga) and late Palaeoproterozoic (1.6–1.8 Ga) ages. The dataset is consistent with the lower Dalradian Supergroup being sourced from the eastern Laurentian (Labrador region) and/or possibly western Baltica blocks. These data indicate that the basins were flanked to the west by ca. 1.8 Ga Makkovikian-Ketilidian (Rhinnian) igneous basement and to the east by 1.0 Ga Grenvillian-Sveconorwegian basement. This interpretation, combined with the similarities with other penecontemporaneous Laurentian rift-basin fills, indicates that the Dalradian Supergroup is not allochthonous or exotic to the Laurentian continental block.