Middle jurassic-lower cretaceous transgressive-regressive sequences and facies distribution off northern nordland and troms, Norway

• Published in: Norwegian Petroleum Society Special Publications Vol. 10; pp. 211 - 232
• Main Authors: Smelror, Morten, Mørk, Atle, Mørk, Mai Britt E., Weiss, Hermann M., Løseth, Helge
• Format: Book Chapter
• Language: English
• Published: Elsevier 2001
• Subjects: Earth Sciences; Geology, Exploration & Drilling; Oil & Gas Engineering; Paleontology & Stratigraphy
• ISBN: 9780444502414; 0444502416
• ISSN: 0928-8937
• DOI: 10.1016/S0928-8937(01)80015-1

Application of sequence stratigraphic principles, detailed facies analyses, mineralogy, organic geochemistry and high-resolution biostratigraphic correlations to continuously cored units from the Middle Jurassic-Lower Cretaceous succession of the Troms III and Nordland VII areas provide new information on the sedimentary history offshore northern Norway. Two new lithostratigraphical units, the Masnykan Formation and Rauate Member, are formally described. In the Troms III area, the lowermost sequence boundary of late Bajocian-early Bathonian age occurs in the upper part of the Stø Formation, while at Andøya and in the Nordland VII area it occurs on top of weathered basement. The Bathonian to Oxfordian succession is dominated by the transgressive systems tracts formed by the proximal sandstones of the Masnykan (new unit in the Nordland VII area) and Ramsa (Andøya) formations which distally grade into the Fuglen Formation in the offshore Troms area. The Hekkingen Formation occurs in all areas above the late Oxfordian sequence boundary. In the Nordland VII area, siltstones of the Rauate Member (new) represent the most proximal deposits of the Hekkingen Formation. Basinward the Rauate Member grades into the very organic-rich claystone of the Alge Member. We explain the deposition of the Alge Member by a modified "expanding puddle" model. Overlying the Alge Member a thick (Volgian-Berriasian), highstand systems tract forms the dark claystones and siltstones of the Krill Member in all areas. Sediments reflecting tectonic activity in the earliest Cretaceous are overlain by a regional early Valanginian sequence boundary that marks a clear shift in sedimentary regime. Slow sedimentation rate and high bioclastic input resulted in deposition of a condensed marly succession on shallow shelf areas (Klippfisk and Nybrua formations). The late Hauterivian-earliest Barremian sequence boundary is followed by renewed marine dark claystone deposits (Kolje Formation). The change in depositional regime across the condensed unit is associated with mineralogy changes of the claystones, which suggest increased influence from erosion of feldspar-rich rocks towards the end of this period.