Løvehovden fault and Billefjorden rift basin segmentation and development, Spitsbergen, Norway

Abstract

The Carboniferous Billefjorden rift basin is a well-known example of a suite of Carboniferous basins on the Barents Shelf and NE Greenland. The basin has a clastic, carbonate and evaporite fill with complex and disputed stratigraphic relationships, especially regarding the Ebbadalen and Minkinfjellet formations. Geometrically, the basin is considered a simple half-graben. A N-Strending fault and monocline structure within the northern portion of the basin, the Løvehovden fault, has lithological and thickness differences across it within the Minkinfjellet and possibly Ebbadalen formations. The fault shows W-side-down movement, defining a sub-basin within the larger halfgraben. Significant along-strike changes occur. Down-throw to the west is at least 150 metres and possibly 400 metres, as shown by across-fault thickness differences of Ebbadalen and/or Minkinfjellet formations. To the east of the fault, the contact between the Ebbadalen and Minkinfjellet formations is a disconformity with significant local relief, and is interpreted to represent exposure from footwall uplift, and associated near-or at-surface solution, producing basal stratiform breccias. A similar contact is not exposed west of the fault. Monoclinal deformation and thickening of the younger Wordiekammen Formation above and across the monocline constrain a later movement component. Kinematic data and the structural style clearly indicate the Løvehovden fault is a normal fault with associated tri-shear zone development, consistent with the regional Carboniferous rift setting. Earlier interpretations describe the Løvehovden fault and monocline as Tertiary contractional features. In contrast, our work advocates that they are an important architectural basin element, defining a sub-basin within the Billeforden Trough during Minkinfjellet Formation deposition, with insignificant, if any, Tertiary reactivation. The Løvehovden fault is aligned with and represents the southern termination of the Lemströmfjellet fault to the north. Thus, the Billefjorden basin changes from a narrow graben to a broader half-graben to the south. These along-strike changes have important implications for the stratigraphic architecture of the basin, and for palaeogeographic reconstructions. These results and application of 3-D models for extension related tri-shear zones may help inform interpretation of other Carboniferous basins on the Barents Shelf.

From widespread Mississippian to localized Pennsylvanian extension in central Spitsbergen, Svalbard

“…12c and d), potentially reflecting upward propagation of the fault as a blind fault, as shown in Gawthorpe et al (1997, their Fig. 3a) and as inferred for the Løvehovden Fault farther south, in Billefjorden (Maher Jr. and Braathen, 2011), and thus indicating decreasing fault activity along WNW-ESE-striking faults during the deposition (of the upper part?) of the Sporehøgda Member (Mumien Formation, Billefjorden Group) in Odellfjellet.…”

“…The Overgangshytta fault may have propagated upwards from an existing, steep, inherited, Neoproterozoic, basement-seated fault during post-Caledonian Mississippian to earliest Pennsylvanian extension. Such a mechanism was recently proposed to explain the geometry of the N-S-striking Løvehovden Fault in Billefjorden (Maher Jr. and Braathen, 2011). Another possibility is that the Overgangshytta anticline formed as a faultbend anticline (Rotevatn and Jackson, 2014, their Fig.…”

The first magnetotelluric image of the lithospheric-scale geological architecture in central Svalbard, Arctic Norway

“…The lateral variation in thickness can be due to a regional syncline dip of the strata in central Spitsbergen as well as the presence of thick Devonian and Carboniferous basins beneath the Mesozoic platform units. This is most pronounced adjacent to the BFZ (Maher & Braathen 2011;.…”

Early Cenozoic Eurekan strain partitioning and decoupling in central Spitsbergen, Svalbard

“…This would explain the localization of contractional duplexes and décollements in areas such as Pyramiden, Sassenfjorden, Reindalspasset, and (potentially) Triungen during early Cenozoic deformation. These contractional duplexes partially decoupled deformation between Lower Devonian to lowermost Upper Devonian sedimentary rocks of the Andrée Land Group and Mimerdalen Subgroup and thick Pennsylvanian-Permian deposits of the Gipsdalen Group and locally shielded the latter from Eurekan deformation, while Pennsylvanian sedimentary rocks in basinal areas in the hanging wall of the Odellfjellet Fault were involved in Eurekan deformation, and Carboniferous normal faults were inverted, e.g., in Odellfjellet (Koehl and Muñoz-Barrera, 2018), Løvehovden-Hultberget (Dallmann, 1993;Maher and Braathen, 2011), Adolfbukta (Harland et al, 1988), Lykteneset (Koehl et al, 2020), Anservika (Ringset and Andresen, 1988), and Sassenfjorden (Fig. 5a-f).…”