Cenozoic vertical motions in the Moray Firth Basin associated with initiation of the Iceland Plume

Abstract

It is likely that the Iceland mantle plume generated transient uplift across the North Atlantic region when it initiated in earliest Cenozoic time. However, transient uplift recorded in sedimentary basins fringing the region can be overprinted by the effects of permanent uplift. Identifying and quantifying transient uplift can only be achieved in areas which have a well‐constrained stratigraphic record and across which the relative importance of permanent and transient uplift varies (e.g., the Moray Firth Basin, North Sea). By analyzing the subsidence of 50 boreholes from the Moray Firth Basin (MFB), residual vertical motions unrelated to rifting have been isolated. Transient uplift of 180–425 m occurred during Paleocene times. The western MFB has also been affected by permanent Cenozoic uplift, with denudation decreasing from 1.3 ± 0.1 km in the west of the basin to zero denudation east of 1°W. Dynamic support above the Iceland Plume led to transient uplift of the entire MFB in early Paleocene times, peaking in latest Paleocene times. In early Eocene times the effect of the plume waned, and subsidence occurred. Paleocene permanent uplift of the NW British Isles is generally accepted to have been due to magmatic underplating of the crust emplaced during the British Tertiary Igneous Province (61–58.5 Ma). The cause of Neogene uplift events is poorly understood, but it could also be associated with the Iceland Plume.

The North Atlantic Igneous Province: A review of models for its formation

“…Dataset: Brooks and Gleadow (1977), Gleadow and Brooks (1979), Bugge et al (1980), Dickin (1981), Dickin and Jones (1983), Mussett (1986), Thompson et al (1987), Gibson et al (1987), Noble et al (1988), Hitchen and Ritchie (1993), Nevle et al (1994), Upton et al (1995), Pearson et al (1996), Hirschmann et al (1997), Price et al (1997), , , Storey et al (1998), Tegner et al (1998), Gamble et al (1999), Tegner and Duncan (1999), Moorbath et al (1968), Ross and Mussett (1976), Hardarson et al (1997), andFoulger (2006). Ren et al (2003), Jones and White (2003), Mackay et al (2005) and Knox (1998). …”

“…Tectonic subsidence curves show uplift around the time of rift-drift transition on the western side of the Vøring Basin and the Vøring Marginal High (Skogseid et al, 1992). Around Ireland and in the North Sea, a maximum transient uplift occurs in Late Paleocene-Early Eocene time, followed by a rapid post-early Eocene subsidence (Nadin et al, 1997;Jones et al, 2001;Green et al, 2001;Mackay et al, 2005). In the Faeroe-Shetland Basin, the Late Paleocene-Early Eocene phase coincides with a strong unconformity and prograding sands and mudstone sequences offshore Faeroes (Sørensen et al, 2003).…”

“…Around the British Isles, apatite fission track studies have identified two exhumation events: an Early Cenozoic and a Late Cenozoic episode (Green et al, 2001). Subsidence analysis in the Moray Firth Basin (Mackay et al, 2005) suggests transient uplift initiated in Early Paleocene time. The basin records contemporaneous changes from hemipelagic to clastic sedimentation in the northern North Sea and coincides with a marine regression (Ahmadi et al, 2003).…”

Control of Aptian palaeobathymetry on turbidite distribution in the Buchan Graben, Outer Moray Firth, Central North Sea

“…-Rifting in the OMF was dominantly pre-Aptian in age and effects of rifting are thought to be instantaneous; no riftrelated footwall uplift or hangingwall subsidence along the main faults was, therefore, included in the modelling. -Published literature documents that the lithosphere in the OMF is relatively weak with an elastic thickness of <5 km (Barton and Wood, 1984;Barton, 1992;Nadin and Kusznir, 1996;Tiley et al, 2003;Mackay et al, 2005). Local, or 1D, isostatic compensation (Airy Isostasy) can be used when the elastic thickness is zero.…”

“…-When Flexural Isostasy is used the lithosphere is assumed to demonstrate perfect elastic behaviour. -Palaeowater-depths suggested by Mackay et al (2005;and references therein) are used. -The surfaces at the base and top of the Chalk Group are assumed to have been deposited horizontally.…”