A crustal model for northern Melville Bay, Baffin Bay

Abstract

The interpretation of seismic refraction and gravity data acquired in 2010 gives new insights into the crustal structure of the West Greenland coast and the adjacent deep central Baffin Bay basin. Underneath Melville Bay, the depth of the Moho varies between 26 and 17 km. Stretched continental crust with a thickness of 25 to 14 km and deep sedimentary basins are present in this area. The deep Melville Bay Graben contains an up to~11 km thick infill of consolidated and unconsolidated sediments with velocities of 1.6 to 4.9 km/s. Seaward, at the~60 km wide transition between oceanic and stretched continental crust, a mount-shaped magmatic structure is observed, which most likely formed prior to the initial formation of oceanic crust. The up to 4 km high magmatic structure is underlain by a~2 km thick and~50 km wide high velocity lower crust. More to the west, in the oceanic part of the Baffin Bay basin, we identify a two-layered, 3.5 to 6 km thin igneous oceanic crust with increasing thickness toward the shelf. Beneath the oceanic crust, the depth of the Moho ranges between 11.5 and 13.5 km. In the western part of the profile, oceanic layer 3 is unusually thin (~1.5 km) A possible explanation for the thin crust is accretion due to slow spreading, although the basement is notably smooth compared to the basement of other regions formed by ultra-slow spreading. The oceanic crust is underlain by partly serpentinized upper mantle with velocities of 7.6 to 7.8 km/s.

Geophysical evidence for the extent of crustal types and the type of margin along a profile in the northeastern Baffin Bay

“…Underneath the thin crust, the upper mantle has velocities of >7.8 km/s, which is partly constrained by refractions (Figure ). Comparably low velocities of the upper have been described underneath the thin oceanic crust of the nearby profile AWI‐20100200 and interpreted as indication for serpentinized upper mantle [ Altenbernd et al ., ].…”

“…Modern wide‐angle seismic data sets have revealed that the southern Baffin Bay is underlain by 6 to 9 km thick oceanic crust [ Suckro et al ., ; Funck et al ., ]. In the northwestern Baffin Bay, the crust is composed of normal to abnormally thin oceanic crust (3.5–6 km) [ Altenbernd et al ., ]. Altenbernd et al .…”

“…Altenbernd et al . [] propose that slow spreading rates might be the reason for the accretion of unusually thin oceanic crust in the Baffin Bay.…”

“…Profile AWI‐20100200 extends across the main crustal highs and basins in northern Melville Bay, where stretched and 14 to 25 km thick, two‐layered continental crust is present [ Altenbernd et al ., ]. In this area, the Melville Bay Graben contains up to 11 km thick sediments and sedimentary rocks with velocities of up to 4.9 km/s, while the infill in the smaller Kivioq Basin is only ~6 km thick [ Altenbernd et al ., ]. The continental crust underneath the southern Melville Bay Graben is composed of three crustal units with velocities of 5.2 to 6.9 km/s [AWI‐20100400, Suckro et al ., ].…”

“…Black lines mark the position of other modern wide‐angle seismic profiles in the Baffin Bay. 1: line 3 [ Funck et al ., ], 2: profile 91/3 [ Jackson and Reid , ], 3: profile 91/2 [ Reid and Jackson , ], 4: profile 91/1 [ Jackson and Reid , ], 5: profile 91/4 [ Reid and Jackson , ], 6: profile AWI‐20100300 (Altendbernd et al, submitted manuscript, 2015), 7: profile AWI‐20100200, [ Altenbernd et al ., ], 8: profile AWI‐20100450 (this study), 9: profile AWI‐20100400 [ Suckro et al ., ], 10: profile AWI‐20080500 [ Suckro et al ., ], and 11: profile AWI‐20080600 [ Funck et al ., ]. Red lines mark sonobouy recordings from Keen and Barrett [].…”