The pre-breakup stratigraphy and petroleum system of the Southern Jan Mayen Ridge revealed by seafloor sampling

The authors would like to acknowledge the contribution from the vessel’s crew (captain I. Rasmussen) and operator (Thor Ltd), the two surveyors (K. Høysæth and H.B. Bortne), and two sampling assistants (F. Gausepohl and A.-M. Voelsch). Sverre Planke and Dougal Jerram are partly funded through a Norwegian Research Council Centers of Excellence project (project number 223272, CEED). Adriano Mazzini is funded by the European Research Council under the European Union's Seventh Framework Programme Grant agreement n° 308126 (LUSI LAB project, PI A. Mazzini). TGS and VBPR funded the cruise and allowed the publication of the data and interpretation. Steve Killops from APT refined our interpretation of the biomarker data. The reviewers and the editor are also thanked for their constructive comments. Finally, this article is dedicated to the biostratigrapher Haavard Selnes who sadly passed away in 2015.Peer reviewedPostprin

Igneous seismic geomorphology of buried lava fields and coastal escarpments on the Vøring volcanic rifted margin

Voluminous igneous complexes are commonly present in sedimentary basins on volcanic rifted margins, and they represent a challenge for petroleum explorationists. A 2500 km2 industry-standard 3D seismic cube has recently been acquired on the Vøring Marginal High offshore mid-Norway to image subbasalt sedimentary rocks. This cube also provides a unique opportunity for imaging top- and intrabasalt structures. Detailed seismic geomorphological interpretation of the top-basalt horizon, locally calibrated with high-resolution P-Cable wide-azimuth data, reveals new insight into the late-stage development of the volcanic flow fields and the kilometer-high coastal Vøring Escarpment. Subaerial lava flows with compressional ridges and inflated lava lobes cover the marginal high, with a comparable structure and size to modern subaerial lava fields. Pitted surfaces, likely formed by lava emplaced in a wet environment, are present in the western part of the study area near the continent-ocean boundary. The prominent Vøring Escarpment formed when eastward-flowing lava reached the coastline. The escarpment morphology is influenced by preexisting structural highs, and these highs are locally bypassed by the lava. Volcanogenic debris flows are well-imaged on the escarpment horizon, along with large-scale large slump blocks. Similar features exist in active volcanic environments, e.g., on the south coast of Hawaii. Numerous postvolcanic extensional faults and incised channels cut into the marginal high and the escarpment, and we found that the area was geologically active after the volcanism ceased. In summary, igneous seismic geomorphology and seismic volcanostratigraphy are two very powerful methods to understand the volcanic deposits and development of rifted margins. Our study demonstrates great promise for further understanding the igneous development of offshore basins as more high-quality 3D seismic data become available

Regional structure and polyphased Cretaceous-Paleocene rift and basin development of the mid-Norwegian volcanic passive margin

The Møre and Vøring basins of the mid-Norwegian volcanic passive margin are characterized by thick accumulations of Cretaceous to Paleocene sedimentary strata. They were formed during a series of Late Mesozoic-Early Cenozoic extensional events and represent vast underexplored areas with a limited number of wells. Recently, a new generation of long-offset 2D seismic reflection lines and 3D seismic data, together with new well data, has permitted a significant improvement in the regional understanding of the Møre and Vøring basins. This has enabled much better imaging of the deep Cretaceous subbasins and sub-basalt structures. In light of this significant data improvement, we performed a regional tectonostratigraphic synthesis of the pre-breakup development of the Møre and Vøring basins. We have interpreted eight regional Cretaceous and Paleocene horizons and constructed a series of structural and thickness maps. The new interpretations allow us to examine the sequential evolution of the Cretaceous to Paleocene sedimentary infill and to discuss its relationship to the deep crustal structures and regional tectonic events. We conclude that the long and polyphased development of the Møre and Vøring basins is partly controlled by deep-seated structural highs. We show that active deposition in the Early Cretaceous was mainly focused in the Møre Basin, while the main Cenomanian and subsequent Late Cretaceous-Paleocene depocentres developed principally in the Vøring Basin and migrated sequentially west towards the present continent-ocean boundary. We argue that the outer Møre and Vøring basins are likely underlain by a relatively thick continental crust compared to the inner part of the regional sag basin. In this setting our observations do not support evidence for a large zone of exhumed upper mantle, which has previously been proposed to have formed before magmatism and breakup

The ocean-continent transition in the mid-Norwegian margin: Insight from seismic data and an onshore Caledonian field analogue

Understanding the structure of the ocean-continent transition (OCT) in passive margins is greatly enhanced by comparison with onshore analogues. The North Atlantic margins and the "fossil" system in the Scandinavian Caledonides show variations along strike between magma-rich and magma-poor margins, but are different in terms of exposure and degree of maturity. They both display the early stages of the Wilson cycle. Seismic reflection data from the mid-Norwegian margin combined with results from Ocean Drilling Program Leg 104 drill core 642E allow for improved subbasalt imaging of the OCT. Below the SeawardDipping Reflector (SDR) sequences, vertical and inclined reflections are interpreted as dike feeder systems. High-amplitude reflections with abrupt termination and saucer-shaped geometries are interpreted as sill intrusions, implying the presence of sediments in the transition zone beneath the volcanic sequences. The transitional crust located below the SDR of the mid-Norwegian margin has a well-exposed analogue in the Seve Nappe Complex (SNC). At Sarek (Sweden), hornfelsed sediments are truncated by mafic dike swarms with densities of 70%-80% or more. The magmatic domain extends for at least 800 km along the Caledonides, and probably reached the size of a large igneous province. It developed at ca. 600 Ma on the margin of the lapetus Ocean, and was probably linked to the magma-poor hyperextended segment in the southern Scandinavian Caledonides. These parts of the SNC represent an onshore analogue to the deeper level of the mid-Norwegian margin, permitting direct observation and sampling and providing an improved understanding, particularly of the deeper levels, of present-day magma-rich margins

Seismic volcano-stratigraphy of the Northeast Greenland continental margin

The Early Eocene continental break-up between the NE Greenland and the mid- Norwegian–SW Barents Sea margins was associated with voluminous magmatism and led to the emplacement of massive volcanic complexes including wedges of seawards-dipping reflections (SDR). We study the distribution of these break-up-related volcanic rocks along the NE Greenland margin by revisiting existing seismic reflection data and comparing our observations to betterstudied segments of the conjugate margin. Seismic facies types match between the conjugate margins and show strong lateral variations. Seaward-dipping wedges are mapped offshore East Greenland, the conjugate to the Vøring continental margin. The geophysical signature of the SDRs becomes less visible towards the north, as it does along the conjugate Lofoten–Vestera°len margin. We suggest that the Traill Ø volcanic ridge is a result of plume–ridge interactions formed between approximately 54 and 47 Ma. North of the East Greenland Ridge, strong basement reflections conjugate to the Vestbakken Volcanic Province are interpreted as lava flows or ‘spurious’ SDRs. We discuss our findings in conjunction with results from seismic wide-angle experiments, gravity and magnetic data. We focus on the spatial and temporal relationships of the break-up volcanic rocks, and their structural setting in a late rift and initial oceanic drift stage

Rapid loading and deformation of soft sediments during emplacement of a Lava Delta in the Vøring Basin, Mid-Norwegian Margin

Egg-box dimension measurements

Seismic volcanostratigraphy of the NE Greenland continental margin

The figures show the original seismic data used as the base for the interpretations shown in this paper. The seismic profiles are marked on Figure 1 (in the paper) as numbers 1 to 10