--> ABSTRACT: Volcanic Rifted Margins and Unconventional Delta Systems; Constraining Supply, Sea Level and Slumping

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Volcanic Rifted Margins and Unconventional Delta Systems; Constraining Supply, Sea Level and Slumping

Wright, Kirstie 1; Davies, Richard 1; Jerram, Dougal 1; Morris, Jenny 2; Fletcher, Rosie 2
(1) Earth Science, Durham University, Durham, United Kingdom. (2) Statoil Uk, London, United Kingdom.

During the late Palaeocene, the rifting event that created the North Atlantic produced significant volumes of lava that erupted on or close to the Faroe Islands. Where lava flows entered the Faroe-Shetland Basin, a number of lava-fed delta systems formed and have been shown to record the early encroachment of the flood basalts into the basin and the position of the palaeo-shoreline[1]. Siliciclastic deposition can decrease or cease during volcanism and resume during periods of quiescence. Preservation of these ancient volcanic systems in offshore settings have the potential to record basin development when more conventional depositional systems were absent, including indicators for relative sea level, volcanic sediment supply and available accommodation space.

Mapping of overlapping 2D and 3D seismic surveys within the central Faroe-Shetland Basin has revealed a variety of seismic facies that document the transition of aerial lava flows to marine hyaloclastic breccias. The application of seismic stratigraphic principles delineated a series of discrete, seismically resolvable units with distinct bounding reflectors and internal architectures. The 3D data allowed for the spatial construct of the lava-fed delta front and its depositional processes to be assessed.

The seismic units are taken to represent periods of active volcanism and their stacking patterns has allowed the reconstruction of the gross depositional history. Delta deposition is primarily driven by lava supply, which overwhelmed the basin and caused the system to prograde out into the basin, with later periods of retrogradation as volcanism waned and died. Distinct 3D morphological features have also been identified, including cuspate collapse scarps, lava flow feeder systems and lobate, pahoehoe-like lava flows. These features are directly comparable to those of more recent lava-fed delta systems, including those on Iceland and Hawaii, suggesting that similar processes may have occurred. This breakthrough allows us to map the development of the delta systems from the lavas that fed them, and ultimately how a palaeo-shore line was affected by flood volcanism during the breakup of Europe from North America.

[1] Kiørboe, L. (1999) Stratigraphic relationships of the Lower Tertiary of the Faeroe Basalt Plateau and the Faeroe-Shetland Basin. In: Petroleum Geology of Northwest Europe: Proceedings of the 5th Conference (Ed. by A.J. Fleet & S.A.R. Boldy). Geological Society of London, 559-572.

 

AAPG Search and Discovery Article #90135©2011 AAPG International Conference and Exhibition, Milan, Italy, 23-26 October 2011.