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| 2. |
- Jakobsson, Martin, et al.
(författare)
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Evidence for an ice shelf covering the central Arctic Ocean during the penultimate glaciation
- 2016
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 7
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Tidskriftsartikel (refereegranskat)abstract
- The hypothesis of a km-thick ice shelf covering the entire Arctic Ocean during peak glacial conditions was proposed nearly half a century ago. Floating ice shelves preserve few direct traces after their disappearance, making reconstructions difficult. Seafloor imprints of ice shelves should, however, exist where ice grounded along their flow paths. Here we present new evidence of ice-shelf groundings on bathymetric highs in the central Arctic Ocean, resurrecting the concept of an ice shelf extending over the entire central Arctic Ocean during at least one previous ice age. New and previously mapped glacial landforms together reveal flow of a spatially coherent, in some regions41-km thick, central Arctic Ocean ice shelf dated to marine isotope stage 6 (similar to 140 ka). Bathymetric highs were likely critical in the ice-shelf development by acting as pinning points where stabilizing ice rises formed, thereby providing sufficient back stress to allow ice shelf thickening.
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| 3. |
- Jerram, D.A., et al.
(författare)
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Introduction: from the British Tertiary into the future – modern perspectives on the British Palaeogene and North Atlantic Igneous provinces
- 2009
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Ingår i: Geological Magazine. - 0016-7568 .- 1469-5081. ; 146:3, s. 305-308
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Tidskriftsartikel (refereegranskat)abstract
- The study of volcanic rocks and igneous centres has long been a classic part of geological research. Despite the lack of active volcanism, the British Isles have been a key centre for the study of igneous rocks ever since ancient lava flows and excavated igneous centres were recognized there in the 18th century (Hutton, 1788). This led to some of the earliest detailed studies of petrology. The starting point for many of these studies was the British Palaeogene Igneous Province (BPIP; formerly known as the ‘British Tertiary’ (Judd, 1889), and still recognized by this name by many geologists around the globe). This collection of lavas, volcanic centres and sill/dyke swarms covers much of the west of Scotland and the Antrim plateau of Northern Ireland, and together with similar rocks in the Faroe Islands, Iceland and Greenland forms a world-class Large Igneous Province. This North Atlantic Igneous Province (NAIP) began to form through continental rifting above a mantle plume at c. 60 Ma, and subsequently evolved as North America separated from Europe, creating the North Atlantic Ocean.
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| 4. |
- Mattsson, Tobias, 1990-, et al.
(författare)
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Quantifying the crystal cargo of the Cerro Bayo cryptodome, Argentina; A window into pre-emplacement magma processes and storage conditions
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Shallow plumbing systems with intermediate to evolved volcanic systems can show complex magma recycling and recharge systematics. Such evidence is often stored in the information looked within the crystal cargo found in shallow systems. The Cerro Bayo cryptodome provides a classic example of such processes and was emplaced in the upper kilometre of the Miocene, back-arc Chachahuén volcano. Cerro Bayo formed during an extensive dome-building (and collapse) stage of the Chachahuén volcano, and is composed of a porphyritic trachyandesite which contains numerous mafic enclaves. This contribution investigates the deeper magma plumbing system and magmatic processes preceding the emplacement of Cerro Bayo with petrography, mineral chemistry, crystal size distributions and thermobarometry. The main crystals found in Cerro Bayo are plagioclase and amphiboles, found as mixed phenocryst/antecryst and glomerocryts, constituting about 30 vol. % of the rock. Minor mineral phases include pyroxene, apatite and magnetite. Several crystal populations are identified within the Cerro Bayo, which indicate differences within the growth histories of the populations. Some plagioclase crystal display resorbed textures and show zones with sharp increases in An mol% (up to 25 %), indicative of recharge events with hot (more mafic) magma. Whereas other crystals record only small temperature shifts, likely induced by latent heat of crystallisation. Amphibole and clinopyroxene barometers yield average crystallisation pressure estimates that range from 740 to 1036 MPa, however, they overlap within error of the barometers, revealing a storage region prior to shallow emplacement at about 30 to 40 km depth in the lower crust. The voluminous crystal cargo, diverse zoning patterns, sieve-textured plagioclase and the abundant enclaves in Cerro Bayo suggest that the magma was derived from a crystal mush storage region that was mobilised and partly mixed by the recharge of mafic melt.
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| 5. |
- Stranne, Christian, et al.
(författare)
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Acoustic mapping of mixed layer depth
- 2018
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Ingår i: Ocean Science. - : Copernicus GmbH. - 1812-0784 .- 1812-0792. ; 14:3, s. 503-514
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Tidskriftsartikel (refereegranskat)abstract
- The ocean surface mixed layer is a nearly universal feature of the world oceans. Variations in the depth of the mixed layer (MLD) influences the exchange of heat, fresh water (through evaporation), and gases between the atmosphere and the ocean and constitutes one of the major factors controlling ocean primary production as it affects the vertical distribution of biological and chemical components in near-surface waters. Direct observations of the MLD are traditionally made by means of conductivity, temperature, and depth (CTD) casts. However, CTD instrument deployment limits the observation of temporal and spatial variability in the MLD. Here, we present an alternative method in which acoustic mapping of the MLD is done remotely by means of commercially available ship-mounted echo sounders. The method is shown to be highly accurate when the MLD is well defined and biological scattering does not dominate the acoustic returns. These prerequisites are often met in the open ocean and it is shown that the method is successful in 95% of data collected in the central Arctic Ocean. The primary advantages of acoustically mapping the MLD over CTD measurements are (1) considerably higher temporal and horizontal resolutions and (2) potentially larger spatial coverage.
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