Tectonic Framework and Geologic History (North Atlan:c and Iceland) Sarah Slotznick Enrichment Trip 2014 Ingibjörg Kaldal Iceland Geosurvey Present Day North Atlan:c 58II I
5 5a*L~~~~~~I
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-__
30.W
I____
I_____
I____I____
25 W I_
WIN
Fig. 2 (left). The location of Reykjanes Ridge, southwest of Iceland, and the area of Fig. 3. The 1000-fathom submarine contour
is shown, together with the 500-fathom contours for Rockall Bank.
Fig. 3 (right). Summary diagram of the magnetic
anomalies observed over Reykjanes Ridge (see Fig. 2). Straight lines indicate the axis of the ridge and the central positive
anomaly (17).
(21) in reconstructing the fit of the
continents around the Atlantic. In this
instance the deep to the southeast of
Rockall may represent an initial abortive split; the oceanic area to the
mentary cores.
northwest, centered on Reykjanes Ridge,
a subsequent and more persistent site
of spreading of the ocean floor. There
Reykjanes Ridge
is every indication from the existing
bathymetry (17) that the ridge crest
Observed anomaly profiles obtained is linear and not interrupted or offduring four crossings of the crest of set by transverse fractures.
Reykjanes
Ridge
are compared (Fig. 5)
This area therefore,
1200 kilometers
5a*L~~~~~~I
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I____
I_____
WIN
|
|
30.W
58II
I
with
simulations obtained
by assump- in width, may well record a comparaouthwest of Iceland,
area of
Fig.scales
3. Thefor1
1000-fathom
contour
the last submarine
tionand
of the
reversal
time
tively simple
and straightforward
exVine 966 Vogt 1986 s for Rockall Bank.
Fig. 3 (right). Summary diagram of the magnetic
only additional parameter being the
rate of spreading; the scale (Fig. 4)
has recently received striking independent confirmation from the work of
Opdyke et al. (20) on deep-sea sedi-
-__
I____I____
25 W I_
12
5
Ridge (half width, 600 km) is approximately 1 centimeter per annum
-that is, the rate of "drifting" is approximately 2 centimeters per annum.
Other Ridges
The model proposed by Vine and
Matthews (6) and developed by Vine
and Wilson (8) has been applied to
four widely separated areas on the
midoceanic ridge system (Figs. 6-9)
by assumption of the reversal time
scale shown in Fig. 4 and a rate
ed from www.sciencemag.org on January 8, 2012
|
1,
estimates with geodynamic models is problematic, since all geodynamic models are based on simplifying assumptions. Recently, seismic
anisotropy has emerged as a further tool to estimate NR for recent
times (Becker 2008; Kreemer 2009; Conrad and Behn, submitted
past plate boundary configuration has to be restored by making
assumptions based on limited geological constraints (like the age of
preserved ophiolites or slab-window related volcanism) and the rules
of plate tectonics. World uncertainty — the fraction of the Earth's
Plate Reconstruc:ons Torsvik et al. 2010 NA-­‐ EU Spreading Rates Eysteinsson and Gunnarsson 1995 the crust along the Faroe–Iceland ridge is 25–30 km thick
(Smallwood, 1999), which indicates, that the mantle potential
temperature is elevated by 200–250° C above normal. Similar
crustal thickness (25–35 km) has been inferred for the Green-
Hot Spot! Given appropriate rheological assumptions, the flow structure of the mantle can be calculated based on density anomalies
derived from seismic tomography and surface plate velocities
Fig. 1. Bathymetry and ridges in the North Atlantic.
Mihalffy et al. 2008 Hot Spot Tracks S.M. Howell et al. / Earth and Planetary Science Letters 392 (2014) 143–153
ate reconstructions and paleo-basement depth (Müller et al., 2008) showing the tectonic evolution of the study area. Filled circles mark estimated cente
to Greenland by Lawver and Müller (1994) (red) and Mihalffy et al. (2008) (purple). Dashed circles show corresponding (like colors) areas of influence of
or perfectly circular plume pancakes when the Aegir Ridge became extinct ∼25 Ma, based on the distance to the rough–smooth boundary in seafloor fa
eykjanes Ridge at 25 Ma. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)
Howell et ahotspot
l. 2014 influence. (2) Variations in lithospheric thicknes
ing the conduit-like, “inverted troughs” which form ben
Hotspot Tracks (Method) 120
T. Thordarson, G. Larsen / Journal of Geodynamics 43 (2007) 118–152
Fig. 1. Iceland is an elevated plateau in the middle of the North Atlantic, situated at the junction between the Reykjanes and Kolbeinsey Ridge
segments. Also shown: the axis of the Mid-Atlantic Ridge (heavy solid line), the North Atlantic basalt plateau (black) and their submarine equivalents
(dark grey). The line with the dots shows the position of the Iceland mantle plume from 65 million years to the present day. Modified after Saunders
et al. (1997).
Thordarson and Larson 2007 ; >58;G 5<:6F< 5<8 ;4F3=56?8 :E 58;B8745678 B87567A45=:3> <4>
Geochemistry
Geophysics
Geosystems
3
G
V-­‐shaped Ridges Ito 2001 BENEDIKTSDÓTTIR ET AL.: TECTONICS OF THE RR PAST 15 MA
10.1029/2011GC
Figure 13. Satellite gravity and tectonic boundaries near Iceland [Sandwell and Smith, 2009]. Oblique M
projection. Pseudofaults and failed rifts predicted
by our magneticemodels
shown; solid lines connect the
Benediktsdo\r t al 2are
012 56
faults of southward
propagating rifts, dashed lines connect pseudofaults of northward propagators, and red
Plate Boundaries in Iceland: Volcanoes and Faults Iceland rifts and transforms
Einarsson 2008 Plate Boundaries in Iceland T. Thordarson, G. Larsen / Journal of Geodynamics 43 (2007) 118–152
121
Fig. 2. The principal elements of the geology in Iceland, outlining the distribution of the major geological subdivisions, including the main fault
structures and volcanic zones and belts. RR, Reykjanes Ridge; RVB, Reykjanes Volcanic Belt; SISZ, South Iceland Seismic Zone; WVZ, West
Volcanic Zone; MIB, Mid-Iceland Belt; EVZ, East Volcanic Zone; NVZ, North Volcanic Zone; TFZ, Tjörnes Fracture Zone; KR, Kolbeinsey Ridge;
ÖVB, Öræfi Volcanic Belt; SVB, Snæfellsnes Volcanic Belt. Modified from Thordarson and Höskuldsson (2002).
Thordarson and Larson 2007 Ac:ve Plate Boundary in Iceland Árnadóttir et al.
orizontal GPS station velocities with 95 per cent confidence
ellipses,erelative
to stable North America, determined from the ISNET me
Árnadó\r t al. 2009 e time interval 1993–2004 (black arrows) and CGPS stations in Iceland for the time interval 1999–2004 (red arrows). The predicted
Past Plate Boundaries in Iceland Ivarsson 1992 Fig. 2. Crustal accretion, relocation and propagation of the Icelandic rift zones in the last 12 Ma
Past Plate Boundaries in Iceland Older crust underlies Iceland
-28˚
-24˚
-20˚
-16˚
5
5
Kolbeinsey
Ridge
6
-600
68˚
-1
0
00
280 k
6
00
0
Skagi
?
13
Snaefellsnes
7
Vatnajokull
64˚
6
00
-10
-600
5
7 (26)
5 (10)
6 (20)
62˚
Reykjanes
Ridge
-32˚
-28˚
-24˚
64˚
20 (45)
-600
Öraefajökull
12.92
± 0.14 Ma
-180
Iceland-Faeroe
Ridge
21 (49)
22 (52)
0
13 (36)
-1
00
0
62˚
23 (54)
-20˚
-16˚
-12˚
-8˚
Figure 1. Map of the Iceland region showing bathymetric contours and tectonic features. Oceanic magnetic anomalies (Nunns 1983) are labelled with anomaly
Foulger 006 on the eastern flank of the Reykjanes ridge. Thick black lines: axes of
number. Approximate ages in Ma are shown in parentheses after the
anomaly 2
number
Downloaded from http://gji.oxfordjournals.org/ at California Institute o
?
-1000
00
66˚
-600
-600
-18
68˚
m
-1
66˚
-8˚
-1800
Greenland-Iceland
16 ± 0.3 Ma
Ridge
-12˚
-2600
-32˚
673
Geology of Iceland Sigmundsson 2006 Geologic History Sigmundsson 2006 1.  Ter:ary—Basal:c Lava Pile, 10m thick flows, regionally :lted 2.  Plio-­‐Pleistocene—Subaerial lavas plus hyaloclas:tes, fluvioglacial/morainic deposits 3.  Upper Pleistocene—More extensive hyaloclas:tes and pillow lavas, ligle erosion 4.  Postglacial—Fresh flows, pyroclas:cs and sediments 4. Horizontal GPS station velocities with 95 per cent confidence ellipses, relative to stable Eurasia, estimated from the ISNET observations
rval 1993–2004 (black arrows) and CGPS stations in Iceland for the time interval 1999–2004 (red arrows). The predicted velocity of North A
o stable Eurasia from the NUVEL-1A plate motion model (DeMets et al. 1994) is shown with green arrows.
Glacial Rebound Árnadó\r al. CGPS
2009 network
. Vertical velocities in the ITRF2005 from ISNET (1993–2004)
andet the
in Iceland (1999–2004). Positive numbers indicate upl
−1
are subsidence. Contour lines are drawn every 4 mm yr . The red dots show the GPS station locations.
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Works Cited Kaldal, I. From Þingvellir. hgp://www.geothermal.is/30-­‐open-­‐fissures-­‐diver:ng-­‐plate-­‐margin-­‐thingvellir Vine, F. J. (1966). Spreading of the ocean floor: new evidence. Science,154(3755), 1405-­‐1415. Vogt, P. R. (1986). The present plate boundary configura:on, in: P.R. Vogt and B. E. Tucholke (eds), The Geology of North America, Volume M: The Western North Atlan:c Region, Geological Society of America, Boulder, CO, 189-­‐204. Torsvik, T. H., Steinberger, B., Gurnis, M., & Gaina, C. (2010). Plate tectonics and net lithosphere rota:on over the past 150My. Earth and Planetary Science Le@ers, 291(1), 106-­‐112. Eysteinsson, H., & Gunnarsson, K. (1995). Maps of gravity, bathymetry and magne:cs for Iceland and surroundings. Orkustofnun. Mihalffy, P., Steinberger, B., & Schmeling, H. (2008). The effect of the large-­‐scale mantle flow field on the Iceland hotspot track. Tectonophysics, 447(1), 5-­‐18. Howell, S. M., Ito, G., Breivik, A. J., Rai, A., Mjelde, R., Hanan, B., ... & Vogt, P. (2014). The origin of the asymmetry in the Iceland hotspot along the Mid-­‐Atlan:c Ridge from con:nental breakup to present-­‐day. Earth and Planetary Science Le@ers, 392, 143-­‐153. Thordarson, T., & Larsen, G. (2007). Volcanism in Iceland in historical :me: Volcano types, erup:on styles and erup:ve history. Journal of Geodynamics,43(1), 118-­‐152. Ito, G. (2001). Reykjanes' V'-­‐shaped ridges origina:ng from a pulsing and dehydra:ng mantle plume. Nature, 411(6838), 681-­‐684. Benediktsdó\r, A., Hey, R., Mar:nez, F., & Höskuldsson, Á. (2012). Detailed tectonic evolu:on of the Reykjanes Ridge during the past 15 Ma.Geochemistry, Geophysics, Geosystems, 13(2). Einarsson, P. (2008). Plate boundaries, rips and transforms in Iceland. Jökull,58, 35-­‐58. Árnadó\r, T., Lund, B., Jiang, W., Geirsson, H., Björnsson, H., Einarsson, P., & Sigurdsson, T. (2009). Glacial rebound and plate spreading: results from the first countrywide GPS observa:ons in Iceland. Geophysical Journal Interna:onal, 177(2), 691-­‐716. Ivarsson, G. (1992). Geology and petrochemistry of the Torfajokull central volcano in central south Iceland, in associa:on with the Icelandic hot spot and riR zones (Doctoral disserta:on, University of Hawaii). Foulger, G. R. (2006). Older crust underlies Iceland. Geophysical Journal Interna:onal, 165(2), 672-­‐676. Sigmundsson, F. (2006). Iceland geodynamics: Crustal Deforma:on and Divergent Plate Tectonics. Praxis Publishing Limited, Chichester, UK.