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Papers by Christian Schiffer

The crustal seismic velocity model (based on receiver functions) of Ellesmere Island and the stru... more The crustal seismic velocity model (based on receiver functions) of Ellesmere Island and the structural geological cross-section of Ellesmere Island, both documented and discussed elsewhereinthisvolume, arehereintegratedinto acrustal-scaletransect crossingall themaintec-tonic domains. Thevelocity model satisf es much of theobserved gravity f eld, but implies minor modif cations with potentially important implications for characterizing the lower crust over the transect. The crust of the Pearya Terrane includes a high-velocity and high-density lower crustal body, suggested to represent a maf c underplate linked to the emplacement of the High Arctic Large Igneous Province. A similar body also lies directly beneath the Hazen Plateau, but this is more likely to be inherited from earlier tectonic stages than to be linked to the High Arctic LargeIgneousProvince. A large-scalebasement-involvingthrust, possiblylinkedtoadeepdetach-ment of Ellesmerian age, lies immediately south of the Pearya Terrane and forms the northern backdroptoacrustal-scalepop-upstructurethataccommodatesEurekan-agedshorteninginnorth-ernEllesmereIsland. ThethickestcrustanddeepestMohoalongthetransectarebelow theCentral Ellesmerianfoldbelt, wheretheMohoisf exureddownwardstothenorthtoadepthof about48 km beneath the load of the structurally thickened supracrustal strata of the fold belt.

Newdeepseismological datafromEllesmereIslandandtheadjacentArcticcontinental margin provide new in... more Newdeepseismological datafromEllesmereIslandandtheadjacentArcticcontinental margin provide new information about the crustal structure of the region. These data were not availablefor previousregional crustal models. Thispaper

Weusenewmodelsof crustal structureandthedepthof thelithosphere– asthenosphere boundary tocalculat... more Weusenewmodelsof crustal structureandthedepthof thelithosphere– asthenosphere boundary tocalculatethegeopotential energy anditscorrespondinggeopotential stressf eldfor the High Arctic. Palaeostress indicators such as dykes and rifts of known ageareused to comparethe presentdayandpalaeostressf elds. Whenbothstressf eldscoincide, aminimumagefor theconf g-uration of the lithospheric stress f eld may be def ned. We identify three regions in which this is observed. InnorthGreenlandandtheeasternAmerasiaBasin, thestressf eldisprobably thesame as that present during the Late Cretaceous. In western Siberia, the stress f eld is similar to that in theTriassic. Thestress directions on theeastern Russian Arctic Shelf and theAmerasiaBasin are similartothatintheCretaceous.Thepersistentmisf tof thepresentstressf eldandEarlyCretaceous dykeswarmsassociatedwith theHigh Arctic LargeIgneousProvinceindicates ashort-livedtran-sient change in the stress f eld at the time of dyke emplacement. Most Early Cretaceous rifts in theAmerasiaBasincoincidewiththestressf eld, suggestingthatdykingandriftingwereunrelated. Wepresentnewevidencefordykesandagrabenstructureof EarlyCretaceousageonBennettIsland.

Teleseismic receiver function analysis imaged a complex upper mantle structure in the Central Fjo... more Teleseismic receiver function analysis imaged a complex upper mantle structure in the Central Fjord Region of East Greenland, including an east-dipping high velocity layer and a mantle wedge of high crustal or low mantle velocities. This was interpreted as a fossil Caledonian subduction complex, including a slab of eclogitised mafic crust and an overlying wedge of serpentinised mantle. In this paper, we use a multidisciplinary geophysical and petrological modelling approach to test this proposed fossil subduction model. The consistency of the obtained velocity model with the regional gravity field is tested by forward density modelling and isostatic calculations. The models show that the sub-crustal structure, given by the more buoyant mantle wedge and the dipping high velocity/density layer, yield in a markedly better fit as compared to a homogeneous mantle lithosphere. Petrological-geophysical modelling is performed by testing different upper mantle compositions with regard to topography, gravity and seismic velocities using Litmod2D. This suggests that the observed lower crustal/ uppermost mantle bodies could be a combination of mafic intrusions, serpentinised peridotite and metamor-phosed mafic crust. The preferred composition for the dipping structure is eclogitised mafic crust, and hydrated peridotite filling the overlying mantle wedge. Models lacking an eclogite layer or a hydrated upper mantle composition show an inferior fit and, therefore, are not favoured representatives. This supports the interpretation as a fossil subduction zone complex. The spatial relations with Caledonian structures suggest an early Caledonian origin.

Rifts and passive margins often develop along old suture zones where colliding continents merged ... more Rifts and passive margins often develop along old suture zones where colliding continents merged during earlier phases of the Wilson cycle. For example, the North Atlantic formed after continental break-up along sutures formed during the Caledonian and Variscan orogenies. Even though such tectonic inheritance is generally appreciated, causative physical mechanisms that affect the localization and evolution of rifts and passive margins are not well understood. We use thermo-mechanical modeling to assess the role of orogenic structures during rifting and continental breakup. Such inherited structures include: 1) Thickened crust, 2) eclogitized oceanic crust emplaced in the mantle lithosphere, and 3) mantle wedge of hydrated peridotite (serpentinite). Our models indicate that the presence of inherited structures not only defines the location of rifting upon extension, but also imposes a control on their structural and magmatic evolution. For example, rifts developing in thin initial crust can preserve large amounts of orogenic serpentinite. This facilitates rapid continental breakup, exhumation of hydrated mantle prior to the onset of magmatism. On the contrary, rifts in thicker crust develop more focused thinning in the mantle lithosphere rather than in the crust, and continental breakup is therefore preceded by magmatism. This implies that whether passive margins become magma-poor or magma-rich, respectively, is a function of pre-rift orogenic properties. The models show that structures of orogenic eclogite and hydrated mantle are partially preserved during rifting and are emplaced either at the base of the thinned crust or within the lithospheric mantle as dipping structures. The former provides an alternative interpretation of numerous observations of 'lower crustal bodies' which are often regarded as igneous bodies. The latter is consistent with dipping sub-Moho reflectors often observed in passive margins.

With convergent plate boundaries at some distance, the sources of the lithospheric stress field o... more With convergent plate boundaries at some distance, the sources of the lithospheric stress field of the North Atlantic Realm are mainly mantle tractions at the base of the lithosphere, lithospheric density structure and topography. Given this, we estimate horizontal deviatoric stresses using a well-established thin sheet model in a global finite element representation. We adjust the lithospheric thickness and the sub-lithospheric pressure iteratively, comparing modelled in plane stress with the observations of the World Stress Map. We find that an anomalous mantle pressure associated with the Iceland and Azores melt anomalies, as well as topography are able to explain the general pattern of the principle horizontal stress directions. The Iceland melt anomaly overprints the classic ridge push perpendicular to the Mid Atlantic ridge and affects the conjugate passive margins in East Greenland more than in western Scandinavia. The dynamic support of topography shows a distinct maximum of c. 1000 m in Iceland and amounts <150 m along the coast of southwestern Norway and 250–350 m along the coast of East Greenland. Considering that large areas of the North Atlantic Realm have been estimated to be sub-aerial during the time of break-up, two components of dynamic topography seem to have affected the area: a short-lived, which affected a wider area along the rift system and quickly dissipated after break-up, and a more durable in the close vicinity of Iceland. This is consistent with the appearance of a buoyancy anomaly at the base of the North Atlantic lithosphere at or slightly before continental breakup, relatively fast dissipation of the fringes of this, and continued melt generation below Iceland.

Geophysical Journal International, 2016

Ellesmere Island in Arctic Canada displays a complex geological evolution. The region was affecte... more Ellesmere Island in Arctic Canada displays a complex geological evolution. The region was affected by two distinct orogenies, the Palaeozoic Ellesmerian orogeny (the Caledonian equivalent in Arctic Canada and Northern Greenland) and the Palaeogene Eurekan orogeny, related to the opening of Baffin Bay and the consequent convergence of the Greenland plate. The details of this complex evolution and the present-day deep structure are poorly constrained in this remote area and deep geophysical data are sparse. Receiver function analysis of seven temporary broad-band seismometers of the Ellesmere Island Lithosphere Experiment complemented by two permanent stations provides important data on the crustal velocity structure of Ellesmere Island. The crustal expression of the northernmost tectonic block of Ellesmere Island (∼82◦–83◦N), Pearya, which was accreted during the Ellesmerian orogeny, is similar to that at the southernmost part, which is part of the Precambrian Laurentian (North America- Greenland) craton. Both segments have thick crystalline crust (∼35–36 km) and comparable velocity–depth profiles. In contrast, crustal thickness in central Ellesmere Island decreases from ∼24–30 km in the Eurekan fold and thrust belt (∼79.7◦–80.6◦N) to ∼16–20 km in the Hazen Stable Block (HSB; ∼80.6◦–81.4◦N) and is covered by a thick succession of metasediments. A deep crustal root (∼48 km) at ∼79.6◦N is interpreted as cratonic crust flexed beneath the Eurekan fold and thrust belt. The Carboniferous to Palaeogene sedimentary succession of the Sverdrup Basin is inferred to be up to 1–4 km thick, comparable to geologically-based estimates, near the western margin of the HSB.

The large-scale geological evolution of the North Atlantic Realm during the past 450 Myr is large... more The large-scale geological evolution of the North Atlantic Realm during the past 450 Myr is largely understood, but crucial elements remain uncertain. These involve the Caledonian orogeny, the formation of the North Atlantic and accompanying igneous activity, and the present-day high topography surrounding the North Atlantic. Teleseismic receiver function interpretation in the Central Fjord Region of East Greenland recently suggested the presence of a fossil Caledonian subduction complex, including a slab of eclogitised mafic crust and an overlying wedge of serpentinised mantle peridotite. Here we further investigate this topic using inverse receiver functions modelling. The obtained velocity models are tested with regard to their consistency with the regional gravity field and topography. We find that the obtained receiver function model is generally consistent with gravity and isostasy. The western part of the section, with topography of >1000 m, is clearly supported by the 40-km-thick crust. The eastern part requires additional buoyancy as provided by the hydrated mantle wedge. The geometry, velocities and densities are consistent with interpretation of the lithospheric structure as a fossil subduction zone complex. The spatial relations with Caledonian structures suggest a Caledonian origin. The results indicate that topography is isostatically compensated by density variations within the lithosphere, and that significant dynamic topography is not required at the present-day.

Plate tectonic reconstructions are usually constrained by the correlation of lineaments of surfac... more Plate tectonic reconstructions are usually constrained by the correlation of lineaments of surface geology and crustal structures. This procedure is, however, largely dependent on and complicated by assumptions on crustal structure and thinning and the identification of the continent-ocean transition. We identify two geophysically and geometrically similar upper mantle structures in the North Atlantic and suggest that these represent remnants of the same Caledonian collision event. The identification of this structural lineament provides a sub-crustal piercing point and hence a novel opportunity to tie plate tectonic reconstructions. Further, this structure coincides with the location of some major tectonic events of the North Atlantic post-orogenic evolution such as the occurrence of the Iceland Melt Anomaly and the separation of the Jan Mayen microcontinent. We suggest that this inherited oro-genic structure played a major role in the control of North Atlantic tectonic processes.

Ellesmere Island in Arctic Canada displays a complex geological evolution. The region was affecte... more Ellesmere Island in Arctic Canada displays a complex geological evolution. The region was
affected by two distinct orogenies, the Palaeozoic Ellesmerian orogeny (the Caledonian equivalent
in Arctic Canada and Northern Greenland) and the Palaeogene Eurekan orogeny, related
to the opening of Baffin Bay and the consequent convergence of the Greenland plate. The
details of this complex evolution and the present-day deep structure are poorly constrained
in this remote area and deep geophysical data are sparse. Receiver function analysis of seven
temporary broad-band seismometers of the Ellesmere Island Lithosphere Experiment complemented
by two permanent stations provides important data on the crustal velocity structure
of Ellesmere Island. The crustal expression of the northernmost tectonic block of Ellesmere
Island (∼82◦–83◦N), Pearya, which was accreted during the Ellesmerian orogeny, is similar
to that at the southernmost part, which is part of the Precambrian Laurentian (North America-
Greenland) craton. Both segments have thick crystalline crust (∼35–36 km) and comparable
velocity–depth profiles. In contrast, crustal thickness in central Ellesmere Island decreases
from ∼24–30 km in the Eurekan fold and thrust belt (∼79.7◦–80.6◦N) to ∼16–20 km in the
Hazen Stable Block (HSB; ∼80.6◦–81.4◦N) and is covered by a thick succession of metasediments.
A deep crustal root (∼48 km) at ∼79.6◦N is interpreted as cratonic crust flexed beneath
the Eurekan fold and thrust belt. The Carboniferous to Palaeogene sedimentary succession of
the Sverdrup Basin is inferred to be up to 1–4 km thick, comparable to geologically-based
estimates, near the western margin of the HSB.

All requests for permission to reproduce this work, in whole or in part, for purposes of commerci... more All requests for permission to reproduce this work, in whole or in part, for purposes of commercial use, resale, or redistribution shall be addressed to: Earth Sciences Sector Copyright Information Officer, Room 622C,

Intraplate Earthquakes, 2014

Basin inversion is an intermediate-scale manifestation of continental intraplate deformation, whi... more Basin inversion is an intermediate-scale manifestation of continental intraplate deformation, which produces earthquake activity in the interior of continents. The sedimentary basins of central Europe, inverted in the Lale Cretaceous-Paleocene, represent a classic example of this phenomenon . It is known that inversion of these basins occurred in two phases: an initial one of transpressional shortening involving reverse activation of former normal faults and a subsequent one of uplift of the earlier developed inversion axis and a shift of sedimentary depocentres, and that this is a response to changes in the regional intraplate stress field. This European intraplate deformation is considered in the context of a new model of the present-day stress field of Europe (and the North Atlantic) caused by Iithospheric potential energy variations. Stresses causing basin inversion of Europe must have been favourably orientated with respect to pre-existing structures in the lithos ph ere. Furthermore, stresses derived from Iithospheric potential energy variations as well as those from plate boundary forces must be taken into account in order to explain intraplate seismicity and deformation such as basin inversion.

Passive margins are commonly separated into volcanic and non-volcanic modes, each with a distinct... more Passive margins are commonly separated into volcanic and non-volcanic modes, each with a distinct formation mechanism and structure. Both form the transition from continental to oceanic crust. Large amounts of geophysical data at passive margins show that the tapering continental crust is often underlain by high-velocity and density bodies (“Lower Crustal Bodies”, LCBs). A widely accepted theory of the origin of LCBs is that they were emplaced by magmatic underplating at volcanic margins. At the same time mantle serpentinization is thought to create geophysically similar structures at non-volcanic margins due to syn or post rift hydrothermal circulation. In this study an alternative model is presented that explains the oceanic rifting process from the onset to the formation of passive margins without the requirement of magmatic underplating or in situ mantle serpentinization. Instead rifting is focussed at relict subduction and suture zones, which may inherit rheological and composi...

Talks by Christian Schiffer

We have arranged a topical session for the 2017 GSA meeting in Seattle, 22-25 October. The online... more We have arranged a topical session for the 2017 GSA meeting in Seattle, 22-25 October. The online abstract submission system is open and will close 1 August. Please find the session and submit and abstract here: https://lnkd.in/dtC4RWV We are also organising a Special Issue in the Journal of Geodynamics for ALL interested colleagues on this topic. The session is co-sponsored by the International Lithosphere Program. The goals of this session are the discussion and revision of the structure and geological-geodynamic evolution of the North Atlantic–Arctic realm. Contributions from all relevant disciplines are requested, especially reports of multidisciplinary approaches.

Geophysical Journal International, 2016

Ellesmere Island in Arctic Canada displays a complex geological evolution. The region was affecte... more Ellesmere Island in Arctic Canada displays a complex geological evolution. The region was
affected by two distinct orogenies, the Palaeozoic Ellesmerian orogeny (the Caledonian equivalent
in Arctic Canada and Northern Greenland) and the Palaeogene Eurekan orogeny, related
to the opening of Baffin Bay and the consequent convergence of the Greenland plate. The
details of this complex evolution and the present-day deep structure are poorly constrained
in this remote area and deep geophysical data are sparse. Receiver function analysis of seven
temporary broad-band seismometers of the Ellesmere Island Lithosphere Experiment complemented
by two permanent stations provides important data on the crustal velocity structure
of Ellesmere Island. The crustal expression of the northernmost tectonic block of Ellesmere
Island (∼82◦–83◦N), Pearya, which was accreted during the Ellesmerian orogeny, is similar
to that at the southernmost part, which is part of the Precambrian Laurentian (North America-
Greenland) craton. Both segments have thick crystalline crust (∼35–36 km) and comparable
velocity–depth profiles. In contrast, crustal thickness in central Ellesmere Island decreases
from ∼24–30 km in the Eurekan fold and thrust belt (∼79.7◦–80.6◦N) to ∼16–20 km in the
Hazen Stable Block (HSB; ∼80.6◦–81.4◦N) and is covered by a thick succession of metasediments.
A deep crustal root (∼48 km) at ∼79.6◦N is interpreted as cratonic crust flexed beneath
the Eurekan fold and thrust belt. The Carboniferous to Palaeogene sedimentary succession of
the Sverdrup Basin is inferred to be up to 1–4 km thick, comparable to geologically-based
estimates, near the western margin of the HSB.

Intraplate Earthquakes, 2014