TY - JOUR
T1 - Oblique rifting and the Late Eocene–Oligocene demise of Laurasia with inception of Molloy Ridge
T2 - Deformation of Forlandsundet Basin, Svalbard
AU - Kleinspehn, Karen L.
AU - Teyssier, Christian
N1 - Publisher Copyright:
© 2016 Elsevier B.V.
PY - 2016/12/14
Y1 - 2016/12/14
N2 - Final breakup of the Laurasian supercontinent occurred within a residual continental bridge that spanned Svalbard, Greenland and Arctic Canada from Late Cretaceous to Oligocene time, but the timing and precise kinematics of that breakup have remained obscure. Dextral oblique motion between Svalbard and northeastern Greenland initially generated the West Spitsbergen Fold-Thrust Belt (a transpressional orogen) but evolved into oblique rifting until the ultimate demise of the continental bridge with the Early Miocene formation of the Molloy Ridge. The Forlandsundet basin stands as a critical entity within the Svalbard continental margin whose fill captured the progressive transition between oblique convergence and divergence. The basin originated as a Late Eocene piggyback basin within the fold-thrust belt during deposition of the oldest unit, the marine fluvio-deltaic Sarsbukta conglomerate. Structural mapping highlights early deformation of the Sarsbukta strata expressed as (1) fractured cobbles in which fractures formed by consistent NNW–SSE stretching were injected with sandy matrix (when poorly lithified), (2) stylolites recording WSW–ENE shortening, and (3) conjugate dextral- and sinistral-normal mesoscale faults that indicate WSW–ENE shortening (P axes) and NNW–SSE extension (T axes). Between 38 and 31 Ma, this episode of orogen–normal shortening with orogen–parallel extension evolved progressively into oblique divergence (NW–SE extension) recorded in the Sarsbukta strata as basin-wide strike-slip/normal faults, transtensional folds, and sub-horizontal stylolite surfaces (subvertical P axes). Thus NW–SE extension, consistent with present spreading on the Molloy Ridge, was established at least 9 m.y. before the first emergence of recognized oceanic lithosphere. Deformation occurred at upper-crustal temperatures of ≤ 104 °C based on new vitrinite reflectance data. Transtension resulted in intrabasinal exposures of the Caledonide metamorphic basement during deposition of the second unit, the ≥ 31 Ma marine fan-deltaic Sarstangen conglomerate, in the Forlandsundet graben sensu stricto. Such oblique stretching severed the continental bridge heralding ultimate oceanic spreading at the Molloy Ridge.
AB - Final breakup of the Laurasian supercontinent occurred within a residual continental bridge that spanned Svalbard, Greenland and Arctic Canada from Late Cretaceous to Oligocene time, but the timing and precise kinematics of that breakup have remained obscure. Dextral oblique motion between Svalbard and northeastern Greenland initially generated the West Spitsbergen Fold-Thrust Belt (a transpressional orogen) but evolved into oblique rifting until the ultimate demise of the continental bridge with the Early Miocene formation of the Molloy Ridge. The Forlandsundet basin stands as a critical entity within the Svalbard continental margin whose fill captured the progressive transition between oblique convergence and divergence. The basin originated as a Late Eocene piggyback basin within the fold-thrust belt during deposition of the oldest unit, the marine fluvio-deltaic Sarsbukta conglomerate. Structural mapping highlights early deformation of the Sarsbukta strata expressed as (1) fractured cobbles in which fractures formed by consistent NNW–SSE stretching were injected with sandy matrix (when poorly lithified), (2) stylolites recording WSW–ENE shortening, and (3) conjugate dextral- and sinistral-normal mesoscale faults that indicate WSW–ENE shortening (P axes) and NNW–SSE extension (T axes). Between 38 and 31 Ma, this episode of orogen–normal shortening with orogen–parallel extension evolved progressively into oblique divergence (NW–SE extension) recorded in the Sarsbukta strata as basin-wide strike-slip/normal faults, transtensional folds, and sub-horizontal stylolite surfaces (subvertical P axes). Thus NW–SE extension, consistent with present spreading on the Molloy Ridge, was established at least 9 m.y. before the first emergence of recognized oceanic lithosphere. Deformation occurred at upper-crustal temperatures of ≤ 104 °C based on new vitrinite reflectance data. Transtension resulted in intrabasinal exposures of the Caledonide metamorphic basement during deposition of the second unit, the ≥ 31 Ma marine fan-deltaic Sarstangen conglomerate, in the Forlandsundet graben sensu stricto. Such oblique stretching severed the continental bridge heralding ultimate oceanic spreading at the Molloy Ridge.
KW - Hydraulically fractured cobbles
KW - Late Eocene–Oligocene Forlandsundet basin
KW - Molloy Ridge
KW - Oblique rifting
KW - Tertiary Laurasian continental bridge, Svalbard
KW - Transpression to transtension transition
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U2 - 10.1016/j.tecto.2016.05.010
DO - 10.1016/j.tecto.2016.05.010
M3 - Article
AN - SCOPUS:84970029109
SN - 0040-1951
VL - 693
SP - 363
EP - 377
JO - Tectonophysics
JF - Tectonophysics
ER -