scholarly journals Cenozoic tectonic and thermal history of the Nenana basin, central interior Alaska: new constraints from seismic reflection data, fracture history, and apatite fission-track analyses

2017 ◽  
Vol 54 (7) ◽  
pp. 766-784 ◽  
Author(s):  
Nilesh Dixit ◽  
Catherine Hanks ◽  
Alec Rizzo ◽  
Paul McCarthy ◽  
Bernard Coakley
Keyword(s):  
Seismic Reflection ◽  
Fission Track ◽  
Strike Slip ◽  
Apatite Fission Track ◽  
Plate Convergence ◽  
South Central ◽  
Interior Alaska ◽  
Late Paleocene ◽  
Half Graben ◽  
Nenana Basin

The Nenana basin of interior Alaska forms a segment of the diffuse plate boundary between the Bering and North American plates and is located within a complex zone of crustal-scale strike-slip deformation that accommodates compressional stresses in response to oblique plate convergence to the south. The basin is currently the focus of new oil and gas exploration. Integration of seismic reflection and well data, fracture data, and apatite fission-track analyses with regional data improves our understanding of the tectonic development of this continental strike-slip basin. The Nenana basin formed during the Late Paleocene as a 13 km wide half-graben, affected by regional intraplate magmatism and localized crustal thinning across the Minto Fault in south-central Alaska. The basin was uplifted and exhumed along this faulted margin in the Early Eocene through to Late Oligocene in response to oblique subduction along the southern Alaska margin. This event resulted in the removal of up to 1.5 km of Late Paleocene strata from the basin. Renewed rifting and subsidence during the Early Miocene widened the basin to the west resulting in deposition of Miocene non-marine clastic rocks in reactivated and newly formed extensional half-grabens. In the Middle to Late Miocene, left lateral strike-slip faulting was superimposed on this half-graben system, with rapid subsidence beginning in the Pliocene and continuing to the present day. At present, the Nenana basin is in a zone of transtensional deformation that accommodates compressional stresses in response to oblique plate convergence and allows tectonic subsidence by oblique extension along major basin-bounding strike-slip faults.

K–Ar and Fission Track Geochronometry of an Eocene Thermal Event in the Kettle River (West Half) Map Area, Southern British Columbia

1975 ◽  
Vol 12 (5) ◽  
pp. 836-843 ◽  
Author(s):  
G. A. Medford
Keyword(s):  
British Columbia ◽  
Abrupt Change ◽  
Fission Track ◽  
Apatite Fission Track ◽  
Thermal Event ◽  
South Central ◽  
Early Tertiary ◽  
Okanagan Valley

The Okanagan and Similkameen plutonic complexes west of the Okanagan Valley of south-central British Columbia yield K–Ar dates that range from 185 to 133 m.y. East of the Okanagan Valley Shuswap gneisses into which the plutonics intrude, and which may be as old as pre-midCarboniferous in age yield K–Ar dates between 59.9 and 47.4 m.y. This abrupt change, which approximately coincides with the Okanagan Valley, is a consequence of an intense thermal event in the early Tertiary which has reset K–Ar dates in the gneisses at shallow depths. Comparison of K–Ar, sphene and apatite fission track dates demonstrates that the heating affected the plutons west of the Okanagan Valley and that cooling of the Shuswap gneisses occurred at a rate in excess of 25 °C. per million years. The scatter observed in the older K–Ar dates of the plutonic complexes could be caused by post-emplacement heating with variable partial argon loss rather than by separate magmatic events. Thus, only the oldesl K–Ar dates obtained from the plutons may be significant as minimum ages for emplacement.

The Miocene plutonic event of the Patagonian Batholith at 44° 30′ S: thermochronological and geobarometric evidence for melting of a rapidly exhumed lower crust

2000 ◽  
Vol 91 (1-2) ◽  
pp. 169-179 ◽  
Author(s):  
M. A. Parada ◽  
A. Lahsen ◽  
C. Palacios
Keyword(s):  
Late Miocene ◽  
Lower Crust ◽  
Fission Track ◽  
Strike Slip ◽  
Fault System ◽  
Apatite Fission Track ◽  
Axial Zone ◽  
Exhumation Rates ◽  
Fission Track Ages ◽  
Host Rocks

The Patagonian Batholith was formed by numerous plutonic events that took place between the Jurassic and the Miocene. North of 47° S, the youngest plutons occupy the axial zone adjacent to the Liquiñe-Ofqui Fault Zone, which is a major intra-arc strike-slip fault system active since the Miocene. The Queulat Complex, located at 44° 30′ S, includes two Miocene plutonic units: the Early Miocene Queulat diorite (QD) and the Late Miocene Puerto Cisnes granite (PCG). The QD includes hornblende + clinopyroxene diorites and tonalites, whereas the PCG includes slightly peraluminous garnet ± sillimanite granites and granodiorites.Eleven mineral Ar–Ar ages and three apatite fission track ages were obtained from the Queulat Complex and surrounding host rocks. Hornblende and biotite Ar–Ar ages of c. 16-18 Ma and 9-10 Ma, respectively, were obtained for the QD. The youngest ages of the QD are similar to the age of emplacement of the PCG as previously determined. Ar–Ar ages for muscovites and biotites of 6·6 ± 0·3 Ma and 5·6 ± 0·1 Ma, respectively, were obtained for the PCG. Biotites and muscovites from mylonites and pelitic hornfelses adjacent to the PCG yielded Ar—Ar ages between 5·1 Ma and 5·5 Ma. The apatite fission track ages of the QD and PCG overlap within the error margin (2•2 ± 1·1-3·3 ± 1·4 Ma).The Al-in-hornblende geobarometer yielded pressures for the QD emplacement equivalent to depths in the 19-24 km range, which is substantially higher than the 10 km depth estimated previously for the PCG emplacement. Exhumation rates (v) up to 2·0mm/yr were calculated for the time elapsed between the QD and PCG emplacements. A v value of 1·0mm/yr was calculated for the PCG subsequent to its emplacement. Using the silica—Ca-tschermak-anorthite geobarometer, we estimate the QD magma generation to be at c. 33 km, which is similar to the current crustal thickness. Melting of mafic and metapelitic lower crust was possible at > 30km depth during a period when v was between 1·0mm/yr and 2·0mm/yr.

The thermal history of the Nares Strait, Kane Basin, and Smith Sound region in Canada and Greenland: constraints from apatite fission-track and (U–Th–Sm)/He dating

2005 ◽  
Vol 42 (9) ◽  
pp. 1547-1569 ◽  
Author(s):  
Alexander M Grist ◽  
Marcos Zentilli
Keyword(s):  
Thermal History ◽  
Fission Track ◽  
Source Area ◽  
Strike Slip ◽  
Sediment Supply ◽  
Late Paleozoic ◽  
Apatite Fission Track ◽  
Nares Strait ◽  
Denudation Rates ◽  
History Of

Apatite fission-track and (U–Th–Sm)/He data for samples with Proterozoic–Neogene lithologic ages from eastern Ellesmere, Devon, and Baffin islands in the Canadian Arctic Archipelago and northwest Greenland provide insights into the complex thermal history of this region. Most data reflect exhumational cooling of the region as a sediment source area for the developing Sverdrup Basin to the west during late Paleozoic – Mesozoic time. Samples proximal to the basin margin record late Paleozoic cooling consistent with erosion of uplifted rift flanks and widespread clastic sedimentation during early rifting and thermal subsidence. Data from distal samples are consistent with early Mesozoic epeirogenic denudational cooling during periods of high sediment supply from well-developed river systems. Around northern Baffin Bay, the data record erosional cooling of uplifted rift flanks in response to Late Cretaceous rifting. Rapid denudation rates are indicated for southeastern Devon Island, compatible with thick Upper Cretaceous strata offshore in Lancaster Sound. Slower denudation rates are indicated for northwest Greenland. Along Nares Strait, data reflect mafic volcanism or erosional exhumation associated with strike-slip and (or) thrust displacements during the Paleogene Eurekan orogeny and offer limited support for the existence of a Wegener fault. Fission-track ages older than those obtained in central Ellesmere Island, however, suggest that active tectonics occurred earlier near the strait, and strike-slip tectonism and deformation were likely partitioned across a relatively wide belt. Apatites obtained from Archean gneisses and Franklinian dykes have up to 500 ppm Sm, and up to 15% of the radiogenic He is Sm derived.

Conjugate strike-slip faulting across a subduction front driven by incipient seamount subduction

Geology ◽  
2020 ◽  
Vol 48 (5) ◽  
pp. 493-498
Author(s):  
Sam R. Davidson ◽  
Philip M. Barnes ◽  
Jarg R. Pettinga ◽  
Andrew Nicol ◽  
Joshu J. Mountjoy ◽  
...  
Keyword(s):  
New Zealand ◽  
Seismic Reflection ◽  
Fluid Pressure ◽  
Strike Slip ◽  
Accretionary Wedge ◽  
Pore Fluid Pressure ◽  
Plate Convergence ◽  
Swath Bathymetry ◽  
Seamount Subduction ◽  
Overlying Strata

Abstract The initial stages of seamount subduction and associated deformation in an overriding accretionary wedge is rarely documented. Initial subduction of Bennett Knoll seamount and faulting of the overlying strata along the Hikurangi subduction margin, New Zealand, are here studied using multibeam swath bathymetry, subbottom profiles, and regional seismic reflection lines. Our results provide new insights into the earliest stages of seamount collision at sediment-rich margins. Differential shortening along the subduction front induced by seamount subduction is initially accommodated in the accretionary wedge by conjugate strike-slip faults that straddle the buried flanks of the seamount and offset the frontal thrusts by as much as 5 km. The geometries of the strike-slip faults are controlled by the seamount’s dimensions and aspect, the obliquity of plate convergence, pore-fluid pressure, and the thickness and rheology of the incoming sedimentary section. Strike-slip faults in such settings are ephemeral and overprinted by the formation of new structures as seamount subduction advances.

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