Frank Lisker

Eocene initiation of Ross Sea dextral faulting and implications for East Antarctic neotectonics

The Ross Sea region of the East Antarctic plate provides evidence for intraplate tectonic activity in Cenozoic times. Still unresolved are the cause, timing and kinematics of this intraplate tectonism. By integrating and discussing the different (kinematic and temporal) signals of Cenozoic tectonism, intraplate dextral shearing is recognized as the main tectonic regime controlling the structural architecture of the Ross Sea region from the Mid-Eocene (c. 40–50 Ma) onward. We speculate that propagation and persistence of this tectonic regime through time constitutes a feasible seismogenetic framework to explain past and current tectonism in the Ross Sea region.

Review of fission track studies in northern Victoria Land, Antarctica—passive margin evolution versus uplift of the Transantarctic Mountains

Abstract Apatite fission track ages in the Pacific sector of Antarctica range from 470 Ma in Terre Adelie to 15 Ma in the Transantarctic Mountains of northern Victoria Land. Ages west of the Rennick Graben (Outback Shoulder) predominantly vary between ∼300 and ∼100 Ma, whereas those east of the graben (Admiralty Block) are typically younger than 100 Ma. The age pattern and the regional distribution of the track lengths indicate a markedly different cooling history for the tectonic blocks of northern Victoria Land, but similar to that of the pre-Gondwana breakup conjugate margin of southeastern Australia. At least 2 km of regional erosion is recorded for the Outback Shoulder during the Devonian/Carboniferous, which is probably related to late Paleozoic terrane accretion. Jurassic to Early Cretaceous rifting and extension of the Wilkes Basin led to crustal thinning of the Outback Shoulder, followed by limited regional denudation of 2–3 km during late Mesozoic times. In contrast, the cooling history of the Admiralty Block is characterised by coastal denudation exceeding 3–4 km due to the formation of the Pacific continental margin since the Early Cretaceous, and episodic uplift of the Transantarctic Mountains since the Late Cretaceous and Cenozoic.

The Evolution of the Geothermal Gradient from Lambert Graben and Mahanadi Basin – A Contribution to the Indo-Antarctic Rift Debate

Abstract The East Antarctic Lambert Graben and the Indian Mahanadi Basin are considered to represent segments of an intra-Gondwanan rift structure that was active at least since the Paleozoic. Fission track analyses of apatites from a comprehensive data set across the shoulders of both grabens were used to compare their low temperature history, and to estimate the paleo-geothermal gradients before the onset of the last denudation/rifting stage (Late Jurassic). The paleo-geothermal gradients of both juxtaposed Gondwana margins similarly increase from the basement towards the respective rift shoulder from 15–20°Ckm −1 to 25–30°Ckm −1 . This trend of increasing paleo-geothermal gradients, together with a denudation episode commencing in the Early Cretaceous and coeval igneous activity, indicates a common rifting stage accompanying the breakup of Gondwana in the India-Antarctica sector.

Post Permian tectono-thermal evolution of western Dronning Maud Land, East Antarctica: an apatite fission-track approach

New apatite fission-track (AFT) ages fromHeimefrontfjella andMannefallknausane indlcate that the Mesoproterozoic basement and Permian sedimentary cover rocks were heated to c. 100°C during the Mesozoic. Heating was due to the burial by up to 2000 m of Jurassic lavas at c. 180 Ma, when the area was affected by the BouvetKaroo hot spot. Near the developing coastline, the lava pile was quickly eroded and in part deposited on the continental shelf as pebbly and coarse-grained volcaniclastic sandstones. The AFT data inhcate that farther inland the lava pile was not eroded until c. 100 Ma, and the Palaeozoic unconformity between the Mesoproterozoic basement and Permo-Carboniferous sedimentary rocks as a reference plane remained at temperatures of c. 80°C. Formation of an up to 800 m b. s.1. deep graben in front of Heimefrontfjella as well as flexural upllft and rapid denudational cooling of the not extended crust from Heimefrontfjella southwards occurred at c. 100 Ma. It is speculated that a period of major plate reorganisation and new rfing at c. 100 Ma is responsible for affecting a much wider continental margin as far inland as Heimefrontfjella and producing a total relief in excess of 3500 m.

The Mesozoic Victoria Basin: Vanished link between Antarctica and Australia

The Transantarctic Mountains (TAM) are the largest non-compressional mountain belt in the world. Their origin is traditionally related to crustal thickening during the Jurassic Ferrar magmatic event that was followed by episodic uplift in the Early and Late Cretaceous and since the Paleocene. This concept of a long-lived morphological high constitutes a base of virtually all Gondwana reconstructions and global climate models. Here we demonstrate that crossover age relationships between thermochronological (apatite fission track) data and stratigraphic information contradict this established interpretation. Instead these data, together with a wealth of independent thermal indicators and geological evidence require the existence of a vast intra-Gondwana basin between at least Late Triassic and Late Cretaceous times, including during the Ferrar magmatic event. Referred to here as the Mesozoic Victoria Basin (MVB), this basin formed during crustal extension across the paleo-Pacific margin of Antarctica and Australia. Uplift of the TAM with associated basin inversion commenced only with the development of the West Antarctic Rift System in Paleogene times. The recognition of the long-lived MVB has primary consequences for the general understanding of the landscape of Gondwana and the breakup between Antarctica and Australia, West Antarctic rifting and uplift of the TAM, and global long-term climate evolution and faunal radiation.

Thermal history of the Vestfold Hills (East Antarctica) between Lambert rifting and Gondwana break-up, evidence from apatite fission track data

Analysis of five basement samples from the Vestfold Hills (East Antarctica) reveals pooled apatite fission track (FT) ages ranging from 188 to 264 Ma and mean lengths of 13.7 to 14.9 μm. Quantitative thermal histories derived from these data give consistent results indicating onset of cooling/denudation began sometime prior to 240 Ma, with final cooling below 105°–125°C occurring between 240 and 220 Ma (Triassic). A Cretaceous denudation phase can be inferred from the sedimentary record of the Prydz Bay offshore the Vestfold Hills. The two denudational episodes are likely associated with Palaeozoic large-scale rifting processes that led to the formation of the adjacent Lambert Graben, and to the Cretaceous Gondwana break-up between Antarctica and India. Subsequent evolution of the East Antarctic passive continental margin likely occurred throughout the Cenozoic based on the depositional record in Prydz Bay and constraints (though tentative) from FT data.

The Main Shear Zone in Sør Rondane, East Antarctica: Implications for the late-Pan-African tectonic evolution of Dronning Maud Land

Structural investigations in western Sor Rondane, eastern Dronning Maud Land (DML), provide new insights into the tectonic evolution of East Antarctica. One of the main structural features is the approximately 120 km long and several hundred meters wide WSW-ENE trending Main Shear Zone (MSZ). It is characterized by dextral high-strain ductile deformation under peak amphibolite-facies conditions. Crosscutting relationships with dated magmatic rocks bracket the activity of the MSZ between late Ediacaran to Cambrian times (circa 560 to 530 Ma). The MSZ separates Pan-African greenschist- to granulite-facies metamorphic rocks with “East African” affinities in the north from a Rayner-age early Neoproterozoic gabbro-tonalite-trondhjemite-granodiorite complex with “Indo-Antarctic” affinities in the south. It is interpreted to represent an important lithotectonic strike-slip boundary at a position close to the eastern margin of the East African-Antarctic Orogen (EAAO), which is assumed to be located farther south in the ice-covered region. Together with the possibly coeval left-lateral South Orvin Shear Zone in central DML, the MSZ may be related to NE directed lateral escape of the EAAO, whereas the Heimefront Shear Zone and South Kirwanveggen Shear Zone of western DML are part of the south directed branch of this bilateral system.

Origin of bentonites and detrital zircons of the Paleocene Basilika Formation, Svalbard

The Paleocene was a time of transition for the Arctic, with magmatic activity of the High Arctic Large Igneous Province giving way to magmatism of the North Atlantic Large Igneous Province in connection to plate tectonic changes in the Arctic and North Atlantic. In this study we investigate the Paleocene magmatic record and sediment pathways of the Basilika Formation exposed in the Central Tertiary Basin of Svalbard. By means of geochemistry, Sm–Nd isotopic signatures and zircon U–Pb geochronology we investigate the characteristics of several bentonite layers contained in the Basilika Formation, as well as the provenance of the intercalated clastic sediments. Our data show that the volcanic ash layers of the Basilika Formation, which were diagenetically altered to bentonites, originate from alkaline continental-rift magmatism such as the last, explosive stages of the High Arctic Large Igneous Province in North Greenland and the Canadian Arctic. The volcanic ash layers were deposited on Svalbard in a flat shelf environment with dominant sediment supply from the east. Dating of detrital zircons suggests that the detritus was derived from Siberian sources, primarily from the Verkhoyansk Fold-and-Thrust Belt, which would require transport over ~3000 km across the Arctic.

Exhumation history along the eastern Amundsen Sea coast, West Antarctica, revealed by low‐temperature thermochronology

West Antarctica experienced a complex tectonic history, which is still poorly documented, in part due to extensive ice cover. Here, we reconstruct the Cretaceous to present thermo-tectonic history of Pine Island Bay area and its adjacent coasts, based on a combination of apatite and zircon fission track and apatite (U-Th-Sm)/He thermochronology. In addition, we report petrographic information for the catchments of Pine Island, Thurston Island and Thwaites glaciers. Our data suggest that the underlying bedrock of the Pine Island and Thwaites Glacier catchments are very different and vary from granitoids to (Cenozoic?) volcanogenic sequences and low-grade metamorphics. Our thermochronology data show that the upper crustal rocks of Pine Island Bay experienced very rapid cooling during the late Cretaceous. We attribute this rapid cooling of basement rocks and associated reduction in mean elevation to tectonic denudation driven by gravitational collapse of the Cretaceous orogen along the proto-Pacific Gondwana margin. Rapid Cretaceous crustal cooling was followed by very slow cooling during the Cenozoic, with no erosional response – within the limits of thermochronological methods – to the onset of glaciation and subsequent climatic changes. Cenozoic rifting within the West Antarctic Rift appears to have had little effect on erosion processes around Pine Island Bay; instead, our data suggest Cenozoic crustal tilting towards Pine Island Trough, a major geomorphic feature previously suggested to be a branch of the rift system.