Papers by Joanne Whittaker
<p>The migration of mid-ocean ridges is driven by asymmetric plate motions on eithe... more <p>The migration of mid-ocean ridges is driven by asymmetric plate motions on either ridge flank transmitted from far-field subduction forces. Within this model, the geometry and location of mid-ocean ridges are independent of lower-mantle dynamics. However, this fails to recognise the attraction between mid-ocean ridges and mantle plumes. Using numerical models of mantle convection, we show that plumes with high buoyancy flux (> 6000 kg/s) can capture mid-ocean ridges within a 1000 km radius and anchor them in place. If the plume buoyancy flux wanes below 1000 kg/s the ridge may be released, potentially resulting in rapid migration rates that trigger a major plate reorganisation. Plume-ridge interactions are commonly preserved as conjugate large igneous provinces (LIPs), which form on each flank of a mid-ocean ridge as new crust is created. The decoupling of ridges from plumes are demarcated by a switch from conjugate LIPs, formed by a plume beneath a spreading ridge, to trails of intraplate hotspot volcanoes signifying the plume and ridge have separated. We demonstrate that the waning buoyancy flux of the Kerguelen plume, inferred from the geochemistry of eruption products, resulted in its decoupling with the SE Indian Ridge spurring rapid northward migration of the Australian plate. Our modelling predicts that following plume-ridge decoupling, the waning plume can tilt 15° within the upper mantle towards the migrating ridge, providing an explanation for diffuse volcanism and low eruption volumes along the Kerguelen Archipelago. Our results have significant implications for other plume-ridge interactions globally such as the Iceland, Tristan, and Easter plumes, and the generation of intraplate hotspot volcanoes proximal to mid-ocean ridges.</p>
Models generated by the methods described by Stål et al (in review GRL 2019). The repository cont... more Models generated by the methods described by Stål et al (in review GRL 2019). The repository contains boundary models for Antarctica and reference models for Australia. Sum, union, squared sum, intersect, product and squared intersect refers to the technique used to combine boundary models derived from three datasets: Seismic shear wave speed from tomography study (An et al, 2015, doi:10.1002/2014jb011332), Free air gravity (Förste at al, 2014, GFZ Data Services), and bedmap elevation (Fretwell et al, 2013, doi:10.5194/tc-7-375-2013)
Seafloor Geomorphology as Benthic Habitat, 2020
We present highlights of the first multibeam and bottom sampling survey surrounding the UNESCO Wo... more We present highlights of the first multibeam and bottom sampling survey surrounding the UNESCO World Heritage listed Heard and McDonald Islands (HIMI), conducted in the HIMI Marine Reserve InnerMarine Zone. These insular shelf data reveal that persistent eastward flowing currents and retreating glaciers drive patterns of sediment distribution. Sedimentary bedform directionality, corroborated by drifter data, suggest that the prevailing energy in this region dominates from west to east, and is deflected in an anticlockwise direction around Heard Island, causing sediment deposition to be concentrated on the eastern (downcurrent) side of the islands. Sediment bedform morphology likely mirrors the eastward flowing Antarctic Circumpolar Current and oscillating east!west tidal currents. Thick sediment accumulations north of Heard Island may be related to deglaciation since the Last Glacial Maximum. Sample sites on the northern down-current side of Heard Islands and on the western up-current side of the McDonald Islands contain a diverse range of taxonomic groups compared to all other sample sites. Benthic specimens obtained in rock dredges and sediment grabs show a range of invertebrate species that are likely endemic to the HIMI region.
<p><strong>Deep mantle plumes are buoyant upwellings ... more <p><strong>Deep mantle plumes are buoyant upwellings rising from the Earth’s core-mantle boundary to its surface, and describing most hotspot chains. Mechanisms to explain dual chains of hotspot volcanoes for the Hawaiian-Emperor and Yellowstone chains fail to explain the geochemical similarity and large distances between contemporaneous volcanoes of the Tasmantid and Lord Howe chains in the SW Pacific. Using numerical models of mantle convection, we demonstrate how slab-plume interaction can lead to sustained plume branching over a period of >40 million years to produce parallel volcanic chains that track plate motion. We propose a three-part model: first, slabs stagnate in the upper mantle, explaining fast upper mantle P-wave velocity anomalies; second, deflection of a plume conduit by a stagnating slab splits it into two branches 650-900 km apart, aligning to the orientation of the trench axis; third, plume branches heat the stagnating slab causing partial melting and release of volatiles which percolate to the surface forming two contemporaneous volcanic chains with slab-influenced EM1 signatures. Our results highlight the critical role of long-lived subduction on the evolution and behaviour of intraplate volcanism.</strong></p>
This record describes the End of Voyage (EOV) archive from the Marine National Facility (MNF) RV ... more This record describes the End of Voyage (EOV) archive from the Marine National Facility (MNF) RV Investigator research voyage IN2019_V04, titled "Hotspot dynamics in the Coral Sea: connections between the Australian plate and deep Earth." The voyage took place from Cairns (QLD) to Brisbane (QLD) between August 7 and September 3, 2019. For further information please refer to the voyage documentation links below. Instruments used and data collected include: Regular measurements: Acoustic Doppler Current Profiler (ADCP; 75, 150 KHz ), Lowered ADCP (LADCP), Fisheries echosounder (EK60), Multibeam Echosounder (EM710, EM122), Sub-bottom Profiler (SBP120), Gravimeter, GPS Positioning System, Doppler Velocity Log, Temperature, Humidity, Pressure, Wind and Rain sensors, Photosynthetically Active Radiation (PAR) sensor, Precision Infrared Radiometer (PIR), Precision Spectral Pyranometer (PSP), Nephelometer, pCO2, Condensation Particle Counters (CPC), Cloud Condensation Nuclei counte...
The first public version of maps generated by the methods described by Stål et al (to submit 2019... more The first public version of maps generated by the methods described by Stål et al (to submit 2019). Updated with SCons sconstruct file containing all code used for the study.
Kroenke Canyon on the Ontong Java Plateau (OJP) extends for approximately 500 km between its hypo... more Kroenke Canyon on the Ontong Java Plateau (OJP) extends for approximately 500 km between its hypothesized origin at Ontong Java and Nukumanu atolls and its mouth at the transition between the Plateau and the Nauru Basin. For FK141015, RV Falkor departed Pohnpei, Federated States of Micronesia, on 15 October 2014, and arrived in Guam, USA, on 3 November 2014. During the voyage we acquired primarily EM302 multibeam data along 6,288 line-km over the 13 days in the survey area, augmented by EM710 multibeam data in shallower water. Overall, the EM302 ensonified 23,439 km2 of seafloor in the survey area, in water depths ranging from 87 m to 4,444 m (Figure ES1). XBT data (12 casts) were acquired routinely, and the CTD was tested, returning useful data from one cast. Of similar scale and relief to the Grand Canyon (Arizona, USA), and with multiple tributaries, Kroenke Canyon incises pelagic sediment, sedimentary rock, and igneous rock of OJP. We mapped the thalweg of Kroenke Canyon from ap...
Encyclopedia of Solid Earth Geophysics, 2021
Nature Geoscience, 2019
Ocean-floor plateaus are not voluminous lava flows from central volcanoes as thought, but anomalo... more Ocean-floor plateaus are not voluminous lava flows from central volcanoes as thought, but anomalously thick oceanic crust, suggest magnetic anomaly patterns from the Shatsky Rise, in the northwestern Pacific Ocean.
GSA Today, 2012
... 600 Ma reconciles paleomagnetic data for the NAC and WAC (green and cyan) at 1070 Ma; however... more ... 600 Ma reconciles paleomagnetic data for the NAC and WAC (green and cyan) at 1070 Ma; however, this model does not reconcile these poles with an ... John Cannon helped to prepare the text, and the cover image associated with this paper was prepared by Sabin Zahirovic. ...
Geochemistry, Geophysics, Geosystems, 2015
Oceanic fracture zone traces are widely used in studies of seafloor morphology and plate kinemati... more Oceanic fracture zone traces are widely used in studies of seafloor morphology and plate kinematics. Satellite altimetry missions have resulted in high-resolution gravity maps in which all major fracture zones and other tectonic fabric can be identified, and numerous scientists have digitized such lineaments. We have initiated a community effort to maintain low-cost infrastructure that allows seafloor fabric lineaments to be stored, accessed, and updated. A key improvement over past efforts is our processing software (released as a GMT5 supplement) that allows for semiautomatic corrections to previously digitized fracture zone traces given improved gridded data sets. Here we report on our seafloor fabric processing tools, which complement our database of seafloor fabric lineations, magnetic anomaly identifications, and plate kinematic models. However, the usefulness of specific FZ traces decay with time as new data become available. For instance, the efforts of Gahagan et al. [1988] and Cande et al. [1989] relied on early processing of widely spaced, stacked 1-D SEASAT and GEOSAT profiles. Today, we have extensive 2-D coverage of higher accuracy that allows ever subtler fracture zone trends to be found [Sandwell et al., 2014]. Furthermore, digitized FZ traces are usually not updated, or perhaps only some FZs are redigitized, leading to a heterogeneous, partly global data set reflecting different eras of data qualities and personal styles and procedures for digitizing (i.e., did Key Points: Infrastructure to facilitate research in plate tectonic reconstructions Refines location of digitized fracture zone traces Analyzes fracture zones for alongtrace changes
Geophysical Research Letters, 2015
A reorganization centered on the Pacific plate occurred~53-47 million years ago. A "top-down" pla... more A reorganization centered on the Pacific plate occurred~53-47 million years ago. A "top-down" plate tectonic mechanism, complete subduction of the Izanagi plate, as opposed to a "bottom-up" mantle flow mechanism, has been proposed as the main driver. Verification based on marine geophysical observations is impossible as most ocean crust recording this event has been subducted. Using a forward modeling approach, which assimilates surface plate velocities and shallow thermal structure of slabs into mantle flow models, we show that complete Izanagi plate subduction and margin-wide slab detachment induced a major change in sub-Pacific mantle flow, from dominantly southward before 60 Ma to north-northeastward after 50 Ma. Our results agree with onshore geology, mantle tomography, and the inferred motion of the Hawaiian hot spot and are consistent with a plate tectonic process driving the rapid plate-mantle reorganization in the Pacific hemisphere between 60 and 50 Ma. This reorganization is reflected in tectonic changes in the Pacific and surrounding ocean basins. SETON ET AL.
Precambrian Research, 2014
The oldest known rocks in Tasmania occur in the Proterozoic Rocky Cape Group, a ∼10 km thick quar... more The oldest known rocks in Tasmania occur in the Proterozoic Rocky Cape Group, a ∼10 km thick quartzarenite-siltstone-pelite-dominated succession, previously constrained to have been deposited between 1450 Ma and 750 Ma. The Rocky Cape Group contains the enigmatic fossil Horodyskia ('string of beads') and has the potential to place Tasmania within supercontinent reconstructions. Detrital zircon and authigenic monazite grains dated via U-Pb laser ablation-inductively coupled plasma mass spectrometry (LA-ICPMS) analysis yield a deposition window between c. 1450 Ma (youngest zircon populations) and c. 1330 Ma (oldest authigenic monazite population) for the ∼9 km thick lower-middle units (Pedder River Siltstone, Lagoon River Quartzite, Balfour Subgroup which hosts Horodyskia, Detention Subgroup). The upper units (∼1 km) include the Irby Siltstone, which is younger than c. 1310 Ma; this unit is likely separated from both the lower-middle units and the overlying c. <1010 Ma Jacob Quartzite by disconformities. The lower-middle Rocky Cape Group is dominated by detrital zircon populations between 1600 and 1900 Ma, with subordinate populations at c. 1450 Ma and a spread of older grains mostly between 2300 and 2900 Ma. The overlying Irby Siltstone has a bimodal detrital zircon distribution with a dominant peak at c. 1340 Ma and a secondary peak at c. 1720 Ma; no >1900 Ma grains were identified. Authigenic monazite age distributions are complex, with multiple age domains within most samples. The common Pb corrected 206 U/ 238 Pb ages, defined by oldest grains in each sample, identify three statistically significant groups: (1) 1358-1292 Ma (inclusive of two sigma errors) (Lagoon River Quartzite and Pedder River Siltstone), (2) 1283-1239 Ma (Cowrie Siltstone and Balfour Subgroup), and (3) 1085 ± 9 Ma (Detention Subgroup). We suggest monazite was precipitated during episodic fluid flow events at these three stages in various parts of the basin. The original source for REE-bearing fluids could be detrital monazite, which is rarely preserved, and/or organic matter from the interbedded carbonaceous shales. The Rocky Cape Group has a shared provenance with the higher-grade metasediments (Surprise Bay and Fraser formations) of nearby King Island; the newly derived depositional ages also overlap and support the correlation of these rock associations. On the basis of current datasets, there are no obvious correlations that can be made with Mesoproterozoic basins preserved in mainland Australia. Instead, an overlap in the timing of deposition, similarities in detrital zircon signatures and analogous depositional environment suggests the c. 1.45-1.37 Ga upper Belt-Purcell Supergroup (Missoula and Lemhi groups) of western North America constitutes a plausible correlation with the Tasmanian Mesoproterozoic succession. If the (unexposed) Palaeoproterozoic basement of Tasmania correlates with the Transantarctic Mountains region of East Antarctica as previously proposed, we suggest that the overlying Mesoproterozoic sequences were deposited during rifting of the supercontinent Nuna, between proto-Australia
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Papers by Joanne Whittaker