Marie Busfield
Royal Holloway, University of London
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Journal of the Geological Society | 2014
Marie Busfield; D. P. Le Heron
The Cryogenian record of South Australia includes the type region of the Sturtian glaciation, the oldest of three pan-global icehouse intervals during the Neoproterozoic. Data are presented from previously little described sections at Holowilena Creek, Oladdie Creek and Hillpara Creek in the central and southern Flinders Ranges, where five facies associations are recognized. These are (1) diamictite and conglomerate, (2) interbedded heterolithic deposits, (3) hummocky cross-stratified sandstone, (4) lonestone-bearing siltstone, and (5) ferruginous siltstone and sandstone. The succession reveals significant lateral and vertical facies variation, which is linked to a complex inherited palaeotopography and distance from the sediment source. Repeated stratigraphic occurrences of striated clasts and abundant ice-rafted debris strongly support recurrent glacial influence on sedimentation. The intercalation of gravitationally reworked diamictites, dropstone-bearing siltstone and dropstone-free siltstone testifies to dynamic sedimentation within a periodically glacially influenced subaqueous environment. Sequence stratigraphic analysis identifies four glacial advance systems tracts, separated by three glacial retreat systems tracts, wherein hummocky cross-stratified sandstones attest to open water conditions. These findings support dynamic ice sheet behaviour in South Australia, and provide clear evidence for repeated intra-Sturtian ice sheet recession.
Journal of the Geological Society | 2014
Daniel P. Le Heron; Marie Busfield; Anthony R. Prave
The Kingston Peak Formation is a diamictite-bearing succession that crops out in the Death Valley region, California, USA. An exceptionally thick (>1.5 km) outcrop belt in its type area (the Kingston Range) provides clear insights into the dynamics of mid-Cryogenian (‘Sturtian’) ice sheets in Laurentia. Seven detailed logs allow the lateral and vertical distribution of facies associations to be assessed. We recognize (1) diamictite facies association (ice-proximal glacigenic debris flows), (2) lonestone-bearing facies association (ice-marginal hemipelagic deposits and low-density gravity flows with iceberg rafting), (3) pebble to boulder conglomerate facies association (ice-proximal cogenetic glacigenic debris flows and high-density turbidites), (4) megaclast facies association (olistostrome and hemipelagic sediments subject to ice-rafting), and (5) interbedded heterolithics facies association (low-density turbidites and hemipelagic deposits). The stratigraphic motif allows three glacial cycles to be inferred across the range. Ice-minimum conditions interrupting the Kingston Peak succession are associated with the development of an olistostrome complex, succeeded by a thick accumulation of boulder conglomerates deposited during ice readvance. The data testify to a strong glacial influence on sedimentation within this ancient subaqueous succession, and to highly dynamic ice sheet behaviour with clear glacial cycles during the Sturtian glaciation.
Journal of the Geological Society | 2018
Thomas Vandyk; D. P. Le Heron; David M. Chew; Jeffrey M. Amato; Matthew F. Thirlwall; C. M. Dehler; Juliane Hennig; S. R. Castonguay; T. Knott; S. Tofaif; Dilshad O. Ali; Christina Manning; Marie Busfield; Daniel Doepke; Nathalie V. Grassineau
Olistolith production and magmatism are processes commonly associated with extensional tectonic settings, such as rift basins. We present a cautionary exemplar from one such Precambrian basin, in which we reinterpret metabasite bodies, previously documented as sills, to be olistoliths. We nevertheless demonstrate that, on the basis of field observation alone, the previous but erroneous sill interpretation is parsimonious. Indeed, it is only by using isotopic age and compositional analysis that the true identities of these metabasite olistoliths are revealed. We present new data from metabasites and metasedimentary strata of the Kingston Peak Formation (Cryogenian) and Crystal Spring Formation (Mesoproterozoic) of Death Valley, USA. These include field observations, U–Pb apatite ages, U–Pb zircon ages (detrital and igneous) and whole-rock geochemistry. These data also provide a new maximum age for the base of the Pahrump Group and suggest that the Crystal Spring Diabase was more tholeiitic than previously thought. Similar sill/olistolith misinterpretations may have occurred elsewhere, potentially producing erroneous age and tectonic-setting interpretations of surrounding strata. This is particularly relevant in Precambrian rocks, where fossil age constraints are rare. This is illustrated herein using a potential example from the Neoproterozoic literature of the Lufilian belt, Africa. We caution others against Precambrian olistoliths masquerading as sills. Supplementary material: Details of a meta-igneous boulder from P12 of the Silurian Hills, LA-ICP-MS and whole-rock geochemistry methods and standards, and U–Pb apatite and zircon isotopic data, including standards and selected cathodoluminescence images, are available at https://doi.org/10.6084/m9.figshare.c.3990639
Sedimentology | 2013
Daniel P. Le Heron; Marie Busfield; Fred Kamona
Proceedings of the Geologists' Association | 2013
Marie Busfield; Daniel P. Le Heron
Sedimentology | 2016
Marie Busfield; Daniel P. Le Heron
Proceedings of the Geologists' Association | 2015
Marie Busfield; Jonathan R. Lee; James B. Riding; Jan Zalasiewicz; Sarah V. Lee
Palaeogeography, Palaeoclimatology, Palaeoecology | 2013
D. P. Le Heron; Marie Busfield; E. Le Ber; A.F. Kamona
Sedimentology | 2014
Daniel P. Le Heron; Marie Busfield; Alan S. Collins
Sedimentology | 2016
Daniel P. Le Heron; Marie Busfield