Landscape and regolith features related to Miocene leucitite lava flows, El Capitan northeast of Cobar New South Wales

Kenneth McQueen, Ian Roach, B Pillans, W Dunlap, M Smith

    Research output: Contribution to journalArticle

    6 Citations (Scopus)

    Abstract

    Outcrops of leucitite lavas occur as scattered remnants up to 40 m thick in the El Capitan area, northeast of Cobar in western New South Wales. Two eruption sites have been located for these lavas. Preserved volcanic features indicate that the lavas were erupted on to a relatively low-relief, Early Miocene land surface, flowed along a shallow valley and underwent inflation. Geochemical analyses of the leucitites indicate only limited fractionation. Remnant outcrops of the leucitite lavas represent a very important time marker in the geomorphic history of the Cobar region, preserving evidence of both Early Miocene and post-Early Miocene landscape evolution and weathering conditions. A deep-weathering profile, similar to those common throughout the region and characterised by a ferruginous mottled zone and underlying bleached saprolite, is preserved beneath a dissected flow at one eruption site. Other deposits beneath the leucitite flows include baked soils, silcretes, and quartz-rich gravels and grits. Palaeomagnetic dating of the upper part of the deep-weathering profile indicates an Early to Middle Miocene age for hematite fixation. A new 40Ar/39Ar age on the volcanic plug at this site (17.14 ± 0.20 Ma, 2σ) refines the minimum eruption age for the leucitites and supports an Early Miocene age for ferruginisation of the deep-weathering profile. Topographic inversion of the basal contact of one of the leucitite flows indicates an average minimium erosion rate for the area of 1 m per million years. Weathering profiles on the leucitites are thin and lack significant ferruginisation or chemical leaching, indicating that post-Early Miocene weathering in the region has been very limited. These profiles also contain a significant aeolian component including abundant quartz dust
    Original languageEnglish
    Pages (from-to)1-17
    Number of pages17
    JournalAustralian Journal of Earth Sciences
    Volume54
    Issue number1
    DOIs
    Publication statusPublished - 2007

    Fingerprint

    regolith
    lava flow
    weathering profile
    Miocene
    volcanic eruption
    outcrop
    weathering
    quartz
    volcanic feature
    saprolite
    landscape evolution
    erosion rate
    inflation
    hematite
    fixation
    land surface
    gravel
    relief
    fractionation
    leaching

    Cite this

    McQueen, Kenneth ; Roach, Ian ; Pillans, B ; Dunlap, W ; Smith, M. / Landscape and regolith features related to Miocene leucitite lava flows, El Capitan northeast of Cobar New South Wales. In: Australian Journal of Earth Sciences. 2007 ; Vol. 54, No. 1. pp. 1-17.
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    title = "Landscape and regolith features related to Miocene leucitite lava flows, El Capitan northeast of Cobar New South Wales",
    abstract = "Outcrops of leucitite lavas occur as scattered remnants up to 40 m thick in the El Capitan area, northeast of Cobar in western New South Wales. Two eruption sites have been located for these lavas. Preserved volcanic features indicate that the lavas were erupted on to a relatively low-relief, Early Miocene land surface, flowed along a shallow valley and underwent inflation. Geochemical analyses of the leucitites indicate only limited fractionation. Remnant outcrops of the leucitite lavas represent a very important time marker in the geomorphic history of the Cobar region, preserving evidence of both Early Miocene and post-Early Miocene landscape evolution and weathering conditions. A deep-weathering profile, similar to those common throughout the region and characterised by a ferruginous mottled zone and underlying bleached saprolite, is preserved beneath a dissected flow at one eruption site. Other deposits beneath the leucitite flows include baked soils, silcretes, and quartz-rich gravels and grits. Palaeomagnetic dating of the upper part of the deep-weathering profile indicates an Early to Middle Miocene age for hematite fixation. A new 40Ar/39Ar age on the volcanic plug at this site (17.14 ± 0.20 Ma, 2σ) refines the minimum eruption age for the leucitites and supports an Early Miocene age for ferruginisation of the deep-weathering profile. Topographic inversion of the basal contact of one of the leucitite flows indicates an average minimium erosion rate for the area of 1 m per million years. Weathering profiles on the leucitites are thin and lack significant ferruginisation or chemical leaching, indicating that post-Early Miocene weathering in the region has been very limited. These profiles also contain a significant aeolian component including abundant quartz dust",
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    Landscape and regolith features related to Miocene leucitite lava flows, El Capitan northeast of Cobar New South Wales. / McQueen, Kenneth; Roach, Ian; Pillans, B; Dunlap, W; Smith, M.

    In: Australian Journal of Earth Sciences, Vol. 54, No. 1, 2007, p. 1-17.

    Research output: Contribution to journalArticle

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    T1 - Landscape and regolith features related to Miocene leucitite lava flows, El Capitan northeast of Cobar New South Wales

    AU - McQueen, Kenneth

    AU - Roach, Ian

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    AU - Smith, M

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    N2 - Outcrops of leucitite lavas occur as scattered remnants up to 40 m thick in the El Capitan area, northeast of Cobar in western New South Wales. Two eruption sites have been located for these lavas. Preserved volcanic features indicate that the lavas were erupted on to a relatively low-relief, Early Miocene land surface, flowed along a shallow valley and underwent inflation. Geochemical analyses of the leucitites indicate only limited fractionation. Remnant outcrops of the leucitite lavas represent a very important time marker in the geomorphic history of the Cobar region, preserving evidence of both Early Miocene and post-Early Miocene landscape evolution and weathering conditions. A deep-weathering profile, similar to those common throughout the region and characterised by a ferruginous mottled zone and underlying bleached saprolite, is preserved beneath a dissected flow at one eruption site. Other deposits beneath the leucitite flows include baked soils, silcretes, and quartz-rich gravels and grits. Palaeomagnetic dating of the upper part of the deep-weathering profile indicates an Early to Middle Miocene age for hematite fixation. A new 40Ar/39Ar age on the volcanic plug at this site (17.14 ± 0.20 Ma, 2σ) refines the minimum eruption age for the leucitites and supports an Early Miocene age for ferruginisation of the deep-weathering profile. Topographic inversion of the basal contact of one of the leucitite flows indicates an average minimium erosion rate for the area of 1 m per million years. Weathering profiles on the leucitites are thin and lack significant ferruginisation or chemical leaching, indicating that post-Early Miocene weathering in the region has been very limited. These profiles also contain a significant aeolian component including abundant quartz dust

    AB - Outcrops of leucitite lavas occur as scattered remnants up to 40 m thick in the El Capitan area, northeast of Cobar in western New South Wales. Two eruption sites have been located for these lavas. Preserved volcanic features indicate that the lavas were erupted on to a relatively low-relief, Early Miocene land surface, flowed along a shallow valley and underwent inflation. Geochemical analyses of the leucitites indicate only limited fractionation. Remnant outcrops of the leucitite lavas represent a very important time marker in the geomorphic history of the Cobar region, preserving evidence of both Early Miocene and post-Early Miocene landscape evolution and weathering conditions. A deep-weathering profile, similar to those common throughout the region and characterised by a ferruginous mottled zone and underlying bleached saprolite, is preserved beneath a dissected flow at one eruption site. Other deposits beneath the leucitite flows include baked soils, silcretes, and quartz-rich gravels and grits. Palaeomagnetic dating of the upper part of the deep-weathering profile indicates an Early to Middle Miocene age for hematite fixation. A new 40Ar/39Ar age on the volcanic plug at this site (17.14 ± 0.20 Ma, 2σ) refines the minimum eruption age for the leucitites and supports an Early Miocene age for ferruginisation of the deep-weathering profile. Topographic inversion of the basal contact of one of the leucitite flows indicates an average minimium erosion rate for the area of 1 m per million years. Weathering profiles on the leucitites are thin and lack significant ferruginisation or chemical leaching, indicating that post-Early Miocene weathering in the region has been very limited. These profiles also contain a significant aeolian component including abundant quartz dust

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    SN - 0812-0099

    IS - 1

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