Late Neoproterozoic Baltic paleosol: Intense weathering at high latitude?

Liivamägi, Sirle; Somelar, Peeter; Mahaney, William C.; Kirs, Juho; Vircava, Ilze; Kirsimäe, Kalle

doi:10.1130/g35209.1

Cited by 39 publications

(17 citation statements)

References 31 publications

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“…To add to the complexity, intense weathering may have occurred at high palaeolatitudes in Baltica during the Ediacaran (Liivamägi et al, 2014(Liivamägi et al, , 2015.…”

Section: Palaeolatitude Of Proterozoic Glacial Successionsmentioning

confidence: 98%

Strongly seasonal Proterozoic glacial climate in low palaeolatitudes: Radically different climate system on the pre-Ediacaran Earth

Williams

Schmidt

Young

2016

Geoscience Frontiers

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Proterozoic (pre-Ediacaran) glaciations occurred under strongly seasonal climates near sea level in low palaeolatitudes. Metre-scale primary sand wedges in Cryogenian periglacial deposits are identical to those actively forming, through the infilling of seasonal (winter) thermal contraction-cracks in permafrost by windblown sand, in present-day polar regions with a mean monthly air temperature range of 40°C and mean annual air temperatures of -20°C or lower. Varve-like rhythmites with dropstones in Proterozoic glacial successions are consistent with an active seasonal freeze-thaw cycle. The seasonal (annual) oscillation of sea level recorded by tidal rhythmites in Cryogenian glacial successions indicates a significant seasonal cycle and extensive open seas. Palaeomagnetic data determined directly for Proterozoic glacial deposits and closely associated rocks indicate low palaeolatitudes: Cryogenian deposits in South Australia accumulated at ≤10°, most other Cryogenian deposits at <20° and Palaeoproterozoic deposits at <15° palaeolatitude. Palaeomagnetic data imply that the Proterozoic geomagnetic field approximated a geocentric axial dipole, hence palaeolatitudes represent geographic latitudes. The Cryogenian glacial environment included ice-free, continental permafrost regions with ground frozen on a kyr time-scale, aeolian sandsheets, extensive and long-lived open seas, and an active hydrological cycle. This palaeoenvironment conflicts with the 'snowball Earth' and 'slushball Earth' hypotheses, which cannot accommodate large seasonal changes of temperature near the equator. Consequently, their proponents have attempted to refute the evidence for strong seasonality by M A N U S C R I P T A C C E P T E D ACCEPTED MANUSCRIPT 2introducing Popperian 'auxiliary assumptions'. However, non-actualistic arguments that the Cryogenian sand wedges indicate diurnal or weakly seasonal temperature changes are based on misunderstandings of periglacial processes. Modelling of a strongly seasonal climate for a frozen-over Earth is invalidated by the evidence for persistent open seas and ice-free continental regions during Cryogenian glaciations, and gives a mean monthly air temperature range of only ≤10°C for ≤10° latitude. By contrast, a strongly seasonal climate in low palaeolatitudes, based on the actualistic interpretation of cryogenic sand wedges and other structures, is consistent with a high obliquity of the ecliptic (>54°) during Proterozoic lowlatitude glaciations, whereby the equator would be cooler than the poles, on average, and global seasonality would be greatly amplified.

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“…To add to the complexity, intense weathering may have occurred at high palaeolatitudes in Baltica during the Ediacaran (Liivamägi et al, 2014(Liivamägi et al, , 2015.…”

Section: Palaeolatitude Of Proterozoic Glacial Successionsmentioning

confidence: 98%

Strongly seasonal Proterozoic glacial climate in low palaeolatitudes: Radically different climate system on the pre-Ediacaran Earth

Williams

Schmidt

Young

2016

Geoscience Frontiers

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“…A weathered and bleached zone, affecting the basement to a maximum depth of 5 m at the top of the peneplain, is common in southern Sweden (Hadding 1929;Lundegårdh et al 1973;Elvhage & Lidmar-Bergström 1987) reach tens of metres (Liivamägi et al 2014). Weathering profiles associated with the peneplain are also found in many places in southern Norway (Rekstad 1903;Högbom & Ahlström 1924;Spjeldnaes 1955;Skjeseth 1962a;Nystuen 1966).…”

Section: Unconformity With a Weathered Zonementioning

confidence: 99%

“…According to plate reconstructions by Torsvik & Rehnström (2001) and Li et al (2008), Baltica moved to high latitudes around 580-600 Ma during the non-Snowball-Earth Gaskiers glaciations at 580-590 Ma (Halverson et al 2005), before entering low, equatorial latitudes in late Ediacaran to Early Cambrian times (550-530 Ma). It has been speculated that intensely leached Ediacaran palaeosol in Baltica reflects intense chemical weathering during renewed greenhouse climate and high atmospheric CO 2 (Liivamägi et al 2014).…”

Section: Denudation Burial and Alteration Of The Sub-cambrian Peneplainmentioning

confidence: 99%

The Sub-Cambrian Peneplain in southern Norway: its geological significance and its implications for post-Caledonian faulting, uplift and denudation

Gabrielsen

Nystuen

Jarsve

et al. 2015

JGS

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The Sub-Cambrian Peneplain in southern Norway formed in the Cryogenian–early Cambrian. It was transgressed in the Cambrian–early Ordovician, and subsequently broken up by Caledonian thrusting, post-Caledonian normal faulting and regional uplift. In southern Norway the Sub-Cambrian Peneplain is generally expressed as an angular unconformity or nonconformity surface with no apparent deep weathering. In some localities the basement is characterized by a weathered top. Furthermore, the basement may have a mineralized top in some cases. The peneplain is commonly overlain by in situ regolith, and/or Cryogenian glacial diamictite, Lower–Middle Cambrian siliciclastic sediments, Lower–Upper Cambrian black shale or Lower Ordovician limestone. It has commonly mildly tectonized contacts, but occasionally displays contacts that have been completely destroyed by Caledonian thrusting and reworked into fault rocks. Tracing the peneplain across southern Norway reveals a fault-affected and fault-delineated plateau with a sloping eastern margin. Onshore cumulative offsets record vertical movements of > 2000 m. A 1–5° dip below Caledonian nappes suggests a flexural component related to tectonic overburden. As the oldest identifiable and dateable surface covering much of Scandinavia the peneplain constitutes the reference surface for studies of the younger regional morphotectonic evolution. Its shape supports the interpretation that Cenozoic uplift combined with faulting, not smooth flexural doming, caused the Southern Scandes high in South Norway.

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“…It is a well preserved and unmetamorphosed weathering profile characterized by a mineral alteration sequence topped by up to 7-8 m thick strongly weathered zone composed of kaolinite, Fe-oxyhydroxide and residual quartz. Kaolinite content in the uppermost part of weathering profile can exceed 60% of mineral phases and indicates a strong and deep weathering, possibly under a warm and humid climate (Liivamägi et al, 2014(Liivamägi et al, , 2015. APS mineralization in the Baltic weathering crust was found in a profile developed on a postorogenic unmetamorphosed intrusion composed of mediumgrained monzogabbro rich in magmatic apatite and titanomagnetite.…”

Section: Introductionmentioning

confidence: 98%

“…In this contribution we studied an exceptionally rich APS mineralization (up to 4 wt.% of mineral phases) in a Neoproterozoic (Ediacaran) weathering crust (Baltic paleosol sensu Liivamägi et al, 2014) developed on Paleo-Mesoproterozoic crystalline basement in northern Estonia, former Baltica continent. It is a well preserved and unmetamorphosed weathering profile characterized by a mineral alteration sequence topped by up to 7-8 m thick strongly weathered zone composed of kaolinite, Fe-oxyhydroxide and residual quartz.…”

Section: Introductionmentioning

confidence: 99%

Origin and paleoenvironmental interpretation of aluminum phosphate–sulfate minerals in a Neoproterozoic Baltic paleosol

Vircava

Somelar

Liivamägi

et al. 2015

Sedimentary Geology

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Late Neoproterozoic Baltic paleosol: Intense weathering at high latitude?

Cited by 39 publications

References 31 publications

Strongly seasonal Proterozoic glacial climate in low palaeolatitudes: Radically different climate system on the pre-Ediacaran Earth

Strongly seasonal Proterozoic glacial climate in low palaeolatitudes: Radically different climate system on the pre-Ediacaran Earth

The Sub-Cambrian Peneplain in southern Norway: its geological significance and its implications for post-Caledonian faulting, uplift and denudation

Origin and paleoenvironmental interpretation of aluminum phosphate–sulfate minerals in a Neoproterozoic Baltic paleosol

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