|
|
 |
|||||||||||||||||
|
|||||||||||||||||
 |
|||||||||||||||||
| JOURNAL HOME | HELP | CONTACT PUBLISHER | SUBSCRIBE | ARCHIVE | SEARCH | TABLE OF CONTENTS |
1 School of Geography and Geosciences, University of St. Andrews, St. Andrews, Fife KYI6 9AL, Scotland, UK
Stratigraphically discrete glacigenic dropstone intervals have been identified within six separate Neoproterozoic glaciomarine successions: the ca. 720 Ma Chuos Formation (southwestern Congo craton) and Surprise Diamictite (southwestern Laurentia), the ca. 600 Ma Ghaub Formation (Congo craton), Blässkrans Formation (northwestern Kalahari craton) and Wildrose Diamictite (southwestern Laurentia), and the post–595 Ma lower Southern Highland Group (northeast Laurentia). These dropstone intervals are interstratified with hemipelagic, dropstone-free lithologies that record periods devoid of glacial rainout. Such episodic deposition requires, at a most rudimentary level, temporally compatible environmental fluctuations to generate melting of ice. The Ghaub Diamictite is particularly revealing in this regard, given that, according to the snowball Earth hypothesis, it had to be deposited either during glacial maxima (totally frozen seas) or melt back (geologically instantaneous) owing to its low-latitude setting and association with carbonates that record highly depleted 
13C values. The consistency of facies features shared by all six glaciomarine successions leads us to speculate that the temporally discrete glacial- rainout events (including diamictites deposited in low latitudes) record a dynamic glacial environment and that such conditions were characteristic of Neoproterozoic glaciations in general. These observations indicate that Neoproterozoic seas were not totally frozen and that the hydrologic cycle was functioning.
Key Words: Neoproterozoic • glaciation • ice rafting
This article has been cited by other articles:
|
|
 |
|
  A.R. Prave, A.E. Fallick, C.W. Thomas, and C.M. Graham A composite C-isotope profile for the Neoproterozoic Dalradian Supergroup of Scotland and Ireland Journal of the Geological Society, September 1, 2009; 166(5): 845 - 857. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 A. G. Smith Neoproterozoic timescales and stratigraphy Geological Society, London, Special Publications, January 1, 2009; 326(1): 27 - 54. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 Y. F. Zheng, B. Gong, Z. F. Zhao, Y. B. Wu, and F. K. Chen Zircon U-Pb age and o isotope evidence for neoproterozoic low-18O magmatism during supercontinental rifting in South China: Implications for the snowball earth event Am J Sci, April 1, 2008; 308(4): 484 - 516. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
P. J. Pazos, L. S. Bettucci, and J. Loureiro The Neoproterozoic glacial record in the Rio de la Plata Craton: a critical reappraisal Geological Society, London, Special Publications, January 1, 2008; 294(1): 343 - 364. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
N. M. Chumakov Climates and climate zonality of the Vendian: geological evidence Geological Society, London, Special Publications, January 1, 2007; 286(1): 15 - 26. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 P. F. Hoffman 28th DeBeers Alex. Du Toit Memorial Lecture, 2004. On Cryogenian (Neoproterozoic) ice-sheet dynamics and the limitations of the glacial sedimentary record South African Journal of Geology, December 1, 2005; 108(4): 557 - 577. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 J. E. Blair and S. B. Hedges Molecular Phylogeny and Divergence Times of Deuterostome Animals Mol. Biol. Evol., November 1, 2005; 22(11): 2275 - 2284. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 K. J. Peterson, M. A. McPeek, and D. A. D. Evans Tempo and mode of early animal evolution: inferences from rocks, Hox, and molecular clocks Paleobiology, June 1, 2005; 31(2_Suppl): 36 - 55. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 J. Leather, P. A. Allen, M. D. Brasier, and A. Cozzi Neoproterozoic snowball Earth under scrutiny: Evidence from the Fiq glaciation of Oman Geology, October 1, 2002; 30(10): 891 - 894. [Abstract] [Full Text] [PDF]
|
|
| JOURNAL HOME | HELP | CONTACT PUBLISHER | SUBSCRIBE | ARCHIVE | SEARCH | TABLE OF CONTENTS |
