Peripatus Home Page pix1Black.gif (807 bytes) Paleontology >> Vendian PeriodUpdated: 02-Feb-2017 

Vendian Period


Abstract

This page describes the Vendian Period, including stratigraphy, and explains its relationship with the Ediacaran Period.

Keywords: stratigraphy, Vendian Period, Vendian biota, fossil record, evolution, extinction

Introduction

The Vendian System and Period were first proposed by Sokolov 1952, from drill core sequences on the Siberian Platform (Sokolov & Fedonkin 1984). Although the Vendian was not embraced quickly, and was not adopted by the Subcommission on Precambrian Stratigraphy, it came into almost universal de facto usage. A new stratotype in Belarus was proposed (Makhnach & Veretennikov 2001) to address the perceived shortcoming of the original type section in a drill core.

There is much confusion over the status of the Vendian, so it is worth further detailing its status, particularly in relation to the “new” Ediacaran Period (Knoll et al. 2004). The Vendian is an Eurasian geochronologic and chronostratigraphic unit, just as the Sinian is recognised in China. It was never recognised by the Subcommission on Precambrian Stratigraphy which had, in 1991, opted instead for a “Neoproterozoic III” interval defined “strictly by chonometric age, without reference to events recorded in sedimetary rocks” (Knoll et al. 2004, p. 621). The recent recognition of a properly (GSSP) defined Ediacaran System and Period by the Subcommission on Precambrian Stratigraphy is certainly a step in the right direction, and it probably means that new publications will increasingly refer to the Ediacaran rather than the Vendian, and references to the latter outside of the Siberian Platform will eventually disappear. However, it does not mean, as some commentators have suggested, that the Vendian is suddenly invalidated as a legitimate geochronologic and chronostratigraphic unit, or that it has “gone away” in any sense.

The absolute age constraints on the Vendian interval have ebbed and flowed over the past few years; perhaps the best current estimate is from ~605 to 541 million years (Ma) ago, somewhat shorter than current estimates for the Ediacaran (~635 to 541 Ma; Cohen et al. 2015). Possibly, however, this is simply because nobody is bothering to revise the absolute age estimates for the base of the Vendian as new data and techniques come to light. To a first order approximation, it is probably reasonable to simply think of the Vendian as the Siberian equivalent to the Ediacaran. Much of the following text will take this approach.

Throughout the extent of the period, dominant organisms were simple, entirely marine, and for the most part soft-bodied: hard-bodied organisms did not occur until nearly the beginning of the Cambrian Period when the so-called “small shelly faunas” appeared.

 
 

Related Topics


Further Reading

  • Ogg et al. 2008: The Concise Geologic Time Scale. Cambridge.

Related Pages

     
     

    Stratigraphy

    Type Section/Sections

    The Vendian Period and System were first proposed by Sokolov 1952, from drill core sequences on the Siberian Platform. More recently, a new stratotype in Belarus was proposed by Makhnach & Veretennikov 2001.

    Lower (Sturtian-Vendian) Boundary

    The Sturtian is another geochronologic unit which is no longer in widespread use; it encompassed the Sturtian glaciation (one of the “snowball” events) and was defined in Australia.

    Placing the base of the Vendian is a somewhat pointless exercise today; probably nobody will ever complete the necessary work to provide an accurate chronology.

    Upper (Vendian-Cambrian) Boundary

    Since 1947, when H.E. Wheeler initiated debate with the suggestion that the Precambrian-Cambrian boundary should be based upon the first appearance of trilobites, much has ensued. Progress has largely been facilitated by the International Geological Congress (IGC) and the establishment in 1960 of a Subcommission on Cambrian Stratigraphy. The classical idea of placing the boundary at an unconformity has been displaced by the search for monofacial, continuous deposition sequences across the boundary, with the view to selecting a stratotype.

    The search itself produced a wealth of data from around the world – including the Palaeotethyan Belt, Siberian Platform, and England – eventually focusing upon south-east Newfoundland.

    Prior to 1990, the boundary was generally placed at the base of the Tommotian. However, in 1991 the International Subcommission on Cambrian Stratigraphy (through its Working Group on the Precambrian-Cambrian Boundary) made the official decision to draw the base on the Cambrian at the first appearance datum (FAD) of the distinctive horizontal burrow ichnofossil, Trichophycus (formerly Phycodes) pedum (Seilacher 1955, fig. 1), in the reference section at Fortune Head. This horizon correlates with the base of the Siberian Nemakit-Daldynian Stage, some 13 Ma earlier than the Tommotian, included within the Vendian in some older literature.

    [DELETE THIS BIT?] In 1991 the International Subcommission on Cambrian Stratigraphy (through its Working Group on the Precambrian-Cambrian Boundary) made the official decision to draw the base on the Cambrian at the first appearence date (FAD) of Trichophycus pedum (figure) in the reference section at Fortune Head.

    [insert image here]

    Chronology

    Paleogeography

    Major Tectonic Events

    The Precambrian supercontinent usually known as Rodinia (or, rarely, as Proto-Pangea or Ur-Pangea) formed ~1,000 Ma from the amalgamation of three or four pre-existing continents, in an event known as the Grenville Orogeny. Perhaps beginning ~700 Ma, but protracted over many millions of years, Rodinia began breaking up into three major blocks: West Gondwana, East Gondwana, and Laurasia. Subsequently – perhaps ~540 Ma – West and East Gondwana merged in the mountain-building event known as the Pan-African Orogeny. (After Rogers 1996.)

    Land and Sea

    Climate

    Paleontology

    General Characteristics

    Trace fossils ...

    Body fossils typically of cnidarian grade dating from as early as 600 or 610 Ma – e.g. the Twitya fossils are simple cup-shaped animals, possibly similar to the sea anemones of today.

    Doushantuo Phosphate embryos

    The “classic” Ediacarans ...

    Mineralised skeletons of uncertain affinity – the ‘small shelly fauna’ – appear just before the beginning of the Cambrian, ~550 Ma, increasing in numbers and diversity towards the Tommotian. The most common skeletal materials are calcium carbonate (aragonite or calcite) and varieties of calcium phosphate. Many of the latter may originally have been carbonates, phosphatized during preservation.

    The oldest of these to occur abundantly are Cloudina and the allied genera comprising the family Cloudinidae: small, conical fossils made of calcium carbonate, first (?) appearing in the Ediacaran Stirling Quartzite of California (Langille 1974) and persisting into the Cambrian. Anabarites and Cambrotubulus are other Ediacaran ‘small shelly’ taxa, known from Siberia and Mongolia.

    Major Taxa

    Stromatolites

    Cyanobacteria

    Acritarchs

    Porifera

    Twitya ?cnidarians

    Olivoiides?

    The “classic” Ediacarans are a diverse assemblage of enigmatic organisms. We will briefly discuss one genus, Dickinsonia, here – see my Ediacaran Biota page for more.

    Mollusca – Kimberella – material to right is used above; find something more suitable for this section. ”The fossil Kimberella quadrata was originally described from late Precambrian rocks of southern Australia. Reconstructed as a jellyfish, it was later assigned to the cubozoans (’box jellies’), and has been cited as a clear instance of an extant animal lineage present before the Cambrian. Until recently, Kimberella was known only from Australia, with the exception of some questionable north Indian specimens. We now have over thirty-five specimens of this fossil from the Winter Coast of the White Sea in northern Russia. Our study of the new material does not support a cnidarian affinity. We reconstruct Kimberella as a bilaterally symmetrical, benthic animal with a non-mineralized, univalved shell, resembling a mollusc in many respects. This is important evidence for the existence of large triploblastic metazoans in the Precambrian and indicates that the origin of the higher groups of protostomes lies well back in the Precambrian” (Fedonkin & Waggoner 1997, Abstract).

    Arthropods may be indicated by some Ediacaran fossils such as Parvancorina minchami.

    Echinodermata – Arkarua adami (Pound Subgroup, South Australia; Gehling 1987)

    Cloudina and the allied genera comprising the family Cloudinidae Hahn & Pflug 1985 are small, conical fossils made of calcium carbonate. Cloudinids are the oldest shelly animal fossils to appear abundantly in the fossil record, first appearing in the Stirling Quartzite of California (Langille 1974) and persisting into the Cambrian. It is not known what kind of organism produced Cloudina.

    Major Evolutionary Events

    There can be little doubt, on the basis of trace evidence alone, that bilaterian metazoans existed from early in the Ediacaran. Although some traces are simple, rather featureless, winding trails, “others display transverse rugae and contain pellets that can be interpreted as of fecal origin. The bilaterian nature of these traces is not in dispute. Furthermore, such traces must have been made by worms, some of which had lengths measured in centimetres, with through guts, which were capable of displacing sediment during some form of peristaltic locomotion, implying a system of body wall muscles antagonized by a hydrostatic skeleton. Such worms are more complex than flatworms, which cannot create such trails and do not leave fecal strings” (Valentine 1995, p. 90). Sets of paired hypichnial ridges strongly hint at an arthropod s.l. presence.

    Unfortunately, it is equally true that the relatively few body fossils known from the late Precambrian do not shed much light on the sequence of evolutionary advances that led to the famously diverse Cambrian taxa. There are a few sign-posts, however:

    • Sponges are widely recognised (e.g. Nielsen 2001, pp. 30, 506-507) to be the most primitive of living metazoans, occupying a basal position in metazoan phylogeny, as a sister group to all other Metazoa. Thus their first occurrence in the fossil record is a metric of particular interest. However, only rare occurrences of Precambrian sponges have been reported. The earliest record is of presumed sponge remains from the Doushantuo phosphates, dated around 570 Ma (Li et al. 1998), and the earliest described species is Paleophragmodictya reticulata from the ?555 Ma Ediacara locality. However, sponges could have occurred earlier and not been recognised; spicules are not necessarily diagnostic, even in living sponges (Dr. Allen Collins, pers. comm.)
    • Fossils of the Twitya Formation are generally presumed to be cnidarians, or at least as metazoans of cnidarian grade. “Interpretation as colonial aggregates of prokaryotes (e.g. Nostoc-like balls) is possible but is difficult to reconcile with the morphology and relatively high relief of the remains, their occurrence at the bottom of turbidite beds, and the lack of a carbonaceous film outlining them, particularly in view of the of the fact that carbonaceous compressions are present in the formation” (Hofmann et al. 1990, p. 1202). Of principal significance is this occurrence of cnidarian-grade metazoans in pre-Varanger sediments, since the Varanger glaciation is sometimes cited as an evolutionary ‘bottleneck’ which arrested metazoan evolution.
    • In preserving evidence of bilaterians, the Vendian record provides constraints on the protostome-deuterostome split. If Kimberella is indeed a mollusc, as suggested by Fedonkin & Waggoner 1997, or the Ediacara/Zimnie Gory traces are correctly interpreted as radula scratches, we have evidence for derived protostomes at 555 Ma. Similarly, if Arkarua adami (from the Pound Subgroup, South Australia; Gehling 1987) is correctly interpreted as an echinoderm, we have evidence for a derived deuterostome of similar age. In either case, it follows that the P-D split must have occurred well before 555 Ma, which is in accordance with most ‘molecular clock’ studies.

    Mineralised skeletons of uncertain affinity – the ‘small shelly fauna’ – appear just before the beginning of the Cambrian, ~550 Ma, increasing in numbers and diversity towards the Tommotian. The most common skeletal materials are calcium carbonate (aragonite or calcite) and varieties of calcium phosphate. Many of the latter may originally have been carbonates, phosphatized during preservation.

    Lagerstätten

    Extinctions

    New Zealand Occurrences

    Precambrian rocks are almost unknown in New Zealand. Possibly the most likely contender is parts of the Balloon Formation, which is exposed in the Cobb Valley area: see Cooper & Grindley 1982, p. 50.

    References

    No reference data for [Wheeler 1947] .

    No reference data for [Seilacher 1955] .

    No reference data for [Makhnach & Veretennikov 2001] .

    Cohen, K.M.; Finney, S.C.; Gibbard, P.L.; Fan, J.X. 2015: The ICS international chronostratigraphic chart v 2015/01. Episodes 36: 199-204.

    Cooper, R.A.; Grindley, G.W. 1982: Late Proterozoic to Devonian sequences of southeastern Australia, Antarctica and New Zealand and their correlation. Geological Society of Australia Special Publication 9: 1-103.

    Fedonkin, M.A.; Waggoner, B. M. 1997: The Late Precambrian Fossil Kimberella is a Mollusc-Like Bilaterian Organism. Nature 388: 868-871. Nature.

    Gehling, J.G. 1987: Earliest known echinoderm a new Ediacaran fossil from the Pound Subgroup of South Australia. Alcheringa 11: 337-345. Alcheringa.

    Hofmann, H.J.; Narbonne, G.M.; Aitken, J.D. 1990: Ediacaran remains from intertillite beds in northwestern Canada. Geology 18: 1199-1202. Geology.

    Knoll, A.H.; Walter, M.R.; Narbonne, G.M.; Christie-Blick, N. 2004: A new period for the geologic time scale. Science 305: 621-622. Science.

    Langille, G.B. 1974: Problematic Calcareous Fossils from the Stirling Quartzite, Funeral Mountains, Inyo County, California. Gological Society of America Abstracts with Programs 6: 204-205. .

    Li, C.; Chen, J.; Hua, T. 1998: Precambrian Sponges with Cellular Structures. Science v. 279, issue of 6 February 1998, pp. 879 - 882. Science.

    Nielsen, C. 2001: Animal evolution: Interrelationships of the living phyla (second edition). Oxford University Press: 1-378.

    Ogg, J.G.; Ogg, G.; Gradstein, F.M. 2008: The Concise Geologic Time Scale. Cambridge: 1-177.

    Rogers, J.J.W. 1996: A history of the continents in the past three billion years. Jl. Geol. 104: 91-107. .

    Sokolov, B.S. 1952: On the Age of the Oldest Sedimentary Cover of the Russian Platform. Izvestiya Acad. Nauk SSSR, Geol. Ser. 5: 12-20. .

    Sokolov, B.S.; Fedonkin, M.A. 1984: The Vendian as the Terminal System of the Precambrian. Episodes, 7: 12-19. .

    Valentine, J.W. 1995: Late Precambrian bilaterians: Grades and clades. In Fitch, Walter M.; Ayala, Francisco J. 1995: Tempo and mode in evolution: Genetics and paleontology 50 years after Simpson. National Academy of Sciences, pp. 87-107. PNAS.


     Peripatus Home Page pix1Black.gif (807 bytes) Paleontology >> Vendian Period

    Hits counted from 1 Feb 2017: