From the first link:
Although such studies illustrated that Precambriancarbonate marine environments were dominated by microbial mats, including layered communities of phototrophic and chemotrophic microorganisms, much of the unbioturbated siliciclastic sedimentary record from this interval was thought to lack structures attributable to microbial processes. Recent studies of anomalous soft-bodied preservation (Gehling, 1996, this issue) and sedimentologic structures characteristic of the later Neoproterozoic (Pflu¨ger and Gresse, 1996; Pflueger and Sarkar, 1996; Hagadorn and Bottjer, 1997; McIlroy and Walter, 1997; Pflu¨ger, this issue; Schieber, this issue; Simonson and Carney, this issue), have begun to change these views, suggesting that many siliciclastic sediments were likely not only to have hosted a variety of layered microbial communities, but that such communities may have actually been the dominant biotic influence on clastic seafloor environments prior to the onset of bioturbation (Seilacher and Pflu¨ger, 1994).
From the second link:
Abstract
: The Sukharikha River section contains more than 800 m of fossiliferous Vendian and Lower Cambrian carbonate
rock deposited in ramp, shelf, and slope environments. A diverse fauna of small shelly fossils, calcibionts, brachiopods,
trilobites, and archaeocyaths has allowed us to develop a multi-taxa biostratigraphic framework for this section. A dearth of
distinctive fossils low in the Sukharikha Formation
prevents us from determining the position of the VendianñCambrian
boundary. Abundant small shelly fossils and archaeocyaths in the uppermost Sukharikha Formation and low in the
Krasnoporog Formation provide ample biostratigraphic control near the base of the Tommotian Stage, but the
NemakitñDaldynian ñ Tommotian boundary, as defined at UlakhanñSulugur on the Aldan River, is temporally ambiguous.
For this reason there is no precise definition of this boundary. In the Sukharikha River section we have provisionally placed
the base of the Tommotian Stage at the first occurrence of
Nochoroicyathus sunnaginicus
Zone archaeocyaths, about 1.5 m
below the top of the Sukharikha Formation. However, we suppose that this horizon actually predates the deposition of
nominally basal Tommotian taxa in the Aldan region. A new global stratotype section for the NemakitñDaldynian ñ
Tommotian boundary should be selected, and this section may turn out to be a good candidate. The paleontological richness
(especially small shelly fossils and archaeocyaths), the apparent absence of long depositional hiatuses, and the presence of
well-preserved limestones suggest that the Sukharikha River section contains the combination of paleontological,
sedimentological, and isotopic data to
resolve some fundamental problems in Early Cambrian stratigraphy. Emphasis mine
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