Saturday, June 08, 2019

Pondering the Precambrian #28




A cyanobacteria normally associated with the Phanerozoic has been found in Ediacaran deposits in China.

There was a significant shift in what the limiting nutrients were across the Ediacaran/Cambrian boundary.

How did the black shales form across the Ediacaran/Cambrian boundary?

Was the Sao Francisco Basin a restricted basin during the Ediacaran?

A section in China appears to be a record of the late Ediacaran glaciations, showing a cold, dry climate.

The Cathayasian block was attached to Gondwana since 630 million years ago.

The fate of an inland sea from during the Neoproterozoic gets discussed.

Evidence of the Milkanovich cycles is preserved in Ediacaran deposits.

Tubular fossils from the Weng'an Biota are algae, not metazoans.

Weng'an Biota also provides examples of preserved encysting of eukaryotes.


Could the banded iron formations of the Cryogenian be related to ocean acidification?

There is evidence of a less than complete snowball earth from China during the Marinoan Glaciation.

Cryogenian Period deposits of Datangpo Formation of China from the interglacial period between the Sturtian and Marinoan glaciations show a very stratified ocean.

The majority of the time, the NeoProterozoic oceans were anoxic and were supersaturated with dolomite.


Fungus fossils appear to have been found in Tonian (neoproterozoic) or Stenian (mesoproterozoic) deposits in Canada.

There appears to have been a paleorifting event during the Tonian of the Sao Francisco-Congo continent.

The Sognefjel complex appears to have formed in the Asgardian Sea during the early Tonian.

Did the Paleo-South China Ocean close during the Tonian?


The Eastern European Craton has a Mesoproterozoic signal.

The southern Grenville formation dates from Mesoproterozoic and is from purely Laurentian sources.

Reported stromatolites from a Stenian lake cannot be proven to be biogenic.


600 million years of sedimentation is examined from the Paleoproterozoic of Lapland.

Statherian Period evolution of the Oolongbuluke terraine is explained.

In Brazil, the Sobreiro Formation appears to be from the Orosirian/Statherian boundary.


There is evidence of retreating oceanic slab subduction from the NeoArchean of China.

Evidence from India suggests there was significant local variation in Archean ocean conditions.

The Caozhuang basin appears to be a case of sagduction.

Fossils from paleoarchean South Africa show bacteria dividing and they appear to be very similar to cyanobacteria Pleurocapsales.

Eoarchean stromatolites get examined.


Was the Earth covered in a lava ocean before Theia impacted and created the moon?


What are the implications of a hotter mantle, but colder subduction during the Precambrian?

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