[X] My Assistant

[Guest_AlexBlackwell_*]

For those without access, SpringerLink is offering temporary free access to the February 2006 issue of Origins of Life and Evolution of Biospheres.

[Guest_BruceMoomaw_*]

While we're on the general subject of Origins of Life and the Evolution of the Biosphere, today's "Nature" has an article describing new isotopic evidence that methanogen bacteria were alive and very plentiful on Earth 3.5 billion years ago: http://www.nature.com/nature/journal/v440/...ature04584.html

Given how shaky a lot of the trumpeted fossil evidence of extremely early terrestrial life forms turns out to be when you actually look at it, this seems to me to be an important new confirmation that life really was very much up and running very early in Earth's history.

[tty]

Hmm... 3.5 Gyr old, hydrothermal deposits and from Pilbarra. That means they are from those odd stromatolite-like deposits in the Warrawoona group that most of those shaky very early microfossils come from. Maybe they really are biogenic?

tty

[ljk4-1]

WORLD'S OLDEST FOSSILS, OR NO SUCH THING? (Ancient Worlds News, 8/6/06)

Researchers say they have found "compelling" new evidence of the earliest
known forms of life on Earth in ancient rock in Australia.

http://abc.net.au/science/news/ancient/Anc...ish_1655990.htm

[tty]

An interesting paper in the latest issue of Palaeontologia Electronica on microorganisms and stromatolites in extremely acid hot springs:

http://palaeo-electronica.org/2007_1/sinter/index.html

Microfacies Of Stromatolitic Sinter From Acid-Sulphate-Chloride Springs At Parariki Stream, Rotokawa Geothermal Field, New Zealand

We present a unique, scale-integrated, and spatially controlled study of acid-derived sinters and their abiotic-biotic relations. Through a microfacies-based approach, we provide context and constraints for inferring causal factors in the formation of these sinters. Four distinct microfacies of siliceous stromatolitic sinter formation and their associated microbiota were elucidated from acid-sulphate-chloride hot spring outflows (pH 2.1-2.3, 91-30°C), located on the floodplain of Parariki Stream, ~1 km north of Lake Rotokawa in the Rotokawa Geothermal Field. Microfacies 1 comprises cup- to ridge-shaped sinters forming close to vents (91-64°C) with relatively high water and gas discharge. Sinter surfaces are characterised by relatively small (0.5 cm high) spicules, irregular, gnarly siliceous textures and colonisation by coccoidal microorganisms (1-1.5 µm in diameter). Microfacies 2 consists of spiculose (1 cm high) sinters colonised by bacilli (1-2.3 µm long), diatoms and coccoidal algae (2–10 µm in diameter) that are surrounded by quiescent waters (85-30°C) with little steam discharge. Microfacies 3 is typified by parallel-laminated sinters forming on slightly steepened areas that are colonised by bacilli (1-8 µm long), diatoms and coccoidal algae (2–10 µm in diameter) and exposed to fluctuating water levels (60-54°C). Microfacies 4 constitutes thin siliceous sinter rims forming mainly on small pumiceous clasts that rest upon moist (67-45°C) sandy substrates and colonised by bacilli (1-2.3 µm long), diatoms and spherical cells (2-6 µm in diameter). Sinter morphology, texture and formation mechanisms, as well as microbial colonisation, depend on a variety of environmental constraints that can act at a scale of centimetres or less. Textural development of the sinters, including their laminae, is attributed to a combination of abiotic and biotic factors. The differential preservation potentials of microbial communities need to be taken into account when assessing biodiversity of ancient sinters.

Read it so You know what to look for down in Victoria.....