STATEMENT: OLDEST ROCKS AND FOSSILS
STATEMENT: ÄLTESTE GESTEINE UND FOSSILIEN
Es wurde schon viel darüber diskutiert, welches Gestein das älteste ist und worin sich möglicherweise erste Lebensspuren befinden (von links oben nach rechts unten): Nuvvuagittuq- Grünstein aus Kanada, evt. mit Lebensspuren, Acasta-Gneiss aus Kanada oder Isua-Grünstein von Grönland (Lebensspuren?). Auf jeden Fall findet das Ganze an der Grenze vom Archaikum zum Hadaikum statt also vor plus/minus 4 Milliarden Jahren... Ich habe ein Statement eingeholt von Kristen Coleman (Science Mall, USA).
The discussion about the oldest rock of the world, containing perhaps biogenic structures does not end (left above to right below): Nuvvuagittuq Greenstone, possibly with traces of life, Acasta Gneis or Isua Greenstone (traces of life?). It happens at the border between Archean and Hadean (ca 4 billions)... I bought Acasta Gneis from Thomas Kapitany, Australia, Nuvvuagittuq Greenstone and Isua Greenstone from Science Mall/USA. So I asked Kristen Coleman (Science Mall) to give me a statement:
“Conflict arises on the method of dating, accuracy, and exact location collected. When we recommend an age date it is with the confidence in saying that "the general average" microprobed or sampled.
Nuvvuagittug is about 4.3 with a minimum age of 3.8 Ga. The Nuvvuagittuq Greenstone Belt consists of recorded isotopic compositions that can only be produced in the Hadean (i.e. older than 4 billion years ago) and the complete isotopic study of all the lithologies included in the Nuvvuagittuq Greenstone Belt suggests that it was formed NEARLY 4.4 billion years ago. It IS the oldest without question and is only surpassed by just a little by the Jack Hills Zircons. (Below a picture of the Nuvvuagittuq Greenstone Belt in Québec/Canada.)
Isua is about 3.8 Ga.
Acasta Gneiss is 3.5-4 Ga.
Then there is Akilia sediments which include banded iron beds. Akilia rocks do show evidence of life at 3.85 Ga. This is the earliest time life would have had an opportunity to "organize" itself in a very tight zone, as before 3.9 Ga the Earth would have been very inhospitable. It is a little different from Isua
as it is from a different location.
North Pole stromatolite, probably one of the oldest examples of preserved fossil stromatolites in the geological record are about 3.5 Ga, found in Western Australia. Some stromatolites from South Africa are also in the same range (some people don't know that), such as the Fig Tree chert stromatolite at about 3.2 Ga.Gunflint chert stromatolite is 1.9 Ga. Apex Chert is 3.45 Ga. Barberton Greenstone and similar belts is about 3.5 - 3.8 Ga.
The oldest material on Earth is the Jack Hills zircons, with an average date of 4.4 Ga (below, with a piece of oldest stromatolites from Strelley Pool, Western Australia, ca 3.5 billions).
The problem lies in whether the reported date represents the age that the rock itself formed or the residue of an isotopic signature of older material that melted to form the rock.
Being that the youngest age of Nuvvuagittuq is 3.8 Ga and the probable cutoff for life to have existed is at 3.9 Ga, it is entirely possible that Nuvvuagittuq contains some ultra-primitive biogenic marker. This is just my opinion but I would not rule it out. It is like finding any other ancient fossil, you don't find the fossil until you separate it from the rock. Heat, pressure and tectonic forces could have utterly destroyed any evidence that it once did exist.
We don't know for sure yet, so it is an open-ended debate.”
Jack-Hills-Zirkone aus Australien befinden sich in dem Gestein oben (4,4 Mrd.). - Unten ein Stück mit den ältesten bisher bekannten Stromatolithen: Strelley Pool, ebenfalls Australien (3,5 Mrd.).