And The Bands Played On BANDED · PDF file2 billion years ago 3 billion years ago 4 billion...
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Ocean surface 25 metres 70 metres O O O O O C O Carbon dioxide Methane Water Oxygen + = + CYANOBACTERIA 20 um l Filamentous PHOTOFERROTROPHS Coccoidal Spindle-shaped 10 um l 10 um l BANDED IRONSTONE BARBERTON MAKHONJWA GEOTRAIL Iron Brew Around three billion years ago, there was no breathable oxygen in the air and none in the warm ocean. Because of this, great quantities of iron were dissolved in the water. Rust In Peace We are not sure how oxygen appeared in the ocean. It may have had a volcanic origin, or perhaps UV radiation produced oxygen in the atmosphere. Perhaps cyanobacteria near the surface produced it by photo- synthesis, just as green plants do today, or maybe specialised floating microbes used sunlight to take oxygen from other molecules. It may have been a combination of these processes. However it was produced, oxygen combined with dissolved iron to form iron oxide (rust). Innumerable tiny red flakes floated down to form layers on the sea floor. Take A Deep Breath First, oxygen oxidised iron. Once the iron in the sea had been used up, oxygen removed methane from the atmosphere. While this was happening, weathering of minerals at the Earth’s surface and on the sea floor used up much oxygen as well. Gradually, oxygen began to build up in the atmosphere. These processes led to the Great Oxygenation Event ~ 2.4 billion years ago and changed the face of Earth. Simplified timeline of the build-up of oxygen in the atmosphere. We are not sure when oxygen-producing photosynthesis began. Atmospheric oxygen concentrations are shown as a percentage of today’s level. Adapted from: © 2012 Nature Education Courtesy of Biddanda et al. All rights reserved. Modern humans are born Dinosaurs become extinct First hard-shelled animals Permian mass extinction Plants take root on land First multicellular organisms 5 billion years ago 1 billion years ago Today 3 billion years ago Percent of Today’s Oxygen 100 1 0.001 ATMOSPHERIC O 2 OCEANIC O 2 PHOTOSYNTHESIS First cells with a nucleus Rise in atmospheric oxygen Great Oxygenation Event Banded Iron Formations 2 billion years ago 3 billion years ago 4 billion years ago Formation of the Earth Oldest zircon crystal Formation of the Moon Banded Ironstone 3.24 billion years ago 4 3 1 Today 2 ? oxygen-producing ? mixed oxygen-producing very low oxygen ? oxygen 5 NOT ENOUGH OXYGEN AVAILABLE TO TAKE IRON OUT OF THE OCEAN ALL OCEANIC IRON OXIDISED OXYGEN OXIDISES IRON. BANDED IRON FORMATIONS PROTEROZOIC PHANEROZOIC ARCHAEAN HADEAN Biomats, first widespread signs of life Kaapvaal craton, the first continent THE BARBERTON SUPERGROUP Moodies Group Shallow-water sandstones ~ 3.5 km thick. Onverwacht Group Dominated by volcanic lavas, ~ 9 km thick. Few sedimentary strata, all of oceanic origin. Fig Tree Group Deep-water sediments and volcanics ~3 km thick. BARBERTON GREENSTONE BELT Above: Bands of iron-rich chert and haematite. Yes. . . No. . . Maybe! How banded iron layers form is hotly debated. To obtain fresh and continuous rock, a drill hole more than 500 m deep was made a few hundred metres from here in 2011. As geoscientists study the distribution of minerals and elements in these strata in detail, they will learn more about the early ocean, atmosphere and life on our planet. Collisions of pieces of crust (tectonic plates) have folded these rocks like folds pushed into a rug. Horizontal layers have been folded to almost vertical. www.geotrail.co.za Geological consultant: Christoph Heubeck BARBERTON BRANCH BATOBIC BARBERTON TOURISM & BIODIVERSITY CORRIDOR Karl and Lesley Lane - Hamilton-Fynch: www.hamiltonfynch.com Jointly funded by the Barberton Chamber of Business and the National Department of Tourism After T. McCarthy, B. Rubidge. The Story of Earth & Life, Struik. Site And The Bands Played On The banding in the ironstone may have been caused by periodic change in temperature. Bacteria were active when it was warm and so oxidized lots of iron. When it was cold they slowed down or even switched to feed on other dead bacteria drifting down into the depths. When this happened, silica-rich chert was laid down. This was repeated over and over as the climate changed. Did you know? ¢ Almost all the iron in the world comes from the banded iron formations laid down in this period so long ago. ¢ About 2 billion tonnes of iron ore are mined each year worldwide. HOW BANDED IRON AND OXYGEN MAY HAVE BEEN PRODUCED PHOTOSYNTHESIS: Cyanobacteria pump oxygen into the ocean and atmosphere. PHOTOFERROTROPHS: These strange microbes have their name from: photo = light; ferro = iron; troph = to do with feeding and used very dim light to oxidise (rust) dissolved iron. Particles of iron oxide stuck to their coats forming an armour coating. This killed them and they sank to the sea floor forming layers of haematite and goethite.
Transcript of And The Bands Played On BANDED · PDF file2 billion years ago 3 billion years ago 4 billion...
Ocean surface
25 metres
70 metres
OO
OO
OC
O
Carbon dioxide
Methane
Water
Oxygen
+=
+
CYANOBACTERIA
20 uml
Filamentous
phOTOFERROTROphs
Coccoidal spindle-shaped10 uml
10 uml
BAN
DED
IRO
NST
ON
E BA
RBER
TON
MA
KH
ON
JWA
GEO
TRA
ILIron BrewAround three billion years ago, there wasno breathable oxygen in the air and none inthe warm ocean. Because of this, great quantities of iron were dissolved in the water.Rust In PeaceWe are not sure how oxygen appeared in the ocean. It may have had a volcanic origin, or perhaps UV radiation produced oxygen in the atmosphere. perhaps cyanobacteria near the surface produced it by photo-synthesis, just as green plants do today, or maybe specialised floating microbes used sunlight to take oxygen from other molecules. It may have been a combination of these processes. however it was produced, oxygen combined with dissolved iron to form iron oxide (rust). Innumerable tiny red flakes floated down to form layers on the sea floor.
Take A Deep BreathFirst, oxygen oxidised iron. Once the iron in the sea had been used up, oxygen removed methane from the atmosphere. While this was happening, weathering of minerals at the Earth’s surface and on the sea floor used up much oxygen as well. Gradually, oxygen began to build up in the atmosphere. These processes led to the Great Oxygenation Event ~ 2.4 billion years ago and changed the face of Earth.
Simplified timeline of the build-up of oxygen in the atmosphere. We are not sure when oxygen-producing photosynthesis began. Atmospheric oxygen concentrations are shown as a percentage of today’s level.
Adapted from: © 2012 Nature Education Courtesy of Biddanda et al. All rights reserved.
Modern humans are bornDinosaurs become extinct
First hard-shelled animals
permian mass extinction
plants take root on land
First multicellular organisms
5 billion years ago
1 billion years ago
Today
3 billion years ago
BA
RB
ER
TO
N G
RE
EN
ST
ON
E B
ELT
percent of Today’s Oxygen
100
1 0.00
1AT
MO
sph
ERIC
O2
OC
EAN
IC O
2
phO
TOsY
NTh
EsIs
First cells with a nucleus
Rise in atmospheric oxygen
Great Oxygenation Event Banded Iron Formations
2 billion years ago
3 billion years ago
4 billion years ago
Formation of the Earth
Oldest zircon crystalFormation of the Moon
Banded Ironstone 3.24 billion years ago
4
3
1
Today
2
? ox
ygen
-pro
duci
ng ?
m
ixed
oxyg
en-p
rodu
cing
v
ery
low
oxy
gen
?
o
xyge
n
5
NOT ENOUGhOXYGEN
AVAILABLE TOTAKE IRON
OUT OF ThEOCEAN
ALL OCEANIC IRONOXIDIsED
OXYGEN OXIDIsEs
IRON.BANDED IRONFORMATIONs
PRO
TERO
ZO
IC P
HAN
ERO
ZO
ICAR
CH
AEAN
HAD
EAN
Biomats, first widespread signs of lifeKaapvaal craton, the first continent
BA
RB
ER
TO
N G
RE
EN
ST
ON
E B
ELT
THE BARBERTON SUPERGROUPMoodies Group shallow-water sandstones ~ 3.5 km thick.
Onverwacht Group Dominated by volcanic lavas, ~ 9 km thick. Few sedimentary strata, all of oceanic origin.
Fig Tree Group Deep-water sediments and volcanics ~3 km thick.
BA
RB
ER
TO
N G
RE
EN
ST
ON
E B
ELT
Above: Bands of iron-rich chert and haematite.
Yes. . . No. . . Maybe! how banded iron layers form is hotly debated. To obtain fresh and continuous rock, a drill hole more than 500 m deep was made a few hundred metres from here in 2011. As geoscientists study the distribution of minerals and elements in these strata in detail, they will learn more about the early ocean, atmosphere and life on our planet.
Collisions of pieces of crust (tectonic plates) have folded these rocks like folds pushed into a rug.
Horizontal layers have been folded to almost vertical.
www.geotrail.co.zaGeological consultant: Christoph Heubeck
BARBERTON BRANCh
BATOBICBARBERTON TOURISM &BIODIVERSITY CORRIDOR
BATOBICBARBERTON TOURISM &BIODIVERSITY CORRIDOR
BATOBICBARBERTON TOURISM &BIODIVERSITY CORRIDOR
BATOBICBARBERTON TOURISM &BIODIVERSITY CORRIDOR
Karl
and
Lesle
y La
ne -
ham
ilton
-Fyn
ch: w
ww
.ham
ilton
fync
h.co
m
Jointly funded by the Barberton Chamber of Business and the National Department of Tourism
After T. McCarthy, B. Rubidge. The story of Earth & Life, struik.
Site
And The Bands Played OnThe banding in the ironstone may have been caused by periodic change in temperature. Bacteria were active when it was warm and so oxidized lots of iron. When it was cold they slowed down or even switched to feed on other dead bacteria drifting down into the depths. When this happened, silica-rich chert was laid down. This was repeated over and over as the climate changed.
Did you know? ¢ Almost all the iron in the world comes from the banded iron formations laid down in this period so long ago.
¢ About 2 billion tonnes of iron ore are mined each year worldwide.
hOW BANDED IRONAND OXYGEN MAY hAVEBEEN pRODUCEDphOTOsYNThEsIs:Cyanobacteria pump oxygeninto the ocean and atmosphere.phOTOFERROTROphs:These strange microbes have their name from:photo = light; ferro = iron;troph = to do with feedingand used very dim light to oxidise (rust) dissolved iron.
particles of iron oxide stuck to their coats forming an armour coating. This killed them and they sank to the sea floor forming layers of haematite and goethite.
