Earth’s magnetic ield as new ocean crust is formed. Each stripe
thus represents a change in the polarity of the Earth’s magnetic
ield lips in geological time.
The stripes suggested that the Miocene sediments had been
deposited on ocean crust that was more than 20 million years
old. This was counter to conventional interpretations of the
Red Sea, which implied that sea-loor spreading and ocean crust
formation began only 5 million years ago.
We then applied the latest geophysical processing methods
which revealed the presence of eight stripes that could be corre-
lated to a global database. This suggested that the ocean crust
formed 22–26 million years ago during the Oligocene era.
The implication of this was that ocean crust formation in the
Red Sea occurred in two discrete spreading events: the present-
day sealoor spreading was superimposed on an older segment
of ocean crust. The two events were separated by 17 million
years of relative tectonic calm during which 4 km of sediment
was laid down.
So what stalled the sealoor spreading? The answer was not
to be found in the Red Sea itself but further to the north in
the Zagros Mountains of Iran. These mountains record the
closure of another ancient ocean called Tethys.
Sealoor spreading in the Red Sea was likely initiated as the
hot mantle of the Afar Plume thermally weakened the
African–Arabian crust. It began pushing the African and
Arabian plates apart, but stalled when the leading edge of the
Arabian plate collided with Iran, slowing the northward migra-
tion of Arabia and creating the Zagros Mountains. That was
22 million years ago.
Fast forward to the present day. The geological community
has now collected 50 years of geological and geophysical data
in and around the Red Sea. Perhaps the most important dataset
is a combined satellite and marine magnetic, gravity and sea
loor depth data that provides high resolution images of the
entire Red Sea for the very irst time. The patterns in the
magnetic and gravity data reveal the extent of present-day
sealoor spreading, the distribution of the ocean crust, and the
extent of the older spreading segment.
We applied geophysical iltering techniques used for mineral
exploration to this data, and the results were intriguing. They
tell us, for instance, that the conventional thinking about oceans
opening by continuously unzipping is not applicable to the
Red Sea. Rather, the process appears to happen in segments.
The pattern of ocean crust formation shows many similar-
ities to the Woodlark Basin, a small ocean basin formed at the
northern edge of the Australian tectonic plate to the imme-
diate east of Papua New Guinea. This poses compelling ques-
tions around why such very different tectonic systems would
produce almost identical patterns of spreading.
We are now collaborating with the University of Adelaide
to map how magma pushes up from the mantle so that we can
understand the link between magmatism and ocean crust forma-
tion. And at Monash University we are working with Prof
Sandy Cruden to create an innovative modelling experiment to
replicate the patterns of Red Sea ocean formation. We hope
this will lead to a deeper understanding of the dynamics of this
intriguing tectonic system.
Khalid’s knock at my door opened up new and exciting
research and collaboration opportunities, took me out of my
comfort zone and opened my eyes to another world.
Peter Betts is a Professor in the School of Earth, Atmosphere and Environment and
Associate Dean of Graduate Research at Monash University's Faculty of Science.JUNE 2016|| 27Peter Betts standing on exposed coral reef on the Farasan Islands in the southern Red
Sea. The coral has been uplifted by upwelling of a salt diapir beneath the reef.Figure 1. The Red Sea is undergoing
active seafloor spreading where the
African, Arabian and Indian plates all
meet. Wikimedia Commons