constituting the Asian mosaic, and by the uplift of the
Himalayas and other chains farther north. These great disconnecting systems laterally eject plaques such as South
China and Indochina (Tapponnier et al. 2001). This deformation of the southern margin of Asia is in fact generalized
throughout the southern margin of Eurasia, in response to the
Africa-Europe overlap resulting in the Alpine orogeny. This
deformation contributed to the establishment of sea basins,
sometimes deep, in Eurasia. These basins were connected to
each other and extended from Western Europe to the foot of
the Tibetan zone (during the process of uplifting) to form a
vast epicontinental sea, the Paratethys, connected to the
Atlantic Ocean and to the Tethys. The intense deformation
of the southern margin of Eurasia during the Miocene
gradually isolated the Paratethys from the rest of the oceans.
Supplied only by runoff waters and subjected to the deformation of the substratum, this sea was gradually reabsorbed.
Today, the Caspian Sea and the Black Sea are the only
descendants of the Paratethys.
The Arabia-Eurasia collision during the Early Miocene
lead to the closure of the Neo-Tethys sea and the uplift of the
Zagros collisional wedge (Pirouz et al. 2017). In the Middle
Miocene, the northern part of the Arabian Peninsula became
exposed, marking the birth of the Mediterranean Sea. This
would dry up almost completely at the end of the Miocene
(the Messinian crisis) for a few hundred thousand years, due
to an upheaval in the Betic zone (Gibraltar region) combined
with a slight decrease in sea level. During the late Miocene,
the northward drift of Australia initiated the closure of the
Indonesian seaway, while the closure of the Central American Seaway linked to a tectonic uprising permanently isolated the Atlantic and Pacific waters.
Box: Focus on the uplift of the Tibetan Plateau.
Since 50 Ma, the average convergence speed between
India and Asia has remained around 5 cm per year.
The Himalayan range occurred due to the deformation
of the northern edge of the Indian sub-continent when
it was subducted under the Asian continent. To the
south of the Tsangpo suture is the Himalayan domain:
on Indian crust with remnants of the Tethyan sedimentary cover and accretion prism associated with
subduction of the Tethyan Ocean before collision.
North of the suture, the Tibetan plateau has sedimentary layers from the Asian paleomargin. These are two
very different realms with different Cenozoic geological histories, although related to the same event.
During the millions of years after the collision, a
proto-Himalayan chain must have developed on the
remains of the Andean chain associated with the
subduction of the Tethys, but the extent of this is not
known. The Tibetan plateau was still a low-lying area.
Two contrasting opinions have been proposed to
explain the uplift of the Tibetan plateau: a “soft Tibet”
model and a “staggered model”. The “soft Tibet”
model considers the uplift to be the result of an isostatic rebound caused by the “sinking” of the crustal
root of a thickened Tibetan proto-plateau. The plateau
reached its stable altitude of about 5000 m, and began
to creep, as evidenced by the normal faults that line the
southern plateau. The other theory (Tapponnier et al.
2001) considers, on the contrary, that the uplift took
place in successive stages. Part of the India-Asia collision is absorbed by the lateral extrusion of landmasses (South China, Indochina), which caused old
sutures inherited from the accretion of small landmasses during the Paleozoic and Mesozoic to protrude, profoundly modifying the paleogeography of
South-East Asia (resulting in the closure of the
Indonesian passage). These large strike-slip faults,
separating the landmasses, connect with small perpendicular faults parallel to each other. The associated
reliefs isolate small endorheic sedimentary basins
which gradually fill up with the output from the dismantling of the chain “like a bathtub”. The uplift of
the Tibetan plateau would have occurred in successive
stages since 50 Ma. The southern part of the Tibetan
plateau rose during the Eocene, the central part during
the Oligocene-Miocene and the northeastern part is
currently uplifting.
Conclusion
The Earth moved from being entirely composed of an
oceanic crust to the emergence of the first shreds of continental crust during the Archean, then to its episodic growth,
mainly during the Precambrian. The paleogeography of this
period is uncertain, given the small number of paleomagnetic data available, but it seems that the first consolidation
of landmasses into a supercontinent (followed by a break-up
phase) dates back to that time. It is only from the end of the
Precambrian that we have global paleogeographic reconstructions, but there are no unique and definitive solutions
for much of the Paleozoic, as uncertainties remain on the
arrangement of some continents and the dimensions of the
oceans. Paleogeographic reconstructions become more reliable at the end of the Paleozoic, and data from ocean kinematics makes it possible to constrain the relative positions of
some continents relative to others. The distribution of the
continents, either as they grouped together or dispersed,
represents an important climate forcing through direct and
2 The Changing Face of the Earth Throughout the Ages
45
Himalayas and other chains farther north. These great disconnecting systems laterally eject plaques such as South
China and Indochina (Tapponnier et al. 2001). This deformation of the southern margin of Asia is in fact generalized
throughout the southern margin of Eurasia, in response to the
Africa-Europe overlap resulting in the Alpine orogeny. This
deformation contributed to the establishment of sea basins,
sometimes deep, in Eurasia. These basins were connected to
each other and extended from Western Europe to the foot of
the Tibetan zone (during the process of uplifting) to form a
vast epicontinental sea, the Paratethys, connected to the
Atlantic Ocean and to the Tethys. The intense deformation
of the southern margin of Eurasia during the Miocene
gradually isolated the Paratethys from the rest of the oceans.
Supplied only by runoff waters and subjected to the deformation of the substratum, this sea was gradually reabsorbed.
Today, the Caspian Sea and the Black Sea are the only
descendants of the Paratethys.
The Arabia-Eurasia collision during the Early Miocene
lead to the closure of the Neo-Tethys sea and the uplift of the
Zagros collisional wedge (Pirouz et al. 2017). In the Middle
Miocene, the northern part of the Arabian Peninsula became
exposed, marking the birth of the Mediterranean Sea. This
would dry up almost completely at the end of the Miocene
(the Messinian crisis) for a few hundred thousand years, due
to an upheaval in the Betic zone (Gibraltar region) combined
with a slight decrease in sea level. During the late Miocene,
the northward drift of Australia initiated the closure of the
Indonesian seaway, while the closure of the Central American Seaway linked to a tectonic uprising permanently isolated the Atlantic and Pacific waters.
Box: Focus on the uplift of the Tibetan Plateau.
Since 50 Ma, the average convergence speed between
India and Asia has remained around 5 cm per year.
The Himalayan range occurred due to the deformation
of the northern edge of the Indian sub-continent when
it was subducted under the Asian continent. To the
south of the Tsangpo suture is the Himalayan domain:
on Indian crust with remnants of the Tethyan sedimentary cover and accretion prism associated with
subduction of the Tethyan Ocean before collision.
North of the suture, the Tibetan plateau has sedimentary layers from the Asian paleomargin. These are two
very different realms with different Cenozoic geological histories, although related to the same event.
During the millions of years after the collision, a
proto-Himalayan chain must have developed on the
remains of the Andean chain associated with the
subduction of the Tethys, but the extent of this is not
known. The Tibetan plateau was still a low-lying area.
Two contrasting opinions have been proposed to
explain the uplift of the Tibetan plateau: a “soft Tibet”
model and a “staggered model”. The “soft Tibet”
model considers the uplift to be the result of an isostatic rebound caused by the “sinking” of the crustal
root of a thickened Tibetan proto-plateau. The plateau
reached its stable altitude of about 5000 m, and began
to creep, as evidenced by the normal faults that line the
southern plateau. The other theory (Tapponnier et al.
2001) considers, on the contrary, that the uplift took
place in successive stages. Part of the India-Asia collision is absorbed by the lateral extrusion of landmasses (South China, Indochina), which caused old
sutures inherited from the accretion of small landmasses during the Paleozoic and Mesozoic to protrude, profoundly modifying the paleogeography of
South-East Asia (resulting in the closure of the
Indonesian passage). These large strike-slip faults,
separating the landmasses, connect with small perpendicular faults parallel to each other. The associated
reliefs isolate small endorheic sedimentary basins
which gradually fill up with the output from the dismantling of the chain “like a bathtub”. The uplift of
the Tibetan plateau would have occurred in successive
stages since 50 Ma. The southern part of the Tibetan
plateau rose during the Eocene, the central part during
the Oligocene-Miocene and the northeastern part is
currently uplifting.
Conclusion
The Earth moved from being entirely composed of an
oceanic crust to the emergence of the first shreds of continental crust during the Archean, then to its episodic growth,
mainly during the Precambrian. The paleogeography of this
period is uncertain, given the small number of paleomagnetic data available, but it seems that the first consolidation
of landmasses into a supercontinent (followed by a break-up
phase) dates back to that time. It is only from the end of the
Precambrian that we have global paleogeographic reconstructions, but there are no unique and definitive solutions
for much of the Paleozoic, as uncertainties remain on the
arrangement of some continents and the dimensions of the
oceans. Paleogeographic reconstructions become more reliable at the end of the Paleozoic, and data from ocean kinematics makes it possible to constrain the relative positions of
some continents relative to others. The distribution of the
continents, either as they grouped together or dispersed,
represents an important climate forcing through direct and
2 The Changing Face of the Earth Throughout the Ages
45