Cratonic keels and a 2-layer mantle tested: Miles Osmaston Mantle expulsion during Arabia-Russia...

Cratonic keels and a 2-layer mantle tested:

Miles Osmaston

Mantle expulsion during Arabia-Russia closure linked to

westward enlargement of the Black Sea, formation of the Western Alps and

subduction of the Tyrrhenian (not the Ionian) Sea

Osmaston 2006

First: What happens when cratons separate?

The Greenland- Eureka folding

The early Arctic ocean was nearly surrounded by

cratons, so the flow of mantle to put under the opening Eurasia Basin ‘dragged’

Greenland’s keel northward in the Eocene, causing major folding across it’s northern

neighbours.

First: What happens when cratons separate – Greenland-Eureka folding

Opening of the western Black Sea

350km

Vrancea seismicity M>3.0 (Sperner et al 2001)

Vrancea seismicity and shear line?

180km

?

Moesian ‘indenter’ microcraton

mid-K closure

Vrancea

Transylvania

S.Karamata (2006) cites this as a part of the dextral shear line

after Kemenci & Canovic 1997

Beograd

Dextral shear zone N of Belgrade

The dextral link with the Alps

The link with the Alps (Burchfiel)

= Motion 1 of Adria/Italy – 200-250km to WNW - Oligocene

W Alps

from Osmaston - submitted

Final construction of the Western Alps

1

Stepfaulting mechanism of plate down-bendcauses…………

1. seismic coupling (alternate step-fault and interface slip)2. basal Subduction Tectonic Erosion (STE) - development

of flat subduction profiles

crust of upper plate

each step increment traps a sliver of upper

plate

downbend moves forward

Subducting plate down-bend

Basal subduction tectonic erosion (STE): its large scale action

Basal STE: its large-scale action

Apennines - preparation

(seen as widespread sub-CCD turbidites)

Final line of

subduction

downbend

Former extent(?) of ‘Greater Adria’

WHEN ADRIA WAS BEING STE-UNDERCUT IN CRETACEOUS but was further East at the time

Former extent of ‘Greater Adria’

trench line in

Cretaceous?

Apennines - constructionDevelopment of slab pull

Tyrrhenian downbend

basins?

Aeolian arc

After Gamberi & Marani 2006

Downfaulting

100 km

(a pseudo-trench?)

Overthrusting of Calabria-Peloritani

All have been overthrust from the direction of the Tyrrhenian Sea. This has induced strong epeirogenic response in blocks of mature continental crust, (which have not been displaced).

Episodes 2004

250km

SeismicityWortel & Spakman 2000

Jenny et al 2006

<40km

Where does >800km of slab length come from if it was Ionian?

Mainly intracrustal (thermal) epeirogenic adjustments following overthrusting

Did Tyrrhenian slab pull drive the swing of Corsica-Sardinia?

from Geological Map of Europe 1:5M, 2005

Opening of the western Black Sea - reprise

350km

1. Mantle flow expelled from between the converging Russia-Arabia cratons HAS driven the keel of Moesia westwards, and is still active (Vrancea).

2. In the Oligocene this action drove the Balkans ~200km westward. This built the Western Alps and started Apennines construction by reactivating Cretaceous subduction and triggering Tyrrhenian slab pull.

3. Since mid-Cretaceous or earlier, this action has driven or triggered E-W components of closure in Mediterranean belts.

4. N-S closure in the East was the primary agent, so N-S compression was present too.

Conclusions

Apparently these two primary

directions were indeed operative in Apennines

construction

Guisy Lavecchia 1988

So I conclude that the Earth does indeed have a 2-layer mantle

and(at least some) cratonic keels that

reach nearly to the 660.

Thank you