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4.1 Plio-Quat of West Cyprus (Sealevel change (Extension in chalk…
4.1
Plio-Quat of West Cyprus
Sealevel change
Chalk ~ 20 Ma
= Underlying U. Lefkhara basement
∴ immense time gap btwn chalk & quaternary above
Extension in chalk
Extension assoc w Polis Graben opening (trend?)
Pulled open cracks into which sediment fills
Evidence: neptunian dykes & normal faults
Transgression (SL ↑) erodes marl
Unconformity surface
Reworking/lag deposit of older
terrace material & basement (Mammonia Complex)
Sealevel highstand: Coralline algae rhodoliths
Regression: Migrating dune envmt
Aelionite - non marine sand dunes when land exposed
Palaeosol: Warm, humid terrestrial
Agios Gorgios Chapel
Coralline algae
Shallow - deep conditions (Water Z ≈ 2-40 m)
Sequence
Chalk
Deep water envmt
TRANSGRESSION
erosional u/c & conglom lag
Rhodolith
(Coralline algae)
High energy beach, shallow marine
SL highstand
REGRESSION
Calcarenite
(aeolianite)
Migrating dunes
- Large-scale crossbeds
(Bioclastic sandstone)
Non-marine dunes migrate as island uplifts
Palaeosol
Terra rossa
from warm, humid terrestrial envmt
U/C @ base
∴ immense time gap btwn chalk & quaternary above
Underlying basement, chalk = upper lefkhara ( > 20 Ma )
Uncertain how much sed lost
Lithologies
Chalk (lefkhara)
Conglomerate lag
pebbles @ base of rhodolith
record erosive change to high energy beach envmt as sealevel rises
Rhodolith
= Coralline mound
Algae grow around detrital grain on high energy seafloor
'Rhodolith balls' coalesce to form mounds
Interp: high energy, shallow marine envmt
Aeolian calcarenite
Shoreline was exposed to form dune system
Bioclastic sstone w large scale crossbeds
Interp
Forearc envmt atop downgoing plate
UPLIFT RATE SLOWED
Cemented Dunes
Paphos
Aeolianite
Coarse sand, rich in bioclasts
Strong cross bedding oriented SE
Rootlets
vertical wiggly hollows remain
extend few metres into rock
Well cemented
Burrows
stubby hollows
Palaeo reconstruction
Palaeowind blew E
Strong Westerlies needed to carry coarse grains
Wind speed =
f (temp gradient)
Glacial so cold - polar front extended to Med
Jet stream deflected S provided W component
How Med cooled?
Inflow Atlantic Water to Med
Battle btwn Arctic & African air masses
Arctic won @ this time
∴Dunes migrate over shoreline
Where aeolianite source?
Reworked carbonate material (shore/offshore)
Coastal submarine sand = exposed
No beachrock
∴ Must have been transported by wind rapidly after exposure
Forest growing atop
Root evinces
Climate ameliorated soon after
Base of lowest terrace
Base of last terrace = just above present sealevel
Shortlived terrace level
only produced thin marine layer & aeolianite
Lower uplift rate
Most recent terrace essentially overlies older terraces
∴ small vert displacement btwn youngest 2 terraces
Why marine material?
Nr the Troodos (elsewhere)
Material coming off Troodos = funnelled into Polis Graben
Whereas here (SW Cyprus)
Region = starved of terrigenous sediment
∴ Terraces dominated by marine material