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3.1 Troodos Cover: S Side (Palaeocene Calcturbidites (Turbidite packages,…
3.1
Troodos Cover: S Side
Palaeocene Calcturbidites
Lefkhara Fm.
- Chalks & Cherts nr Pano Lefkhara
2 types chert:
Qtz chert
forms by dissolution & reprecip opal-CT
grey/black
Opal-CT
forms earlier
Buff, greenish/cream
Qtz chert silica > opal ct
Bedded replacement chert
remnant 1° background chalk
chert nodules
w pockets of:
Turbidite packages
Erosive base
Dark chert band - Green/grey waxy
Fining upwards
Pelagic fallout
Coarse opal CT
Interp
Lack of fossils - distal deposition ?
Opal CT
Reprecip chert
forms in coarse, compacted bottom layer turbidite
Quartzose chert
forms in upper portion of coarse
Eocene Interp
High silica
Abundant chert/radiolaria in rocks
Congruent w globally high SiO2
Whereas Oligo/Miocene = carb-dominated
High productivity
suggesting high nutrient levels
Fluids very SiO2 saturated
Suggests this was below CCD ?
Deep abyssal depths potentially ~4 km ?
Rapid infill by turbidite buries & protects carbonates
Where material sourced from?
Upper slope in N basin
Lekfhara Chalks divided in 3
Lower Lefkhara
Ponded in depressions btwn pillow lavas
Middle lefkhara
Calcturbidites
Laterally continuous chalk & chert
Upper Lekhara
Poorly bedded irregularly deposited replacement cherts
Calcturbidites
Lie SE side Troodos
Not full bouma
Driver
Tectonic shocks assoc w uplift
Deposited in deepwater envmt
Palaeoflow agrees w S downbuckling of Troodos
Why SiO2 pools in coarser layers
Finer grained
more impurities blocking cation expulsion
hence why nodules etc. expel impurities so chert can be concentrated
Coarser, more porous
More cations exposed
∴ more SiO2 can be accrued
Silica
in chert
forms by dissolution of radiolarian
some sourced from volcanoes
Lekhara Chalks