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2.1 Troodos Cover (N) Kottaphi Hill (Interp (Sed rate slows (much more…
2.1 Troodos Cover (N) Kottaphi Hill
Kottaphi Hill
Emergence of Troodos saw carbonate buildups develop atop the chalk
Oligocene
= missing
Carbonate sequence v condensed (only ~10 m)
18.9 Ma - 7.5 Ma (Burdigalian-Tortonian)
Hiatus btwn Eocene chert & Miocene carbonates
Later hiatus ~ 1.5 Ma (no sed)
Getting older:
Carbonates (Miocene)
Break (Oligocene missing)
Chert (Eocene)
Pillow lavas
Why condensed sequence ?
Characteristic of high in basin (deepening basin)
Orange rocks indicate
high continental weathering rates
low continental sed input
Mn/Fe enrichment
possible when low sedimentation rate - Fe settles out
whereas high sed would dilute Fe
Starved of continental sediment input
∴ condensed pelagics accumulate slowly
Troodos Cover N Side
Upward progression through condensed Mio-Quat cover
Represents relative uplift & emergence of Troodos ophiolite
Sediments characterised by:
Miocene
Patch reefs & assoc off-reef facies
U. Miocene
Gypsum
Pliocene
Extensional Mesaoria Basin develops North of Troodos
As basin fills & Troodos uplifts
Channelised bioclastic sands --> Fan deltas --> Fluvial conglomerates
Cover on N side = thinner than S side
1.1
Eocene
Chert
Fragmented, poor bedding
Planktic forams =
abundant
Shallowing assemblage
Fully pelagic
at bottom of hill, pelagic forams
Increasing benthics
Moving up section, more benthics
Precessional cycling btwn marl & chalk
Sapropel
Coarser marl
Bioturbd/ nod chalk
Precess cycle marl & chert
Pelagic chert
1.2.
Marl-Chalk Cycling
Precessional (100ka) cycles may reflect
Glacial eustatic sealevel ∆ --> different temps/runoff
Continental weathering variability
Alternates btwn thinner muddy & thicker chalky horizons
Interpretation
Muddy horizons
Higher runoff from land ?
Lower productivity
Terrigenous mud input = more abundant
Chalky horizons
Higher productivity - nanofossil forams
Thicker - high nutrients
Rhythmic layering on 100 ka cycle results from ∆ in sedimentation
Marl
= CaCO3
rich mudstone
1.3
Bioturbated/ nodular chalk
Abundant bioturbation
Preservation - suggests prolonged stable seafloor conditions
Reduced sed rate
can lead to ↑ burrowing intensity
Zoophycos - spiral, Chonolites - small, delicate
Pink marl fills in cavities in lumpy surface beneath
Mn deposits
Black pits/specks / layers = Mn precipitate ('pyrolusite')
Layers - likely came from land in solution (cont weathering)
Hardground
Hard, lumpy & bumpy surface, bored in placed
Forms slightly beneath seafloor
Suggests hiatus in sedimentation
Poss reason sed hiatus
Tectonic uplift
Sealevel drop
Test - isotopic analysis
do local signals align w global SL records?
Upseq Change
Normal chalk
Bioturbated chalk
Nodular chalk
evinces hard, lumpy surface on seafloor
Red marl
fills in cavities in lumpy surface beneath
Deeper > reducing envmt
Sapropel
Shallower
Higher terrestrial runoff --> anoxia
Interp
Deep shelf envmt
Sealevel drop likely
Sed rate slows
much more oxygenated
lotsa burrowing & trace fossils
Sed & Mn precip
cont runoff ↑?
Some seds lithified & bored/encrusted
hard ground, high prod
Deepening conditions?
switch to red marl - more reducing
orbulinas = pelagic foram (football shaped)
1.4
Sapropel
Heavily bioturbated
Forams abundant
Muddier/browner
more terrigenous input
Horiz burrows
first conclusive evidence shallowing
Oxidised red
1.4
Sapropel Interp
Sapropels - mid Miocene - Recent
Reps onset of Milankovitch cycles, w alternation btwn
Nile flow dominates Med (sapropel)
Normal circulation (muddy)
Wetter climate
Freshwater low salinity cap forms atop Med
∴ Circulation ceased, causing water column stratification
Deoxygenation @ depth ∴ organics preserved on seafloor