AN INTEGRATED GEOCHEMICAL AND FACIES ANALYSIS OF ...Figure 1. Location map of Petrockstow, Bovey and...
1
Figure 1. Location map of Petrockstow, Bovey and Lough Neagh pull apart basins in its regional settings (Modified from Martyn, 2006) Figure 2. Geologic map of Bovey Basin (Modified from Freshney et al.,1979) Figure 3. Geologic map of Petrockstow Basin showing the position of Borehole 1 (Modified from Freshney et al., 1979) References Collinson, M. E. et al (2009),Grana, 48; 38-66. Edwards, R. (1976), Proceedings of the Geologists Association 87, 1 - 26. Freshney, E. C. et al. (1979), Memoir Geological Survey Great Britain (Sheet 309). Martyn, F. Q. (2006), Scottish Journal of Geology, 42, 20, 101 - 112. Selwood et al. (1984), Memoir British Geological Survey (Sheet 339). Conclusion 1. Our new sedimentary facies model involves: Firstly Sand filled fluvial channels, secondly a lake with ready supply of organic debris, and thirdly a lake prone to drying out. 2. The dominant palynomorphs identified are Inaperturopollenites, Laevigatisporites, Monocolpopollenites, Bissacate, Tiliaepollenites and Cicatrisisporites 3. Inaperturopollenites is similar to the modern conifer Taxodium which is associated with warm and wet conditions. Monocolpopollenites is a palm pollen which with other micro-floral evidence and compared to distribution maps of modern flora, suggests frost free climate. 4. MBT/CBT data shows a consistent palaeotemperature of 11 - 18 in Petrockstow 1A core though, two data points gave 25 - 27 5 o C o C . The age model for these sediments proposed by Turner (1979) in Freshney et al. (1979) and Selwood et al. (1984) is difficult to prove using pollen and/chemostratigraphic evidence collected Introduction The Petrockstow and Bovey Basins are two similar pull apart (strike slip) basins belonging to the Sticklepath-Lustleigh Fault Zone (SLFZ) in Devon (Figs. 1 & 2), SW England. The SLZF is one of the several faults on the Cornubian Peninsula and may be linked to Variscan structures rejuvenated in Palaeogene times. The bulk of the basins’ fill consists of clays, silts, lignites and sands of Palaeogene age, comparable to the Lough Neagh Basin (Northern Ireland), which is also thought to be part of the SLFZ. The basin-fills therefore, may provide rare potentially expanded sections through the Palaeocene Eocene Thermal Maximum (PETM), and the Eocene-Oligocene (Oi-1) cooling event in the UK. Facies analysis was undertaken on the sediments of the Petrockstow and Bovey Basins in order to provide a tectonic and palaeoenvironmental context for palaeoclimatic reconstructions using palynology, orgainic geochemistry (Methylation Branched Tetraether/Cyclisation Branched Tetraethers) and carbon isotope analyses. 1. High resolution palaeotemperature reconstruction using MBT/CBT proxy will continue into Petrockstow 1B 2. Biostratigraphic/palynolgical analysis to identify if flora changes are similar to that seen in the Cobham Lignite bed in the south-eastern UK which is the only PETM that has been established in the UK. Future Work Results 055 Key Laminated Silts Cross bedding Clay Lignite Fossil wood Lignite fragments > 30cm Sample Points/Number Apprx. Geol. Boundary Large Organic debris < 20cm Abundant fairly disseminated Lignites Lens of medium Coarse Quartz Sand in Clay matrix Clay clasts > 10 cm Lenses of Lignite within facies 1d Mottling of Clay Pink & Purple Mottling Palaeosol?? Coal Flakes >10cm + Coalified roots In-situ Plants >10cm dia. F. T - Facies type C - Clay S - Sand F.S - Fine Sand M.S - Medium Grain Sand C.S - Coarse Grain Sand G - Gravels P - Pebbles Co - Cobbles Figure 4: Palynomorph profiles from the Bovey Formation in Petrockstow 1A and 1B. A stratigraphic section of the formation appears to the left Figure 5: Palynofacies profile of 6 kerogen types of organic matter from the upper Bovey Formation, Bovey basin. A sedimentary log of the section appears to the left. -28.0 -27.0 -26.0 -25.0 -24.0 -23.0-22.0 Lappathorn Member and Abbrook Clay-and-Sand Member South Acre Clay-and-Lignite Member Upper Bovey Formation ? e a e 1 0 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 a f a d a c a d a c a c a a a c a b f a a 28 001 002 003 004 005 006 007 008 009 010 011 012 013 014 015 016 017 018 019 020 021 022 024 025 023 027 026 028 029 030 031 032 033 - 034 48 47 46 45 44 43 41 40 39 38 37 36 35 34 33 32 31 30 29 42 a c a g c a c g c a c g c a a a g a c c g c a g g c a c g a g c a c g c g a c g g g c c a c a g a c a c a c g a g c a c 066 065 064 067 068 069 070 063 062 061 060 058; 057 059 056 055 054 053 052 051 050 049 048 046 047 045 044 043 042 041 040 036 037 038 039 035 g c g g c a c C S F. S M. S C. S G P Co F. T Depth (m) 0 20 40 60 Amorph (%) Phyt-Brown (%) Palyno (%) Phyt-Blk (%) Fungi (%) 0 20 40 60 0 20 40 60 (%) (%) (%) (%) (%) (%) Trans (%) 0 20 40 60 80 100 0 20 40 60 80 100 0 20 0 5 10 15 20 25 30 0 5 10 15 20 25 30 o MAAT ( C) Palynofacies 13 δ C TOC Palynomorphs Pollen count Pollen count Pollen count Pollen count Pollen count Pollen count Pollen count Pollen count Pollen count Pollen count Pollen count Pollen count Pollen count 1A 1B o MAAT ( C) using MBT/CBT 13 δ C TOC 7.62 c c c b b b b b b b g c c c c b c f b b c c c c c h f c b c b g f b c c f c c c c d d b d g b e d d d d g d d d c b c c c c c b e b b b f h d d e 429 400 350 300 250 200 150 100 50 10 CARBONIFEROUS BASEMENT F. T Depth C S F. S M. S C. S G P Co d d d d b c b d d b d b d b c b b a a c 430 450 500 550 600 662 650 -30.0 -29.0 -28.0 -27.0 -26.0 -25.0 -24.0 -23.0 10 15 20 25 30 T i l i a e p o l l e n i t e s T r i c o l p o r o p o l l e n i t e s T r i l e t s T r i c o l p a t e I n a p e r t u r o p o l l e n i t e s A r e c i p i t e s F u n g i P l i c a p o l l i s P o m p e c k j o i d a e p o l l e n i t e s S a l i x p o l l e n i t e s G r a m i n i d i t e s S e q u o i a p o l l e n i t e s S t e r e i s p o r i t e s C i c a t r i c o s i s p o r i t e s 0 20 40 60 80 100 120 140 160 180 200 L a e v i g a t i s p o r i t e s 0 20 40 60 80 t 0 20 40 60 80 0 20 40 60 0 20 40 60 0 20 40 60 0 20 40 0 20 0 20 0 20 0 0 0 0 0 M o n o c o l p o p o l l e n i t e s 40 60 80 100 20 B i s s a c c a t e 0 20 40 60 80 100 0 120 AN INTEGRATED GEOCHEMICAL AND FACIES ANALYSIS OF PALAEOGENE FLUVIO-LACUSTRINE SEDIMENTS IN THE PETROCKSTOW AND BOVEY BASINS, UK Mohammed S. Chaanda (1), Rhodri M. Jerrett (2), Stephen T. Grimes (1), Gregory D. Price (1) and Mark Anderson (1) (1) Centre for Research in Earth Sciences, Plymouth University, Drake Circus, PL48AA, Devon, UK. (2) School of Atmospheric, Earth and Environmental Sciences, University of Manchester, M139PL, UK. e-mail: [email protected] Inaperturopollenites Laevigatisporites Sequoaipollenites Cicatricosisporites Sp 500 500 0 500 1000 yards m 0 500 1000 BH 1 Stratigraphical junction Bovey Formation (Palaeogene) Carboniferous Faults Railway South Western Shelf South Eastern Shelf North Eastern Shelf AXIAL THROUGH Wooladon Borehole drilled for the Institute of Geological Sciences BH 1 N 2 51 1 13 1 12 1 11 1 10 1 09 1 08 2 52 2 53 2 54 Dunsbeare River Mere A35 Merton Petrockstow LNPB Dalkey Fault Coding Fault Lambay Fault SLFZ ext + + + + + + + + + + + + + + + + + + + + + 0 50 Km 0 10Km Petrockstow pull apart Basin Petrockstow pull apart Basin Sticklepath Lustleigh Fault Zone Bovey pull apart Basin N Bristish Channel Basin Lundy pull-apart basin 6°W 3°W 52°N 45°N ENGLAND SCOTLAND IRELAND WALES East Irish Sea Basin East Irish Sea Basin Central Irish Sea Basin North Celtic Sea Basin South Celtic Sea Basin Cardigan Bay Basin Kish Bank Basin South Upland Fault Scottish Midland Valley Highland Boundary Fault Ballymoney pull- apart Basin Ulster Basin LNPB St. George’s Channel Basin Variscan Front Thrust Cenozoic Lough Neagh pull-apart basin (LNPB) Bann Fault Newry Fault Markerhill Fault Camlough Fault SGC CC MMC Site of Cenozoic pull-apart basin Extents of pull-apart basin Sliev Gullions Complex Mourne Mountains Complex Carlingford Complex SGC MMC CC N Bovey pull apart Basin Fig.3 Fig.2
Transcript of AN INTEGRATED GEOCHEMICAL AND FACIES ANALYSIS OF ...Figure 1. Location map of Petrockstow, Bovey and...
Figure 1. Location map of Petrockstow,Bovey and Lough Neagh pull apart basins in itsregional settings (Modified from Martyn, 2006)
Figure 2. Geologic map of Bovey Basin (Modified from Freshney et al.,1979)
Figure 3. Geologic map of Petrockstow Basin showing the position of Borehole 1 (Modified from Freshney et al., 1979)
ReferencesCollinson, M. E. et al (2009),Grana, 48; 38-66.
Edwards, R. (1976), Proceedings of the Geologists Association 87, 1 - 26.
Freshney, E. C. et al. (1979), Memoir Geological Survey Great Britain (Sheet 309).
Martyn, F. Q. (2006), Scottish Journal of Geology, 42, 20, 101 - 112.
Selwood et al. (1984), Memoir British Geological Survey (Sheet 339).
Conclusion1. Our new sedimentary facies model involves: Firstly Sand filled fluvial channels, secondly a lake with ready supply of organic debris, and thirdly a lake prone to drying out.
2. The dominant palynomorphs identified are Inaperturopollenites, Laevigatisporites, Monocolpopollenites, Bissacate, Tiliaepollenites and Cicatrisisporites
3. Inaperturopollenites is similar to the modern conifer Taxodium which is associated with warm and wet conditions. Monocolpopollenites is a palm pollen which with other micro-floral
evidence and compared to distribution maps of modern flora, suggests frost free climate.
4. MBT/CBT data shows a consistent palaeotemperature of 11 - 18 in Petrockstow 1A core though, two data points gave 25 - 27
5
oC
oC
. The age model for these sediments proposed by Turner (1979) in Freshney et al. (1979) and Selwood et al. (1984) is difficult to prove using pollen and/chemostratigraphic evidence collected
IntroductionThe Petrockstow and Bovey Basins are two similar pull apart (strike slip) basins belonging to the Sticklepath-Lustleigh Fault Zone (SLFZ) in Devon (Figs. 1 & 2), SW England. The SLZF is one
of the several faults on the Cornubian Peninsula and may be linked to Variscan structures rejuvenated in Palaeogene times. The bulk of the basins’ fill consists of clays, silts, lignites and sands
of Palaeogene age, comparable to the Lough Neagh Basin (Northern Ireland), which is also thought to be part of the SLFZ. The basin-fills therefore, may provide rare potentially expanded
sections through the Palaeocene Eocene Thermal Maximum (PETM), and the Eocene-Oligocene (Oi-1) cooling event in the UK. Facies analysis was undertaken on the sediments of the
Petrockstow and Bovey Basins in order to provide a tectonic and palaeoenvironmental context for palaeoclimatic reconstructions using palynology, orgainic geochemistry (Methylation
Branched Tetraether/Cyclisation Branched Tetraethers) and carbon isotope analyses.
1. High resolution palaeotemperature reconstruction using MBT/CBT proxy will continue into Petrockstow 1B
2. Biostratigraphic/palynolgical analysis to identify if flora changes are similar to that seen in the Cobham Lignite
bed in the south-eastern UK which is the only PETM that has been established in the UK.
Future Work
Results
055
Key
Laminated SiltsCross bedding
ClayLignite
Fossil wood
Lignite fragments > 30cm
Sample Points/Number
Apprx. Geol. Boundary
Large Organic debris < 20cmAbundant fairly disseminatedLignites
Lens of medium Coarse QuartzSand in Clay matrixClay clasts > 10 cm
Lenses of Lignite within facies 1d
Mottling of Clay
Pink & Purple MottlingPalaeosol??
Coal Flakes >10cm+ Coalified roots
In-situ Plants >10cm dia.
2b
F. T - Facies typeC - ClayS - SandF.S - Fine SandM.S - Medium Grain SandC.S - Coarse Grain SandG - GravelsP - PebblesCo - Cobbles
Figure 4: Palynomorph profiles from the Bovey Formation in Petrockstow 1A and 1B. A stratigraphic section of the formation appears to the left
Figure 5: Palynofacies profile of 6 kerogen types of organic matter from the upper Bovey Formation, Bovey basin. A sedimentary log of the section appears to the left.
-28.0 -27.0 -26.0 -25.0 -24.0 -23.0-22.0
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C S F. S
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G P Co
F. T
Depth
(m
)
0 20 40 60
Amor
ph (%
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Phyt-B
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Fungi (%
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(%) (%) (%) (%) (%) (%)
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0 5 10 15 20 25 30
oMAAT ( C)
Palynofacies
13δ C TOC
Palynomorphs
Pollen count Pollen count Pollen count Pollen count Pollen count Pollen count Pollen count Pollen count Pollen count Pollen count Pollen count Pollen count Pollen count
1A
1B
oMAAT ( C) using MBT/CBT13
δ C TOC
7.62 c
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CARBONIFEROUS BASEMENT
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T
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poro
polle
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s
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t
0 20 40 60 80 0 20 40 60 0 20 40 60 0 20 40 60 0 20 40 0 20 0 20 0 20 0 0 0 0 0
Mono
colpo
pollen
ites
40 60 80 10020
Bissacc
ate
0 20 40 60 80 100 0120
AN INTEGRATED GEOCHEMICAL AND FACIES ANALYSIS OF PALAEOGENE FLUVIO-LACUSTRINE SEDIMENTS IN THE PETROCKSTOW AND BOVEY BASINS, UK
Mohammed S. Chaanda (1), Rhodri M. Jerrett (2), Stephen T. Grimes (1), Gregory D. Price (1) and Mark Anderson (1)(1) Centre for Research in Earth Sciences, Plymouth University, Drake Circus, PL48AA, Devon, UK.
(2) School of Atmospheric, Earth and Environmental Sciences, University of Manchester, M139PL, UK.e-mail: [email protected]
Inaperturopollenites
Laevigatisporites
Sequoaipollenites
Cicatricosisporites Sp
500
500 0 500 1000yards
m0 500 1000
BH 1
Stratigraphical junction
Bovey Formation(Palaeogene)
Carboniferous
Faults
Railway
South Western Shelf
South
East
ern
Shelf
North Eastern Shelf
AXIAL THROUGH
Wooladon
Borehole drilled for the Institute of Geological Sciences
BH 1
N2 51
1 13
1 12
1 11
1 10
1 09
1 08
2 52 2 53 2 54Dunsbeare
River
Mer
e
A35
Merton
Petrockstow
LN
PB
Dal
key
Fau
lt
Co
din
g F
au
lt
Lambay Fault
SLFZ ext
+
+
++
++
++
+++
++
+
++++
+
+
+
0 50 Km
0 10Km
Petrockstow pullapart Basin
Petrockstow pullapart Basin
Sticklepath Lustleigh Fault Zone
Bovey pullapart Basin
N
Bristish ChannelBasin
Lundy pull-apartbasin
6°W 3°W
52°N
45°N
ENGLAND
SCOTLAND
IRELAND
WALES
East IrishSea BasinEast IrishSea Basin
Central IrishSea Basin
North CelticSea Basin
South CelticSea Basin
CardiganBay Basin
Kish Bank Basin
South U
pland F
ault
Scotti
sh M
idla
nd
Val
ley
Hig
hland B
oundary
Fault
Ballymoney pull-apart Basin
Ulster Basin
LNPB
St. G
eorg
e’s
Chan
nel
Bas
in
Variscan Front Thrust
Cenozoic Lough Neaghpull-apart basin (LNPB)
Bann Fault
Newry Fault
Markerhill Fault
Camlough Fault
SGCCC
MMC
Site of Cenozoic pull-apart basin
Extents of pull-apart basin
Sliev Gullions Complex
Mourne Mountains Complex
Carlingford Complex
SGC
MMC
CC
N
Bovey pullapart Basin
Fig.3
Fig.2
