project funded by the b.c. dept. of energy and mines, and the geological survey of canada
DESCRIPTION
Apatite Fission Track (AFT) thermochronology of the Northern Bowser and Sustut Basins: Constraints on the Latest Cretaceous through Cenozoic thermal history. Paul O’Sullivan - Apatite to Zircon, Inc. Fil Ferri - British Columbia Dept. Energy and Mines - PowerPoint PPT PresentationTRANSCRIPT
Project funded by the B.C. Dept. of Energy and Mines,Project funded by the B.C. Dept. of Energy and Mines,and the Geological Survey of Canada and the Geological Survey of Canada
Apatite Fission Track (AFT) thermochronology of Apatite Fission Track (AFT) thermochronology of the Northern Bowser and Sustut Basins:the Northern Bowser and Sustut Basins:
Constraints on the Latest Cretaceous through Constraints on the Latest Cretaceous through Cenozoic thermal historyCenozoic thermal history
Apatite Fission Track (AFT) thermochronology of Apatite Fission Track (AFT) thermochronology of the Northern Bowser and Sustut Basins:the Northern Bowser and Sustut Basins:
Constraints on the Latest Cretaceous through Constraints on the Latest Cretaceous through Cenozoic thermal historyCenozoic thermal history
Paul O’SullivanPaul O’Sullivan - Apatite to Zircon, Inc.- Apatite to Zircon, Inc.
Fil FerriFil Ferri - British Columbia Dept. Energy and Mines- British Columbia Dept. Energy and Mines
Carol EvenchickCarol Evenchick - Geological Survey of Canada- Geological Survey of Canada
Kirk OsadetzKirk Osadetz - Geological Survey of Canada- Geological Survey of Canada
Ray DonelickRay Donelick - Apatite to Zircon, Inc.- Apatite to Zircon, Inc.
Overview of PresentationOverview of PresentationOverview of PresentationOverview of Presentation
- - Introduce some general background concerning apatite Introduce some general background concerning apatite fission track (AFT) analyses and interpretation of AFT fission track (AFT) analyses and interpretation of AFT datadata
- Introduce some regional geologic constraints within the - Introduce some regional geologic constraints within the Bowser Basin - Bowser Basin - thesethese help explain why samples were help explain why samples were originally collected for AFT analysisoriginally collected for AFT analysis
- - Present representative AFT results from study regionPresent representative AFT results from study region
- Summarize the Late Cretaceous to Tertiary thermal - Summarize the Late Cretaceous to Tertiary thermal history of the study region based on the AFT results*history of the study region based on the AFT results*
**NOTE - I will leave the geologic implications of these results to thoseNOTE - I will leave the geologic implications of these results to those
most familiar with the regional geologymost familiar with the regional geology
- - Introduce some general background concerning apatite Introduce some general background concerning apatite fission track (AFT) analyses and interpretation of AFT fission track (AFT) analyses and interpretation of AFT datadata
- Introduce some regional geologic constraints within the - Introduce some regional geologic constraints within the Bowser Basin - Bowser Basin - thesethese help explain why samples were help explain why samples were originally collected for AFT analysisoriginally collected for AFT analysis
- - Present representative AFT results from study regionPresent representative AFT results from study region
- Summarize the Late Cretaceous to Tertiary thermal - Summarize the Late Cretaceous to Tertiary thermal history of the study region based on the AFT results*history of the study region based on the AFT results*
**NOTE - I will leave the geologic implications of these results to thoseNOTE - I will leave the geologic implications of these results to those
most familiar with the regional geologymost familiar with the regional geology
ThermochronometersThermochronometersThermochronometersThermochronometersT
emp
erat
ure
(°C
)T
emp
erat
ure
(°C
)
Argon/ArgonArgon/Argon Fission TrackFission Track U/Th-HeliumU/Th-Helium
00
100100
200200
300300
400400
500500
600600
700700
800800
TopographyTopographySurface processesSurface processes
Sedimentary BasinsSedimentary BasinsBurial/Burial/
MetamorphismMetamorphism
Igneous processesIgneous processes
MetamorphismMetamorphismMid-crustalMid-crustalprocessesprocessesHornblendeHornblende
ZirconZircon
SpheneSphene
ApatiteApatite
SpheneSphene
ApatiteApatite
K-SparK-Spar
MuscoviteMuscovite
ZirconZircon
Apatite Fission-Track (AFT)ThermochronologyApatite Fission-Track (AFT)ThermochronologyApatite Fission-Track (AFT)ThermochronologyApatite Fission-Track (AFT)Thermochronology
Fission-track ageFission-track agearea density of fossil tracksarea density of fossil tracks
induced fission tracks (U conc)induced fission tracks (U conc)
Fission-track lengthsFission-track lengthsmean track lengthmean track length
distribution of lengthsdistribution of lengths
Fission-track kineticsFission-track kineticsmeasure Dpar for each grain analyzedmeasure Dpar for each grain analyzed
Fission-track ageFission-track agearea density of fossil tracksarea density of fossil tracks
induced fission tracks (U conc)induced fission tracks (U conc)
Fission-track lengthsFission-track lengthsmean track lengthmean track length
distribution of lengthsdistribution of lengths
Fission-track kineticsFission-track kineticsmeasure Dpar for each grain analyzedmeasure Dpar for each grain analyzed
Constrains maximum paleotemperatures plus timing and style of coolingConstrains maximum paleotemperatures plus timing and style of coolingfrom maximum paleotemperaturesfrom maximum paleotemperatures
Constrains maximum paleotemperatures plus timing and style of coolingConstrains maximum paleotemperatures plus timing and style of coolingfrom maximum paleotemperaturesfrom maximum paleotemperatures
“ “time” of coolingtime” of cooling “ “time” of coolingtime” of cooling
“ “rate” & “style” of coolingrate” & “style” of cooling “ “rate” & “style” of coolingrate” & “style” of cooling
1250x1250x
‘‘confined’confined’lengthslengths
‘‘confined’confined’lengthslengths
annealing “resistivity”annealing “resistivity”annealing “resistivity”annealing “resistivity”
Number of tracks provides a Number of tracks provides a measure of time over which measure of time over which
tracks have accumulatedtracks have accumulated
Both grains have same Both grains have same Uranium concentrationUranium concentration
Pretty youngPretty young
Bloody oldBloody old
Apatite Fission-Track (AFT)ThermochronologyApatite Fission-Track (AFT)Thermochronology- Fission-Track Age -- Fission-Track Age -
Apatite Fission-Track (AFT)ThermochronologyApatite Fission-Track (AFT)Thermochronology- Fission-Track Age -- Fission-Track Age -
2000x2000x
220 Ma220 Ma
Length of a track today is Length of a track today is determined by the maximum determined by the maximum paleotemperatures since that paleotemperatures since that
track formedtrack formed
Apatite Fission-Track (AFT)ThermochronologyApatite Fission-Track (AFT)Thermochronology- Fission-Track Lengths -- Fission-Track Lengths -
Apatite Fission-Track (AFT)ThermochronologyApatite Fission-Track (AFT)Thermochronology- Fission-Track Lengths -- Fission-Track Lengths -
2250x2250x
““Confined” tracksConfined” tracks
PrettyPrettycoolcool
BloodyBloodyhothot
Dpar (µm)Dpar (µm)
Apatite Fission-Track (AFT)ThermochronologyApatite Fission-Track (AFT)Thermochronology- Fission-Track Kinetics -- Fission-Track Kinetics -
Apatite Fission-Track (AFT)ThermochronologyApatite Fission-Track (AFT)Thermochronology- Fission-Track Kinetics -- Fission-Track Kinetics -
2250x2250x2000x2000x
““Confined” trackConfined” track
Etch pitEtch pit
SpontaneousSpontaneoustrackstracks
Dpar is essentially a measure of apatite solubility in a grain.Dpar is essentially a measure of apatite solubility in a grain.Solubility in apatite is related to the grain’s compositionSolubility in apatite is related to the grain’s composition
C-axisC-axis
Little variationLittle variationbetween grainsbetween grains
AFTSolve:AFTSolve: Measure kinetic variation (Dpar) Measure kinetic variation (Dpar)AFTSolve:AFTSolve: Measure kinetic variation (Dpar) Measure kinetic variation (Dpar)
Significant variationSignificant variationbetween grainsbetween grains
Dpar is essentially a measure of apatite solubility in a grain.Dpar is essentially a measure of apatite solubility in a grain.Solubility in apatite is related to the grain’s compositionSolubility in apatite is related to the grain’s composition
TotalTotalresettingresetting~100°C~100°C
TotalTotalresettingresetting~115°C~115°C~145°C~145°C~160°C~160°C
Oil
Oil
gen
erat
ion
gen
erat
ion
Wet
gas
Wet
gas
gen
erat
ion
gen
erat
ion
Potential oil generationPotential oil generation
AFTSolve:AFTSolve: Modeled Thermal History Modeled Thermal History (not reset)(not reset)AFTSolve:AFTSolve: Modeled Thermal History Modeled Thermal History (not reset)(not reset)
AFT resetAFT reset
AFT Age103±6 Ma
Onset of cooling88±4 Ma
Stratigraphic Age ~130 Ma
Oil
Oil
gen
erat
ion
gen
erat
ion
Wet
gas
Wet
gas
gen
erat
ion
gen
erat
ion
Lack of controlLack of controlprior to ~56 Maprior to ~56 Ma
AFTSolve:AFTSolve: Modeled Thermal History Modeled Thermal History (reset)(reset)AFTSolve:AFTSolve: Modeled Thermal History Modeled Thermal History (reset)(reset)
AFT resetAFT reset
real / predictedAFT Age = 53±4 Ma / 53±4 Ma
M.L. = 14.3±0.2 µm / 14.2±0.2 µmOnset of cooling = 56±5 Ma
Stratigraphic Age ~180 Ma
Bowser Basin (Skeena FB)Bowser Basin (Skeena FB)- regional stratigraphic framework -- regional stratigraphic framework -
Bowser Basin (Skeena FB)Bowser Basin (Skeena FB)- regional stratigraphic framework -- regional stratigraphic framework -
Sustut GroupSustut Groupcoarsening upward deltaic to coarsening upward deltaic to
fluvial successionfluvial succession
Bowser Lake GroupBowser Lake Groupcoarsening upward coarsening upward
deep marine to deltaic deep marine to deltaic successionsuccession
Hazelton GroupHazelton Groupvolcanic and volcanic and
volcaniclastic stratavolcaniclastic strata
Cre
tace
ou
sC
reta
ceo
us
Jura
ssic
Jura
ssic
0
1000
2000
3000
meters
~200 my
~175 my~155 my
~144 my~138 my
~75 my
Tertiary Plutonic RocksTertiary Plutonic Rocks
- Tertiary sedimentary rocks have been eroded from the Skeena Fold Belt - Tertiary sedimentary rocks have been eroded from the Skeena Fold Belt - thus the majority of the post-Cretaceous geologic record has been deleted- thus the majority of the post-Cretaceous geologic record has been deleted - requires - requires regional relationshipsregional relationships and/or and/or thermochronologythermochronology to help to help constrain geologic history since ~75 Maconstrain geologic history since ~75 Ma
At least 2 distinct episodes of folding recognized:At least 2 distinct episodes of folding recognized:- BLG rocks folded pre-Sustat Basin deposition - BLG rocks folded pre-Sustat Basin deposition - older folding <150 Ma and >95 Ma- older folding <150 Ma and >95 Ma- Sustat Basin rocks themselves are folded - Sustat Basin rocks themselves are folded - so younger episode of folding <75 Ma- so younger episode of folding <75 Ma- Folds in Sustat Basin rocks truncated a by 53 Ma pluton - Folds in Sustat Basin rocks truncated a by 53 Ma pluton - folds are >53 Ma- folds are >53 Ma
Coast PlutonicCoast PlutonicBeltBelt
North American CratonNorth American Craton
StikiniaStikinia
EEWW Intermontane BeltIntermontane BeltSkeena Fold BeltSkeena Fold Belt
Bowser BasinBowser Basin SustatSustatBasinBasin
Omineca BeltOmineca BeltRocky MountainRocky Mountain
Fold & Thrust BeltFold & Thrust Belt
Subducting Farallon/Kula plateSubducting Farallon/Kula platebeneath the Coast Complexbeneath the Coast Complex
Bowser Basin (Skeena FB)Bowser Basin (Skeena FB)1) regional relationships1) regional relationships
Bowser Basin (Skeena FB)Bowser Basin (Skeena FB)1) regional relationships1) regional relationships
- Diving force for deformation within the basin related to subduction of Pacific plates- Diving force for deformation within the basin related to subduction of Pacific plates beneath North American Cratonbeneath North American Craton- Skeena Fold Belt has experienced ~50% horizontal shortening - Skeena Fold Belt has experienced ~50% horizontal shortening (initially >360 km wide)(initially >360 km wide)
Coast PlutonicCoast PlutonicBeltBelt
North American CratonNorth American Craton
StikiniaStikinia
EEWW Intermontane BeltIntermontane BeltSkeena Fold BeltSkeena Fold Belt
Bowser BasinBowser Basin SustatSustatBasinBasin
Omineca BeltOmineca BeltRocky MountainRocky Mountain
Fold & Thrust BeltFold & Thrust Belt
Subducting Farallon/Kula plateSubducting Farallon/Kula platebeneath the Coast Complexbeneath the Coast Complex
Rapid cooling at Rapid cooling at some time between:some time between:
~100-80 Ma~100-80 Ma~65-60 Ma~65-60 Ma~45-35 Ma~45-35 Ma~10-8 Ma~10-8 Ma
Rapid cooling at Rapid cooling at some time between:some time between:
~100-80 Ma~100-80 Ma~65-60 Ma~65-60 Ma~45-35 Ma~45-35 Ma~10-8 Ma~10-8 Ma
Rapid cooling at Rapid cooling at some time between:some time between:
~65-60 Ma~65-60 Ma~45-40 Ma~45-40 Ma
Rapid cooling at Rapid cooling at some time between:some time between:
~65-60 Ma~65-60 Ma~45-40 Ma~45-40 Ma
Rapid cooling at Rapid cooling at some time between:some time between:
~65-60 Ma~65-60 Ma~45-40 Ma~45-40 Ma
Rapid cooling at Rapid cooling at some time between:some time between:
~65-60 Ma~65-60 Ma~45-40 Ma~45-40 Ma
Bowser Basin (Skeena FB)Bowser Basin (Skeena FB)2) regional AFT results2) regional AFT results
Bowser Basin (Skeena FB)Bowser Basin (Skeena FB)2) regional AFT results2) regional AFT results
????
AFT SamplesAFT SamplesAFT SamplesAFT Samples
- locations - - locations -
On GSC ThermalOn GSC Thermal
Maturity Base*Maturity Base*
- locations - - locations -
On GSC ThermalOn GSC Thermal
Maturity Base*Maturity Base*
** GSC Report 4343 GSC Report 4343
Evenchick et al. (2002)Evenchick et al. (2002)
1) Triangle Zone &1) Triangle Zone & Upper Sustut BasinUpper Sustut Basin2) Groundhog coalfield2) Groundhog coalfield3) Mount Ritchie3) Mount Ritchie
1) Triangle Zone &1) Triangle Zone & Upper Sustut BasinUpper Sustut Basin2) Groundhog coalfield2) Groundhog coalfield3) Mount Ritchie3) Mount Ritchie
Triangle Zone /Triangle Zone / Upper SustutUpper SustutTriangle Zone /Triangle Zone / Upper SustutUpper Sustut
BLGBLG
BPFBPF
BLGBLG
AFT AgeAFT Age
59±3 Ma59±3 MaOnset of Onset of CoolingCooling
62±3 Ma62±3 Ma
AFT AgeAFT Age
59±3 Ma59±3 MaOnset of Onset of CoolingCooling
62±3 Ma62±3 Ma
AFT AgeAFT Age
40±4 Ma40±4 MaOnset of Onset of CoolingCooling
46±4 Ma46±4 Ma
AFT AgeAFT Age
40±4 Ma40±4 MaOnset of Onset of CoolingCooling
46±4 Ma46±4 Ma
AFT AgeAFT Age
40±3 Ma40±3 MaOnset of Onset of CoolingCooling
44±3 Ma44±3 Ma
AFT AgeAFT Age
40±3 Ma40±3 MaOnset of Onset of CoolingCooling
44±3 Ma44±3 Ma
- Significant Eocene cooling- Significant Eocene cooling- Note recent cooling- Note recent cooling
PaleocenePaleocenecoolingcooling
Triangle Zone /Triangle Zone / Upper SustutUpper SustutTriangle Zone /Triangle Zone / Upper SustutUpper Sustut
NotNotallall
resetreset
GroundhogGroundhogGroundhogGroundhog
BLGBLG
BLGBLG
BLGBLG
GroundhogGroundhogGroundhogGroundhogAFT AgeAFT Age
49±4 Ma49±4 MaOnset of Onset of CoolingCooling
59±4 Ma59±4 Ma
AFT AgeAFT Age
49±4 Ma49±4 MaOnset of Onset of CoolingCooling
59±4 Ma59±4 Ma
AFT AgeAFT Age
35±2 Ma35±2 MaOnset of Onset of CoolingCooling
44±4 Ma44±4 Ma
AFT AgeAFT Age
35±2 Ma35±2 MaOnset of Onset of CoolingCooling
44±4 Ma44±4 Ma
AFT AgeAFT Age
45±3 Ma45±3 MaOnset of Onset of CoolingCooling
48±4 Ma48±4 Ma
AFT AgeAFT Age
45±3 Ma45±3 MaOnset of Onset of CoolingCooling
48±4 Ma48±4 Ma
- Significant Eocene cooling- Significant Eocene cooling- Note recent cooling- Note recent cooling
Mt. RitchieMt. RitchieMt. RitchieMt. Ritchie
BLGBLG
BLGBLG
a-3-Ja-3-J
BLGBLG
Mt. RitchieMt. RitchieMt. RitchieMt. Ritchie
a-3-Ja-3-J
AFT AgeAFT Age
38±3 Ma38±3 MaOnset of Onset of CoolingCooling
41±3 Ma41±3 Ma
AFT AgeAFT Age
38±3 Ma38±3 MaOnset of Onset of CoolingCooling
41±3 Ma41±3 Ma
AFT AgeAFT Age
41±5 Ma41±5 MaOnset of Onset of CoolingCooling
43±4 Ma43±4 Ma
AFT AgeAFT Age
41±5 Ma41±5 MaOnset of Onset of CoolingCooling
43±4 Ma43±4 Ma
AFT AgeAFT Age
46±5 Ma46±5 MaOnset of Onset of CoolingCooling
49±5 Ma49±5 Ma
AFT AgeAFT Age
46±5 Ma46±5 MaOnset of Onset of CoolingCooling
49±5 Ma49±5 Ma
- Significant Eocene cooling- Significant Eocene cooling- Note recent cooling- Note recent cooling
Mt. RitchieMt. RitchieMt. RitchieMt. Ritchie
No known tectonic mechanism to justify higher paleogeothermal gradients - No known tectonic mechanism to justify higher paleogeothermal gradients - thus we prefer the constant gradient solution (A)thus we prefer the constant gradient solution (A)
TimingTimingTimingTiming
Western BowserWestern Bowser
Northern BowserNorthern Bowser
Constant Values:Constant Values:~65-60 Ma~65-60 Ma~45-30 Ma~45-30 Ma~10-5 Ma~10-5 Ma
Constant Values:Constant Values:~65-60 Ma~65-60 Ma~45-30 Ma~45-30 Ma~10-5 Ma~10-5 Ma
Coast PlutonicCoast PlutonicBeltBelt
North American CratonNorth American Craton
StikiniaStikinia
EEWW Intermontane BeltIntermontane BeltSkeena Fold BeltSkeena Fold Belt
Bowser BasinBowser Basin SustatSustatBasinBasin
Omineca BeltOmineca BeltRocky MountainRocky Mountain
Fold & Thrust BeltFold & Thrust Belt
Subducting Farallon/Kula plateSubducting Farallon/Kula platebeneath the Coast Complexbeneath the Coast Complex
Bowser Basin (Skeena FB)Bowser Basin (Skeena FB)- regional AFT results -- regional AFT results -
Bowser Basin (Skeena FB)Bowser Basin (Skeena FB)- regional AFT results -- regional AFT results -
Rapid cooling Rapid cooling sometime:sometime:~65-60 Ma~65-60 Ma~45-30 Ma~45-30 Ma~10-5 Ma~10-5 Ma
Rapid cooling Rapid cooling sometime:sometime:~65-60 Ma~65-60 Ma~45-30 Ma~45-30 Ma~10-5 Ma~10-5 Ma
Rapid cooling at Rapid cooling at some time between:some time between:
~100-80 Ma~100-80 Ma~65-60 Ma~65-60 Ma~45-35 Ma~45-35 Ma~10-8 Ma~10-8 Ma
Rapid cooling at Rapid cooling at some time between:some time between:
~100-80 Ma~100-80 Ma~65-60 Ma~65-60 Ma~45-35 Ma~45-35 Ma~10-8 Ma~10-8 Ma
Rapid cooling at Rapid cooling at some time between:some time between:
~65-60 Ma~65-60 Ma~45-40 Ma~45-40 Ma
????
Rapid cooling at Rapid cooling at some time between:some time between:
~65-60 Ma~65-60 Ma~45-40 Ma~45-40 Ma
????
Rapid cooling at Rapid cooling at some time between:some time between:
~65-60 Ma~65-60 Ma~45-40 Ma~45-40 Ma
????
Rapid cooling at Rapid cooling at some time between:some time between:
~65-60 Ma~65-60 Ma~45-40 Ma~45-40 Ma
????
So what do AFT results suggest?So what do AFT results suggest?So what do AFT results suggest?So what do AFT results suggest?
- - AFT results are interpreted to record rapid cooling from paleotemperatures AFT results are interpreted to record rapid cooling from paleotemperatures ≥110-160°C ≥110-160°C (range based on different annealing resistivities from Dpar)(range based on different annealing resistivities from Dpar)
- Cooling is interpreted to have occurred in association with km-scale - Cooling is interpreted to have occurred in association with km-scale denudation throughout the region during the Paleocene, Eocene, Miocenedenudation throughout the region during the Paleocene, Eocene, Miocene
- M- Major episodes of denudation occurred within the Skeena Fold Belt after the ajor episodes of denudation occurred within the Skeena Fold Belt after the last known phase of contractional deformation last known phase of contractional deformation (between 75-53 Ma)(between 75-53 Ma)
- Results do not discount the possibility that minor reactivation within the fold - Results do not discount the possibility that minor reactivation within the fold belt might have occurred more recently than previously documentedbelt might have occurred more recently than previously documented
- - AFT results are interpreted to record rapid cooling from paleotemperatures AFT results are interpreted to record rapid cooling from paleotemperatures ≥110-160°C ≥110-160°C (range based on different annealing resistivities from Dpar)(range based on different annealing resistivities from Dpar)
- Cooling is interpreted to have occurred in association with km-scale - Cooling is interpreted to have occurred in association with km-scale denudation throughout the region during the Paleocene, Eocene, Miocenedenudation throughout the region during the Paleocene, Eocene, Miocene
- M- Major episodes of denudation occurred within the Skeena Fold Belt after the ajor episodes of denudation occurred within the Skeena Fold Belt after the last known phase of contractional deformation last known phase of contractional deformation (between 75-53 Ma)(between 75-53 Ma)
- Results do not discount the possibility that minor reactivation within the fold - Results do not discount the possibility that minor reactivation within the fold belt might have occurred more recently than previously documentedbelt might have occurred more recently than previously documented
Remember:Remember:
- - At least 2 distinct episodes of folding within the Skeena Fold Belt have been At least 2 distinct episodes of folding within the Skeena Fold Belt have been recognized:recognized:
1) >95 Ma, but <150 Ma - BLG rocks folded prior to Sustat Basin deposition1) >95 Ma, but <150 Ma - BLG rocks folded prior to Sustat Basin deposition
2) >53 Ma, but <75 Ma - Sustat Basin rocks folded, trucated by 53 Ma pluton2) >53 Ma, but <75 Ma - Sustat Basin rocks folded, trucated by 53 Ma pluton
Furthermore:Furthermore:Furthermore:Furthermore:
- - Incorporating regional thermal maturity data (%VR) with the AFT Incorporating regional thermal maturity data (%VR) with the AFT results and paleogeothermal gradient information derived from results and paleogeothermal gradient information derived from the a-3-J well, suggests that at least 7.0 to 4.4 km of the a-3-J well, suggests that at least 7.0 to 4.4 km of sedimentary section has been removed over sections of the sedimentary section has been removed over sections of the Bowser Basin Bowser Basin (assuming geothermal gradients of 31°C/km and (assuming geothermal gradients of 31°C/km and 45°C/km respectively)45°C/km respectively)
- Hydrocarbon generation from potential source beds ceased with - Hydrocarbon generation from potential source beds ceased with rapid cooling/denudation sometime between latest Cretaceous rapid cooling/denudation sometime between latest Cretaceous and Paleocene timesand Paleocene times
- Petroleum generation ceased earlier in overmature regions- Petroleum generation ceased earlier in overmature regions
- - Incorporating regional thermal maturity data (%VR) with the AFT Incorporating regional thermal maturity data (%VR) with the AFT results and paleogeothermal gradient information derived from results and paleogeothermal gradient information derived from the a-3-J well, suggests that at least 7.0 to 4.4 km of the a-3-J well, suggests that at least 7.0 to 4.4 km of sedimentary section has been removed over sections of the sedimentary section has been removed over sections of the Bowser Basin Bowser Basin (assuming geothermal gradients of 31°C/km and (assuming geothermal gradients of 31°C/km and 45°C/km respectively)45°C/km respectively)
- Hydrocarbon generation from potential source beds ceased with - Hydrocarbon generation from potential source beds ceased with rapid cooling/denudation sometime between latest Cretaceous rapid cooling/denudation sometime between latest Cretaceous and Paleocene timesand Paleocene times
- Petroleum generation ceased earlier in overmature regions- Petroleum generation ceased earlier in overmature regions
Bowser Basin / Skeena Fold BeltBowser Basin / Skeena Fold Belt
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Te
mp
era
ture
(°C
)T
em
pe
ratu
re (
°C) Time (Ma)Time (Ma)
11
22
33
33
22
11
Nu
mb
er
of
tra
cks
Nu
mb
er
of
tra
cks
Track length (µm)Track length (µm)
Final distributionFinal distribution(at time 3)(at time 3)
Fission Track MethodologyFission Track Methodology- System Response 1 -- System Response 1 -
Small Dpar TA*Small Dpar TA*
Large Dpar TA*Large Dpar TA*
**TA = Total Annealing (resetting)TA = Total Annealing (resetting)
Nu
mb
er
of
tra
cks
Nu
mb
er
of
tra
cks
Track length (µm)Track length (µm)
Final distributionFinal distribution(at time 3)(at time 3)
11
22
33
Fission Track MethodologyFission Track Methodology- System Response 2 -- System Response 2 -
Te
mp
era
ture
(°C
)T
em
pe
ratu
re (
°C) Time (Ma)Time (Ma)
33
22
11
Small Dpar TA*Small Dpar TA*
Large Dpar TA*Large Dpar TA*
**TA = Total Annealing (resetting)TA = Total Annealing (resetting)
Bowser Basin / Skeena Fold BeltBowser Basin / Skeena Fold Belt
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Lunch?Time for a
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