use of paleochemotaxonomy for tracing paleoflora and paleoclimatic changes during jurassic...
TRANSCRIPT
Use of paleochemotaxonomy for
tracing
paleoflora and paleoclimatic
changes
during JurassicHAUTEVELLE Yann
MICHELS Raymond, MALARTRE Fabrice, TROUILLER Alain
22nd IMOG, Seville - Spain September 12-16, 2005
Desertic climate
Temperate climate
Tropical climate
Polar climate
flora ↔ climate
Paleoflora as paleoclimatic recorder
INTRODUCTION
INTRODUCTION
PALEOBOTANY(fossil plants assemblages)
PALYNOLOGY(spore & pollens assemblages)
classically used for the
reconstruction of paleofloras
and paleoclimates
Paleoflora and paleoclimatic proxies
Vascular plant biomarkers have a paleochemotaxonomic value and are specific of a restricted number of plant taxa
PALEOCHEMOTAXONOMY (plant biomarkers assemblages)
Extant & fossil plants classification
Plantae kingdom
INTRODUCTION
Phytocenose or floraat the time
of the deposition
angiospermspines pines
cypress
sequoia
Land plant biomarkers
distribution in sediment
ferns
paleoflora reconstruction
Vascular plant biomarkers distribution in sediments & rocks is a « picture » of the terrestrial paleophytocenose at the time of
the deposition
Stratigraphicrecord
paleobiodiversity
paleoflora
paleoclimate
T°, humidity
desertic climate
Geolo
gic
al ti
mes
tropical climate
temperate climate
Molecularfacies
Use of paleochemotaxonomy in stratigraphy
INTRODUCTION
Aims
INTRODUCTION
Aims of this work :
1) study the evolution of vascular plant biomarkers on a stratigraphic series of paleoclimatic interest ;
2) interpret this evolution in terms of paleoflora then in terms of paleoclimatic changes ;
Cadinane class biomarkers (sesquiterpenoids)
cadalene
diagenetic evolution
I) Paleochemotaxonomic data used in this study
Cadalene Generic plant biomarker
Molecularbiomarkers
Biologicalprecursors
O/ Gingkoales
O/ Coniferales
P/ Bryophytaand others…
Biologicalproducers Reactional intermediates
cadinenes
cadinols
I) Paleochemotaxonomic data used in this study
Abietane class biomarkers (diterpenoids)
(keto)phenolic
abietanes
abietanoicacids
diageneticevolution
Molecularbiomarkers
Biologicalprecursors
retene
Reactional intermediates
O/ Coniferales
Biologicalproducers
O/ Coniferales
F/ Pinaceae
O/ Coniferales
F/ all families except
Pinaceae
I) Paleochemotaxonomic data used in this study
Saturated bi-, tri & tetracyclic diterpanes (diterpenoids)
bi-, tricyclic diterpanes (labdanes, norabietanes, pimaranes, …)
bi-, tricyclic diterpanes ½ specific conifers biomarkers
tetracyclic diterpanesAll conifer familiesexcept Pinaceae
O/ Coniferales
F/ all families
tetracyclic diterpanes (phyllocladanes, kauranes, beyeranes, …)
O/ Coniferales
F/ all families except
Pinaceae
Geological background of studied series
II) Geological and paleobotanical background
Jurassic stratigraphy of Paris basin (France)Type-section of the Paris
basin
Paleoenvironments
Deep ←→ Shallow
Terrigenous deposits & flooding events
Pliensbachian
Sinemurian
Toarcian
AalenianBajocian
Bathonian
Callovian
Oxfordian
Kimmeridgian
Tithonian
Paleoclimatic interest
Eustatic regression cooling
event (glaciation ?)
(Dromart et al., 2003, Cecca et al., 2005)
Upper Callovian
Global warming(Cecca et al., 2005)
Oxfordian & Kim-meridgian
Climatic control of the alternance
carbonate / terrigenous deposits ?
Geological background of studied series
East ofParisBasin
(4 wells)
London-BrabantMassif
marine environment
Paleogeography 5 studied wells (Callovo-Oxfordian)
A 901well
II) Geological and paleobotanical background
Paleobotanical background of studied sedimentary series
O/ Filicales(Ferns)
Some paleobotanical studies indicate the presence of many plant taxa on emerged lands boundering the Paris basin (London-Brabant Massif).
East ofParisBasin
(4 wells)
London-BrabantMassif
marine environment
A 901well
II) Geological and paleobotanical background
Paleobotanical background of studied sedimentary series
Some paleobotanical studies indicate the presence of many plant taxa on emerged lands boundering the Paris basin (London-Brabant Massif).
East ofParisBasin
(4 wells)
London-BrabantMassif
marine environment
A 901well
O/ Cycadales
II) Geological and paleobotanical background
Paleobotanical background of studied sedimentary series
Some paleobotanical studies indicate the presence of many plant taxa on emerged lands boundering the Paris basin (London-Brabant Massif).
East ofParisBasin
(4 wells)
London-BrabantMassif
marine environment
A 901well
Ferns(Filicales)
O/ Ginkgoales
II) Geological and paleobotanical background
Paleobotanical background of studied sedimentary series
Some paleobotanical studies indicate the presence of many plant taxa on emerged lands boundering the Paris basin (London-Brabant Massif).
East ofParisBasin
(4 wells)
London-BrabantMassif
marine environment
Bennettitalesand
Caytoniales(presently
extinct orders)
A 901well
II) Geological and paleobotanical background
Paleobotanical background of studied sedimentary series
Some paleobotanical studies indicate the presence of many plant taxa on emerged lands boundering the Paris basin (London-Brabant Massif).
East ofParisBasin
(4 wells)
London-BrabantMassif
marine environment
Ferns(Filicales)
O/ ConiferalesF/ AraucariaceaeF/ PodocarpaceaeF/ CupressaceaeF/ TaxodiaceaeF/ Pinaceae
F/ CheirolepidiaceaeA 901well
II) Geological and paleobotanical background
Retene/cadalene ratio
III) Chemostratigraphic evidence of a paleofloral and paleoclimatic change
MSE 101-649 m m/z=183+219+237+223+241+233
m/z=183+219+ 237+223+241+233MSE 101-493.3 m
Other vascular plant biomarkers
Retene-rich extract (Oxfordian platform)
Retene-poor extract (Callovo-Oxfordian claystones)
aromatic fraction
cadalene
cadalene
retene
retene
III) Chemostratigraphic evidence of a paleofloral and paleoclimatic change
MSE 101-649 m
hopanes
hopanes
MSE 101-493.3 m High content ofsaturated diterpanes
m/z=123+109+ 163+191
m/z=123+109+ 163+191
Other vascular plant biomarkers
Retene-rich extract (Oxfordian platform)
Retene-poor extract (Callovo-Oxfordian claystones)
aliphatic fraction
Very low contentor absence of
saturated diterpanes
III) Chemostratigraphic evidence of a paleofloral and paleoclimatic change
hopanes
MSE 101-493.3 m m/z=123+109+ 163+191High content ofsaturated diterpanes
Other vascular plant biomarkers
Retene-rich extract (Oxfordian platform)aliphatic fraction
isomers
Retene-poor extract (Callovo-Oxfordian claystones)
Tetracyclic diterpanes
III) Chemostratigraphic evidence of a paleofloral and paleoclimatic change
MSE 101-649 m
m/z=239+253MSE 101-493.3 m
m/z=239+253
Dehydroabieticacid
Abietic acid
Other vascular plant biomarkers
Retene-rich extract (Oxfordian platform)
Retene-poor extract (Callovo-Oxfordian claystones)
Polar fraction
Dehydroabieticacid
Abietic acid
III) Chemostratigraphic evidence of a paleofloral and paleoclimatic change
Cause of the increase of the retene/cadalene ratio
Hypothesis 1 :A better preservation of the retene precursors
by clay minerals
Hypothesis 2 :
Formation of saturated abietanes instead of
retene in the claystones
Hypothesis 3 :Increase of the abietane-class diterpenoids
input into the depositional environment
paleoflora change on emerged lands (London-
Brabant Massif)
III) Chemostratigraphic evidence of a paleofloral and paleoclimatic change
In Callovo-Oxfordian claystones, the absence
— of abietanoic acids
— their reactional intermediates
— of saturated abietanes
}Hypothesis 1
Hypothesis 2
Hypothesis 1 : a better preservation of retene precursors by clay minerals
Hypothesis 2 : formation of saturated abietanes in claystones instead of aromatic abietanes
The increase of retene/cadalene ratio reflects a paleoflora
change from the Cordatum zone (top of the Lower Oxfordian)
on the London-Brabant Massif
Hypothesis 3 : increase of the abietane-type diterpenoids input in the depositional environment
Cause of the increase of the retene/cadalene ratio
III) Chemostratigraphic evidence of a paleofloral and paleoclimatic change
Nature of the paleoflora change
(keto)phenolic
abietanes
O/ Coniferales
F/ all families except
Pinaceae
Biologicalproducers
O/ Coniferales
F/ Pinaceae
abietanoicacids
diageneticevolution
retene
All conifer families All conifer families except Pinaceae
di-, tricyclic diterpanes
tetracyclic diterpanes
III) Chemostratigraphic evidence of a paleofloral and paleoclimatic change
What is its meaning in terms of paleoclimatic
change ?
Nature of the paleoflora change
III) Chemostratigraphic evidence of a paleofloral and paleoclimatic change
This evolution indicates an
increase of the proportion of
Pinaceae since the end of
the Lower Oxfordian
(Cordatum zone).
Pinaceae have acquired many xeromorphic adaptations :
+ more or less flat niddle-like leaves+ leaves covered by a thick layer of epicuticular waxes
Cheirolepidia-, Podocarpa-, Cupressa- & Taxodiaceae frequently colonize peat and swamps, not the Pinaceae.
Paleoclimatic interpretation
+ stomata sunken in wells and furrows+ stomata mostly closed by gardian cells
Others conifers families :
III) Chemostratigraphic evidence of a paleofloral and paleoclimatic change
Pinaceae have acquired many xeromorphic adaptations :
+ more or less flat niddle-like leaves+ leaves covered by a thick layer of epicuticular waxes
+ stomata sunken in wells and furrows
Ferns, Cycadales, Bennettitales preferably occur under wet climates.
+ stomata mostly closed by gardian cells
Paleoclimatic interpretation
Plants other than conifers :
III) Chemostratigraphic evidence of a paleofloral and paleoclimatic change
Extant Cycadaleslocalisation
The increase of the
Pinaceae proportion indicates
an increase of aridity since
the end of the Lower
Oxfordian (Cordatum zone).
Paleoclimatic interpretation
III) Chemostratigraphic evidence of a paleofloral and paleoclimatic change
Information brought by other paleoclimatic proxies
Isotopic paleothermometry δO18 & Paleobiogeography of marine invertebrates : increase of the oceanic water temperature at the western european scale (Riboulleau et al., 1998; Cecca et al., 2005; Martin Garin et al., 2005)
Clay mineralogy : disapearance & decrease of the kaolinite content around the Lower / Middle Oxfordian increase of aridity (Pellenard et al., 2005)
Palynology : increase of temperature and aridity in England (Abbink et al., 2001)
III) Chemostratigraphic evidence of a paleofloral and paleoclimatic change
Paleophytogeography :Upper JurassicLondon-Brabant Massif is within the Winterwet paleo- climatic zone.
Dry climate with one humid season.
Middle JurassicLondon-Brabant Massif is within the tropical paleo- climatic zone.
Wet and warm climate.
(Rees et al., 2000)
III) Chemostratigraphic evidence of a paleofloral and paleoclimatic change
Information brought by other paleoclimatic proxies
A similar increase of the relative proportion of retene compared to cadalene in the Oxfordian sedimentary series of Australia
Comparison with Callovo-Oxfordian sedimentary series of Australia(van Aarssen et al., 2000)
This increase is also interpreted as a global paleoclimatic change (van Aarssen et al., 2000).
retene
(van Aarssen et al., 2000)
III) Chemostratigraphic evidence of a paleofloral and paleoclimatic change
Comparison with Jurassic sedimentary series of Australia(van Aarssen et al., 2000)
III) Chemostratigraphic evidence of a paleofloral and paleoclimatic change
400
500
600
800
900
1000
0 5 10 15 20
Stratigraphic time line
Retene/cadalene
Cycle 2
Cycle 1
700Cycle 1Cycle 3
Cycle 2 ?
Cycle 1 ?
Cycle 3 ?
Stratigraphic time line
Carnavaron Basin, Australia(van Aarssen et al., 2000)
Paris Basin, France(preliminary results)
CONCLUSIONS
— vascular plant biomarkers constitute an efficient tool
for tracing paleoflora and paleoclimatic changes during
geological times.
— Vascular plant biomarker chemostratigraphy indicates an
increase of the proportion of Pinaceae on the London-Brabant
Massif at the end of the Lower Oxfordian which is related to
an increase of aridity.
— Because a similar evolution is reported in the Oxfordian
sedimentary series of Australia, this climatic change could be
recorded at the global scale.
Poster session
POSTER II. PC2-4.
POSTER II. PC2-5.
Thank you for your attention