1. Early Jurassic (Sinemurian – Toarcian)
palynology of the Lias, Lyme Regis, Dorset
Clarissa Wright

2. Project aims
• Correlate palynomorph occurrences and abundance trends with established
biostratigraphic schemes.
- Morbey (1978) pollen & spores for
NW Europe
- Powell (1992) dinoflagellate cysts
for NW Europe
- Wall (1965) acritarchs in Lyme Regis,
Dorset
• Deduce palaeoenvironmental
implications based on
palynomorph and palynofacies analysis.
• Based on outcrop sample material
ranging from the Sinemurian to the
Toarcian.
Sample no. Location Lithostratigraphic fm. Member Bio Success. Age Ammonite Zones
1 - 4 The Cobb E Sinemurian
3 Blue Lias Blue Lias Semicostatum
5 – 7b Stonebarrow Cliff E Sinemurian
L Sinemurian
5 Charmouth Mudstone Black Ven Marl Turneri
7a Charmouth Mudstone Black Ven Marl Obtusum
8 - 23 Golden Cap E Pliensbachian
L Pliensbachian
8, 10 Charmouth Mudstone Belemnite Marl Jamesoni/ibex
13 Charmouth Mudstone ?Belemnite Marl Jamesoni/ibex
14 Charmouth Mudstone Green Ammonite Margaritatus
16, 18 Dyrham fm Three Tiers “
22 Dyrham fm Eype Clay “
24 - 37 Eype Mouth L Pliensbachian
E Toarcian
24 Dyrham fm Eype Clay “
27 Dyrham fm Down Cliff Sand “
30, 32 Dyrham fm Thorncombe Sand “
35 Beacon Limestone fm Levesquei –
spinatum
36 Bridport Sand fm Down Cliff Clay Levesquei
38, 39 Burton Bradstock L Toarcian
38, 39 Bridport Sand fm Bridport Sand Levesquei

3. Lias Group in the UK
SINEMURIAN
EL
PLIENSBACHIAN
EL
TOARCIAN
EL

5. Material & Methods
Material had been previously
prepared using standard
preparation techniques
(following CGG standards in
1983).
Optical light, x1000 mag.,
laterally scanning of slides.
Palynomorph analysis: Count of 250 palynomorphs (pollen, spores,
acritarchs, dinoflagellates) on oxidised material.
Palynofacies analysis: Count of 500 particles of organic matter –
AOM, palynomorphs, phytoclasts on unoxidised material.
Limitation: Poor sample preservation

6. Scale bar = 10μm.

7. Biostratigraphy – pollen & spores
• Pollen and spore
assemblages
compared to scheme
of Morbey 1978 for
NW Europe.
SINEMURIAN
EL
PLIENSBACHIAN
EL
TOARCIAN
EL
Chronostratigraphy

8. Biostratigraphy - Dinoflagellates
Where dinoflagellates are
identified, they match the
scheme of Powell (1992).
Nannoceratopsis gracilis
zone
Luehndea spinosa zone
Liasidium variabile zone
Dapcodinium priscum
zone
X
X

9. Biostratigraphy - Acritarchs
• Species occurrences compared
to Wall (1965), in a study of the
Lias from Lyme Regis.
• Results show consistency, aside
from one case.
• Micrhystridium wattonensis is
identified earlier than claimed
by the Author.
• Peaked abundance in L
Toarcian.

10. Palynofacies
Toarcian
• Phytoclast
dominated
• Sparse
assemblages
Pliensbachian
• Palynomorph
and phytoclast
dominated
• Influx of
freshwater algae
Sinemurian
• AOM dominated
• Sparse
assemblages
0 100 200 300 400 500
3i
5
7Ai
24
26
27
28
30
32
35
36
38
39
Sampleno.
Relative proportions of Phytoclasts, Palynomorphs and AOM.
PHYT
PLYN
AOM
SINEM.
EL
PLIENSBACHIAN
L
L
TOARCIAN
EL
Trends broadly correspond to sample lithologies
and stratigraphic episodes in the Wessex basin
discussed by Hessselbo (2008).

11. Climate implications
Classopollis pollen &
spores
• Classopollis vs.
Bisaccate ratio
• Spore vs. Bisaccate
ratio
Likewise utilised by
(Pienkowski &
Waksmundzka, 2006) in
Poland

12. Bisaccate pollen
• Potential implications for climate
and proximity to shore.
• Consistently abundant, except in
Obtusum and Levesquei zone.
Temperature implications agree with
deducations by Van de Schootbrugge
et al (2005), and Dera et al 2012.

13. Conclusion
• Pollen, spores, dinoflagellates and acritarch trends show correlation
with established schemes and publications.
• Palynofacies analysis implies environmental conditions of
offshore/anoxic in the Sinemurian, basinal-shelfal in the
Pliensbachian, and shelfal in the Toarcian.
• Thermophilic indicators may reflect warming in the Sinemurian, and
cooling in the Late Pliensbachian.
Acknowledgements: Thank you to Jim Fenton, Guy Harrington and Ian
Boomer, and teaching associates of this course.