The past 66 million years, known as the Cenozoic Era, is particularly relevant to climate change because the world's climate changed from the greenhouse world of the dinosaurs to our modern icehouse world. But Cenozoic sediments in the Arctic are notoriously difficult to date using fossils (‘biostratigraphy’). The talk describes the methodology, based on 40 years work by Dr Jonathan Bujak, for establishing a biostratigraphic framework for the Cenozoic of the Arctic. This enables the history of the entire region to be correlated within the Arctic and with events in lower latitudes.

1. TOWARDS A BASIN-WIDE SCHEME
ARCTIC CENOZOIC BIOSTRATIGRAPHY
DR JONATHAN BUJAK

2. The talk is split into three parts
• Arctic paleoceanography and climate
• historical review of the problems
• solutions leading to an regional biozonation

3. we first need a climatic and oceanographic
perspective going back into the Mesozoic

4. MESOZOIC OCEANOGRAPHY AND CLIMATE
• Glaciation was absent from both poles during the Mesozoic
due to open marine connection, warming by oceanic currents
and higher CO2 levels
• the Arctic comprised a warm highly productive ocean
that had open marine connection to the Pacific

5. ….during the Triassic…..
source: L.A. Lawver, A. Grantz, L.M.
Gahagan & D.A. Campbell,
University of Texas Institute for
Geophysics

6. ….. continuing through
the Middle and Late Jurassic….

7. …..into the Early Cretaceous

8. this was reflected by the marine biotas

9. the warm highly productive ocean was also fringed by abundant vegetation
so that the rich and diverse marine and nonmarine fossils
provide a high-resolution zonal scheme for the Arctic…..

10. …..that has been applied by
Jonathan Bujak across the Alaskan
and Canadian Arctic from the
Chukchi Sea to the Sverdrup Basin

11. including the 2004 Arctic
Coring Expedition which drilled
the Lomonosov Ridge

12. into the Cenozoic

13. CENOZOIC BIOSTRATIGRAPHY:
REGIONAL SETTING AND CLIMATE
the Arctic Basin occupied a high-latitude position during
the Cenozoic
the climate shifted dramatically after the Early Eocene
from warm-temperate to today’s Arctic environments….
…..so the assemblages became progressively impoverished
and this affected both marine and nonmarine taxa

14. from the Mesozoic - early Eocene greenhouse world
the Cenozoic cooling had
a massive effect on the
Arctic Basin

15. to the modern
icehouse world

16. and this temperature fall was the
most important control on the
Cenozoic palynological
succession

17. p
Arctic Basin location
the Arctic Basin was centred on the
North Pole through the Cenozoic
from the present…..

18. p
Arctic Basin
centred on the North Pole
through the Cenozoic
…..back to the Paleocene

19. p
source: L.A. Lawver, A. Grantz,
L.M. Gahagan & D.A. Campbell,
University of Texas Institute for
Geophysics
Arctic Basin
centred on the North Pole through
the Cenozoic
and the Late Cretaceous

20. Arctic Basin
the entire Arctic region therefore
underwent the same temperature
changes during the Cenozoic -
but several problems need
to be solved in order to erect
a reliable Arctic-wide scheme

21. CENOZOIC ARCTIC BIOSTRATIGRAPHY
PROBLEMS

22. AGE RANGES AND FACIES
most marine and nonmarine palynomorphs died out early
in the Arctic due to decreased water and air temperature
so that the age ranges differ from those to the south
how can we develop a chronostratigraphy tied to the lower latitudes?

23. AGE RANGES AND FACIES
.....and there is also the problem of reworking
in the Canadian Beaufort Mackenzie Delta

24. reworked Mesozoic assemblages strongly dilute
the impoverished in situ Cenozoic populations
the reworked taxa are large and conspicuous, whereas the
in situ populations are small, pale and easily overlooked…..
…..and this has resulted in many erroneous ages, such as Early
Cretaceous age assigned to Eocene and Oligocene sections

25. CENOZOIC BIOSTRATIGRAPHY
PERCEPTION
….. so that there is a widespread view that
1. Arctic Cenozoic biostratigraphy is unreliable
2. the Cenozoic can only be subdivided into a few zones
3. and the zones must be based mostly on non-marine pollen

26. LACK OF PUBLISHED ZONAL SCHEMES
like the Mesozoic, a comprehensive
palynological zonation has not been published
the only published Cenozoic scheme is that of
Geoff Norris (1989) at the University of Toronto

27. NORRIS’ PUBLISHED SCHEME
but this has few zones
and low resolution
there is little or no
chronostratigraphic control
the three Oligocene ‘zones’ are
actually diachronous biofacies…..
…..and the scheme is based
on a single well – Nuktak C-22
which TD ‘d in the Middle Eocene

28. CENOZOIC BIOSTRATIGRAPHY
STRATEGY
…..so we need to go beyond traditional biostratigraphic techniques, using
FLUORESCENCE MICROSCOPY
 to locate and identify rare and inconspicuous in situ species
 to distinguish different populations and provenance of reworking
PALEOCLIMATIC CORRELATIONS
 to tie into chronostratigraphy established in lower latitudes

29. FLUORESCENCE
short wavelength fluorescence
is progressively lost by
dinocyst and angiosperm walls
as they become older
Bujak and Davies
(GSC 1982, 1983)
called this ‘biochemical
fluorescence’

30. as seen in the Canadian Beaufort Kopanoar M-13 well under normal light

31. normal light
yellow-green
fluorescence emission
yellow-green biochemical fluorescence
highlights the in situ population

32. normal light
yellow-green
fluorescence emission
and blue
fluorescence emission
and blue fluorescence does this even more

33. normal light
yellow-green
fluorescence emission
blue
fluorescence emission
this lets us see and identify the rare in situ palynomorphs

34. normal light
yellow-green
fluorescence emission
blue
fluorescence emission
which are very difficult to observe under normal light

35. NEW OBSERVATIONS
Fluorescence also shows common Neogene dinoflagellates
that migrated into the Arctic during the Miocene warm phase
most of these have not been recorded before in the Arctic
but they are known from the North Atlantic and Pacific…..
….. so the dinocysts and pollen together provide
a high-resolution Cenozoic zonation

36. Bujak and Davies (GSC 1982, 1983) also examined
other Arctic wells and the Hibernia P-15 discovery well
in the NE Newfoundland Basin
They observed a regeneration of fluorescence coincident
with the onset of the oil window which they termed ‘thermochemical
fluorescence’

37. normal lightbiochemical fluorescence
thermochemical fluorescence
and the combination of biochemical and thermochemical fluorescence
helps to distinguish different populations and provenance of reworking

38. CHRONOSTRATIGRAPHY
PROBLEM
it is difficult to correlate Arctic Cenozoic sections with lower latitudes because
stratigraphic ranges are truncated in the Arctic

39. STRATEGY
Cenozoic temperatures changed as a series of steps
as marine gateways opened and closed and CO2 levels changed
the steps are global chronostratigraphic datums
and have a stronger expression towards the poles
each step caused temperature-sensitive species to die out and
the number of affected species increased towards the poles
CHRONOSTRATIGRAPHY

40. CORRELATION FROM LOW TO MID LATITUDES
so let’s look at the effect of the cooling steps
on dinoflagellates species at different latitudes by
first constructing a latitudinal transect from the Tethys
through the North Atlantic into the North Sea

41. the Tethyan to North Sea transect

42. oxygen isotope stratigraphy
magnetostratigraphy
standard NP & P zones
Stages and absolute time
provides us with a robust chronostratigraphy

43. ONSET OF COOLING
(AZOLLA EVENT)
we can then overlay the middle and late
Eocene cooling steps based on palynology
beginning with the Azolla event which
marked the onset of cooling

44. this shows that a cooling step
occurs in the North Sea region
coincident with the Azolla Event
ONSET OF COOLING
(AZOLLA EVENT)

45. and that cooling did not
significantly affect the Tethys until
the Terminal Eocene Event (TEE)
TEE

46. it also shows that the extinction of temperature-
sensitive dinoflagellates was diachronous
with latitude (e.g. T. delicata)

47. indicating that the North Sea System
had a cooler water regime than the
North Atlantic System

48. due to separation of two oceanographic
systems along the Wyville Thompson Ridge
and Artois Dome……

49. the entire region had
full marine connection
in the Danian

50. …but late Paleocene
uplift of the Greenland
mantle plume

51. NORTH
SEA
SYSTEM
NORTH ATLANTIC
SYSTEM
BAFFIN
SYSTEM
separated the region
into three distinct
oceanic/biotic
systems/provinces

52. NORTH
SEA
SYSTEM
NORTH ATLANTIC
SYSTEM
BAFFIN
SYSTEM
dinoflagellates clearly
show the differences in
sea-surface temperature
(SST) between
these systems

53. for example - the diachronous range of T. delicata which is older
in the North Sea System than in the North Atlantic System -
reflecting a progressive SST fall to below the temperature
tolerance of T. delicata (e.g., to below 14oC)

54. so we can use the dinoflagellate record
to reconstruct SST for the entire region

55. the succession of cooling steps
is reflected by dinoflagellates,
non-marine pollen and
the isotope record

56. showing that the controlling mechanism
was temperature change rather than local facies

57. most of the cooling steps correspond to Stage boundaries
because the boundaries were originally defined by major biotic,
tectonic, sedimentary and oceanographic changes

58. so we can correlate the events and stages across the entire region
using Bujak’s North Atlantic palynological zones

59. this gives us a robust framework with strong
magnetostratigraphic, chronostratigraphic,
biostratigraphic and isotope control

60. STEP 2:
CORRELATE FROM MID TO HIGH LATITUDES

61. the climatic cooling had a massive effect on high-latitudes
because the middle and late Eocene cooling steps
progressively eliminated most dinocyst
and angiosperms species from the Arctic

62. we can document the changes on both sides of Greenland even though
these has restricted marine connection to the Arctic.
Let’s look at the western transect through the Labrador Sea

63. western transect into the Arctic

64. we see that the cooling events caused major extinctions in the Arctic
that affected the marine dinocysts and terrestrial angiosperms

65. …..both of which define our Arctic palynological zones

66. so the cooling events and our Arctic zones can be
correlated chronostratigraphically to the south and
hence with absolute time and lower latitude stages

67. giving us a chronostratigraphic framework
for the Arctic Cenozoic succession

68. ARCTIC CENOZOIC ZONATION
SUMMARY
[1] fluorescence microscopy provides a high-resolution zonal scheme
by helping us to see the in situ palynomorphs
[2] the cooling steps provide a chronostratigraphic framework tied to the south
[3] the scheme can be applied to the entire Arctic region because the Arctic
was centered on the North Pole through the Cenozoic

69. ARCTIC CENOZOIC ZONATION
AND PALEOTEMPERATURE

70. BUJAK’S ARCTIC CENOZOIC
PALYNOLOGICAL ZONATION
[1] has good resolution
though most of the section
[2] avoids local biofacies
[3] can be tied to
lower-latitudes and
hence absolute time

71. giving us an integrated
climatic–biostratigraphic
scheme that can be
correlated with
paleotemperature …..

72. …..using a succession of
chronostratigraphically
defined climatic datums,
which help us reconstruct
the climatic history
of the Arctic

73. we first see a Paleocene-Early Eocene
greenhouse world with warm
temperatures…..

74. …..with the Azolla and
Apectodinium (PETM/EETM)
events being
chronostratigraphic datums
tied to lower latitudes

75. and the Azolla event
triggering the initial shift
from greenhouse
towards icehouse

76. the Azolla Event
was followed by
a succession of
Middle and Late Eocene
cooling steps

77. …..which are zonal and
subzonal boundaries

78. ending with the
Terminal Eocene
Cooling Event

79. leading to the impoverished
Oligocene cold phase
which is difficult
to subdivide due to
the scarcity of markers

80. ….except in the early
Oligocene of the Barents Sea
due to inflow of the
proto Gulf Stream

81. this was followed by the
Miocene warm period
characterised by the
migration of temperate
dinocysts and
angiosperms
into the Arctic

82. with strong
Plio-Pleistocene cooling leading
to the
modern Arctic marine
and terrestrial regime

83. and finally
because the Arctic Ocean
was centred on the North
Pole through the Cenozoic
we can predict that the
scheme should be valid for
the entire Arctic Basin…..

84. giving us
our Arctic-wide
biostratigraphic
scheme

85. Please contact Dr Jonathan Bujak for
more information
or for a free copy of this talk
Email: info@azollabiosystems.co.uk.