the geomagnetic polarity time scale for eary...
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THE GEOMAGNETIC POLARITY TIME SCALE FOR EARY PALEOZOIC: DATA AND SYNTHESE
1 2Vladimir Pavlov and Yves Gallet1 Institute of Physics of the Earth, Russian Academy of Sciences
2 Institut de Physique
Late Ediacarian - Hyperactivity of the Earth magnetic field?
White sea area, Arkhangelsk region, Late Ediacarian, 558-555 Ma, siltstone and claystone,
about 60 reversals in 420 m,-1 estimated revrsal rate ~ 20 RMa
South Urals, Late Ediacarian, 545-550 Masiltstone and sandstone, 40 polarity zones
-1 in 110 m, estimated revrsal rate ~ 20-25 RMa
Southwestern Siberian platform, Late Ediacarian, ~550 Ma, siltstone and sandstone, 58 polarity zones
-1 in 60 m, estimated reversal rate > 30 RMa
Available data indicate that on the eve of and around the Precambrian-Phanerozoic transition geodinamo had operated in a hyper-activity reversing mode (Gallet and Pavlov, 2016) characterized by an extreme geomagnetic reversal frequency.
INTRODUCTION
Constructing the Geomagnetic Polarity Time Scale (GPTS) through the geological history is of crucial importance to address several major issues in Earth sciences, as for instance the long-term evolution of the geodynamo. The GPTS is also an important chronological tool allowing one to decipher the age and duration of various geological processes. Moreover, GPTS is widely used in prospecting for commercial minerals and in petroleum geology
. The chronology of the geomagnetic polarity reversals since the Upper Jurassic is rather well known thanks to the magnetic
anomalies recorded in the sea floor. For more ancient epochs our knowledge of the GPTS is still very fragmentary and much more uncertain. However significant information has been obtained for several time intervals, in particular for the Triassic and the beginning of the Phanerozoic.
We will focus our presentation on recent developments made in the determination of the GPTS during the Early Paleozoic (Cambrian and Ordovician).
Upper Cambrian
Kulumbesection
Khorbusuonka section
May
an s
tage
Mid
dle
Cam
bria
n
An
om
oca
rioid
es l
imb
ata
eform
isL
.laev
igata
- A
.tru
nca
ta
Ep
och
3
Mid
dle
Cam
bri
an
Am
ga s
tage
Toy
on s
tage
Bot
oma
T.g
ibbu
sT
.fis
sus
- P
.sach
eri
Ku
onam
- k
ites
Ory
ctoc
ara
Low
er C
amb
rian
Ep
och
2E
poc
h 3
Am
ga s
tage
Mayan
sta
ge
Mid
dle
Cam
bri
an
An
om
oca
rioid
es l
imb
ata
eform
isC
.per
fora
tus-
A.h
enri
ciT
.fis
sus-
P.s
ach
eri
T.g
ibbu
s
Ep
och
3
Cordylodusangulatus
Cordylodusangulatus
Cordyloduslindstromi
Cordyloduslindstromi
Cordylodusprolindstromi
Hirsutodontussimplex
Cordylodusproavus
Cordylodusproavus
H.discretus
H.appresus
H.resimus
Teridontusnakamurai
Pro
conodontu
s
Post
ero
-co
statu
sM
ulle
ri
Eoco
nodontu
s
C.minutus
P.muelleri
P.postero-costatus
P.tenui-serratus
Nya
yan
Loparian
Mansi
Black Mountain,
Australia Dayangcha,
Kulumbe
NW China
NW Siberia
C-
C-
D+
D+
D+
E-
E-
F1+
F1+
F1+
F2-
F3+
F3+
F3+
G1-
G2+
G3-
G4+
G5-
H+
H+
H+
G-
A-
B2-
B+
Ripperan and Kirschvink, 1992
Ripperdan et al
Gallet and Pavlov, 1998
., 1993
Ke
tyia
nY
ura
kia
nE
nts
ian
Тр
ем
ад
ок
Ар
ени
г
C.proavus
C.intermedius
C.angulatus
C.herfurhi
S.quadra-plicatus
Tangchan,Northern China
Eoconodontus (E.)notchpeakensis
Hirsutodontus ani
Drepanoistodus delfiter
Pro
toco
nodo
ntus
C.primitivus
Eoconodontus (E.)alisonae
Westergaardodinaamplicava
Eoconodontu
s
Paroistodusproteus
?
Rak
hmet
Aks
ay
Cordylodus proavus
Cordylodus intermedius
Cordylodus lindstromi
P.dahlmani-P.memorabilis
Sak
sB
atyr
bay
Ung
urA
ktay
Stages
Are
nig
(F
loia
n-D
arr
iwili
an)
Tre
madoc
Upper
Cam
brian
F1+
F3+G2+
H+
D+
B1+
B3+
B1+
B3+
I+
J+
J+
I+
I+
Madyian
Tavgian
Nganasanian
Ayus
okka
n
Yang et al., 2002
Mid
dle
cam
brian
Upper Cambrian - lowermost OrdovicianComparison of magnetostratigraphy of sections
from Siberia, Australia and China Composite
section
Kulumbe section: Uppermost Middle Cambrian- Lowermost Ordovician
Magnetostratigraphy from the Middle Cambrian through the Middle Ordovician Ordovician
The Middle Cambrian was mostly characterized by very high reversal frequency. Beginning from the end of the Middle Cambrian through Early Ordovician (Trema-doc) the geodinamo was in its “normal reversing mode” (Gallet and Pavlov, 2016) with medium to low reversal frequency. Between the Late Tremadocian and the Middle Llandeilian (begiining of the Sandbian age) the superchron Moyero occurred. This superchron of reversed polarity would have a duration of ~20 Myr.
Няй
ски
йУ
гор
ски
йК
им
ай
ски
йМ
укте
йск
ий
Вол
гинск
ий
Ки
ре
нск
о-
куд
ри
нск
ий
Ар
ен
иг
Лл
ан
ви
рн
Лл
ан
ви
рн
Лл
ан
ви
рн
Лл
ан
дей
ло
Ва
ра
нгу
Хун
небе
ргВ
ол
хов
Кун
да
ЛМГ
Уха
куК
укрус
е
Тр
ем
ад
ок
Ар
ен
иг
Лл
ан
ви
рн
Лл
ан
дей
ло
Азе
ри
Би
лл
инге
н
Composite section
Moyero
Kulumbe
Rozhkova
Tosna(Smethurst et al., 1998)
Lava(Smethurst et al., 1998)
South Sweden(Torsvik and Trench, 1991a)
Magnetostratigraphy of the Arenig and the Llanvirn
Ви
хор
евск
ий
Tre
mad
oc
Flo
ian
Siberia Europe
Dap
ing
ian
Dap
rriw
ilia
nS
an
db
ian
Flo
ian
Dap
ing
ian
Dap
rriw
ilia
nS
an
db
ian
Kudri
nsk
yC
he
rto
vsky
Volg
insk
y
Lla
ndeilo
Cara
doc
Sandbia
n
Llan
virn
Kir
ensk
y
Kulumbe
Stolbovaya
?
?
?
?
?
?
?
?
Kudrino,Rodionov et al.,2001;This study
Polovinka,Pavlov et al.,2000
Profile 2 Profile 1
?
Moyero,Gallet and Pavlov, 1996.
Alexeevka,this study
Gullhogen,Trench and Torsvik, 1991
Hallekis,Trench and Torsvik, 1991
Lena, 59.8N, 118.1E,Torsvik et al.,1995
Lla
ndeilo
Lla
nvirn
Cara
doc
Re
gio
sta
ge
Se
rie
Siberian platform East-European platformComposite Scale
Magnetostratigraphy of the Middle Ordovician
Re
gio
sta
ge
Se
rie
Gra
pto
lite
zo
ne
s
Uhaku
Kukru
se
Cara
doc
Lla
ndeilo
Lla
nvirn
N.g
racilis
G.t
ere
tiu
scu
lus
N.g
racili
sG
.te
retiu
scu
lus
Gra
pto
lite
zo
ne
s
Darr
iwili
an
Sandbia
nD
arr
iwili
an
Tom
mo
tA
tda
ba
n
Te
rre
ne
uvi
an
Ep
och
2
Ea
rly
Ca
mb
ria
n
525 Ma
516 Ma
509 Ma
Bo
tom
a -
To
yon
Mo
de
rate
(h
igh
?)
rev
ers
al
fre
qu
en
cy
Tom
mo
tA
tda
ba
nB
oto
ma
- T
oyo
n
Terr
en
eu
via
nE
po
ch 2
Ea
rly
Ca
mb
ria
n
Lo
w (
ve
ry l
ow
?)
rev
ers
al
fre
qu
en
cy
NN
S30°
S60°
экватор Е150°Е90°E30°
Kirschvink’s pole
Khramov’s pole
P-T
D3-C1
O2-O3
Cm3-O1
Cm2
Siberian APWP
N
NN
EARLY CAMBRIAN:
LONG STANDING CONROVERSY:
TWO PRIMARY POLES FOR ONE SIBERIAN PLATFORM?Kirschvink and Rozanov, 1984
Khramov et al., 1982
NN
N
SYNTHES: both directions are primary(i.e. have been recorded either during the formation of rocks or soon after).
But observed data can't be reconciled in the framework of the Geocentric Axial Dipole hypothesis!
Kirschvink’s direction Khramov’s direction?OR
Kirschvink and Rozanov, 1984
Pisarevsky et al., 1997
Pavlov et al., 2018
Pavlov et al.,unpubl.
To explain seemingly contradictory outcomes of the numerous paleomagnetic studies we consider a hypothesis of anomalous non-uniformitarian geomagnetic field during Early Camb- rian. In this case the geomagnetic field could be characterized by occurrence of two quasi-stable generation modes, which replaced each other in turn. The first mode would correspond to prolonged period during which an axial mostly mono-polar dipole field predominated. The second mode would correspond to relatively short epochs when a reversing circumpolar or midlatitude dipole predominated.
By the beginning of the Sandbian age (Late Llandeilo-Early Caradoc) geody-namo returns to “normal reversing state”, however, soon, the new long magnetic polarity interval (but of normal polarity) is, probably, established. Existence of this Late Ordovician - Early Silurian superchron would be in a good aggrement, with the hypothesis of “double - superchron” of Algeo (1996) and with the hypothesis of sudden transitions between geodynamo operation modes (Gallet and Pavlov, 2016). Further studies are needed to check these hypotheses.
Upper
Ord
ovi
cian
Cara
doc
Ash
gill
Hirnantia
n
Chert
ovs
kian
Baks
ania
n
Kudrino(Siberia)
Dolb
orian
Rozhkova(Siberia)
Almaly(Tienshan)
Gullhogen(Sweden)
Moyero(Siberia)
Botmoynak(Tianshan)
Khondelen (Siberia)
Toluk(Tianshan)
Regio
sta
ge
Series
Katia
nS
andbia
nM
ayan
Floi
an
Dopi
ngia
nDa
rriw
ilian
Sand
bian
Kat
ian
Hirn
an-
tian
Upper Cambrian
Mid
dle
Cam
bri
an
Mid
dle
Ord
ovic
ian
Am
gian
Toy
onA
tdab
anB
otom
aT
omm
ot
Low
er C
amb
rian
Silurian
Up
per
Ord
ovic
ian
Car
adoc
Low
er O
rdov
icia
n
Tre
mad
oc
Up
per
Cam
bri
an
Are
nig
Lla
nvi
rn
Lla
nd
eilo
Ash
gill
Rak
hm
etA
kta
yU
ngu
rB
atyr
bay
Ak
say
Sak
sA
yuso
kk
an526
510
499
499
Ma
485.4
477.7
443.8Ma
Superchron“Moyero”
Normalpolarity
Reversedpolarity
Anomalousinterval
Early Paleozoic Geomagnetic polarity time scale: tentative compilation
Ediacarian Middle Cambrian
458.4
Normal Reversing mode
Superchron mode
Hyper-Active Reversing mode
? ??
no data
?
0
2
4
6
8
10
0 100 200 300 400 500 600
Magnetic r
eve
rsal fr
equency
(re
v/M
yr)
Time (Ma)
Three Distinct Reversing Modes in the Geodynamo (Gallet and Pavlov, 2016)
The geodynamo operates in three distinct reversing modes: (i) a “normal” reversing mode generatinggeomagnetic polarity reversals according to a stationary random process, with on average a reversal rateof ~3 rev./Myr; (ii) a non-reversing “superchron” mode characterizing long time intervals without reversal;(iii) a hyper-active reversing mode characte-rized by an extreme geomagnetic reversal frequency. The transitions between the different reversing modes would be sudden, i.e. on the Myr time scale. We suggest that in the past, the occurrence of these transitions has been modulated by therma conditions at the core-mantle boundary governed by mantle dynamics.
Baykal Lake
Olekm
aLenaAngara
Ole
nek L
ena
Viluy
Viluy
Markha
Popigay
Fomich
Djogdjo
Magan
Pyas
ina
Kheta
Eni
sey
Kot
uy
Kotuykan
Nijnyaya TunguskaPodkamennaya Tunguska
Enisey Vitim
Aldan
Cretaceous
Jurassic
Permian and Triassic
Paleozoic
o70
o60
0100
0120
Precambrian
Turukhanskregion
Uchur-Mayaregion
EniseyRidge
Our sampling in the Siberian platform
Baykal Lake
Olekm
aLenaAngara
Ole
nek L
ena
Viluy
Viluy
Markha
Popigay
Fomich
Djogdjo
Magan
Pyas
ina
Kheta
Eni
sey
Kot
uy
Kotuykan
Nijnyaya TunguskaPodkamennaya Tunguska
Enisey Vitim
Aldan
Cretaceous
Jurassic
Permian and Triassic
Paleozoic
o70
o60
0100
0120
Precambrian
Kulumbe
Kudrino
Moyero
Rozhkova
Khorbusuonka
Location of main studied sections (Siberian platform)
Polovinka
Middle Lena
Khorbusuonka river section