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Jurassic and Cretaceous Magnetic Stratigraphy
Jurassic and Cretaceous Magnetic Stratigraphy
11.1 CretaceousMagnetic Stratigraphy The majority of Cretaceous magnetostratigraphic studies have been carried out on pelagic limestones in the Mediterranean region, following the pioneering work of Lowrie and Alvarez (1977a,b) on the Gubbio (Bottacione) section in Italy. The principal feature of Cretaceous geomagnetic polarity is the so-called Cretaceous long normal superchron, an interval of prolonged normal polarity lasting about 38 My, beginning just above the Barremian/ Aptian boundary and ending close to the Campanian/Santonian boundary (Fig. 11.1, Table 11.1).
a. K/T Boundary Magnetic Stratigraphy The position of the Cretaceous-Tertiary (K/T) boundary in the GPTS has always been of great interest because of the associated mass extinctions. The position of this boundary in magnetostratigraphic section was first determined at Gubbio (Bottacione) (Alvarez et al., 1977). Since then, the position of this boundary has been accurately determined in more than 14 magnetostratigraphic sections both in outcrop and deep-sea cores. The average position of the K/T boundary in these studies implies a correlation to C29r (0.75) (75% up from base of the reverse chron). However, the location of the boundary within the polarity zone correlative to C29r is not a good estimate of the position of boundary in time due to a substantially reduced sedimentation rate in the Paleocene part of C29r. Cyclostratigraphy 182
11.1 Cretaceous Magnetic Stratigraphy
| I]3
CRETACEOUS
Ma
20 24
22 \
/
'N
Ic3~
5
,/
13
26
II
74.5
84.0 86.3 88.7 93.3
98.5 ~
~
i Ic3,~
~
~
28
19
112.(
25 ....
i
121
12( 131.0 135.1
CM1
-i CMll
Z
N
~T]._.~s
m-CMI6
141
. ....
o~,7
N
i
_--~.
t
N
i
Figure 11.1 Summary of some of the more important Cretaceous magnetostratigraphic studies. For key, see Table 11.1.
184 Table 11.1 Cretaceous Rock unit 1
Scaglia
Lo Age Hi
Region
C29N-C34N
Italy. Guhhio Italy. Pogg10 Italy. Gorgo a. Cerhera Italy, Boss0
+43.37 +12.58
1
+14.51 +12.58
1
+43.56 + 12.53
2 Fucoid Mark
34N
3 Maiolica
CMO-CM10
4 Maiolica
CM13-CM19
5
C24-C34
Scaglia
6 Fucoid Mark
C34
7 Maiolica
CMO-CMI
8 Maiolica
CMO-CMI 1
9
Maiolica
CM15-CM19
10 Scaglia Rossa
C29-C34
11 Maiolica
CMO-CMI
12 Maiolica
CMO-CM16
13 Scaglia
C30-C34
14 Fucoid Mark
C34N
NSI
NSA
M
D
5-1 m
1
250
- J-I
52
3-4
2
.75-1 m
1
+12.53
1
Italy, Belluno Italy, Alhian. Contessa Italy Pie’Dosso Italy, Polveno Italy, Fonte Del Giordano Italy Moria
+46.00 +11.75
5
Italy Frontale Italy Capriolo Italy Italy Valdorhia
A
+43.56
Q,
NSE
78
RM
- I
DM
AD
A
A
V
V
NMZ NCh C R RT F.C.T. Q 13
6
22
R+
F+
6
References Lowrie and Alvarez (1977h) Lowrie er a/. (1980h)
A
V
F-V
I
1
-
-
F+
6
180
-
I
T
Z-V F-V
24
II
47
-
F+
7
Lowrie ef a/. (198Oa): Lowrie and Alvarez
.8 m
120
-
-
T
Z-V F-V
17
-
4
Lowrie and Channell
359
127
- -
T
-
5 Channell and Medizza
v
33
7 4 7 13
28
-
(1984)
(1984)
(1981)
+43.36 + I 2 5 6
I
72
+45.55 +10.11
3
1.5m
200
+ 10.05
3
1.5m
+43.30 +12.54
1
+43.50 +12.54
30
Tdl
T-A
Z-P
F-V
15
1
16
R-
-
6
Tarduno era/. (1992)
- I
TA
Z-P
F-V
34
11
41
R+
F+
9
200
- I
TA
Z-P
F-V
34
II
41
R+
F+
9
104
275
-
T
Z-B F-V
21
9
43
-
F+
7
Channell and Erha (1 992) Channell and Erba (1992) Cirilli era/. (1984)
1
250
340
- -
A
V
12
6
18
R+
F+
5
+43.56 + I 2 5 3
1
.75-1 m
1
130
- I
T
Z-V V
15
6 3 3 -
-
6
+45.60 +9.89
I
.3m
I
167
- -
T-A
Z-B V
41
-
5
+43.64 +12.71
1
450
1
300
- I
T-A
Z-V F-V
27
9 2 0 -
-
7
+14.43 112.71
3
24
4
30
- I
A
V
3
1 0 6 -
F+
5
+45.63
-
I
F-V
F-V
15
42
-
Alvarez and Lowrie ( 1978) Lowrie and Alvarez ( 19%) Channell er a/. (1987) Alvarez and Lowrie ( 1984) Lowrie er a/. (198Oh)
+43.56 + 12.53
1
7-1 m 1
+44.38 +4.25 +43.4 - .003.00 +46 +11.76
1 1
163 259
2
+ 46
C28-C32 C34-CM5 C26-C34
Italy Presale France Spain Italy Cismon Italy Cismon S. Atlantic N. Pacific S. Atlantic
Site 463 Site 516 Site 317 Point Loma fm Great Valley Gap Christopher Fm Hole 69OC Cehegin Aix-en-Provence
C34-CMO C29-C34 c34 C32-C33 c33-c34 C34-M 1 C29-C33 CM15-CM17 CM28-CM34
Pacific S. Atlantic C. Pacific USA (CA) USA (CA) Canada S. Atlantic Spain France
+21.36 -30.35 -15.2 +32 78 +40.00 + 80 - 65 +38.(!6 +33.5
Deccan Traps Sierra Geral
C29-C30 Early Cretaceous Haul- Alb E. EoceneTuronian
India Brazil
+20
15 Maiolica
MGM8
16 Berriasian Lmst. 17 Sopelana 18 Scaglia
CM14-CM19 C29N-C31R C33R-CM8
19 Maiolica
C33R-CM8
20 Hole 525A 21 Site 167 22 Hole 530A 23 24 25 26 27 28
Leg 103 Holes 752-755
Atlantic Indian Oc.
94
T
2-V F-V
15
9 4 7 -
-
6
13 X
5 4
Lowrie and Alvarez (1984) Galbrun (1985) Mary er a/. (1991) Channell el a/. (1979) Channell er a/. (1979)
I
1 1 1
394.
T-A Z-V F-V T-A 2-P F-V A B V
2
1
1
394.
A
B
-29.08 +02.99 +07.00 - 177.00 -19.19 -9.39
4
.3-.6 m 88 .35 m
1 1
133 120 630
A AT A
2-B I 2-P F-I 2-B I
+ I75 -35.18 -1468 - 117.29 -121.5 -92 +2 -1.81 +5.5
1 1 1
56
1 I 1 1
IM) 2x9
A A.T. A T A-T T-A A T T
2-P B Z-P Z-V 2-V Z-V 2-V 2-P 2-V
+11.76
+75 -18 - 56 -30 -48 +42.17 -12.17 -31 +93.83
1
I
3 9 6
2 2 33 3 20 6 4
180
74 45 252 76 .25 m 73
I
30 150
1
50 200 3000 IS00 70 12
110
1-4
1166
27 3
4-10 500
loo0
1.5 m 576
383
300
1
310
3 5 I
-
V
F-I I I
R+ R-
-
26
47 50 20
-
-
6 5 6
26
20
-
-
6
-
5 5 4
12 10
II 5 9 3
5 3 8 6 2 4 4 1 5 -
55 35
R+
-
-
-
Chave (1984) Tarduno er a/. (1989) Keating & HerreroBervera (1984) 5 Tarduno el a/. (1989) 3 Hamilton el a/. (1983) 5 Tarduno (1990) 8 Bannon er a/. (1989) 6 Verosub er a/. (1989) 7 Wynn er a/. (1988) 4 Hamilton (1990) 7 Ogg el a/. (1988) 5 Westphal and Durand (1990) 6 Vandamrne era/. (1991) 7 Ernesto et a/. (1990)
11
-
-
19
40
R+
-
5 7
2 0 1 6 3 5 1 01 2 24 2 4 6 3 05 3 0 7 2 72 6 2 5
V V F I F F
4 13
T.A. 2-P F T-A 2-V F
3 4
2 -
20 26
T-A T-A
2-P I 2-P I
3
3 5 11
-
-
-
-
R+ -
F+
-
F+
R+ -
-
-
-
Ogg (1988) Gee et a/. (1991)
185
| ~6
11 Jurassic and Cretaceous Magnetic Stratigraphy
based on carbonate content, color density, and magnetic susceptibility from South Atlantic cores and Spanish land sections was used to demonstrate that the boundary occurred in time almost exactly in the middle of C29r (Herbert and D'Hondt, 1990; Herbert et al., 1995). Nonmarine terrestrial sediments from the western United States (Butler et al., 1977, 1981b) as well as from Europe (Galbrun et al., 1993) have contributed to the debate concerning the faunal crisis at the end of the Cretaceous by demonstrating that extinctions of marine and nonmarine fauna were essentially synchronous (see Section 9.5).
b. Santonian-Maastrichtian Magnetic Stratigraphy The Late Cretaceous polarity zones at the young end of the Cretaceous long normal interval were recorded and correlated to foraminiferal biostratigraphy in the original Alvarez et al. (1977) study of the Gubbio (Bottacione) section (Fig. 11.2) Subsequent nannofossil biostratigraphy at Gubbio (Monechi and Thierstein, 1985) has provided a correlation of these polarity chrons to nannofossil zones (Fig. 11.3). The correlations of polarity chrons to nannofossil and foraminiferal biozonations at Gubbio have been ratified and refined in the Southern Alps (Channell and Medizza, 1981), Spain (Mary et al., 1991), and in cores from the NW Pacific (Monechi et al., 1985) and South Atlantic (Hamilton et al., 1983; Chave, 1984; Tauxe et al., 1983c; Poore et al., 1984; Keating and Herrero-Bervera, 1984). Due to the scarcity of ammonites in the pelagic limestone sections, polarity chrons are generally correlated to the ammonite-bearing stage stratotype sections through the micropaleontology. Direct correlation of the GPTS to European Upper Cretaceous ammonite zones which define stage boundaries has not been achieved, although the C33r/C33n polarity chron boundary has been correlated to ammonite biostratigraphy in Wyoming (Hicks et aL, 1995).
c. Cretaceous Long Normal From paleomagnetic data available at the time, Helsley and Steiner (1969) postulated the existence of an interval of constant normal polarity from Late Aptian to middle Santonian which could be correlated to long smooth intervals in coeval oceanic magnetic anomaly records (Raft, 1966; Heirtzler et aL, 1968). The presence of this long interval of normal polarity was confirmed by Keating et al. (1975) from deep-sea cores obtained from the Deep Sea Drilling Project (DSDP). Subsequent studies in Italian pelagic limestones resulted in correlation of the top of the quiet zone (base of C34r) to the early Campanian, just above the base of the G l o b o t r u n c a n a elevata foraminiferal zone (Alvarez et al., 1977;
11.1 Cretaceous Magnetic Stratigraphy
] 87
PALEONTOLOGICAL
LITHOLOGY
POLARITY
VGP LATITUDE
-90
0
+90
ZONES
Planktonic ]Calcareous _foraminiferaI nannofossils
Globigerina I = eu_cluDina %,j
STAGE
Pa[eo(ene
Abathompha!us mayaroensls i
MAASTRICHTIAN
GIt. g a n s s e r i
GIt. tricarinata GIt. calcarata
CAMPAN-
GIt. elevata
IAN
r
=-"~
O
,m
GIt. concavata carinata
..{3
SANTONIAN
GIt. concavata concavata
(.9
[ONIACIAN
ql=~
GIt. schneegansi
,,,
TLIRONIAN
GIt. helvetica ~.H. lehmanni rRtl. cushmani
(notzoned)
Planomalina buxtorfi T. breggiensis
o~-,.===
~ "
G. blowi H. similis
Eiffellithus turriseiffeli
_.J _R _cretace~--L _ Parhabdofithus
augustus : Chiastozygus " litterarius
Micranthofithus obtusus
Lithraphidites bollii
limestone
II
normal
marl
~
reverse
~
CENOMANIAN
BIAN APTIAN
BARREM IAN
HAUTERIVIAN
hiatus
Figure 11.2 Summary of Cretaceous magnetostratigraphic studies at Gubbio and Cismon (Italy) (after Lowrie et al., 1980b).
| 88
E
11 Jurassic and Cretaceous Magnetic Stratigraphy
~~ .~ ~
500- ,~ii ~
CALCAREOUS
POLARITY CHRONS
EVENT
44O
-
top C grandis (484m)
Ii
20r
420
•
CPI2
280 9 z r
P8
lY r base M arag~
--i
I
~tYmp:ff:Tmi:.ii~top_iRpseudomenardii I
~a: DI-I~le~nl~ll~3~32?)m) " ' ~ "P, OaseP. pseudomenardii (364~7"/ -~ ~ }
ase F. n is (36 .5 - base E maceltus (354m) --.C~2, -.base C danicus (350.5_m). -'CPI' -top C r e t a c e o u s (347.6m)NC23 - base M. murus (337.9m)
- base L. quadratus ~326m)
NC21 !
- top 77.trifidus (302m)
I 32r
~
'
- base T trifidus (264m)
z z
_ top E. eximius (253m) .- base T gothicus (250m)
33n
I
,
base G. gansserl (302m)
MC$8
Z
~
" top G. calarata (2ZO.2m) base G. calarata (264m)
NCl9o
P-"
,r
,ru~
' i :~ L
--
~
Z ; 'r
MCs7
" . base B. parco (209m)
NCl8 ~
,
_,1
9
.
.
.
.
.
.
.
~1
i
~uul
5
U
! base Giobotruncana elevata (196m);,
NC17
or} ~
~Z
- base C. oculeu~ (222m) 33r
-r"
Z
z z
220- .,=1=,=
MCIIO ~
NC19b
--~ ~J ~ ~ I ~ ~. 1 "" ~
base A mayaroensis (330m) ~ base G. contusa (325 5m) --
I~20 MCs9
zx
260- z
I
~,1~=" base M. angulata (359m) .~"Pt--" base M. uncinata (356. 5m) ~ PI -~'base S. trinidaclensis ( 3 5 3 m ) ~ =--"~,base S pseudobuiloicfes (348m~ MCsll base G. eugubina (3476m) /
~lC22 ~ ~
31r
34n ....
(3998m) - - ~
I-base O. diastypus (386m) "'~pa L _ / top M edgari (382m) "~ ~..base D. multiradiatus (378 5m~,,,j.p r ' ' / t o p lld. velascoensis ( 3 7 6 r n ) \
24r . . . .
r
z 240. z
base G. palmeroe (418.5m)
CP 9 p 6
31n i
t
i
base T. orthostylus (398m)
32n
~
i
CPIO!-- base G. taroubaensis (408 7m) - -.
29r 30n
i
I
base Hantkenina sp. (429m) _ . . _ ~
base D. Iodoensis (402m)
340
~,J
----
iP 9
22r ~ -
360
i
- P1 I
23r ~
25r
300, m =
-
base N fulgens (445m)
i~
~i
base O sublocloensis (417. 5m) base C crassus (414m) ~
26r/ 27r
320- ~ i~
'
,
P1] - - - - - - - P12 o M CP13 ~ t p . aragonensis (453m)
base R. umbilica (463m)
. ~
380
EVENT
CPI~I~ P ~ " base G. semiinvoluta (489m) --.. --
L 21r I
400 "="-=
,
STAGE
CPI4
I
~
~ ZONE, ,
basetrecurvus(50'm) CPl~Pls
'' 16r
9
FORAMINIFERA
ZONE
480 ~i~ 18r/ t z~x~: 19r 460 i
PLANKTONIC
NANNOFOSSILS
Z
~ .
.
Correlation of Late Cretaceous-Eocene calcareous nannofossil and planktonic foraminiferal events/zones to polarity chrons at Gubbio, Italy (after Monechi and Thierstein, 1985).
Figure 1 1 . 3
11.1 Cretaceous Magnetic Stratigraphy
| ~q
Lowrie and Alvarez, 1977a,b; Channell et al., 1979; Channell and Medizza, 1981) (Fig. 11.2). The entire Cretaceous long normal interval has been recorded in the Cismon section (northern Italy) and here the reverse polarity chron at its base (CM0) is close to the Barremian/Aptian boundary (Channell et al., 1979) (Fig. 11.2). The base of CM0 has since been found to immediately postdate the first occurrence (FO) of nannofossil R. irregularis in two Italian land sections (Capriolo and Pie' del Dosso) (Channell and Erba, 1992) and at ODP Site 641 on the Galicia margin (Ogg, 1988). In the absence of the ammonite Deshayesites, which formally defines the Barremian/Aptian boundary, the FO of R. irregularis is considered the most reliable microfossil marker for this stage boundary. The base of CM0 is usually close to but slightly younger than this nannofossil event. There are a number of magnetostratigraphic records of post-CM0 Aptian-Albian reverse polarity chrons. The first such observation in outcrop was by Lowrie et al. (1980a), who observed a reversely magnetized bed in the Late Aptian Globigerinelloids algerianus zone at Valdorbia (Umbria, central Italy). This so-called ISEA reverse polarity zone (Fig. 11.4), also known as polarity chron C M - 1 (minus 1), was not observed at two other sections in Umbria where the same foraminiferal zone was present in comparable or greater stratigraphic thickness; however, Tarduno et al. (1989) observed two samples with reverse magnetizations just above the FO of G. algerianus at DSDP Site 463. The documentation of this short reverse polarity chron is strengthened by two samples with reverse magnetization spanning 43 cm in a core from ODP Site 765 (Ogg et al., 1991b), where the reverse polarity zone postdates CM0 and is late Aptian in age. Seven reverse polarity zones have been observed by Tarduno et al. (1992) in the middle Albian interval (Fig. 11.4) (A. albianus nannofossil zone and top Ticinella primula to base Biticinella breggiensis foraminiferal zones) at the Contessa section near Gubbio (Umbria, central Italy). In these reverse polarity zones, the magnetization is carried by hematite and the reddening of the sediment may be late diagenetic in origin. The reverse magnetization components in this interval are not antipodal to the normal magnetization components, and the reverse directions are offset toward directions consistent with the Late Cretaceous or Paleogene. The duration of the proposed middle Albian polarity zones is well known from lithologic cyclostratigraphy (see Herbert et al., 1995, and references therein). Of the seven polarity zones recognized by Tarduno et al. (1992), the thickest (3.25 m) represents about 800 ky. This duration is greater than that estimated for reverse chron CM0 and about twice that estimated for CM1 (see Herbert, 1992), both of which are usually recognized by shipboard magnetic anomaly surveys. It is, therefore, doubtful that these middle Albian reverse
| 90
11 Jurassic and Cretaceous Magnetic Stratigraphy
CEN 198"5
PLANKTONIC FORAMINIFERS
CALCAREOUS NANNOFOSSILS
{3)
~=
R. brotzeni
i~
LO R. irregularis L~ F O E . turriseiffefii
m E
OA
EIc
F O P . achlyostaurion FO "small" Eiffellithus
z
!
R. ticinensis ~_ R. subticinensis
~
.o
.J <
FO R. appenninica FO R. ticinensis F O R . subticinensis
T. praeticinensis F O B . breggiensis
T. primula FO A. albianus FO 7. orionatus
H. rischi
E 112.0
F O R . brotzeni
R. appenninica
B
~
.......... OAE1 b ~ H. planispira ..........
FO C. ehrenbergii F O P . columnata
FO T. primula LO T. bejaouaensis
T. bejaouaensis LO M. hoschulzii LO N. steinmannii
Z
N. truittii
H. trocoidea
acme
G. algerianus
<
F O G . algerianus
FO C. achylosum
G. ferreolensis
FO B. africana
L. cabri
9FO E. floralis F O R . angustus FO F. oblongus
121.0
i (N3
rr
FO T. bejaouaensis LO G. algerianus
FO L. cabri
(~Ela
~4-- n
Nannoconid "crisis"
G. blowi ..........
.~:
a~
LO L. cabri
G. duboisi kO C. oblongata
F O G . blowi F O G . duboisi
notzoned
(3~,15
~
~
LO L. bol//i
Figure 11.4 Correlation of mid-Cretaceous calcareous nannofossil and planktonic foraminiferal events to polarity chrons (after Larson et aL, 1993).
polarity zones represent the geomagnetic field at the time of deposition of the sediments. Until the middle Albian reverse polarity chrons are recognized elsewhere, we consider that they should not be incorporated into the geomagnetic polarity time scale (GPTS).
11.1 Cretaceous Magnetic Stratigraphy
|9|
d. Berriasian-Aptian Magnetic Stratigraphy "M-sequence" polarity chrons are numbered according to the correlative oceanic magnetic anomaly. These anomaly numbers, by tradition, correlate to reverse polarity chrons except for M2 and M4, which correlate to a normal polarity chrons. We use a prefix "C" to distinguish polarity chrons from magnetic anomalies and follow Harland et al. (1982) in labeling normal polarity chrons (other than CM2 and CM4) using the number of the next older polarity chron with the appendage "n." Using this nomenclature, CM9 denotes the reverse polarity chron correlative to magnetic anomaly M9 and CM9n denotes the normal polarity chron between CM9 and CMS. It should be noted the magnetic anomaly between M10 and M l l is labeled M10N. This anomaly was originally omitted from M-sequence anomalies (Larson and Pitman, 1972) and was included by Larson and Hilde (1975) and designated M10N after Fred Naugler, co-chief scientist of the NOAA Western Pacific Geotraverse Project. Land section magnetic stratigraphy in the Mediterranean region has been the basis for the correlation of the M-sequence polarity chrons to biozonations and hence to geologic stage boundaries. The oceanic magnetic anomaly record from the Hawaiian lineations (Larson and Hilde, 1975) remains the template for the M-sequence polarity pattern. Some pelagic limestone sections in Italy have recorded substantial portions of the Msequence pattern. Notable among these sections are Gorgo a Cerbara (CM0-CM9) (Lowrie and Alvarez, 1984), Polaveno (CM3-CM16) (Fig. 11.5) (Channell and Erba, 1992; Channell et al., 1995b), Capriolo (CM8CM16) (Channell et al., 1987), and Bosso (CM14-CM19) (Lowrie and Channell, 1984) (see Fig. 11.1, Table 11.1). It is remarkable that the polarity pattern derived by Larson and Hilde (1975) from Hawaiian oceanic magnetic anomalies has been confirmed time and time again by these land section studies, particularly in the CM0-CM19 interval. The only polarity chron observed in land section which is not included in the Larson and Hilde (1975) polarity pattern is a second reverse subchron between C M l l and CM12. These two subchrons were recognized at Capriolo (Italy) (Channell et al., 1987) and have also now been observed in the oceanic magnetic anomaly record (Tamaki and Larson, 1988). The vast majority of the magnetostratigraphic studies in the CM0CM19 interval have been carried out in the Maiolica Limestone Formation of Italy. This is a Tithonian to Aptian white/gray thin bedded magnetitebearing pelagic limestone with fairly constant sedimentation rates (typically --~15 m/My), thereby aiding the recognition of polarity zone patterns. The biostratigraphic control in the Maiolica is mainly from calpionellids for the
Polaveno
Lithology
Nannofossil Eventsand Zones
Polarity Chrons
z ,~ <_
i5o i 'i i--!.ii-'-~.ii 'i.i--.ii 'i..i........ 'i'i~!-.i.'i i .i i .i.il
C M 3 C. oblongata
~
1:
!
......
en .........
!00
...........................................................
............
L. b o l l i i
CM5
"
CM7 i
.
.
.
.
.
.
i
.
150
R. terebrodentarius
,
9 C. cuvilleri
CM9
t ....
L. bollii
CM'~ON t.
.
N. bucheri
oo ....
T. verenae
~
--
o
8~ t. . . .
CM12 _'1~ - ~ ~
~ . . . . . il ......
. . . .
! .
.
.i. 11... " _ , i - . . .... ~ ~. . . . . . . . . . .. :
i
T. verenae
C. oblongata Calpionellites d a r d e d
CM~5
0
40
z
<
z
~_ z
. . . . . . . . .
T=
.~
R. fenestratus
t ....... C. angustiforatus
-40
~
CM113 I
t
-80
o
~ .
80
VGP Latitude (o) Figure 11.5 Virtual geomagnetic polar (VGP) latitudes from the Polaveno section (Italy), correlation to the GPTS, and correlation to nannofossil and calpionellid events (after Channell and Erba, 1992; Channell e t al., 1995b). In the lithologic log, F indicates small faults (with minimal offset), speckles indicate cherty intervals, diagonals indicate marly interval, and black bars indicate black shales. Horizontal thin bars indicate pelagic limestone, the dominant lithology.
11.1 Cretaceous Magnetic Stratigraphy
| 9~
Tithonian and Berriasian and from calcareous nannofossils for Tithonian tq Aptian. It has been demonstrated in numerous Maiolica sections that polarity chrons correlate consistently to nannofossil events (Fig. 11.6) and calpionellid events (Fig. 11.7). For correlations to calpionellids, see Channell and Grandesso (1987) and Ogg et al. (1991c); for correlations to nannofossils see Bralower (1987), Channell et al. (1987, 1993), Bralower et al. (1989), Ogg et al. (1991b), and Channell and Erba (1992). The result of these studies is that the combination of nannofossil or calpionellid biostratigraphy and magnetic stratigraphy gives a very precise and useful integrated stratigraphic tool for pelagic limestones of this age. Even for short sections where polarity zone patterns are not distinctive, the nannofossil/calpionellid events indicate the approximate stratigraphic position relative to the GPTS, and the magnetic stratigraphy then gives precise stratigraphic control. Although the correlation of polarity chrons to nannofossils and calpionellids is firmly established, the correlation to stage boundaries requires correlation to ammonite zones. Although ammonites are very rare in the Maiolica limestones, recent finds place the Hauterivian/Barremian boundary in the upper (younger) part of CM4 (Cecca et al., 1994) and the Valanginian/ Hauterivian boundary at the young end of C M l l (Channell et al., 1995b) (Fig. 11.6). Previous estimates of the correlation of these stage boundaries to polarity chrons relied on the correlation of nannofossil events to ammonite zones from Thierstein (1973, 1976). For the Berriasian-Valanginian boundary, the relevant ammonite zonal boundary has been correlated directly to CM15n at Cehegin (Spain) (Ogg et al., 1988). For the Jurassic/ Cretaceous (Tithonian/Berriasian) boundary, there are two alternative definitions with respect to ammonite zones, with no clear consensus. In the Tethyan realm, the boundary lies either at the B. grandis/B. ]acobi zonal boundary or at the underlying B. jacobi/Durangites zonal boundary. At Carcabuey (Spain), the B. jacobi/Durangites zonal boundary lies in a normal polarity chron at the top of the section, which is interpreted as CM19n (Ogg et al., 1984). Elsewhere, nannofossil and calpionellid events in the vicinity of the Jurassic/Cretaceous boundary have been consistently correlated to polarity chrons in land sections and deep-sea cores (Lowrie and Channell, 1984; Cirilli et al., 1984; Channell and Grandesso, 1987; Bralower et al., 1989; Ogg et al., 1991c). These studies imply that the Jurassic/Cretaceous boundary lies in the upper part of CM19n or at the CM19n/CM18 polarity chron boundary, and it has been advocated that this polarity chron boundary be used to define the stage boundary (Ogg and Lowrie, 1986). At Berrias (France), the Berriasian stratotype section yielded a magnetic stratigraphy that is correlated to calpionellids, nannofossils, and ammonite zones (Galbrun, 1985; Bralower et al., 1989); however, the base of the section is within the B. grandis zone and
194
11 Jurassic and Cretaceous Magnetic Stratigraphy
POLARITY CHRON
Ma
. .1 2.o .
CALCAREOUS NANNOFOSSILS
.,
"--" -
CM~
CM1
-
--
Nannoconid crisis ~
---r
[]~
~ F. oblongus R. irregularis
~
125 CM3
-- CM4 "-'~r--
AMMONITES POLARITY ZONES SUBZONES STAGES CHRON
m
]-"1C. oblongata ]--1L. be/Ill
~Rterebrodentarlus 7C." cuvillieri -1 CM10 i "j]-J L. boIlii
D. weissi ~ D. tuakyricus _ ~ - C.'s,~ a'ra"si_ ~_ il. airaudi ,(i) H. feraudi ca. H. sartusi = , A.vandenheckei H. caillaudi ._ "S, nicklesi , ~ S. hu(:Jii ' .9o P.ancjulicostata P. catulloi P.angulicoit. B. balearis- P.'li,qatus" e"
"-t--c I-- 8
--
CM1 -CM11A - ~ - CM12
L. nodosoplicatum
_
,
'j_.j T. verenae
--
--
CM1
51,.~
N. pachvdicranus
'
~_j p. fenestrata
T. pertransiens otopeta
m7uR. nebulosusL..F, boissieri j_Jc. angustiforatus _ CM16 0_.t = - ' ' - ' - ' -
1
J
CM17
~
~
CM18 ~
N. St. steinmannii i " C. cuvillieri ~ ~'
"I-JN._ stoinm, minor
Ii
mmll
C. mex. minor
t1" ,
m z .
I
or ~
,
M~
CM1
CM4 C~M7
CM10
I
~--CM10N ~ z i ~: ~ 9 ~
UM11A 9 , CM 12
.r.
i
alpillensi$
B. picteti ~ m - ~ - i.paramimouna ~" ~-CM16 (/) ,
T. occitanica
D. dalmasi B. privasensis
<{: ~
T.subalpina i ~
i
io m,
~
B~aco~l
Durangites
~
~=
P. transitoris
Simplisphinctes
B. peroni
g. aa'mTr~n d-um /
R. richteri
l
z ~ ,,,
X
_ B. grandis. . . . . . .
--' ' ~ - ' ~ l N. colomiin i-1 i, CM19 ~ "J R./aline,~ L_LjI -U. gr. granulosa ' 7J. ...J carniolensis i JM.L.chiastius -~J C. mex. mexicana 17 145 c a 2 0 ~ ----'-I _ P. beckmannfl L...u j ~_j P. embergeri CM21 ~ CM22
H. trinoclosurn
S. verrucosum B. campylotoxus
3S~TM~4"mt'j-JC. oblongata ~
C. Ioryi A. radiates
<
o.~~~_. =o. ~. ~ ~ T< 'r
S. sayni
.CMlON=~J---iN'bucheril T. verenae
z.
"~ ~ ~)
/ S . biruncinatum
:~
~ E
CM17
CM18
i
CM19 CM20 1 CM21
V~all~ed[n~m:
H. hybonotum
CM22
kl "
"
x
11.6 Summary of correlation of Oxfordian to Aptian polarity chrons to nannofossil events/zones and ammonite zones. Open bars indicate the range of the nannofossil events with respect to polarity chrons (from Channell et al., 1995a). Figure
11.1 Cretaceous Magnetic Stratigraphy
] 95
~mmonite Calpionellid Zone zone i event ~ P ~
Stage
Busnardoiles
>
T" P ~ r t r a n s i e n s
]
I7ili!ii7i7777!i,~~C.
T. otopeta -_......................
9
B. callisto
da~ri
CM14
=
~ h
D
P. pecteti
" ung;'rica
CM15
:i:!:i:iiii
Z<~ .paramimounum ........B................. ~:~....:~:I--'C. r~C ~ oblon~ CM 16
h'q <
::::::::::::::::::::::::::::::::J .
O. d a l m u i :::::::::::::::::::::::::::::::::::::::::::::::::
simplex
C
~
B. privasensis ................................. :!:i:i:7:7:7:i:~:7:7:7:7:7:7:7:7:7:7:7:7:7:7:7:7:! :i:!:i:i:i:i:i:i:i:i:!:!:!:{:i:i
.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:
,~'IC. elliplica
B. grandis .......
. ferasini
:ii!i!i!i!iiiiiii!i!i!i!i!iiiiiiiiiiiii!iiiiiiiiii::::::::::::::::::::: i:i:i:!:i:!:!:!:i:::::::::::::::::::::::::::::::: :::::::::::::::::::::::::::::::: ....._ ....... ._.~:::::::::::::::::::::::::::: :, .
.
.
.
.
.
.
i
.
CM18
-
!iii!iiiiiii!i!i!i!!i!!!i!iiiiii!
Z
........o:.,._..~,,,:.......
~)
Sid~l,s;Uincteg::i!::::::::::i:i i i :2i!i;~l.
I-
S ~.;~o;'.:;umChit" I ~,
A
I c-='"n~ ~
,,
:::::::::::::::~.:E:::::-::::::::::::............... T. L'arpathicaT'T B. peroni
s. biruncinatum R richteri
( ~ 20
C. bone. t~,.
~
~I~Chitinoidell,
(3vi21
BB
H. verruciferum
Figure11.7 Correlation of calpionellid events to polarity chrons (after Channell and Grandesso, 1987; Ogg et aL, 1991c).
therefore the section does not include either of the two definitions of the Jurassic/Cretaceous boundary. Ogg et al. (1991c) have identified CM17 in the Purbeck Limestone of southern Britain, providing a first M-sequence magnetostratigraphic correlation out of the Tethyan into the Boreal Realm.
196
11 Jurassic and Cretaceous Magnetic Stratigraphy
11.2 JurassicMagnetic Stratigraphy a. Kimmeridgian-Tithonian Magnetic Stratigraphy As for the Early Cretaceous (CM0-CM18), the Larson and Hilde (1975) oceanic magnetic anomaly block model is the template for geomagnetic polarity in the Tithonian and Kimmeridgian stages of the Jurassic (CM18CM25). Subsequent extension of the oceanic anomaly block model to M29 (Cande et al., 1978), and to M38 (Handschumacher et al., 1988) has extended the record into the middle Jurassic interval. Land section magnetic stratigraphies have been correlated to CM18-CM25; however, correlations to older M-sequence chrons and between-section pre-Kimmeridgian correlations have not been adequately achieved (Fig. 11.8, Table 11.2). The problem for pre-Kimmeridgian magnetic stratigraphy is twofold. First, preKimmeridgian calcareous nannofossil biostratigraphy does not yet allow precise correlation among Tethyan sections; and second, pre-Kimmeridgian Jurassic facies in the Tethyan realm are often highly condensed and/or highly siliceous. The oldest polarity chron recorded by the Maiolica Limestones of Italy is CM19. The Maiolica limestones are usually underlain either by siliceous limestones (Calcari Diasprigni) or by condensed nodular limestones (Ammonitico Rosso). The Sierra Gorda and Carcabuey sections of southern Spain are the key sections for the correlation of CM19-CM25 to ammonite zones (Ogg et al., 1984). In these sections, the "Ammonitico Rosso"-type sediments have mean sedimentation rates of 2-3 m/My. The polarity patterns are distorted by variable sedimentation rates and it is not easy to correlate polarity zones to polarity chrons. Nonetheless, the correlations of Ogg et al. (1984) place the H. beckeri/H, hybonatum ammonite zonal boundary which defines the Kimmeridgian/Tithonian boundary in CM23n, and the I. planula/S, platynota zonal boundary which defines the Oxfordian/ Kimmeridgian boundary in CM25 (Fig. 11.6). Ammonites are lacking in this interval in the Belluno Basin and Trento Plateau (Southern Alps, Italy), where the Oxfordian/Kimmeridgian and Kimmeridgian/Tithonian boundaries lie in the unsubdivided "Saccocoma Zone." The lack of calpionellid or other microfossil events in the Italian sections precludes the accurate definition of these boundaries; however, the polarity zone pattern in these sections is more readable than in the Spanish sections. Estimates of
Figure 11.8 Summaryof some of the more important Jurassic magnetostratigraphic studies. For key, see Table 11.2.
JURASSIC 14
Composite (Ma) ~---144.2 r cO c-
10
54.1
mm
C
EE m
,.,..
0 X
,-m
0 --159.4 c"
m mm
> 0
64.4 r-
6
11
tor
--169.2 C o 0
n~
-s ---<180.1 c o~
12
15
17
.0
.d
0O r .m m
m m
II
13"195.3 E C
II
03 --.201.9
7"
198 Table 11.2 Jurassic Rock unit
Lo Age Hi
Region
@
A
NSE
NSI
NSA
M
D
RM
DM
AD
A
NMZ NCh %R RT
1
13
-
-
T
Z-P
F-D-I
21
-
60
- I
T-A Z-V F-D-I
15
-
SO
F.C.T
Q
References
R-
6
R+ -
7
Steiner era/. (1989) Galbrun ef a/. (1988a) Ogg er a/. (1984) Channel1 er a/. (1990a) Steiner ef a/. (1987) Homer and Heller (1983) Witte era/. (1991) Channell era/. (1987) Steiner er a/. (1985) Steiner er a/. (1987) Homer and Heller (1983) Steiner and Ogg (1988) Channell era/. (1982b) Marton er a/. (1980)
1 Marine Magnetic
Anomalies 2 Sierra Harana
Spain
+37.2
-3.7
1
3 Toarcian
Bathoniard Bajocian Toarcian
France
+47.W
-.02
2
.I m
1
5
4 Carcabuey 5 Ammonitico-Rosso
CM18-CM25 Ox-Callo.
Spain Italy
+37.5
-3.3 +I1
2 3
.I m .05 m
1
1
10 10
- - -
T T
Z-V FV Z-P V
28 55
6
+46
-
4 0 R + 32 - -
6 6
6 La Fuente
Bathe.-Bajo.
Spain
+37.5
-3.3
2
1
10
- -
T
Z-P
19
-
42
R + F+
8
7 Breggia
Baj.-Car.
Switzerland
+45.87 + 9
2
I
120
- I
T-A Z-V F-V
82
-
47
-
-
7
USA Italy
+40.25 -75.25 +45.7 f11.46
3 1
4 139
5 1
4180 60
T Z-P FV T-A Z-B V
1
- -
25
1 9
0 52
-
R + F+ F+
9 5
105
1
13
- -
T
Z-P
F-D-I
22
4
54
R-
F+
7
-
-
T
Z-P
F-D-I
51
-
41
-
F+
8
82
-
47
-
-
7
D-l
14
-
62
-
C+
6
-
17
6
4 9 - -
11
-
55
8 Newark Supergroup Het-Carnian 9 Xausa CM14-CM23
106
9
9
.2 m
10 Aquilon
L,Oxfordian M Spain
+41.3
-l.W
5
11 Carcabuey
Bath-Aal
Spain
+37.5
-3.3
2
.I5 m
1
33
12 A l p Turati
Ba-Car.
Switz
+45.87
+9
2
.2 m
1
120
1-13.5
13 Kandelbach Grab.
Sin:Het.
Austria
+4.7
14 Foza
Ber.-Kim
Italy
+45.54 +13.5
15 Bakonyncoke
Pliens
Hungary
+47.1
+I8
3
169
I
3 9 0
1
1
.I m
1
24 -
K
I
- I
T-A Z-V F-V
- -
T
- I
T-A -
8.9 - I
F-D-I
T
B
Z-V V
R-
2 -
5
16 Quero
Titho
Italy
17 Cingoli
Pleins-Sinme
Italy
+43.33
18 Frisoni
ritho-Kimm
Italy
+4.5.53
Ammonitico-Rosso
L Toarcian E
Spain
+ 37.39 -3.49
Kayenta Fm.
Pliensbachian
USA
+38.6
-109.6
101
Krakow Uplands La Luna
M.Ox. E.. Call. Sant. Sen
Poland Veneiuela
+SO.I +Y.Y
+I9 6 -61.0
204 48
1
Lebombo Grp. Morrison Fm.
E. Jurassic Kim-Ox
S. Africa USA
-24 +3X.13
+31.75 -108.21
25 215
4s 1
6000
Morrison Fm
Kim-Tith
IJSA
+MI
-10x.z
I
1
Purbeck Ls. Sierra Gerral
Ber.-Tith
England
-2.24
I
I
Sierra Paloma Summerville & Curtis Fm. Umbria
+SIM
1
I
74
+I321
1
64
20
+ 11.33
I
132
xn
Brazil
-
-
Toarcian
Spain
+40.65
- 1.1
Callovian
USA
+3x.x
-111.1
TithonianToar.
Italy
+43.33
+I3
.I3
I
1
50
1
1
20 I00
I
.3 7x ~
~
T
Z-B
T
V
6
4
39
6
Z-V F-V
16
-
5x
6
T
Z-B V
IX
7
47
6
T
%-P F ~ D - I 21
53
R
6
T
-V
IY
R+ -
5 7 7
D-l
8 ~
R+ -
A
63
~~
4
30 7x
T Z-P T-A Z-P
F F-D-I
A-T B T V
F D-I
165
T
Z-V
F-D-I
XI1
1I15 -
T
V
F-D-I
33
I07 50
8.5
I
K
A
~
~
19
5
-~~
~
6 4
R+ - -
4
5 ~
Channell and Grandcsso ( 1987) Channell el a / . (19@) Channell and Grandcsso (1987) Galhrun er a1 (1990) Steiner and Helslcy (1974)
Ogg e r n / . (19Yla) Ca.itillo er a / . (1991) Henthorn (1981) Steincr and Helsley ( 1 9 7 5 ) Strmer and Helslcy (197Sb) O g g r r a l . (1991~) Valencio er a / . (1983)
47
1
75
T
Z-V V
4s7
I
120
T
V
1
2IN
T
Z-B F-V
5
I
F
14
3h
4
Y
92
5
Galhrun er a1 (IYXXh) Steiner (197Xi
14
14
h
Channell (19x4)
YI
ul.
199
~00
11 Jurassic and Cretaceous Magnetic Stratigraphy
the location of the Kimmeridgian/Tithonian boundary in the Italian sections place it in CM22 (Ogg et al., 1984; Channell and Grandesso, 1987). Early work on Jurassic magnetic stratigraphy was carried out on the Kimmeridgian-Oxfordian Morrison Formation in Colorado (Steiner and Helsley, 1975a) and the Callovian Summerville and Curtis formations in Utah (Steiner, 1978). Correlation to European sections is hindered by poor biostratigraphy in these terrestrial and near-shore sediments, complex magnetic behavior which compromises the fidelity of the magnetostratigraphic records, and variable sedimentation rates which distort the polarity zone pattern. Steiner et al. (1994) have made the case that magnetic stratigraphy can be used as a means of correlation in the Morrison Formation in Colorado and New Mexico.
b. Oxfordian-Callovian Magnetic Stratigraphy The correlations of European land section magnetic stratigraphies to M0M25 oceanic magnetic anomalies are fairly robust; however, magnetostratigraphic correlation to M26-M38 has not been well established. CM26 to CM30 have been correlated to Oxfordian ammonite zones in northern Spain (Steiner et al., 1985/1986; Ju~irez et al., 1994, 1995); however, the correlation between land sections and oceanic anomaly records remains somewhat tenuous. The difficulty in correlation is partly a result of discontinuous and low mean sedimentation rates (---1-3 m/My) in the condensed limestone facies. Similarly condensed Callovian-Oxfordian sediments in Monti Lessini (northern Italy) yield polarity reversals and sporadic ammonite control (Channell et al., 1990a) but the polarity pattern cannot be correlated to the oceanic magnetic anomaly record. The existence of polarity reversals in the Callovian-Oxfordian is confirmed by studies of short sections from the Krakow Uplands (Poland) (Ogg et aL, 1991a); however, here again the lack of long, continuously deposited sedimentary sections does not allow a convincing correlation to the oceanic anomaly record. Although the magnetostratigraphic correlation to the M26-M38 oceanic magnetic anomaly record has not been achieved, it is clear that the Jurassic "quiet zone" in the central Atlantic magnetic anomaly record is not due to a prolonged interval of normal polarity, as had been implied by magnetostratigraphic study of the Valdorbia section (central Italy) (Channell et al., 1984). It is now clear that the Callovian-Oxfordian interval, which correlates to the Jurassic quiet zone, was an interval of frequent polarity reversal (Fig. 11.8, Table 11.2).
c. Pre-Caliovian Jurassic Magnetic Stratigraphy For the Bajocian and Bathonian, several sections from southern Spain indicate a very high frequency of polarity reversal (Steiner et al., 1987), an
11.2
Jurassic Magnetic Stratigraphy
20|
average reversal rate of at least 5.5 reversals/My for the Bajocian. The mean sedimentation rate in these sections is in the 1-4 m/My range. The high frequency of reversal and the lack of any discernable "fingerprint" in the polarity zone patterns have precluded clear correlation among land sections. The elucidation of the magnetic stratigraphy in this interval will be aided by studies of more expanded sections. Such sections occur in central Italy but they lack ammonites and therefore await refinement of nannofossil and radiolarian biostratigraphies in this interval. One of the most important magnetostratigraphic studies in the Jurassic is that of Horner and Heller (1983) from the Breggia section (southern Switzerland) (Fig. 11.9). The sedimentation rates in the nodular limestones at Breggia are about 14 m/My for the Pliensbachian and 4-7 m/My of the Toarcian and Aalenian. These sedimentation rates are several times greater than for more typical Ammonitico Rosso-type limestones, and this results in a considerable improvement in the clarity of the magnetostratigraphic record. In addition, the ammonite biostratigraphy for the Pliensbachian-early Bajocian interval at Breggia has been determined in detail by Wiedenmayer (1980). Mfirton et al. (1980) acquired a magnetic stratigraphy from the VGP LATITUDE .90 ~ 0o +90oP~
AMMONITE ZONES Stage
VGP LATITUDE -90
(Ma)
~
0 ~
+90 ~
A M MONI TE ZONES Polarity
Stage ,~ (Ma)
sowerbyi oo m
margari-z__.
220
176.5
tatus
~
192
"' ..J
sonae
_
davoei
E2
murchi- ~,~
opalinum
~ 2oo g
180.1
~5
meneghinii
ibex
~o ~8o
i
8
erbaense
bifrons
falciferum z
%1
,.me.on,
189.6
spinatum ~ 0 a
Figure 11.9 Carixian (Pliensbachian) to Bajocian magnetic stratigraphy and ammonite zones at Breggia (Switzerland) (after Horner and Heller, 1983).
202
11 Jurassic and Cretaceous Magnetic Stratigraphy
9-m-thick Bakonycsernye section (Hungary). Here sedimentation rates in the Pliensbachian are about 1.5 m/My and 10 reversals are recognized in this stage. Pliensbachian sections in Italy with similar sedimentation rates yielded comparable numbers of reversals (Channell et aL, 1984). However, at Breggia, the sedimentation rate for the Pliensbachian is an order of magnitude greater (---14 m/My) and 39 reversals are recognized in the stage. Correlation between Breggia and Bakonycsernye shows that seven normal polarity zones at Breggia have been concatenated into one at Bakonycsernye. There is clearly a problem in resolving complete magnetic stratigraphies in the Ammonitico Rosso-type facies when sedimentation rates are a few meters/My, probably because of frequent lacunae even in sections where ammonite finds imply continuity of sedimentation. The Toarcian stratotype sections at Thouars and Airvault (France) are gray marls and limestones, and their magnetic stratigraphies have been resolved by Galbrun et al. (1988a). As the sections are about 5 m thick and the entire stage is represented, the mean sedimentation rates are less than 1 m/My. Nonetheless, a reasonable magnetostratigraphic correlation can be made from the stratotype sections to the Breggia section. The magnetic stratigraphy provides a means of correlation of the West European ammonite zonation in the stratotype sections to the Tethyan ammonite zonation at Breggia. For the Hettangian and Sinemurian, three red nodular limestone sections in Austria (at Kendelbach Graben and Adnet) have been studied by Steiner and Ogg (1988). Correlations among sections are hampered by the condensed nature of the sedimentation and the very poor biostratigraphic control in these sediments. The same problems affect gray/white pelagic limestones of this age in central Italy (Channell et aL, 1984). The best quality Hettangian/Sinemurian magnetic stratigraphy is from a core drilled in the Paris Basin (Yang et aL, 1996) indicating high reversal frequency in the vicinity of the Hettangian-Sinemurian stage boundary.
11.3 Correlation of Late Jurassic-Cretaceous Stage Boundaries to the GPTS Late Jurassic and Cretaceous chronostratigraphy is based on stage stratotypes defined by ammonite zones. However, due to absence or uneven distribution of ammonite faunas in land sections and oceanic cores, Cretaceous chronostratigraphy is often based on calcareous microplankton biostratigraphy and the supposed correlation of these events to ammonites. A review of calcareous nannofossil events in sections with ammonites, microplankton, or magnetic stratigraphy has revealed the uncertainties in correlation of nannofossil and calpionellid datum planes to stage boundaries (Figs.
11.3 Correlation of Late Jurassic-Cretaceous Stage Boundaries to the GPTS
~0~
11.6 and 11.7). All the nannofloral datums have been directly correlated to polarity chrons. Ammonite biozones have been directly correlated to magnetic stratigraphy in parts of the Oxfordian-lowermost Valanginian (see Ogg et al., 1991c), Valanginian-Hauterivian (Channell et aL, 1995b), and uppermost Hauterivian-Barremian intervals (Cecca et al., 1994). The Oxfordian/Kimmeridgian boundary is correlative to the base of the Sutneria platynota ammonite zone, which has been correlated to CM25 in southern Spain (Ogg et al., 1984). The Kimmeridgian/Tithonian boundary is correlative to the base of the Hybonoticeras hybonotum ammonite zone, also in southern Spain (Ogg et aL, 1984). The Tithonian/Berriasian (Jurassic/Cretaceous) boundary does not have a universally accepted definition. Many of the candidate biomarkers have been correlated to the polarity chrons (Ogg and Lowrie, 1986; Channell and Grandesso, 1987; Bralower et al., 1989; Ogg et al., 1991c). The base of CM18 has become the generally accepted correlation to the Tithonian/ Berriasian boundary. The Berriasian/Valanginian boundary is defined by the base of the T. otopeda ammonite zone and falls within CM15n (Ogg et al., 1988) and between the first occurrence (FO) of Cretarhabdus angustiforatus and the FO of Calcicalathina oblongata (Fig. 11.6). The Valanginian/Hauterivian boundary coincides with the base of the A. radiatus ammonite zone and is close to the FO of Nannoconus bucheri and at the base of CM11n (Channell et al., 1995b). The base of the S. hugii ammonite zone defines the Hauterivian/Barremian boundary, which falls between the last occurrence (LO) of Lihtraphidites bollii and the LO of Calcicalathina oblongata and in the upper part of CM4 (Cecca et al., 1994; Channell et aL, 1995b). The Barremian/Aptian boundary was formally defined at the first occurrence of Deshayesites. None of the nannofossil events proposed by Thierstein (1973) to define this boundary have proved to be reliable. The FO of Rucinolithus irregularis is correlated to the upper part of the C. sarasini ammonite zone and is therefore slightly older than the Barremian/ Aptian boundary (Channell and Erba, 1992). The base of CM0 coincides closely to this boundary, but direct correlation of this polarity chron with the ammonite biozone has not been documented. The Santonian-Campanian is formally defined by the appearance of the ammonite Placenticeras bidorsatum, the index species of the oldest Campanian ammonite zone. Unfortunately, this species is extremely rare even in the type area (northwest Europe) and the Santonian-Campanian boundary is often informally defined on the basis of the FO of the nannofossil Broinsonia parca and/or the FOs of foraminifera Globotruncana arca and Bolivinoides strigillatus. The microfossil markers of the SantonianCampanian boundary result in a correlation of this boundary to the basal
204
11 Jurassic and Cretaceous Magnetic Stratigraphy
part of C33r, close to the top of the Cretaceous normal superchron (e.g., Alvarez et al., 1977; Channell et al., 1979; Monechi and Thierstein, 1985). The type area of the Campanian-Maastrictian boundary (northwest Europe) is characterized by a major hiatus, and hence there is more than average debate over the definition of this stage boundary. In the pelagic realm, the LO of the foraminifera Globotruncanita calcarata is often used as an informal definition, and this event usually appears in the top part of C33r (e.g., Alvarez et al., 1977).
11.1 CretaceousMagnetic Stratigraphy The majority of Cretaceous magnetostratigraphic studies have been carried out on pelagic limestones in the Mediterranean region, following the pioneering work of Lowrie and Alvarez (1977a,b) on the Gubbio (Bottacione) section in Italy. The principal feature of Cretaceous geomagnetic polarity is the so-called Cretaceous long normal superchron, an interval of prolonged normal polarity lasting about 38 My, beginning just above the Barremian/ Aptian boundary and ending close to the Campanian/Santonian boundary (Fig. 11.1, Table 11.1).
a. K/T Boundary Magnetic Stratigraphy The position of the Cretaceous-Tertiary (K/T) boundary in the GPTS has always been of great interest because of the associated mass extinctions. The position of this boundary in magnetostratigraphic section was first determined at Gubbio (Bottacione) (Alvarez et al., 1977). Since then, the position of this boundary has been accurately determined in more than 14 magnetostratigraphic sections both in outcrop and deep-sea cores. The average position of the K/T boundary in these studies implies a correlation to C29r (0.75) (75% up from base of the reverse chron). However, the location of the boundary within the polarity zone correlative to C29r is not a good estimate of the position of boundary in time due to a substantially reduced sedimentation rate in the Paleocene part of C29r. Cyclostratigraphy 182
11.1 Cretaceous Magnetic Stratigraphy
| I]3
CRETACEOUS
Ma
20 24
22 \
/
'N
Ic3~
5
,/
13
26
II
74.5
84.0 86.3 88.7 93.3
98.5 ~
~
i Ic3,~
~
~
28
19
112.(
25 ....
i
121
12( 131.0 135.1
CM1
-i CMll
Z
N
~T]._.~s
m-CMI6
141
. ....
o~,7
N
i
_--~.
t
N
i
Figure 11.1 Summary of some of the more important Cretaceous magnetostratigraphic studies. For key, see Table 11.1.
184 Table 11.1 Cretaceous Rock unit 1
Scaglia
Lo Age Hi
Region
C29N-C34N
Italy. Guhhio Italy. Pogg10 Italy. Gorgo a. Cerhera Italy, Boss0
+43.37 +12.58
1
+14.51 +12.58
1
+43.56 + 12.53
2 Fucoid Mark
34N
3 Maiolica
CMO-CM10
4 Maiolica
CM13-CM19
5
C24-C34
Scaglia
6 Fucoid Mark
C34
7 Maiolica
CMO-CMI
8 Maiolica
CMO-CMI 1
9
Maiolica
CM15-CM19
10 Scaglia Rossa
C29-C34
11 Maiolica
CMO-CMI
12 Maiolica
CMO-CM16
13 Scaglia
C30-C34
14 Fucoid Mark
C34N
NSI
NSA
M
D
5-1 m
1
250
- J-I
52
3-4
2
.75-1 m
1
+12.53
1
Italy, Belluno Italy, Alhian. Contessa Italy Pie’Dosso Italy, Polveno Italy, Fonte Del Giordano Italy Moria
+46.00 +11.75
5
Italy Frontale Italy Capriolo Italy Italy Valdorhia
A
+43.56
Q,
NSE
78
RM
- I
DM
AD
A
A
V
V
NMZ NCh C R RT F.C.T. Q 13
6
22
R+
F+
6
References Lowrie and Alvarez (1977h) Lowrie er a/. (1980h)
A
V
F-V
I
1
-
-
F+
6
180
-
I
T
Z-V F-V
24
II
47
-
F+
7
Lowrie ef a/. (198Oa): Lowrie and Alvarez
.8 m
120
-
-
T
Z-V F-V
17
-
4
Lowrie and Channell
359
127
- -
T
-
5 Channell and Medizza
v
33
7 4 7 13
28
-
(1984)
(1984)
(1981)
+43.36 + I 2 5 6
I
72
+45.55 +10.11
3
1.5m
200
+ 10.05
3
1.5m
+43.30 +12.54
1
+43.50 +12.54
30
Tdl
T-A
Z-P
F-V
15
1
16
R-
-
6
Tarduno era/. (1992)
- I
TA
Z-P
F-V
34
11
41
R+
F+
9
200
- I
TA
Z-P
F-V
34
II
41
R+
F+
9
104
275
-
T
Z-B F-V
21
9
43
-
F+
7
Channell and Erha (1 992) Channell and Erba (1992) Cirilli era/. (1984)
1
250
340
- -
A
V
12
6
18
R+
F+
5
+43.56 + I 2 5 3
1
.75-1 m
1
130
- I
T
Z-V V
15
6 3 3 -
-
6
+45.60 +9.89
I
.3m
I
167
- -
T-A
Z-B V
41
-
5
+43.64 +12.71
1
450
1
300
- I
T-A
Z-V F-V
27
9 2 0 -
-
7
+14.43 112.71
3
24
4
30
- I
A
V
3
1 0 6 -
F+
5
+45.63
-
I
F-V
F-V
15
42
-
Alvarez and Lowrie ( 1978) Lowrie and Alvarez ( 19%) Channell er a/. (1987) Alvarez and Lowrie ( 1984) Lowrie er a/. (198Oh)
+43.56 + 12.53
1
7-1 m 1
+44.38 +4.25 +43.4 - .003.00 +46 +11.76
1 1
163 259
2
+ 46
C28-C32 C34-CM5 C26-C34
Italy Presale France Spain Italy Cismon Italy Cismon S. Atlantic N. Pacific S. Atlantic
Site 463 Site 516 Site 317 Point Loma fm Great Valley Gap Christopher Fm Hole 69OC Cehegin Aix-en-Provence
C34-CMO C29-C34 c34 C32-C33 c33-c34 C34-M 1 C29-C33 CM15-CM17 CM28-CM34
Pacific S. Atlantic C. Pacific USA (CA) USA (CA) Canada S. Atlantic Spain France
+21.36 -30.35 -15.2 +32 78 +40.00 + 80 - 65 +38.(!6 +33.5
Deccan Traps Sierra Geral
C29-C30 Early Cretaceous Haul- Alb E. EoceneTuronian
India Brazil
+20
15 Maiolica
MGM8
16 Berriasian Lmst. 17 Sopelana 18 Scaglia
CM14-CM19 C29N-C31R C33R-CM8
19 Maiolica
C33R-CM8
20 Hole 525A 21 Site 167 22 Hole 530A 23 24 25 26 27 28
Leg 103 Holes 752-755
Atlantic Indian Oc.
94
T
2-V F-V
15
9 4 7 -
-
6
13 X
5 4
Lowrie and Alvarez (1984) Galbrun (1985) Mary er a/. (1991) Channell el a/. (1979) Channell er a/. (1979)
I
1 1 1
394.
T-A Z-V F-V T-A 2-P F-V A B V
2
1
1
394.
A
B
-29.08 +02.99 +07.00 - 177.00 -19.19 -9.39
4
.3-.6 m 88 .35 m
1 1
133 120 630
A AT A
2-B I 2-P F-I 2-B I
+ I75 -35.18 -1468 - 117.29 -121.5 -92 +2 -1.81 +5.5
1 1 1
56
1 I 1 1
IM) 2x9
A A.T. A T A-T T-A A T T
2-P B Z-P Z-V 2-V Z-V 2-V 2-P 2-V
+11.76
+75 -18 - 56 -30 -48 +42.17 -12.17 -31 +93.83
1
I
3 9 6
2 2 33 3 20 6 4
180
74 45 252 76 .25 m 73
I
30 150
1
50 200 3000 IS00 70 12
110
1-4
1166
27 3
4-10 500
loo0
1.5 m 576
383
300
1
310
3 5 I
-
V
F-I I I
R+ R-
-
26
47 50 20
-
-
6 5 6
26
20
-
-
6
-
5 5 4
12 10
II 5 9 3
5 3 8 6 2 4 4 1 5 -
55 35
R+
-
-
-
Chave (1984) Tarduno er a/. (1989) Keating & HerreroBervera (1984) 5 Tarduno el a/. (1989) 3 Hamilton el a/. (1983) 5 Tarduno (1990) 8 Bannon er a/. (1989) 6 Verosub er a/. (1989) 7 Wynn er a/. (1988) 4 Hamilton (1990) 7 Ogg el a/. (1988) 5 Westphal and Durand (1990) 6 Vandamrne era/. (1991) 7 Ernesto et a/. (1990)
11
-
-
19
40
R+
-
5 7
2 0 1 6 3 5 1 01 2 24 2 4 6 3 05 3 0 7 2 72 6 2 5
V V F I F F
4 13
T.A. 2-P F T-A 2-V F
3 4
2 -
20 26
T-A T-A
2-P I 2-P I
3
3 5 11
-
-
-
-
R+ -
F+
-
F+
R+ -
-
-
-
Ogg (1988) Gee et a/. (1991)
185
| ~6
11 Jurassic and Cretaceous Magnetic Stratigraphy
based on carbonate content, color density, and magnetic susceptibility from South Atlantic cores and Spanish land sections was used to demonstrate that the boundary occurred in time almost exactly in the middle of C29r (Herbert and D'Hondt, 1990; Herbert et al., 1995). Nonmarine terrestrial sediments from the western United States (Butler et al., 1977, 1981b) as well as from Europe (Galbrun et al., 1993) have contributed to the debate concerning the faunal crisis at the end of the Cretaceous by demonstrating that extinctions of marine and nonmarine fauna were essentially synchronous (see Section 9.5).
b. Santonian-Maastrichtian Magnetic Stratigraphy The Late Cretaceous polarity zones at the young end of the Cretaceous long normal interval were recorded and correlated to foraminiferal biostratigraphy in the original Alvarez et al. (1977) study of the Gubbio (Bottacione) section (Fig. 11.2) Subsequent nannofossil biostratigraphy at Gubbio (Monechi and Thierstein, 1985) has provided a correlation of these polarity chrons to nannofossil zones (Fig. 11.3). The correlations of polarity chrons to nannofossil and foraminiferal biozonations at Gubbio have been ratified and refined in the Southern Alps (Channell and Medizza, 1981), Spain (Mary et al., 1991), and in cores from the NW Pacific (Monechi et al., 1985) and South Atlantic (Hamilton et al., 1983; Chave, 1984; Tauxe et al., 1983c; Poore et al., 1984; Keating and Herrero-Bervera, 1984). Due to the scarcity of ammonites in the pelagic limestone sections, polarity chrons are generally correlated to the ammonite-bearing stage stratotype sections through the micropaleontology. Direct correlation of the GPTS to European Upper Cretaceous ammonite zones which define stage boundaries has not been achieved, although the C33r/C33n polarity chron boundary has been correlated to ammonite biostratigraphy in Wyoming (Hicks et aL, 1995).
c. Cretaceous Long Normal From paleomagnetic data available at the time, Helsley and Steiner (1969) postulated the existence of an interval of constant normal polarity from Late Aptian to middle Santonian which could be correlated to long smooth intervals in coeval oceanic magnetic anomaly records (Raft, 1966; Heirtzler et aL, 1968). The presence of this long interval of normal polarity was confirmed by Keating et al. (1975) from deep-sea cores obtained from the Deep Sea Drilling Project (DSDP). Subsequent studies in Italian pelagic limestones resulted in correlation of the top of the quiet zone (base of C34r) to the early Campanian, just above the base of the G l o b o t r u n c a n a elevata foraminiferal zone (Alvarez et al., 1977;
11.1 Cretaceous Magnetic Stratigraphy
] 87
PALEONTOLOGICAL
LITHOLOGY
POLARITY
VGP LATITUDE
-90
0
+90
ZONES
Planktonic ]Calcareous _foraminiferaI nannofossils
Globigerina I = eu_cluDina %,j
STAGE
Pa[eo(ene
Abathompha!us mayaroensls i
MAASTRICHTIAN
GIt. g a n s s e r i
GIt. tricarinata GIt. calcarata
CAMPAN-
GIt. elevata
IAN
r
=-"~
O
,m
GIt. concavata carinata
..{3
SANTONIAN
GIt. concavata concavata
(.9
[ONIACIAN
ql=~
GIt. schneegansi
,,,
TLIRONIAN
GIt. helvetica ~.H. lehmanni rRtl. cushmani
(notzoned)
Planomalina buxtorfi T. breggiensis
o~-,.===
~ "
G. blowi H. similis
Eiffellithus turriseiffeli
_.J _R _cretace~--L _ Parhabdofithus
augustus : Chiastozygus " litterarius
Micranthofithus obtusus
Lithraphidites bollii
limestone
II
normal
marl
~
reverse
~
CENOMANIAN
BIAN APTIAN
BARREM IAN
HAUTERIVIAN
hiatus
Figure 11.2 Summary of Cretaceous magnetostratigraphic studies at Gubbio and Cismon (Italy) (after Lowrie et al., 1980b).
| 88
E
11 Jurassic and Cretaceous Magnetic Stratigraphy
~~ .~ ~
500- ,~ii ~
CALCAREOUS
POLARITY CHRONS
EVENT
44O
-
top C grandis (484m)
Ii
20r
420
•
CPI2
280 9 z r
P8
lY r base M arag~
--i
I
~tYmp:ff:Tmi:.ii~top_iRpseudomenardii I
~a: DI-I~le~nl~ll~3~32?)m) " ' ~ "P, OaseP. pseudomenardii (364~7"/ -~ ~ }
ase F. n is (36 .5 - base E maceltus (354m) --.C~2, -.base C danicus (350.5_m). -'CPI' -top C r e t a c e o u s (347.6m)NC23 - base M. murus (337.9m)
- base L. quadratus ~326m)
NC21 !
- top 77.trifidus (302m)
I 32r
~
'
- base T trifidus (264m)
z z
_ top E. eximius (253m) .- base T gothicus (250m)
33n
I
,
base G. gansserl (302m)
MC$8
Z
~
" top G. calarata (2ZO.2m) base G. calarata (264m)
NCl9o
P-"
,r
,ru~
' i :~ L
--
~
Z ; 'r
MCs7
" . base B. parco (209m)
NCl8 ~
,
_,1
9
.
.
.
.
.
.
.
~1
i
~uul
5
U
! base Giobotruncana elevata (196m);,
NC17
or} ~
~Z
- base C. oculeu~ (222m) 33r
-r"
Z
z z
220- .,=1=,=
MCIIO ~
NC19b
--~ ~J ~ ~ I ~ ~. 1 "" ~
base A mayaroensis (330m) ~ base G. contusa (325 5m) --
I~20 MCs9
zx
260- z
I
~,1~=" base M. angulata (359m) .~"Pt--" base M. uncinata (356. 5m) ~ PI -~'base S. trinidaclensis ( 3 5 3 m ) ~ =--"~,base S pseudobuiloicfes (348m~ MCsll base G. eugubina (3476m) /
~lC22 ~ ~
31r
34n ....
(3998m) - - ~
I-base O. diastypus (386m) "'~pa L _ / top M edgari (382m) "~ ~..base D. multiradiatus (378 5m~,,,j.p r ' ' / t o p lld. velascoensis ( 3 7 6 r n ) \
24r . . . .
r
z 240. z
base G. palmeroe (418.5m)
CP 9 p 6
31n i
t
i
base T. orthostylus (398m)
32n
~
i
CPIO!-- base G. taroubaensis (408 7m) - -.
29r 30n
i
I
base Hantkenina sp. (429m) _ . . _ ~
base D. Iodoensis (402m)
340
~,J
----
iP 9
22r ~ -
360
i
- P1 I
23r ~
25r
300, m =
-
base N fulgens (445m)
i~
~i
base O sublocloensis (417. 5m) base C crassus (414m) ~
26r/ 27r
320- ~ i~
'
,
P1] - - - - - - - P12 o M CP13 ~ t p . aragonensis (453m)
base R. umbilica (463m)
. ~
380
EVENT
CPI~I~ P ~ " base G. semiinvoluta (489m) --.. --
L 21r I
400 "="-=
,
STAGE
CPI4
I
~
~ ZONE, ,
basetrecurvus(50'm) CPl~Pls
'' 16r
9
FORAMINIFERA
ZONE
480 ~i~ 18r/ t z~x~: 19r 460 i
PLANKTONIC
NANNOFOSSILS
Z
~ .
.
Correlation of Late Cretaceous-Eocene calcareous nannofossil and planktonic foraminiferal events/zones to polarity chrons at Gubbio, Italy (after Monechi and Thierstein, 1985).
Figure 1 1 . 3
11.1 Cretaceous Magnetic Stratigraphy
| ~q
Lowrie and Alvarez, 1977a,b; Channell et al., 1979; Channell and Medizza, 1981) (Fig. 11.2). The entire Cretaceous long normal interval has been recorded in the Cismon section (northern Italy) and here the reverse polarity chron at its base (CM0) is close to the Barremian/Aptian boundary (Channell et al., 1979) (Fig. 11.2). The base of CM0 has since been found to immediately postdate the first occurrence (FO) of nannofossil R. irregularis in two Italian land sections (Capriolo and Pie' del Dosso) (Channell and Erba, 1992) and at ODP Site 641 on the Galicia margin (Ogg, 1988). In the absence of the ammonite Deshayesites, which formally defines the Barremian/Aptian boundary, the FO of R. irregularis is considered the most reliable microfossil marker for this stage boundary. The base of CM0 is usually close to but slightly younger than this nannofossil event. There are a number of magnetostratigraphic records of post-CM0 Aptian-Albian reverse polarity chrons. The first such observation in outcrop was by Lowrie et al. (1980a), who observed a reversely magnetized bed in the Late Aptian Globigerinelloids algerianus zone at Valdorbia (Umbria, central Italy). This so-called ISEA reverse polarity zone (Fig. 11.4), also known as polarity chron C M - 1 (minus 1), was not observed at two other sections in Umbria where the same foraminiferal zone was present in comparable or greater stratigraphic thickness; however, Tarduno et al. (1989) observed two samples with reverse magnetizations just above the FO of G. algerianus at DSDP Site 463. The documentation of this short reverse polarity chron is strengthened by two samples with reverse magnetization spanning 43 cm in a core from ODP Site 765 (Ogg et al., 1991b), where the reverse polarity zone postdates CM0 and is late Aptian in age. Seven reverse polarity zones have been observed by Tarduno et al. (1992) in the middle Albian interval (Fig. 11.4) (A. albianus nannofossil zone and top Ticinella primula to base Biticinella breggiensis foraminiferal zones) at the Contessa section near Gubbio (Umbria, central Italy). In these reverse polarity zones, the magnetization is carried by hematite and the reddening of the sediment may be late diagenetic in origin. The reverse magnetization components in this interval are not antipodal to the normal magnetization components, and the reverse directions are offset toward directions consistent with the Late Cretaceous or Paleogene. The duration of the proposed middle Albian polarity zones is well known from lithologic cyclostratigraphy (see Herbert et al., 1995, and references therein). Of the seven polarity zones recognized by Tarduno et al. (1992), the thickest (3.25 m) represents about 800 ky. This duration is greater than that estimated for reverse chron CM0 and about twice that estimated for CM1 (see Herbert, 1992), both of which are usually recognized by shipboard magnetic anomaly surveys. It is, therefore, doubtful that these middle Albian reverse
| 90
11 Jurassic and Cretaceous Magnetic Stratigraphy
CEN 198"5
PLANKTONIC FORAMINIFERS
CALCAREOUS NANNOFOSSILS
{3)
~=
R. brotzeni
i~
LO R. irregularis L~ F O E . turriseiffefii
m E
OA
EIc
F O P . achlyostaurion FO "small" Eiffellithus
z
!
R. ticinensis ~_ R. subticinensis
~
.o
.J <
FO R. appenninica FO R. ticinensis F O R . subticinensis
T. praeticinensis F O B . breggiensis
T. primula FO A. albianus FO 7. orionatus
H. rischi
E 112.0
F O R . brotzeni
R. appenninica
B
~
.......... OAE1 b ~ H. planispira ..........
FO C. ehrenbergii F O P . columnata
FO T. primula LO T. bejaouaensis
T. bejaouaensis LO M. hoschulzii LO N. steinmannii
Z
N. truittii
H. trocoidea
acme
G. algerianus
<
F O G . algerianus
FO C. achylosum
G. ferreolensis
FO B. africana
L. cabri
9FO E. floralis F O R . angustus FO F. oblongus
121.0
i (N3
rr
FO T. bejaouaensis LO G. algerianus
FO L. cabri
(~Ela
~4-- n
Nannoconid "crisis"
G. blowi ..........
.~:
a~
LO L. cabri
G. duboisi kO C. oblongata
F O G . blowi F O G . duboisi
notzoned
(3~,15
~
~
LO L. bol//i
Figure 11.4 Correlation of mid-Cretaceous calcareous nannofossil and planktonic foraminiferal events to polarity chrons (after Larson et aL, 1993).
polarity zones represent the geomagnetic field at the time of deposition of the sediments. Until the middle Albian reverse polarity chrons are recognized elsewhere, we consider that they should not be incorporated into the geomagnetic polarity time scale (GPTS).
11.1 Cretaceous Magnetic Stratigraphy
|9|
d. Berriasian-Aptian Magnetic Stratigraphy "M-sequence" polarity chrons are numbered according to the correlative oceanic magnetic anomaly. These anomaly numbers, by tradition, correlate to reverse polarity chrons except for M2 and M4, which correlate to a normal polarity chrons. We use a prefix "C" to distinguish polarity chrons from magnetic anomalies and follow Harland et al. (1982) in labeling normal polarity chrons (other than CM2 and CM4) using the number of the next older polarity chron with the appendage "n." Using this nomenclature, CM9 denotes the reverse polarity chron correlative to magnetic anomaly M9 and CM9n denotes the normal polarity chron between CM9 and CMS. It should be noted the magnetic anomaly between M10 and M l l is labeled M10N. This anomaly was originally omitted from M-sequence anomalies (Larson and Pitman, 1972) and was included by Larson and Hilde (1975) and designated M10N after Fred Naugler, co-chief scientist of the NOAA Western Pacific Geotraverse Project. Land section magnetic stratigraphy in the Mediterranean region has been the basis for the correlation of the M-sequence polarity chrons to biozonations and hence to geologic stage boundaries. The oceanic magnetic anomaly record from the Hawaiian lineations (Larson and Hilde, 1975) remains the template for the M-sequence polarity pattern. Some pelagic limestone sections in Italy have recorded substantial portions of the Msequence pattern. Notable among these sections are Gorgo a Cerbara (CM0-CM9) (Lowrie and Alvarez, 1984), Polaveno (CM3-CM16) (Fig. 11.5) (Channell and Erba, 1992; Channell et al., 1995b), Capriolo (CM8CM16) (Channell et al., 1987), and Bosso (CM14-CM19) (Lowrie and Channell, 1984) (see Fig. 11.1, Table 11.1). It is remarkable that the polarity pattern derived by Larson and Hilde (1975) from Hawaiian oceanic magnetic anomalies has been confirmed time and time again by these land section studies, particularly in the CM0-CM19 interval. The only polarity chron observed in land section which is not included in the Larson and Hilde (1975) polarity pattern is a second reverse subchron between C M l l and CM12. These two subchrons were recognized at Capriolo (Italy) (Channell et al., 1987) and have also now been observed in the oceanic magnetic anomaly record (Tamaki and Larson, 1988). The vast majority of the magnetostratigraphic studies in the CM0CM19 interval have been carried out in the Maiolica Limestone Formation of Italy. This is a Tithonian to Aptian white/gray thin bedded magnetitebearing pelagic limestone with fairly constant sedimentation rates (typically --~15 m/My), thereby aiding the recognition of polarity zone patterns. The biostratigraphic control in the Maiolica is mainly from calpionellids for the
Polaveno
Lithology
Nannofossil Eventsand Zones
Polarity Chrons
z ,~ <_
i5o i 'i i--!.ii-'-~.ii 'i.i--.ii 'i..i........ 'i'i~!-.i.'i i .i i .i.il
C M 3 C. oblongata
~
1:
!
......
en .........
!00
...........................................................
............
L. b o l l i i
CM5
"
CM7 i
.
.
.
.
.
.
i
.
150
R. terebrodentarius
,
9 C. cuvilleri
CM9
t ....
L. bollii
CM'~ON t.
.
N. bucheri
oo ....
T. verenae
~
--
o
8~ t. . . .
CM12 _'1~ - ~ ~
~ . . . . . il ......
. . . .
! .
.
.i. 11... " _ , i - . . .... ~ ~. . . . . . . . . . .. :
i
T. verenae
C. oblongata Calpionellites d a r d e d
CM~5
0
40
z
<
z
~_ z
. . . . . . . . .
T=
.~
R. fenestratus
t ....... C. angustiforatus
-40
~
CM113 I
t
-80
o
~ .
80
VGP Latitude (o) Figure 11.5 Virtual geomagnetic polar (VGP) latitudes from the Polaveno section (Italy), correlation to the GPTS, and correlation to nannofossil and calpionellid events (after Channell and Erba, 1992; Channell e t al., 1995b). In the lithologic log, F indicates small faults (with minimal offset), speckles indicate cherty intervals, diagonals indicate marly interval, and black bars indicate black shales. Horizontal thin bars indicate pelagic limestone, the dominant lithology.
11.1 Cretaceous Magnetic Stratigraphy
| 9~
Tithonian and Berriasian and from calcareous nannofossils for Tithonian tq Aptian. It has been demonstrated in numerous Maiolica sections that polarity chrons correlate consistently to nannofossil events (Fig. 11.6) and calpionellid events (Fig. 11.7). For correlations to calpionellids, see Channell and Grandesso (1987) and Ogg et al. (1991c); for correlations to nannofossils see Bralower (1987), Channell et al. (1987, 1993), Bralower et al. (1989), Ogg et al. (1991b), and Channell and Erba (1992). The result of these studies is that the combination of nannofossil or calpionellid biostratigraphy and magnetic stratigraphy gives a very precise and useful integrated stratigraphic tool for pelagic limestones of this age. Even for short sections where polarity zone patterns are not distinctive, the nannofossil/calpionellid events indicate the approximate stratigraphic position relative to the GPTS, and the magnetic stratigraphy then gives precise stratigraphic control. Although the correlation of polarity chrons to nannofossils and calpionellids is firmly established, the correlation to stage boundaries requires correlation to ammonite zones. Although ammonites are very rare in the Maiolica limestones, recent finds place the Hauterivian/Barremian boundary in the upper (younger) part of CM4 (Cecca et al., 1994) and the Valanginian/ Hauterivian boundary at the young end of C M l l (Channell et al., 1995b) (Fig. 11.6). Previous estimates of the correlation of these stage boundaries to polarity chrons relied on the correlation of nannofossil events to ammonite zones from Thierstein (1973, 1976). For the Berriasian-Valanginian boundary, the relevant ammonite zonal boundary has been correlated directly to CM15n at Cehegin (Spain) (Ogg et al., 1988). For the Jurassic/ Cretaceous (Tithonian/Berriasian) boundary, there are two alternative definitions with respect to ammonite zones, with no clear consensus. In the Tethyan realm, the boundary lies either at the B. grandis/B. ]acobi zonal boundary or at the underlying B. jacobi/Durangites zonal boundary. At Carcabuey (Spain), the B. jacobi/Durangites zonal boundary lies in a normal polarity chron at the top of the section, which is interpreted as CM19n (Ogg et al., 1984). Elsewhere, nannofossil and calpionellid events in the vicinity of the Jurassic/Cretaceous boundary have been consistently correlated to polarity chrons in land sections and deep-sea cores (Lowrie and Channell, 1984; Cirilli et al., 1984; Channell and Grandesso, 1987; Bralower et al., 1989; Ogg et al., 1991c). These studies imply that the Jurassic/Cretaceous boundary lies in the upper part of CM19n or at the CM19n/CM18 polarity chron boundary, and it has been advocated that this polarity chron boundary be used to define the stage boundary (Ogg and Lowrie, 1986). At Berrias (France), the Berriasian stratotype section yielded a magnetic stratigraphy that is correlated to calpionellids, nannofossils, and ammonite zones (Galbrun, 1985; Bralower et al., 1989); however, the base of the section is within the B. grandis zone and
194
11 Jurassic and Cretaceous Magnetic Stratigraphy
POLARITY CHRON
Ma
. .1 2.o .
CALCAREOUS NANNOFOSSILS
.,
"--" -
CM~
CM1
-
--
Nannoconid crisis ~
---r
[]~
~ F. oblongus R. irregularis
~
125 CM3
-- CM4 "-'~r--
AMMONITES POLARITY ZONES SUBZONES STAGES CHRON
m
]-"1C. oblongata ]--1L. be/Ill
~Rterebrodentarlus 7C." cuvillieri -1 CM10 i "j]-J L. boIlii
D. weissi ~ D. tuakyricus _ ~ - C.'s,~ a'ra"si_ ~_ il. airaudi ,(i) H. feraudi ca. H. sartusi = , A.vandenheckei H. caillaudi ._ "S, nicklesi , ~ S. hu(:Jii ' .9o P.ancjulicostata P. catulloi P.angulicoit. B. balearis- P.'li,qatus" e"
"-t--c I-- 8
--
CM1 -CM11A - ~ - CM12
L. nodosoplicatum
_
,
'j_.j T. verenae
--
--
CM1
51,.~
N. pachvdicranus
'
~_j p. fenestrata
T. pertransiens otopeta
m7uR. nebulosusL..F, boissieri j_Jc. angustiforatus _ CM16 0_.t = - ' ' - ' - ' -
1
J
CM17
~
~
CM18 ~
N. St. steinmannii i " C. cuvillieri ~ ~'
"I-JN._ stoinm, minor
Ii
mmll
C. mex. minor
t1" ,
m z .
I
or ~
,
M~
CM1
CM4 C~M7
CM10
I
~--CM10N ~ z i ~: ~ 9 ~
UM11A 9 , CM 12
.r.
i
alpillensi$
B. picteti ~ m - ~ - i.paramimouna ~" ~-CM16 (/) ,
T. occitanica
D. dalmasi B. privasensis
<{: ~
T.subalpina i ~
i
io m,
~
B~aco~l
Durangites
~
~=
P. transitoris
Simplisphinctes
B. peroni
g. aa'mTr~n d-um /
R. richteri
l
z ~ ,,,
X
_ B. grandis. . . . . . .
--' ' ~ - ' ~ l N. colomiin i-1 i, CM19 ~ "J R./aline,~ L_LjI -U. gr. granulosa ' 7J. ...J carniolensis i JM.L.chiastius -~J C. mex. mexicana 17 145 c a 2 0 ~ ----'-I _ P. beckmannfl L...u j ~_j P. embergeri CM21 ~ CM22
H. trinoclosurn
S. verrucosum B. campylotoxus
3S~TM~4"mt'j-JC. oblongata ~
C. Ioryi A. radiates
<
o.~~~_. =o. ~. ~ ~ T< 'r
S. sayni
.CMlON=~J---iN'bucheril T. verenae
z.
"~ ~ ~)
/ S . biruncinatum
:~
~ E
CM17
CM18
i
CM19 CM20 1 CM21
V~all~ed[n~m:
H. hybonotum
CM22
kl "
"
x
11.6 Summary of correlation of Oxfordian to Aptian polarity chrons to nannofossil events/zones and ammonite zones. Open bars indicate the range of the nannofossil events with respect to polarity chrons (from Channell et al., 1995a). Figure
11.1 Cretaceous Magnetic Stratigraphy
] 95
~mmonite Calpionellid Zone zone i event ~ P ~
Stage
Busnardoiles
>
T" P ~ r t r a n s i e n s
]
I7ili!ii7i7777!i,~~C.
T. otopeta -_......................
9
B. callisto
da~ri
CM14
=
~ h
D
P. pecteti
" ung;'rica
CM15
:i:!:i:iiii
Z<~ .paramimounum ........B................. ~:~....:~:I--'C. r~C ~ oblon~ CM 16
h'q <
::::::::::::::::::::::::::::::::J .
O. d a l m u i :::::::::::::::::::::::::::::::::::::::::::::::::
simplex
C
~
B. privasensis ................................. :!:i:i:7:7:7:i:~:7:7:7:7:7:7:7:7:7:7:7:7:7:7:7:7:! :i:!:i:i:i:i:i:i:i:i:!:!:!:{:i:i
.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:
,~'IC. elliplica
B. grandis .......
. ferasini
:ii!i!i!i!iiiiiii!i!i!i!i!iiiiiiiiiiiii!iiiiiiiiii::::::::::::::::::::: i:i:i:!:i:!:!:!:i:::::::::::::::::::::::::::::::: :::::::::::::::::::::::::::::::: ....._ ....... ._.~:::::::::::::::::::::::::::: :, .
.
.
.
.
.
.
i
.
CM18
-
!iii!iiiiiii!i!i!i!!i!!!i!iiiiii!
Z
........o:.,._..~,,,:.......
~)
Sid~l,s;Uincteg::i!::::::::::i:i i i :2i!i;~l.
I-
S ~.;~o;'.:;umChit" I ~,
A
I c-='"n~ ~
,,
:::::::::::::::~.:E:::::-::::::::::::............... T. L'arpathicaT'T B. peroni
s. biruncinatum R richteri
( ~ 20
C. bone. t~,.
~
~I~Chitinoidell,
(3vi21
BB
H. verruciferum
Figure11.7 Correlation of calpionellid events to polarity chrons (after Channell and Grandesso, 1987; Ogg et aL, 1991c).
therefore the section does not include either of the two definitions of the Jurassic/Cretaceous boundary. Ogg et al. (1991c) have identified CM17 in the Purbeck Limestone of southern Britain, providing a first M-sequence magnetostratigraphic correlation out of the Tethyan into the Boreal Realm.
196
11 Jurassic and Cretaceous Magnetic Stratigraphy
11.2 JurassicMagnetic Stratigraphy a. Kimmeridgian-Tithonian Magnetic Stratigraphy As for the Early Cretaceous (CM0-CM18), the Larson and Hilde (1975) oceanic magnetic anomaly block model is the template for geomagnetic polarity in the Tithonian and Kimmeridgian stages of the Jurassic (CM18CM25). Subsequent extension of the oceanic anomaly block model to M29 (Cande et al., 1978), and to M38 (Handschumacher et al., 1988) has extended the record into the middle Jurassic interval. Land section magnetic stratigraphies have been correlated to CM18-CM25; however, correlations to older M-sequence chrons and between-section pre-Kimmeridgian correlations have not been adequately achieved (Fig. 11.8, Table 11.2). The problem for pre-Kimmeridgian magnetic stratigraphy is twofold. First, preKimmeridgian calcareous nannofossil biostratigraphy does not yet allow precise correlation among Tethyan sections; and second, pre-Kimmeridgian Jurassic facies in the Tethyan realm are often highly condensed and/or highly siliceous. The oldest polarity chron recorded by the Maiolica Limestones of Italy is CM19. The Maiolica limestones are usually underlain either by siliceous limestones (Calcari Diasprigni) or by condensed nodular limestones (Ammonitico Rosso). The Sierra Gorda and Carcabuey sections of southern Spain are the key sections for the correlation of CM19-CM25 to ammonite zones (Ogg et al., 1984). In these sections, the "Ammonitico Rosso"-type sediments have mean sedimentation rates of 2-3 m/My. The polarity patterns are distorted by variable sedimentation rates and it is not easy to correlate polarity zones to polarity chrons. Nonetheless, the correlations of Ogg et al. (1984) place the H. beckeri/H, hybonatum ammonite zonal boundary which defines the Kimmeridgian/Tithonian boundary in CM23n, and the I. planula/S, platynota zonal boundary which defines the Oxfordian/ Kimmeridgian boundary in CM25 (Fig. 11.6). Ammonites are lacking in this interval in the Belluno Basin and Trento Plateau (Southern Alps, Italy), where the Oxfordian/Kimmeridgian and Kimmeridgian/Tithonian boundaries lie in the unsubdivided "Saccocoma Zone." The lack of calpionellid or other microfossil events in the Italian sections precludes the accurate definition of these boundaries; however, the polarity zone pattern in these sections is more readable than in the Spanish sections. Estimates of
Figure 11.8 Summaryof some of the more important Jurassic magnetostratigraphic studies. For key, see Table 11.2.
JURASSIC 14
Composite (Ma) ~---144.2 r cO c-
10
54.1
mm
C
EE m
,.,..
0 X
,-m
0 --159.4 c"
m mm
> 0
64.4 r-
6
11
tor
--169.2 C o 0
n~
-s ---<180.1 c o~
12
15
17
.0
.d
0O r .m m
m m
II
13"195.3 E C
II
03 --.201.9
7"
198 Table 11.2 Jurassic Rock unit
Lo Age Hi
Region
@
A
NSE
NSI
NSA
M
D
RM
DM
AD
A
NMZ NCh %R RT
1
13
-
-
T
Z-P
F-D-I
21
-
60
- I
T-A Z-V F-D-I
15
-
SO
F.C.T
Q
References
R-
6
R+ -
7
Steiner era/. (1989) Galbrun ef a/. (1988a) Ogg er a/. (1984) Channel1 er a/. (1990a) Steiner ef a/. (1987) Homer and Heller (1983) Witte era/. (1991) Channell era/. (1987) Steiner er a/. (1985) Steiner er a/. (1987) Homer and Heller (1983) Steiner and Ogg (1988) Channell era/. (1982b) Marton er a/. (1980)
1 Marine Magnetic
Anomalies 2 Sierra Harana
Spain
+37.2
-3.7
1
3 Toarcian
Bathoniard Bajocian Toarcian
France
+47.W
-.02
2
.I m
1
5
4 Carcabuey 5 Ammonitico-Rosso
CM18-CM25 Ox-Callo.
Spain Italy
+37.5
-3.3 +I1
2 3
.I m .05 m
1
1
10 10
- - -
T T
Z-V FV Z-P V
28 55
6
+46
-
4 0 R + 32 - -
6 6
6 La Fuente
Bathe.-Bajo.
Spain
+37.5
-3.3
2
1
10
- -
T
Z-P
19
-
42
R + F+
8
7 Breggia
Baj.-Car.
Switzerland
+45.87 + 9
2
I
120
- I
T-A Z-V F-V
82
-
47
-
-
7
USA Italy
+40.25 -75.25 +45.7 f11.46
3 1
4 139
5 1
4180 60
T Z-P FV T-A Z-B V
1
- -
25
1 9
0 52
-
R + F+ F+
9 5
105
1
13
- -
T
Z-P
F-D-I
22
4
54
R-
F+
7
-
-
T
Z-P
F-D-I
51
-
41
-
F+
8
82
-
47
-
-
7
D-l
14
-
62
-
C+
6
-
17
6
4 9 - -
11
-
55
8 Newark Supergroup Het-Carnian 9 Xausa CM14-CM23
106
9
9
.2 m
10 Aquilon
L,Oxfordian M Spain
+41.3
-l.W
5
11 Carcabuey
Bath-Aal
Spain
+37.5
-3.3
2
.I5 m
1
33
12 A l p Turati
Ba-Car.
Switz
+45.87
+9
2
.2 m
1
120
1-13.5
13 Kandelbach Grab.
Sin:Het.
Austria
+4.7
14 Foza
Ber.-Kim
Italy
+45.54 +13.5
15 Bakonyncoke
Pliens
Hungary
+47.1
+I8
3
169
I
3 9 0
1
1
.I m
1
24 -
K
I
- I
T-A Z-V F-V
- -
T
- I
T-A -
8.9 - I
F-D-I
T
B
Z-V V
R-
2 -
5
16 Quero
Titho
Italy
17 Cingoli
Pleins-Sinme
Italy
+43.33
18 Frisoni
ritho-Kimm
Italy
+4.5.53
Ammonitico-Rosso
L Toarcian E
Spain
+ 37.39 -3.49
Kayenta Fm.
Pliensbachian
USA
+38.6
-109.6
101
Krakow Uplands La Luna
M.Ox. E.. Call. Sant. Sen
Poland Veneiuela
+SO.I +Y.Y
+I9 6 -61.0
204 48
1
Lebombo Grp. Morrison Fm.
E. Jurassic Kim-Ox
S. Africa USA
-24 +3X.13
+31.75 -108.21
25 215
4s 1
6000
Morrison Fm
Kim-Tith
IJSA
+MI
-10x.z
I
1
Purbeck Ls. Sierra Gerral
Ber.-Tith
England
-2.24
I
I
Sierra Paloma Summerville & Curtis Fm. Umbria
+SIM
1
I
74
+I321
1
64
20
+ 11.33
I
132
xn
Brazil
-
-
Toarcian
Spain
+40.65
- 1.1
Callovian
USA
+3x.x
-111.1
TithonianToar.
Italy
+43.33
+I3
.I3
I
1
50
1
1
20 I00
I
.3 7x ~
~
T
Z-B
T
V
6
4
39
6
Z-V F-V
16
-
5x
6
T
Z-B V
IX
7
47
6
T
%-P F ~ D - I 21
53
R
6
T
-V
IY
R+ -
5 7 7
D-l
8 ~
R+ -
A
63
~~
4
30 7x
T Z-P T-A Z-P
F F-D-I
A-T B T V
F D-I
165
T
Z-V
F-D-I
XI1
1I15 -
T
V
F-D-I
33
I07 50
8.5
I
K
A
~
~
19
5
-~~
~
6 4
R+ - -
4
5 ~
Channell and Grandcsso ( 1987) Channell el a / . (19@) Channell and Grandcsso (1987) Galhrun er a1 (1990) Steiner and Helslcy (1974)
Ogg e r n / . (19Yla) Ca.itillo er a / . (1991) Henthorn (1981) Steincr and Helsley ( 1 9 7 5 ) Strmer and Helslcy (197Sb) O g g r r a l . (1991~) Valencio er a / . (1983)
47
1
75
T
Z-V V
4s7
I
120
T
V
1
2IN
T
Z-B F-V
5
I
F
14
3h
4
Y
92
5
Galhrun er a1 (IYXXh) Steiner (197Xi
14
14
h
Channell (19x4)
YI
ul.
199
~00
11 Jurassic and Cretaceous Magnetic Stratigraphy
the location of the Kimmeridgian/Tithonian boundary in the Italian sections place it in CM22 (Ogg et al., 1984; Channell and Grandesso, 1987). Early work on Jurassic magnetic stratigraphy was carried out on the Kimmeridgian-Oxfordian Morrison Formation in Colorado (Steiner and Helsley, 1975a) and the Callovian Summerville and Curtis formations in Utah (Steiner, 1978). Correlation to European sections is hindered by poor biostratigraphy in these terrestrial and near-shore sediments, complex magnetic behavior which compromises the fidelity of the magnetostratigraphic records, and variable sedimentation rates which distort the polarity zone pattern. Steiner et al. (1994) have made the case that magnetic stratigraphy can be used as a means of correlation in the Morrison Formation in Colorado and New Mexico.
b. Oxfordian-Callovian Magnetic Stratigraphy The correlations of European land section magnetic stratigraphies to M0M25 oceanic magnetic anomalies are fairly robust; however, magnetostratigraphic correlation to M26-M38 has not been well established. CM26 to CM30 have been correlated to Oxfordian ammonite zones in northern Spain (Steiner et al., 1985/1986; Ju~irez et al., 1994, 1995); however, the correlation between land sections and oceanic anomaly records remains somewhat tenuous. The difficulty in correlation is partly a result of discontinuous and low mean sedimentation rates (---1-3 m/My) in the condensed limestone facies. Similarly condensed Callovian-Oxfordian sediments in Monti Lessini (northern Italy) yield polarity reversals and sporadic ammonite control (Channell et al., 1990a) but the polarity pattern cannot be correlated to the oceanic magnetic anomaly record. The existence of polarity reversals in the Callovian-Oxfordian is confirmed by studies of short sections from the Krakow Uplands (Poland) (Ogg et aL, 1991a); however, here again the lack of long, continuously deposited sedimentary sections does not allow a convincing correlation to the oceanic anomaly record. Although the magnetostratigraphic correlation to the M26-M38 oceanic magnetic anomaly record has not been achieved, it is clear that the Jurassic "quiet zone" in the central Atlantic magnetic anomaly record is not due to a prolonged interval of normal polarity, as had been implied by magnetostratigraphic study of the Valdorbia section (central Italy) (Channell et al., 1984). It is now clear that the Callovian-Oxfordian interval, which correlates to the Jurassic quiet zone, was an interval of frequent polarity reversal (Fig. 11.8, Table 11.2).
c. Pre-Caliovian Jurassic Magnetic Stratigraphy For the Bajocian and Bathonian, several sections from southern Spain indicate a very high frequency of polarity reversal (Steiner et al., 1987), an
11.2
Jurassic Magnetic Stratigraphy
20|
average reversal rate of at least 5.5 reversals/My for the Bajocian. The mean sedimentation rate in these sections is in the 1-4 m/My range. The high frequency of reversal and the lack of any discernable "fingerprint" in the polarity zone patterns have precluded clear correlation among land sections. The elucidation of the magnetic stratigraphy in this interval will be aided by studies of more expanded sections. Such sections occur in central Italy but they lack ammonites and therefore await refinement of nannofossil and radiolarian biostratigraphies in this interval. One of the most important magnetostratigraphic studies in the Jurassic is that of Horner and Heller (1983) from the Breggia section (southern Switzerland) (Fig. 11.9). The sedimentation rates in the nodular limestones at Breggia are about 14 m/My for the Pliensbachian and 4-7 m/My of the Toarcian and Aalenian. These sedimentation rates are several times greater than for more typical Ammonitico Rosso-type limestones, and this results in a considerable improvement in the clarity of the magnetostratigraphic record. In addition, the ammonite biostratigraphy for the Pliensbachian-early Bajocian interval at Breggia has been determined in detail by Wiedenmayer (1980). Mfirton et al. (1980) acquired a magnetic stratigraphy from the VGP LATITUDE .90 ~ 0o +90oP~
AMMONITE ZONES Stage
VGP LATITUDE -90
(Ma)
~
0 ~
+90 ~
A M MONI TE ZONES Polarity
Stage ,~ (Ma)
sowerbyi oo m
margari-z__.
220
176.5
tatus
~
192
"' ..J
sonae
_
davoei
E2
murchi- ~,~
opalinum
~ 2oo g
180.1
~5
meneghinii
ibex
~o ~8o
i
8
erbaense
bifrons
falciferum z
%1
,.me.on,
189.6
spinatum ~ 0 a
Figure 11.9 Carixian (Pliensbachian) to Bajocian magnetic stratigraphy and ammonite zones at Breggia (Switzerland) (after Horner and Heller, 1983).
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9-m-thick Bakonycsernye section (Hungary). Here sedimentation rates in the Pliensbachian are about 1.5 m/My and 10 reversals are recognized in this stage. Pliensbachian sections in Italy with similar sedimentation rates yielded comparable numbers of reversals (Channell et aL, 1984). However, at Breggia, the sedimentation rate for the Pliensbachian is an order of magnitude greater (---14 m/My) and 39 reversals are recognized in the stage. Correlation between Breggia and Bakonycsernye shows that seven normal polarity zones at Breggia have been concatenated into one at Bakonycsernye. There is clearly a problem in resolving complete magnetic stratigraphies in the Ammonitico Rosso-type facies when sedimentation rates are a few meters/My, probably because of frequent lacunae even in sections where ammonite finds imply continuity of sedimentation. The Toarcian stratotype sections at Thouars and Airvault (France) are gray marls and limestones, and their magnetic stratigraphies have been resolved by Galbrun et al. (1988a). As the sections are about 5 m thick and the entire stage is represented, the mean sedimentation rates are less than 1 m/My. Nonetheless, a reasonable magnetostratigraphic correlation can be made from the stratotype sections to the Breggia section. The magnetic stratigraphy provides a means of correlation of the West European ammonite zonation in the stratotype sections to the Tethyan ammonite zonation at Breggia. For the Hettangian and Sinemurian, three red nodular limestone sections in Austria (at Kendelbach Graben and Adnet) have been studied by Steiner and Ogg (1988). Correlations among sections are hampered by the condensed nature of the sedimentation and the very poor biostratigraphic control in these sediments. The same problems affect gray/white pelagic limestones of this age in central Italy (Channell et aL, 1984). The best quality Hettangian/Sinemurian magnetic stratigraphy is from a core drilled in the Paris Basin (Yang et aL, 1996) indicating high reversal frequency in the vicinity of the Hettangian-Sinemurian stage boundary.
11.3 Correlation of Late Jurassic-Cretaceous Stage Boundaries to the GPTS Late Jurassic and Cretaceous chronostratigraphy is based on stage stratotypes defined by ammonite zones. However, due to absence or uneven distribution of ammonite faunas in land sections and oceanic cores, Cretaceous chronostratigraphy is often based on calcareous microplankton biostratigraphy and the supposed correlation of these events to ammonites. A review of calcareous nannofossil events in sections with ammonites, microplankton, or magnetic stratigraphy has revealed the uncertainties in correlation of nannofossil and calpionellid datum planes to stage boundaries (Figs.
11.3 Correlation of Late Jurassic-Cretaceous Stage Boundaries to the GPTS
~0~
11.6 and 11.7). All the nannofloral datums have been directly correlated to polarity chrons. Ammonite biozones have been directly correlated to magnetic stratigraphy in parts of the Oxfordian-lowermost Valanginian (see Ogg et al., 1991c), Valanginian-Hauterivian (Channell et aL, 1995b), and uppermost Hauterivian-Barremian intervals (Cecca et al., 1994). The Oxfordian/Kimmeridgian boundary is correlative to the base of the Sutneria platynota ammonite zone, which has been correlated to CM25 in southern Spain (Ogg et al., 1984). The Kimmeridgian/Tithonian boundary is correlative to the base of the Hybonoticeras hybonotum ammonite zone, also in southern Spain (Ogg et aL, 1984). The Tithonian/Berriasian (Jurassic/Cretaceous) boundary does not have a universally accepted definition. Many of the candidate biomarkers have been correlated to the polarity chrons (Ogg and Lowrie, 1986; Channell and Grandesso, 1987; Bralower et al., 1989; Ogg et al., 1991c). The base of CM18 has become the generally accepted correlation to the Tithonian/ Berriasian boundary. The Berriasian/Valanginian boundary is defined by the base of the T. otopeda ammonite zone and falls within CM15n (Ogg et al., 1988) and between the first occurrence (FO) of Cretarhabdus angustiforatus and the FO of Calcicalathina oblongata (Fig. 11.6). The Valanginian/Hauterivian boundary coincides with the base of the A. radiatus ammonite zone and is close to the FO of Nannoconus bucheri and at the base of CM11n (Channell et al., 1995b). The base of the S. hugii ammonite zone defines the Hauterivian/Barremian boundary, which falls between the last occurrence (LO) of Lihtraphidites bollii and the LO of Calcicalathina oblongata and in the upper part of CM4 (Cecca et al., 1994; Channell et aL, 1995b). The Barremian/Aptian boundary was formally defined at the first occurrence of Deshayesites. None of the nannofossil events proposed by Thierstein (1973) to define this boundary have proved to be reliable. The FO of Rucinolithus irregularis is correlated to the upper part of the C. sarasini ammonite zone and is therefore slightly older than the Barremian/ Aptian boundary (Channell and Erba, 1992). The base of CM0 coincides closely to this boundary, but direct correlation of this polarity chron with the ammonite biozone has not been documented. The Santonian-Campanian is formally defined by the appearance of the ammonite Placenticeras bidorsatum, the index species of the oldest Campanian ammonite zone. Unfortunately, this species is extremely rare even in the type area (northwest Europe) and the Santonian-Campanian boundary is often informally defined on the basis of the FO of the nannofossil Broinsonia parca and/or the FOs of foraminifera Globotruncana arca and Bolivinoides strigillatus. The microfossil markers of the SantonianCampanian boundary result in a correlation of this boundary to the basal
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part of C33r, close to the top of the Cretaceous normal superchron (e.g., Alvarez et al., 1977; Channell et al., 1979; Monechi and Thierstein, 1985). The type area of the Campanian-Maastrictian boundary (northwest Europe) is characterized by a major hiatus, and hence there is more than average debate over the definition of this stage boundary. In the pelagic realm, the LO of the foraminifera Globotruncanita calcarata is often used as an informal definition, and this event usually appears in the top part of C33r (e.g., Alvarez et al., 1977).