地
2012 年 10 月
第 33 卷 增刊 1: 25-28
www.cagsbulletin.com
报
Oct. 2012
Acta Geoscientica Sinica
球
学
Vol.33 Supp.1: 25-28
www.地球学报.com
doi: 10.3975/cagsb.2012.s1.14
西南日本秋吉带石炭系高山(Ko-yama)灰岩群的
石炭纪(Visean – Moscovian)牙形石序列
Carboniferous (Visean–Moscovian) Conodont Faunal Succession in
the Ko-yama Limestone Group, Akiyoshi Belt, SW Japan:
the Biostratigraphic Resolution in the Clastic Carbonate
Sedimentary Field
Keisuke ISHIDA1), Sigeyuki SUZUKI 2), Noriyuki INADA2), Shinji YAMASHITA2)
1) Laboratory of Geology, Institute of SAS, Tokushima University, 770-8502, Tokushima, Japan;
2) Dept. Earth Sci., Okayama University, 700-8530, Okayama, Japan
Abstract: The Carboniferous conodont faunal succession of the lower part of Ko-yama Limestone Group was
studied. The confirmed upper Visean–lower Moscovian lithostratigraphy of the group is characterized by the clastic carbonates with common association of the basaltic pyroclastics and some intercalation of spicular chert beds.
The faunal succession of Gnathodus semiglaber (upper Visean), Gnathodus praebilineatus – Lochriea multinodosa
(upper Visean), Lochriea ziegleri – Gnathodus girtyi girtyi s.l. (lower Serpukhovian), Neoganthodus symmetricus
– Idiognathodus primulus (middle – upper Bashkirian), and Idiognathoides convexus – Gondolella clarki (lower
Moscovian) faunas, appears in concordance with the lithostratigraphic order. The faunas are correlative with those
from the conodont zones of the Hina, Atetsu, Akiyoshi and Omi limestone groups in the Akiyoshi Belt. The
Visean/Serpukhovian boundary of the section was recognized by the FAD of Lochriea ziegleri.
Key words: conodont; Ko-yama Limestone; Carboniferous; Akiyoshi Belt; SW Japan
1
Introduction
The Carboniferous conodont biostratigraphy in
Japan has been studied mainly in the 20th Century
(Igo and Koike, 1964; Koike, 1967; Igo, 1973; Igo and
Kobayashi, 1974; Watanabe, 1975; Igo and Igo, 1979;
Haikawa, 1988). The Middle Carboniferous conodont
zonation has been studied in relation with the Mississippian–Pennsylvanian boundary in the Hina Limestone of the Akiyoshi Belt (Mizuno, 1997). The Akiyoshi Belt is regarded as one of the Permian accretionary complexes in the Inner Zone of SW Japan
(Isozaki, 1997; Sano et al., 2004). The complex encompasses large limestone masses, as they are well
known as the Akiyoshi, Taishaku, Atetsu, Hina, and
the Ko-yama limestones with associations of basaltic
pyroclastics on their bases. On the sedimentology of
the Akiyoshi Limestone Group, Nakashima and Sano
(2007) gave the implication that the limestone group is
of a resedimented origin shed from Mississippian –
Permian mid-oceanic atoll-type buildup into
slope-to-basin facies.
E-mail: [email protected].
We studied the conodont faunas of the lower part
of Ko-yama Limestone Group in NW of Okayama
with respect to the biostratigraphic resolution in the
clastic carbonate sedimentary field. The obtained faunal succession that appeared in concordance with the
lithostratigraphic order was correlative with those of
global Visean, Serpukhovian, Bashkirian and
Moscovian stages, respectively. The Visean/ Serpukhovian boundary of the section was considered to be
represented by the occurrence of Lochriea species (e.g.
Blanco-Ferrera, et al., 2005; Groves et al., 2003; Higgins, 1975; Kullmann et al., 2008; Nemyrovska, 1999,
2005; Nikolaeva, et al., 2009; Somerville, 2008).
2 Geological setting of the Ko-yama
Limestone Group
The Ko-yama Limestone (Yokoyama et al., 1979)
in the Ko-yama Limestone Group (after Yoshimura,
1961: Koyama Group) is one of the large masses in the
Akiyoshi Belt. The biostratigraphic research revealed
that the Ko-yama Limestone ranges from Carboniferous to Middle Permian. The six foraminifer-zones of
26
Acta Geoscientica Sinica
Endothyra, Millerella, Pseudostafella, Profusulinella,
Fusulinella–Fusulina,
and
Pseudoschwagerina–
Parafusulina were recognized (Yokoyama et al.,
1979).
The lower part of the Ko-yama Limestone Group
is mainly composed of clastic carbonates, which are
dominated by the crinoid–bryozoan bioclastic packstone. These carbonates were considered to be formed
by the transportation of carbonate clasts into the chert
depositional deeper open sea bottom (Yokoyama et al.,
1979). According to the shed-model (Nakashima and
Sano, 2007), the limestone–basaltic pyroclastic sequence with association of the spiculite cherts in the
Akiyoshi Limestone Group is suggestive as a marginal
deeper and slope facies of the mid-oceanic atoll-type
buildup.
3 Faunal succession of the lower part of
the Ko-yama Limestone Group
Among the extracted conodont materials, P1 elements were used for the chronological analysis. The
faunas appear in concordance with the lithostrati-
Fig. 1
Vol.33
graphic order (Inada et al., this issue), and are correlative with the faunas from the studied conodont zonation in the Akiyoshi Belt (Fig. 1). The faunal succession of the lower part of the Ko-yama Limestone
Group is as follows in ascending order.
Gnathodus semiglaber Fauna (upper Visean): is characterized by the occurrence of Gnathodus semiglaber.
The fauna was obtained from a wackestone block in
the basaltic pyroclastics at the basal part of the group.
Gnathodus praebilineatus – Lochriea multinodosa
Fauna (upper Visean): is composed of Gnathodus
praebilineatus, Gnathodus ex. gr. bilineatus, Pseudognathodus homopunctatus, Lochriea multinodosa,
Lochriea commutata, and Cavusgnathus unicornis.
Lochriea ziegleri – Gnathodus girtyi girtyi s.l. Fauna
(lower Serpukhovian): in addition to Lochriea ziegleri,
Gnathodus ex. gr. bollandensis and Vogelgnathus
campbelli, transition forms of Gnathodus girtyi girtyi
s.l. to G. girtyi simplex, and Lochriea nodosa s.l. to L.
crusiformis were recognized from the lower horizons.
Neoganthodus symmetricus – Idiognathodus primulus Fauna (middle–upper Bashkirian): is composed of
Correlation of the conodont zones in the Akiyoshi Belt, Japan
Supp.1
Keisuke ISHIDA et al.: Carboniferous (Visean–Moscovian) Conodont Faunal…
Neoganthodus symmetricus, Idiognathodus primulus,
Idiognathodus sp. 1, Idiognathodus sp. 3, and Streptognathodus expansus. The fauna from a particular
horizon contains reworked upper Visean to Serpkhovian elements of Gnathodus semiglaber, Gnathodus sp.
1, Pseudognathodus homopunctatus, and Vogelgnathus
postcampbelli.
Idiognathoides convexus – Gondolella clarki Fauna
(lower Moscovian): is composed of Gondolella clarki,
Gondolella sp. 1, Idiognathoides sulcatus sulcatus,
Idiognathoides macer, Idiognathoides attenuates,
Idiognathoides convexus, Idiognathodus delicatus s.l.,
Streptognathodus suberectus, Neognathodus bothrops,
Neoganthodus symmetricus, and Idiognathodus sp. 1.
27
HAIKAWA T. 1988. The basement complex and conodonts biostratigraphy of the Lowest parts in the Akiyoshi Limestone
Group, Southwest Japan. Bulletin of the Akiyoshi-Dai Museum of Natural History, 23: 13-37, pls.4-7.
HALLAM A. 1992. Phanerozoic sea-level changes. New York:
Columbia University Press: 266.
HIGGINS A C. 1975. Conodont zonation of the late Visean – Early
Westphalian strata of the south and central Pennines of northern England. Bulletin of the Geological Survey of Great Britain, 53: 1-90, pls. 1-18.
IGO HH. 1973. Lower Carboniferous conodonts from the Akiyoshi
Limestone Group, southwest Japan. Trans. Proc. Palaeont. Soc.
4
Results and Discussions
Conodont faunal succession: The conodont faunas from the lower part of the Ko-yama Limestone
Group were studied with respect to the biostratigraphic reliance in the “clastic carbonate” sedimentary
field. The existence of conodont faunal succession as
well as the faunal stability was basically confirmed.
The conodont faunal succession is: Gnathodus
semiglaber Fauna (upper Visean), Gnathodus praebilineatus – Lochriea multinodosa Fauna (upper Visean),
Lochriea ziegleri – Gnathodus girtyi girtyi s.l. Fauna
(lower Serpukhovian), Neoganthodus symmetricus –
Idiognathodus primulus Fauna (middle – upper Bashkirian), and Idiognathoides convexus – Gondolella
clarki Fauna (lower Moscovian). The faunas are correlative with those from the conodont zones of the
Hina, Atetsu, Akiyoshi, and Omi limestone groups in
the Akiyoshi Belt, respectively.
Visean/Serpukhovian boundary in the section:
The FAD of Lochriea ziegleri in the study section
marked the Visean/Serpukhovian boundary.
Mixed fauna in relation with the early Bashkirian global low-standing eustatic condition: A
reworked Serpukhovian and older elements were recognized in some Neoganthodus symmetricus – Idiognathodus primulus Fauna (middle – upper Bashkirian)
from the particular clastic carbonate horizon. The
early Bashkirian global low-standing eustatic condition (ex. Hallam, 1992; Nakazawa and Ueno, 2009)
might be considered for the erosional event in the
provenancial shallow-carbonate buildup.
Japan, N.S., 92, 185-199, pl.29.
IGO HY, IGO HH. 1979. Additional note on the Carboniferous
conodont biostratigraphy of the lowest part of the Akiyoshi
Limestone Group, southwestern part of Japan. Annual Rep.
Inst. Geosci., Univ. Tsukuba, 5, 47-50.
IGO HY, KOBAYASHI F. 1974. Carboniferous conodonts from the
Itsukaichi district, Tokyo, Japan. Trans. Proc. Palaeont. Soc.
Japan, N. S., 96, 411-426.
IGO HY, KOIKE T. 1964. Carboniferous conodonts from the Omi
Limestone, Niigata Prefecture, Central Japan. Trans. Proc.
Palaeont. Soc. Japan, N. S., 53, 179-193.
INADA T, SUZUKI S, ISHIDA K, YAMASHITA S. 2012. Folded
structure
of
the
Carboniferous
Ko-yama
Limestone
Group, Akiyoshi Belt, SW Japan. Acta geoscientica sinica,
33(s1): 24.
ISOZAKI Y. 1997. Jurassic accretion tectonics of Japan. The Island
Arc, 6, 25-51.
KOIKE T. 1967. A Carboniferous succession of conodont faunas
from the Atetsu Limestone in Southwest Japan (Studies of
Asiatic conodonts, Part VI). Science Reports of the Tokyo
Kyoiku Daigaku, Section C, 93, 23-62, pls.1-4.
KULLMANN J, MIROUSE M-F P, DELVOVE J-J. 2008. Late
Visean/Serpukhovian goniatites and conodonts from the Central and Western Pyrenees, France. Geobios, 41: 635-656.
MIZUNO Y. 1997. Conodont faunas across the Mid-Carboniferous
boundary in the Hina Limestone, Southwest Japan. Paleon-
References:
tological Research, 1(4): 237-259.
BLANCO-FERRERA S, GARCIA-LOPEZ S, SANZ-LOPEZ J.
NAKASHIMA K, SANO H. 2007. Palaeoenvironmental implica-
2005. Carboniferous conodonts from the Cares river section
tion of resedimented limestones shed from Mississippian –
(Picos de Europa Unit, Cantabrian Zone, NW Spain). Geobios,
Permian mid-oceanic atoll-type buildup into slope-to-basin
38: 17-27.
facies, Akiyoshi, Japan. Palaeogeography, Palaeoclimatology,
GROVES J R, LARGHI C, NICOLA A, RETTORI R. 2003. Mississippian (Lower Carboniferous) microfossils from the Chios
Mélange (Chios Island, Greece). Geobios, 36, 379-389.
Palaeoecology, 247: 329-356.
NAKAZAWA T, UENO K. 2009. Carboniferous-Permian long-term
sea-level change inferred from Panthalassan oceanic atoll
28
Acta Geoscientica Sinica
stratigraphy. Palaeowarld, 18: 162-168.
NEMYROVSKA T I. 1999. Bashkirian conodonts of the Donets
Basin, Ukraine. Scripta Geologica, 119, 1-115, with an appendix by Samankassou, E.
NEMYROVSKA T. I. 2005. Late Visean/early Serpukhovian
conodont succession from the Triollo section, Palencia (Cantabrian Mountains, Spain). Scripta Geologica, 129: 13-89.
NIKOLAEVA S V, AKHMETSHINA L Z, KONOVALOVA V A,
Vol.33
global cooling and sea-level change: Akiyoshi, Japan. Palaeogeography, Palaeoclimatology, Palaeoecology, 213: 187-206.
SOMERVILLE I D. 2008. Biostratigraphic zonation and correlation of
Mississippian rocks in Western Europe: some case studies in the
late Visean/Serpukhovian. Geological Journal, 43: 209-240.
WATANABE K. 1975. Mississippian conodonts from the Omi
Limestone, Niigata Prefecture, Central Japan. Trans. Proc.
Palaeont. Soc. Japan, N. S., 99: 156-171.
KOROBKOV V F, ZAINAKAEVA G F. 2009. The Carbonif-
YOKOYAMA T, HASE A, OKIMURA Y. 1979. Sedimentary
erous carbonates of the Dombar Hills (western Kazakhstan)
facies of Koyama Limestone. Jour. Geol. Soc. Japan, 85(1):
and the problem of the Visean – Serpukhovian boundary. Pa-
11-25.
laeoworld, 18: 80-93.
SANO H, FUJII S, MATSUURA F. 2004. Response of Carboniferous – Permian mid-oceanic seamount-capping buildup to
YOSHIMURA N. 1961. Geological studies of the Paleozoic groups
in the Oga Plateau, Central Chugoku, Japan. Sci. Rep. Hiroshima Univ. (Earth Sci.), 10: 1-36.