Bull. Inst. Oceanic Res. & Develop., Tokai Univ.（2010）, 31, 65 − 77

Global Sea Level in the Messinian Stage of the Late Miocene
Masaaki Hanada1）

Abstract
The Leg 13 voyage of the Deep-Sea Drilling Project was implemented in the Mediterranean Sea area andthe evaporite deposits originating in the Messinian period that were discovered on the deep sea ﬂoor in the
Mediterranean Sea as a result of the drilling became a focus of worldwide attention. Scientists aboard shipat the time concluded that the evaporite was formed by the lowering of the sea level by as much as 2,000
meters below the current sea level that occurred only in the Mediterranean Sea（Hsü et al., 1977）. In otherwords, they emphasized that the sea level in the Messinian period was 2,000 meters lower than the current
sea level only in the Mediterranean Sea.
The author surveyed the initial report of the deep sea drilling results of the DSDP, IPOD and ODP andexamined the rise in the sea level in the geological eras. Based on the distribution of shallow sea strata notedin the initial report as thought to have been formed at the site, I concluded that the old sea level at the very
end of the Miocene period was about 2,000 meters lower than it is today（Hanada, 2000）. The phenomenon of
the low sea level in the Messinian period was not only limited to the Mediterranean Sea.
One proof evidencing this is indicated in the results of the deep sea drilling at two drilling sites
implemented during the DSDP Leg 13 voyage. One of them is the drilling at site 120 on the Atlantic side
across the Gibraltar Strait and the other is that at site 121 implemented in the Mediterranean Sea. The
drilling at site 120 was carried out on the northern slope of the Gorringe Bank at the shallowest depth ofabout 50 m located about 260 miles into the Atlantic Ocean. Based on drilling record, an increase in the sea
depth during the Pliocene period and later was evident at the drilling site. That is, site 120 had a sea depthof 1,711 m and Lower Pliocene deposits were found at a depth of about 55 m under the sea bottom. Similar
increased sea depth is also seen in the record of drilling at site 121 implemented in the Western Alboran
Basin in the Mediterranean Sea. Speciﬁcally, Trubian deposits overlapping unconformably on Messinian
evaporite in the Mediterranean Sea are said to be abyssal based on the analysis of deep foraminifera andostracodes contained in the deposits. It is consequently clear at the present time that the Mediterranean Sea
was not isolated from the Atlantic Ocean.

1. Introduction
It is widely accepted that the sea-level in theWestern Mediterranean in Late Miocene times（theMessinian Stage）was 2000 meters lower than that ofthe present Mediterranean Sea. This paper sets out
to suggest that, in fact, the sea level in the Western
Mediterranean was not a local phenomenon, but waspart of a global picture.
Hoshino（1962）claimed in the past that the1） Department of Marine Mineral Resources, School of Marine Science and Technology, Tokai University,
Orido, Shimizu-ku, Shizuoka 424-8610, Japan（2009 年 11 月 11 日受付／ 2009 年 12 月 15 日受理）

3-20-1

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Masaaki Hanada

sea-level of the Late Miocene was the uniformity

The authors has perused the initial report ofof the water depth of the termination of deep sea

the results of the global deep sea drillings by DSDP

canyons, water depth of the upper margins of deep

and ODP and examined the rise in the sea level in

sea terraces and the continental rise found on thethe Late Miocene era based on the distribution ofseabed throughout the world.

shallow sea formations thought to have been formed

A total of four deep sea drillings have been

locally. As a result, he concluded that the global

made in the Mediterranean Sea, the DSDP Leg 13

paleo-depth in the late Miocene was approximately

in 1970, DSDP Leg 42A of 1975, Leg 107 in 1987 and2000 meters lower than it is today（Hanada, 2000）.

ODP Leg 161 in 1995. Among these, the discovery

In other words, the low sea level of the Messinianof evaporates of the Messinian Stage from the deep

period was not limited to the Messinian Sea alone.

seabed in the Mediterranean Sea on Leg 13 Cruise,

In this study, I presents wide ranging geologicalthe ﬁrst drilling cruise in the Mediterranean Sea,

evidence that the sea level around the world in theattracted worldwide attention.

late Miocene was some 2000 meters lower than it is

The scientists on board at the time concluded
that the evaporites were caused by a drop in the sea
level by as much as 2000 meters due to seawater
evaporation in the Mediterranean Sea（Hsü et al.,today.

2. Origin of the western Mediterranean basins
2.1 Geological origin1973）. In other words, they emphasized that only

Comas et al.（1999）announced the pattern

the water level in the Mediterranean Sea was somediagram based on an analysis of the records of2000 meters lower in the Messinian than it is today.

seismic exploration conducted in the Alboran

There is no explanation whatsoever, however, of theBasin area in the western part of the westernreason why the Mediterranean Sea evaporated to a

Mediterranean Sea. According to this, it can be seenlevel 2000 meters lower than today or what caused

that the basement of the Alboran basin is about 6

evaporations that were repeated eight times as

km below present sea level. This is indicated in the

Hsü et al（1973）estimated from the volume of thebasement depth contour map（Fig. 1）. Watts et al.

evaporite.

（1993）claimed that the sedimentary sequence of theFig. 1 Basement depth contour map of the Málaga Graben（de la Linde et al., 1996）. Contour lines every 100
ms（TWT）, showing Andalucía-G1（And-G1）, Alborán-A1（Alb-A1）, DSDP 121 and Site 976 locations.
Both ﬂanks of the graben correspond to complex interference of formar dubmarine or formerly
emerged surfaces and low- and high-angle faults, normal-oblique transfer faults, and tops of rollover
structures affecting the basement（after Comas et al., 1999）.

Global Sea Level in the Messinian Stage67

2-2 Origin of the Gibraltar Strait
The Gibraltar Strait is a strait linking theAtlantic Ocean and the Mediterranean Sea with awidth of about 15 km with the shallowest depth ofless than 300 meters.
Van Couvering et al.（1976）pointed to thestructural upheaval prior to the Messinian period
in the same area. It is thought, however, that theupheavals in this period took place no more than2000 meters lower than the present sea level.
That is, the beginning of the sill that was createdby the upheavals at this time did not go so far as
to totally isolate the Mediterranean Sea from theAtlantic Ocean. However, since an incomplete sill
was created, the circulation of seawater in the
Mediterranean Sea deteriorated markedly andFig. 2 Development of a central platform andits marginal geosyncline（after Hoshino, 1991）.

it is thought that this promoted the evaporationof seawater. The current Gibraltar sill was notcompleted in the Messinian period, which isproven by the short-term exchange of terrestrial

Alboran Sea Basin has a thickness of 6-8 km and,mammals between Spain and Africa at the end offurthermore, Chalovan et al.（1997）stated that thethe Pliocene period（DeBoajen, 1973）.

sedimentary column at the center of the Alboran

There are many researchers who explain

sedimentary basin is at least 9 km thick. Thesethe origin of Mediterranean basins by means ofresults, however, were obtained using the seismic

plate tectonics（Calvert et al., 2000, and Mejgs

refraction method and it should pointed out that theand Burbank, 1997）. However, with regard to thebed of the sedimentary layer is not distinct.

evaporates of the late Miocene period, it is known

Hoshino（1991）stated that the existence ofthat evaporite exists at a depth of 2000 meters

a basement at some 6 km below the present sea

below the current sea level in the Red Sea（Ross etlevel is also known in the Tyrrhenian Basin in theal., 1973）. The explanation by the plate-tectonicists

Mediterranean Sea as Well as in the Japan Sea

is the Mediterranean basin is due to the subduction

Basin, North Sea Basin, Pannonian Basin, Westof the Aﬂica plate under the Eurasia plate and that

Siberian Lowland, Song-Liao Basin in China and thethe Red Sea is due to the stretching of the Africa

Venazuelan Basin. He conclueded that the basins

plate and Arabian plate. The two basins caused

are remnant basins and furthermore advocated theby differing mechanisms with the same sea levelmechanism as shown in Fig. 2 for the formation ofin the Messinian period is, the author believes, aremnant basins. He asserts that these sedimentary

reﬂection of the fact that the sea level at the timebasins are the result of a large-scale rise of the sea

was globally 2000 meters lower than today. The Red

level and surrounding mobile belts following A）

Sea and Mediterranean Sea were connected during

unheaval og the central massif in the Hercynian, B）

the Miocene period and the connection to the Indian

followed by erosion, peneplanation and sedimentation

Ocean occurred during the Pliocene period or laterin the peripheral alpine geosyncline and C）sea level（Hoshino, 1998）. In other words, the Red Sea andrise and uplift of gyosynclinal materials.

Mediterranean Sea were connected during the late

68

Masaaki Hanada

Miocene period, which indicates that evaporite wasformed successively in this series of basins.

2-3 Messinian period sedimentary stratum in the
Gulf of Cadiz（Unit M3）

The unconformity that is occurs worldwide

The Gulf of Cadiz is a part of the North Atlantic

between the late Miocene and early Pliocene

continental margin on the northwest side of theindicates that emergence in the Messinian and theStrait of Gibraltar. The occurrence of the Messinianrise of sea level in the early Pliocene were on aformation in the Gulf of Cadiz, in a drilling near

global scale.

shore（B3）（see Fig. 3）is at a depth of 1250 meters
below present sea level（Maldonado et al., 1997）and

Fig. 3 a : Simppliﬁed bathymetric chart of the Gulf of Cadiz. The multichannel seismic proﬁle and location ofcommercial wells is shown（after Maldonado et al., 1999）. b: The interpretative line drawing showing
representative cross-section of the northern Gulf of Cadiz（Line 339）
（ after Maldonado et al., 1999）.

Global Sea Level in the Messinian Stage

69

Unit M3（upper Messinian deltaic sediments）evident

this is the fact that the rise in the sea level after thein the acoustic traverse through the vicinity has

Messinian period, during which the continental slope

a water depth of about 0.8 sec（TWTT）and layer

was formed, was global event.

thickness of about 1.2 sec（TWTT）and, if the Vp in

Shepard（1963）notes that the terminal depth of

this formation is about 2.3 km / sec（TWTT）（Sartori

continental slope is at −2000 meters. This is probably

et al., 1994 ; refer to Fig., Line A）, the upper portion

an indication of a major upheaval in the portionof this Messinian stratum would be located at afrom the lower part of the continental slope to thedepth of 2 km below sea level, equivalent
to the depth of the contemporaneous
evaporates in the Mediterranean Sea,
thus indicating that sea level in the
Mediterranean Sea during the Messinian
period is the same as that of open ocean.
Hoshino（1981） asserts that shallow
autochthonous sediment and shallow sea
fossils of the same period distributed in
the deepest areas in the seabed indicate
the sea level of the geological era withwhich these are afﬁliated. Maldonado etal.（1999）think that this area was exposed
to rapid crustal subsidence in the early
Pliocene; however, the depth of Unit M3
is the same as the Messinian evaporates
in the western Mediterranean Sea andthe evaporitic layer is thought to havebeen formed in response of the − 2000
meters sea level occurring globally. The
rapid crustal submergence of the early
Pliocene refers to the large-scale risein sea level as indicated by changes in
the paleo-depth of benthic foraminifera
referred to later.

3. Geological evidence indicating thesea level in the late Miocene period
3-1 Hypsographic curve
In the case of the MediterraneanSea, Cita （1973）pointed out that the
hypsographic curve in the Mediterranean
Sea is similar to that in the open ocean,t h ough the reason for that is not
explained. The primary cause involved inFig. 4

Deep sea terrace in the Kumano-Nada Sea, off central
Honshu, Japan.

70

Masaaki Hanada

continent in the Neotectonic Period taking the depth

and other locations on land along the Mediterranean

in the vicinity of −2000 meters as the standard,

Sea coast（Butler et al., 1995; Hsü et al., 1973）.

that is, with this major upheaval in the Neotectonic

Deep-sea terraces are evident in many locations

Period, there were conspicuous upheavals in thein the vicinity of -2000 meters. In the case of Japan,

area from the continental margin to the inland area

the deep-sea terrace offshore in the Kumano Nada iswhile the major part of the sea basin bed remained

well known（Fig. 4）. Many of the deep-sea terraces

immobile. As evidence of this, the point can be citedare sedimentary basins that have a peripheral dam

that the Messinian evaporite widely distributed aton the ocean side and sedimentary accumulation

the bottom of the basin in the Mediterranean Sea

on the shore side, which form the terrace. Erodedis hardly distributed at all. Meanwhile, the same

bedrock was found in the peripheral dam on theevaporates are also distributed on the Island of Sicily

outer side of the deep-sea terrace of offshore Shikoku

Fig. 5Bathymetric chart of the continental margin between Britany and Ireland（after Day, 1959）.
Depths in fathoms.

Global Sea Level in the Messinian Stage

Fig. 671

Kamogawa Submarine Canyon.

in Japan through acoustic exploration, indicating

pointed out that Mississippi Canyon continues to a

the location of the sea level at the time（Hilde et

depth of about 2000 meters（Gealy, 1965）, that theal., 1969）. In addition, deep-sea terraces at a depth

submarine canyon in the Bering Sea continues atof 2000 meters dating from the Middle Miocene

depths from 165 meters to 2200 meters, the upper

are partially developed from northern Honshu tomargin of the continental rise（Scholl et al., 1968）,

Hokkaido on the Japan Sea side, in particular, athat the Martaban Canyon in the Andaman Sea

clearly-deﬁned deep-sea late Miocene erosionalends at a depth of 2000 m（Rodolfo, 1969）, and thatterrace is distributed in the area from southwest

the gradient of the valley axis of the Black Mudoffshore Okushiri Island to the Tsugaru Strait.

Canyon in the western part of the English Channel

Among deep-sea terraces in the northern

moderates at a depth of 1800-2000 meters, which

Atlantic Ocean, the Meriadgek Terrace（Day, 1959）

corresponds to the depth of the Meriadgek Terrace

in the western part of the English Channel, at a（Day, 1959）. The same occurs off the eastern

depth of about 2000 meters, is noteworthy（Fig. 5）.

coast of the United States. In addition, the Kahana
Canyon distributed on oceanic islands such as Oahu

3-2 Submarine canyons
Submarine canyons which terminate at a depthof 2000 meters are found throughout the world.
There are numerous examples of submarine

Island, Hawaii, also has a terminal depth of 2000
meters（Hamilton, 1957）and, moreover, according to
Shepard and Dill（1966）, many submarine canyons
have a terminal depth of −2000 meters.

canyons with a terminal depth in the range of

As in the case of the Kamogawa Submarine

about 2000 meters. For example, it has been

Canyon（Fig. 6）, there are also submarine canyons

72

Masaaki Hanada

with valley topography that extends even deeper
than 2000 meters and, given the valley topography
extending deeper than 2000 meters insuch cases,
they are unusual valleys with a trough conﬁgurationand steeper valley axis gradients than at shallower
depths, and we can see the submarine canyons withthe same nature at the Korean continental slope of
the Sea of Japan.
Submarine canyons are frequently explained
to be created by turbidity currents ; it would
be difﬁcult at present, however, to say that all
submarine canyons are formed by such turbidity
currents（Hoshino, 1998）. It is evident from thedeep-sea topography of Toyama Bay（Hanada, 1982）
that the canyon loses form at the level surface of thebay at a depth of 1000 meters and that the canyon
topography continues on to a depth of 2000 meters
further out. In other words, turbidity currents
originating near the coastline are not able to explain
the origin of submarine canyons that cut into thelower part of the continental slope.
3-3 Examination of change in the sea levelindicated by benthic foraminifera

Fig. 7

Percent planktonic foraminifera at Buff Bay（after Katz and Miller, 1993）.

Hanagata et al.（2001）claim that the disappearanceof the benthic foraminifer Spirosigmoinella compressa

a rapid increase in water depth of about 2 km

from the Japan Sea and the appearance of Miliammina

after the Messinian period at both DSDP Sites 682

echigoensis into the Japan Sea indicate changes

and 688. They considered the subsidence of thein maritime conditions in the Japan Sea at thecontinental margin to be the cause of this increaseboundary between the Miocene and Pliocene periods.

in depth; however, this phenomenon should probably

Further, reporting on a large-scale rise in sea level

be seen as the result of a rise in sea level after theafter the Messinian based on an examination of

Messinian period.

paleo-depth from the benthic foraminifers, theyAs the result of research in benthic foraminifera

claim that this phenomenon after the Messinian

in marine deposits of the Neogene and Quaternary

period is the result of a major rise in the sea level of

periods along the coast of Jamaica, Katz and Miller

global magnitude. That coincides with the assertion（1993）released charts indicating that the paleo-of Benson（1972）, based on the paleoecology of

depth in the Messinian period was shallower, that

ostracodes, that there was a rapid rise in sea level

unconformities occurred and that, at the beginning

extending to 1000 meters after the formation of theof the Pliocene, the sea depth increased once again

Messinian evaporite.

（Fig. 7）, just as in the Mediterranean Sea. ThisIn account of the continental margin of offshore

indeed corresponds to eustatic changes in the sea

Peru, Suess et al.（1988）concluded, based on anlevel curve from the Miocene to the Pliocene in theanalysis of benthic foraminifera, that there wasMediterranean Sea（Hoshino et al., 2001）（Fig. 8）.

Global Sea Level in the Messinian Stage73

The previously referenced Hanagata et al. and vonAtlantic side across the Strait and Site 121 carried

Huene et al. also have much the same to say.

out in the Mediterranean Sea. Site 120 is located in

In Fig. 7, it is thought that the basin became

the Atlantic Ocean about 260 miles west-northwest

shallower in depth in the Messinian period not asof the Strait of Gibraltar and the drilling was carrieda result of the drop in the sea level but because

out on the north slope of the Gorringe Bank, which

the basin became shallower as it became ﬁlled in.

has a depth of about 50 meters at the shallowest

This phenomenon represents the conclusion ofpoint. Based on the record, it is clear from thestratigraphic geological research relating to oil in

results of the analysis of benthic foraminifera that

the Tertiary of the northeastern Japan Sea（Suzuki,

the sea had increased in depth since the Pliocene at1989）. Von Couvering et al.（1976）point out thethis drilling point（Shipboard Scientiﬁc Party, 1973）.

increased shallowness prior to the Messinian period

In other words, Site 120 had a depth of 1711 metersin the Guadalquivir Trough in Spain based on

and Lower Pliocene was found at a depth of about

research in benthic foraminifera and this is also the

55 meters below the seabed. The same increase in

result of ﬁll, the same as in the case of the Tertiary

depth is also seen in the drilling record of Site 121

Niigata oil ﬁelds.

in the Western Alboran Basin in the Mediterranean

There are results available of the deep sea

Sea（Shipboard Scientiﬁc Party, 1973）. That is,

drilling at two drilling points spanning the Strait

the Trubian stratum that inconsistently overlapsof Gibraltar implemented during the DSDP Leg

the evaporite of the Messinian period in the

13 cruise. These are the results of Site 120 on the

Mediterranean Sea is said to be abyssal as theFig. 8 Sea level change since the late Miocene（aftr Hoshino et al., 2001）.

74

Masaaki Hanada

result of analyses of the benthic foraminifera

Hoshino（1983）classiﬁed the magmatic history ofand ostracodes contained in it（ Benson, 1972）.

the earth into the Granitic Stage（Archeozoic era）,

Consequently, the Mediterranean Sea is not thought

Transitional Stage（Proterozoic and Palaeozoic eras）

to have been isolated from the Atlantic Ocean at thisand Basaltic Stage（Mesozoic and Cenozoic eras）.

time but that the Atlantic Ocean and Mediterranean

What characterized the age since the Mesozoic

Sea had the same sea level.

era, that is, the Basaltic Stage, was basaltic activity

Here, the distribution depth of the Pliocene
seabed at Site 120 has a current depth of 1766 meters,

and he points out that the ocean ﬂoor was rised bybasaltic ﬂooding and its underplating.

somewhat less than 2000 meters, which is due to the

The Messinian evaporates are geologicallyfact that this bank is an upheaval formation area andimportant in that it indicates the level of sea surface

some upheaval is thought to have occurred after theimmediately prior to the major global upheavals inaccumulation of Pliocene sediment.

the Neotectonic Stage Age that formed the entire

Thus, examples in marine areas of Lower

topography of the present-day earth.

Pliocene overlapping Miocene indicating abyssal

Acknowledgments

environment do not only occur in the Mediterranean
Sea but are also known to have occurred in other

I would like to record here our thanks toareas as well. For example, it is said that Lower

Professor Michihei Hoshino, Professor Emeritus

Pliocene fauna indicates abyssal environment as theof Tokai University, for his encouragement toresult of the analysis of the fossil of foraminifers,

write this paper, for his valued discussion. I wish

mollusks, sea urchins and other sea animals in theto express my gratitude to the conveners of theLos Angels sedimentary basin on the west coast of

Session 164, Geology of the Mediterranean area ofNorth America（Conery, 1967）. Furthermore, in the

32nd IGC in Florence, Italy. Our thanks are extended

Japan Sea, the increase in the depth of Japan Sea isto the Professor A.J. Smith, Professor Emeritus ofsaid to have started in the early Pliocene（Ishiwada

London University for his helpful advice on several

et al., 1977）.

subjects and his assistance in correcting our English

4. Conclusion

manuscript.

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77

Global Sea Level in the Messinian Stage

中新世最末期（Messinian 期）の地中海，および世界における − 2000 m 海水準について
花田正明

深 海 掘 削 計 画 の Leg 13 航 海 が 地 中 海 海 域 で 実 施 さ れ た． こ の 深 海 掘 削 の 結 果， 地 中 海 の 深 海 底 か ら
Messiniann 期の蒸発岩が発見されたことが，世界中の注目を集めた．そして，当時の乗船科学者たちは，この蒸発岩の成因について，地中海だけに起こった現在の海水準にくらべて 2000 m におよぶ海水準低下現象であった，と結論した（Hsü et al., 1977）．すなわち，地中海においてのみ Messiniann 期の海水準は現在とくらべて，
2000 m 低かったことを強調している．
筆者は，DSDP, IPOD, ODP による深海掘削結果のイニシャルレポートを通覧して，地質時代の海水準の上昇について検討した．イニシャルレポートで，現地で形成されたと考えられる記載がされている浅海層の分布から，中新世最末期の古海水準は現在とくらべて約 2000 m 低い位置にあったと結論づけた（Hanada, 2000）．それは，Messinian 期の低海水準は，地中海だけではなかったということである．
このことを示す証拠の 1 つが，DSDP Leg13 航海中におこなわれた 2 つの掘削地点の深海掘削の結果に示されている．ひとつは，ジブラルタル海峡をはさんだ大西洋側の site 120 であり，他のひとつは地中海で実施されたsite 121 の掘削結果である．Site 120 は，ジブラルタル海峡の西北西，約 260 マイルの大西洋に存在する，最浅部の水深が 50 m ほどのゴリンゲ・バンクの北側斜面上で掘削がおこなわれた．掘削記録からは，本掘削地点では，鮮新世以降の深海化が明らかである．すなわち，site 120 は，水深 1711 m であり，海底下 55 m 付近に下部
鮮新統が発見されている．これと同様の深海化が地中海の Western Alboran Basin において実施された site 121の掘削記録にも見られる．すなわち，地中海の Messinian 期の蒸発岩の上に不整合に重なる Trubian の地層は，それにふくまれている底生有孔虫と介形虫の分析によって，深海相であるといわれている．したがって，この時点においては，地中海は大西洋から孤立した状態にはなかったことが明らかである．
このように，海成層において，中新統の上に重なる下部鮮新統が深海相を示すという例は，地中海だけのこと
でなく地中海以外の地域でも知られている．たとえば，北アメリカ大陸西岸のロサンゼルス堆積盆地では，下部
鮮新統中にふくまれる有孔虫，軟体動物，ウニなどの化石の分析によって，下部鮮新統が深海相を示すことがいわれている（Conery, 1967）．さらに，日本海においては，日本海の深海化は鮮新世初期にはじまったといわれている（石和田ほか，1977）．また，筆者は，地形計測の結果と地質構造からみて，日本近海の上部大陸斜面の発達
は，陸上の環境で形成された斜面が，その後に起こった海面上昇によって現在の海底に沈水したものであることを明らかにした（花田，1989）．
以上のようなことから，現在の海水準にくらべて，中新世最末期の海水準は 2000 m 低い位置にあったのは地中海だけの現象ではなく，汎世界的なものであり，このことは，生物地理学的な考察からも裏づけられている（Hoshino, 1998）（花田：東海大学海洋学部〒 424-8610

静岡県静岡市清水区折戸 3-20-1）