RIVER AND SOILS CYCLICITIES INTERFERING W ITH SEA LEVEL CHANGES
ROLAND PA E PE & ELFI VAN O V E R L O O P
Vrije U niversität Brussel (VUB)
Earth Technology Institute (ETI)
& Belgian Geological Survey
ABSTRACT: Palaeosoils and river deposits alternate at specific levels within continental
lithostratigraphic sequences of various parts of the globe. They attest to cyclicities through time
of global importance. This study is divided into a number of chapters especially regarding the last
2,4 Ma years, the last 130K-years and the last 10K-years, which may all be read almost independently
from the others. Without some lengthy chapters about the long term, middle term, and short term
geosoil cycles it was quite impossible to come to any reasonable conclusion about the number of
soils occurring in the Quaternary and the time stability of the geosoils in such sequences, especially
of the 100K interglacial soil. Four main groups of cycles of periodicities have been detected. Two
long range cycles, of 100K and 400K respectively, dominate the interglacial/glacial soil sequences
of the Quaternary. These reveal the continental evidence of Imbrie's 100K cycle and Hays' 400K
cycle. It is quite remarkable that the recorded soils in these continental systems all are relict soils
of interglacial age. In the coastal fringe area these soil sequences may interfere periodically with
interglacial marine deposits as well. From the North Sea and Mediterranean regions all palaeosoil
development can be proved to have occurred after, or towards the end of each of the marine
transgressions.
Another question was whether these marine transgressions result from climatic forcing. The
decreasing amplitude of the interglacial marine high level stands and glacial low stand fluctuations
towards the Holocene MSL (Mean Sea Level) infer that major regression/transgression cycles are
tectonically biased movements rather than climatically controlled ones.
The next two periodicity cycles are the middle range last 100K cycle (the Upper Pleistocene
or Last Glacial) and the short range 10K cycle (the Holocene). Within the last 100K a complete
warm/cold cycle was achieved. During this period one interglacial (warm climatic) soil has developed
at the beginning of the cycle, although after the maximum of the marine transgression. During
the following cold part of the cycle at least ten other interstadial (colder climatic) soils may have
developed. Fluctuations o f sea level within this cycle seem mainly related to climatic changes.
Finally the 10K cycle of the Holocene shows rapid fluctuations of the 40 m sea level rise during
the interglacial after the maximum soil development. Before this maximum soil development some
10,000 years ago, sea level had already been rising for more than 60 m since the maximum cold
of 18,000 BP.
253
R . P a e p e e t a l. (e d s .), G r e e n h o u s e E ffe c t, S e a L e v e l a n d D ro u g h t, 2 5 3 - 2 8 0 .
© 1 9 9 0 K lu w e r A c a d e m ic P u b lis h e r s . P r in te d in th e N e th e r la n d s .
The present mean sea level (MSL) should naturally have attained its equilibrium as a result,
first, of the long term tectonic rheology cycles of lithosphere, second, of the shorter climatic cycles.
Geotraverses from the North Sea Basin towards the Mediterranean into the equatorial Belt proved
that the tectonic cycles were of global intensity and frequency whereas the cl imatic cycles are increasing
in both frequency and intensity towards the Equator.
1.
Introduction: Deep Sea Versus Land D a ta
The validity o f standard sequences obtained fro m terrestrial deposits is still questionable,
especially for those who prefer to w ork with th e deep sea core results as standard scale.
Terrestrial sequences are believed to be:
- composed o f non-continuous sections
- incom plete because o f sedim ento-stratigraphic hiatuses
- of high variability as to sedimentation rates
- w ithout stable m arker horizons
- o f no global response (i.e. with no clim atic signal in the equatorial belt)
Deep sea records are considered to represent:
- continuous stratigraphie sections
- continuity in sedimentation
- generally uniform sedimentation rates
- stable m arker horizons with m icrofossils
- a global response from the Poles to the E q u ato r
M oreover, land data represent restricted dating possibilities:
- long-term palaeom agnetic dating as B/M , M /G boundaries
- occasional K /A r dating on basalt and tuff
- radiocarbon dating for m iddle and short te rm s
- unstable T L datings
- prehistoric and archaeological dating
In evaluating these statements, especially with regard to sedimentological-stratigraphical
continuity (which is an absolute necessity for establishing curves about clim atic changes
on a global scale) the following remarks may b e put forward.
For the deep sea record:
- the B/M (Brunhes/M atuyam a) Boundary o ccu rs sometimes in a cold stage (Shackleton
& Opdyke, 1973), sometimes in a warm p h a se (Imbrie, 1979).
- the rate o f bioturbation is high.
- only global changes in ice-volume are recorded without specifying which particular glacier
ice is dealt w ith and w ithout any evidence o f changes in other landm ark features as e.g.
forest cover density.
F o r the terrestrial record :
- continuity o f palaeosoil sequences in w indborne deposits as eolian loess is generally
accepted; this statem ent, how ever, is applicable to other depositional series in between
soils as e.g. loess.
- landm arks as palaeosoils are within limits o f variance and o f tim e transgressivity of
255
geographical spreading o f palaeosoils, synchronous fro m one geographical area to another
as well as with the deep sea oxygen-isotope record (see section 2)
- there is a firm possibility of a step by step correlation between sequences o f widely varying
geomorphological entities such as basin sequences, terrace sequences and plateau sequences.
2.
Palaeosoils as Stable Stratigraphical Key H orizons
As in all other geological sections, stable tim e bound k e y horizons are needed to establish
the tim escale o f a given geological sequence. Indeed, i f absolute dating materials are not
available, one is to produce relative dating methods such as the relative age determination
o f palaeosoils. Dating o f soils is useful as long as th e soil signals used for this purpose
show a certain degree o f stability o f occurrence in the stratigraphie record i.e. they should
occur a t definite time levels within reasonable small boundary intervals o f time.
Palaeosoils in the geologic sequence offer the possibility o f such stratigraphie stability.
H ow ever, the geological status of palaeosoils o f the Pleistocene and of the H olocene Series
rem ains controversial, especially am ongst geologists and pedologists. Indeed, unlike guide
fossils showing a definite taxonom y, palaeosoils most often do not. Actually, a large range
of fossil soils appear as monolayered, truncated soil horizons and hamper soil solum studies.
Others show multicyclic (polycyclic) soil horizons and also appear as single sediment layers
instead o f a well developed soil solum o r even a soil catena. Palaeosoils may not even
find their equivalent in the global soil zonation and m ay reflect environm ental climatic
conditions o f the Past which do not longer exist today.
These peculiarities all render the study o f soil dynam ics and soil genetics precarious or
even impossible when dealing with palaeosoils. But then the question arises whether a complete
soil solum is mandatory for the purpose o f dating a soil as a stratigraphie key horizon.
Since palaeosoils show continuous sequences from o ne area to another, this sim ple fact
may already indicate that palaeosoils are tim e bound and stable tim e stratigraphical units.
Nevertheless, despite their tim e stability, fossil soils rem ain difficult to date; they are
seldom built up by autochthonous parent-m aterial unless they are o f an organic (like peat
and hum ic horizons) or chemical (like calcrete horizons) origin. M ore often, as fossil soils
(like m odern soils) are developed in foreign parent m aterial different in age and origin
from the soil, the time relationship between the palaeosoil and the sediment remains dubious.
If hum ic o r calcrete horizons are suitable for im m ediate dating or environm ental assessment
(e.g. by pollen analysis o r stable isotope geochem istry), most other fossil soil horizons
are not since they mostly reflect only m ineralogical w eathering in nature.
Yet, palaeosoils exist and occupy specific tim e stable stratigraphie positions in sediment
sequences; m oreover, they may be follow ed from one sedim entary series into another,
thus serving as marker beds or key horizons in distant geographical belts. Hence, palaeosoils
are form al M em bers o f a "norm al" stratigraphie sequence and as such, are very useful
geologic tim e indicators as well as good indicators for assessm ent o f the environment.
Although the term "palaeosoils" is com m only used, palaeosoils as mem bers of a
lithostratigraphic sequence should be sim ply considered and named "geosoils" in the sense
256
5. P alaeo p ed o lo g y
^
4.
P alaeo b o tan y
3.
P alaeo clim ato lo g y
2.
P a laeo g eo m o rp h o lo g y
1.
P a la e o se d im e n ta tio n
fl m u l t i p h a s e o f s e d i m e n t a t i o n : f i r s t o r o a n i c j s e c o n d m i n e r a l & s o i l s o l u m
5.
P alaeo p ed o lo g y
4.
P a laeo b o tan y
3.
P alaeo clim ato lo g y
2.
P alaeo g eo m o rp h o lo g y
1.
P a la e o s e d im e n ta tio n
--- ------
/•
D u r i n g p h a s e B a l l s o i l b u i l d i n g p r o c e s s e s w e r e r e p e a t e d e n d i n g u p in a
1..............
n P in < m l I n g p r n h n n p th p . n rp .n in iis _ n n p ..
5.
P alaeo p ed o lo g y
4.
P alaeo b o tan y
3.
P alaeo clim ato lo g y
2. P alaeo g eo m o rp h o lo g y
1. P a la e o s e d im e n ta tio n
T h e s o i l b u i l d i n g p h a s e fl h a s t e r m i n a t e d a f t e r s u b s e q u e n t p h a s e s o f s e d i ­
m e n t a t i o n (1), s u r f a c e d e u e l o p m e n t ( 2 ) , c h a n g e o f c l i m a t i c c o n d i t i o n s (3),
d e u e l o p m e n t o f a neti> u e g e t a t i o n c o u e r ( 4 ) a n d f i n a l l y p e d o g e n e s i s ( 5 )
Figure 1. The five moments in the landscape building process.
257
given by M orrison (1965). This restricts the occurrence o f a palaeosoil level to its strictly
geological and geom orphological expression w ithout a n y other further bias to pedology.
From this point o f view five important steps or moments may be ascribed to fossil geosoils
occurring in a lithostratigraphic sequence (Fig. 1):
1 the palaeosedim entation m om ent which is the phase o f building up the parent material
which may vary from sedimentary and m etam orphic to volcanic and plutonic deposits.
2 the palaeogeomorphological moment o f shaping land surfaces corresponding to specific
processes o f landscape developm ent o f the past prior to the pedological m om ent or even
synchronous with it.
3 the palaeoclim atic moment: aside from the foregoing clim atic phases including
sedimentation and landscape development, one o r m o re clim atic phases may enhance
weathering (eventually involving all o r som e o f the aforem entioned moments o f the Past)
which previously was impossible.
4 the palaeobotanical moment: one o r m ore sequences o f vegetational developm ent of
the past following the previous moment o f initial w eathering.
5 the palaeopedological moment: a fossil soil (buried o r relict; with m odem equivalent
or not) inferring a m om ent o f standstill in the sedim entological aggradational process
of the Past.
It is quite clear that geosoils, combining all these natural mom ents, should no longer be
considered as occasionally occurring features but instead as stable horizons in both time
of occurrence and periodicity. Furtherm ore, all five m om ents point to clim atic changes
as the com m on generator o f the global forcing involved; henceforth, geosoils are true stable
clim atic indicators as w ell, operating at given periods o f time. Global clim atic changes
in terrestrial sequences may consequently be detected from the soil stratigraphie sequences
with the sam e degree o f accuracy and resolution as from deep sea sequences.
3.
T he 100K , 200K & 400K Periodicities Along th e N orth-South Geotraverse
3.1. T H E SO IL SEQU EN CES
The tim e stability and periodicities o f geosoil levels becom e clear when com paring soil
stratigraphie sequences from various global belts. At first sight such comparison may look
too sim ple from the m ethodological point o f view. B iohorizons as Stylatractus universus
occurring at isotope stage boundary 11/12 in the deep sea records are com pared over long
distances as well, because o f their tim e stability. For the same reasons, geosoils giving
proof o f such tim e stability may then be com pared over long distances as well in an attempt
to establish global continental lithostratigraphic correlation.
The N orth-South G eotraverse from the N orth Sea Basin (Belgium, 5 0 °N .) through the
Eastern Mediterranean (Greece, 36°N .) towards the Equator (Burundi, 4°S.) is a first attempt
to put such long distance correlation into focus. It reveals rem arkable evidence o f geosoil
stability (F ig .2). F o r the last 800,000 years (M iddle and U pper Pleistocene encompassing
the Brunhes polarity zone) eight geosoils o f the interglacial type regularly appear at lOOKy
258
K -years
BURUNDI
C H NA
BELGIUM
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(UPPER)
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ARENDONK PE A T
Figure 2. N orth-South Geotraverse: N orth S e a belt - Equatorial belt.
259
time intervals in the stratigraphie column o f the N orth S ea Belt. T he soil levels interfere
with colder and dryer periods o f loess or similar w indbom e deposits together with periglacial
features such as frostwedges (indicated by a V-shaped sym bol). Q uite often the interglacial
soil may be underlaid with a m arine deposit o f the sa m e interglacial age. From before
800Ky to about 2.2 M a years ago, another 13 soils o c c u r at regular 100K distances.
As most o f the sections are in loess o r loesslike deposits correlation o f the W esternmost
geotraverse with the Eastern loess section at Luochuan in China (36°S.) was inevitable
and rem ains by and large perfectly feasible. The stability o f the loess-geosoil sequences
o f China reinforce the principle o f both geosoil stability and the possibility o f long distance
lithostratigraphic correlation.
3 .1 .1 . Geosoils o f the L ast 800K-Years. In all o f the sequences considered, geosoils are
best developed within the time interval between 800,000 and 450,000 years with a maximum
developm ent at the Eastern level o f geosoil S5 at L uochuan and at the corresponding
pedocomplex PK5 o f the W estern levels. This time interval corresponds to the classical
Cromerian Complex o f Zagwijn (1975) with four distinctive interglacials and corresponding
interglacial geosoils (Paepe, 1975). They are corresponding with the Dram a Complex of
G reece (Paepe et a l., 1986) and with the m iddle p a rt o f the Bwegera Form ation in
Burundi/Zaire (Ilunga Lutum ba, 1984).
The interglacial geosoils o f the next 400K -years are less well developed in all o f the
geologic sequences considered and show a num ber o f hiatuses in the soil sequence. This
tim e interval corresponds with the com plicated glacio-lithostratigraphic subdivisions of
N orthern Europe, i.e ., the Elst, the H olsteinian, the D renthe, the W acken, the Saale,
the Treene, the W arthe, the Eem ian and the W eichselian Stages (the bold ones being the
interglacials). The sequence is indisputably the m ost com plete again in Luochuan and in
Burundi/Zaire i.e. in the Tropics and Subtropics.
The less well developed nature o f the last 400K series o f geosoils led to the assumption
that the clim ate was generally cooler and dry er than during the previous 400K period. It
also leads to the recognition o f long-term w arm periods (Therm om ers, T) with generally
w arm er interglacials and long-term cooler/dryer periods (Cryom ers, C) with generally
cooler interglacials. This 400K -years cyclicity (Paepe et a l., 1986) is sim ilar to what was
shown by HAYS et a l.in 1981 for the 400 K periodicity from the deep sea core studies.
Thus may be concluded that for the last 800,000 years geosoils on a global scale from
North to South and from East to W est, reveal two im bricated long terrestrial cyclicities:
a 100K-years periodicity composed o f eight w arm (interglacial)/cold (glacial) cycles which
can be split up into two 400K -years periodicities: one initial w arm er cycle starting at about
800K and a generally cooler one starting at about 400K and including the very last warm/cold
cycle o f the U pper Pleistocene (starting som e 127K-years ago). A new Therm om er has
just started some 10K-years ago with the beginning o f the M odem Stage or H olocene of
which the N eolithic M arathon soil is the first expression (see hereafter). T oday1s worldwide
recognised so-called greenhouse effect is trapped within this new long-term generally warmer
natural phase.
260
3 .1 .2 . Geosoils o f the 800K /2.4 M a Time Span. Beyond the 800,000 years boundary in
the Lower Pleistocene Subseries correlation becom es less obvious. In E urope, cold cryomer
conditions prevailed hampering the regular developm ent o f geosoils over a tim e o f another
400K-years which started som e 1.2 M a years a g o . It is the original cold M enapian Stage
which recently has been subdivided into a M enapian Substage and a Bavelian Stage (Zagwijn,
1987) in which two w arm er Substages occur nam ely the Bavel and the Leerdam Substages.
Only a few calcrete soil horizons are developed in Belgium and in G reece at this level
whereas soils o f the same stratigraphie position double or even triple in num ber in the
Loess Belt o f China and in the Equatorial B elt o f A frica (B urundi/Zaire). Indeed, over
less than 400,000 years at least six, sometimes seven geosoils occur. The im m ediate effect
is that correlation in the Low er Pleistocene S ubseries o f tropical and monsoonal regimes
is not hampered by a lack o f evidence but by a n abundance o f evidence throughout the
same time span.
This geosoil doubling effect in tropical and subtropical belts reaches its maximum with
again at least six new geosoils in the next tim e interval located roughly betw een 1.2 and
1.5 M illion years. It corresponds to the well know n therm om er encom passing the W aalian
Stage in the N orth Sea Belt stratigraphie classification. Usually four well developed organic
geosoils characterised by the arrival o f the fern A zolla filiculoides in the pollen spectrum
occur. The sam e occurs in G reece in the so called Kokkino (Limanaki) Form ation and
in Burundi/Zaire in the so-called Cibitoke F orm ation (upper part).
Similarly one finds during the next C ryom er (referred to as the Eburonian Stage in the
North sea Belt) organic peat bogs o f the tundra which developed during the interglacial
phases o fth a t Super Stage. In the Eastern M editerranean only a few calcrete horizons occur
within the equivalent Spata Stage, and an even m uch weaker developm ent is observed in
the Equatorial Belt (Burundi/Zaire) and not a t all in the monsoonal region o f the Loess
Plateau (Xian Province) in China.
T he next warm therm om er tallies with the fam ous Tiglian Stage o f the N orth Sea Belt
with Azolla tigliensis. It shows still m ore geosoil development in the monsoonal (China
loess) belt with at least four well developed ones within the Wusheng Loess 3 (WS 3) covering
the tim e interval o f 1.8 to 2 .2 million years. L ess developed are the equivalent soils in
the M eltemi Stage o f G reece and in the M uhira Formation o f B urundi/Zaire.
3.1.3. The Red Silt Soil. Except for the North S ea Belt a well developed Red Silt Soil (of
the Latosoil type) form s the low erm ost soil in China, Greece and Burundi. There is no
equivalent o f such soil within the above lying Pleistocene geosoils series. That is why
investigators in the various regions considered this Red Silt Soil originally to represent
the N eogene/Pleistocene Boundary. H ow ever, in Greece Paepe, Hus and Lin (in press)
found in 1981 at the type locality o f Kokkino Limanaki that the Red Silt Soil was older
than the Olduvai Event (palaeomagnetic evidence) and younger than the first cold oscillation
o f the Quaternary (foram iniferal evidence). B elow that soil, lagoonal m arls with periglacial
features occur in turn overlying a Pecten Crag which has been definitely proved to be o f
U pper Pliocene A ge (Christodoulou, 1969). T h e real End-Tertiary soil occurs immediately
underneath.
261
A t Luochuan, a sim ilar situation occurs w here the M atuyam a/G auss Boundary of 2.43
Ma was found to exist immediately under the Red Silt Soil whereas below the palaeomagnetic
boundary other well developed latosols occur. These m ay be correlated with the Pliocene
A rendonk Peat M em ber o f Belgium occurring in the L a te Pliocene N orth Sea Belt (Paepe
& Van H oom e, 1976).
Three basic questions arise from the evidence as given. T hese are:
1 W hy is the beginning o f the Quaternary characterised b y a soil reflecting vegetational,
clim atical and geom orphological conditions o f the T ertiary even after the first severe
cold phase took place already during the first C ry o m er dating from the beginning of
the Pleistocene and lasting from roughly 2 .4 to 2 .0 m illion years?
2 W hy did none o f these traditionally Tertiary-bound conditions of soil development re-appear
after that period so that subsequent typical Q uaternary soil developm ent becomes totally
different and generally o f lesser developm ent?
3 W hy is this the first soil o f the first Q uaternary Therm om er encompassing the
Tiglian/M eltem i Stage and not a separate one?
T he conclusion o f this chapter deals essentially with th e stratigraphical significance of the
100K and 400K cyclicities.
(a) It is rem arkable that geosoils (i.e. land surfaces and relevant vegetations) of the
interglacial stages can be found to be piled up one upon another w ithout interruption
by sedim entary sequences revealing the presence o f interstadial soils. These sequences
show the prerequisite position for the interglacial soil landscape development. It is
a specific geom orphological position which m ost probably coincides with a plateau
type feature. N o evidence o f any interstadial soil developm ent nor of related glacial
lithostratigraphic sequences is shown between such positions. I f such intermediate
sediments have ever existed, they have either been eroded away or have been preserved
only in specific relict type positions (see section 4).
This geom orphological param eter o f the interglacial soil landscape adds to the time stability
o f the interglacial geosoil. It may be concluded that the 100K and related 400K long term
Geosoil Lithostratigraphic Cycles show over the last 2 .5 M illion years an uninterrupted
interglacial landscape sequence o f extensive, widely developed landm arks o f sim ilar nature.
In these features the geom orphological link with the past interglacial landscape shows
m axim um preservation. It therefore becom es possible to use these geosoils for global
correlation and for the land locking o f the Brunhes/M atuyam a and M atyam a/G auss polarity
reversals.
(b) A ccording to the higher resolution o f geosoil frequency in the tropics than in higher
latitudinal regions it may be questioned w hether Glacial Periods resulted from
disturbances in the Global Circulation System (GCS) in the Pole areas or in Equatorial
zones which seem to have responded m ore rapidly and more frequently to GCS changes.
262
3 . 2 . THE RELATIONSHIP BETWEEN 100K, 20 0 K & 400K GEOSOILS AND SEA LEVEL CHANGES
O ne o f the first relations established by early geom orphologists was the principle that all
geom orphological evolution was intim ately related to a base level o f erosion. As oceans
occupy 4/5 o f the global surface, the Mean Sea Level (M SL) represents the most important
base level o f erosion and hence o f landscape m odelling.
I f the previously discussed interglacial soil-landscape sequences have been developed
on privileged geomorphological positions as plateau-surfaces, the areas around these
"interfluvial" regions were subject to frequent cyclic rem odelling as a result o f the sea
level changes. T he land-/seascape dynam ic ratio continuously changed between two standextrem es of low and high sea level, i.e. in the m o st geo-dynam ic part of the global surface:
betw een the isolated plateau's on the one side an d the deep sea beyond the continental shelf,
on the other.
M oreover, within the narrow marginal zone o f changing coastlines attesting to the highest
and the lowest stands o f the M SL, m arine and continental deposits rapidly alternate. Such
m arginal sedimentation areas w ere studied intensively in the periphery o f the Southern
Bight o f the North Sea Basin, on the East coast o f Attica (Greece) for the Aegean Sea (Eastern
M editerranean) and for Lake Tanganyika in th e Ruzizi Plain (Zaire-Burundi) as described
above.
T he land-sea relationship for the Southern B ig ht of the N orth Sea was studied from the
interglacial geosoil position in betw een the m arine transgressive deposits. The Lower
Pleistocene sequence was studied along the D utch-Belgian border (Paepe & Vanhoorne,
1978), the Middle Pleistocene sequence along th e French-Belgian border (Sommé & Paepe,
1981) and the U pper Pleistocene along the F lem ish Valley (Tavernier, 1943; Paepe & Van
Eloorne, 1968), the southernmost fossil estuary on Belgian territory of the D elta system
in the Southern Netherlands.
3.2.1. Sea Level Changes during the Last 800K- Years. The span-interval of the last 800K-years
(U pper- and M iddle Pleistocene combined) show s the best correlation (Fig. 3). Along the
Flem ish Valley from M elle (Ghent) tow ards th e N orth Sea (Zeebrugge) M SL fluctuations
w ithin the tim e span o f 800 Ky to 400 Ky w ere recorded. At M elle two m arine highstands
respectively at + 5 m and + 1 2 m above M S L w ere recorded with overlying continental
peat horizons as belonging to the beginning o f the Cromerian Complex (Paepe, 1974).
These initial high M SL stands (occurring after undetermined lower stands during the preceding
cold dry Bavelian Stage) coincide with isotope stage peaks 19 and 17 which are separated
by a double peaked isotopic trough corresponding to a low MSL stand at -15 m approximately.
A nother much deeper isotopic trough occurs ju s t before isotope stage 15 most probably
coinciding with a yet undeterm ined m ajor low M SL stand o f presum ably -50 m right in
the M iddle o f the Cromerian Stage. T he last mentioned stage 15 again is composed of
two high isotope peaks corresponding with two high stands of M SL in the Zeebrugge Member
(Paepe et a l., 1981). Flowever, at a considerably lower level than those occurring at the
beginning o f the Cromerian C om plex, respectively at -10 m and -25 m MSL.
From this first analysis o f the first 400K -years of the M iddle Pleistocene (totally
263
SEA LEVEL CHANGES
DURING TH E LAST 8 0 0 .0 0 0 YEARS
IN T H E SOUTHERN BIGHT O F T H E NORTH SEA
[ France. Belgium and th e S outhern Netherlands J
U pper
P leist.
H olo
cene
Midd le
Therm om er
P l e i s t o c e n e
Cryomer
L ow er PI.
T herm om er
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Fig. 3 : The F lem ish Valley in th e north o f B elgium is th e southern­
m o st o u tlet o f th e Zealand Schelde, Maas and Rhine estuary which
filled up co m p letely during th e last 8 0 0 .0 0 0 years. Peaks and lows
o f th e oxygen isotop e curve correlate w ith th e high and low inter­
glacial MSL stands. As so ils occur on top o f th e m arine d ep osits
th e y are ind icatin g th e en d phase o f th e interglacial after th e
m axim um transgression o f th e sea.
264
corresponding to the Crom erian Complex Stage) four high stands o f M SL are recorded
of which the two earlier ones (Melle) are g enerally 20-50 m higher than the two later ones
(Zeebrugge). It also means that the earlier ones a re above to d a y 's M SL and the later ones
below. Between the earlier and later Crom erian transgressions the deep stand (at least -50
m) o f which no evidence is found except for th e deep valleys incised in som e parts of the
Flem ish Valley (De M oor;Paepe, 1963).
Each o f the high stands is succeeded by an o rg a n ic soil layer totalling four geosoil levels
dating o f the Crom erian Complex Stage. E q u ally, along the terraces o f the Lesse (more
specifically at Han-sur-Lesse) four truncated tex tural B-soil horizons also occur in the same
tim e span o f the Crom erian Complex Stage and w ere indicated as Han Soils (Paepe, ).
These soils by correlation with the Eemian and H olocene situation (see p.) are considered
as post-marine. This conclusion corresponds with the opinions o f Iversen (1958) and Grycuk
(1965) proclaim ing a generally drier climate to w ards the end o f an interglacial, with little
if any sedim entation and soil development (L ozek, 1975) during this depositional standstill.
A t H erzeele (French-Belgian border) isotope stages 13 and 11 correspond with two peaks
o f m arine highstands respectively occurring b e fo re Holsteinian Stage peat layers H o i and
Ho2 (Sommé;Paepe et al., 1978; Van Hoome & Geysels, 1987). These Herzeele highstands,
with an average o f + 1 5 m M SL correspond w ith the M elle highstands.
D uring isotope stage 9 the next highstand reaches only -25 m M SL whereas during the
next isotope stage 7 it occurs around + 1 5 m M S L . These highstands have been observed
at Izenberge (Belgium) not far from Herzeele (F rance) along both sides of the famous river
of the Great W ar, the Yzer. Once again, p e a tb o g s occur above the m arine layers indicating
that the end o f each transgression was follow ed by a slightly dryer period inducing land
aggradation with soil developm ent (corresponding with the T ubize and Daussoulx Soils
on the continent). The Izenberge high type transgression continues within the Ostend highstand
at + 5 m M SL (isotope stage 5) seconded by a lo w type transgression at -25 m M SL (isotope
stage 3) during the U pper Pleistocene namely th e Denekamp Interstadial (see section 4).
Each o f these transgressions is followed again by soil forming processes as the Rocourt
Soil (Gullentops, 1954; Paepe, 1963) and the Z elzate Soil (Paepe, 1964) at 110 Ky and
30 Ky respectively. The M SL o f the H olocene F landrian Transgression occupies the lowest
position o f all form er highstands. Actually a gen eral lowering o f the highstand MSL from
an average o f + 2 0 m M SL some 800 Ky ago to w ards today's zero M SL may be observed.
Absolute low stands seem to have diminished a s well so that one may speak o f a general
am plitude decrease in the course o f the last 8 0 0 Ky.
3 .2 .2 . The L ast 2 .4 Ma. Time Span. If one extends the above m entioned observations to
the end o f the Pre-Tiglian Stage i.e. at about 2 M a (Fig. 4), the am plitude of high and
low M SL stands is increasing from about 50 m for the end o f the M iddle Pleistocene to
about 100 m for the beginning o f the Lower Pleistocene.
T he frequency o f occurrence o f high and lo w M SL stands varies as well throughout .
the Q uaternary. A t first inspection peaks o f sea level highstands are less compatible with
isotope stage peaks and one single peak seems to cover two or even a group o f corresponding
isotope peaks. F o r exam ple the M SL highstand at + 3 5 m. o f the Tiglian Stage located
265
at about 1.7 Ma occurred in the m iddle o f the O lduvai polarity event. The latter range
is com posed o f at least two, perhaps three isotope peaks each o f which may correspond
with the sole M SL highstand. The deeper isotope tro ughs occurring before the beginning
(1.77 M a) and at the end (1.57 M a) o f the Olduvai event coincide with two low M SL stands
at -75 m and -50 m respectively. T he w hole covers a tim e o f alm ost 200K-years.
T he next 200K-years climb up in tim e to about 1.37 M a encompassing on the isotope
curve a series o f five weakly developed peaks o f a w eaker intensity than all previous ones.
O nly the troughs at the beginning and at the end o f this 2 0 0 K-years tim e span are naturally
reflected into two low M SL stands at -50 m. and -65 m respectively. In between, two high
level stands occurring at about -15 m each may possibly correspond with the group of
interm ediate isotope peaks. Even when based on this m inim um assumption these highstands
occur alm ost at a position 50 m low er than the Olduvai - Tiglian M SL highstand at + 35
m. A ccording to the classical Southern N orth Sea C hronostratigraphic Classification this
period encompasses a greater part o f the cold Eburonian Stage within the second Cryom er
o f the L ow er Pleistocene.
T he following 200 K-years lasting to about 1.1 M a show a succession o f four MSL
highstands at only + 1 0 m and shallow M SL low stands at -10 m between two major troughs:
the aforem entioned at -60 m and a new deep low stand at -30 m. Except for the first one,
it is difficult to make any correlation with the peaks and troughs o f the isotope curve in
this reach. Nevertheless, these higher highstands in com parison to the previous series point
to a possible correlation with the W aalian Stage m arine transgressions.
From the -30 m. level on, a steady rise o f the sea level can be followed so that this latter
lowstand may well encompass the M enapian Cold Stage as recently redefined by Zagwijn
& D e Jong (1988). In the same line o f thought the next tw o M SL highstands at respectively
+ 5 m and + 2 5 m, ju st before the deep trough on the oxygen-isotope curve, are correlated
with the Bavel and Leerdam interglacials o f the D utch Bavelian Stage. The deep trough
represents the extrem e cold phase separating the L ow er from the M iddle Pleistocene viz.
the Bavelian Stage from the general w arm er C rom erian Com plex Stage. As stated before,
the landscape evidence o f the deep isotopic trough may be represented by the deep gullies
eroded at the base o f the Flem ish Valley (Paepe, 1981) and the steady retreat to the North
o f H olland o f the estuaries o f the R hine and M euse rivers (Zagw ijn, 1975; Paepe, 1981).
Despite these assumptions o f a correlation between the lithostratigraphic and chronostratigra­
phic subdivisions o f the North Sea which form erly was assumed to be one o f the most
com plete o f quaternary classifications, it becom es clear that such a subdivision today is
far from com plete when com pared to the standard deep sea record and the geosoil record
o f the monsoonal subtropics and the tropics. The main reason for this incompatibility is
due to the fact that the (chronostratigraphic) N orth Sea Belt Stages absolutely did not
encompass oxygen-isotopic stages during the Lower Pleistocene. Indeed, the "continental/coast­
al fringe" classification o f the higher M iddle Latitudes does not show a sufficiently continuous
record to follow and detect all clim atic variations and it is not at all clear w hat the impact
o f the neotectonics at each o f these Stage levels is in that region. Therefore chronostratigraphic
"Stages" have erroneously grouped one o r m ore 100K-years intervals thus rendering
correlation extremely difficult if not im possible.
266
F L A N D E R S & C O A ST A L P L
& O FFSH O RE AREAS
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This figure shows the possible correlation between sea level high stands and
low stands during the last 2.4 Ma years of the Quaternary..
O
:
J
fS .
f
Fixed measured ordnance datum level of sea level highs and lows
:
•'
Asymptotic curve of high an d low MSL ( m ean sea level).
Periodicity graph of high and low MSL in comparison with the oxygenisotope curve of the last 2.4 Ma years.
Figure 4. Sea level changes o f the last 2 m illion years (southern bight o f the North Sea).
Even if one should be careful in making such correlations, it cannot be denied that a
num ber o f high and low M SL stands exist and a re seemingly following patterns o f climatic
changes within the limits o f neotectonic m ovem ents.
W hen the maximum and minim um stands o f Pleistocene sea level changes o f the two
above discussed graphs (F ig.4) are connected som ething quite striking is happening. For
the last 800 K-years, starting at present zero M SL , one not only finds the 200 K periodicity
but an asym ptotically increasing am plitude betw een the maximum and minimum levels
o f the coastline stands. In the present coastal plain area maximum am plitude differences
for the Last G lacial/H olocene figure about 25-30 m and at 800 K-years about 75 m. This
trend continues beyond the 800 K -year (i.e. th e Brunhes/M atuyam a boundary) with an
ever widening trend to about 130 m (alm ost doubling the 75 m amplitude) over slightly
267
more than another 800 K-years, at the beginning o f the Pleistocene. From this asymptotically
double dim m ing trend o f both maxima and minima a ro u n d the present M SL the question
arises whether this amplitude will reach zero in the near future. This very question withholds
further consideration about changes in M SL namely w h eth e r these are clim atically biased
or solely due to tectonic m ovements, including seafloor m ovem ents as well. Paepe (1963,
1981) has suggested the possibility of terrace building as periodically induced tectonic terrace
steps. Indeed, many o f the terrace systems developed around the Southern N orth Sea are,
clim atically speaking, polycyclic since they are com posed o f sediment series form ed under
widely differentiated clim ates (Paepe, 1981 ; Paulissen, 1977). This brings one to a further
consideration that if terraces, due to cyclic induced tecto n ic m ovements (enhancing high
and low M SL stands i.e. higher and low er base levels o f erosion) correlate with climatic
stages o f the deep sea record and (as was stated above) with clim atic soil phases, does
that not point to clim atic changes rather being a result o f sea floor m ovements than vice
versa? A t least it teaches us at this stage o f the investigation that sea level changes and
related landscape morphological evolution are not necessarily solely the result o f climatic
Global C hange alone.
4.
T he 40K and 20K Periodicities Along the N orth-South Geotraverse
In the previous chapter only 100K-years interglacial soil levels have been considered in
lithological sequences where little if any other deposits than such soils are present. In particular
situations som e others, especially periglacial and w indborne (e.g. loess) deposits, have
been preserved as relatively thin layers between the soils. In some particular conditions,
how ever, com plete w arm /cold sediment sequences m ay be found trapped in fossil valleys
or on broad plateaus. M ost o f these com plete sequences are dating mainly back to the Last
Interglacial/G lacial cycle (U pper/Late Pleistocene) although others may be found as well.
In such sequences interglacial palaeosoils occupy the low est position whereas in the layers
above them other fossil soils o f different nature occur. T h e latter usually are called "inter­
stadial" palaeosoils in contrast to the "stadial" sedim ents which reflect cold phases.
"Interstadials" are o f a m ilder clim ate than the vigorously cold glacial "stadials" but never
as mild as an interglacial. Interstadial geosoils are therefore of w eaker developm ent than
interglacial geosoils.
Many such Late Pleistocene sections have been described all over Europe over the last
thirty years; yet most o f them were located north o f th e Pyrenees and o f the Alps. Only
in the last five years sections o f Late Pleistocene A ge have been described from regions
south o f the European mountains in Italy, Spain and G reece. A jum p-over to the Equatorial
Belt was m ade possible thanks to mapping o f the Ruzizi plain in B urundi/Zaire by Ilunga
Lutum ba. In F ig .5 sections from Zelzate (Belgium) in the North Sea Belt (Paepe 1966),
from K oroni (Greece) in the Southern Peloponnesus (Paepe, M ariolakos & Van Overloop,
1981) and from G ihungw e (Burundi) in the W est A frican Rift (Ilunga Lutum ba, 1984)
have been selected to establish a Late Pleistocene N orth-South geotraverse. This middle
range geotraverse parallels the long range one with only interglacial soils represented. Again
268
the sections are projected against the Late P leisto cene oxygen isotope stages o f Shackleton
& O pdyke (1973).
T he Zelzate section has developed entirely a b o v e m arine layers o f the Last Interglacial
(Eem ian Stage). Im mediately above it is the so-called Rocourt Soil o f Eem ian Age. Since
its introduction by Gullentops (1954), this soil h a s been generally considered to form the
base o f the Late Pleistocene in the typical L oess Belt of W estern and Central Europe. In
the Zelzate section it was made clear by Paepe (1964) that this interglacial soil was developed
after the maximum o f the marine transgression o f th e same Last Interglacial which is generally
believed to correspond to isotope stage 5e. T he R o court Soil which in most o f the sections
north o f the A lps occurs as a single red soil tex tu ral horizon is proved to be polycyclic
thus form ing a com plex which developed at a different stage following isotope stage 5e
i.e. after 1 15K-years. Since the studies carried o u t at La G rande Pile (W oillard & Mook,
1982) confusion has risen as to the boundary betw een the Last Interglacial and Last Glacial
viz. whether the interglacial should be extended u ntil the upper lim it either o f isotope stage
5a o r 5e. This will be discussed at full length later in this paper.
A bove the R ocourt Soil another series o f s o il levels are found to which the names
Amersfoort (68K-years, Zagwijn, 1967), Brorup (65K-years, Andersen, 1965) and Odderade
(55K-years, Averdieck, 1968) were given. A s in many places the three soil layers are
telescoped together into one complex soil h o rizo n the nam e W arneton Soil Complex for
such a grouping was introduced by Paepe (1 9 6 3 ). The w hole series o f soils correspond
with weakly developed steppelike soils. Therefore they are considered interstadial. Henceforth
they encom pass isotope stage 4 ( dated 73K thro ugh 61 K-years) according to the former
datings and in o u r opinion these soil horizons should not be confused with any possible
soil developm ent o f an age older than 75K -years. In fact they are clearly separated from
the R ocourt Soil by important periglacial features (such as cryoturbations and frost wedges)
whereas im m ediately above them, large frost w edges usually occur along a line of strong
erosional unconform ity indicating a severe co ld phase of som e 50K-years ago.
In com paring the above discussed part of the Z elzate section with the sections in Koroni
and in Gihungwe the statements about the R o co urt and W arneton Soil Complexes gain
stronger evidence. Actually, in Koroni the equivalent o f the Rocourt Soil split up in three
red textural B horizons labelled as Koroni Soils o f which Koroni Soil 2 can still be subdivided
into two horizons. Between Koroni Soil 1 and the underlying Last Interglacial marine deposits,
frostlike wedges occur. Above Koroni Soil 3 follow s a series o f three w eaker developed
brow n soils in a sedim ent series which, as is the case in the Zelzate series, is again strongly
eroded at the top. Similarly in Gihungwe a threefold subdivision for the interglacial soils
and a threefold subdivision for the overlying interstadial soils is maintained.
Between 50K -years (first extrem e cold) and 26K -years (second extrem e cold) another
threefold system o f well dated interstadial soils develop at respectively the Poperinge/Moershoofd level (45K ), the Hoboken/H engelo level (34K) and finally at the Zelzate/Denekamp
level (29K) (Zagw ijn & Paepe, 1968). They rep resent mild phases o f the full glacial period
(isotope stage 3) so that their degree o f developm ent is weaker still than the previous
interstadial soils o f the W arneton Soil C om plex. The 45K and the 34K soil levels are quite
often lacking due to erosional activities going on at this stage of the Last Glacial (as is
269
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270
observed in K oroni). H ow ever, at Gihungwe in the Equatorial Belt one observes againa
doubling o f these interstadial soils.
After the maximum cold a t 18K-years, again three interstadial hum ic soil levels were
reported in the Zelzate section at about 17K (Z ulte/L ascaux level), 12K (Stabroek/Bolling
level) and at about 1 IK (Roksem /A llerod level) o f which the equivalents o f the uppermost
two are found in Koroni (this p art was not observed in G ihungwe). The w hole is covered
with the next interglacial soil o f the H olocene.
A few prelim inary conclusions may be draw n a t this stage (Fig. 6):
(a) The so called "Interglacial Soil" represents a fivefold com plex soil development o f
which part was form ed during warm p h ases corresponding w ith the end o f isotope
stage 5e, beginning, m iddle, and end o f iso to p e stage 5c, and finally o f isotope stage
5a.
(b) All soil developm ents are posterior to th e maximum o f the interglacial marine
transgression (Zelzate & Koroni) viz. th e maximum lake level rise (Gihungwe).
(c) Only the 5e soil development is considered to be fully representing the Last Interglacial
and indicated as an interglacial pedocom plex (PK) m arking the end o f the Last
Interglacial after either a m arine or lake transgression; certainly before the start of
the first cooling or drying o f the clim ate.
(d) Above the interglacial soil type form ations occur. From 75K-years ago three groups
o f three interstadial soils each, between 6 8 K and 55K-years, 45K and 28K-years, and
17K and 11 K-years respectively. These n in e interstadial soils together with the four
weaker interglacial soil types represent 13 Last Glacial Soils (GS).
(e) By controlling the tim e interval between a num ber of date limits as 73K against 95K
and 115K one may readily detect the 20K and 40K-years cyclicity which is proved
to be a result o f obliquity and equinox respectively (Berger, 1978).
(f) The position o f a interglacial soil is indisputably located at the very beginning o f each
warm/cold 100K cycle. M oreover, as it occurs between the maximum of the interglacial
transgressions (high M SL) and the first n e x t cold, it can only be a fraction o f 10,000
years considering the tim e span intervals o f both continental H olocene and 5e isotope
stage.
(g) Two other questions are arising from th e above considerations:
- Would an interglacial include the whole period of sea level rise starting immediately
after the maximum cold? If answered positively then the H olocene would be lasting
alm ost twice as long i.e . 20,000 years from 17K BP to the beginning o f the next
glacial period in the near future about 5000 A .D . Likew ise, the space of time o f
the Last Interglacial should be enlarged as has been done by som e American
Quaternarists by shifting the beginning o f the Last Interglacial to about 145K BP.
- Should not, in the light o f the above m entioned, the position o f the interglacial '
palaeosoil be determined with even greater precision? This question will be answered
in the following chapter on the study o f the palaeosoil cycle during the Holocene.
271
5.
Palaeosoil Cycles o f the Holocene
T he H olocene sequence o f geosoils within the duration o f the current interglacial, i.e. the
last 10,000 years, has been unravelled thanks to the geological-archaeological studies carried
out in G reece since 1975. In num erous excavation sections o f the A ttica peninsula namely
in the M arathon Plain, down along the East A ttica coastal plain to Cape Sounion and in
the Kifissos Valley in the Western part between Athens and Pireefs, at least twenty Holocene
Soils (HS) o f different soil types have been revealed. It points to a soil cyclicity of an average
o f one in every 500 years. As is shown in F ig .6 the frequency o f this continuous series
o f tw enty soils seems to amplify as they becom e m ore rec en t and w eaker in development.
This will be discussed in due detail hereafter.
A thens and its surroundings is indeed fam ous for its abundance in continuity o f vestiges
o f antiquity all over the past 7000 years viz. since the N eolithic Period. The relationship
between the occupation o f land by man and the natural landscape evolution may therefore
be studied in that area at the highest possible resolution. It was possible to establish
litho-stratotypes (F ig .6) i.e. complete lithological sequences o f the rock layers and o f the
soils in the famous battlefield o f Marathon (Holostratotype) and in the Kifissos Valley linking
Athens and Pireefs (Hypostratotype).
D eposits from the ancient river Haradros have build up a fossil alluvial fan in the middle
o f the M arathon Plain. In Fig. 6 the M arathon H olostratotype shows above the substratum
o f M esozoic shales a series o f sands, gravels, loam s and clays separated by geosoils. The
great num ber o f cherts in these deposits proved that one is dealing here with a complete
series o f H olocene deposits.
Indeed, above the shales one finds the first (HS1) and m ost developed strong red geosoil
which therefore has been specially labelled with the nam e M arathon Soil. This soil paves
the fossil valley which deepens towards the sea so that the assumption is then that the it
shapes the erosion valley which was formed during the sea level low stand of the previous
Last Glacial Stage. It points at an Early H olocene Age for its development.
T he sand covering the M arathon Soil is sealed o ff by another weakly developed soil
(HS2) upon which follows a thick series o f coarse well rounded gravels. The fluviatile
sands between HS 1 and HS2 testify to the fluviatile filling up of the valley due to the post
glacial sea level rise which hampered the evacuation o f the valley waters. As this very
first phase o f sea level rise cam e to an end the valley bottom was again overgrow n by
vegetation so that HS2 developed and sealed o ff the very first part o f the valley filling.
Early N eolithic rem ains and cherts found above these soil series confirm their Early
H olocene Age. Both are believed to be older than 8000 BP (Before Present), the start of
the N eolithic in G reece being located at about 6000 BC (Before C hrist). This period of
two thousand years corresponds in archaeological terms with the Mesolithic while in geological
term s it encom passes the relatively dry phases o f the Pre Boreal and the Boreal. T he high
degree o f developm ent o f the M arathon Soil (HS 1) inplicates deciduous forest conditions
which m ean high tem perature and a certain am ount o f m oisture higher than during the
dry P re Boreal. The m ost probable position for such clim atic conditions is the transition
o f the P re Boreal tow ards the Boreal about 9000 B P. The w eaker HS2 brow n soil developed
272
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273
in slightly sim ilar conditions 1000 years later at the en d o f the dry Boreal Substage when
climatic conditions w ere gradually transgressing into th e m oister A tlantic Substage. The
sharp contrast with the overlying thick coarse gravel b o d y indeed points to a definite change
towards a more energetic fluviatile activity inferring m oister climatic conditions; the thickness
o f the gravel body points to a strong rise in sea level w hich also occurred as a result of
the A tlantic Clim atic Optimum.
Above the gravel body, four geosoils HS3, HS4, H S 5 and H S6 occur at regular time
intervals o f roughly 500 years, covering the whole space o f time o f the Bronze Age. This
archaeological period encom passes roughly the tim e in terval o f 5000 BP to 3000 BP which
corresponds to 90% o f the new dry Sub-Boreal Substage. Fluviatile activity seriously decreased
and was periodically interrupted by even dryer phases thus offering the possibility for
vegetation to overgrow valley bottom s at each o f the d ry /w et transitions and for soils to
form.
Tow ards the end o f the Bronze Age and at the beginning o f the G eom etric Period about
1000 BC (some 3000 years ago) the postglacial valleys, basins and coastal plains were
completely filled in until today's topographical level and sealed off by a new strongly
developed geosoil H S6. As this soil level locates a very precise landm ark in the evolution
o f the land m achinery it is connoted again with a specific name: the Kallikleios Soil. For
the second tim e in the H olocene, soil development a t least points to an overwhelming
vegetation which in turn points to higher moisture conditions announcing clearly the dawning
of the m oister Sub-A tlantic Sub Stage. Conditions o f life must have changed dramatically
by both the com plete filling up and the bevelling o f th e landscape as well as by a the
trem endous growth o f the forest.
A fter 700 BC (some 2700 BP) these newly established lowlands offered less flooded
landscape conditions together with abundant woodland w hich allowed the highly developed
civilisations o f H istorical Tim es develop. N evertheless, periods o f reduced river activity
and partial reforestation occurred, the latter being the origin o f eight geosoils o f most different
soil types varying from brow n soils (H S7,H S 8,H S 9,H S 10,H S 11) to steppe (HS12) and
gley soils (H S7a,H S9a) developed above the Kallikleios Soil (H S6). Several cyclicities
seem to be mixing in this very last substage o f the H olocene: a 1000 years cycle for the
brown soils interfering with a 500 years, o r even a 250 years cycle if the w eaker soils
are taken into account. It means that during Historical T im es, w oodlands, steppe and wet
lands alternated m ore frequently than was hitherto accepted, interfering with low energetic
river activity phases resulting in the deposition o f m ainly sandy loam s and loam y sands.
Further to the soil cyclicities in the M arathon plain the grouping o f HS 1, HS2, and HS3
to H S6, and HS7 to HS12 subdivides the H olocene sequence into the four well known
and above mentioned geoclim atic substages o f 2500 years each in duration i.e. the Suess
carbondioxide cycle. It should be stressed that these four m ajor geologic subdivisions correlate
extrem ely well with the M esolithic, the N eolithic, the Bronze Age and the H istorical Times
periods respectively.
Sim ilar conclusions are draw n from the hypostratotype o f Kratilou in the Kifissos Valley,
west of Athens. H ow ever, here the num ber o f soils and sedim ent facies changes in the
tranquil depositional environm ent o f the Kifissos river reveals a much greater variety than
274
1 0 0 K=YERR CYCLES
/
LOST IOO=K CVCLE
/
L0S1 10=K CYCLE
2 K
'1 OK
GS15
100
GS12
GS I I
200
IK
2BK
28 K
400
2K
GS 9
500
t
HS 18
HSJ7
300
54 K
je h j
a
*
ESI G
OK
limn
U
m
CO
I
1K
4BK
HS11
700
HS10
45 K
800
0
§
2 K
50EC
900
Ha
SI 0{
GS 7
58 K
-5K
61 K,
S DK
GS 6
GS 5
SI 2
1.3
-
HS5
69 K
•c
70K
- 4K
" 73 K
S13Í
S 141
5a
DQK
1.6
8K
90K
HS8
- 5 K
Hsa
6 K.
SI 7
95 K
GS3
SI0
00
I IRK
B í
S20
2.0
11 OK
S21
GSI
BK
2.1
----------------------1 1 5 K
m
L ast
In te rg l^ a a l
.
2.2
1 215C
PK 1
2.3
»I 2 7 K
2.4
2.5
■ 7 K
130K
PL IO C EN E
QURTERNRRY SOIL SEQUENCES
Figure 7. Q uaternary soil sequences.
275
in the restless alluvial fan sequence o f the M arathon Plain. Especially within the
A tlantic/N eolithic Substage, in w hich no such subdivision could possibly be made in the
M arathon Plain all types o f soils, like deciduous b ro w n soils, steppe soils and gley soils,
equal to those occurring in the Sub Boreal and Sub A tlantic Substages of the M arathon
H olostratotype, are now represented. T hese additional soil levels reconfirm the existence
o f cyclicities o f 1000, 500 and 250 years. A total o f tw enty soils, as stated above, have
finally been recorded (F ig.7).
The revealed 1000 years cycle o f the strong brown/red soils of deciduous forest development
and the 500 and 250 years cyclicity o f the intercalated steppe and gley soils point at quick
changes in the m oisture/tem perature balance within th e m ajor 2500 years cycle.
Surprisingly again these smaller soil cyclicities are repeated in the sequence of civilisations
o f the B ronze Age (the 500 years cycle) and o f the H istorical Tim es (the 250 years cycle)
so that one could almost speak o f an environm entally determ ined historical evolution.
M oreover, the 1000 years cycle reveals a recurrent cyclicity o f extrem e drought (Paepe,
1986) which probably becam e effective since the beginning o f the Holocene, but certainly
since the 8th century BC (the A gora drought). R ecurrences are found at the 2nd century
A .D . (the Roman drought), the 12th century A .D . (the A kom inatos drought) and finally
today in the 20 century A .D . (the Sahel drought). T hese interfere in time with rises in
sea level as was found from many places along the N orth Sea and the M editerranean shores.
6.
Conclusive Remarks on the Soil Cyclicities
The great num ber o f soil cyclicities which exist throughout the Q uaternary at the long term,
m iddle term , and short term level prove at the same tim e the com plexity of the drought
and sea level changes. All three levels o f cyclicities are operating in a kind o f sequential
system , the first step being an interglacial o f the long term cycle followed by the short
term cycle w hereafter the m iddle term cycle is enhanced until finally the next interglacial
shows up and the system is repeated again.
W ithout precise knowledge o f the tim e boundaries w ithin which the cycles operate it
will rem ain difficult to forecast which type o f cyclicity is generating a drought or sea level
change o r any other natural hazard. T he prediction o f the re-enforcing effect o f natural
clim atic changes on the greenhouse effect o r vice versa henceforth rem ains difficult.
T he final discussion w ill focus on the position and the tim e stability o f the Interglacial
Soil in the long term , m iddle term , and short term cycles, which are essential parameters
to be determ ined. The interglacial soil represents indeed the land surface which in the past
was covered to its maximum extension by the m ost dense forest vegetation including the
tropical forests, several times. Its rhythm o f disappearance and reappearance within certain
boundaries o f time, as stated at the beginning o f this paper, covers so many moments of
the landscape evolution that it should obviously be regarded as one o f the most important
counterparts to the deep sea records to be used in the detection o f climatic changes.
6.1. PO SSIBLE STRATIGRAPHIC PO SITIONS O F AN IN T E R G L A C IA L SOIL
U nlike the Last Interglacial Pedocomplex (PK) at Koroni (Greece) or Zelzate (Belgium)
276
the M arathon Soil is not underlain by m arine deposits in the M arathon plain. Instead, the
thick gravel bed which is definitely a consequence of the maxim um sea level rise of the
Holocene Atlantic Climatic Optimum (the Flandrian transgression) covers both the Marathon
Soil (HS1) and HS2. Indeed, there is a possible confusion betw een the M arathon Soil which
was formed some 3000 years before the Clim atic O ptim um below the gravel sedimentation,
and the Kallikleios Soil (HS12 o f F ig .6) o f com parable intensity of developm ent as the
M arathon Soil, which was form ed 3000 years a fte r and above the gravel body. Both red
clay soils should be considered in the sequence o f the twenty H olocene Soils, as typical
interglacial soils whereas the other ones, as th e brow n soils, steppe soils, and gley soils
o f much weaker development, should be interpreted as interstadial soils of the same interglacial
stage.
The very question to be answered is with w hich o f the stratigraphical positions the
interglacial soils o f the long term and middle term cycle should be stratigraphically compared:
with the Marathon Soil (HS1) o r with the K allikleios Soil (HS12) at the beginning or in
the m iddle o f the Holocene interglacial respectively? In other words: with the one before,
or after the maximum o f the interglacial transgression?
It should also be pointed out that in the M arathon Plain both the M arathon and Kallikleios
Soils are converging together into a complex soil entity with increasing distance from the
sea (which in the M arathon Plain is less than 2 km .). M ore inland, on the surrounding
heights outside the plain, w here this complex soil entity is resting on pre-holocene or even
pre-quaternary deposits, it is once m ore converging with the Holocene most recent topsoil
(HS20), thus representing only one single H olocene interglacial soil composed o f the Marathon
Soil, the Kallikleios Soil, and the topsoil (in F ig .6 labelled as HS1, HS12 and HS20
respectively) together.
W ith regard to the possible stratigraphical position of the Last Interglacial soil in the
Holocene sequence, its equivalent o f the middle term record of 127K-years and the interglacial
soils o f the 2.4 M a years long term Q uaternary record may be o f a fourfold origin:
- the single interglacial soil o f the beginning o f each interglacial stage;
- the single interglacial soil o f the middle interglacial stage;
- the soils o f the beginning and the m iddle interglacial stage combined into an interglacial
complex;
- the interglacial complex com bined with the present topsoil.
6 . 2 . T H E POSITION OF T H E LAST IN T E R G L A C IA L SOIL
- T he Last Interglacial Soil is occupying a sim ilar position as the single m iddle holocene
soil when occurring above marine deposits o f the Last Interglacial transgression maximum;
in this position its age is covering only the upper 1/3 of the isotope stage 5e.
- T he Last Interglacial also com pares to a single holocene interglacial soil when it occurs
at the basis o f the m arine interglacial deposits although its age is covering then more .
than 2/3 o f the 5e isotope stage.
- Usually both Last Interglacial Soils at the base and at the top o f the m arine deposits
277
appear together in the same sequence.
- T he L ast Interglacial soil occupies a position o f the com plex soil (beginning and middle
interglacial interpenetrating into one polycyclic so il) when occurring on a plateau in
continental sequences as e.g. loess deposits; it is then also representing alm ost the entire
interglacial tim e span if considered to be 10,000 y e ars.
- Finally it seem s not really to m atter whether the H o lo cen e topsoil is present or not as
it lacks the status o f a fully developed interglacial soil.
6.3. T H E T IM E STABILITY OF T H E IN TERG LA CIA L S O IL
6 .3 .1 . Taking the H olocene as an Inter glacial Soil Stratigraphie M odel o f 10,000 Years
Long, the Last lnterglacial Soil Does N ot Cover the E n tire Isotope Stage 5e (Between 127K
and 115K BP).
- Actually only the last 1/3 o f the tim e when resting on m arine deposits; geosoils of an
age younger than 115K-years should then be totally integrated into the Last Glacial (GS)
soil record.
- On land Last lnterglacial soils may occasionally be interpenetrating with early Glacial
Stage soils (GS soils) as e.g. in the case o f loess soils like the Rocourt Soil. Even then
only 2/3 o f 5e is covered.
6.3.2. The Single lnterglacial Soils o f the Long-Term 1 0 0 K Sequence M ay Very Well Form
In Less than 50 0 Years (Probably Even In Less than 2 5 0 Years) Considering the Revealed
Cyclicities in the H olocene Soil Sequence.
- The tim e stability o f a single (monocyclic) interglacial soil may thus be estimated at
the order o f 0.5 % and 0.25 %.
- A complex interglacial soil being a combination o f the interglacial soils from the beginning
and from the m iddle o f the lnterglacial, thus covering a timespan o f roughly 5000 years
is still indicating a tim e stability o f 2% .
- If the interglacial soil is composed o f the base, the m iddle, and the topsoil, representing
a 9000 years interval there is still a tim e stability o f less than 10%. The latter should
not be taken into account if the topsoil should not really be considered as an element
o f the interglacial soil process, as was stated above.
- M ost o f the interglacial soils being either o f the d ouble complex type or o f the single
type as they seem to occur above deposits o f the maximum interglacial marine transgression
(Fig. 3 & 4) leads to the assumption that the tim e stability o f occurrence o f the interglacial
geosoil is m ost probably o f the order o f 2 %.
- Palaeosoils, or better geosoils, are stable fossil indicators o f palaeoclimatie evidence.
Even when only a few geochronological datings are available, geosoils may be fitted
in at regular tim e intervals because o f their high degree of tim e stability.
6.4. GEOSOILS A N D GLOBA L CHANGE
- U nlike most other fossils, geosoils are very little tim e transgressive. The North-South
278
Geotraverses o f the long term- and middle geosoil cycles prove that. Recent studies reveal
a sim ilar status for the Holocene soil cycles b u t more study is still needed.
- G eosoils, as stated before, are doubling o r e v e n tripling showing the sensitivity of the
Equatorial Belt to the Global Circulation System. A time stability of 2% for these geosoils
proves that the doubling or tripling are isolated, independent climatic, features and certainly
no casual appearances o f a local situation. T h e presence o f two soils or m ore instead
o f one, indicates that the tropics were able to re g iste r the global clim atic changes better
than anyw here else on this planet.
- The myth o f a high latitudinal interglacial being th e equivalent o f an equatorial interpluvial
and the glacial being the equivalent o f a p lu v ial is hereby defenitely banned. When it
was dry at the higher latitudes it was also d ry a t the low er ones.
6.5. DEFO RESTA TIO N AND SOIL D EG RA DATION
- This study may finally help to clarify the pro b lem o f "natural" deforestation and natural
forest regeneration, both obviously bound to th e same m ultiple series o f cyclicities as
the geosoils and the geomorphic surfaces on w hich the soils developed. W ith respect
to the four recognised moments o f geosoil developm ent from sedim ent accumulation,
to surface developm ent, to vegetational developm ent, and finally to soil development,
these are substantial elements o f all these cyclicities and becom e so to say automatically
operational at the appropriate moment in the geosequence cycle leading to the geosoil
developm ent.
- As with geosoils, forests do disappear and rejuvenate naturally as a response to global
clim atic change in the course o f geologic tim e. D eforestation and soil degradation should
then be seen essentially as a man induced feature. The present dem ands of Mankind
and its Society on its natural environm ent, th e Biosphere and the G eosphere, are in a
sharp disharm ony with the possibilities o f c u rre n t natural regeneration possibilities of
forest and soils. T he long term geoclim ate at th e end o f the current interglacial indeed
sets back the well established landscape equilibrium of the last three thousands years
(Kallikleios Soil). This process of disintegration is re-enforced by the natural desertification
due to the 1000 years historical cycle. M a n k in d 's demands for a natural equilibrium
o f its present environm ent stands in a sharp co n trast with the point o f cyclic evolution
which has been reached in the dynam ic equilibrium of the Biosphere and the Geosphere.
It is not at all clear in what stage the Greenhouse effect is influencing the dynamic equilibrium,
at a m om ent in the geoclim ate' s evolution w here biodiversity should norm ally be decreasing
and landscape changes are dramatically different to those that were prevailing mainly during
the last three m illennia in which M ankind w itnessed the dawn of its H istorical Civilisations.
279
7.
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