Loess Dutch

Eiszeitalter und Gegenwart 51 1 1 4 - 1 3 0

7 Abb. Hannover 2002

Loess stratigraphy in Dutch and Belgian Limburg

ERIK P. M . MEIJS*)

MEIJS, E. P. M . (2002): Loess stratigraphy in Dutch and Belgian Limburg. - Eiszeitalter und Gegenwart, 51: 115- 131; Hannover 2002.

Keywords: Loess stratigraphy, quaternary paleopedo- logy, heavy mineral analysis, Belgium, Netherlands.

Abstract: Purpose of this paper is constructing a loess- stratigraphical framework for a small region along the Albert Canal in Dutch and Belgian Limburg. Field ob­

servation and heavy mineral analysis are central focus of this study.

The large-scale sediment trap environment, at scarpe foots or between river-terraces led to the conservation of thick and differentiated loess sequences. The exposed walls of the widened Albert Canal, loess sections in the adjacent loess-exploitation zone and excavations at four major archeological sites did provide important data.

By means of characteristic lithological and paleopedo- logical "marker" horizons, mineralogical and chrono­

logical data and correlation with loess sections in Ger­

many, a reliable loess-stratigraphical framework has been constructed. Beginning with the Holsreinian, it is match­

ing marine/ice isotope records and terrestrial lacustrine pollen records. It contains four glacial loess cycles with five intercalated interglacial paleosols on top of the Rothem river terrace of the Maas.

[Lössstratigraphie in Niederländisch und Belgisch Limburg]

Kurzfassung: Ziel dieser Veröffentlichung ist es, für einen Abschnitt entlang des Albert Kanals in Nieder­

ländisch und Belgisch Limburg eine Ubersicht zur Löss­

stratigraphie zu erstellen.

Die Arbeit gründet sich vor allem auf Feldaufnahmen und Schwermineralanalysen.

An Talhängen und zwischen Flussterrassen kam es zur Sedimentation und Erhaltung mächtiger, reich geglie­

derter Lössablagerungen.

Die Wände des Albert Kanals, Lössaufschlüsse im an­

grenzenden Gebiet und vier große archäologische Aus­

grabungen wurden untersucht. Auf Grund von cha­

rakteristischen lithologischen und paläopedologischen Leithorizonten, mineralogischen und chronologischen Daten und deren Korrelation mit Lössaufschlüssen in Hessen wurde eine lössstratigraphische Übersicht für die Zeit seit dem Holstein-Interglazial erstellt, welche sich mit Ozean- und Eisisotopenabfolgen sowie mit

*)Anschrift d e s Verfassers: Drs. E. P. M . MEIJS, A r c h e o g e o l a b , V e u l e n e r b a n k 3 3 , N L - 6 2 1 3 JR Maastricht, T h e N e t h e r l a n d s .

fesdändischen Pollenzonen korrelieren lassen. Es las­

sen sich vier glaziale Lösszyklen und fünf interglaziale Paläoböden auf der Rothem Terrasse der Maas ausma­

chen.

Introduction

Stratigraphical frameworks for loesses have had to be revised frequendy over the past 40 years (see

HAESAERTS

et al. 1981 and

J U V I G N E

et al. 1996).

Because of the similarity of the sediments, sedi- mentological and cryogenic structures and pale­

osols originating from the different warm and cold stages of the Upper Pleistocene, few convincing stratigraphical "marker"-horizons can be detect­

ed. This is especially the case with regards to the pre-Weichselian loess-sediments, which until now, have been difficult to subdivide stratigraphically.

In volcanic regions tephra layers can provide ex­

tensive lithostratigraphical markers. T h e y often show a distinct mineral suite and are direcdy or indirecdy dated by means of absolute dating meth­

ods.

Apart from

1 4

C -dating on humic sediments, char­

coal or molluscs, different forms of T L - d a t i n g have been developed over the past decades. H o w ­ ever, for both of the last-mentioned dating m e t h ­ ods many methodological problems still exist, es­

pecially in loesses, leading to different chronostrati- graphical interpretations.

Since 1945 several researchers demonstrated the importance of heavy mineral analysis for litho­

stratigraphical studies on loess sediments.

Over the past years intensified investigations have taken place in new and enlarged quarries i n the study area. T h e results of heavy mineral analysis, in combination with lithological, paleopedologi- cal and chronological data from the extreme long loess sequences along the widened Albert Canal and in adjacent loess-pits, give new insight into the loess stratigraphy of the study area.

Research area

The research area is shown in Fig. 1. It is located

in a part of the drainage basin of the river M a a s .

Since the middle Pliocene (4 ma) the M a a s met

L o e s s stratigraphy in D u t c h and Belgian Limburg

115

the Rhine near Aachen (Germany). Afterwards the Maas moved westwards and started around 800 ka to erode the Cretaceous and Paleocene lime­

stones and Oligocene sands in the study area (van den B e r g 1996). The continuous uplift of the area, the alternation of glacial and interglacial periods and the lateral westward shifting of the Maas were responsible for the preservation of an extraordi­

nary extended and complete river terrace sequence.

Transition periods between interglacial and glacial times were favourable for river-erosion and inci­

sion, while gravel-accumulation took place under cold and severe conditions, on the base of widely observed cryogenic features within the gravel beds

' (van den B e r g 1996). Interglacial regimes favoured the formation of river floodloams and lateral ero­

sion. After the retreatment of the Maas from the research area, the preserved river terraces were al­

ternately eroded by wind- and water-action and covered by eolian sands and loesses. The bounda­

ry between the coversand area in the north and the loess belt in the south is located near Gellik (Fig. 1). T h e present landscape is smoothly undu­

lating, with SW-NE orientated valleys, draining to the rivers Jeker and Maas in the east.

Several brickyards are exploiting loess-pits near Kesselt and Veldwezelt (Nelissen pit "Kesselt" and Vandersanden pits "Veldwezelt-Hezerwater" and

^Eindhoven

^--v 777e

NETHERLARY.

BELGIUM 1

S/ Dusseft

GERMANY

A torf N 1

^Eindhoven

^--v 777e

NETHERLARY.

BELGIUM 1

Maastricht Cologne? W[

• ( i v . v . v . v . v . v . v ;

® Aachen

30 km

Fig. 1: Location o f the study area a n d position of the cross sections L - M , A-K, a-b, d-c, f-e, g-h a n d i - j , w h i c h are shown in Fig.

2, 4, 5 and 6. A t t h e right bottom: t w o fossil meander c h a n n e l - b e d s from R o t h e m - 1 and R o t h e m - 2 river-terraces are indicated on the base o f o u t c r o p and drilling information.

Abb. 1: L a g e des Forschungsgebietes u n d Lokalisierung d e r Aufschlüsse L-M, A-K, a-b, d-c, f-e, g-h u n d i-j in Fig. 2, 4, 5 u n d 6. In der rechten unteren Ecke sind, b a s i e r e n d auf B o h r u n g e n und Aufschlüssen, zwei fossile M ä a n d e r b ö g e n der R o t h e m - 1 und R o t h e m - 2 Flussterrasse w i e d e r g e g e b e n .

1 1 6 ERIK P. M . MEIJS

"Op de Sclians"). In fact the area along the Albert C a n a l is an i m p o r t a n t l o e s s - e x p l o i t a t i o n z o n e which will be further investigated in the future.

T h e Nelissen pit "Kesselt" was, until 1996, the t y p e - l o c a t i o n for the s o - c a l l e d H e s b a y e l o e s s , which induced research by several universities. In the future this site will possibly be assigned as the type-location for the rare Upper Saalian " B - l o e s s "

(see chapter chronostratigraphy). The Vandersand- en c o m p a n y started exploiting the loess-pit " O p de S c h a n s " in March 2000 (Fig. 1). For the study of pre-Weichselian loesses, it is a promising loca­

tion because it is situated in line with the most complete and differentiated pre-Weichselian out­

crop along the widened Albert Canal (Fig. 2 ) . Between 1975 and 1985 the Albert Canal was wid­

ened and detailed research of the exposed walls led to a thorough understanding of the geological and geomorphological genesis of this area. Ex­

posed sediments in neighbouring loess-pits were then correlated to the Albert Canal sequences.

T h e discovery of four major archeological sites (Maastricht-Belvedere, Kanne, Kesselt and Veld- wezelt-Hezerwater) in the research area led to ad­

ditional stratigraphical and chronological research.

In conclusion, the research area could be consid­

ered as a key-region for present and future loess- stratigraphical research.

Terrace sequence of the river Maas In Fig. 2 the roughly SW-NE and S-N orientated cross-sections clearly show the strong influence of river erosion and aggradation processes in the area. T h e cross-section Lafelt-Oud Caberg (A-K;

Fig. 2 bottom) is constructed on recorded sections along the Albert Canal and adjacent loess-pits and a d d i t i o n a l d r i l l i n g i n f o r m a t i o n

( H a l e t

1 9 3 2 ,

F e l d e r & B o s c h

1989 and

G e o l a b

1996), while the Vroenhoven-Veldwezelt cross-section (L-M;

Fig. 2 top) is based on outcrop-information along the w i d e n e d wall of the eastern side of the Albert Canal. Four distinct river terrace sequences can be distinguished. According to gravel-base heights the R o t h e m terrace-level seems to be divided into two sublevels; representing an outward sliding meandercurve-complex (Fig. 1). In a wider con­

text,

F e l d e r & B o s c h

(1989) deduced from the presence of different gravel-bases and two distinct f l o o d l o a m g e n e r a t i o n s , t h e e x i s t e n c e of two Rothem sub-levels: Rothem-1 and Rothem-2. As well for the Gravenvoeren level, a distinction be­

tween Gravenvoeren 1 and 2 seems justified, al­

though section F-H in Fig. 2 is the only example

of a terrace-division in the Gravenvoeren sequence throughout the Maas terrace area between Liege in B e l g i u m and Roermond in The Netherlands

( F e l d e r & B o s c h

1989 and

v a n d e n B e r g

1996).

According to

F e l d e r & B o s c h

(1989) the Pieters- berg and Maarland terrace levels are present over a distance of 100 meters, in a SW direction from point A and in a NE direction from point K seen in the cross-section Lafelt-Oud Caberg, with gravel bases at about 98 m A S L and 38 m A S L (Fig. 1, Fig. 2).

It is clear that during long periods a sediment-trap existed between the heights of the Pietersberg and Gravenvoeren terraces, which resulted in an ex­

tremely thick loess cover in between.

H e a v y mineral analysis

As stated above, lithological, sedimentological and paleopedological analyses of loesses are rarely able to discriminate between the different w a r m and cold stages of the Upper Pleistocene. However, correlations between different loess sections can be strengthened and stratigraphical conclusions can be drawn by means of heavy mineral analysis.

In c o m b i n a t i o n with m i c r o m o r p h o l o g i c a l and lithological research, the content of the g r e e n amphibole and volcanic minerals are used to cor­

relate individual loess sections and to construct a loess-stratigraphical framework for the research area.

Methods Loess minerals:

T h e investigation of the mineralogical composi­

tion of the loess fraction (30-63 g m ) in relation to the loess stratigraphy began in The Netherlands

( v a n D o o r m a e l

1945). This research was continu­

ed by

G u l l e n t o p s

(1954),

L a u t r i d o u

(1968),

J u - v t g n e

(1978,1985),

B a l e s c u & H a e s a e r t s

(1984),

M e i j s

(1985),

J a n u s

(1988) and

H e n z e

(1998) in the loess-belt of France, Belgium, The Nether­

lands and Germany.

J u v i g n e

(1978) proposed the ratio between "green amphibole + garnet / zir­

con + rutile" to distinguish Weichselian loess from pre-Weichselian loess. This approach was adopt­

ed in G e r m a n y by

H e n z e

(1998). Both

G u l l e n ­ t o p s

(1954) and

M e i j s

(1985) mentioned the i m ­ portance of green amphibole as a discriminating heavy mineral in stratigraphical research. Accord­

ing to

B a l e s c u

et al. (1986) the West-European

loess-belt is divided into separate regions w i t h

specific mineralogical properties. This implies that

green amphibole percentages may differ slighdy

between these regions. The overall tendencies how-

Loess stratigraphy in Dutch a n d Belgian Limburg

117

Albert Canal-east Vroenhoven-Veldwezelt

M.ioo

FELDER A MEIJS, July 2 0 0 0

S o u t h - W e s t A Lafelt

cross-section Lafelt-Oud Caberg

Gravenvoeren-1 terrace

LEGEND

EPÜ Cretaceous and Paleocene limestone Oligocene sand

Maas gravel brook gravel

Maas floodloam (sand and clay) brook floodloam brook sand coversand

EH •

E3

"7J

loess clayey loess geliflucted loess luvisol pod sol pale horizon humic horizon

3 1

m

tundrasol ice-segregation horizon Nagelbeek tongued horizon patina layer Rocourt tephra

N1/2 Upper Saalian tundrasol CL clayey loess

lower decalcification limit

Moqs & Felder. Ap-D 2000

Fig. 2: S W - N E a n d S-N cross-section showing t h e g e o m o r p h o l o g i c a l a n d geological structure o f t h e study area. T h e role o f fluvial/eolian erosion and a g g r a d a t i o n processes are p o i n t e d out.

A b b . 2: S W - N O u n d S-N Querschnitte, w e l c h e d i e g e o m o r p h o l o g i s c h e u n d g e o l o g i s c h e S t r u k t u r d e s Gebietes darstellen.

Auffallend sind die Hinweise a u f fluviatile u n d ä o l i s c h e Abtragungs- u n d Sedimentationsprozesse.

ever are the same. Even in northern Germany drill­

ing data from

HENNINGSEN & STEPHAN ( 2 0 0 0 )

showed that the amount of green amphibole in­

creases from the Elsterian to the younger Saalian and Weichselian sediment series.

Requivenient for this kind of stratigraphical re­

search however, is that the samples should b e of

"real" eolian loess, as loess may have been rede- posited and may be contaminated with older un­

derlying material, mixing the green amphibole con­

tent.

Wet sieving of chemically untreated samples was carried out to obtain the fraction 3 0 - 6 3 m m . T h e heavy a n d light minerals were separated in bro- moform by using a centrifuge and the heavy min­

eral fraction w a s sucked u p using a micropipet.

From each sample about 3 0 0 transparent heavy minerals w e r e counted, using the ribbon-count­

ing method as described by

VAN H A R T E N ( 1 9 6 5 ) .

The percentage of green amphibole in the frac­

tion 3 0 - 6 3 g m was calculated based on the total amount of all counted transparent heavy miner­

als.

Volcanic minerals:

Until n o w only three volcanic tephra layers have been found in the research area, all originating in the volcanic Eifel in Germany.

Minerals from the Laacher See tephra have been detected on the archeological site of K a n n e by

PAULISSEN

et al.

( 1 9 8 1 ) ,

just on top of the Holocene soil, that was burried b y colluvium. The Laacher See tephra, 1 2 , 2 5 0 calibrated years BP, occurs in more than 5 0 pollen diagrams (Germany, Belgium, France and Italy) in the final phase of the Allerod

oscillation (JUVIGNE 1 9 9 3 ) .

The Eltville tephra is the only tephra-layer visible by eye. It lies just beneath the Nagelbeek tongued horizon (NB) and is dated by

^{1 4}

C and T L methods

b e t w e e n 1 6 and 3 0 ka (JUVIGNE 1 9 9 3 ) .

118 ERIK P. M . MEIJS

Like the Laacher See tephra, the Rocourt tephra is only detectable by using microscopical equipment and occurs in secondary position in colluviated humic material, just above the Rocourt pedocom- plex of the last interglacial

( G U L L E N T O P S

1954,

J U V I G N E

1977,

M E E S & M E I J S

1984). T h e estimat­

ed age on the base of indirect

1 4

C and

2 3 0

T h -

2 3 4

U - datings lies between 61.5 and 106 ka

( J U V I G N E

1993).

Stratigraphically the Eltville tephra is less interest­

ing than the Rocourt tephra because the Nagel- beek tongued horizon (NB), which lies in the same stratigraphical position as the Eltville tephra, is a very characteristic and almost always present mark­

er horizon from the French coast to eastern Eu­

rope

( H A E S A E R T S

et al. 1981,

M E I J S

et al. 1983).

For the mineralogical research of tephra-material, the sediment-fractions 63-106 m m (Laacher See tephra) and 106-300 m m (Rocourt tephra) were used. T h e further preparation and counting is sim­

ilar to the above-mentioned methods used for the green amphibole analysis.

Description and results

In this chapter four major litho-pedological units are described separately; namely "A-loess", " B - loess", " C - l o e s s " and "D-loess" (Fig. 3). From each unit samples were taken for heavy mineral a n d / o r micromorphological analysis. The results are pre­

sented and discussed beneath.

Loess cycle A (max. thickness at location "Veld- wezelt-Hezerwater": 24 meter)

In lower topographical positions and in shallow paleovalleys this sequence often starts with the presence of white-greyish ( 1 0 Y R 5 / 4 ) pale sedi­

ment, followed by darkbrown ( 1 0 Y R 4 / 3 ) humic material, most often directly covering the redbrown coloured ( 1 0 Y R 5 / 8 ) Rocourt pedocomplex of the last interglacial. The material predominantly con­

sists of redeposited loess-sediment, from the Ro­

court p e d o c o m p l e x

( J U V I G N E

1 9 7 8 ,

V A N D E N ­

B E R G H E

et al. 1998). The base of both horizons,

especially that of the humic horizon, is of erosive origin (Fig. 5 bottom). The lower part is heavily bioturbated, leading to the formation of a mixed zone between the humic material and the pale se­

diment with numerous krotovinas. T h e humic ho­

rizon is often divided into three sublevels

( M E E S

& M E I J S

1984,

H A E S A E R T S

et al. 1999); the bottom and top consisting of dark brown material and the middle part of lightbrown material that may laterally merge in a downslope direction into a grey­

ish pale horizon (Fig. 5 bottom). Just on top of

this humic horizon a yellowish loess is sometimes present ("marker-loess"), representing the first eolian loess-supply since the last interglacial peri­

od.

Just after the outburst of the Eltville tephra, the climate was extremely cold and dry. As a result, a polar desert pavement ( P L : patina layer) formed, discordantly lying upon the older deposits with windblown gravels at its base. T h e term "patina layer" has been chosen because of the clearly visi­

ble wind varnish (patina) present on the recov­

ered paleolithic artefacts from this horizon. T h e wind erosion created a totally n e w landscape, dis­

regarding the underlying valleys and ridges (Fig. 4 and 6). In fact it formed more or less the present landscape, because only a blanket of pure eolian loess was deposited on top of it afterwards, with no erosion phases in between (Brabant loess). T h e most important soil-formation phase which took place after the formation of the desert pavement r e s u l t e d in t h e f o r m a t i o n of t h e N a g e l b e e k tongued horizon (NB), lying just on top of the desert pavement and showing characteristic cryo- turbation features at its base

( H A E S A E R T S

et al.

1981).

In general the underlying Eltville tephra is eroded during this wind erosion phase. Only in excep­

tional topographical positions, such as sediment- traps, the tephra is preserved.

The present study and earlier studies

(VAN D O O R - M A E L 1945, G U L L E N T O P S 1954, L A U T R I D O U 1968, J U V I G N E 1978, B A L E S C U & H A E S A E R T S 1984, M E I J S

1985,

J A N U S

1988 and

H E N Z E

1998) reveal that the green amphibole percentages in Weichselian loess deposits range from 8 to 4 0 % . In the study area the mean percentage for the loesses deposited, just above the humic horizon, is around 10%. Above these first loesses the percentage quickly reaches the mean values for the "A-loess" in this region, around 2 0 % (Fig. 5 middle part).

A s seen before, volcanic minerals of the Rocourt tephra have b e e n microscopically traced in the above-mentioned humic horizon. T h e minerals occur in secondary position throughout the hum­

ic material but often show a distinct concentra­

tion peak on top of the lower h u m i c sublevel

( M E E S & M E I J S 1984, M E I J S & G R O E N E N D I J K 1999,

personal communication

G U L L E N T O P S

1999; Fig.

5 bottom).

Apart from the serrated appearance of the clinopy- roxines, the presence of enstatite is very diagnos­

tic for the Rocourt tephra

( G U L L E N T O P S

1954, J u -

Loess stratigraphy in D u t c h and Belgian Limburg 119

Meijs. August 2000

Fig. 3: M o d e l , showing the proposed litho-pedological relations b e t w e e n the most i m p o r t a n t loess sections. T h e numbers are indicating the percentages of green a m p h i b o l e from l o e s s - s a m p l e s in the fraction 30-63u.m. In this figure the tundrasols are indicated by dashed lines. For legend see Fig. 2.

Abb. 3: Sammelprofile für d a s Untersuchungsgebiet, w e l c h e die litho-pedologischen Z u s a m m e n h ä n g e z w i s c h e n den wichtig­

sten Lössaufschlüssen andeuten. Die Zahlen g e b e n den Anteil v o n g r ü n e n A m p h i b o l e n [in % ] am S c h w e r m i n e r a l s p e k t r u m (Fraktion 30-63u.m) wieder. Tundrenböden sind durch punktierte L i n i e n angedeutet. L e g e n d e siehe Fig. 2.

viGNE 1977). T h r o u g h microprobe analysis J u ­ v i g n e et al. (1996) were able to detect the pres­

ence of volcanic glass shards in the heavy mineral section.

Recent mineralogical research reveals the presence of the Rocourt-tephra at three locations in the research area (Fig. 3, 5 and 6). Concentration val­

ues can decline dramatically in downslope as well in upslope directions in the same stratigraphical position (Fig. 5 bottom; see also Juvigne 1977).

Fig. 5 shows that in extreme cases percentages are tending towards zero. T h e weakly developed hu­

mic horizon on the northern side of this section does not show any volcanic minerals at all.

Loess cycle B (max. thickness at location "Kes­

selt": 12 meter)

Thick loess sequences situated beneath the Rocourt pedocomplex are very rare. The relative abundance

of these deposits in the research area is explained by the presence of geomorphologically defined se­

diment-traps between the different river terraces of the Maas. The most impressive "B-loess"-sequence is present in the Nelissen pit "Kesselt" which has been issue of smdying by several universities dur­

ing the past 50 years (Fig. 6). Here, even calcareous

"B-loess" is found which has not been influenced by the soil-formation processes of the last intergla­

cial. In the Nelissen pit, the so-called "B-loess" se­

quence has been interpreted as middle Weichselian from the first description of the section ( G u l l e n ­ t o p s 1954) until 1996. In 1996, the uncovering of the Rocourt pedocomplex and the presence of the Rocourt tephra on top of it allowed J u v i g n e et al.

(1996) to put the " B - l o e s s " sequence into the time

before last glaciation (see also chapter chronostrati-

graphy).

120 ERIK P. M . M E I J S

The " B - l o e s s " sequence starts with a polar desert pavement, which in general is less pronounced than that of the "A-loess" and shows more features of water activity. Locally, the influence of running water is distinct, showing large and shallow gully systems. This wind and water erosion phase is re­

sponsable for an important hiatus in the different loess sections. T h e sequence on top of the desert pavement is representing an alternation of loess- sedimentation and five tundrasol-formation phases (N1-N5). Fossil ice-wedge casts are present at three different levels, starting at about 10-20 c m above the paleo-surface of the middle three tundrasols ( M f . e s & M e i j s 1984). T h e greyish ( 1 0 Y R 5 / 3 ) tun­

drasols, especially the lower two, are well devel­

oped and have a characteristic appearance some­

times showing a whitish to greenish ( 1 0 Y R 7 / 1 ) thin layer on top and a strong orange-like, rusty ( 1 0 Y R 5 / 8 ) horizon at the base. They significantly differ from the over- and underlying tundrasols, present in the "A-loess" and "C-loess". T h e dis­

tance between the lower two tundrasols ( N l and N2) varies from 2 to 4 meters and occasionally a faint weak developed tundrasol is present between

them (see also M e e s & M e i j s 1984 a n d H u i j z e r

1993).

A n analogue loess sequence, situated below an Eemian paleosol and containing up to six tundra­

sols, has been reported by B i b u s (1974, 1980) at several locations in Germany and is indicated as the "Bruchköbeler Nassboden-Komplex". Count­

ing from below, the first and the third tundrasol have the most pregnant appearance. In compari­

son with the situation in the Nelissen pit "Kes­

selt" the similarity is striking, considering the fact that the second G e r m a n tundrasol matches the occasionally appearing tundrasol of Kesselt (be­

tween the N l and N 2 ) .

On top of this sequence the Rocourt pedocom­

plex is present at times, especially in sediment-traps like paleovalleys and scarp foots (Fig. 3, 5 and 6).

Here periods of colluviation alternated with sub­

sequent soil-formation finally produced a complex soil-profile showing several generations of clay- illuviation, leaching and polygonal developement

( H a e s a e r t s & V a n V l i e t - L a n o e 1 9 8 1 , M e s t d a g h

& H a e s a e r t s 1 9 9 8 , V a n m o n t f o r t et al. 1998,

S c h i r m e r 2 0 0 0 a n d p e r s o n a l c o m m u n i c a t i o n M O c h e r 1999). T h e issue of chronostratigraphi- cal correlation with M I S - 3 instead of M I S - 5 will be discussed in the chapter dealing with chrono- stratigraphy.

The green amphibole percentages in the "B-loess"

range from about 2 0 % at its base to around 5 % in

the loess-sediments deposited at the e n d of this period, just prior to the onset of the last intergla­

cial. In general the " B - l o e s s " is heavily truncated.

In such a situation only the lower amphibole-rich part is preserved from erosion and the overlying tundrasols and Rocourt pedocomplex are missing (Fig. 4 ) . In that case distinction between "A-loess"

and " B - l o e s s " by m e a n s of their green amphibole content is not possible. Until 1984 loess sequenc­

es with high green amphibole percentages were assigned to the "A-loess". In the mid-eighties how­

ever B a l e s c u & H a e s a e r t s (1984) a n d J u v i g n e

(1985) found in northern France and eastern Bel­

g i u m an interglacial paleosol between loess layers with a high green amphibole content a n d it lasted until 1996 that J u v i g n e et al. (1996) discovered the same situation for the sequence in the Nelis­

sen pit "Kesselt" (see Fig. 6). Taking into account these n e w insights, the stratigraphical framework had to be revised and a great part of the so-called Hesbaye loess ("A-loess") was interpretated as " B - l o e s s " ( J u v i g n e et al. 1996).

T h e consequent decrease of the green amphibole content from the older to the younger layers is striking (Fig. 6). T h e decrease of these percentag­

es towards the end of the "B-loess" period has also been reported in northern France and east­

ern Belgium by B a l e s c u & H a e s a e r t s (1984) and J u v i g n e (1985). J u v i g n e (1985) suggests that the

chemical weathering of green amphibole could provide an explanation. However, as shown in Fig.

6 g r e e n amphibole percentages already start to diminish within the calcareaous loess, which has not been influenced by chemical weathering proc­

esses at all. Thin section, grain-size and sedimen- tological analyses all point to an upward coarsen­

ing, a decrease in mineral sorting, a diminishing soil-stability and an increasing stream power re­

g i m e in an upward direction within the " B - l o e s s " -

s e q u e n c e ( H u i j z e r 1 9 9 3 , V a n d e n b e r g h e et al.

1998). This implies that the climate w a s changing from d r y towards m o r e moist conditions. In ac­

cordance to the study area (Fig. 6) B i b u s (1980) reported wide spread overlandflow activity in the a b o v e m e n t i o n e d G e r m a n loess s e c t i o n s , just above the sixth Bruchköbeler tundrasol, before the onset of the last interglacial. Thus climate change seems a more plausible explanation for decreas­

ing amphibole percentages than chemical weath­

ering.

As proposed by J u v i g n e (1978), the most proba­

ble provenance area for green amphibole is the outwash zone of the Scandinavian icecap. Possi­

bly d r y climatic conditions were a dominant fac-

Fig. 4: O u t c r o p of the w e s t e r n side of the w i d e n e d Albert Canal near Kesselt, showing a massive, almost c o m p l e t e loess sequence. Especially the glacial loess-covers of M i d d l e and L o w e r Saalian age (C- and D-loess) and the interglacial luvisols from the m a r i n e isotope stages (MIS) 5, 7, 9, 11 and 13 are represented. T h e g r e e n amphibole percentages from different loess-samples in the fraction 30-63 urn are indicated by numbers. T h e abbreviations R S , HS, M S , W S , PS and D S are respectively u s e d for the Rocout soil, the H e e s soil, the M o n t e n a k e n soil, the Wolder soil, the Pottenberg soil and the D o u s b e r g soil.

For l e g e n d see Fig. 2

Abb. 4: Aufschluss an der W e s t w a n d des Albert Kanals in der N ä h e von Kesselt mit einer der vollständigsten Löss-Serien dieser Region. Besonders die glaziale L ö s s d e c k e der Mittel- u n d Alt-Saalezeit (C- u n d D-Löß) und die interglazialen Luvisols, die d e n Isotopenstadien (MIS) 5, 7, 9, 11 und 13 entsprechen, sind deutlich erkennbar. D i e A b k ü r z u n ­ g e n R S , H S , M S , W S , PS u n d D S stehen für den Rocourt-Boden, den H e e s - B o d e n , den M o n t e n a k e n - B o d e n , den Wolder-Boden, d e n Pottenberg-Boden u n d den D o u s b e r g - B o d e n . Die Zahlen g e b e n den Anteil des G r ü n e n A m p h i b o l s [in % ] a m S c h w e r m i n e r a l s p e k t r u m (Fraktion 30-63 u.m) wieder. L e g e n d e siehe A b b . 2.

122 ERIK P. M . MEIJS

Fig. 5: O u t c r o p on the e a s t e r n side of the w i d e n e d Albert Canal n e a r Voenhoven s h o w i n g a pedo- lithological s e q u e n c e presenting the Weichselian (A-loess) and U p p e r Saalian (B-loess) p e r i o d s . In the upper two drawings, the g r e e n a m p h i b o l e p e r c e n t a g e s from the different loess-samples in the fraction 30-63 u.m are indicated by n u m b e r s . T h e b o t t o m d r a w i n g shows the variation in the volcanic m i n e r a l content o f the R o c o u r t tephra. T h e n u m b e r s indicate the percentages of transparent, volcanic heavy minerals in relation to all c o u n t e d transparent and o p a q u e heavy minerals in the fraction 1 0 6 - 3 0 0 u.m. T h e abbreviation R S and W S are used for the R o c o u r t and Wolder paleosols. For legend see Fig. 2.

Abb. 5: Aufschluss entlang d e r O s t w a n d des A l b e r t - K a n a l s , in der N ä h e von V r o e n h o v e n , m i t einer Abfolge v o n W e i c h s e l (A) und J u n g - S a a l e (B). D i e zwei o b e r e n Z e i c h n u n g e n g e b e n den Anteil d e s G r ü n e n A m p h i b o l s [in % ] a m S c h w e r m i n e r a l s p e k ­ trum (Fraktion 30-63 um) w i e d e r . D i e detaillierte Z e i c h n u n g unten zeigt die Variation des Gehaltes vulkanischer M i n e r a l e des R o c o u r t - T u f f s . D i e Z a h l e n r e p r ä s e n t i e r e n d e n Anteil der t r a n s p a r e n t e n v u l k a n i s c h e n S c h w e r m i n e r a l e an allen g e z ä h l t e n transparenten und opaken S c h w e r m i n e r a l e n (Fraktion 106-300 u.m). D i e A b k ü r z u n g e n R S u n d W S bedeuten R o c o u r t - B o d e n und Wolder-Boden. L e g e n d e siehe A b b . 2.

Loess stratigraphy in D u t c h and Belgian Limburg 123

S o u t h

Nelissen pit Kesselt

^{N o r t h}

Meijs. January 2000

Nelissen pit Kesselt

Fig. 6: S-N and W-E cross-sections in the N e l i s s a n pit Kesselt s h o w i n g the most c o m p l e t e U p p e r Saalian loess sequence (B- loess) in this region with at least five intercalated fossil tundrasols. T h e n u m b e r s are representing the g r e e n a m p h i b o l e percent­

ages from loess-samples in the fraction 3 0 - 6 3 u.m. T h e a b b r e v i a t i o n s R S and HS are used for the Rocourt a n d H e e s paleosol.

For the l e g e n d see Fig.2.

Abb. 6: S-N- und W-E-Querschnitte durch die Nelissen-Grube b e i Kesselt (einer der Aufschlüsse mit der vollständigsten J u n g - Saale-Lössabfolge (B) der R e g i o n ) , g e k e n n z e i c h n e t durch m i n d e s t e n s fünf fossile T u n d r e n b ö d e n . Die Z a h l e n g e b e n den A n ­ teil des G r ü n e n A m p h i b o l s [in % ] am S c h w e r m i n e r a l s p e k t r u m (Fraktion 30-63 um) wieder. Die A b k ü r z u n g e n R S und H S stehen für den Rocourt-Boden und den H e e s - B o d e n . Legende siehe A b b . 2.

tor in the transport of green amphibole to the research area. During moist to wet climatic condi­

tions a long-lasting snow-cover probably prevent­

ed large-scale deflation from the braided outwash plains.

The uniformity of the green amphibole percent­

ages in the upper part of the " B - l o e s s " and within the Rocourt pedocomplex (4-6%) in the different sections is striking (Fig. 3, 4, 5 and 6). This may mean that at the end of the " B - l o e s s " period an uniform loess blanket was deposited, on which

colluvial and soil-formation processes took place later on.

Loess cycle C (max. thickness at location "Albert Canal-west Kesselt": 7 meter)

Sediments of the " C - l o e s s " sequence are encoun­

tered at two locations in the research area (near Kesselt; see Fig. 4 and 6).

T h e sequence starts with a characteristic clayey

loess (CL). In most cases a weak greyish tundrasol

is present at the base as well as on top of this

124 ERIK P. M . MKIJS

clayey loess. Above, laminated and heavily cryo- turbated loess-sediment occurs, which is overlain by more homogeneous loess with another tundra­

sol transferring upwards into laminated and geli- flucted sediment (Fig. 4 ) . T h e sequence ends with the formation of a red-brownish ( 8 . 5 Y R 5 / 6 ) inter­

glacial soil and overlying pale and humic horizons.

Thin section analysis clearly shows the presence of in situ clay-cutans within the interglacial pale­

osol (MEES 1984). Micromorphological research also revealed that the overlying pale and humic horizons consist of eroded and colluviated mate­

rial with a lot of transported and rounded ferric nodules derived from the interglacial paleosol be­

low (MEES 1984).

According to the mineralogical results presented in Fig. 3 and 4 and on the base of lithological and paleopedological characteristics of the over- and underlying sediments, this interglacial paleosol can no longer be correlated with the Rocourt pedo­

complex. We therefore propose to name this pale­

osol after the neighbouring village of Hees in Bel­

gian Limbourg; the Hees soil.

T h e green amphibole percentages in this sequence are rather constant, ranging from 1-3%. In the Nelissen pit "Kesselt" (Fig. 6) it seems that the p e r c e n t a g e s here also d e c r e a s e u p t h r o u g h the stratigraphy. It may be possible that, given the more laminated and sandy character of the uppermost sediments, this is due to the mixing with older sed­

iment-material from below.

Mineralogical research of the Hees soil and over­

lying pale and humic horizons in cross-section Albert Canal-west Kesselt (Fig. 4) did not reveal the presence of volcanic minerals.

Loess cycle D (max. thickness at location "Albert Canal-east Op de Schans": 8 meter)

In the research area this sequence represents the first eolian cycle after the formation of the wide spread and massive (sandy) floodloams belonging to the Rothem terrace-level of the river Maas.

These sediments have been recognized at two lo­

cations along the widened Albert Canal (near Kes­

selt and Vroenhoven; Fig. 4 and 5).

T h e sequence starts with two different sediment fades. In the beginning, formation of broad, shal­

low gullys took place, filled up by redeposited sandy floodloam material.

Later, coversand was blown out of these gully sys­

tems onto adjacent interfluvia. Locally, a greyish ( 8 . 5 Y R 5 / 3 ) podsolic soil is present on top of both fades, the so-called Wolder soil (FELDER & BOSCH

1988). After the podsol-formation the sedimenta­

tion of coversand, continued in places (Fig. 4).

Soon after however, loess-accumulation predomi­

nated. A t their base the loesses have a laminated character, becoming more homogeneous, although periods of more overlandflow activity m a y inter­

v e n e . T h e s e q u e n c e is closed by a r e d b r o w n ( 1 0 Y R 5 / 6 - 8 ) interglacial paleosol, with a subse­

quent grayish ( 1 0 Y R 7 / 2 to 2 . 5 Y R 7 / 4 ) sandy, pale horizon and a darkbrown ( 1 0 Y R 4 / 4 ) h u m i c hori­

zon. T h e interglacial paleosol is assigned as the Montenaken soil after FELDER & BOSCH (1988) and thin section analysis revealed the presence of at least two clay-illuviation generations (MEES 1984).

T h e large number of charcoal pieces present in the pale horizon is striking. No micromorphologi­

cal indications were found for an existing erosion hiatus between the Montenaken soil and the over­

lying pale and humic horizons. However, glauco- nite grains were found within the Montenaken soil, but not in the sediments above (MEES 1984).

T h e percentages of green amphibole are v e r y low (0.5-1%) in this sequence and are difficult to dis­

criminate between the sediments from b e l o w (Fig.

3 and 4 ) .

T h e Montenaken soil and the overlying pale and humic horizons, were checked for the presence of volcanic minerals. Here also the result w a s neg­

ative.

Rothem river terrace

As mentioned above the Rothem terrace is mould­

ed in the study area as an outward bending mean­

der-curve, with the deepest incision depth at the outerside of the curve (Fig. 1 and 2). D u r i n g the process of lateral and vertical river erosion huge quantities of Oligocene sand were eroded and re- deposited over short distances. The great sediment load probably lead to the accumulation of an im­

portant sequence of alternating clayey a n d sandy floodloams.

This sequence ended with the formation of an intense red-coloured ( 5 Y R 5 / 8 ) interglacial pale­

osol, the so-called Pottenberg soil (FELDER &

BOSCH 1988). In some sections of the widened Albert-canal another redbrown coloured luvisol is present beneath the Pottenberg soil, w i t h inter­

calated floodloam in between (Fig. 2, 4 ) . Probably local river activity of the " C a b e r g - 1 " M a a s gave rise to a thin floodloam cover on top of this pale­

osol. It is representing the equivalent of the warm

period between the formation of the Rothem-2

and Caberg-1 terraces. T h e luvisol is assigned to

L o e s s stratigraphy in D u t c h and Belgian L i m b u r g 125

the neighbouring Dousberg and will be named Dousberg soil (Fig. 4).

T h e earlier results of

B U S T A M E N T E S A N T A C R U Z

(1973), which show negligible green amphibole percentages for the Maas terrace sequences, can be supported by the present study, where the per­

centages range from 0-0.5% (Fig. 4, 6).

Chronostratigraphy

By m e a n s of characteristic "marker" horizons, in combination with mineralogical and chronologi­

cal data and in correlation with the "Bruchköbel­

er" loess sections in Germany ( B i b u s l 9 7 4 , 1980) it is attempted to construct an extended chrono- stratigraphical framework for the research area, which is related to the river terrace sequence of the M a a s , the standard Marine Isotope Stages (MIS) of the astronomical calibrated ocean records O D P - 6 7 7 and M D 9 0 0 9 6 3

( B A S S I N O T

et al. 1994), the dust and temperature successions in the Vos- tok ice core

( P E T I T

et al. 1990,1999) and the long continental pollen records from Massif Central, France

( R E I L L E

et al. 1998) (Fig. 7).

In this respect the Vostok dust record is of major i m p o r t a n c e , indicating continental aridity, dust mobilization and dust transport were most preva­

lent in the full glacial stages. This is also reflected by m a n y other dust records from for instance Greenland (GRIP

M E M B E R S

1993), Africa

( D E M E N - O C A L

1995) and China

( V A N D E N B E R G H E

et al. 1997).

It is obvious that the extreme cold oscillations at the end of interglacial stages were too short to g e n e r a t e l a r g e - s c a l e l o e s s d e f l a t i o n (see also

S C H I R M E R

1999). Both the ice core sequence

( P E T -

rr et al. 1999) as well as the terrestrial pollen records

( T Z E D A K I S

et al. 1997,

R E I L L E

et al. 1998) confirm the presence of four major climatic cycles during the past 400,000 years. Each climatic cycle is start­

ing with an extreme w a r m and humid stage

( R E I L L E

et al. 1998; M I S 11.3, 9.5, 7.5 and 5.5; Fig. 7) and ends with an extreme cold and dry stage

( P E T I T

et

al. 1999, B A S S I N O T et al. 1994, L O Y E R et al. 1995;

MIS 10.2, 8.2, 6.2 and 2.2; Fig. 7).

Weichselian

For the Weichselian period (MIS 2-4) recent mulridis- ciplinary research at the archeological site Veldwezelt- Hezerwater is of great importance. Together with the standard sequences of Harmignies and Remicourt in Belgium

( H A E S A E R T S

1974,

H A E S A E R T S

et al. 1999), this is one of the most complete Weichselian loess sequenc­

es in western Europe

( G U L L E N T O P S

et al. 1998).

The present study focuses however on MIS-stages 5- 12.

Upper Saalian

TL-dating of the " B - l o e s s " sequence, containing the characteristic tundrasols beneath the (part of the) Rocourt pedocomplex with related Rocourt tephra, did provide mean ages of 130-140 ka in the Nelissen pit "Kesselt"

( V A N D E N H A U T E

et al.

1998,

W I N T L E

in

V A N D E N H A U T E

et al. 1998). These ages are in accordance with mean TL-dating re­

sults of around 140 ka from several loess sections in middle Germany, containing tundrasols of the

" B r u c h k ö b e l e r N a s s b o d e n - K o m p l e x " present beneath a redbrown interglacial paleosol

( Z Ö L L E R

in

F R E C H E N

1991). A t the archeological site Maas­

tricht-Belvedere, T L - d a t i n g of the first eolian loesses, present above Caberg-3 floodloams and influenced by soil-formation processes of the last interglacial, gives a m e a n minimum age of 115 ka

( D E B E N H A M

1993). In fact, these results clearly demonstrate that the " B - l o e s s " , containing the characteristic tundrasols and showing green am­

phibole percentages from 20-5%, perfectly fits into MIS-6 (Fig. 7).

However, loesses deposited during the period of strong overlandflow and gully-formation, just be­

fore the onset of the last interglacial period (see Nelissen pit "Kesselt", Fig. 6) yielded TL-ages of 50-60 ka

( V A N D E N H A U T E

1998,

W I N T L E

in

V A N D E N H A U T E

1998). On the base of these TL-ages

V A N D E N H A U T E

et al. ( 1 9 9 8 ) a n d

M E I J S &

G R O E N E N D I J K

(1999) assumed an important ero­

sion hiatus between the guUy-filling and underly­

ing tundrasol-sequence N 1 - N 5 . In contrary to

J U V I G N E

et al. (1996),

V A N D E N B E R G H E

et al. (1998) did not correlate the interglacial-like paleosol to the Rocourt pedocomplex (MIS-5). On the base of numerous

^{1 4}

C - dates of the N 1 - N 5 tundrasols (30-37 ka) and the above mentioned TL-results of 50-60 ka they proposed for correlation with MIS-3 and assigned it as the Lafelt soil.

According to new chronological data from a sim­

ilar sequence at the archeological site Veldwezelt- Hezerwater, it seems reasonable to accept the cor­

relation with MIS-5 after

J U V I G N E

et al. (1996). A thorough study is prepared on this subject in co­

operation with the universities of Gent (Belgium) and Amsterdam (The Netherlands). T h e chrono­

logical results from the archeological site Veld- wezelt-Hezerwater will be published in a later pa­

per.

Middle Saalian

TL-dating done on burnt flints and calcareous tufa

and ESR-dating of molluscs, all found in relation

to interglacial soil-formation on top of the Ca-

126 ERIK P. M . MEIJS

Fig. 7: Chronostratigraphical framework constructed by correlation o f l o e s s , river terrace, pollen, dust and m a r i n e / i c e i s o t o p e s e q u e n c e s , o n the base of lithological and paleopedological characteristics and mineralogical a n d chronological data. T h e dust and t e m p e r a t u r e records are a d o p t e d from PETIT et al.(1999), while the pollen and i c e - v o l u m e sequences are a c q u i r e d from REILLK et al. (1998) and BASSINOT et al. (1994).

For l e g e n d see Fig. 2.

Fig. 7: Chronostratigraphische Übersicht, entwickelt auf der Basis von D a t e n zur L ö s s s e d i m e n t a ü o n , Bildung v o n F l u s s t e r r a s ­ sen, Staubabfolge, Pollenanalytik, Mineralogie u n d Chronologie. S t a u b - u n d T e m p e r a t u r d a t e n n a c h PETIT et al. ( 1 9 9 9 ) , Pollen­

daten u n d D a t e n z u m E i s v o l u m e n nach REILLE et al. (1998) und BASSINOT et al. (1994). L e g e n d e siehe Abb. 2.

Loess stratigraphy in D u t c h and Belgian Limburg 127

b e r g - 3 floodloams, s h o w average ages ranging from 2 2 0 ka (ESR) to 2 5 0 ka (TL; with a mini­

m u m age of

1 7 5

ka for molluscs:

V A N K O L F S C H O -

T E N et al. 1 9 9 3 ) . According to m e a n TL-data of around 2 4 5 ka for Middle Saalian loess sequences m m i d d l e Germany, present beneath two intergla­

cial paleosols

( Z Ö L L E R

et al.

1 9 8 8 )1

and the above- indicated data for the archeological site Maastricht- Belvedere, it seems m o s t logical to assign the grav­

el-aggradation phase of the C a b e r g - 3 terrace lev­

el and the " C - l o e s s " with green amphibole per­

centages ranging from 1 - 3 % , to M J S - 8 (Fig. 7 , see also

V A N K O L F S C H O T E N

et al.

1 9 9 3 ) .

This implies that the Hees soil m a t c h e s with M J S - 7 a n d the Montenaken soil with MTS-9.

L o w e r Saalian

For correlating the Weichselian a n d Saalian river terraces with the m a n n e / i c e isotopic records and the terrestnal pollen sequences, only two convinc­

ing reference points are present: the Maasmeche- len terrace (first p r e s e n c e of R o c o u r t tephra;

P A U L I S S E N 1 9 7 3 )

and the Caberg-3 terrace (ESR and T L darings; see above). In d o w n w a r d direc­

tion only the Pietersberg-2 ( 8 0 0 k a ) , Geertruid-2 ( 1 . 1 m a ) and Simpelveld-1 ( 2 . 1 m a ) terrace levels form important fixing points by their paleomag- netical polanty a n d / o r pollen content (VAN D E N

B E R G 1 9 9 6 ) .

Recent studies by

F E L D E R & B O S C H ( 1 9 8 8 , 1 9 8 9 ) , J U V I G N E & R E N A R D ( 1 9 9 2 ) and V A N D E N B E R G ( 1 9 9 6 )

reported no further chronostrati­

graphical data that can support m o r e detailed cor­

relation. On the base of these fixing points and climo-tectomc modelling studies

V A N D E N B E R G

( 1 9 9 6 ) found a correlation between the five lower river terraces of the Maas and the glacial manne isotopic stages 2 / 4 , 6 , 8 , 1 0 and 1 2 , denoting that only long-lasting full glacial stages generate major river terrace systems (see Fig. 7 ) . According to u r a n i u m senes dating and biostratigraphical re­

search

M E I J E R A N D P R E E C E ( 2 0 0 0 )

discovered ex­

actly the same situation for the l o w e r terrace se­

quence of the nver T h a m e s in England. On the base of these two studies the strongly developed, reddish Pottenberg soil, which has been found in m a n y sections along the widened A l b e r t Canal on top of the R o t h e m - 1 , Rothem-2 a n d Caberg-1 floodloams, should be attnbuted to MTS-11. Re­

cent chronometncal andpollen-stratigraphical re­

search on lacustnne dnlling cores in France, Italy and Greece and alluvial sediments in England, re­

veals strong evidence for assigning M I S - 1 1 to the Holsteiman p e n o d

( T Z E D A K I S

et al.

1 9 9 7 , R E I L L E

et al.

1 9 9 8

and

M E I J E R A N D P R E E C E 2 0 0 0 ) .

In plac­

es the Pottenberg soil is underlain by a redbrown luvisol (Dousberg soil), which represents the warm period (MIS-13) between the formation of the Rothem-2 and Caberg-1 river terraces (VAN D E N

B E R G

1996).

T h i s implies that the " D - l o e s s " correlates with J M J S - I O and that the Pottenberg soil and Wolder soil are equivalent to respectively MIS-11.3 and MIS-11.1 (Fig. 7 ) .

Conclusions

T h o r o u g h lithological, m i n e r a l o g i c a l and pale- opedological examinations of numerous loess sec­

tions in the study area, the application of recent chronological data and extended correlation with loess sections in middle Germany, m a d e it possi­

ble to construct a reliable loess-stratigraphical framework, which begins with the Holsteinian and matches with the manne/ice isotopic and terres­

tnal pollen records. It contains four glacial loess cycles with five intercalated interglacial paleosols on top of the R o t h e m nver terrace of the Maas.

A c k n o w l e d g e m e n t s

I wish to thank A.

G R O E N E N D I J K

for his full coop­

eration in the exhausting leveling and drawing ses­

sions of the n u m e r o u s loess sections in the field.

He was very helpfull in discussing and lnterpre- tating the recorded data.

Prof. P.

V A N D E N H A U T E ,

Prof. J.

V A N D E N B E R G H E

and Prof. E.

( U V I G N E

are thanked for providing constructive comments on the manuscript.

Appreciation g o e s out to prof. F.

G U L L E N T O P S ,

A.

G R O E N E N D I J K

a n d J-P.

D E W A R R I M O N T

for their positive cnticism and discussions in the field.

Great thanks are also due to W

F E L D E R

and P.

B O S C H

who supplied data from both sides of the

widened Albert Canal, which w a s of emense val­

ue for this study.

Appreciation is extended to H.

V A N N I E U W E N B O R G

of the company of Geolab for supplying dnllmg- data from the potential loess-exploitation zone between Kesselt and Lafelt.

S H A W N B U B E L , F R E D E R I C C L A S S O N and E L K E S C H L E - P Ü T Z

were so kind to correct the English text.

128 ERIK P. M . MEIJS

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1

According to recent knowledge, these TL-ages from

Ariendorf, Middle Rbine Valley, must be regarded as

underestimated, however (personal cornmunication by

L. ZÖLLER). This further strengthens the assignment of

C-loess to MIS-8.