Maas / Meuse: some geology

PART 1   MAAS / MEUSE


Geology : Maas/ Meuse gravels.

 Short descriptions

 The quaternary geology of the region between Liege, Maastricht and Aachen is dominated by two major facts: fluvial depositions and eolian sand/ loess covers.  This article, is about the the Maas/ Meuse gravels, deposed during almost 2 million years.

 The Maas /Meuse river (1) , about 2 million years ago was  looking like a wide braided river, changing it' s coarse often. On the highest elevations in the area, around Vaalserberg ( near  Aachen), above + 250 - 300 m. a.s.l., we find rounded pebbles ( < 5 -15 > cm cross-cut) originating  from deposits of an earlier Miocene-Pliocene river, already flowing in a northern direction ( see image below: river pebbles from the Pliocene/ Miocene Maas/ Meuse river, consisting of flint from the upper cretaceous in Belgium) .We cannot trace the direction of this former river, as the river itself has cleared all traces afterwards. The old, late Pliocene Maas/ euse river, followed a direction to the north- east, forming a Rhine- Meuse delta that started north of Aachen..

Pebbles from the pre- Maas / Meuse, found at the Vaalserberg (NL/D) at an altitude of + 290  m. a.s.l. , pointing at the tertiary period the pre- river flew directly over the region - the Eupen -region of the Hohe Venn (Hautes Fagnes)at same altitude connected with the Aachener Wald.

The river definitely changed it 's  coarse from east to west ca. 1,2 mya ago, due to uplift of the eastern part of Southern Limburg. In all these periods the Maas/ Meuse river deposed large amounts of gravels in changing sizes and changing compositions (2). Before the so called Toul- captation ( about 350.000 BP) the Maas/Meuse river transported gravels from both the Ardennes (B) and the Vosges (F),the last 350.000 years only gravels from the Ardennes were transported.

During the Cromerian period (ca 860.000 - 480.000BP) large amounts of gravels were deposed in the Belgian Kempen area, forming a large fan- area. In the pit of S.B.S at Maasmechelen we can imagine the hughe gravel-deposits during glacial conditions.



(Image above:) Gravel deposits change in composition and sediment types during different periods ( e.g. more quartz in the older depositions) and several horizons show typical gravel depositions, even artifact -carrying gravel horizons can be detected by the type of pebbles in the horizons.(Picture: S.B.S. pit Maasmechelen (B))vertical differentiation in mineralogy of the different weathering profiles indicate  a stage -by- stage alteration of primary deposed rock minerals during changing environmental conditions.




(Image above:) Small geological  insight  of the Pleistocene Maas/Meuse  river at Bemelen  (NL).Top horizons show eroded loess, leached loess and gravel layers. The direction ( southeast -  northwest) of the pebbles during deposition in the early Pleistocene is suggesting the Maas river made a large bend towards the east, ( eroding bank) , leaving the city of Maastricht at the depositional riverside.
Notice the difference with the image of the S.B. S. pit, showing the Kempen area is a building up of a fan plateau.



(Image above :) During the formation of the river terrace heavy weathering took place, causing heavily cemented integrated layers. Gravel horizons are different in composition (size, origin of pebbles), and deposition patterns; in this way gravel containing horizons where possible artifacts may occur can be traced. (Picture taken at Bemelen NL).



Red oxidation layers were build up and integrated into other horizons during moderate interglacials, with more humidity and higher temperatures than today. In the image above, a Manganese dioxide layer is visible in black, based on the same type of chemical reactions during interglacial periods., but [laced in an earlier stage of the change of minerals compared with Fe2+/ Fe 3+. The stagnating clay layers  directly underneath ( grey layers in the image) deliver minerals ( such as Ca2+) for the chemical reactions, where the Manganese layers are formed, during changing water-levels ( clay mineral particles moving upward in the profile).  In the upper part of the stratigraphy red oxidation horizons are visible. (Image from the S.B.S. pit, Maasmechelen, Belgium).








Upper stratigraphy of the Belgian Kempen plateau (S.B.S. pit Maasmechelen).

 (Compilation of two images)







Image above: abrupt change in oxidation gradients in the horizons of gravel depositions of the Maas/ Meuse river, visible in a vertical stratigraphy. This would indicate exposure levels and water-levels during Middle -Pleistocene conditions.


Horizontal view of a coarse sand- gravel deposition of the Pleistocene Maas/ Meuse river. Rounded and sub-angular gravels are mixed with coarse sands, mostly of a dark yellow color, often remixed with loam. These reworked gravel-type often contains  dark flint ( dark grey, black) sometimes used for tool production in early Paleolithic periods. (Image Maas /Meuse -upper terrace at Opoeteren, Belgium)


During glacial periods of the Cromerian (ca. 800.000 - 550.000 BP), the Maas / Meuse river transported very large "ice rafted blocks", of more than 1000 kgs.  Such blocks can be found in the Kempen area, most of the times the biggest part invisible in the ground. Here the blocks from the SIBELCO pit at Maasmechelen are placed along a cycle-path. Image taken at Maasmechelen, SIBELCO pit.



(Image above) One of the blocks, transported during the glacial periods appears to be a very large Conglomerate stone, transported from the Ardennes. The age of these Conglomerate stones is Devonian ( 420- 350 mya). Image taken at Maasmechelen, SIBELCO pit.



It is quite well visible there is an abundance of stones, blocks  and pebbles from the Maas/ Meuse rivers in the Kempen: a wall  filled up with selected, average sized blocks from the glacial depositions is visible here at the entrance of the SIBELCO pit, Maasmechelen,  


(Image above) Small granulated gravel from the Maas/Meuse river ( + 80 - 90 m): sub-angular gravels (mainly quartzite and quartz)  mixed with eolian sands + ersoion).


(Image above) The Kikbeekgroeve near Opgrimbie (B) now is given back to nature. Still, we can see soil profiles on the west and south walls of the former pit.


Eolian depositions near the Maas/ Meuse river



The eolian depositions in the region are mainly divided into two types: sands and loess.



These eolian depositions originate the glacial periods , mainly the Saalian period. The sand covers are found in the northern part of the region, the loess is found south of Sittard (NL). The sand and loess originating from the dry North sea basin during the glacial, was blown mainly to a southeast- east direction. The smaller loess particles arrived in the farther away areas. It is assumed, that at least a part of the loess in Dutch southern Limburg comes from the dry riverbed and floodplain of the Meuse river.



Sand dunes on the eastern, very steep plateau -edge (sloping up to 25 m)  of the Belgian Kempen Plateau, running over the  edge like a "falling dune". These sands were blown here original from coastal areas (the dry North sea bassin) during glacial conditions of the Saalian. The dunes cover the earlier gravel depositions of the Maas/ Meuse river. In the back we see the community of Maasmechelen( Mechelen a/d/ Maas).


At the Brunsummerheide, in the eastern part of South Limburg ( near Brunssum and Landgraaf -Abdissenbosch) we find the gravels, deposed  by the old river Meuse, some 1,5 million years ago. This gravel deposition consists mainly of quartz pebbles, that often are bleached by the sand and exposure to sunlight.

 The spring of the Roode Beek is formed by a typical pool and many small springs  with very clear , purified water, from the sandy areas, right on a loamlayer, left by the pleistocene Maas river, over 1,5 million years ago. 
This is how we must imagine the old springs on the Kempen plateau in Belgium, when first humans arrived here. Now,  springs like these are gone in the Kempen region.
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NOTES
(1) The Maas (= NL) Meuse (= F) river is a Late Pliocene -Pleistocene river that flew from (melting) sources in the French Vosges mountain area to the north and followed a more east course, thus forming a common delta with the river Rhine. The Maas /Meuse debouched in the Rhine river north of the German city of Aachen.

Because of uplift of the eastern part of ( Dutch) Southern Limburg, the river followed a more west direction, until finally between 1 million years and 800.000 years ago the river cut itself into the present valley, visible between Maastricht (NL) and Liege (B).

The Belgian Kempen area remained a  to the west  inclined plateau, receiving millions of tons of gravels, known as the Kempen fan gravels , thus building up the plateau.

(2) We distinguish several types of gravels in the depositions. The younger depositions show  a decreasing number of quartz. During different periods, especially the glacial periods high energy transport of the river caused the presence of sub-angular gravels in the flow. In other periods, coarse sands containing small gravels were deposed. During interglacial circumstances, no gravels were deposed, but the river build clay layers and in the Kempen area loam lenses.




                        



                              





























2 comments:

  1. Hi,

    I’m a fossil collector too. Can you tell me, where you found the belemnites in Aachen? I never came across one in years?

    Best wishes Oliver

    ReplyDelete
    Replies
    1. Fossiles of belemnites in Aachen occur in the cretaceous parts of the area of the Schneeberg/ Wachtelkopf, in older horizons of the Roebelsbos near Slenaken.

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