From research carried, out on a section of the Levriere, concretions (granules, nodules, which were sometimes joined together) partly covering the river ”bottom” were observed. The authors propose to make besides a petrographic examination of the calcareous precipitations and to see if their origin is connected to a biological activity, or if it is purely a case of a physical-chemical precipitation. The hydrological background of the Levriere, a small river of the Normandy Vexin, is given and conditions of the formation of the concretions studied

Adolphe, J.P.

Rofe, G.

English

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FRESHWATER BIOLOGICAL ASSOCIATION 
FBA Translation (New Series) No. 167 
Title: Calcareous concretions in the Levriere (tributary 
of the Epte, secondary tributary of the Seine, 
Eure department) 
Author(s) ADOLPHE, J.-P. & ROFES, G. 
Reference: Bull.Ass.fr.Etud.Quaternaire (1973) No.2, 79-87 
Original language: French 
Date of publication of original: 1973 
Translator: A. Baker 
Date of publication of translation: 1986 
No. of pages of translation: 9 
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FBA TRANSLATION (NEW SERIES) NUMBER 167 
Calcareous concretions in the Levriere (tributary of the Epte, secondary 
tributary of the Seine, Eure department). 
ADOLPHE, J.-P. and ROFES, G. 1973 
Bull. Ass. fr. Etud. Quaternaire (1973) No. 2, 79-87 
Translated by: A. Baker 
Introduction 
From research carried, out on a section of the Levriere, we 
observed concretions (granules, nodules, which were sometimes joined 
together) partly covering the river "bottom. 
Such calcareous precipitations have already attracted the attention 
of many researchers [Bourcart, Borzi A. (1883), Butcher R.W. (1932), 
Couteaux M. ( 1969) , Cornet J. ( 1899) , Fremy P. (1926), Lohest M. ( 1899) , 
Forir H. (1904), Meunier S. ( 1899) , Symoens J.J. (1947 & 1967), Tilden J.E. 
(1897), Van Oye P. (1937), Wallner J. (1934)]. Their work has above all 
centred on the determination of the vegetation enclosed by the precipitations. 
We propose to make besides a petrographic examination 
of the calcareous precipitations and to see if their origin is connected 
to a biological activity, or if it is purely a case of a physical-chemical 
precipitation. 
- 2 -
Calcareous concretions in the Levriere 
1. Hydrological background 
The Levriere is a small river of the Normandy Vexin, which rises 
south east of the Bray country (at an altitude of 120 m) and which travels 
about 30 km before entering the Epte below Gisors. 
Its average flow is less than 1m3 s-1 and the average current velocity 
is about 0.30 m s-1 . The depth, which is variable, rarely reaches 1.50 m; 
the width of the river bed never exceeds 12m. 
The river flows over clay and flint for the length of its course, 
which explains the consistency of the bottom which is dominated by fine sand 
and fragments of flint and siliceous material where it is not mud. 
The section under discussion, about 2 km long, is limited upstream by 
a mill race. Below this obstacle the water flows swiftly for a hundred metres, 
then more slowly (with some meanders and widening of the bed). The bottom, 
pebbly near the mill race, shows finer and finer particles as one moves 
downstream until it forms sand and mud banks. The first calcareous concretions 
are seen at the level of the separation of the river into parallel channels 
lying NW-SW, a kilometre below the mill race (Fig. 1 ) . 
The course of the Levriere, at sites at the communities of Saint-Paer 
and Bezu-Saint-Eloi, has been the subject of consistent treatment, the 
scattering of powdered chalk (particles of several microns) with the aim of: 
1. Dissipating the mud; 
2. Following the evolution of the phenomenon; and 
3. Studying the action of chalk on mud. 
The treatment by chalk has created a change in the morphology of the river bed 
after a progressive cleaning of the mud banks: some of them, having completely 
disappeared, have given place to concretions, which is the subject of the 
present note. 
.2. Macroscopic and microscopic study of the concretions 
A Macroscopic study 
They occurred in the form of granules (the size is in the order of mm) 
or of nodules (in the order of cm), rather rounded, ovoid or cylindrical, 
forming a crust when they are joined together. 
Their natural colour is chestnut, but after a long time in the open 
air, the surface exposed to the light takes on a whitish or blue-mauve tint. 
Dissected, the concretions offer alternate light arid dark zones of different 
hardness (photo 1, sheet 2). Their density is low (wet density 2.0; dry 
density 1.^) and the current sweeps them along easily by rolling them 
and saltation. There appears to exist a connection between these movements 
and the size of the zones. 
- 3 -
In addition insect larvae (larvae of the Goeridae family, Silo) 
establish bridges between certain concretions, so that the forming of 
the concretion no longer appears around the granules and nodules, but 
only on the surface exposed to light. The concretion spreads out, making 
a crust which covers the whole. This phenomenon can occur over several 
square metres. 
B Microscopic study 
On a thin plate (sheet II, photo 1) the concretion appears very porous. 
The empty spaces represent light zones, while dark zones are joined up by 
shafts (sheet II, fig. 2). The shafts, like the dark zones, consist of 
crystals which are shown to be calcified partitions of algal filaments of a 
basically radiating orientation. The crystals (smaller than a micron) are 
arranged in rings or according to the orientation of a cylinder representing 
the filament, with a specific morphology for each type of alga. Their 
diameter is between 2 and 10 u. The concretion always begins with a dark 
zone and discontinues, anchored in a central matrix (fragments of silex, 
limestone, brick, charcoal, sheaths of insect larvae, sand etc.). The last 
dark area, little different from the earlier, suggests that the incrustation 
is produced at the same time as the algal activity. 
With the aid of M. Bourrelly, Professor at the Museum d'Histoire 
Naturelle de Paris, we have identified the following algae (previously 
isolated from the concretions using 10% hydrochloric acid): 
Stigonema (Cyanophyceae, unknown species). This alga lives in water 
or on wet rocks. Stygonemaceae are filamentous Cyanophyceae characterized 
by the formation of lateral branches following the evolution of a cell 
divided from the trichome lengthways. Propagation is effected by hormogones, 
hormocysts, spores, solitary gonidia or part of chroococcoidal masses. They 
live in thermal fresh water or are underground. Otherwise they are in the 
same family as Chamesiphonaceae or Rivulariaceae. 
Lyngbya calcarea (Tilden) Symoens (Cyanophyceae) 
L. martensensiana Menegh var. calcarea Tilden. The encrusted filaments 
have a diameter of about 7 microns, they are more or less straight. Trichomes 
are without constrictions at the septae and at their extremities have a 
diameter of 5.5 u to 6 u. The length of the cells is from 1.3 to 2-2.8 u , the 
anterior cell is rounded and there is no cap. This diagnosis was given by 
Tilden in 1897 and this alga was reported in different calcareous incrustations 
in North America and in the Tatras, the Namurous, the Somme, and the Herault in 
Europe. The sheath of this Cyanophyceae is firm. 
- 4 -
Gongrosira species (Chlorophyceae). This filamentous alga has a thallus 
strongly encrusted with limestone and the small branches are abundant. The 
width of filaments varies between 10 to 15 u, the small branches having a 
narrower diameter. The cells of the filaments are 13 to 18 u long but are 
12 to 21 u for terminal branches of the main axes. Gongrosira was found at 
Messina (Sicily) in 1883 and described by Borzi on the walls of an old 
aqueduct and only found again in Belgium in 1948 (incrustations on pebbles 
in a stream of the Hautmont wood). 
From the measurements taken, both from the concretions collected from 
cages left on the river bottom, and from those kept in running water in tanks 
in the laboratory, it appears that their growth is in the neighbourhood of 
1 mm a year (sheet III). At the time of this last experiment the debris of 
eruptive rocks (rhyolite, free of all calcium carbonate deposit) put in the 
running water flowing over the concretions, were covered again with carbonate domes 
1 mm large. These domes are a result of the development of air circulating 
round the colonising algae; their juxtaposition and the piling up of the 
successive colonies creates a rounded outer appearance of the concretion. 
The dark areas can be compared to the arches of a bridge and the pillars 
which connect them to the piles. The clear zones thus correspond to the 
spaces between the piles supporting the dark zones. The piles are the point 
of departure of the whole colony of which the greatest growth takes place in 
spring, summer and autumn. (Fig. 2, sheet II) 
Photo 3 (sheet II) taken with an electron microscope shows the different 
stages of the incrustation of the algae: it is made of material growing in the 
membrane of the filament, then progressively reaches the centre. It is also 
vertical and perhaps the crystal rings mark the stages of these deposits. It 
is probable that a precipitation takes place around the filaments, in the 
mucilage of the algae, explaining their occasional union. 
These first observations allow one to envisage that the accumulation 
of calcium carbonate is at the same time both intra- and extra- cellular. The 
studies are undertaken in order to make sure about the nature of the organelles 
of the cell which participate in the formation of the initial calcareous deposit. 
3. Conditions of the formation of the concretions 
The solution of calcium carbonate by CO2 is facilitated at the gravel 
surface by conditions of pressure in excess of atmospheric pressure. (....?....) 
The development of different concretions occurs following a process shown by 
the following equilibrium: 
[C03H]2 Ca < > CO3Ca + H20 + C02 
In addition, the rise in temperature and pH, associated with the 
encrusting activity of the algae, favours the precipitation of calcium 
carbonate in a very weak solution. (1 4 mg/l in water at 25° C) 
The analyses carried out during the field studies from January 1970 
to February 1971 corroborate the preceding remarks. In effect the main 
variations occur between the source and site 2 and between sites 4 and 5. 
Graphics 1-10 (sheet IV) show that: 
1. As soon as it emerges, the water at the stream bed surface is 
impoverished of CO2, bicarbonates, calcium, but enriched in 
oxygen (mixing of the water) and at the same time the water 
becomes more alkaline; 
2. Certain variables, such as pH and are stable going downstream 
(site 5): 
3. Bicarbonate, calcium, conductivity augment slightly at sites 3 & 
to reach a maximum at site 5, explained by the contribution of the 
Bonde river which emerges upstream of site 5 in the Levriere; 
4. The water temperature decreases while flowing downstream: it is 
subjected directly to the air temperature which is cold in winter; 
5. At the source, the rough water cleans the silex nodules present at 
the bottom of the arrival basin, making them completely clean and 
smooth to the touch. 
The first kind of concretions (granules) develop upstream of 
site 2 as far as site 5 (crusts) with a maximum thickness of 50 cm 
from site 4. 
6. The chemical analysis of the incrustations shows the following 
average content: 
- CO3Ca: 80% (in the form of calcite determined by the microscope 
polarising and by X rays); 
- CO3 Mg: 13% 
- organic matter: 5% (proportion by loss on combustion) 
- diverse (trapped grains of mud, clay, diatoms): 2% 
Among the parameters of the environment described above some react on 
the activity of algal colonies. One would say that incrustations are maximum 
in time and space, when the conditions of precipitation of calcium carbonate 
by biological means are favourable. Among the rest: 
1. Incrustations increase very little in winter, but very much in 
spring, summer and autumn (maximum photosynthesis); increasing 
2. Concretions like photosynthesis go on from site 2 to site 4 and 5 
in summer, parallel with the warming up of the water. 
- 6 -
The scattering of chalk has eliminated mud and brought to light the 
anterior concretions at the area of silting up, explaining the increase in 
the number of nodules in the section treated. It is certain that the 
artificial deposits of chalk are not at the origin of the concretions; on 
the one hand, they appear upstream of all chalk distribution and on the 
other, from site 2 the water course reaches a pH approaching a pH of 
saturation point. 
Conclusion 
The results of the microscopic studies of the concretions speak 
volumes; they are constituted solely of encrusted algal filaments, above all 
with calcium carbonate. This structure explains the physical properties of 
the incrustations (weak density and high porosity). 
Without departing from the possibility of a physico-chemical 
precipitation of calcium carbonate, from the presence of algae and above all 
from the study of its activity one should reach the conclusion that the 
precipitation, is essentially biological. Diverse experiments have allowed 
one to clarify the way algal colonies have developed and to establish a 
relatively precise measure of their growth. 
As borings in the original river bed and in the channels excavated 
in the last century have revealed several levels of concretions separated 
by mud banks, it is certain that the alternate concretions and mud are not 
a new phenomenon and that it occurred many times in former years. 
2. A. Plan of one arched colony 
B. Juxtaposition and. piling up of several colonies 
They show the external rounded aspect of the concretion 
3. Algal filament of the concretions (x = 1 100) 
1. Cross section of a concretion. It shows alternating 
light and dark zones of different hardness (x 6) 
7 
Measurements of the growth, of the concretions in the Levriere 
9 
Physico-chemistry of the water in the Levriere 
Fig 5. Profile of the river at the sites of previous deductions 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Notice 
 
 
Please note that these translations were produced to assist the scientific staff of the 
FBA (Freshwater Biological Association) in their research. These translations were 
done by scientific staff with relevant language skills and not by professional 
translators. 
 
 
 


Calcareous concretions in the Levriere (tributary of the Epte, secondary tributary of the Seine, Eure department) [Translation from: Bull.Ass.fr.Etud.Quaternaire 1973(2),  79-87, 1973]

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Calcareous concretions in the Levriere (tributary of the Epte, secondary tributary of the Seine, Eure department) [Translation from: Bull.Ass.fr.Etud.Quaternaire 1973(2), 79-87, 1973]

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