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CN2b

Material name: CN2b
Synonyms: Silex Crétacé supérieur Nord - Sénonien (Campanien)
Material (geologic): Campanian (Senonian, Late Cretaceous) flint

Detail of Senonian CN2b flint
Foto: Jehanne Féblot-Augustins, 2005.

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Material description

Mode of occurrence: Small irregular nodules or pebbles.
Cortex: Can be pale tan, worn and thin, smooth to moderately rough, or cream-coloured, smooth and partially rolled with traces of impact; transition always sharp.
Colour: Light to dark olive grey (5Y 4.4/2 to 3.5/2), to light brownish grey (2.5Y 6.5/2).
Pattern: Flecked/spotted (unreplaced matrix and concentrations of micritized elements).
Appearance: Homogeneous material with a medium lustre, semi-opaque to subtranslucent in thin flakes, smooth and medium to fine-grained.
Structure: Some samples display a fluidal arrangement of grains.
Texture: Mudstone/wackestone.
Matrix: Opaque.
Grains: 10 to 15 %, very small pale rounded elements (40-80 µ), skeletal grains with high sphericity contained between 150 and 300 µ.
Grain composition: Fewer thin-walled sponge spicules than in CN2a (occasionally preserved lattice), benthic foraminifera (Nodosarianidea, a complete 3 mm long Nodosaria sp., Lenticulinea), discrete Nodosaria chambers (200-250 µ), numerous globose planktonic foraminifera (e.g. Hedbergella planispira), rare small biserial foraminifera (Heterohelicidae), pollen fragments, a tube-shaped organism.
Further information: Click here for the original French description (opens in a new window), or here for more information on the attributes used in the description (use your browser's "BACK"-button to return here).
Citing: Information on citing this page can be found here.


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Le Devin
Locality: Leyssard / Le Devin, France, Ain department
Synonyms: Sampling site Bugey 56 after Féblot-Augustins
Geographical description: The sampling site is located just above some hairpin-bends in the narrow road which connects the village of Leyssard with the main road D  979. Nearby there also is a path which goes from the mentioned hairpin-bends in the direction of Sonthonnax-le-Vignoble to the west.
Geographical co-ordinates: east/x 842.37
north/y 2134
(Lambert zone II, NTF)

This corresponds roughly with
Lat. 46° 09' 45.4" N
Long. 005° 28' 32" E
(WGS84)

Co-ordinate precision: As with most sites in this section on the Bugey, the French Lambert-values were taken off a large-scale topographical map and the geographical coordinates were calculated directly by transforming those values on WGS84. The precision of both are within 50 metres.

The location can be found on the 1:25 000 topographical map sheet 3229 W of the French Institut Géographique National.

Geology: According to the geological map, the substrate consists of clays-with-flints (Rs), which are the residues of dissolved/decalcified Late Cretaceous formations (C6).

Map of all sampled localities of Late Cretaceous flint in the Bugey (PDF, 54 KB, opens in new window).

Type of source: Secondary.
Other types of flint: The residual loams on this location contain also CN1a and CN1b flint.
  Freshly split piece of CN2b flint
Foto: Jehanne Féblot-Augustins, 2005
 
Patinated flake with recent damage
Foto: Jehanne Féblot-Augustins, 2005
 


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Meillarenche
Locality: Leyssard / Solomiat - Meillarenche, France, Ain department
Synonyms: Sampling site Bugey 57 after Féblot-Augustins
Geographical description: The sample was collected along the small road which connects Solomiat with the main D 979 road, some 350 metres to the southwest of the village.
Geographical co-ordinates: east/x 842.37
north/y 2134
(Lambert zone II, NTF)

This corresponds with
Lat. 46° 10' 31" N
Long. 005° 28' 31" E
(WGS84)

Co-ordinate precision: The Lambert reference given was taken from a large-scale map, and are within approx. 50 metres of the actual spot.
The latitude/longitude coordinates are a direct transformation of these data on WGS84 and are accurate to the same level, so don't be deceived by the apparently high precision to the second.

The location can be found on the 1:25 000 topographical map sheet 3229 W of the French Institut Géographique National.

Geology: According to the geological map, the substrate belongs to unit Rs, which represents clays-with-flints, in this case presumably the residual of unit C6 (Late Cretaceous, Senonian) limestones.

Map of all sampled localities of Late Cretaceous flint in the Bugey (PDF, 54 KB, opens in new window).

Type of source: Secondary.
Other types of flint: Besides the CN2b material, flints of the CN4c and CN5 type (both of similar age) might be found here.
  Worn nodule of Upper Cretaceous flint
Foto: Jehanne Féblot-Augustins, 2005
 
 


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Solomiat-Le Petit Bois (secondary)
Locality: Leyssard / Solomiat - Le Petit Bois, France, Ain department
Synonyms: Sampling site Bugey 59 after Féblot-Augustins
Geographical description: The source is located just east of the small road which connects the hamlet of Solomiat with the D 979, the main road in the northern part of the Bugey, linking Bourg-en-Bresse with Bellegarde-sur-Valserine. Solomiat lies approx. 10 kilometres as the crow flies WNW of Nantua, on a terrace on left bank of the river Ain, some 360 metres above the bottom of the narrow valley.
Geographical co-ordinates: east/x 842.7
north/y 2135.3
(Lambert zone II, NTF)

This corresponds with
Lat. 46° 10' 27" N
Long. 005° 28' 50" E
(WGS84)

Co-ordinate precision: As usual with the sites from the Bugey, the French Lambert-values were taken off a large-scale topographical map and the geographical coordinates were calculated directly by transforming those values on WGS84. The precision of both are within approx. 50 metres.

The location can be found on the 1:25 000 topographical map sheet 3229 W of the French Institut Géographique National.

Geology: The flint is to be found in residual loams left after the decalcification of Late Cretaceous (Senonian) limestones, unit Rs on the geological map.

Map of all sampled localities of Late Cretaceous flint in the Bugey (PDF, 54 KB, opens in new window).

Type of source: Secondary.
Other types of flint: Apart from the CN2b-type, also two other flints of Senonian age can be found here, namely CN1a and CN4c.
  Weathered nodule of CN2b flint
Foto: Jehanne Féblot-Augustins, 2005
 
Freshly split nodule with thick, irregular cortex
Foto: Jehanne Féblot-Augustins, 2005
 


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La Bierle
Locality: Poncin / La Bierle, France, Ain department
Synonyms: Sampling site Bugey 62 after Féblot-Augustins
Geographical description: The material was collected on a south-facing slope overlooking the eastern "outskirts" of Poncin, 20 kilometres SE of Bourg-en-Bresse.
Geographical co-ordinates: east/x 838,3 – 838,6
north/y 2125,3 – 2125,5
(Lambert zone II, NTF)

This corresponds roughly with
Lat. 46° 05' 12" N
Long. 005° 25' 14" E
(WGS84)

Co-ordinate precision: With a surface of several hectare, the site is quite extended, so no bother about the precision of the coordinates
The latitude/longitude coordinates point somewhere to the centre of the area, so don't bother about the single seconds (in this area, 1 second of latitude is ca. 30 metres on the ground, a longitudinal second approx. 20 metres)

The location can be found on the 1:25 000 topographical map sheet 3229 W of the French Institut Géographique National.

Geology: The site is located on fluvio-glacial deposits from the Würm I and II stages (units agl a-b on the geological map), in contact with Aquitanian sediments (Early Miocene, unit ml). This results in a mix of Upper Cretaceous and Cenozoic flints being present at this site. The CN2b type can be dated to the Campanian.

Map of all sampled localities of Late Cretaceous flint in the Bugey (PDF, 54 KB, opens in new window).

Type of source: Secondary.
Other types of flint: As so often on secondary sites, quite a lot of other types of flint can be found here, mostly of Late Cretaceous age: CN4a, CN4b, CN4c, as well as the Cenozoic "silex lacustre" of the T1 type.
  Worn nodule with fresh flake-scar
Foto: Jehanne Féblot-Augustins, 2005
 
 


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Sous les côtes
Locality: Poncin / Sous les côtes (chemin), France, Ain department
Synonyms: Sampling site Bugey 63 after Féblot-Augustins.
Geographical description: The sample was collected at the foot of the hillside north of the road that connects Poncin with Leymiat, some 500 metres northwest of the latter village.
Geographical co-ordinates: east/x 838.8
north/y 2125.1
(Lambert zone II, NTF)

This corresponds roughly with
Lat. 46° 05' 02" N
Long. 005° 25' 30" E
(WGS84)

Co-ordinate precision: The coordinates given were taken from a detailed topographic map, and are within approx. 50 metres of the actual spot.
The latitude/longitude coordinates are a direct transformation of these data on WGS84 and are accurate to the same level, so don't be deceived by the apparently high precision to the second.

The location can be found on the 1:25 000 topographical map sheet 3229 W of the French Institut Géographique National.

Geology: Although the flint itself dates to the Late Cretaceous, it now lies in a secondary position, embedded in fluvio-glacial deposits from the Würm I and II stadials (unit "agl a-b" on the geological map of the region).

Map of all sampled localities of Late Cretaceous flint in the Bugey (PDF, 54 KB, opens in new window).

Type of source: Secondary.
Other types of flint: Besides CN2b flint, the CN2a variety can be found here too.
  Freshly split nodule of CN2b flint
Foto: Jehanne Féblot-Augustins, 2005
 
 

 

Last modified on:
November 25, 2005
Contents primarily by:
Jehanne Féblot-Augustins
Comments to: