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Sedimentary Descriptions of Stratigraphic Cuts
Extensively based on field observations recorded
by Luc Braillard.
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Cut 1 (Y-Z/4 and
A-C/4, Fig.
37
: 1)
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Unit
Modern debris
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Granulometry: silt, sandy and slightly clayey |
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Interpretation: modern (>1998). |
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Unit
R1
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Granulometry: silt, clayey. |
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Color:
brown. |
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Compaction:
compact. |
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Inclusions:
- humic content;
- small lumps of disturbed organic
layer. |
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Limits:
abrupt (0-2 cm). |
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Interpretation: part of the filling of anthropic origin between outer wall and
central platform. |
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Unit
R2
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Heterogeneous
layer made from a), b), and c) fractions. |
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Granulometry: a) silts, clayey; b) silts; c) silt, clayey, humic. |
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Color:
a) yellow; b) orange, centimetric sizes (1-2 cm); c) dark
brown. |
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Compaction:
strong compaction. |
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Limits:
abrupt (0-2 cm). |
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Interpretation: a) lumps disturbed from Unit 4 mixed in the filling of the
earthen mound; b) pieces,
disturbed, mixed in the filling of the earthen mound;
c) small lumps from the humic horizon that was the upper
deposit prior to the edification of the structure B3. |
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Links:
b) orange inclusions in Cut 2. |
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Unit
R3
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Heterogeneous
layer made from R1 and R2 fractions. |
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Granulometry: silts, clayey. |
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Color:
brown, yellow. |
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Compaction:
strong compaction. |
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Structure:
intimate heterogeneous mix. |
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Limits:
abrupt (0-2 cm). |
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Interpretation: earthen mound fill. |
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Unit
4
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Granulometry: a) upper part (only in squares B-C/4: Silts, clayey; b) lower
part: “Fragipan” horizon with frost polygons. Mica-silts. |
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Color:
a) yellow; b) brown, gray, yellow. |
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Compaction:
a) strong compaction; b)
very strong compaction. |
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Inclusions:
charcoal, Fe/Mn precipitates. |
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Limits:
abrupt (0-2 cm), erosive upper limit. |
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Interpretation: local horizon that was partly dug, as well as the layer lying above
it, prior to the building of B3. |
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Links:
unit 4 in Profile 2. |
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Remarks
about the frost polygons in su4:
A
ferric border of orange color surrounds the polygons. They are
constituted of mica-silts, brown, gray and yellow in color, very
compacted, with brown spots of Fe and Mn. The frost cracks are
filled with yellow clayey silts, less compact (same as top of
Unit 4. Charcoal fragments are present throughout the Unit 4.
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Cut 2 (V-Y/3; Fig.
37
: 2)
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Unit
2.1
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Granulometry:
silt, slightly clayey (>95%)
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Color:
brown yellowish (orange).
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Inclusions:
few angular and rounded crystalline gravels Qc5%).
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Compaction:
strong compaction on the 20 cm on top, due to machines.
Weak compaction below. |
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Structure:
lumpy with quite high porosity, breaky.
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Inclusions:
- scarce charcoal splinters and rare charcoal fragments;
- orange dots are hardened silts (understood as burnt; cf.
field notes, 18.04.2000) and represent ca. 5%. They are
disturbed (secondary position).
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Interpretation:
humic colluvial deposit, probably deposited rapidly
following a deforestation of the above slopes. Most elements are
in disturbed, secondary position.
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Links:
unit 2.1 in cut 3.
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Unit
2.2
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Granulometry:
silt, slightly clayey.
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Color:
brown black (orange) and dark brown.
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Inclusions:
some angular crystalline gravel (flat micaschist
fragments) disposed along the layer slope.
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Compaction:
very weak compaction.
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Structure:
lumpy and breaky.
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Inclusions:
- orange dots are hardened silts (understood as
burnt; cf. field notes, 18.04.2000) and represent ca. 2%. They
are disturbed (secondary position); - few dark brown clayey
silt pieces (understood as disturbed organic layer fragments; - scarce
presence of preserved vegetal fibers.
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Limits:
upper limit very clear to the West, gradual to the East
(5-15 cm). The crystalline elements (collapsed elements and
standing remains) are included in this layer, which implies a
contemporary deposit. The lower limit (mV3) is irregularly
abrupt, probably bioturbed (no anthropic digging at this
location).
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Interpretation:
very humic horizon with a partly preserved vegetal
fraction. This layer proceeds certainly from the earthen mound,
by washing activities. It started to form once the vegetation
installed on the earthen mound, as well as during the
dismantling (naturally by erosion or by an earthquake during the
17th century? or anthropically by recuperation or
volunteer destruction?) of the outer wall from which the
elements are included in this layer. This layer is absent at 9.5
m to the East (cf. Profile 4).
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Chronological
remarks:
This layer is relatively thick compared to the time of
deposition. We think the structure B3 was built in ca.
1550-1600. The earthen mound was then soon colonized by
vegetation. Unit 2.2 began its formation around ca. 1650 (?).
The structure could have been partly dismantled by ca. 1900, as
well as Unit 2.1 was then deposited. Deforesting occurred.
Reforesting could have taken place around 1950-1960, and
concomitantly the vegetation context was stabilized. All those
sedimentary processes would have taken no longer than 300 years;
this is possible, although apparently quite short.
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Unit
4
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Granulometry:
silt.
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Color:
yellow.
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Compaction:
strong compaction.
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Limits:
upper limit is naturally erosive, with later slight
bioturbation during the deposit of Unit 2.2. |
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Interpretation:
see Unit 4 in Profile 1.
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Links:
unit 4 in Profile 1.
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Cut 3 (13.2
meters north of G/1; Fig.
37
: 3)
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Unit
1
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Definition:
small organic litter. |
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Granulometry: silt. |
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Color:
dark brown, black |
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Inclusions:
numerous roots and preserved vegetal fibers (1-2 cm). |
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Interpretation: modern. |
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Unit
2
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Granulometry: silt, slightly clayey, some angular crystalline gravels. |
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Color:
dark brown, humic. |
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Structure:
loose, lumpy, little compaction. |
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Inclusions:
orange silt lumps. |
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Limits:
lower abrupt erosive limit. |
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Interpretation: slope colluvial deposit, formed by washing during a period with poor
forest cover. |
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Links:
perfectly identical to Unit 2 in B3.00.Profile 2. |
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Unit
4
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For
a general description, see su4 in Cut 1 (above). |
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Unit
4.2.1
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Granulometry: silts, clayey. |
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Color:
gray, brown, yellow. |
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Compaction:
strong compaction. |
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Limits:
upper abrupt erosive limit;
lower progressive limit |
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Structure:
presence of superposed vertical cracks interpreted as
frost polygons and presence of clay intrusions interpreted as Bt
horizon. It is difficult to say which phenomenon is anterior to
the other. |
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Links:
- probably corresponding with Unit 4.2.1 in
B5-6.00.Profile 1; - similar
to su4 in Cut 1 and Cut 2. |
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Unit
4.2.3
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Granulometry: see B5-6.00.Cut 1. |
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Color:
see B5-6.00.Cut 1. |
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Compaction:
see B5-6.00.Cut 1. |
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Structure:
the polygons are individualized by clay flanking and are
small in size (4-15 cm). |
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Limits:
upper loose limit; bottom
not reached. |
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Interpretation: Bt horizon. |
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Links:
see B5-6.00.Cut 1.Unit 4.2.3. |
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Cut 4 (9.5 meters
southeast of W/3; Fig.
37
: 4)
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Unit
1
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Definition:
small organic litter. |
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Granulometry: silt. |
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Color:
very dark brown. |
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Structure:
lumpy, breaky, porous. |
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Inclusions:
numerous roots and preserved vegetal fibers (1-2 cm). |
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Interpretation: actual soil. |
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Unit
2.1
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Granulometry: silt, slightly clayey. |
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Color:
brown, yellowish, humic. |
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Structure:
loose, lumpy, little compaction. |
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Inclusions:
orange silt lumps. |
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Limits:
lower loose limit. |
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Interpretation: colluvial deposit. |
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Links:
identical to Cut 2, unit 2.1. |
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Unit
2.2
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Absent
in this profile. |
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Unit
2.3
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Granulometry: silts, clayey. |
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Color:
brown, humic. |
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Compaction:
strong compaction, massive structure. |
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Inclusions:
- scarce and angular crystalline gravel;
- some charcoal
splinters. |
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Limits:
upper loose limit; |
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Structure:
massive. |
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Interpretation: old humic colluvial deposit, probably much older than Unit 2.1. |
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Links:
similar to B3.00.Profile 1.Unit R1. |
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Unit
4
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Granulometry: silts, clayey. |
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Color:
brown, gray, yellow. |
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Compaction:
very strong compaction. |
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Inclusions:
charcoal, Fe/Mn precipitates. |
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Limits:
upper abrupt erosive limit with later light bioturbation. |
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Interpretation: Bt horizon. |
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Links:
unit 4 in Cut 2. |
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Cut
5 (V/3-8; Fig.
37
: 5)
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Unit
Modern Debris
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Definition:
debris accumulated during terracing work in 1998.
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Granulometry:
heterogeneous mix.
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Color:
variable.
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Inclusions:
variable.
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Interpretation:
modern (1998).
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Unit
1
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Granulometry:
- 0.5 cm of preserved vegetal remains;
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Color:
- black vegetal remains;
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Structure:
loose, lumpy, very little compaction.
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Inclusions:
preserved vegetal remains.
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Interpretation:
upper horizon of actual soil, very little pedologic
evolution.
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Unit
2.1
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Definition:
recent humic colluvial deposit.
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Description:
same description as Cut 2, unit 2.1.
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Unit
2.2
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Definition:
very humic horizon resulting from washing of the earthen
mound.
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Description:
same description as Cut 2, unit 2.2.
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Limits:
upper limit is gradual to the Northeast and clear abrupt
to the Southwest. Like this feature, the humicity increases
toward the Southwest, as well as the color becoming darker.
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Unit
4
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Definition:
very compact yellow silts.
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Description:
same as Cut 2, unit 4.
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Cut
6 (Z/6-10; Fig.
38
: 6)
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Unit
1
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Description:
identical to Cut 5, unit 1.
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Unit
R1
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Description:
identical to Cut 1, unit R1.
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Unit
R3
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Description:
identical to Cut 1, unit R3.
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Cut
7 (J-K/4-8; Fig.
38
: 7)
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Unit
1
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Description:
identical to Cut 5, unit 1.
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Unit
R1
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Description:
identical to Cut 1, unit R1.
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Unit
R3
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Description:
identical to Cut 1, unit R3.
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Cut
8 (J-N/0; Fig.
38
: 8)
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Unit
2.1
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Granulometry: silt, slightly clayey. |
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Color:
brown, yellowish, humic. |
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Structure:
loose, lumpy, little compaction. |
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Inclusions:
orange silt lumps. |
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Limits:
lower loose limit. |
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Interpretation: colluvial deposit. |
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Links:
identical to Cut 2, unit 2.1. |
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Unit
2.2
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Granulometry: silt, slightly clayey. |
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Color:
brown, grayish, humic. |
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Description:
identical to Cut 2, unit 2.2. |
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Unit
4.1
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Description:
identical to Cut 2, unit 4, but with inclusion of a few
structural stones. |
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Unit
4.2
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Description:
identical to Cut 3, unit 4.2.3. |
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