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Appendix 1: Sedimentary Descriptions

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Sedimentary Descriptions of Stratigraphic Cuts

Extensively based on field observations recorded by Luc Braillard.

Cut 1 (Y-Z/4 and A-C/4, Fig. 37 : 1)

Unit Modern debris

Granulometry: silt, sandy and slightly clayey

Interpretation: modern (>1998).

Unit R1

Granulometry: silt, clayey.

Color: brown.

Compaction: compact.

Inclusions: - humic content; - small lumps of disturbed organic layer.

Limits: abrupt (0-2 cm).

Interpretation: part of the filling of anthropic origin between outer wall and central platform.

Unit R2

Heterogeneous layer made from a), b), and c) fractions.

Granulometry: a) silts, clayey; b) silts; c) silt, clayey, humic.

Color: a) yellow; b) orange, centimetric sizes (1-2 cm); c) dark brown.

Compaction: strong compaction.

Limits: abrupt (0-2 cm).

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.

Links: b) orange inclusions in Cut 2.

Unit R3

Heterogeneous layer made from R1 and R2 fractions.

Granulometry: silts, clayey.

Color: brown, yellow.

Compaction: strong compaction.

Structure: intimate heterogeneous mix.

Limits: abrupt (0-2 cm).

Interpretation: earthen mound fill.

Unit 4

Granulometry: a) upper part (only in squares B-C/4: Silts, clayey; b) lower part: “Fragipan” horizon with frost polygons. Mica-silts.

Color: a) yellow; b) brown, gray, yellow.

Compaction: a) strong compaction; b) very strong compaction.

Inclusions: charcoal, Fe/Mn precipitates.

Limits: abrupt (0-2 cm), erosive upper limit.

Interpretation: local horizon that was partly dug, as well as the layer lying above it, prior to the building of B3.

Links: unit 4 in Profile 2.

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.

Cut 2 (V-Y/3; Fig. 37 : 2)

Unit 2.1

Granulometry: silt, slightly clayey (>95%)

Color: brown yellowish (orange).

Inclusions: few angular and rounded crystalline gravels Qc5%).

Compaction: strong compaction on the 20 cm on top, due to machines. Weak compaction below.

Structure: lumpy with quite high porosity, breaky.

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).

Interpretation: humic colluvial deposit, probably deposited rapidly following a deforestation of the above slopes. Most elements are in disturbed, secondary position.

Links: unit 2.1 in cut 3.

Unit 2.2

Granulometry: silt, slightly clayey.

Color: brown black (orange) and dark brown.

Inclusions: some angular crystalline gravel (flat micaschist fragments) disposed along the layer slope.

Compaction: very weak compaction.

Structure: lumpy and breaky.

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.

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).

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).

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.

Unit 4

Granulometry: silt.

Color: yellow.

Compaction: strong compaction.

Limits: upper limit is naturally erosive, with later slight bioturbation during the deposit of Unit 2.2.

Interpretation: see Unit 4 in Profile 1.

Links: unit 4 in Profile 1.

Cut 3 (13.2 meters north of G/1; Fig. 37 : 3)

Unit 1

Definition: small organic litter.

Granulometry: silt.

Color: dark brown, black

Inclusions: numerous roots and preserved vegetal fibers (1-2 cm).

Interpretation: modern.

Unit 2

Granulometry: silt, slightly clayey, some angular crystalline gravels.

Color: dark brown, humic.

Structure: loose, lumpy, little compaction.

Inclusions: orange silt lumps.

Limits: lower abrupt erosive limit.

Interpretation: slope colluvial deposit, formed by washing during a period with poor forest cover.

Links: perfectly identical to Unit 2 in B3.00.Profile 2.

Unit 4

For a general description, see su4 in Cut 1 (above).

Unit 4.2.1

Granulometry: silts, clayey.

Color: gray, brown, yellow.

Compaction: strong compaction.

Limits: upper abrupt erosive limit; lower progressive limit

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.

Links: - probably corresponding with Unit 4.2.1 in B5-6.00.Profile 1; - similar to su4 in Cut 1 and Cut 2.

Unit 4.2.3

Granulometry: see B5-6.00.Cut 1.

Color: see B5-6.00.Cut 1.

Compaction: see B5-6.00.Cut 1.

Structure: the polygons are individualized by clay flanking and are small in size (4-15 cm).

Limits: upper loose limit; bottom not reached.

Interpretation: Bt horizon.

Links: see B5-6.00.Cut 1.Unit 4.2.3.

Cut 4 (9.5 meters southeast of W/3; Fig. 37 : 4)

Unit 1

Definition: small organic litter.

Granulometry: silt.

Color: very dark brown.

Structure: lumpy, breaky, porous.

Inclusions: numerous roots and preserved vegetal fibers (1-2 cm).

Interpretation: actual soil.

Unit 2.1

Granulometry: silt, slightly clayey.

Color: brown, yellowish, humic.

Structure: loose, lumpy, little compaction.

Inclusions: orange silt lumps.

Limits: lower loose limit.

Interpretation: colluvial deposit.

Links: identical to Cut 2, unit 2.1.

Unit 2.2

Absent in this profile.

Unit 2.3

Granulometry: silts, clayey.

Color: brown, humic.

Compaction: strong compaction, massive structure.

Inclusions: - scarce and angular crystalline gravel; - some charcoal splinters.

Limits: upper loose limit;

Structure: massive.

Interpretation: old humic colluvial deposit, probably much older than Unit 2.1.

Links: similar to B3.00.Profile 1.Unit R1.

Unit 4

Granulometry: silts, clayey.

Color: brown, gray, yellow.

Compaction: very strong compaction.

Inclusions: charcoal, Fe/Mn precipitates.

Limits: upper abrupt erosive limit with later light bioturbation.

Interpretation: Bt horizon.

Links: unit 4 in Cut 2.

Cut 5 (V/3-8; Fig. 37 : 5)

Unit Modern Debris

Definition: debris accumulated during terracing work in 1998.

Granulometry: heterogeneous mix.

Color: variable.

Inclusions: variable.

Interpretation: modern (1998).

Unit 1

Granulometry: - 0.5 cm of preserved vegetal remains;

Color: - black vegetal remains;

Structure: loose, lumpy, very little compaction.

Inclusions: preserved vegetal remains.

Interpretation: upper horizon of actual soil, very little pedologic evolution.

Unit 2.1

Definition: recent humic colluvial deposit.

Description: same description as Cut 2, unit 2.1.

Unit 2.2

Definition: very humic horizon resulting from washing of the earthen mound.

Description: same description as Cut 2, unit 2.2.

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.

Unit 4

Definition: very compact yellow silts.

Description: same as Cut 2, unit 4.

Cut 6 (Z/6-10; Fig. 38 : 6)

Unit 1

Description: identical to Cut 5, unit 1.

Unit R1

Description: identical to Cut 1, unit R1.

Unit R3

Description: identical to Cut 1, unit R3.

Cut 7 (J-K/4-8; Fig. 38 : 7)

Unit 1

Description: identical to Cut 5, unit 1.

Unit R1

Description: identical to Cut 1, unit R1.

Unit R3

Description: identical to Cut 1, unit R3.

Cut 8 (J-N/0; Fig. 38 : 8)

Unit 2.1

Granulometry: silt, slightly clayey.

Color: brown, yellowish, humic.

Structure: loose, lumpy, little compaction.

Inclusions: orange silt lumps.

Limits: lower loose limit.

Interpretation: colluvial deposit.

Links: identical to Cut 2, unit 2.1.

Unit 2.2

Granulometry: silt, slightly clayey.

Color:                  brown, grayish, humic.

Description: identical to Cut 2, unit 2.2.

Unit 4.1

Description: identical to Cut 2, unit 4, but with inclusion of a few structural stones.

Unit 4.2

Description: identical to Cut 3, unit 4.2.3.

 

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Copyright 2001, Reto Blumer, Switzerland
Copyright 2001, SLFA Zürich, Switzerland

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Last updated: 29-05-2001.