OKAYAMA University Earth Science Reports, Vol. 15, No. 1, 9-32, (2008)

Microscopic observations of the recent soils: a step for understanding the paleosols

**

The microscopic observations of the recent soil horizons were conducted in Okayama, Japan (moderate climate). The several soil horizons, including two surface (epipedon) and three subsurface horizons, were recognized in the forest, poorly vegetated hill, and riverside around the Okayama University. The umbric epipedon can be segregated from the organic-rich subsurface horizons by the scattered organic materials in thin sections. The ochrich epipedon shows the sandy matrix without any cements and the illuviation of clay minerals. The subsurface horizons identified in the study area are as follows: albic, argillic, and cambic horizons. Each subsurface horizon shows the specific structures in thin sections. The albic horizon is characterized by the absence of the illuviation. The argillic horizon definitely shows the clayey matrix and the illuviation of clay minerals. The primary structures may be retained in the cambic horizon.

The microscopic examination of the Miocene paleosols from the Ukan-cho, Okayama, was attempted. By comparing the recent soils, the cambic horizon and spodic horizon, which is characterized by the concentration of sesquioxides, are identified in the paleosols. This attempt suggests that the microscopic observations of the recent soils is a useful guide to understanding the paleosols

Keywords : soil, paleosol, soil horizon, soil structure, microscopic observation

I.

, 1987

1960

100-1000

Bullock et al., 1984

1980-1990 Retallack

II.

II.I.

Soil Survey Staff (2003)

1

2

890-0132 1765-3Hanshin Consultants Co., Ltd. 1764-3 Katahirayama, Gumizaki, Satsumasendai-Shi, Kagoshima, 895-0132. Japan

**Department of Earth Sciences, Faculty of Science, Okayama University, Okayama 700-8530, Japan

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II.II.

2km

1891 - 2007 14.9 ºC

1134 mm

http://www.data.jma.go.jp/obd/stats/etrn/index.php

1 II.III.

surface horizon

epipedon subsurface

horizon

, 1975

FAO, 1974

Soil Survey Staff,

2003

Master horizon

Suffix symbol Subordinate

Gradations between master

horizons

II.IV.

1998

Bullock et al. (1984)

Retallack (2001)

500

500

2% Galehouse, 1971

III.

2 2

3 3

3.1. epipedon

1.

11

III.I. epipedon

3 umbric epipedon

ochric epipedon 2

2 - 10cm

3

4.1 roolet

4.2

ochric epipedon

4.3

Ab

4.4

Bh Ab

2, Loc. G

1 2

3 4

3

III.II. Gradations between

master horizons AB BA 2

AB A

3, Loc. H, I, N,

O 1 – 6 cm umbric epipedon

BA AB A

5- 8 cm

AB

4.5

4

Soil survey Staff, 2003

12

13

2.

14

2.

15

2.

16

2.

17

III.III. subsurface horizon albic E argillic

Bt Bts Bt(s) B(t)

cambic Bw Bw(s) C

1

4

albic 15cm

4.6

3

5Y7/2

4.6.a

4.4

5cm A umbric epipedon

AB 3cm

argillic

4 blocky ped

cambic

Bw

argillic

1

plasmic

microfabric

skelsepic

mosepic

lattice sepic 4.8

4.8

4.7

4.8

cambic

Bw C 2

3. Soil Survey Staff (2003)

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4.9 IV. IV.I.

3

FAO Luvisol

Alfisol Andosol Podzoluvisol

Luvisol Alfisol

lessivage

a. b. 1: A-1 A , 2: Eng-1 A , 3: D-1 A 1mm.

19

Bt

5 AB

Loc. A, C, D, E, G, H, M, N, P

Ultisol

5.1

Andosol Luvisol

cambic Bw

5, Loc. B, F, I, J, K, L, Q, R

AB BA

Loc. F, I, L

5.2

a. b. 4: G-2 Ab , 5: P-1 BA , 6: O-1 E 1mm.

20

Podzoluvisol

albic E

5

Ab

albic

spodic

Podzol Podzoluvisol

5.3;

Loc. O IV.II.

5.4

5.5

5 ochric epipedon

a. b. 7: G-1 Bt , 8: C-4 Bt , 9: E-1 Bw 1mm.

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5 1: Loc. A Luvisol , 2: Loc. F Andosol ,

3: Loc. G Podzoluvisol , 4: Cambisol , 5: ochric

epipedon , 6:

Fluvisol

22

cambic horizon C

FAO

Cambisol Inceptisol

IV.III.

5.6

ochric epipedon

5

cambic horizon (C )

Entisol

: incipient soil

Fluvisol

V.

IC

6.a

6.b,c

6d

glaebule

3

Ukan-1

7.1

skelsepic microfabric

2

8

C

1 2

6 IC 1:

2: 3: , 4:

23

cambic

cambic

spodic Bs

cambic

3m

Ukan-4

7.2

8

7.2

cambic

7 a.

b. 1: Ukan-1 (Bs ) 2: Ukan-4 (Bw ) 3: Ukan-3 (R ) 1mm.

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Ukan-3

6.

6

umbric epipedon

ochric epipedon

2

albic

argillic spodic cambic

4 albic

argillic

spodic

spodic 2

cambic

FAO

Luvisol Andosol Podzoluvisol Cambisol

Fluvisol 5

8

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Bullock, P., Ferdoroff, N., Jongerius, A., Stoops, G., Tursina, T., Babel, U. 1984. Handbook for Soil Thin Section Description. Waine Research Publication. 152 pp.

. 1998. .

: 328-328.

. 1976. 1975 . , 280: 1-28. F.A.O. 1974. Soil Map of the World Volume 1. Legend. UNESCO. 59pp. Galehouse, J. S. 1971. Point counting. In: Proceedings in sedimentary petrology. Rutherford, G. K. (ed.). Limestone Press:

385-407. . 1987. X . X , 19: 251-262.

Retallack, G. J. 2001. Soils of the Past An introduction to paleopedology. Blackwell Science. 404 pp. Soil Survey Staff, 2003. Keys to Soil Taxonomy. University Press of the Pacific Honolulu, Hawaii. 332 pp.

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