The Bouma Sequence

8/20/2019 The Bouma Sequence

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Fig. 8.1. The turbidite facies model (i.e., the Bouma Sequence) showing Ta, Tb,

Tc, Td, and Te divisions. Conventional interpretation is that the entire sequence is

a product of a turbidity current (Bouma, 1962; Walker, 1965; Middleton and


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Fig. 8.2. ( A) Sedimentological log of Unit 10 showing contorted layers in association with sigmoidal cross beds. (B) Outcrop photographof contorted layers. Arrow shows stratigraphic position of contorted layers. Annot Sandstone (Eocene–Oligocene), Peira Cava area,

French Maritime Alps. SE France.


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Fig. 8.9. ( A) Sedimentological log of amalgamated sandstone Unit 1 showing basal

complex normal grading (0–2 m) with floating quartzose granules and a simple normal


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Fig. 8.11. ( A) Sedimentological log of amalgamated sandstone Unit 8 showing basalinverse grading, floating armored mudstone balls, lenticular layers, and pockets of

gravel. (B) Outcrop photograph of Unit 8 showing a pocket of gravel (dashed line)

with quartz, feldspar, rock fragments, and mudstone clasts in fine-grained sandstone.

Arrow shows stratigraphic position of photo. Annot Sandstone (Eocene–Oligocene),

Peira Cava area, French Maritime Alps. SE France.


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Fig. 8.13. Diagram showing three increasing levels of detail in field description of Unit 8. Level 1: Low degree of detail that shows a

simple normally graded bed. Note absence of basal inverse grading and other complex features. This level of detail would result in

interpretation of the sandstone unit as the deposit of a single turbidity current. Bouma’s (1962) published graphic logs of 157 layers in

measured sections of K (38 layers), ABC (28 layers), and Q (91 layers), which include Unit 8 of this study. They all show level 1

degree of detail (see Bouma 1962 his Enclosures I II and III) Level 2: Moderate degree of detail shows a normally graded bed with


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Fig. 8.16. ( A) Sedimentological log of amalgamated sandstone Unit 7. (B) Outcrop photograph showing hollows created by

weathering out of floating mudstone clasts. Note random orientation of mudstone clasts. Note floating quartzose granules in medium-

to- coarse grade sandstone. Photo taken at about 2 m stratigraphic position in Unit 7 (arrow). Annot Sandstone (Eocene–Oligocene),

Peira Cava area, French Maritime Alps. SE France.


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Fig. 8.18. Top: Schematic diagram showing development of simple normal grading by


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Fig. 8.19. Conceptual model showing reworking the tops of downslope sandy debris

flows by along-slope bottom currents. Such complex deposits would generate a

sandy unit with a basal massive division and upper reworked divisions with traction

structures (ripple laminae), mimicking the ‘Bouma Sequence’.


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Fig. 8.20. Existing vertical facies models of (1) coarse-grained turbidites (Lowe,


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Fig. 8.21. A schematic diagram showing downslope changes in turbidite divisions

from coarse-grained turbidites (Lowe, 1982), through classic turbidites (Bouma,

1962), to fine-grained turbidites (Stow and Shanmugam, 1980). If existing turbiditefacies models were realistic, then an ideal turbidite bed should develop 16 divisions.

However, no one has ever documented such a turbidite bed with 16 divisions in the

field or in flume experiments. (After Shanmugam (2000a). Reproduced with

permission from Elsevier.)

The Bouma Sequence

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