Geoscience Reference
In-Depth Information
angles to confirm identification. Tabular beds and the
horizontal lamination between the inclined beds as shown
in (a) are consistent with planar cross-stratification.
(a) plan view
(b)
Note:
Structure needs to be examined in faces at right
angles to confirm identification. Lensoid shaped beds as
shown in (c) are consistent with trough cross-stratification.
Trough cross-stratification
10 cm
(c) cross-section
(d)
Hummocky and swaley cross-stratification
Note:
Hummocky and swaley cross-stratification are part
of a continuum. HCS has a 1:1 ratio of hummocks :
swales whereas SCS is mainly swales as the hummocks
have been eroded. For any location the wave length of
the structure increases from HCS to SCS.
Hummocky cross-stratification (HCS)
(e) cross-section
(f)
upward curvature of
laminations over
hummock
Swaley cross-stratification (SCS)
swale with low-angle
curved lamina
intersections
(g) cross-section
(h)
Figure A6.17
Common sedimentary structures. See also Tables 6.2-6.4. Red penknife is 9 cm long. (All
Angela L. Coe, The Open University, UK, except (x) and (cc), R. Chris L. Wilson.)
