GEOL 340 Sedimentology and Stratigraphy
Lecture 9
1. Stratification and Bedforms (continued)
2. Bedding-Plane Markings
3. Others
Stratification and Bedforms (continued)
Soft Sediment Deformation
convolute bedding and lamination = syndepositional plastic
deformation
(Figs. 4.23, p. 106)
flame structures = post-depositional plastic deformation (4.24,
p. 106)
ball and pillows = syndepositional foundering liquification (Fig.
4.25, p. 107)
slump structures = syndepositional gravity sliding (Fig. 4.26,
p. 108)
dish and pillar structures = horizontal and vertical dewatering
(Fig. 4.27, p. 108)
Erosion Structures
channels = u- or v-shaped troughs (scour-and-fill; Fig. 4.28,
p. 109)
Bedding-Plane Markings
Erosion and Deposition Structures (Fig. 4.30, p. 110)
sole markings = positive relief casts at base of beds
current- and tool-formed
groove casts = linear ridges (Fig. 4.31, p. 111)
chevrons with "v" pointing downstream
bounce, brush, prod, roll, and skip marks = gouges on bed (Fig.
4.32, p. 112)
flute casts = elongate ridge, bulbous nose flaring downstream
(Fig. 4.33, p. 113)
vortex scouring
current crescents = similar scouring with wave breaking geometry
downstream
(Fig. 4.34, p. 113)
Deformation Structures
load casts = irregular bulges and shapes, post-depositional (Fig.
4.35, p. 114)
Trace Fossils (Ichnofossils; Tab. 4.2, p. 117, Fig. 4.36, p.
118)
bioturbation structures = burrows, tracks, trails, locomation
biostratification = stromatolites, thrombolites (no internal
laminae)
controvercial: abiotic? versus biotic? (Fig. 4.42, p. 123)
bioerosion = borings, scrappings, bitings
excrement = coprolites, fecal pelelets
ichnofacies = environmental assemblages
Others
mudcracks = subaerial dessication cracks, V-shaped polygonal
fractures
(Fig. 4.44, p. 125)
syneresis cracks = subaqueous clay dewatering cracks, discontinuous
raindrop and haildrop imprints
rill (dendritic dewatering) and swash marks (arcuate swash lines)
parting (current) lineation = parallel to current
sandstone dikes and sills = tabular bodies of massive sandstone
concretions and sand crystals = diagenetic precipitates within
sand bodies
stylolites = compression and dissolution structures
Impact Structures
many of the features mentioned above can be formed during impacts,
as well as in
standard terrestrial, fluvial and submarine environments
list and the basic impact sed structures