Geoscience Reference
In-Depth Information
Table A6.3
Types of common coals and their depositional environment.
Coal type
Components
Environment
Dull and bright, brittle,
crystalline clarain, vitrain
Woody
Lush, well vegetated, mature plants
Dull, waxy conchoidal,
cannel
Wind blown spores,
resin, cuticles, algae
Open water, lagoons, pools in forest/mire
Dirty, crumbly, soft,
fusain
Charcoal
Burnt vegetation, dry weather conditions, e.g. present-
day Borneo in an El Niño year
Dirty, heavy
High ash, clay
minerals
Forest, mire, raised bog, dirty windy conditions, high
muddy water level, seasonal rainfall changes, tropical/
temperate climate
Pyrite
High sulfur
Forest/mire/swamp, coastal estuarine, marginal marine
No pyrite
Low or no sulfur
Inland forest, mire, raised bog
Table A6.4
Ripples are common in the sedimentary record. This table indicates how to distinguish current-
formed ripples diagnostic of linear fl uid fl ow from wave-formed ripples diagnostic of the orbital motion of waves
produced by wind blowing over standing bodies of water.
Wave-formed ripples
Current-formed ripples
Profi le
Individual ripples are symmetrical
Individual ripples are asymmetrical
Ridges tend to have a sharp top
Ridges are gently rounded
Laminations within the ripple dip in
opposing directions
Laminations within the ripple dip in the same
direction
Ripple index (wavelength/
height) = 6-10
Ripple index (wavelength/height) = 8-20
Plan view
Crests are sinuous and bifurcate
Crests are straight or curved
Possible associated
structures that are
unique to either wave
or current processes
Hummocky cross-stratifi cation, swaley
cross-stratifi cation
Herringbone cross-stratifi cation (but care
needs to be taken not to confuse this with
complex wave-formed structures where the
sediment has been deposited on both sides
of the bedform
