Terrestrial Palaeoecology and Global Change

Chapter 2. Taphonomy
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Fig. 10. Intracratonic and marginal sedimentary basins controlled by concurrent and transcurrent fault
systems.
Both offshore and lateral, along-shore, spread of nepheloid layer (with suspended
particulate matter) depends on slope relief controlling suspension currents and the coupling
of pelagic and benthic processes (Wollast et al., 2001). The temperate zone estuaries
deposit during a spring freshet up to 0.5 m thick organic-rich sediment at the turbidity
maximum zone, the location of which depends both on freshwater outflow and flocculation
induced by saline intrusions (Woodruff et al., 2001). Suspended material is conducted
along the fault-bound canyons, with major deposition foci at their heads. Hence continental
margin geomorphology, defined by tectonic developments, is of primary importance
to the biospheric carbon cycle.
Active tectonic zones produce a greater diversity of taphonomic environments owing
to their heterogeneous landscapes, earthquake-generated debris flows and volcanism.
Taphonomic effects of volcanic activity are multiple, such as vegetation burning, leaf fall,
in situ burial by ash fall, transportation (occasionally of tree trunks in upright position) by
pyroclastic flows, stream ponding, etc. (Spicer, 1989a; Scott, 1990; Archangelsky et al.,
1995). Differentiation of positive volcanic features – coastal ranges, island arcs – divided
by the fault-bound foredeeps and transverse troughs results in an intricate mosaic of
taphonomic environments. In contrast, an epeiric subsidence generates a pattern of few
extensive taphonomic zones recurrent over sedimentary sequences.
II.5.1. Intracratonal basins
Intracratonal basins are taphrogenic depressions of various shapes and dimensions, sometimes
traversing entire continents. They are persistent over times as negative, intermittently
subsiding features. Their origins are due either to ongoing rifting or to crustal sagging over the
sutures of an older rifting phase. They are rift basins or epirift basins, respectively.