Mud-dominated coastal systems play by their own rules. Many of
the generalizations derived from years of study of sandy shoreline systems
appear to not apply to shaley successions, or at least apply in unique ways. To
better understand spatial changes and proximal-to-distal facies relationships
of muddy systems, Harazim and McIlroy describe sedimentological, ichnological, and
geochemical characteristics of the Lower Ordovician (Tremadocian) Beach
Formation, Bell Island Group, Newfoundland. The results demonstrate that
ancient fine-grained coastal systems are incompletely incorporated into
sequence stratigraphic models owing to their atypical proximal-to-distal facies
relationships, unique physical sedimentologic properties, and burial
efficiency. The interpretations highlight the importance of 1) frequency
of sediment supply events, 2) direction of mud transport, 3) diagenetic
reactivity of minerals and bioavailable organic carbon, and (4) residence time
of mineral grains and organic matter close to the sediment–water interface on
facies architecture of this non-uniformitarian paleoenvironment, deposited
prior to the evolution of soils. Face
it, mud is complicated.
Mud-rich density-driven flows along an Early Ordovician storm-dominated shoreline: implications for shallow-marine facies models by Dario Harazim
and Duncan McIlroy
