Glacial Environments - Trace Fossils as Indicators of Sedimentary Environments - page 292

deposit feeders tend to dominate. Under anoxic conditions, bioturbation is
suppressed. In other cases, turbidity currents and hyperpycnal flows may supply
oxygen to the fjord floor, resulting in intense postevent bioturbation (e.g.,
Schatz et al., 2011b ). The degree of substrate consolidation may be highly var-
iable in fjords (e.g., Schatz et al., 2011a ). Muddy soupgrounds are rather com-
mon close to the glacier margin, limiting colonization by epifaunal organisms
( Eyles et al., 1992 ). Softground communities with more diverse epifauna and
infauna tend to occur distally, while the proximal fluid muds appear to be unbio-
turbated ( Buatois and M ´ ngano, 2011 ), although this may be due to the low
preservation potential of biogenic structures. Firmground suites tend to be asso-
ciated with current-winnowed substrates ( Eyles et al., 1992 ). Finally, many
fjords are subjected to intense wave action, resulting in a deeply emplaced
storm-wave base and repeated storms impart a strong influence on
benthic communities in relatively deep water ( Buatois and M ´ ngano, 2011;
Syvitski et al., 1987 ).
2.2 Postglacial Colonization of Terrestrial Environments
Studies concerning the faunal primary succession in deglaciated terrestrial areas
are scarce. Kaufmann (2001) analyzed the terrestrial invertebrate succession in
an alpine glacier foreland during the summer-fall period based on the epigean
fauna. Despite the fact that the area in front of the glacier had been ice-free for
the past 9500 years, the disturbed surface of the outwash plain is much younger.
Colonization of the outwash surface began in sunny, stabilized areas and com-
munities from within outwash plains were younger than those from terminal
moraine slopes with developed soils. Predators were the first colonizers, while
herbivores and decomposers appeared later.
Recolonization of the glacier foreland occurred comparatively faster than in
other barren environments (e.g., newly emerged islands), and can be compared
with recolonization of volcanic deposits, where a mobile and tolerant inverte-
brate fauna migrates from adjacent areas to explore and establish breeding
populations in newly deposited material ( Kaufmann, 2001 ).
The terrestrial invertebrate fauna was composed chiefly of arthropods,
mainly insects (e.g., ants, flies, beetles), arachnids (e.g., spiders), and “myria-
pods” (centipedes and millipedes; Kaufmann, 2001 ). Carnivores, like carabeid
and staphylinid beetles, and lycopsid and linyphiid spiders were the pioneer spe-
cies, and despite of the initial lack of vegetation, rhizophagous elaterid beetles
were also present. Myriapods colonized later, when communities became estab-
lished. Centipedes (Chilopoda) appeared first, with the herbivorous beetles and
detritivorous millipedes (Diplopoda) appearing later. Lumbricidae were scarce
in the glacier foreland but common in adjacent grassland areas. Mobile flying
insects, especially dipterans, were widespread in all areas, but dipteran larvae
were absent in the youngest sites and in the outwash plain. According to Kaufmann
(2001) , the biomass produced in the glacier foreland was sufficient to sustain