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| Titel |
Paleoenvironments of Early Devonian plants and fish in the Campbellton Formation, New Brunswick, Canada: invasion of the land at a classic locality |
| VerfasserIn |
Kirsten Kennedy, Martin Gibling |
| Konferenz |
EGU General Assembly 2011
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250055582
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| Zusammenfassung |
| The Campbellton Formation has long been recognized for an unusually well preserved
assemblage of early plants, arthropods, and fishes, as well as some of the world’s oldest coals.
It represents an Early Devonian (Emsian) subtropical terrestrial environment in an
intermontane setting during the Acadian Orogeny. However, paleoenvironments
as revealed by a detailed sedimentological approach have not been determined.
The formation developed above 6 km of Lochkovian and Pragian volcanics, from
which nearly all detrital material within the Campbellton Formation has likely been
derived. The contact with these volcanics can be seen as fissured rhyolite that was
submerged and buried by micritic mudstone containing plants, spores, ostracods,
gastropods, fish, and eurypterids. Plants fossils including representatives of the
rhyniophytes, lycopsids, trimerophytes, and zosterophyllopsids were predominantly
preserved in lakes and fluvial floodplains. Marginal lake deposits contain well preserved
plants in coarse volcaniclastic siltstones with intensive alteration of feldspars to
kaolinite. No roots were observed, but the excellent preservation suggests that the
plants were preserved close to their growth position. Interbedded conglomerates
suggest that the lakes occupied a steep-sided valley where high sedimentation rates
promoted rapid burial of plant material. Deep lake deposits include massive and
laminated siltstones with abundant but poorly preserved plant fragments, likely
preserved where anoxic conditions developed under stable stratification. A few
coals up to 10 cm thick consist of stacked cuticle material, and are probably drifted
accumulations in shallow water. Fluvial sandstones and conglomerates contain
comminuted plant material, and associated shales have abundant and well preserved plant
material but lack much alteration of feldspars to kaolinite, although chlorite is present.
Plant diversity in floodplain shales is greater than in the marginal lacustrine setting.
Terrestrial arthropods are rare but scorpions, millipedes, and Eoarthropleura have been
found in fluvial beds. One fluvial interval contains root traces; however soils are thin
and immature. Thick alluvial cobble-boulder conglomerates, attributed to debris
flows and hyperconcentrated flows in proximal settings, contain sandy lenses with
plant material, as well as reported clasts of the giant putative fungus Prototaxites.
Although this Emsian formation yields little evidence of rooted in-situ assemblages,
plants are abundant and they and other organisms were adapted to a wide range
of lowland and basin-margin environments, including proximal gravelly systems. |
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