|Title||Architecture and morphodynamics of a 16 Ga fluvial sandstone: Ellice Formation of Elu Basin, Arctic Canada
|Author||Ielpi, A; Rainbird, R H|
|Source||Sedimentology 2015., https://doi.org/10.1111/sed.12211|
|Alt Series||Earth Sciences Sector, Contribution Series 20150028|
|NTS||77; 87; 97|
|Area||Elu Inlet; Melvill Sound|
|Lat/Long WENS||-108.0000 -106.0000 68.7500 68.0000|
|Subjects||sedimentology; sedimentary rocks; sandstones; fluvial deposits; fluvial studies; sedimentation; sedimentary structures; sedimentary environments; eolian deposits; coastal environment; coastal studies;
Ellice Formation; Elu Basin; Precambrian|
|Illustrations||location maps; photographs; rose diagrams; tables; stratigraphic sections|
|Program||Rae Province, Chantrey-Thelon, GEM2: Geo-mapping for Energy and Minerals|
|Abstract||Precambrian fluvial deposits have been traditionally described as architecturally simple, forming shallow and wide braidplains with sheet-like geometry. The geomorphic variability and morphodynamics of
the 1.6 Ga Ellice Formation of Elu Basin, Nunavut, Canada, is here explored. The Ellice Formation is well exposed along coastal platforms and stepped cliffs that allow the assessment of its depositional architecture in both section and planform.
Siliciclastic rocks overlie older deposits and Archean crystalline rocks, and record sedimentation in fluvial, aeolian, coastal and nearshore-marine environments. The fluvial deposits display drainage toward the west-northwest, while overlying
shallow marine deposits record transgression toward the east-southeast. At the basin scale, the Ellice Formation displays dispersed palaeoflow at its base, and higher in the section where fluvial and aeolian deposits are associated. Elsewhere, mainly
unimodal palaeoflow points to extensive low-sinuosity fluvial deposition.|
Within the terrestrial deposits, fluvial, fluvial-aeolian, and coastal architectural elements were recognized. Fluvial elements comprise cross-bedded sandstone and minor
conglomerate, exhibiting an overall fining-upward trend with associated decrease in preservation, dimension and amalgamation of channel bodies. These motifs are interpreted to portray a shift from proximal trunk rivers to mature alluvial plains.
Low-sinuosity fluvial elements are the most common, and include major channel bodies, elongate side bars, and mid-channel bars with well-developed scroll topography. High-sinuosity channel-bar complexes exhibit upbar-flow rotation and yield evidence
of bar expansion coupled with rotation and translation. Fluvial-aeolian elements are composed of aeolian dunes juxtaposed with isolated channel bodies and bank-attached bars. Minor mixed fluvial-aeolian sheets record local deposition in unconfined
floodbasins or inter-distributary highlands. Finally, coastal elements comprise small deltaic complexes composed of sand-rich distributary-channel bodies feeding heterolithic mouth bars. Overall, the sedimentary record of the Ellice Formation
demonstrates an example from the Precambrian where alluvium was locally characterized by a higher geomorphic variability than previously thought.
|Summary||(Plain Language Summary, not published)|
Precambrian river deposits have been traditionally described as forming shallow and wide braidplains with sheet-like geometry. In this paper we try to
show that this is not necessarily the case through our examination of the 1.6 Ga Ellice Formation of Elu Basin, Nunavut, Canada. The Ellice Formation is well exposed along coastal platforms and cliffs that allow the assessment of its sedimentiology
in both section and plan. Sandstones overlie older deposits and Archean crystalline rocks, and record sedimentation in rivers, eolian dunes, coastal and nearshore-marine environments. The river deposits display drainage toward the west-northwest,
while overlying shallow marine deposits record marine transgression toward the east-southeast. The Ellice Formation displays structures which show that rivers initially had dispersed directions of transport, but then later had more unidirectional
flow. Overall,the Ellice Formation demonstrates an example from the Precambrian where alluvium was locally characterized by a higher geomorphic variability than previously thought.