Évolution des structures deltaïques du delta de la rivière Natashquan, Québec

Sala, Monique; Long, Bernard

doi:10.7202/032785ar

Cited by 4 publications

(2 citation statements)

References 11 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The resulting deltaic complexes have been investigated by onshore or offshore studies in several areas of the St Lawrence Estuary and Gulf (for example, Natashquan: Long et al ., ; Sala & Long, ; Sept‐Îles: Dredge, ; Normandeau et al ., ; Boyer‐Villemaire et al ., ; Betsiamites and Manicouagan‐Outardes: Bernatchez, ; Hart & Long, ; Portneuf: Dionne et al ., ; Tadoussac: Dionne, ; Dionne & Occhietti, ). A recent overview of the subaqueous expressions of the deltaic systems in the St. Lawrence Estuary is given by Normandeau et al .…”

Section: Regional Settingmentioning

confidence: 99%

From outwash to coastal systems in the Portneuf–Forestville deltaic complex (Québec North Shore): Anatomy of a forced regressive deglacial sequence

et al. 2017

View full text Add to dashboard Cite

Deglacial sequences typically include backstepping grounding zone wedges and prevailing glaciomarine depositional facies. However, in coastal domains, deglacial sequences are dominated by depositional systems ranging from turbiditic to fluvial facies. Such deglacial sequences are strongly impacted by glacio‐isostatic rebound, the rate and amplitude of which commonly outpaces those of post‐glacial eustatic sea‐level rise. This results in a sustained relative sea‐level fall covering the entire depositional time interval. This paper examines a Late Quaternary, forced regressive, deglacial sequence located on the North Shore of the St. Lawrence Estuary (Portneuf Peninsula, Québec, Canada) and aims to decipher the main controls that governed its stratigraphic architecture. The forced regressive deglacial sequence forms a thick (>100 m) and extensive (>100 km2) multiphased deltaic complex emplaced after the retreat of the Laurentide Ice Sheet margin from the study area ca 12 500 years ago. The sedimentary succession is composed of ice‐contact, glaciomarine, turbiditic, deltaic, fluvial and coastal depositional units. A four‐stage development is recognized: (i) an early ice‐contact stage (esker, glaciomarine mud and outwash fan); (ii) an in‐valley progradational stage (fjord head or moraine‐dammed lacustrine deltas) fed by glacigenics; (iii) an open‐coast deltaic progradation, when proglacial depositional systems expanded beyond the valley outlets and merged together; and (iv) a final stage of river entrenchment and shallow marine reworking that affected the previously emplaced deltaic complex. Most of the sedimentary volume (10 to 15 km3) was emplaced during the three‐first stages over a ca 2 kyr interval. In spite of sustained high rates of relative sea‐level fall (50 to 30 mm·year−1), delta plain accretion occurred up to the end of the proglacial open‐coast progradational stage. River entrenchment only occurred later, after a significant decrease in the relative sea‐level fall rates (<30 mm·year−1), and was concurrent with the formation and preservation of extensive coastal deposits (raised beaches, spit platform and barrier sands). The turnaround from delta plain accretion to river entrenchment and coastal erosion is interpreted to be a consequence of the retreat of the ice margin from the river drainage basins that led to the drastic drop of sediment supply and the abrupt decrease in progradation rates. The main internal stratigraphic discontinuity within the forced regressive deglacial sequence does not reflect changes in relative sea‐level variations.

show abstract

Section: Regional Settingmentioning

confidence: 99%

From outwash to coastal systems in the Portneuf–Forestville deltaic complex (Québec North Shore): Anatomy of a forced regressive deglacial sequence

et al. 2017

View full text Add to dashboard Cite

show abstract

“…Identified either from fluvio‐deltaic (e.g. Sala & Long, ; Hart & Long, ; Hansen, ; Eilertsen et al ., , ) or coastal (e.g. Boulton, ; Fraser et al ., ) deposits, comparable successions are widely investigated.…”

Section: Introductionmentioning

confidence: 99%

Forced regressive deposits of a deglaciation sequence: Example from the Late Quaternary succession in the Lake Saint‐Jean basin (Québec, Canada)

et al. 2015

View full text Add to dashboard Cite

International audienceDifferentiating between forced regressive deposits from deglacial periods inhigh latitude domains and forced regressive deposits from the onset of glacialperiods in low latitude domains is fundamental for the accurate interpretationof glacial cycles within the geological record and then for thereconstruction of palaeogeography and palaeo-climate. A forced regressivedeglacial sequence is documented from the Lake Saint-Jean basin (Quebec,Canada). In this area, the Late Pleistocene to Holocene sediments haverecorded the Laurentide ice sheet retreat accompanied by the invasion ofmarine waters (Laflamme Gulf) from ca 129 cal kyr BP. Subsequently, fluviodeltaicand coastal prograding wedges were deposited; they followed thebase-level fall due to glacio-isostatic rebound. This succession, representinga transition from glacial to post-glacial periods within a previously glaciatedarea, was investigated through recent mapping, preserved landforms, faciesanalysis, and new optical stimulated luminescence and radiocarbon dates.Three basin-scale geological sections share a common lower part made ofisolated ice-contact fan deposits overlying bedrock. Throughout the entirebasin, ice-contact fans are capped by glacimarine muds. Above, fluvial andcoastal prograding systems were deposited and evolved through four steps:(i) deltaic systems progressively increased in width; (ii) coastal influence onsedimentation increased; (iii) hydrographic drainage systems became moreorganised; and (iv) deltas graded from steep (Gilbert delta) to low-angle foresets(mouth-bar delta). Deposited during the base-level fall from glacioisostaticrebound, the complete succession has been designated as a singlefalling stage system tract referred to as a deglacial falling stage system tract.It is representative of a deglaciation sequence in areas previously covered byice during glacial periods (i.e. medium to high latitude domains). Diagnosticcriteria are provided to identify such a deglacial falling stage system tract inthe geological record, which may aid identification of previously unknownglacial cycles

show abstract

Timing and controls on the delivery of coarse sediment to deltas and submarine fans on a formerly glaciated coast and shelf

Normandeau¹,

Dietrich²,

Lajeunesse³

et al. 2017

GSA Bulletin

View full text Add to dashboard Cite

24The evolution of deltas and submarine fans is often envisioned as largely controlled by 25 relative sea-level (RSL) variations. However, in some cases, RSL can have less effect on 26 delta and submarine fan activity than sediment supply and shelf geomorphology. In order 27to document the relative importance of these three factors on deltaic and submarine fan 28 evolution in a former glaciated environment, this paper documents the delivery of coarse 29 sediment to the Laurentian Channel (eastern Canada). The well-constrained stratigraphic 30 and geomorphological framework of both the glacio-isostatically uplifted deltas and the 31 modern Laurentian Channel fans allow us to document and contrast the evolution of 32 river-fed deltas, river-fed canyon/fan systems and longshore drift-fed fans during 33 deglacial and postglacial times. The evolution of these different types of fans can be 34 divided into three phases. The first phase is characterized by delta progradation on the 35 shelf while RSL was at its maximum, although already falling, and the ice-margin 36 gradually retreated inland. The second phase is characterized by the delivery of deltaic 37 sediment in the deep realm of the Laurentian Channel, permitted by the supply of large 38 amounts of glaciogenic sediments derived from the retreating ice margin and the 39 lowering of the RSL. At the same time, sediment instability along the steep Laurentian 40 3 Channel formed small incisions that evolved into submarine canyons where the narrow 41 shelf allowed the trapping of longshore sediment. The third phase is characterized by the 42 withdrawal of the ice-margin from the watershed of the main rivers and the drastic 43 decrease in sediment supply to the deltas. Consequently, the delta fronts experienced 44 strong coastal erosion, even though RSL was still lowering in some cases, and the eroded 45 sediments were transferred onto the shelf and to adjacent bays. This transfer of coastal 46 sediments allowed the continued activity of longshore drift-fed canyons. The retreat of 47 the ice margin from the watersheds thus controlled the supply of sediment and induced a 48 change in delta type, passing from river-dominated to wave-dominated. This paper 49 highlights the role of the type of sediment supply (ice-contact, glaciofluvial and 50 longshore drift) in the timing and activity of submarine fans in high-latitude 51 environments. It proposes a conceptual model for high-latitude shelves where sediment 52 delivery to submarine fans is mostly controlled by structural inheritance (watershed area 53 and shelf geomorphology) rather than RSL fluctuations. Therefore, although RSL fell 54 during delta progradation, this study demonstrates that it was not the main contributor to 55 delta and submarine fan growth. This has wider implications for the extraction of sea-56 level information from stratigraphic successions. 57

show abstract

Évolution des structures deltaïques du delta de la rivière Natashquan, Québec

Cited by 4 publications

References 11 publications

From outwash to coastal systems in the Portneuf–Forestville deltaic complex (Québec North Shore): Anatomy of a forced regressive deglacial sequence

From outwash to coastal systems in the Portneuf–Forestville deltaic complex (Québec North Shore): Anatomy of a forced regressive deglacial sequence

Forced regressive deposits of a deglaciation sequence: Example from the Late Quaternary succession in the Lake Saint‐Jean basin (Québec, Canada)

Timing and controls on the delivery of coarse sediment to deltas and submarine fans on a formerly glaciated coast and shelf

Contact Info

Product

Resources

About