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

Abstract

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

The bounding-surfaces record of a barrier spit from Huangqihai Lake, North China: implications for coastal barrier boundary hierarchy

“…The boundary underlying the swash laminated sands is also a 1 st order surface (Fig.4), because it represents another beginning of a storm deposition. The record of 2 nd order surfaces is uncommon, due to the fact that washover deposits are often eroded by subsequent storms as identifi ed in Fig.2c and suggested by Nutz, especially in forced regression conditions (Nutz et al, 2015). The 3 rd order surfaces described in this study are comparable to the 1 st order and 2 nd order surfaces defi ned by Miall (1996), representing sedimentation of similar bedform type.…”

“…The architecture records in the GPR and trenches shows the growth of this spit and washover features. Washover bounding surfaces similar to those described in this study have been described previously (Schwartz, 1982;Neal et al, 2003;Switzer et al, 2006;Switzer and Jones, 2008;Nebel et al, 2011;Nutz et al, 2015;Shan et al, 2015), although in those researches, no hierarchy model was proposed.…”

The nonglacial diamictite of Toutswemogala Hill (lower Karoo Supergroup, central Botswana): Implications on the extent of the late Paleozoic ice age in the Kalahari–Karoo Basin

“…9). As a matter of fact, studies that tackled deglaciation sedimentary successions in the Quaternary have indeed demonstrated that proglacial deltaic systems may lack any evidence directly diagnostic of glacial processes, despite being fed by meltwater and glaciogenic sediments from retreating ice sheet margins (Nutz et al 2015;Dietrich et al 2017Dietrich et al , 2018. In the current case study, the presence of laminated fine-grained sediments (FA2) suggest the influence of a seasonal climatic setting and as such may represent varvites (i.e., alternation between cold and warmer seasons; Zolitschka et al 2015) in periglacial lakes (Catuneanu et al 2005) although the annual character is not demonstrable here.…”

Fluvio‐lacustrine sedimentation in the Agadir‐Tissint Feija (Anti‐Atlas, Morocco): A promising palaeoclimate archive for the last glacial cycle in northwest Africa

“…Consequently, F4-F7 facies are classified using the terminology proposed by Arenas-Abad, Vazquez-Urbez, Pardo-Tirapu, and Sancho-Marcéen (2010) which describes tufa in either lake shore or fluvial domains. The third type of sedimentary facies includes sandstones and conglomerates (F8-F11) reflecting deposition from mostly dilute flows attributed to the activity of a river system (Miall, 2014;Nutz et al, 2015;Schomacker, Kjemperud, Nystuen, & Jahren, 2010). All these sedimentary facies (Table 1) point to the existence of ancient lacustrine-to-fluvial sedimentary systems and document depositional environments such as offshore lake, lake margin, lake shore, fluvial cascade, alluvial plain and alluvial fan.…”