|Titre||Sediment provenance and diagenesis, Lower Cretaceous of the Alma K-85 well, Scotian Shelf|
|Auteur||Pe-Piper, G; Piper, D J W; Lefort, D; Ledger-Piercey, S|
|Source||Commission géologique du Canada, Dossier public 6837, 2011, 326 pages, https://doi.org/10.4095/288723 (Accès ouvert)|
|Éditeur||Ressources naturelles Canada|
|Media||en ligne; numérique|
|Province||Région extracotière de l'est|
|Lat/Long OENS|| -61.0000 -60.0000 44.0000 43.0000|
|Sujets||pétrologie du sediment; origine; diagenèse; faciès diagénétiques; sediments; sédiments marins; milieux sédimentaires; roches sédimentaires; grès; puits; Crétacé inférieur; interprétations géochimiques;
minéraux détritiques; spinelle; chromite; zircon; grenat; tourmaline; feldspath; muscovite; apatite; chlorite; biotite; lithologie; lithostratigraphie; Formation de Missisauga ; Formation de Logan Canyon ; Puit Alma K-85 ; sédimentologie;
minéralogie; géologie marine; Mésozoïque; Crétacé|
|Illustrations||location maps; analyses; stratigraphic columns; seismic reflection profiles; photographs; ternary diagrams; plots; tables|
|Programme||Géoscience en mer, Analyse de bassin et ressources géoscientifiques|
|Diffusé||2011 06 22|
|Résumé||(disponible en anglais seulement)|
Eight conventional cores from the Alma K-85 well have been logged and sampled. They represent the Albian Cree Member of the Logan Canyon Formation and the
predominantly Barremian Upper Member of the Missisauga Formation. Compared with other wells in the southwestern Sable sub-basin, prodeltaic turbidites are rare and sediments comprise principally shoreface sandstones and open shelf mudstones. The
Upper Missisauga interval accumulated on a prodelta slope and almost all sandstones are part of slide blocks 10-15 m thick.
Detrital petrology is strikingly different from that of the Abenaki sub-basin, as represented by the Peskowesk A-99 well.
The sandstones at Alma are principally quartz arenites, in contrast to sublitharenites at Peskowesk. At Alma, the predominant feldspar is plagioclase and lithic clasts from metamorphic and sedimentary sources are more abundant than at Peskowesk,
which appears to have a predominantly felsic igneous source with abundant Kfeldspar. A substantial component of the sediment at Alma has a polycyclic source, probably from Carboniferous or Lower Paleozoic sandstones, resulting in the concentration of
resistant heavy minerals such as chromite/spinel and zircon, and perhaps tourmaline and garnet. Nevertheless, the dominant chemical types of garnet, tourmaline, detrital chlorite and igneous muscovite are all consistent with sources in the Meguma
Spinel/chromite, tourmaline and plagioclase all show little change in abundance with depth, suggesting that the source of sediment remained approximately the same throughout the sampled interval. In contrast, garnet appears to become
diagenetically unstable at depth and less K-feldspar appears to have been supplied.
The paragenetic sequence of diagenetic minerals is similar to that found elsewhere in the southwestern Sable sub-basin, with some early kaolinite and important
early and late Fe-calcite cements. However, Fe-silicate minerals resulting from suboxic reduction of Fe, characteristic of brackish water and low organic carbon, are very rare, and even siderite is uncommon. These observations reflect the dominance
of fully marine (shoreface and open shelf) lithofacies, and accounts for the absence of chlorite rims on quartz grains. The lack of late ankerite cement may also be related to the relative paucity of siderite.