Geology

Foothills

Siderite

Sea level

Sedimentology

Oceanography

Paleontology

Mineralogy

Geography

Outcrop

Quartz

Cartography

Bulletin of Canadian Petroleum Geology

ABSTRACT Samples of early diagenetic siderite from a single outcrop section of the Cardium Formation (Turonian-Coniacian) in the northern Rocky Mountain Foothills have been analyzed to determine whether trends exist in their oxygen isotopic and elemental compositions, and whether such parameters can be used to detect relative sea level changes. We found that vertical trends generally match those predicted based on the sedimentology and stratigraphy of the Formation; the 18O values become lower, and the siderites have less substitution of Fe by Mg and Ca, in strata deposited in environments inferred to have been subjected to greater freshwater influence. These results suggest that such measurements can be useful in corroborating interpretations of transgressive/regressive episodes in the stratigraphic record. RESUME Des echantillons de siderite de diagenese precoce provenant d'une section d'affleurement de la formation Cardium (Turonien-Coniacien) dans les Rocky Mountain Foothills du nord ont ete analyses afin de determiner si des tendances de composition isotopique de 1'oxygee ou elementaire existent, et si ces parametres peuvent etre utilises pour detecter des changements relatifs du niveau de la mer. Nous avons trouve que les tendances verticales coincident generalement a celles predites sur base de la sedimentologie et de la stratigraphie de la formation; les valeurs de 18O decroissent, et les siderites ont moins de substitution de Fe par Mg et Ca, dans les strates deposees dans des environnements interpretes comme ayant ete sujets a de plus grandes influences d'eau douce. Ces resultats suggerent que de telles mesures peuvent etre utiles pour corroborer des interpretations d'episodes de transgression/regression dans la stratigraphie. Traduit par Patrice de Caritat

Evidence for Relative Sea Level Change from Isotopic and Elemental Composition of Siderite in the Cardium Formation, Rocky Mountain Foothills