Stratigraphic and structural relationships between the Cushing, Cape Elizabeth, Bucksport, and Cross River formations, Portland - Boothbay area, Maine

Guidebook for field trips in southwestern Maine: New England Intercollegiate Geological Conference, 78th annual meeting, Bates College, Lewiston, Maine, October 17, 18, and 19, 1986: Trip B-

Bedrock geology of the Portland West quadrangle, Maine

Maine Geological Survey, Open-File Map 03-94https://digitalmaine.com/mgs_maps/1033/thumbnail.jp

Petrology, Structure, and Age Relations of the Igneous Rocks of the York Beach Area, Maine

Guidebook to field trips in southern Maine; 57th meeting, October 8-10, 1965, held at Bowdoin College: Trip

Geologic map of the Portland quadrangle, Maine

Maine Geological Survey (Department of Economic Development), Geologic Map Series GM-1https://digitalmaine.com/mgs_maps/1089/thumbnail.jp

The structural and stratigraphic development of the Casco Bay Group at Harpswell Neck, Maine

Guidebook for field trips in southwestern Maine: New England Intercollegiate Geological Conference, 78th annual meeting, Bates College, Lewiston, Maine, October 17, 18, and 19, 1986: Trip C-

Geological comparisons across the Norumbega Fault Zone, southwestern Maine

Guidebook for field trips in southwestern Maine: New England Intercollegiate Geological Conference, 78th annual meeting, Bates College, Lewiston, Maine, October 17, 18, and 19, 1986: Trip A-

Guidebook to field trips in southern Maine; 57th meeting, October 8-10, 1965, held at Bowdoin College

Trip A: Geology of the Orrs Island 7 1/2\u27 Quadrangle; Trip B: - Paleozoic Section Across Central Maine; Trip C: Nubble, Waisanen, Taminen and Harvard Mines; Trip D: Late-Glacial Stratigraphy of the Kennebec River Valley from Norridgewock to Solon, Maine; Trips E and J: Blue Hill Copper Mine; Trip F: Stratigraphy and Metamorphism in Southwestern Casco Bay, Maine; Trip G: Petrology, Structure, and Age Relations of Igneous Rocks of the York Beach Area, Maine; Trip H: Geology of the Kezar Falls - Newfield Area; Trip I: Eolian Features in Freeport and Wayne, Maine; Trip K: Geology of the Buxfield and Dixfield Quadrangles in Northwestern Main

Guidebook to field trips in southern Maine; 57th meeting, October 8-10, 1965, held at Bowdoin College: title page, table of contents, introduction

Front matte

The Geology and Geochemistry of the Agamenticus Complex, York, Maine

Guidebook for field trips in southern and west-central Maine, October 13, 14 and 15, 1989: New England Intercollegiate Geological Conference 81st annual meeting: Trip A-1; C-

40Ar/39Ar hornblende ages from southwestern Maine: evidence for Late Paleozoic metamorphism

40Ar/39Ar analyses of hornblendes from a 120 km long NE-trending transect within die high-grade rocks of the Casco Bay Group provide information regarding the timing of thermal events and subsequent cooling history of this region. In die north, plateau ages of 368-372 Ma record the time of cooling through argon closure temperatures (500°C) following Acadian metamorphism. In die central portion of the transect, hornblendes display younger ages (350-323 Ma) and release spectra which show evidence of a Late Paleozoic thermal overprint. To the soudi, significantly lower plateau ages are recorded (270-290 Ma). These lower ages date either die time of a Late Paleozoic diermal event or the time of cooling following a prolonged period of burial at deep crustal levels. The former interpretation is favored on the basis of the disturbed release spectra in the central portion of the transect and the fact that ages over the 60 km long southern portion of die transect are relatively constant at 280 ±10 Ma. If a Late Paleozoic thermal event occurred in this region it was evidently not accompanied by large amounts of deformation as structural evidence for such an event is lacking. The exact nature of the Late Paleozoic resetting of hornblendes in this portion of the Casco Bay Group is not clear; however, it may be related to die events which lead to granite emplacement 275 Ma ago in die Massabesic Gneiss Complex and the 272-282 Ma ages for monazites from die nearby Sebago Batholith. RÉSUMÉ Des analyses 40Ar/39Ar, effectuées sur des hornblendes prélevées sur une traverse NE de 120 km de longueur au sein des roches métamorphiques de haut degré du Groupe de Casco Bay, ont foumi des données sur l'âge des épisodes thermiques et l'histoire du refroidissement qui leur succéda dans ce secteur. Au nord, des âges-plateaux de 368 à 372 Ma datent le refroidissement via les tempeéatures de fermeture de 1'argon (500°C) sui vant le métamorphisme acadien. Dans la portion centrale de la traverse, les hornblendes exhibent des âges plus jeunes (350 a 325 Ma) et des spectres de diffusion qui portent la trace d'une surimprcssion thermique tardi-paléozoique. Vers le sud, on enregistre des âges-plateaux bien plus jeunes (270 â 290 Ma). Ces demiers datent soil un épisode thermique tardi-paléozoique, soil un refroidissement après un enfouissement prolongé profondément dans la croûte. On favorise la première interprètation à cause des spectres de diffusion dérangés que montre la portion centrale. de la traverse el parce que les âges obtenus au long des 60 km de la portion sud de la traverse sont rélativement constants à 280 +10Ma. Si cette région à subi un épisode thermique tardi-paléozoique, ce ne fut assurement pas de pair avec une déformation importante puisque la structure ne foumil aucun indice d'un tel événcment. La nature exacte de la remise à zéo tardi-paléozoiquedes hornblendes dans cette portion du Groupe de Casco Bay n'est pas apparente. On pourrait ce pendant la relier aux événements à l'origine de l'emplacement de granite dans le Complexe de Gneiss de Massabesic (il y a 275 Ma) ainsi qu'aux âges de 272-282 Ma des monazites du batholitc avoisinant de Sebago. [Traduit par le journal