Abstract

Fission track ages were obtained for ten apatite concentrates from six post-Paleozoic stocks in southern Maine in order to: (1) check the reliability of the fission track method in post-Paleozoic terrains, (2) establish an age for the youngest igneous event in the area, and (3) check the geologic correlation of the Burnt Meadow Complex and the Agamenticus Complex with the White Mountain plutonic-volcanic series.

A mean age of 119 ± 9 m.y. was obtained for the Cape Neddick Gabbro (3 samples), the Tatnic Complex, the alkaline syenite at Litchfield, Maine, and the Abbott Mountain Syenite. This value suggests the presence of an Early Cretaceous (?) igneous event in southern Maine that correlates chronologically with the Monteregian Hills in Quebec and younger intrusions in Vermont.

Ages were determined for four samples from two older intrusions that correlate on mineralogic and structural similarity with the White Mountain plutonic-volcanic series. Ages of 116 m.y. from the Agamenticus Complex and 143 m.y. from the Burnt Meadow Complex reflect the low-annealing temperature for fission tracks in apatite. Ages of 177 m.y. from the Burnt Meadow Complex and 172 m.y. from the Agamenticus Complex provide support for their chronologic correlation with the White Mountain plutonic-volcanic series established as 180 ± 5 m.y.

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