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Syenitic rocks

Unit symbol: Ksy
Age range Cretaceous, Coniacian to Albian (113 to 86.3 Ma)
Lithology: Igneous - Plutonic
Group name: Granitic rocks of central and southeast Alaska
Nepheline syenite, syenite, monzonite, and subordinate alkaline plutonic rocks and dikes including malignite, ijolite, shonkinite, and pyroxenite (Patton and Miller, 1968). Part of the “western Yukon-Koyukuk plutonic suite” of Miller (1989), a potassic and ultrapotassic belt that outcrops from the northeast corner of the Bettles quadrangle to Saint Lawrence Island. K/Ar and 40Ar/39Ar ages range from about 95 to 113 Ma with the majority of ages between 105 and 109 Ma

Source map information

Source map Patton, W.W., Jr., and Miller, T.P., 1968, Regional geologic map of the Selawik and southeastern Baird Mountains quadrangles, Alaska: U.S. Geological Survey Miscellaneous Geologic Investigations Map I-530, 1 sheet, scale 1:250,000.
Symbol Kgi
Unit name Syenite and monzonite
Description Chiefly leuco- to mesocratic, medium-grained gneissic syenite and monzonite
Lithology Igneous

Correlated geologic units

Label Ksy
Description Syenite
Geologic age Albian to Santonian
Geologic setting Intrusive
Lithology Form Importance
Monzonite < Syenitic < Plutonic < Igneous Pluton Major
Syenite < Syenitic < Plutonic < Igneous Pluton Major