Pg. 15 and map. Mount Garfield porphyritic quartz syenite. Coarse- to medium-grained, usually green. Extends from just north of Mount Hale southwesterly to Hardwood Ridge. Is younger than both Kinsman quartz monzonite and Mount Lafayette porphyry, and either late Devonian or late Carboniferous. Assigned to White Mountain magma series.
Named for Mount Garfield, Franconia quadrangle, northwestern NH.
["White Mountain magma series" considered informal. The practice of employing "Series" for lithostratigraphic or lithodemic nomenclature is now regarded as improper. Term "Series" is applied formally only to chronostratigraphic units (ACSN, 1961, 1970; NACSN, 1983, 2005, 2021).]

Source: US geologic names lexicon (USGS Bull. 896, p. 1434).

Page F2 states that the White Mountain Plutonic-Volcanic Series has an age of Late Triassic or Early Jurassic. Isotope age determination by Tilton and others (1957) and Hurley and others (1960) yields an age of 180 m.y. [It is unclear how 180 m.y. translates into Late Triassic or Early Jurassic. The ages of the Conway Granite, Mount Osceola Granite, Mount Lafayette Granite Porphyry, Mount Garfield Porphyritic Quartz Syenite, and the Albany Quartz Syenite are inferred to be Late Triassic or Early Jurassic.]

Source: GNU records (USGS DDS-6; Reston GNULEX).

Radiometric ages of 201 +/-6 Ma and 193 +/-6 Ma were obtained using K-Ar methods on amphibolite from two samples of Mount Garfield porphyritic quartz syenite. Occurs as a long arcuate mass along northwestern edge of White Mountain batholith. Field relations indicate that it intrudes Mount Lafayette granite porphyry.

Source: GNU records (USGS DDS-6; Reston GNULEX).

Mapped together with Albany Porphyritic Quartz Syenite, also of White Mountain Plutonic-Volcanic Suite, as a unit of undifferentiated porphyritic hornblende quartz syenite. Age is Jurassic based on K-Ar amphibolite ages of 201 +/-6 Ma and 193 +/-6 Ma reported by Eby and others (1992), and using time scale of Harland and others (1989). Report includes geologic map, cross sections, and correlation chart.

Source: GNU records (USGS DDS-6; Reston GNULEX).

Used as Mount Garfield Porphyritic Quartz Syenite of White Mountain Plutonic-Volcanic Suite. Included with Albany Porphyritic Quartz Syenite as an unnamed quartz syenite unit. Age changed from Early and Middle Jurassic to Late Triassic(?) and Early Jurassic based on K-Ar isotopic ages of 201 +/-6 and 193 +/-6 Ma (Eby and others, 1992). [Late Triassic(?) age is very tentative and was not included as part of the age of entire White Mountain Plutonic-Volcanic Suite in NH]. Report includes geologic map and correlation chart, and 1:500,000-scale map showing plutons and sample localities for age dating.

Source: GNU records (USGS DDS-6; Reston GNULEX).