- Usage in publication:
-
- Lafayette granite porphyry
- Modifications:
-
- Original reference
- Dominant lithology:
-
- Granite
- AAPG geologic province:
-
- New England province
Williams, C.R., 1934, Geology in the Franconia region: Appalachia, v. 20, no. 4, p. 69-78.
Summary:
Pg. 69-78. Lafayette granite porphyry. Dark-gray or green rock. Extends length of Franconia Ridge trail from Mount Lafayette [in Franconia quadrangle, Ammonoosuc River region, northwestern New Hampshire] to Little Haystack [etc.]. Age is late Carboniferous(?).
[M.P. Billings and C.R. Williams in 1935 changed this name to Mount Lafayette granite porphyry, and assigned the formation to White Mountain magma series of Billings.]
Source: US geologic names lexicon (USGS Bull. 896, p. 1129).
- Usage in publication:
-
- Mount Lafayette granite porphyry
- Modifications:
-
- Revised
- Dominant lithology:
-
- Granite
- AAPG geologic province:
-
- New England province
Summary:
Originally called Lafayette granite porphyry. Changed name to Mount Lafayette
Named for Mount Lafayette, Franconia 15-min quad, northwest NH. Occupies much of Franconia quad and is exposed on Mount Lafayette. Assigned to White Mountain magma series. Consists of hard, massive, gray or green rock. Main body is 10 mi long and 3 mi wide and extends to the southwest from Mount Hale to Mount Flume. Cuts Kinsman quartz monzonite and is older than Mount Garfield quartz syenite and Mount Osceola granite. Age is late Devonian or late Carboniferous.
Source: GNU records (USGS DDS-6; Reston GNULEX).
- Usage in publication:
-
- Mount Lafayette Granite Porphyry*
- Modifications:
-
- Age modified
- Geochronologic dating
- AAPG geologic province:
-
- New England province
Summary:
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).
- Usage in publication:
-
- Mount Lafayette granite porphyry
- Modifications:
-
- Geochronologic dating
- AAPG geologic province:
-
- New England province
Summary:
Radiometric age of 195 +/-6 Ma obtained using K-Ar methods on amphibolite. Occurs as a ring dike and as a large, kidney-shaped mass along western edge of batholith. Field relations indicate intrusion by Mount Garfield porphyritic quartz syenite.
Source: GNU records (USGS DDS-6; Reston GNULEX).
- Usage in publication:
-
- Mount Lafayette Granite Porphyry*
- Modifications:
-
- Age modified
- Geochronologic dating
- AAPG geologic province:
-
- New England province
Summary:
Mount Lafayette Granite Porphyry of the White Mountain Plutonic-Volcanic Suite is mapped with similar rocks as a unit of undifferentiated hornblende granite porphyry. Combined with other rocks of Jurassic age. Jurassic age of Mount Lafayette is based on Rb/Sr whole-rock isochron of about 195 Ma, 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).
For more information, please contact Nancy Stamm, Geologic Names Committee Secretary.
Asterisk (*) indicates published by U.S. Geological Survey authors.
"No current usage" (†) implies that a name has been abandoned or has fallen into disuse. Former usage and, if known, replacement name given in parentheses ( ).
Slash (/) indicates name conflicts with nomenclatural guidelines (CSN, 1933; ACSN, 1961, 1970; NACSN, 1983, 2005, 2021). May be explained within brackets ([ ]).