(See also C.E. Fritts, 1965, USGS Geol. Quad. Map GQ-427, Geol. Milford quadrangle, scale 1:24,000.) Allingtown Metadiabase. Mainly medium-to fine-grained dark-greenish-gray to dark-gray intrusive metadiabase in chlorite zone and equivalent medium- to fine-grained grayish-green to dark-greenish-gray amphibolite in zone or higher grade metamorphism. Near Connecticut Turnpike contains numerous inclusions of Oronoque Member (new) of Derby Hill Schist 1 to 5 feet thick interlayered with sill-like and gently inclined dike-like bodies of metadiabase 1 to 8 feet thick. Not known to intrude Wepawaug Schist. Age is Ordovician(?).

Source: US geologic names lexicon (USGS Bull. 1350, p. 16-17).

Pg. A30-A32. Allingtown Metadiabase. Formal proposal of name. Burger (unpub. thesis, 1962) made threefold division of Milford Chlorite Schist. He called a southeastern unit Savin Schist (new). This unit extends southwestward across northwest Woodmont quadrangle and into Milford quadrangle where it is interpreted as Derby Hill Schist. Burger's central unit, Allingtown Formation, consists of abundant meta diabase intruded into phyllitic metasedimentary rocks. Unit extends southwestward into southeast corner of Ansonia quadrangle [this report; USGS Geol. Quad. Map GQ-426, 1965] and into Milford quadrangle [USGS Geol. Quad. Map GQ-427, 1965], where the metasedimentary rocks are separately mapped as Oronoque Member of Derby Hill Schist. Burger's northwestern unit, which includes rocks mapped by Holdway (unpub. thesis) near Maltby Lakes Reservoirs in New Haven quadrangle, consists mainly of metavolcanic rocks but contains subordinate metasedimentary rocks and minor intrusive meta diabase similar to that of Burger's Allingtown. This northwestern unit of predominantly metavolcanic rocks also extends southwestward into Ansonia and Milford quadrangles where it lies above Derby Hill Schist and unconformably below Wepawaug Schist. In present report name Maltby Lakes Volcanics is used for the metavolcanic rocks and Allingtown Metadiabase only for intrusive metadiabase or metabasalt which is probably younger than both Derby Hill Schist and Maltby Lakes Volcanics. Type locality designated. Age is probably Ordovician.
Type locality: community of Allingtown, just southwest of city of New Haven on U.S. Highway 1 [New Haven 7.5-min quadrangle, New Haven Co.], central southern CT.
[Additional locality information from USGS GNIS database and USGS historical topographic map collection TopoView, accessed July 29, 2018. Variant spelling Allington on some topographic maps, ca. 1976-1980 ed. Allingtown is U.S. Board on Geographic Names approved spelling.]

Source: US geologic names lexicon (USGS Bull. 1350, p. 16-17).

Pg. 4 (fig. 3), 8-9. Allingtown Volcanics. Proposed for all rocks extending from Veterans Hospital to intersection of Derby Avenue and Forest Road, western part of New Haven quadrangle. Three rock types constitute main mass of this formation: a massive porphyroblastic greenstone, and a schist that is very similar to the predominant lithology of Savin Schist. Base of formation arbitrarily designated as first appearance of massive, porphyroblastic greenstone in a thick sequence of interbedded schists and greenstones. Top of formation is selected as last appearance of the porphyroblastic rock on a small hill just north of the small creek at the junction of Derby Avenue and Forest Road. Massive rocks in this formation are identified as Allingtown Metadiabase on geologic maps of Ansonia and Milford quadrangles, where Fritts (1965a,b) considers them intrusive. Field evidence shows that the three rock types mentioned are discontinuous and widely interbedded, the schists being present throughout the unit. These facts and parallelism of contacts of the various rock types and the unit as a whole suggest an extrusive rather than an intrusive origin for the massive rock types. Allingtown Volcanics as defined in this report includes all of what Fritts mapped as Allingtown Metadiabase and those portions of his Oronoque Member of the Derby Hill Schist that are in contact with the Allingtown Metadiabase. Underlies Maltby Lakes Volcanics. Thickness a little more than 2,000 feet. [Age is Ordovician(?).]

Source: US geologic names lexicon (USGS Bull. 1350, p. 16-17).

Allingtown Metavolcanics of Middle(?) Ordovician age mapped in the Orange-Milford belt of the Connecticut Valley synclinorium in CT.

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