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David S. Harwood

Publications and source records attributed to David S. Harwood.

25 records · Page 2Linked to original sources
USGS1974

Configuration of Precambrian rocks in southeastern New York and adjacent New England from aeromagnetic data

Two aeromagnetic anomalies of regional extent outline two previously unknown buried masses of highly magnetic, probably Precambrian, rocks in southeastern New York and adjacent Vermont, Massachusetts, and Connecticut. The northern mass extends northeastward from Albany, New York, to Bennington, Vermont, where it appears to be buried beneath weakly magnetic Precambrian rocks of the Green Mountains. The southern mass extends north-northeastward from Beacon, New York, through Stissing Mountain, to Copake, New York, and appears to be the buried northeast extension of the Reading Prong. The shape of the Beacon-Copake magnetic anomaly indicates that the source is near the surface and has a sharp boundary, probably a fault, on its northwestern side; the shape also indicates that the source becomes deeply buried to the southeast and thus supports a parautochthonous interpretation for the northern part of the Reading Prong. In southwestern Massachusetts, the highly magnetic Beacon-Copake mass appears to be overstepped on the east by a buried slice of weakly magnetic Precambrian rocks which, in turn, is overstepped on the east by imbricate slices of weakly magnetic Precambrian rocks exposed along the western front of the Berkshire Highlands. Precambrian rocks exposed in the Green Mountains, the Berkshire and Housatonic Highlands, the eastern part of the Hudson Highlands, and the Manhattan Prong have a remarkably lower amplitude magnetic pattern than those in the Adirondack Mountains and the Reading Prong. This difference in magnetic character appears to represent more than different thicknesses of Precambrian rocks and may reflect a different sequence of Precambrian rocks to the east, a lower grade of Precambrian metamorphism to the east, or possibly a reduction in magnetite content in the eastern Precambrian rocks because of Paleozoic metamorphism.

Connecticut, Massachusetts, New York, Vermont↗
USGS1967

Geology of the Arnold Pond quadrangle, Oxford and Franklin Counties, Maine

The Arnold Pond quadrangle lies on the northwest limb of the boundary Mountain anticlinorium (Albee, 1961), a major northeast-trending fold that extends across northern New Hampshire, west-central Maine and adjacent Quebec. The anticlinorium is defined in a regional sense by the Taconic unconformity separating pre-Silurian rocks from the rocks of Silurian and Devonian age. In the western part of the Arnold Pond quadrangle this unconformity is folded and locally faulted. Within the anticlinorium is a thick and highly folded sequence of green salte and quartzite, black slate, mafic and felsic volcanic rocks, and graywacke dated in part as late Middle Ordovician (Harwood and berry, 1967). These pre-Silurian rocks are flanked to the northwest by calcareous slate and limestone, thin lenses of conglomerate, and well-bedded slate and quartzite of Late Silurian to Early Devonian Age. Because the complete section of rocks in the anticlinorium is not exposed in the Arnold Pond quadrangle, the interested reader is referred to the work of Hatch (1963) and Green (1964; in press) in northern New Hampshire; Albee and Boudette (in press), Boucot and others, (1964), Harwood (1966), and Harwood and Sealy, (1967) in west-central Maine; and Marleau (1957; 1959) in adjacent Quebec.

Maine↗
USGS1966

Geology of the Cupsuptic quadrangle, Maine

The Cupsuptic quadrangle, in west-central Maine, lies in a relatively narrow belt of pre-Silurian rocks extending from the Connecticut River valley across northern New Hampshire to north-central Maine. The Albee Formation, composed of green, purple, and black phyllite with interbedded-quartzite, is exposed in the core of a regional anticlinorium overlain to the southeast by greenstone of the Oquossoc Formation which in turn is overlain by black slate of the Kamankeag Formation. In the northern part of the quadrangle the Albee Formation is overlain by black slate, feldspathic graywacke, and minor greenstone of the Dixville Formation. The Kamankeag Formation is dated as 1-ate Middle Ordovician by graptolites (zone 12) found near the base of the unit. The Dixville Formation is correlated with the Kamankeag Formation and Oquossoc Formation and is considered to be Middle Ordovician. The Albee Formation is considered to be Middle to Lower Ordovician from correlations with similar rocks in northeastern and southwestern Vermont. The Oquossoc and Kamankeag Formations are correlated with the Amonoosuc and Partridge Formations of northern New Hampshire. The pre-Silurian rocks are unconformably overlain by unnamed rocks of Silurian age in the southeast, west-central, and northwest ninths of the quadrangle. The basal Silurian units are boulder to cobble polymict conglomerate and quartz-pebble conglomerate of late Lower Silurian (Upper Llandovery) age. The overlying rocks are either well-bedded slate and quartzite, silty limestone, or arenaceous limestone. Thearenaceous limestone contains Upper Silurian (Lower Ludlow) brachiopods. The stratified rocks have been intruded by three stocks of biotite-muscovite quartz monzonite, a large body of metadiorite and associated serpentinite, smaller bodies of gabbro, granodiorite, and intrusive felsite, as well as numerous diabase and quartz monzonite dikes. The metadiorite and serpentinite, and possibly the gabbro and granodiorite are Late Ordovician in age. The quartz monzonite is considered to be Late Devonian. Five tectonic events are inferred from the structural features in the area. The earliest was a period of folding producing tightly-appressed, northeast-trending folds in the rocks of pre-Silurian age. In the second stage the folded pre-Silurian rocks were uplifted, eroded, and truncated to produce a major unconformity between the Middle Ordovician and Lower Silurian rocks. These events constitute the Taconic orogeny. The third tectonic event was a period of folding, probably of Middle Devonian age, that warped the unconformity and overlying rocks into open, gently-plunging, east-trending folds. This period of folding undoubtedly changed the attitude of the early folds in the pre-Silurian units but it did not produce any recognizable, cross-cutting planar features in the older rocks. The fourth tectonic event was a period of igneous intrusion that locally deformed the northeast-trending folds in the pre-Silurian rocks into a macroscopic drag fold plunging at 80 degrees in a direction S.10?w. A north-trending, subvertical slip cleavage was produced locally during this period of Late Devonian (?) deformation. A period of faulting, possibly of Triassic age, dislocated some of the earlier features. The rocks are in the chlorite zone of regional metamorphism, but have been contact metamorphosed to sillimanite-bearing hornfels adjacent to the quartz monzonite stocks. The chemical changes in chlorite, biotite, garnet, cordierite, and muscovite in the chlorite, biotite, andalusite, and sillimanite zones have been-studied by optical and x-ray methods and by partial chemical analyses. The progressive changes in mineral assemblages have been graphically portrayed on quaternary diagrams and ternary projections.

Open-File Report↗