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DISCLAIMER Before visiting any of the sites described in the New England Intercollegiate Geological Conference guidebooks, you must obtain permission from the current landowners. Landowners only granted
DISCLAIMER Before visiting any of the sites described in the New England Intercollegiate Geological Conference guidebooks, you must obtain permission from the current landowners. Landowners only granted permission to visit these sites to the organizers of the original trips for the designated dates of the conference. It is your responsibility to obtain permission for your visit. Be aware that this permission may not be granted. Especially when using older guidebooks in this collection, note that locations may have changed drastically. Likewise, geological interpretations may differ from current understandings. Please respect any trip stops designated as no hammers, no collecting or the like. Consider possible hazards and use appropriate caution and safety equipment. NEIGC and the hosts of these online guidebooks are not responsible for the use or misuse of the guidebooks. NEW ENGLAND INTERCOLLEGIATE GEOLOGICAL CONFERENCE GUIDEBOOK 55th Annual Meeting October 4-6, 1963 Providence, Rhode Island Univiersity of New Hampshire Library m mi m 1 1 IT 1 1!t;r If cue's' t^ 76.2 'QB t. ^ NETGC MEETINGS, 1963, PROVIDENCE, RHODE ISLAND TABLE OF CONTENTS Introduction - Alonzo W. Quinn 1 PAGE Brief View of Rhode Island Geology - Alonzo W. Quinn 1 Main Groups of Rocks 1 Age Relations 1 Older (?) Gneisses 3 Blackstone Series 3 Plutonic Rocks of Central and Southwestern Rhode Island, Scituate Group 3 Plutonic Rocks of Northeastern Rhode Island 4 Mississippian (?) Plutonic-Volcanic Series 4 Pennsylvanian Rocks of Narragansett Basin 4 Pennsylvanian or Post-Pennsylvanian Rocks 5 References 6 General References 6 Geologic Quadrangle Maps of Rhode Island 7 Trip A - Progressive Metamorphism of Pennsylvanian Rocks; Relations to Older and to Younger Rocks - Alonzo W. Quinn 10 Itinerary 10 References 15 Trip B - Sedimentary and Structural History of Narragansett Basin-Thomas A. Mutch and Sam L. Agron 17 General Discussion 17 Itinerary 20 References 25 Trip C - Glacial Geology, Providence to Point Judith - J. P. Schafer 34 Map Coverage 34 Itinerary 34 References 38 ii m PAGE Trip D - Plutonic Rocks of Northern Rhode Island - Alonzo W. Quinn 40 Itinerary 40 References 42 Trip E - Geology of Cliff Walk, Newport - Thomas A. Mutch 43 Introduction 43 Itinerary 43 References 44 Trip F - Structural Study of Drag Folds, Cleavage, etc., Conanicut Island, Beavertail - William M. Chappie 47 Trip G - Westerly Granite and Related Rocks of the Westerly-Bradford Area - Tomas G. Feininger 48 Introduction 48 Modes 49 References 49 Other References 49 NEW ENGLAND INTERCOLLEGIATE GEOLOGICAL CONFERENCE GUIDEBOOK - 55th Meeting Providence^ R. I., October 4-6, 1963 ERRATA p. 4, line 33 - Maskechugg should be Maskerchugg. p. 17, line 13 - quarts should be quartz. p. 21, last line- east should be west. p. 24, line 12 - Bear sharp left should be sharp right. p. 31, Figure B-7a - arrows reversed, p. 38, first reference - Kay should be Kaye. p. 40, 6th line from bottom - the should be at. p. 42, 2nd reference - from should be iron, p. 47, 2nd line - Veavertail should be Beavertail. p. 49, line 1 - Conncecicut should be Connecticut. PAGE Trip D - Plutonic Rocks of Northern Rhode Island - Alonzo W. Quinn 40 Itinerary 40 References 42 Trip E - Geology of Cliff Walk, Newport - Thomas A. Mutch 43 Introduction 43 Itinerary 43 References 44 Trip F - Structural Study of Drag Folds, Cleavage, etc., Conanicut Island, Beavertail - William M. Chappie 47 Trip G - Westerly Granite and Related Rocks of the Westerly-Bradford Area - Tomas G. Feininger 48 Introduction 48 Modes 49 References 49 Other References 49 Itinerary 50 Trip H - Structural Geology of Woonsocket and North Scituate Basins - Henry T. Hall 53 General Discussion 53 Itinerary 54 References ILLUSTRATIONS Figure 1 - Index map of Rhode Island PAGE Figure 2 - Geologic map of Narragansett Basin 9 Figure Al - Geologic map of Natick area 16 Figure Bl - Geologic sketch map of Newport and vicinity 26 Figure B2 - Sketch map of vertical beds within Rhode Island Formation at Stop B-1 27 Figure B3 - Orientation of plant fragments within Rhode Island Formation at Stop B-2 28 Figure B4 - Geologic map of east shore of Sachuest Point, Aquidneck Island, Rhode Island 29 Figure B5 - Stop 4, Purgatory; index map and section 30 Figure B6 - Stop 4, Purgatory; schematic section 31 Figure B7 - Stop 4, Purgatory; elongated boulders 31 Figure B8 - Stop 4, Purgatory; sheared boulder 32 Figure B9 - Stop 4, Purgatory; magnetite in sandstone 32 Figure BIO- Geology at Stop B-5 33 Figure CI - Sketch map of eastern and southern Rhode Island showing localities for glacial trip 39 Figure El - Estates on Cliff Walk and vicinity 45 Figure E2 - Geology of Cliff Walk 46 Figure Gl - Westerly Granite bodies in Westerly-Bradford area 52 Figures HI, 2, 3 - Geologic structures of North Scituate and Woonsocket Basins 56 XV . INTRODUCTION Alonzo W. Quinn, Brown University In planning the 1963 trips of the NEIGC the leaders decided that we should pick out those features of Rhode Island that are most different from those of other parts of New England. For that reason, the two bedrock trips on Saturday will be concerned with some aspects of the Narragansett Basin, a nearly unique major feature of New England geology. Likewise, the glacial trip of Saturday will provide an opportunity to study some glacial features in the vicinity of Point Judith that are somewhat different from the common glacial features of New England The Sunday trips will include a considerable variety of features, some of which are matched elsewhere in New England. However, some of these also are nearly unique in New England geology. The Narragansett Basin occupies a place of considerable significance in southeastern New England geology. The significance lies partly in the fact that it is the largest mass of sedimentary rocks of known Pennsylvanian age in the New England area. Consequently, the character of these rocks provides the best evidence concerning the sedimentary and tectonic conditions prevailing in New England during the Pennsylvanian Period. In addition, these rocks were intensely deformed, and also metamorphosed, in the Appalachian orogeny, so that they provide evidence concerning that orogenetic episode. Still further, the plant fossils provide one of the few definite geologic ages in southeastern New England. Altogether, these rocks contain much evidence that can be used to elucidate the geologic history of this part of New England. Some of the evidence is known and has been interpreted; much is still obscure and the interpretations are yet to be made. BRIEF VIEW OF RHODE ISLAND GEOLOGY The Narragansett Basin rocks are the only rocks of known age in Rhode Island, but most of the other rocks can be given relative ages with respect to the Narragansett Basin rocks and to each other. Furthermore, most of the many different stratigraphic units can be gathered into several groups. MAIN GROUPS OF ROCKS These main groups are: (1) older(?) gneisses of north central Rhode Island, (2) the Blackstone Series of Precambrian(?) age, (3) the Scituate Group of central and southwestern Rhode Island, (4) the plutonic rocks of northeastern Rhode Island, (5) the Quincy granite and the East Greenwich Group of Mississippian(?) age, (6) the Pennsylvanian rocks of the Narragansett Basin, and (7) the Pennsylvanian or post-pennsylvanian granitic rocks of southern Rhode Island. Age Relations Geological ages of the Rhode Island rocks have been assigned on the basis of evidence outlined below. 1- . The rocks of the Narragansett Basin, group (6), seem rather definitely to be Pennsylvanian, on the basis of identification of plant fossils by older paleobatanists and by Knox in The geological evidence for group (7) being Pennsylvanian or post-pennsylvanian seems strong. The Narragansett Pier Granite intruded Pennsylvanian conglomerate and the Westerly Granite intruded the Narragansett Pier Granite. (Nichols GQ 91; Quinn, and others 1957) The Mississippian(?) age of group (5) is based partly on the giant conglomerate in the Blue Hills area of Massachusetts, where boulders of the granite porphyry are contained in Pennsylvanian conglomerate of the Norfolk Basin. The evidence for the East Greenwich Group is not so clear-cut, but this group appears to be overlain unconformably by the Pennsylvanian rocks. Thus, in both places the Pennsylvanian rocks set an upper limit. The Quincy granite intruded the Esmond granite, and the Spencer Hill Volcanics of the East Greenwich Group contain boulders of the Esmond Granite. (Quinn GQ 17) The Esmond, when previously assigned to the Devonian, made a Mississippian age of group (5) almost necessary. However, this Devonian age is not now firmly established. Group (4), plutonics of northeastern Rhode Island, seems, in part at least, to be younger than group (3) the Scituate group . (Quinn GQ 13) However, there is no very good evidence of any large difference of age of the two groups; they may belong to the same general episode of granitic intrusion. The Esmond Granite, which is one of the youngest of both groups, is overlain unconformably by Pennsylvanian rocks at Natick, R. I. and it is older than the Quincy granite. It was also exposed to erosion before the formation of the pre-pennsylvanian Spencer Hill Volcanics of East Greenwich. This all indicates that these plutonic rocks are at least two fairly long erosion intervals earlier than the Pennsylvanian rocks Definitely older than both plutonic groups, (3) and (4), is the Blackstone Series, group (2). This has been assigned a Precambrian(?) age, but the evidence is not strong. (Quinn, Ray, and Seymour GQ 1) They appear to be more metamorphosed than are the f ossiliferous Cambrian rocks at Hoppin Hill in Massachusetts. The above history of the plutonic groups was preceded by the deposition and deformation of perhaps 20,000 feet of sediments and volcanics of the Blackstone Series. This suggests at latest a medial Paleozoic or an early Paleozoic age for the Blackstone Series; a Precambrian age is plausible. Richmond ( GQ 16) mapped a complex structure for the older(?) gneisses, group (1), and stated that they are unconformable beneath the Blackstone Series. The evidence is meager, but neither has any opposing evidence been discovered. All of the above evidence is consistent with the following sequence of events: (I) older gneisses were formed and then deformed in an early orogeny, (II) Blackstone Series deposited, deformed, metamorphosed, and intruded by the two plutonic series (groups (3) and (4) ), this orogeny being the Taconic or the Acadian, (III) erosion of older rocks and the formation of volcanics and plutonics of group (5), (IV) erosion of older rocks and deposition of Pennsylvanian rocks of the Narragansett Basin, and (V) deformation of Narragansett Basin rocks and intrusion of group (7), this being the Appalachian orogeny. The few average ages based on radioactivity are: Quinn and others, 1957; Hurley and others, lead- ., (Quinn GQ 13, Moore GQ 105) These appear to be largely of syntectonic relations, as is indicated by their gneissic structure. They are intrusive into the Blackstone Series, and the Scituate granite gneiss has been intruded by the Esmond Granite These plutonic rocks appear to represent the late stages of an orogeny that deformed and metamorphosed the Blackstone Series. The earliest members of the series have well-developed foliation, whereas the latest members are more nearly massive. The mineral composition also varies in a common systematic way, from quartz diorite early to granite or alaskite late. Plutonic Rocks of Northeastern Rhode Island The main plutonic rocks of northeast Rhode Island are intrusive into the Blackstone Series and the Esmond Granite has intruded the Scituate Granite Gneiss. These include several quartz diorites, the Grant Mills Granodiorite and the Esmond Granite. (GQ 1) They are moderately large discordant intrusives. These rocks generally are less foliated than are rocks of the Scituate Group. Therefore, the northeastern plutonic rocks probably represent a later stage in an orogenic cycle, possibly the same cycle, than does the Scituate Group. The plutonic rocks on the east side of the bay and in the Newport vicinity bear no close similarity to anything on the west side and their ages are unknown except they are older than the Pennsylvanian rocks of the Narragansett Basin and younger than the schists of Tiverton, Sakonnet, and Newport. These include the Metacom Granite Gneiss of Bristol and Tiverton, granite exposed widely from Tiverton to Sakonnet Point, and coarse porphyritic granite of Newport and Conanicut Island. They may or may not be equivalent to some of the plutonic rocks on the west side of the bay. Mississippian(?) Plutonic-Volcanic Series In the northeast part of Rhode Island are several bodies of riebeckiteaegirite Quincy granite and an associated granite porphyry. These are rather small intrusive bodies. (GQ 1) In central Rhode Island, just west of East Greenwich, is a mass of volcanic rocks and intrusive rocks, the East Greenwich Group. (GQ 17) These seem to have the same relations as has the Quincy Granite. Included here are the Spencer Hill Volcanics, the Maske'chugg Granite, a granite porphyry, and the Cowesett Granite Pennsylvanian Rocks of Narragansett Basin The Narragansett Basin is a complex synclinal mass of Pennsylvanian sedimentary rocks, perhaps as much as 12,000 feet thick. They are almost all clastic rocks of non-marine origin. Conglomerate, sandstone, arkose, graywacke, shale, and siltstone were the chief sedimentary rocks. In addition, there were numerous coal beds and very minor lenses of limestone. A few layers of felsite and also basalt are exposed in the northwestern part of the Narragansett Basin (in Massachusetts). Most of the Pennsylvanian rocks are gray to black, but the Wamsutta Formation in the northwest is red. All of these rocks are firmly indurated and those to the south are progressively metamorphosed. The formations included are the Pondville Conglomerate, the Wamsutta Formation, the Rhode Island Formation, and the Dighton Conglomerate. . Two small outliers of probable Pennsylvanian rocks are the North Scituate Basin and the Woonsocket Basin, both about six miles west of the Narragansett Basin. Pennsylvanian or Post -Pennsylvanian Rocks Younger than the Pennsylvanian rocks of the Narragansett Basin are the Narragansett Pier Granite and the Westerly Granite. These both occur in the southern part of the state, the Narragansett Pier Granite chiefly as a large mass of medium-grained red granite and the Westerly chiefly as south-dipping dikes of fine-grained gray granite (G-1 Fairbairn and others 1951). The Bradford dike is about 65 feet thick, dips 28 south, and extends for over a mile and a half. Many other dikes of the Westerly Granite are smaller and some are irregular in shape In addition to the above are several mafic dikes, some cutting the Westerly and some the Pennsylvanian rocks of the Narragansett Basin. A mass of gabbro in the west central part of the state appears to be unaffected by deformation, so it, too, may belong to the Pennsylvanian or post-pennsylvanian group. -5- . REFERENCES This guidebook contains a list of general references and also more specific references for each trip. In addition, references to recent mapping are presented in the form of (a) an index map showing locations of quadrangles and (b) a list of quadrangle reports (mostly GQ maps) published and in preparation. These quadrangle reports resulted from a cooperative program between the U. S. Geological Survey and the R. I, Development Council (and its predecessor agencies) GENERAL REFERENCES Emerson, B. K., 1917, Geology of Massachusetts and Rhode Island: U. S. Geol. Surv., Bull. 597, 389 p. Fairbairn, H. W., and others, 1951, A cooperative investigation of precision and accuracy in chemical, spectrochemical, and modal analysis of silicate rocks: U. S. Geol. Surv., Bull. 980, 71 p. (Westerly granite). Jackson, C. T., 1840, Report on the geological and agricultural survey of the State of Rhode Island, 312 p. Knox, A. S., 1944, A carboniferous flora from the Wamsutta formation of southeastern Massachusetts: Am. Jour. Sci., v. 242, p Quinn, Alonzo W., 1953, Bedrock geology of Rhode Island (abstract): N. Y. Acad. Sci., Trans., v. 15, p Quinn, Alonzo W., Jaffe, Howard W., Smith, W. L., and Waring, C. L., 1957, Lead-alpha ages of Rhode Island granitic rocks compared to their geologic ages: Am. Jour. Sci., v. 255, p Quinn, Alonzo W. and Oliver, W. A., Jr., 1962, Pennsylvanian rocks of New England, Chapter in a volume on Pennsylvanian system in the United States , p , by the American Assoc. Petroleum Geologists. Quinn, Alonzo W. and Swann, D. H., 1950, Bibliography of the geology of Rhode Island, 2nd ed. : R. I, Port and Indus. Comm., 26 p. Shaler, N. S., Woodworth, J. B. and Foerste, A., 1899, Geology of Narragansett Basin: U. S. Geol. Surv., Mon. 33, 402 p. GEOLOGIC QUADRANGLE MAPS OF RHODE ISLAND ni oo' 5CALE 7I J0' Figure 1 Index map of Rhode Island T4-2-'lS' 70'45 LEGEND Igtieeus an^ Metamor-phic RocJ 5 POST PEMNSYLVANIAN gran-t* lonriles GEOLOGIC MAP OF THE NARRAGANSETT BASIN Modified from Qainrv and OI[ver,l1b Figure 2 Geologic map of Narragansett Basin; from Emerson, 1917, later published maps, and unpublished maps by G. E. Moore. Jr., L. J. Rusling, S. J. Pollock, G. H. Springer, and R. B. Williams. A-2, B-2, etc. - stops or general locations of field trips ., TRIP -A PROGRESSIVE MElAMORPHiSM OF PENNSYLVATEIAN ROCKS; RELATIONS TO OLDER AND TO YOUNGER ROCKS Alonzo W. Quinn, Brown University Itinerary The main emphasis of Excursion A will be on progressive metamorphism of Pennsylvanian sedimentary rocks of the Narragansett Basin, but the localities visited will provide opportunity to observe such additional features as sedimentary structures of the Pennsylvanian rocks, unconformable relations of the underlying pre-pennsylvanian rocks, and intrusive relations of Pennsylvanian or post-pennsylvanian granitic rocks. The excursion will go from north to south along the western margin of the Narragansett Basin. Because of the expected size of crowds, only a few localities are suitable; several localities at intermediate positions in progressive metamorphism cannot be visited. STOP 1 - Southern edge of Attleboro, Mass, just SW of Thacher St. crossing of N. Y., N. H., and H. Railroad, Attleboro Quadrangle. This locality is most interesting for the sedimentary structures, channel fills, cross-bedding, etc. The rocks here probably should be assigned to the Rhode Island Formation, although some beds of red rocks like the Wamsutta Forination are exposed. Ides Hill, just west, is the smallest of the three synclines of Dighton Conglomerate, which is youngest of the Pennsylvanian formations here. There may be difference of opinion about whether these rocks are metamorphosed. At any rate, these are about as low on the metamorphic scale as are any Narragansett Basin rocks. The clasts are chiefly quartz, feldspars, and lithic fragments, along with common accessory minerals. Micas are common, but they appear to be detrital. The clastic grains are sharp, randomly oriented, and apparently undeformed. Log from Thacher St. locality: Miles 00.0 West on Thacher St. 0.4 Rte Continue West on Under Rte. 95 (if this piece of Rte. 95 is open by October 5 we will go south on ir, with consequent modification of road log). 3.7 Traffic light, left on la. 4.7 Right onto Rce. 95 ('south). 6.0 Rhode Island State line; passing through Pawtucket, main center on right 6.7 On left is road-cut in black shale and gray sandstone of Rhode Island Formation. 7.7 Crossing Blackstone River, rapids just upstream. Blackstone here has cut small rock gorge, having been diverted by ice block from former open valley. Acres of broken rock (R. I. Formation) from Rte. 95 excavation. Continue south to s
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