We are planning all-day field trips for Saturday, August 28, 1999. These day-long trips will offer visitors an opportunity to visit sites of interest in the Southern New England area, and to discuss geochemical problems in the field with experts on aspects of the regional geology. All trips will depart from and return to the Department of Earth and Planetary Sciences at Harvard. Van transport and box lunches will be provided. Preregistration will be required, on a first-come-first served basis. Trips 1, 2, 3, and 4 will be limited each to 40 people and trip 5 will be limited to 50 people. We will not be publishing a combined field trip guidebook, but each trip will have its own writeup. The cost will be $100 per participant. The final announcement will contain further details on these trips, as will the conference Web page. If you have questions or suggestions relating to the program format for the field trips, please contact the Field Trip Chair, Mark VanBaalen, mvb@harvard.edu.

1. Geochronology and Geochemistry of the Shelburne Falls Arc and the Taconian Orogeny in Western New England.

(Paul Karabinos, Williams College and Chris Hepburn, Boston College)

 We will visit spectacular and scenic exposures of the arc, forearc, accretionary complex, and continental margin deformed during the Ordovician Taconian orogeny. Participants are encouraged to bring along a bathing suit. Stop 1- The 475 Ma plutonic core of the Shelburne Falls arc is beautifully exposed in potholes along the Deerfield River in the lovely town of Shelburne Falls. Stop 2- Volcanic rocks with deformed pillow structures make up part of the Hawley Formation along the Chickley River. These volcanics are probably part of a relict forearc basin. Stop 3- The 447 Ma Middlefield Granite intruded rocks in the hangingwall and footwall of a Taconian thrust but is not offset at the contact. Thus, it helps date the end of the Taconian orogeny. The intrusive contact between the Middlefield Granite and the Moretown Formation, which is part of the forearc basin, is spectacularly exposed at Glendale Falls. Stop 4- Mafic and ultramafic rocks are widely distributed in the Rowe Schist, interpreted as part of the accretionary complex. We will examine part of the largest ultramafic body in Massachusetts along the Westfield River. Stop 5- The Middle Proterozoic basement rocks of the continental margin are unconformably overlain byLate Proterozoic rift clastics. We will hike a short stretch of the Appalachian National Scenic Trail to see the unconformity beautifully exposed on Day Mountain in Dalton. This extraordinary outcrop has caused many hardened geologists to weep.

 Departure Time and Location: 0800 at the EPS Dept., Harvard. Travel will be in vans. We will return to Harvard by approximately 2100. As noted in the above description, swimming is a possibility, so plan to bring along a bathing suit. Trip is limited to 40.

2. Neoproterozoic Stratigraphy in and Around the Boston Basin.

(Meg Thompson, Wellesley College)

 Neoproterozoic rocks in and around the Boston Basin of eastern Massachusetts record Avalonian arc magmatism between ca. 610 and 590 Ma and associated sedimentation in arc-related extensional basins. Representative magmatic units to be visited on this trip will include ca. 599 Ma Westwood Granite, cross-cutting quartz diorite (ca. 589 Ma) and ca. 596 Ma caldera-filling ash-flow tuff of the Mattapan Volcanic Complex. Sedimentary units to be visited will include boulder beds comprising the Brookline Member of the Roxbury Conglomerate and the Squantum "Tillite" Member which contains glacial deposits that can be constrained by interbedded lava flows of the Brighton Volcanics. Also to be highlighted is argillite overlying the Roxbury Conglomerate in which Aspidella has recently been reported. Time and interest permitting, we may return via the Blue Hills where ongoing U/Pb zircon geochronology indicates that the post-Avalonian, alkalic Quincy Granite is younger than the published Ordovician age.

 Departure Time and Location: 0800 at the EPS Dept., Harvard. Travel will be in vans. We will return to Harvard by approximately 1800.

3. Glacial Geology and Hydrology of Block Island.

(Les Sirkin, Adelphi University)

 The Block Island trip will investigate stratigraphic and structural evidence of two glacial advances in the late Pleistocene end moraine region. It will evaluate stratigraphic and geomorphic evidence of glacial recession, including recessional moraines, proglacial lakes, drumlins, late-glacial fluvial erosion, and sea level rise. The development and utilization of groundwater resources in the glacial aquifers will also be demonstrated. Stops will include exposures in the 140 ft high Mohegan Bluffs, the Beacon Hill Recessional Moraine, the mid-Island drumlin field and proglacial lake, the Corn Neck Recessional Moraine and the Island well field and water treatment plant.

 Preliminary references: Sirkin, Les, 1994, Block Island Geology; Veeger and Stone, USGS WRI Report 94-4096.

 Departure Time and Location: 0700 at the EPS Dept., Harvard, for the bus trip to the Block Island ferry at Galilee, Rhode Island (ferry leaves at 0900). We will return to Harvard by approximately 2000. The trip is limited to 40.

4. Geological, Geochemical, and Environmental Aspects of Metamorphosed Black Shales in New England.

(Charles V. Guidotti, University of Maine; Mark Van Baalen, Harvard University)

 The belt of metamorphic rocks in Central New England records a complex tectonometamorphic history during the Paleozoic. Many, but not all of the metasediments in the belt are of Silurian age. Included among the metasediments are some sulfidic schists that are interpreted as metamorphic products of marine black shales. Study of their mineral chemistries, assemblages, and field relations can provide important clues on ancient depositional basins and the subsequent tectonometamorphic processes. This field trip will visit a set of key outcrops in Central Massachusetts and Western New Hampshire that document some of the unusual features of these sulfur + graphite-rich rocks. Points to be discussed during the trip include the following: (1) Based upon the trace element concentrations (e.g. V, Ba, Se, Sb, As) in the silicate and sulfide mineral assemblages, we suggest original depositional environments in strongly reducing to anoxic basins. (2) Chemical signatures indicating a high degree of anoxicity in sedimentary basins may be preserved through high-grade metamorphism. (3) Extensive sulfide-silicate reactions during diagenesis and metamorphism affect such rocks strongly. (4) These reactions impact the silicate-bulk-composition and hence the silicate and opaque mineral assemblages that form during metamorphism. They also impact the compositions of the silicate phases. (5) More recently, the implications for water quality in bedrock water wells with respect to toxic elements, especially As, have brought additional attention to these rocks from the environmental community.

 The field trip will depart from the Earth and Planetary Sciences Department at Harvard at 0800 on Saturday, August 28, and will return there by 2100 on the same day. Travel will be by vans, and box lunches will be provided. We will also stop for dinner in the early evening on the way back to Cambridge. No strenuous hiking will be involved, but sturdy foot gear is advised. The trip is limited to 40 participants.

5. Open House at the Woods Hole Oceanographic Institution. (John Hayes and N. Shimizu, Woods Hole Oceanographic Institution)

 Participants on trips 1-4 are required to bring outdoor clothing and rain gear. Trip 3 involves a one-hour trip on a ferry boat each way from Block Island. Approximately 6 hours will be spent outdoors. There will be no strenuous climbing or hiking. Temperatures in the field are expected to be 20º-30º C (68º-86º F) in August.

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