Ages of the Rye Complex, Coastal NH: A Deformational History Slowly Revealed

BOTHNER, KANE, STOESZ, SOROTA, LAIRD, HUSSEY, DORAIS, WINTSCH, HEPBURN, KUNK

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AGES OF THE RYE COMPLEX, COASTAL NH: A DEFORMATIONAL HISTORY SLOWLY REVEALED

By

Wally Bothner, Department of Earth Sciences, University of New Hampshire, Durham, NH 03824

Patrick Kane, Department of Geological Sciences, Indiana University, Bloomington, IN 47405 Erin Stoesz, Wyoming Carbon and Storage Technology Institute, University of Wyoming, Laramie, WY 82071

Kristin Sorota, Earth and Environmental Sciences, Boston College, Chestnut Hill, MA 02467 Jo Laird, Department of Earth Sciences, University of New Hampshire, Durham, NH 03824

Art Hussey, Department of Geology, Bowdoin College, Brunswick, ME 04008 Mike Dorais, Department of Geological Sciences, Brigham Young University, Provo, UT 84602 Bob Wintsch, Department of Geological Sciences, Indiana University, Bloomington, IN 47405 Chris Hepburn, Earth and Environmental Sciences, Boston College, Chestnut Hill, MA 02467

Mick Kunk, US Geological Survey, MS 926A, National Center, Reston, VA 20192

INTRODUCTION

The Rye Complex is an enigmatic package of highly deformed pelitic, felsic, and mafic schists and gneisses metamorphosed to middle and upper amphibolite facies conditions andalusite/staurolite and sillimanite grade (eg., Stop 4 of Swanson and Carrigan, 1984). The Portsmouth Fault Zone everywhere bounds the Rye on the west from the lower grade feldspathic metasandstones and metashales of the Kittery Formation, the basal unit of the Merrimack trough (Figure 1; Hussey et al., 2008). Protoliths of the Rye include aluminous and carbonaceous shale, calcareous siltstone, feldspathic and argillaceous sandstone, minor limestone, and mafic volcanic and volcanoclastic rocks. The package is highly migmatized, variably mylonitic, and intruded by melts of felsic and intermediate composition that are, except for widespread Mesozoic dikes, also variably foliated. This trip visits a number of outcrops that were parts of earlier NEIGC and GSA trips led by Robert Novotny (1956), Mark Swanson and John Carrigan (1984), and Art Hussey and Wally Bothner (1993 and 1995) and builds on those studies with new descriptions and interpretations. Exposures of the Rye Complex dominate the ~25 km long New Hampshire coastline and southwesternmost Maine (Hussey et al., 2008; Escamilla-Casas, 2003). It forms all of the rocky headlands north of Hampton Beach, many of the islands of New Castle and Portsmouth harbors in New Hampshire (Carrigan, 1984a), all of Gerrish Island in Kittery, ME (Hussey, 1980; Swanson, 1988), the Isles of Shoals (Fowler-Billings, 1959; Blomshield, 1975), Boon Island (Bothner, unpublished notes, 1983), and the sea bottom in between (Brooks, 1986; Brooks and Bothner, 1988; Bothner et al., 1988). The Isles of Shoals and Boon Island are dominated by strongly foliated, gray granitic gneisses, commonly with mappable enclaves of aligned pelitic schist, amphibolite, and minor calc-silicate granofels, lesser amounts of through-going coarse-grained blastomylonitic quartzofeldspathic gneiss, and, on Appledore Island, weakly foliated cross-cutting diorite. Strong dextral shear fabrics are developed at scales ranging from thin section to outcrop and include boudinage (often preserving shear sense in the shape of mega “sigma”clasts), asymmetric folds, and strong stretching lineations, many features of which are subjects of this trip.

Early attempts to date rock in the Rye Complex were fraught with difficulty because of elemental redistribution/rehomogenization (Rb/Sr), recrystallization, and/or argon loss during deformational and metamorphic events. However, these results did point to pre-Silurian events (Gaudette et al., 1984; West, written communication, 1995). Recent efforts using modern techniques has refined the intrusive, protolith, and metamorphic, deformation and cooling ages preserved in the Rye Complex. These include CA-TIMS analysis of cross-cutting igneous bodies and metaigneous units (Bothner et al., 2009; Hussey et al., in press), LA-ICP-MS analysis of detrital zircons from metasedimentary units (Sorota et al., 2011, 2012; Hussey and Bothner, 2013, Kane et al., 2014;), and 40/39Ar analysis of amphibole, mica, and alkali feldspar in shear zones (Stoesz et al., 2013; West et al., 1988).

Like too many real and apparent ‘engimatic tectonic slices’ of New England, the Rye lies between better

documented terrains (Peri-Gondwana and Avalon) but is in fault contact with them, and is everywhere unfossiliferous. Various models place the complex within the Norumbega fault system (Swanson, 1999; Bothner and Hussey, 1999; Stoesz et al., 2013 among many others). Could it be a slice of Ganderian basement or Ganderian cover? We address this question, among others, herein and on the trip.

BOTHNER, KANE, STOESZ, SOROTA, LAIRD, HUSSEY, DORAIS, WINTSCH, HEPBURN, KUNK A2-2

Figure 1. General geologic map of seacoast New Hampshire and southwestern Maine from the Kittery 100000 sheet (Hussey et al., 2008) and Hampton quadrangle (Escamila-Casas, 2003) showing field stops 1 through 8. P – Hampton NH Park and Drive off Rt. 27; L – lunch stop at the Seacoast Science Center, Odiornes State Park. PFZ – Portsmouth Fault Zone; GCFZ – Great Common Fault Zone. Units: COr – Cambro-Ordovcian rocks of the Rye Complex – Undifferentiated, but often dominated by injected gneisses; bg – blastomylonitic quartzofeldspathic gneiss; a – amphibolite; Sk and Se – Silurian Kittery and Eliot Formations; bh – Devonian Breakfast Hill granite; d – Devonian Appledore and Salamander Point diorites; Dng – Devonian Newburyport granite


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SYNOPSIS OF THE RYE ROCKS – VARIETY AND AGES 600 500 400 300 200 100 Ma _____________________________________________________________________________________________ Unit and method

121 1Cape Neddick gabbro 40/39Ar --------228---------------- > 2Dike swarm intrusions

235-238Ma 3FFBZ pseudotachylite 40/39Ar 238Ma* 4Agamenticus biotite granite4 206Pb/238Uzircon 245Ma 5Rye blastomylonite gneiss 40/39ArMU @~200°C 250Ma 5Rye blastonmytonite gneiss 40/39ArKSP @~250°C 278±40Ma 6GCFZ pseudotachylite Rb/Sr >>>>>>>>>>>>>>>>>>>>>> Mylonitic fabric development begins in the Rye 340Ma 5Rye pegmatite 40/39ArMUpeg@~350°C 361Ma* 7Appledore Island diorite 206Pb/238Uzircon 380Ma* 7Salamander Point diorite 206Pb/238Uzircon 403Ma* 7Breakfast Hill granite 206Pb/238Uzircon 407Ma* 7,8Exeter diorite 206Pb/238Uzircon 418Ma* 8Newburyport quartz diorite 206Pb/238Uzircon 432Ma* 9Kittery detrital zircon (416 Ma LA-ICP-MS) 455Ma* 7Rye quartzofeldspathic gneiss 206Pb/238Uzircon 475Ma 5Rye amphibolite 40/39ArHbl@~500°C 482Ma 10Rye tectonized granitoid LA-ICP-MS det zircon 530Ma 10Rye micaceous quartzite LA-ICP-MS det zircon

623±8Ma 11Massabesic Gneiss Complex U/Pbzircon ion probe

__________________________________________________________________________________________________________ *CA-TIMS 206Pb/238Uzircon, FFBZ – Fort Foster Brittle Zone, GCFZ – Great Common Fault Zone; superscript identifies reference (1Hussey et al., 2008; 2McHone, 1992; 3van der Pluijm, written communication 2008; 4Hussey et al., in press; 5Stoesz et al., 2013; 6Boeckeler, 1994; 7Hussey et al., in press; 8Bothner et al., 2009; 9Sorota, 2013; 10Kane et al., 2014; 11Lyons et al., 1997)

Figure 2 summarizes our present understanding of rock ages and datable events. It represents a concerted effort of many. It is used as a template and the following paragraphs will outline plutonism, structure and metamorphism before and speculations and questions are presented.

PLUTONISM

The Geologic Map of the Kittery 100000 quadrangle (Hussey et al., 2008 and bulletin, in press) illustrates the distribution of recently dated middle and late Paleozoic intermediate to felsic plutonic bodies. They reflect a magmatic continuum (calc alkali to peraluminous) from 407 to 287 Ma beginning in the early Acadian and continuing through Alleghanian. From 238 to 121 Ma several central complexes of the White Mountain Volcanic-Plutonic Series were emplaced in the general area of this fieldtrip. They represent the initiation of rifting and extend through the drift stage of the opening of the Atlantic. These strongly cross cutting bodies are characterized by early alkali felsic and later mafic magmatism. Dikes of varying sizes and small explosion breccias do occur within the Rye Complex proper. Some of the plutons within the Rye Complex are very easily recognized and others are surprisingly more difficult. Typical magmatic identifiers for the older intrusives (cross-cutting contacts, varying magmatic textures, chill margins, and the like) are generally overprinted by deformation fabrics. Contacts are commonly transposed into near parallelism. (Art Hussey (1980) first demonstrated that what had been defined as the metavolcanic member, was in fact a series of felsic intrusives that just barely cross-cut or have been transposed to nearly parallel the dominant foliation.) Middle Paleozoic intrusives maintain many of those primary features because they are less severely deformed, and the youngest Mesozoic bodies are unaffected.


The tourmaline and two-mica bearing granite ‘sills’, associated sheared pegmatites and the Wallis Sands quartzofeldspathic gneiss (Stop 2) are typical examples. The sheared granites and pegmatites are so far undated. The later is a 1-5 m thick, light gray felsic rock that strongly conforms to the dominant NE-trending, subvertical dominant foliation. It contains quartz, altered plagioclase, lesser microcline, and muscovite (Fig 3a). It is tempting to name it a granodiorite, but because of metamorphic overprint we await chemical analyses from this body to be more definitive. Zircons were obtained from this body as part of a detrital zircon study (Kane et al., 2014) because the field character led us to believe we were sampling a sheared mica-bearing feldspathic quartzite; however, a high feldspar content observed in thin section points to a more probable metaigenous protolith, with likely retrograde crystallization of muscovite after feldspar. Zircons extracted from this rock were more equant and stubbier than ‘normal’ detrital grains and LA-ICP-MS analysis of 78 grains generated a single narrow peak with an age of 482 Ma (Fig. 3b). We interpret this rock to be an early Ordovician granitic rock that intruded the older Rye metasedimentary package before major ductile deformation.

a. PPL XPL b. Figure 3. Photomicrograph (a) and detrital zircon population density plot (b) of the Wallis Sands quartzofeldspathic gneiss

Breakfast Hill pluton (Stop 8). The Breakfast Hill granite was recognized by Novotny (1969) as a small lenticular, variably foliated, two-mica granite in western part of the Rye Formation. The gneissic granite is identified as a discontinuous, variably sheared mass as far as Portsmouth Harbor. It is comprised of microcline, plagioclase, quartz, muscovite and biotite in a variably granulated fabric. Early attempts to date this rock using U/Pbsphene were fraught with large errors around a 380 Ma value, but high precision 206Pb/238Uzircon yields an early Devonian age of 402.94±0.19 Ma (Hussey et al., in press).

Salamander Point diorite (Stop 6). Salamander Point diorite crops out irregularly along the northeast shore of New Castle Island, NH, and a little over 1 km to the east in Portsmouth Harbor on Fishing Island in Maine. It appears lenticular in map view, perhaps 1 by .5 km long, and is parallel to the strong northeast-trending foliation in the host Rye “Formation.” It is poorly foliated and injected intimately by fine-grained gray granite, that is also poorly foliated. The diorite contains plagioclase, pale green hornblende, biotite, and quartz, plus accessory sphene, apatite, opaque and zircon. The cross cutting granite has a well granulated, mildly cataclastic texture composed of quartz, perthitic microcline, and minor biotite with exsolved sagenitic rutile and pleochroic haloes around included zircon. Undulatory quartz is not recovered. The diorite at Salamander Point provided a high precision 206Pb/238U age of 380.24±0.26 Ma (Hussey et al., in press).

The Appledore diorite crops out on the northeastern shore of Appledore Island, some 15 km off the NH-

ME mainland. It is included here because the rocks comprising the Isles of Shoals represent an important link to the Rye Complex onshore (Brooks et al., 1988) and because this diorite has many of the same field and petrographic characteristics as the Salamander Point diorite. The Appledore “meta”diorite, as defined by Fowler-Billings (1955), was considered to be part of the Exeter pluton for many years. It had a preliminary Rb/Sr age that was the same as for the Exeter (475±20, Gaudette et al., 1984). A zircon 206Pb/238U age of 361.18±0.13 Ma, some 20 million years younger for this body than the Salamander Point body, and more than 40 m.y younger than the Exeter. This new age distinguishes it from the others and points to a much longer period of intermediate magma generation during the Devonian (Dorais et al., in press).

0 500 1000 1500 2000

Rel

ativ

e pr

obab

ility

Age (Ma)

482 Ma n = 78


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. a. b.

c. d. Rock/Chondrite vs REE

Figure 4a, b and c show a transition from calc-alkaline magmas of the ~400 Ma New Hampshire Plutonic

Suite of the Merrimack Trough to the younger Salamander Point and Appledore Island diorites. The 380 Ma Salamander Point diorite has compositions that are intermediate between the NHSP and the Appledore Island diorite, reflecting the initiation of rift-related magmatism that became fully expressed with the Appledore Island diorite. These within-plate magmas may have resulted from Late Devonian to Carboniferous rifting related to orogenic collapse or from post-Acadian slab breakoff. Figure 4d illustrates the general similarity of REE vs Rock/Chondrite plots between the granites associated with the diorites and the Breakfast Hill (o) spanning some 40 Ma. Nd isotopic compositions from the granite intermingling with the Appledore Island diorite suggest a Ganderian source (Dorais et al., in press).

Ti/100

Zr Y*3

WIP IAT

MORB

IAT

CAB

CAB

= Appledore Island

= Salamander Point

= NHPS

1

10

100

10 100 1000

Zr/Y

Zr

Volcanic-arc

basalts

MORB

Within-plate

basalts

MORB &

volcanic arc

basalts

MORB &

within-plate

basalts

= Appledore Island

= Salamander Point

= NHPS

0.0

0.5

1.0

1.5

2.0

2.5

3.0

45 50 55 60 65 70 75 80

0.0

0.2

0.4

0.6

0.8

1.0

1.2

45 50 55 60 65 70 75 80

SiO2

TiO

2

SiO2

P 2O

5

= Appledore Island= Salamander Point= NHPS

0.1

1.0

10.0

100.0

1000.0

Appledore Island and Breakfast Hill

La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu


STRUCTURE – AGES OF DEFORMATION

With the exception of Mesozoic dikes and explosion breccias, all the metasedimentary, metavolcanic(?),

and metaigneous rocks that comprise the Rye Complex are deformed. Weakly foliated granitic rocks are typified by the Breakfast Hill granite. Strongly foliated pelitic, calcareous and mafic schists and blastomylonitic metaigneous rocks represent an intermediate step in the development of ultramylonites from varying protoliths that characterize the Great Common Fault Zone. The age of ductile motion is constrained to be younger than the 455 Ma blastomylonitic quartzo-feldspathic gneiss and likely active during/shortly after the emplacement of the variably strained 403 Ma Breakfast Hill pluton and other similar felsic intrusions. The last episode of ductile motion is based on a 275±40 Ma Rb/Sr isochron on pseudotachylite (Boeckeler, 1994). Refinement of that estimate by O’Brien and van der Pluijm (personal communication, 2012) suggests last motion as young as 235-238 Ma, nearly coincident with the emplacement of the Mt. Agamenticus complex.

Named for New Castle’s colonial park (Carrigan, 1984a,b), the Great Common fault zone is traceable

across Portsmouth harbor where it continues as the Fort Foster brittle zone (Swanson, 1988). Pervasive ductile structure occurs throughout the Rye, but strongest deformation is concentrated in the Portsmouth fault zone and in the Great Common fault zone. The latter, originally mapped as an internal boundary in the Rye that separated metavolcanic from metasedimentary members (Novotny, 1969; Billings, 1956), is now recognized as a 100-200 meter wide, laminated ultramylonite. The high strain zone consists of chocolate brown ultramylonite where protoliths were quartzo-feldspathic rocks and dark greenish black ultramylonite where dominated by calcsilicates (para-amphibolite?). Swanson (1988) describes pseudotachylyte generation zones parallel to ultramylonite laminations which locally ‘feed’ fused host rock into cross (gash) fractures in both types.

The Portsmouth Fault has a long history. It separates the Rye Complex from the Kittery Formation.

Strongly deformed amphibolite facies schists, quartzo-feldspathic mylonitic gneisses, and variably foliated felsic intrusives characterize the Rye. They are juxtaposed against lower greenschist facies feldspathic and variably calcareous metasandstones and minor metashales of the Kittery Formation across a 200-500 meter wide transition zone (Carrigan, 1984a; Rickerich, 1983) in the Portsmouth Harbor area. Little or no shear fabric is developed in the adjacent Kittery Formation, suggesting that the last motion was brittle. This is further confirmed by breccia consisting of clasts of both Rye and Kittery lithologies, slickensided blocks with a range of orientations, and minor hydrothermal alteration along the fault. Slip sense deduced from slickensides, breccia and abrupt change in metamorphic grade (first recognized by Novotny, 1969) suggest a steep west-dipping normal fault, west-side down. The age of this movement may be as young as Mesozoic but predates dike emplacement. .

METAMORPHISM Peak metamorphism recorded by rocks of the Rye Complex is primarily amphibolite facies from garnet to second sillimanite zone, significantly higher than in the adjacent rocks of the Merribuckfred trough. At least two episodes of regional metamorphism are recorded in their complex polydeformational history. Increasing grade, northwest to southeast, has long been recognized: Novotny (1969) mapped a biotite/oligoclase-actinolite isograd in the Kittery Formation,(presumably from calc-silicates near the Portsmouth fault zone) and a sillimanite isograd in the Rye near the coast. Based in part on Novotny’s dissertation work in 1953-54, Billings (1956) showed biotite, garnet, staurolite, and sillimanite isograds that define a metamorphic dome. Carrigan (1984a, 1984c) refined the distribution of isograds in pelitic and calc-silicate protoliths, reporting that the major mineral assemblage in the Kittery Formation on the NW side of the PFZ is quartz+muscovite+biotite with late chlorite after biotite, consistent with Novonty’s (1969) work. He argued for a metamorphic break at the Portsmouth Fault. Metapelites SE of the PFZ on New Castle Island have distinctly higher grade metamorphism. Carrigan (1984a, 1984c) identified quartz + biotite + sillimanite + garnet + Kfeldspar, quartz + biotite + sillimanite + garnet + Kfeldspar + muscovite, and quartz + biotite + Kfeldspar + muscovite in his Zone III NW of the GCFZ. These assemblages indicate metamorphism reached the second sillimanite isograd. In addition Stoesz et al. (2013) report


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magnesio-hornblende + oligoclase to andesine at New Castle Common, also NW of the GCFZ, consistent with amphibolite facies metamorphism. Across the GCFZ to the SE at Fort Stark Carrigan (1984a, his Zone VII) reports two periods of metamorphism. The first is quartz+biotite+garnet+sillimanite+muscovite. Staurolite and andalusite grew during a second metamorphism. The andalusite is cross-folial and includes strained quartz that parallels the foliation. Offshore between New Castle and the Isles of Shoals thin sections show sillimanite + Kfeldspar + muscovite +biotite indicating second sillimanite grade metamorphism (Brooks, 1986).

Welch (1993) conducted electron microprobe analyses on plagioclase-amphibole pairs in amphibolite and garnet-biotite in pelitic rocks from opposite sides of the GCFZ in New Castle. Thermobarometry from andalusite-garnet-biotite schist, quartzite, and minor calc-silicate rocks suggest metamorphism at temperatures ~150°C and 1 kb less than strongly sheared sillimanite-garnet schist and less deformed amphibolite exposed north of the fault. Stoesz (2009) reports hornblende-plagioclase temperatures of ~430-580°C along the GCFZ and ~620-750°C from New Castle Commons. These values suggest perhaps as much as 3km of displacement, west-side up, on the Great Common Fault.

A HISTORY TO DATE

Figure 5. Time – temperature diagram based on 39Ar/40Ar closure temperatures (horizontal light gray dashes) of amphibole (hbl), muscovite (mu) and recrystallized muscovite (rxl mu) and K-feldspar (k). Dated plutons (shaded balloon - melanocratic; open balloon – leucocratic) are plotted against estimated crystallization temperature. Diabase dikes are shown as vertical black bars. GCFZ – Great Common Fault Zone. Labeled diamonds refer to detrital zircons from the Rye Complex (R) and Kittery Formation (K), dashed diamond indicates LA-MS-ICP age determintaion; solid, CA-TIMS age determination; vertical arrow shows zircons dated from Wallis Sands body. Plutons: ws – Wallis Sands, np – Newburyport, e – Exeter, bh – Breakfast Hill, a – Appledore, sp – Salamander Point, ag – Agamenticus, cn – Cape Neddick. References same as Figure 2. Diagram modified from Stoesz et al. (2013).

Amphibole closure!!!Muscovite closure!!Kfeldspar – high temp!!Kfeldspar – low temp!

T°C!!700!!600!!500!!400!!300!!200!!100!!0!

600 550 500 450 400 350 300 250 200 150 Age (Ma) !

!!!!!!!!!!!!!!!!!! ! ! ! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!cn ! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!e!!!!!a!!!!sp!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!ag!

!!!!!!!!!!!!!!!!ws!!!!!!!!!!!!np!!bh! ! ! ! ! ! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! ! ! !!!!!!!!!!!!!!!!!!MZ!dike!swarm!

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!hbl!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!CGFZ!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!mu!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!k!k!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!rxl!mu!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!k!!!!!k!!!!!!!R!!!!!!!!!!!!!!!!!!!!!!!!K!!!K!!!


Some significant progress in establishing a history of the Rye Complex is summarized in Figure 5. The oldest components so far determined are the 539 Ma Cambrian age based on detrital zircons from micaceous quartzite at Fort Stark (Stop 4) and a clear Ordovician magmatic event at 482 Ma at Wallis Sands. A metamorphic and/or deformational event preceding the emplacement of that Ordovician intrusion is not yet confirmed but a late Cambrian/early Ordovician age is suggested from ~700°C hornblende crystallization (amphibole/plagioclase geothermometry) and closure temperature of 500°C. Further work is required to clarify this earliest history, but ductile deformation between 482 and 455 Ma, or shortly thereafter, seems probable; both rocks containing zircons of these ages are strongly mylonitized.

Adjacent Silurian metasedimentary rocks were regionally metamorphosed and deformed prior to the emplacement of early Devonian plutons (Newburyport, Exeter, Breakfast Hill) that support Salinic disturbance. Early and mid Devonian plutons in the Rye are weakly foliated relative to the blastomylonitic gneisses of the Rye that suggest more intense ductile deformation prior to and continuing into the mid Devonian Acadian deformation. Ages from those gneisses, many of magmatic origin, will help date that deformation in greater detail. Both mid and late Devonian Appledore and Salamander Point diorites and associated granites show varying degrees of foliation development but preservation of original magmatic textures. Ages of progressive and concentrated ductile shear within the Rye are now better constrained by cooling temperatures for amphibole from amphibolite and for muscovite and Kfeldspar from blastomylonitic gneisses. Shear may have begun as early as 475 Ma for amphibole and continued to 340 Ma for muscovite fish and ~245 Ma for recrystallized muscovite in evolving blastomylonitic rocks. In zones of ultramylonite ages of deformation are concentrated between 235 and 245 Ma based on argon data. These ages are consistent with Alleghanian motion in the Norumbega system. Cooling ages from Kfeldspar from ~250° to ~150°C over ~100 m.y. interval suggest slow steady exhumation perhaps initiated by last movement in the Great Common and likely Portsmouth fault zones. Basement assignment remains a continuing problem. Nd isotopic data from the granite associated with the Appledore diorite (Dorais et al., in press) suggests a Ganderian signature. Detrital zircon population density in both Rye (Kane et al., 2014) and Merrimack trough (Sorota et al., 2013) are equivocal. The nearby Massabesic Complex shows stronger Ganderian than Avalonian affinities (Dorais et al., 2012) but a direct lithic or temporal connection with this complex is lacking. Additional geochemical and isotopic data from the Rye proper may help solve this important problem.

ROAD LOG

Starting point: 9am at Hampton Park and Drive (19T 348295E 4757520N), I-95 Hampton Exit from North or South to Timber Swamp Rd Exit 13 eastbound on Rte. 101 towards the town of Hampton, NH. https://www.google.com/maps/place/Hampton+Park+and+Ride/@42.955153,-70.859469,17z/data=!3m1!4b1!4m2!3m1!1s0x89e2e8f8a8056f4d:0xaf7d3c5a34085693 Bring lunch or stop at the Towle Farm Market & Deli before rather than during the trip; it’s located only “a stones throw” past Stop 1 on Towle Farm Rd and just before we join Rt 27 A 60 mile (~1 hr drive) from Wellesley College via I-495 and I-95 STOP 0 HAMPTON PARK AND DRIVE

Gather before 9am. To minimize potential parking problems on the field trip, please carpool in as few vehicles as possible - we’ll return here by 4-4:30pm. Leg stretches before a 9am departure includes small ledges of thinly layered, mylonitized biotite schist of the Rye Formation that crops out at the ‘back’ (SE) corner of the parking lot. Sheared fabric consists of strongly oriented biotite, quartz, minor feldspar, and local fractured garnet grains. Layering strikes 285 and dips 75 NE. 0.0 Leave Park and Drive, turn left (S) on Timber Swamp Road 0.5 Turn left (E) on Mary Batchelder Road 1.1 Stop sign. Turn left on Towle Farm Rd


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1.2 Cross I-95 1.5 Park on right, across from the entrance to the new Smuttynose Brewery (we’re too early for a tour) STOP 1. KITTERY FORMATION 19T 348745E 4756322N.

The Silurian Kittery Formation is exposed on both sides of Towle Farm Rd; cross carefully to the brush-free crop on the north side. Well-bedded brown weathering purplish gray biotite metasandstone of the Kittery Formation, here first described by Casas (2008) dominates the roadcut. It is cut by a 5-m thick Mesozoic diabase dike trending 045 at the west end of the outcrop. However, most prominent are meter-scale, shallow SW plunging F2 folds on an upright SE dipping limb of a larger fold. These are expressed as mullion-like lineations defined by fold hinges plunging 15-20°SW and are parallel a variably developed NW-dipping axial plane cleavage in slightly more pelitic layers. Primary evidence for multiple deformation is very small scale and unfortunately obscured by weathering, but cm-scale laminations preserve elegant grades in a few places.

Detrital zircons were extracted from outcrops much like this in Portsmouth. They were analyzed by U-Pb LA-ICP-MS and yielded a spectrum of ages from 413±11 Ma to ~1.8 Ga. The population distribution is shared with the related Eliot and Berwick formations. The four youngest zircons from this suite of Kittery zircons were reanalyzed by CA-TIMS with the youngest age of the four at 432.19±0.68 Ma. We take this mid-Silurian age as the maximum age of the Kittery, younger than that proposed by Wintsch et al. (2007).

a. b.

c. d.

Figure 6. Kittery exposure (a) ‘in front’ of Smuttynose Brewery illustrating plunging fold hinges, (b) detrital zircon population distribution plots from Sorota (2013) and Wintsch et al. (2007), (c) supporting data, and (d) Concordia diagram from the four youngest zircons reanalyzed by CA-TIMS. Continue east on Towle Farm Road to the end.


2.1 Stop sign. Turn right (S) on Rte. 27 (Exeter Rd) 2.5 Stoplight. Continue east across Rt. 1/Lafayette Road on High St. 3.0 Stoplight, keep straight. 4.9 Stoplight, intersection Rt. 27 and US 1A (Ocean Blvd), turn left on US 1A north 6.1 N Hampton Sate Beach on right, continue on Ocean Blvd 6.5 Junction with Rt. 111 (Atlantic Ave) on left, exposures of Rye Fm. on right, continue N on Ocean Blvd 7.2 & 7.5 Potential parking if necessary 7.7 Central Rd on left, no parking 7.8 Turn left on Church Rd, and park on the right. Subsequent visits should obtain permission from Ms. Ann

DeMarrow at 100 Church Road; walk to headland outcrops, watch traffic, including cyclists, on Rte. 1A! STOP 2. PELITIC SCHIST SCREENS AND DIKE SWARM 19T 355890 4759240

Hussey and Bothner (1995, Stop12) describe these photoscenic crops below rip-rap as dark gray garnet (coticule)-tourmaline-biotite-(fibrolite) schist and lighter gray quartz-feldspar-mica schist of the Rye “Formation.” These are preserved as “screens” several meters thick between 7 or more 0.5 to 5-meter thick multiple diabase dikes trending ~035 that occupy >50% of the outcrop area (a nice dike swarm!). One of the dikes contains a small xenolith of unmetamorphosed coarse grained gabbro, presumably plucked on the way up. The screens and schist inclusions show little offset. The pelitic schist dips gently to the SW and is folded about shallow south plunging axes that approximately parallel the stretching lineations. Numerous mostly dextral ~EW trending shears cut the schist. In thin section the pelitic schist contains abundant fine grains of idioblastic tourmaline, garnets (as massive coticules and as single idioblastic grains with inclusion rich cores and clear rims), kinked biotite, and highly strained quartz (good deformation lamellae, subgrain development, mortar texture). Relic fibrolite(?) is now massive fine grained white mica. Some chlorite formed at the expense of both biotite and garnet in the greenschist facies and possibly from syn-dike emplacement some 180 to 200 million years ago.

Figure 7. Dike swarm in sheared pelitic schist of the Rye Complex, Church Road vicinity, Rye, NH Continue along Church Rd 8.0 Church parking lot 8.2 Rejoin Rte. 1A, turn left 8.8 Jenness State Park 10.1 Rye Harbor 10.5 Rye Harbor State Park 12.7 Wallis Sands State Beach. Enter lot and park, walk N to headlands if open, else 13.0 Park on right


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STOP 3. LEDGES NORTH OF WALLIS SANDS STATE BEACH 19T 359415 4765360 Hussey and Bothner (1995, Stop 11) describe this extensive crop as an elegant example of the variety of metasedimentary protoliths in the Rye Complex, here less pelitic than at Stop 2, intrusive granites and related pegmatites, and the site of a remarkable metaigneous “quartzite” lookalike that yields a clear Ordovician intrusive age (Kane and others, 2014; Fig. 3).

Figure 8. Field photographs of Wallis Sands ledges and sample site in the Rye.

Anastamosing mylonitic foliation is well displayed in both the metasedimentary Rye and in cross-cutting granitic “sills” where very strong C/S fabric is well developed. Early tourmaline-bearing pegmatites are strongly deformed as well. Large K-feldspars grains in the pegmatites are megascopic sigma porphyroclasts demonstrating the common dextral shear widespread in the Rye. Granitic layers, metasedimentary layers, and a dismembered rusty weathering sulfide-rich asymmetric mafic pod (in map view a shear boudin of metadiabase?) are shown in Figure 8. The metasedimentary rocks include well foliated garnet-bearing quartz-feldspar-biotite granofels intercalated with thin (1-4cm) pinkish calc-silicate layers. Both they and the gneisses contain isoclinal intrafolial folds and strong subhorizontal stretching lineation. However, feldspars are not severely deformed and are slightly coarser than quartz, which is flattened in the plane of foliation. The calc-silicate layers have a mineral assemblage of pinkish garnet-epidote-hornblende-biotite-feldspar-quartz-sphene, and pelitic layers contain the assemblage quartz-garnet-biotite-white mica (trace) and are shown as the middle amphibolites facies on the Lyons et al. (1997) map. The granite has a blastomylonitic texture. Both plagioclase and microcline are fractured and rotated into C-planes enhanced by preferred orientation of fine-grained white mica. Quartz has undergone significant grain size reduction and has not totally recovered, a feature common to much of the Rye. Strongly deformed quartz, with less deformed feldspar probably places the metamorphic conditions of this deformation in the greenschist facies, even though macroscopic evidence clearly shows amphibolite facies deformation as well. Together these relationships show that the dextral deformation likely occurred during the middle Paleozoic exhumation of these rocks. Continue along the shoreline parallel to strike 14.0 OPTIONAL STOP Odiorne’s Point 19T 360250 4766695 Park behind ramparts and walk to the small cove where at low tide, a number of pine trunks in living position are preserved. They have been dated by C14 to 3300 ybp and are well exposed at low tide (Goldthwait and Lyon, 1934; Chapman, 1972). Outcrops of pelitic schist and quartzofeldspathic blastomylonitic gneiss are cross cut by diabase and exposed at the south end of the inlet. 14.4 Entrance to Odiorne State Park and Seacoast Science Center 19T 360360 4767275 LUNCH STOP. Park and walk to the Seacoast Science Center. Facilities are available inside as are tables if weather is inclement. Else use tables outside or the rocks on the shore where magnificent (I hesitate to use ‘elegant’ too many times) south-plunging folds in pelitic and quartzofeldspathic blastomylonitic gneisses, sheared granite and


pegmatite cut by variably porphyritic 5cm to 4m thick multiple diabase dikes crop out. We’ll not take time to walk to the WWII gun emplacements to east but it is a worthwhile seacoast stop for future visits. Return to 1B, continue to roundabout, stay right on Rte. 1A (now Sagamore Rd) 16.6 Turn right (E) on US 1B (Wentworth Rd) 17.7 New Castle Bridge over New Castle harbor outlet. Wentworth-by-the-Sea Hotel and Conference Center on

your right. Importantly, this hotel is part of the National Trust for Historic Preservation and the site of the Treaty of Portsmouth signing, ending the Russo-Japanese War in 1905. It was renovated and reopened in 2003 as a Marriott resort. The Great Commons Fault Zone passes directly under the hotel and separates higher grade rocks to the east from lower grade rocks to the west (Carrigan, 1984; Welch, 1993)

18.1 North Gate Rd. exposes new outcrops of amphibolite, keep straight on 1B. 18.3 Turn right (E) on Wild Rose Lane, to the Fort Stark Historic Park. 18.7 Park

Figure 9. Locations of Stops 4, 5 and 6 on generalized geologic map of New Castle, NH and Gerrish Island, ME modified after Stoesz (2009). Zones in Rye Complex modified after Carrigan (1984), Dsd – Devonian Salamander Point diorite; darkened areas are outcrop localities; * - Argon sample sites from Stoesz et al. (2013) STOP 4. FORT STARK 19T 360470 4768760 Outcrops surrounding Fort Stark consist of isoclinally folded, brown weathering, well layered and strongly sheared quartzites, interlayered dark gray coarse-grained pelitic schists, and white granite and granite pegmatite of the Rye Complex, about in equal proportions as one walks the perimeter north to south. All are cut by diabase dikes a few cm to a few m in thickness. The quartzites are up to 25cm thick and dipping steeply to the northwest. Interlayered pelitic layers contain clear pink almandine garnets up to 3mm in size and smaller staurolite crystals identified with a handlens. In thin section both are fractured; andalusite appears “micro”boudined (Carrigan, 1984a). Late brittle shears trending ~070 are common. Seaward of the quartzite is ~50m thick body of sheared tourmaline-bearing granitic pegmatite with weak C/S fabric (not dissimilar to the rocks at Stop 3) before reaching a more pelitic assemblage near the north jetty protecting Wentworth ‘harbor’. Here large pavement outcrops (a ‘painters’ delight) consists of sheared pelite and quartzofeldspathic schist, some with 5-10cm knots of 2-

Dsd STOP 6 Fort Constitution STOP 5 New Castle Commons Map 1 STOP 4 Fort Stark d Odiornes State Park


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mica+garnet+staurolite+fibrolite(?). As Welch (1993) discovered, metamorphic grade is lower here than at Stops 2 and 3, and rises significantly as we cross the Great Commons Fault Zone at New Castle Commons (from zone VII to zones V, IV, and III of Carrigan 1984a).

Samples from the micaceous quartzite exposed north of the headland masking the gun emplacements at the fort yielded a suite of detrital zircons that produced a range of ages from 529 Ma to 2175 Ma. Distinct peaks occur at ~627 Ma, ~794 Ma, ~1224 Ma, and ~1506 Ma. The youngest grain is 530±9 Ma and the average of the three youngest is ~539 Ma. This is the first strongly supportive evidence that the protolith age of the Rye Complex is Cambrian in age (Kane et al., 2014).

a. PPL XPL b. Figure 10. Photomicrographs of sheared micaceous quartzite (a) and detrital zircon population plot (b) from exposures at Fort Stark. Return to Rt 1B and 19.2 Turn right on 1B and then 19.3 Turn right into New Castle Commons, turn right and right again 19.6 Park at easternmost point near the picture frame. STOP 5. NEW CASTLE COMMONS 19T 360610 4769403

Strongly sheared amphibolites, ultramylonite and pseudotachylite are well exposed on the crops immediately east of the ‘picture frame’ photo site and define the Great Common Fault Zone; watch your step as rocks can be slick! Both Mark Swanson and John Carrigan studied these rocks in the 1980’s (Carrigan, 1984a; Swanson and Carrigan, 1984). On the seaward side matrix-free brecciated ultramylonitic amphibolite contain widespread layer parallel pseudotachylite generation zones from which dark brown glassy pseudotachylite gash fracture fillings emanate. Shear patterns in the ultramylonite confirm a dominant dextral movement sense. To those with sharp eyes, intrafolial folds and tiny sigma relicts support that interpretation. Pseudotachylite from this locality and its continuation as the Fort Foster Brittle Zone on Gerrish Island provided the samples from which Boeckeler (1994) first reported a Rb/Sr age of 270± Ma that he interpreted to reflect the time of devitrification of the pseudotachylite, essentially the time of its formation in the fault zone. Subsequent work on pseudotachylite by O’Brien and van der Pluijm (2012) using 40Ar/39Ar vacuum encapsulated and rock-chip step-heating methods yielded ages nearly 50 m.y. younger. They concluded that their total gas and plateau ages of 235 Ma and 238 Ma, respectively, best represent the time of pseudotachylite generation by coseismic movement within this fault zone. However, both Permian and Triassic ages fall within the cooling age range for the 40Ar/39Ar age spectra derived from nearby K-feldspar (Stoesz et al., 2013), making the distinction between crystallization ages and cooling ages difficult to establish.

In front and northwest of the ‘picture frame’ coarse, weakly foliated amphibolite occurs in pinch and swell

(boudin-like) structures measuring a meter or two in the ‘neck’ and ‘swelling’ to about 5 m in the center. The margins are more strongly foliated and finer grained with breaks in layers, folded, and contain a few quartz knots as they are followed. Amphibole-plagioclase thermometry suggest that the coarser magnesio-hornblende grew at

400 800 1200 1600 2000 2400 2800

Rel

ativ

e pr

obab

ility

Age (Ma)

794 Ma

627 Ma

1224 Ma

1506 Ma

n = 74


temperatures ~700°C. However, the youngest step of an associated amphibole 40Ar/39Ar analysis is ~475 Ma, interestingly only ~5 m.y. younger than the apparent intrusive age obtained at Stop 3. On the other hand, if this age is found to be a cooling age recording cooling through ~ 500ºC, then this upper amphibolite facies metamorphism is also Early Ordovician or older, and may be Cambrian.

. a. b.

Figure 11. Outcrop map 1 (a) and photo (b) of amphibolite boudin at New Castle Commons

Figure 12. Argon age spectra (a) and photomicrograph (b) from amphibolite at New Castle Common (Stoesz et al., 2013)

Additional 40Ar/39Ar work from quartzofeldspathic gneisses, including those across the harbor at Gerrish Island, but are very much like those by those exposed on the walk to the old lighthouse jetty. Pegmatitic muscovite fish yield a ~340 Ma cooling age which are supported by several other analyses with the same results. Recrystallized mylonitic muscovite are younger by nearly100 Ma, and are thus very similar to the 238-235Ma reported by O’Brien and van der Pluijm for pseudotachylite in the same zone. Younger cooling ages from feldspars of ~275Ma and ~175 may reflect a temperature drop of about 100°C (from 250° at 275Ma to 150° at 175 Ma

Figure 4 a)

Amphibole

PegmatiticMuscovite

Fish

Constant K/Ca Ratio

Minimum Age Step ~475 Ma

b)

RecrystalizedMuscovite

Amph

PlagMicroboudin

Ttn


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a. b.

Figure 13. Outcrop photo of representative blastomylonitic quartzofeldspathic gneiss (a) and associated argon age spectra (b). Data from Gerrish Island (* on Figure 9) but correlative with rocks on New Castle Island. Walkers can follow the shoreline outcrops toward Fort Constitution, exit the beach where Breezy Lane reaches the shore and follow that road to the Gregg Marine Lab. Rocks are dominated by coarse porphyroblastic mylonite gneiss with granitic layers parallel to S and rotated Kspar blasts to 5cm most with a strong dextral shear. A shallow plunging 060 stretching lineation is common on foliation surfaces. Drivers return to the entrance, turn right and then go straight to the UNH Judd Gregg Marine Complex/USCG parking lot 19.9 Return to Rt. 1B, turn north (right) 20.3 Continue straight to UNH/USCG pier and Fort Constitution. 20.4 Park in the UNH designated slots or at the Gregg Marine Operations building. Public facilities are available

at the side of that building. STOP 6. NEW CASTLE LANDING 19T 360565 4770180 Medium grained, yellow-brown weathering blastomylonite dominate the outcrops west of the pier. They are interlayered with strongly porphyroblastic quartzofeldspathic gneiss and are cut by a small body of weakly foliated Salamander Point diorite and later Mesozoic diabase dikes. Among the structural elements here are dextral ductile and brittle shears that strike ~060. The earlier ductile shear displays elegant drags while the later more brittle ones, exposed a few meters seaward, have thin pseudotachylite fillings in straight and sigmoidal fractures that are interpreted as conjugate fractures. Offset of 5-10cm thick ‘granitic’ lenses are particularly instructive. This outcrop has been an important teaching site for UNH geology students since the mid 1980’s when John Carrigan first made note of the multiple shear and intrusive events represented here. Zircons from the dominant quartzofeldspathic mylonite yielded a discordant CA-TIMS 206Pb/238U age array ranging from 451 to 974 Ma. The 451 Ma plots on concordia and was interpreted to reflect the best age for this rock and had set a minimum age for the Rye or its earliest metamorphic recrystallization age until the work of Kane et al. (2014).

Muscovite

Pegmatitic PotassiumFeldspar

c)

g)

d)

h)

~339 Ma

~244 Ma

Cooling through250°C at ~276 Ma

Cooling through150°C at ~194 Ma



PegmatiticMuscovite

Fish

Qtz

K-spar

K-spar PegmatiticMuscovite

Fish

K-spar

Qtz


The Salamander Point diorite with its apparently co-magmatic granitic lenses intrudes the gneisses. The type locality is visible about 200 meters upstream on ledges at the red cape cod house on the shore. It crops out across the harbor on Fishing Island.

Figure 14. Salamander Point diorite at the type locality and at Stop 6

This hornblende biotite diorite is petrographically and geochemically similar to the Appledore diorite and, until both were dated, was correlated. The body here yields a CA-TIMS weighted mean 206Pb/238U age of 380.14±0.26 Ma while that on Appledore Island is ~20 m.y. younger (361.09±0.14 Ma) (Hussey et al., in press; Dorais et al., in press). 20.6 Return to Rt. 1B, turn west (right) – Drive slowly and with extra care through colonial New Castle town center 21.7 Parking will be difficult here. Turn left, stay right on the narrow access road and launch site… hopefully we’ll be able to make a simple U-turn and return to 1B without getting stuck! OPTIONAL STOP 7. GOAT ISLAND AND THE PORTSMOUTH FAULT ZONE 19T 360565 4770180 Goat and Shapleigh Islands lie within the 2-300 meter wide Portsmouth Fault Zone recognized initially by Novotny (1969) and remapped as the Kittery-Rye Transition Zone by Carrigan (1984) and Rickerich (1983). Outcrops across Goat Island consist of 2-25 cm thick brown metasandstone, occasionally with calc-silicate pods, and lesser rusty weathering metasiltstone/metashale with abundant quartz veining and some brecciation. South plunging folds occur across the tombolo/boat launch area. A NW-trending fracture with slickensides indicating west-side down motion (consistent with the normal fault sense for the Portsmouth fault) crops out on the south side of the small peninsula. In other outcrops along the south side of Goat Island to the causeway to New Castle, laminations in the metasandstone suggest that the Kittery Formation is northwest facing and overturned. NE-trending diabase dikes are not uncommon. 21.8 Cross bridge to Shapleigh Island. Rocks of the Kittery Formation are exposed on both sides of the bridge abutments, on the shore to the south (left) and north (right). Pierce Island (home of NH fish pier, Portsmouth Waste Water Treatment plant exposes tightly folded rocks of the Kittery Formation just outside the Portsmouth Fault Zone. Access to these shoreline exposures is reached by following Rt. 1B to Marcy St, then 0.4 miles nearly to the Strawberry Banke historical site, a hard right turn and 0.5 mile drive past the Fish Pier and Portsmouth Swim Facility to the gate leading to the Waste Water Treatment plant. Outstanding, but slippery, rocks with well-preserved primary sedimentary structures crop out opposite the Portsmouth Naval Shipyard and WWII Naval Prison. 19T 358185 4770620 22.6 Turn left 22.7 T intersection at stop sign. Turn left onto South Street 23.8 Stoplight, turn left onto Lafayette Rd (rejoin Rt 1) 23.9 Y to right on present detour 24.1 Stoplight, turn left (Greenleaf Ave, part of detour), continue on Lafayette Rd. We will go through several


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(seven!) so it is important to stay together or don’t loose count. The third light is Peverly Hill Rd, The ‘new ‘ mall complex occupies the 1960-70’s Peverly Hill quarry that provided abundant crushed mylonitic rocks of the Rye Complex. 28.3 Breakfast Hill Rd, turn right 28.4 Turn left into the Bethany Congregational Church parking lot, park and walk to outcrops across the road STOP 8. BREAKFAST HILL GRANITE 19T 352630 4763265 Markers for the Battle of Breakfast Hill of June 26, 1696 are displayed on glacially polished granitic ledges and in a small quarry. Here native Americans ate breakfast while holding early colonists captive from a June 26, 1696 assault near Rye (Brewster, 1859). The captives were rescued and the native Americans chased around the Isles of Shoals to escape near York, Maine… a significant canoe paddle!

Figure 15. Breakfast Hill monument and quarry site The Breakfast Hill granite, exposed in this small historic park and beyond the parking lot at the church, is a light gray weathering medium to coarse grained two-mica granite. It is weakly to moderately foliated consisting of quartz, microcline, plagioclase, and oriented muscovite and biotite. In thin section granulation of feldspars is common, quartz is largely recovered, and muscovite cleavage is bent. Samples from this lenticular granite body yielded a weighted mean 206Pb/238U zircon age of 403.85±0.20 Ma (Hussey et al., in press) that confirms Novotny's (1969) Devonian assignment.

END OF TRIP To return to Hampton Park and Drive via US Rte. 1. 28.5 Turn right (S) on Lafayette Road 31.1 Pass intersection with Rte. 111 34.0 Turn right (WNW) on Rte. 27 (Exeter Rd) 35.8 Turn left on Timber Swamp Road and into the Hampton Park and Drive From the Park and Drive, return to Rte. 27, turn right and then 36.2 Turn left onto Rte 101W and I95 N or S. Head S on I-95 for ~1 hr drive to Wellesley

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Boeckeler, A. J, 1994, Isotopic ages of pseudotachylite veins from coastal New Hampshire and SW Maine: Evidence for post-Acadian strike-slip motion: Geological Society of America Abstracts with Programs, v. 26, no. 3, p.

Bothner, W. A., and Hussey, A. M., II, 1999, Norumbega connections: Casco Bay, Maine to Massachusetts: in

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Formation, New Castle, New Hampshire: Geological Society of America Abstracts with Programs, v. 25, p. A-265.

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NOTES:

Ages of the Rye Complex, Coastal NH: A Deformational History Slowly Revealed

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