A distinctive assemblage of upper greenschist to lower amphibolite facies metasedimentary rocks with intercalated mafic and ultramafic rocks forms a major tectonostratigraphic unit, the Liberty Complex, within the central Maryland Piedmont. The Liberty Complex is composed of two lithotectonic units, the Morgan Run Formation and the Sykesville Formation. The Morgan Run Formation is a thick sequence of pelitic schist with intercalated quartzite, amphibolite, and detrital ultramafite; metagraywacke and intercalated amphibolite; serpentinite and associated ultramafic rock. The Sykesville Formation is a thick, poorly layered sequence of uniform, medium-grained quartzofeldspathic granulite and metadiamictite. Metamorphosed clasts in the diamictite are everywhere matrix supported, range in size from granules to slabs at least tens of meters in length, and commonly display internal metamorphic foliations that are truncated by the clast margins. Petrographic study of clast lithologies from exposures around Liberty Lake in Carroll and Baltimore Counties indicates that all clasts are represented by Morgan Run Formation bedrock lithologies in the immediate area. The Morgan Run and Sykesville Formations are both polydeformed; however, the Morgan Run displays several phases of deformation that are not expressed in the Sykesville Formation or adjacent Piedmont terranes. Metagraywacke sequences in the Morgan Run commonly exhibit relict soft-sediment structures, and pelitic schist-quartzite sequences contain stratiform zones of block-in-matrix structure, which we interpret to be tectonic mélange. The Sykesville Formation was deposited after initial metamorphism of the Morgan Run Formation as a sequence of mass-flow and slide deposits characteristic of sedimentary mélanges. The lithologic assemblage and the internal structural features of the Morgan Run Formation are strongly suggestive of an origin within a subduction complex. We interpret the Morgan Run as having been assembled in an accretionary wedge fronting a continent-facing volcanic arc in Cambrian time. The Morgan Run may represent underplated oceanic and trench-fill material that was deformed into tectonic mélange and broken formation during subduction and then rapidly uplifted as the continental margin of North America collided with the accretionary wedge. The Morgan Run Formation supplied coarse metamorphic detritus to the Sykesville deposits during collision and uplift. Both units were strongly deformed, locally interleaved, and regionally metamorphosed during final suturing of the arc to the continental margin. This final stage of development represents the classical Taconic orogeny. It resulted in the assembly of the Liberty Complex, a polygenetic mélange, from the Morgan Run and Sykesville Formations.

Abstract The Liberty district is located approximately 20 miles southwest ofWenatchee. Production from the district has been chiefly placer gold, discovered along Swauk Creek (following Route 97) in 1874. Major dredging operations began in 1922 (Livingston, 1963), and mining on a commercial scale along Williams Creek near the Liberty townsite has taken place as recently as 1987. The source of the gold, quartz veins largely within arkosic rocks, was discovered in 1881. Mapping and sampling in the Liberty district were undertaken by the author in 1987 for ASARCO, Inc. (Spokane, Washington), who granted permission to discuss the general features of the district as outlined below. Numerous low-sulfide, upward-branching quartz veins (mostly <1m wide) distributed over a 20 square-mile area within the Early Eocene Swauk Formation contain minor, coarse native gold (Figure 1). The Silver Pass Formation, consisting of greenish arkosic sandstone and intermediate-composition volcaniclastic rocks and minor pumiceous deposits, was deposited unconformably on folded Swauk (broad northwest-trending axes) prior to the intrusion and deposition ofTeanaway Basalt dikes and flows, and hosts vein mineralization. Note that Taboret al. (1982) did not recognize Silver Pass rocks in the Liberty area. Veins also occur in dikes and stocks ofTeanaway Basalt (46-47 Ma; Taboret al., 1982) that intruded the Swauk and Silver Pass Formations. Two distinct vein zones containing at least 70 veins extend for at least 7000 meters (Figure 1). Veins contain abundant open space and cockscomb quartz. Pervasive hydrothermal alteration is rare in the vicinity of the veins, most of which

The Belfast quadrangle is located west of Penobscot Bay in east-central Maine. The stratified rocks of the quadrangle have been regionally metamorphosed, multiply folded, and intruded by plutonic rocks. They are exposed in two major structural blocks separated by the St. George longitudinal fault. The oldest rocks in the Passagassawakeag block, the Passagassawakeag Formation, are Precambrian(?) in age and are exposed in the Liberty-Orrington anticline. These rocks consist primarily of quartz-plagioclase-biotite gneiss; minor amphibolite and gneiss with sillimanite and muscovite are present. A calc-silicate member and a fine-grained gneiss unit composed almost entirely of quartz, oligoclase, and microcline (the metavolcanic Mixer Pond Member) are mapped separately. Unconformably overlying the Passagassawakeag Formation northwest of the Liberty-Orrington anticline is the Hogback Schist of probable Cambrian or Ordovician age. Aluminous schist, micaceous quartz-feldspar gneiss, biotite gneiss, and calc-silicate gneiss are included in the Hogback Schist. Southeast of the Liberty-Orrington anticline, the Bucksport Formation of probable Late Silurian or Early Devonian age is interpreted to overlie unconformably the Passagassawakeag Formation. The Bucksport Formation is composed of calc-silicate gneiss, biotite gneiss, and minor biotite schist. It is overlain conformably by the Appleton Ridge Formation of probable Early Devonian age. The Appleton Ridge Formation consists of phyllite or staurolite schist cyclically interbedded with quartzite; at the top of the exposed sequence there is schist rich in garnet and cummingtonite (Muzzy Ridge Member). The stratigraphic section of the Passagassawakeag block is bounded on the southeast by the St. George fault. The oldest rocks exposed in the Penobscot block that lies southeast of the St. George fault are marble and other poorly exposed rocks found in the core of the Coleman antiform. They are correlated with the Rockport sequence of the Camden-Rockland area. Also exposed in the Coleman antiform are quartzite, quartz-mica schist, retrograded sillimanite gneiss, feldspar-quartz-biotite gneiss, and calc-silicate quartzite correlated with the upper part of the Battie Formation in the Camden area. The age of these rocks is believed to be Cambrian or Ordovician. The Penobscot Formation of Ordovician age overlies the Battie Formation and constitutes most of the Penobscot block. The Penobscot Formation consists dominantly of phyllite, andalusite schist, sillimanite gneiss and granofels, quartz-mica schist, and quartzite; most of these rocks are sulfidic. There are rare marble, calc-silicate gneiss, amphibolite, garnet-cummingtonite schist, and plagioclase-quartz granofels of volcanic origin. Metamorphosed volcanic rocks of mafic and felsic composition (Gushee Member) are largely restricted to the upper part of the formation. The Jam Brook Formation is exposed between the Penobscot Formation and the St. George fault but thins and terminates along strike to the northeast. The Jam Brook contains quartz-pebble metaconglomerate, quartzite, quartz-mica schist, andalusite schist, calc-silicate gneiss, and marble, in generalized order of appearance from east to west. There are changes of facies within the formation. The age of the Jam Brook is believed to be Cambrian or Ordovician. The Jam Brook probably correlates with the Rockport sequence, and its contact with the Penobscot Formation is inferred to be a thrust fault.

Middle Cambrian or probably Middle Cambrian trilobites were collected at six localities in the Heritage Range of the Ellsworth Mountains, including Yochelson Ridge, Drake Icefall area, Edson Hills, Liberty Hills (two locations), and Marble Hills. The total fauna includes 14 genera (2 new) and 32 species (5 new). Due to original preservation and/or deformation, a number of the forms are not assignable to specific taxa. The new taxa described herein are Peronopsis deons sp. nov., Pagetia edsonensis sp. nov., Sohopleura drakensis gen. et sp. nov., Pseudobergeronites spinosa gen. et sp. nov., and Blountia perplexa sp. nov. The trilobites were found in formations of the upper Heritage Group (Springer Peak Formation, Drake Icefall Formation, and Liberty Hills Formation). The trilobite faunas described show affinities with faunas from northern Victoria Land (Antarctica), Tasmania, Queensland, China, Kazakhstan, and North America. All faunas are probably Middle Cambrian in age (Templetonian and Boomerangian on the Australian biochronological scale).