PATS POND AND WIGWAM BROOK GROUPS: RECORD OF EPISODIC PERI-GONDWANAN UPPER CAMBRIAN-CARADOC ISLAND ARC ACTIVITY IN THE EXPLOITS SUBZONE OF CENTRAL NEWFOUNDLAND

The newly defined Pats Pond Group (PPG) and (dis?)conformably overlying Wigwam Brook Group (WBG) occupy a fault-bounded slice, immediately east of the Red Indian Line in central Newfoundland. They are juxtaposed structurally to the west with peri-Laurentian arc volcanic rocks of the Llanvirn (c. 464-462 Ma) Harbour Round Formation and to the east along the Barren Pond Fault with Llanvirn (c. 460 Ma) arc/backarc rocks of the Sutherlands Pond Group. The base of the PPG consists of calc-alkaline basalts (eNd 0.3 to -0.5), overlain by bimodal mafic-andesitic tuff breccias with numerous horizons of both mafic and andesitic tuff (eNd 4.6 to 5.5) and lapilli tuff. The breccia yielded a U-Pb zircon age of 487±3 Ma. The WBG consists of three formations. The basal Dragon Pond formation comprises basal, tuffaceous turbiditic siltstones and sandstones, calc-alkaline tuff, flow-banded rhyolite and basalt flows with IAT compositions. Turbidites have abundant erosion channels with rafts of the underlying turbidite beds, and locally liquefaction features. The overlying Halfway Pond Formation comprises tuffaceous conglomerate (U-Pb zircon age of 452.8±3.5 Ma), fine-grained sandstone, siltstone and mudstone, locally with well-developed flaser and lenticular bedding. It is transitional with upper Caradoc black shale of the Perriers Pond formation. Age data suggest there is at least an Arenig hiatus between the PPG and WBG. The PPG and the WBG largely represent episodic Early to Late Ordovician arc magmatism of the Popelogan-Victoria arc, which was terminated in the Caradoc as a result of its collision with the peri-Laurentian Notre Dame arc. The age, isotopic, and stratigraphic characteristics of the PPG suggest a correlation with parts of the Tremadoc Glovers Harbour Formation of the Wild Bight Group and the Tea Arm Formation of the Exploits Group, both comprising Exploits Subzone arc volcanic rocks. Epiclastic rocks of the Dragon Pond formation have eNd from -4.3 to -10.3, inconsistent with the values generally observed in the rocks of the Exploits Subzone. This may indicate greater contribution of Precambrian Exploits basement and/or volcaniclastic input from the Notre Dame Subzone prior to or during the middle to upper Caradoc arc-arc collision.