38 Undergraduate Research in the Geological Sciences II (Posters)

Saturday, 29 March 2003
8:00 AM - 4:30 PM

DISTRIBUTION OF PEPERITES IN THE WALLINGFORD-NORTHFORD, CT, AREA

Paper number: 38-21
Program: THEME SESSIONS
Time: 8:00 AM – 4:30 PM

Authors

Abstract

Continuation of fieldwork begun in 2001, which first identified the formation of peperites in the southern Hartford Basin, has resulted in the further characterization and areal distribution of peperites in the east Wallingford, CT, to Northford, CT, area. Blocky peperites and mixed blocky and fluidal peperites formed where rising melt interacted explosively with groundwater and with coarse, water-saturated sediments of the New Haven Formation, and underwent brittle quench fragmentation. Peperite envelopes and aprons are associated with en echelon segments of the Fairhaven dike system. Here breccias containing globular basalt, basalt droplets and fiammae-like fluidal basalt particles are intimately mixed with disaggregated and fluidized fan and fluviatile sediments. Wohletz (1983) type-2 pyroclasts are common.

Peperites similar in type are located stratigraphically above the main feeder and appear to be confined to an horizon immediately below an amygdaloidal basalt flow of probable lower Talcott age. Here peperites may have formed as magma traveled over wet fan surfaces. The two peperite occurrences are spatially and genetically related, recording subsurface and surface fuel-coolant interactions which preceded and accompanied the beginning of effusion of flood basalts in the basin.