Skip to Main Content
Skip Nav Destination
GEOREF RECORD

Volcanic structures, eruptive style, and posteruptive deformation and chemical alteration of the Watchung flood basalts, New Jersey

John H. Puffer and James J. Student
Volcanic structures, eruptive style, and posteruptive deformation and chemical alteration of the Watchung flood basalts, New Jersey (in Eastern North American Mesozoic magmatism, John H. Puffer (editor) and Paul C. Ragland (editor))
Special Paper - Geological Society of America (1992) 268: 261-277

Abstract

Field observations of Early Jurassic Watchung Basalt throughout the Watchung syncline, including 17 large trap-rock quarries, provide new data on the number of flows, their structure, and the eruptive style of the lavas. Three Orange Mountain Basalt flows, five Preakness Basalt flows, and two Hook Mountain Basalt flows are mapped. The volcanic structures and the eruptive style of the Watchung Basalt flows are typical of continental flood-basalt provinces. The great thickness and large lateral extent of Watchung flows and their pahoehoe surfaces confirm geochemical evidence that viscosity of the lavas was low and eruptive rates were high. Low viscosity of the First Preakness flow and its unusually great thickness (up to 150 m) may account for the thick, phaneritic, diabasic zones and the small lenses of basaltic pegmatite in the flow. Several different kinds of flow structures, including cooling joint patterns and vesicle distributions, indicate that most Watchung lava flowed onto a dry land surface but that some flowed into large lakes. Subaerial cooling of most Watchung flows produced a shrinkage joint pattern that consists of a single basal colonnade and a well-developed entablature. These early primary shrinkage joints were modified later by tectonic joints. The Watchung Basalt is cut by strike-slip faults that strike N30 degrees W. These faults are consistent with north-south compression that coincided with development of the Watchung syncline. Chemical alteration processes that have modified the Watchung Basalt to varying degrees include weathering, salt-water reactions, sediment assimilation, hydrothermal activity, and metasomatism. The lower colonnades of most flows have been particularly affected by saline waters, resulting in major variations in SiO (sub 2) , FeO, MgO, CaO, Na (sub 2) O, K (sub 2) O, Cu, and Zn.


ISSN: 0072-1077
EISSN: 2331-219X
Coden: GSAPAZ
Serial Title: Special Paper - Geological Society of America
Serial Volume: 268
Title: Volcanic structures, eruptive style, and posteruptive deformation and chemical alteration of the Watchung flood basalts, New Jersey
Title: Eastern North American Mesozoic magmatism
Author(s): Puffer, John H.Student, James J.
Author(s): Puffer, John H.editor
Author(s): Ragland, Paul C.editor
Affiliation: Rutgers University, Geology Department, Newark, NJ, United States
Affiliation: Rutgers University, Geology Department, Newark, NJ, United States
Pages: 261-277
Published: 1992
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
ISBN: 0813722683
References: 44
Accession Number: 1993-006085
Categories: Igneous and metamorphic petrology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 1 table, strat. cols., sketch maps
N38°55'00" - N41°21'00", W75°34'60" - W73°52'60"
Secondary Affiliation: Florida State University, USA, United States
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute.
Update Code: 1993
Close Modal

or Create an Account

Close Modal
Close Modal