Newark Basin Field Trip for Petrology
Sunday, March 7th, 2010
Note: Before we leave each site, we'll determine Latitude and Longitude, and collect a sample.
Stop 1 Preakness Basalt, The Second Watchung, outcrops nearRt. 78, Berkeley Heights, NJ. This flow is Early Jurassic. It is a ridge-former because it is resistant to erosion compared to the adjacentPassaic (Brunswick) sediments.
Stop 2 Watchung Town Garage. Here two very different basalt flows are present. we will examine the flows, suggest origins for both, and tests for our ideas.
Alternate Stop 2 Chimney Rock, Bound Brook, New Jersey. A peek through the fence reveals the flow heated red shales and siltstones of the uppermost Triassic Passaic Formation. Along the stream, we'll examine the interface between the two lowest of four flows.
The quarry is operated by
Stavola.
Stop 3. Diabase Ring Dike at Round Valley Reservoir, Lebanon, NJa
Along the North Shore of Round Valley Reservoir, a Diabase that cooled from the early Jurassic magma is exposed.
"Diabase dikes and sills are typically shallow intrusive bodies and often exhibit fine grained to aphaniticchilled margins which may contain dark mafic glass.
Diabase normally has a fine, but visible texture of euhedrallath shaped plagioclasecrystals (62%) set in a finer matrix of clinopyroxene, typically augite (20-29%), with minor olivine (3% up to 12% in olivine diabase), magnetite (2%) and ilmenite (2%)."
The amazing 22-31 cloverleaf "design" at Clinton.
Travel via Rt. 31 to Flemington. Lunch in Flemington, where we will go through the Powerpoint printouts.
Then Rt. 12 to 523 South (Sergeantsville Road) toStockton, NJ near the base of the Late Triassic.
Photo of roads to 29Nheading up-section
Stop 4. Stockton Formation, Raven Rock, NJ.
The Stockton is the basal sediment in the NewarkBasin. Usually interpreted as fluvial, it doesn't show the cyclicity of younger Lockatong and Passaic (formerly Brunswick) Formations. Highlands gneisses, sandstones and carbonates weathered to laterites; arkoses derived from them washed into the newly forming rift valley. Here is the typical form, sandstone redbeds.
Stop 5. Lockatong Formation. The middle unit of the Late Triassic is the Lockatong Formation. It can be black (organic-rich persistent lake with Semionotus fish) or gray (very shallow lakes with frequent drying and mudcracks) or red (the last stop, see below). It shows strong Milankovitch cyclicity.
Stop 6. Perkasie Member of the Passaic Formation, Milford, NJ.
This is the Pebble Bluff locality. The Passaic is the uppermost Triassic sedimentary deposit in New Jersey. It contains typical redbeds that range from mudstones and fine sandstones that are usually interpreted as playas and pediments, to cobble and boulder conglomerates that coarsen as we approach the border fault. The cyclic sedimentation includes shorter and less widespread gray lake deposits.
At this locality the pebbles, cobbles and boulders are manly quartzites, presumably from the Cambrian Hardyston Quartz that is still exposed along the border fault today. USE EXTREME CAUTION HERE.
Stop 7. Holland, NJ. near the border fault, we will examine a small exposure of breccia containing mostly carbonate blocks. These probably were derived from the Cambrian Leithsville Dolomite, which lies above the Hardyston is also exposed along the fault.
Return to Frenchtown and thence to Flemington via Rt. 12.
Stop 8. Has been removed by the highway department.
Stop 9 (Final Stop) Mine Creek Park and Morales Nature Trails, Capner St., Flemington, NJ. Here is the red form(low-stand) of the Lockatong Formation in contact with a flow that is chemically similar to Orange Mountain Basalt. The beds here dip steeply enough that we can see the alteration zone. Across the stream are explosion breccias where the basalt hit wet sediment. If the water levels are low we may be able to collect mudcracks on bars and copper mineralization at the contact; otherwise we will return to the road and approach the contacts along the other shore.
Return to Campus.