Newark Supergroup Basins and Geological Formations
The Newark Supergroup represents a complex series of sedimentary and volcanic rocks distributed across eastern North America. Historically, local paleontologists assigned unique names to the formations within separate basins and sub-basins. However, modern research suggests a more unified approach. A 2016 study by Weems, Tanner, and Lucas proposed that these formations be defined on a regional scale, reflecting the geological uniformity observed across the region.
These formations track the environmental shifts of the Late Permian through the Early Jurassic, documenting a transition from arid alluvial plains to humid lake systems and massive volcanic eruptions.
ไม่มีภาพประกอบ
Key Facts
- Regional Standardization: Recent studies propose regional formation names to replace basin-specific nomenclature due to geological uniformity.
- Time Span: The sequence covers the Late Permian through the Early Jurassic.
- Diverse Environments: Deposits range from aeolian (wind-blown) sandstones and fluvial (river) deposits to lacustrine (lake) sediments.
- Volcanic Activity: The Meriden Group is characterized by significant basalt flows associated with the Central Atlantic Magmatic Province (CAMP).
Regional Stratigraphy of the Newark Supergroup
The regional formations are categorized into groups, ordered here from the youngest (top) to the oldest (bottom).
The Portland Group (Early Jurassic)
This group consists primarily of semi-arid deposits:
- Longmeadow Sandstone: Semi-arid fluvial deposits.
- Mount Toby Conglomerate: Semi-arid alluvial conglomerate.
- Boonton Formation: Lacustrine deposits.
The Meriden Group (Latest Triassic to Early Jurassic)
This group is defined by a mix of volcanic activity and sedimentary layers:
- Hampden Formation: Basalts.
- East Berlin Formation: Semi-arid lacustrine and alluvial deposits.
- Holyoke Formation: Basalts and rare sediments.
- Shuttle Meadow Formation: Lacustrine and freshwater limestone deposits.
- Talcott Formation: Basalts and rare sediments from the Rhaetian stage.
The Chatham Group (Carnian to Rhaetian)
The Chatham Group reflects a shift toward more humid conditions:
- Passaic Formation: Semi-arid fluvial and deltaic deposits.
- Lockatong Formation: Humid lacustrine deposits.
- Stockton Formation: Humid fluvial and deltaic deposits.
- Doswell Formation: Humid fluvial, lacustrine, and coal deposits.
The Acadia Group (Late Permian to Ladinian)
The oldest regional units, characterized by arid conditions:
- Evangeline Formation: Semi-arid fluvial deposits.
- Economy Formation: Arid fluvial deposits and aeolian sandstone.
- Chedabucto Formation: Red beds of uncertain stratigraphy.
- Honeycomb Point Formation: Arid alluvial conglomerate and aeolian sandstone.
Basin-Specific Equivalents
While regional names provide a standard, many basins maintain local nomenclature. These local formations are often equivalent to the regional units described above.
| Basin | Local Formation | Regional Equivalent |
|---|---|---|
| Deep River | Sanford Formation | Passaic Formation |
| Danville/Dan River | Stoneville Formation | Passaic Formation |
| Richmond | Otterdale Sandstone | Stockton Formation |
| Taylorsville | Leedstown Formation | Passaic Formation |
| Culpeper | Mount Zion Church Basalt | Talcott Formation |
| Gettysburg | New Oxford Formation | Stockton Formation |
| Newark | Orange Mountain Basalt | Talcott Formation |
| Hartford | Portland Formation | Boonton, Longmeadow, & Mount Toby |
| Fundy | North Mountain Basalt | Talcott Formation |
Distribution of Minor Basins
Beyond the major basins, several minor basins are present across the eastern United States and Canada. These include the Crowburg and Wadesboro basins in South Carolina; the Ellerbe and Davie County basins in North Carolina; numerous basins in Virginia (such as Scottsburg, Randolph, and Farmville); the Cherry Brook Outlier in Connecticut; the Northfield and Middleton basins in Massachusetts; and the Chedabucto Basin in Nova Scotia.
Frequently Asked Questions
Why were regional formations proposed for the Newark Supergroup?
Researchers Weems, Tanner, and Lucas (2016) proposed regional definitions because the geological characteristics are remarkably uniform across eastern North America, making a standardized system more accurate than fragmented local names.
What is the difference between fluvial and lacustrine deposits?
Fluvial deposits are sediments laid down by rivers and streams, whereas lacustrine deposits are formed in lakes.
Which group in the Newark Supergroup is most associated with volcanic activity?
The Meriden Group is the primary volcanic unit, containing the Hampden, Holyoke, and Talcott formations, which consist largely of basalts.
What are aeolian sandstones?
Aeolian sandstones are sedimentary rocks formed from sand that was transported and deposited by wind, typically indicating an arid or desert environment.
How does the climate change across the Chatham Group formations?
The Chatham Group shows a transition from the humid conditions of the Stockton and Doswell formations to the semi-arid conditions of the Passaic Formation.