Petrographically deduced triassic climate for the Deep River Basin, eastern piedmont of North Carolina

Conference · Tue Jan 01 00:00:00 EST 1985 · Geol. Soc. Am., Abstr. Programs; (United States)

OSTI ID:6462642

McCarn, S T; Mansfield, C F

A petrographic comparison of Triassic, fluvial sandstones from the Deep River Basin in the eastern piedmont of North Carolina with nearby Holocene stream sands (1) indicates that he Triassic climate was more arid than today's and (2) distinguishes an eastern, more plutonic terrane from a western, more metamorphic source terrane. The paleoclimatic interpretation is based on differences in framework composition between modern and ancient sands of the same grain size, derived from the same rock type, transported similar distances and deposited in similar settings. The Triassic sandstones contain more lithic-fragments but less quartz than otherwise equivalent, modern sand in the Deep River Basin. Feldspar content is more complex, controlled by both source-rock composition and climate. Sand from the more plutonic terrane contains more feldspar and plutonic lithic-fragments than sand from the more metamorphic terrane, which contains more quartz and metamorphic lithic-fragments. This petrographic interpretation of the Triassic sandstones along with the presence of coal, limestone, chert and caliche in the middle of the section suggests that the Triassic climate was cyclic, changing from arid to humid and back to arid. Plate-tectonic reconstructions place the Deep River Basin between the Triassic equator and Tropic of cancer, where the easterly trade winds would predominate. Therefore, the arid portions of the cycle could have been due to a periodic, orographic, rain shadow formed as the result of intermittent movement along the Jonesboro Fault, creating a highland area east of the Deep River Basin.

• Research Organization: Sun Exploration and Production Co., Midland, MI (USA)
• OSTI ID: 6462642
• Report Number(s): CONF-8510489-
• Journal Information: Geol. Soc. Am., Abstr. Programs; (United States), Vol. 17; Conference: 98. annual meeting of the Geological Society of America, Orlando, FL, USA, 28 Oct 1985
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
NORTH CAROLINA
SANDSTONES
PALEOCLIMATOLOGY
PETROGRAPHY
PETROLOGY
CLIMATE MODELS
FELDSPARS
GRAIN SIZE
MINERALOGY
SAND
TRIASSIC PERIOD
CRYSTAL STRUCTURE
FEDERAL REGION IV
GEOLOGIC AGES
GEOLOGY
MATHEMATICAL MODELS
MESOZOIC ERA
MICROSTRUCTURE
MINERALS
NORTH AMERICA
PALEONTOLOGY
ROCKS
SEDIMENTARY ROCKS
SIZE
USA
580100* - Geology & Hydrology- (-1989)
580300 - Mineralogy
Petrology
& Rock Mechanics- (-1989)