Nd isotopic constraints on sediment sources of the Ouachita-Marathon fold belt: alternative interpretation and reply

Article Abstract:

Gleason and his colleagues (1995) argued that a sudden shift in Nd isotopes at 450 Ma in the Ouachita succession indicates a transition from a provenance in the cratonic interior to a provenance in the Appalachian orogen. They also contended that sediments from Appalachian sources dispersed throughout the Ouachita and Marathon regions across the southern margin of the continent. However, the failure to resolve provenance characteristics in Nd isotopes shows the need for further examination of regional sediment dispersal, diachroneity of orogenesis, lithotectonic composition of provenances, and location of orogenic uplifts.

Sedimentary structures, Isotope geology, Marathon, Texas

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Article Abstract:

The provenance of detritus in turbidites from the Ouachita Mountains may be gleaned from Nd isotopic data. While such data provide no direct indications of dispersal paths or provenance, Nd isotopes may be useful in such analyses because they are combinations of recycled crustal components. Analysis suggests that southwestward progradation of a clastic wedge into the Black Warrior basin did not block Appalachian detritus from moving toward the Ouachita region. This is an indication that sedimentary and tectonic recycling are both part of complex dispersal systems.

Isotopes, Neodymium, Turbidites

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Article Abstract:

It was wrong to describe different cycle types as 'end members' since each cycle represents a different phenomenon. Most of the cratonic eustatic cycles include the time of hiatus. However, the 'base-cutout' describes cycles with a basal hiatal surface generated by low-stand subaerial exposure. The generic cycle types show that the eustatic magnitude and cycle thickness are not the same even if the effects of compaction are taken into account.

Sea level, Natural cycles, Geology

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