Physical Sciences and Mathematics Commons^™

Does The Great Valley Group Contain Jurassic Strata? Reevaluation Of The Age And Early Evolution Of A Classic Forearc Basin, Kathleen D. Surpless, Stephan A. Graham, Jacob A. Covault, Joseph L. Wooden

Kathleen D. Surpless

The presence of Cretaceous detrital zircon in Upper Jurassic strata of the Great Valley Group may require revision of the lower Great Valley Group chronostratigraphy, with significant implications for the Late Jurassic–Cretaceous evolution of the continental margin. Samples (n = 7) collected from 100 km along strike in the purported Tithonian strata of the Great Valley Group contain 20 Cretaceous detrital zircon grains, based on sensitive high-resolution ion microprobe age determinations. These results suggest that Great Valley Group deposition was largely Cretaceous, creating a discrepancy between biostratigraphy based on Buchia zones and chronostratigraphy based on radiometric age dates. These …

Recent Discoveries And A Review Of The Ordovician Faunas Of New Zealand, Ian Percival, Roger Cooper, Yong Yi Zhen, J Simes, Anthony Wright

Anthony Wright

Fossiliferous Ordovician rocks are of limited extent in New Zealand, being largely restricted to northwest Nelson and Westland in the northern part of the South Island, with some isolated exposures at the southern extremity of Fiordland (Fig. 1). The known stratigraphic record, though incomplete, covers much of the period, and new information from study and revision of old collections (mostly dating from the 1960s and 1970s) continues to fill in the gaps. These data are critical to a better understanding of New Zealand’s place in the Ordovician world, when it occupied an isolated position facing the palaeo-Pacific Ocean offshore to …

Darriwilian (Middle Ordovician) Conodonts From Thompson Creek, Nelson Province, New Zealand, Yong Yi Zhen, Ian G. Percival, Roger A. Cooper, John E. Simes, Anthony J. Wright

Anthony Wright

A well preserved Middle Ordovician conodont fauna of 24 species has been recovered from seven samples of a small limestone lens exposed in Thompson Creek, northwest of Nelson, on the South Island of New Zealand. The presence of Histiodella holodentata, Baltoniodus? sp., Paroistodus originalis, P. horridus, Periodon macrodentatus, Protopanderodus sp. cf. P. varicostatus, Costiconus ethingtoni and Venoistodus balticus in the fauna indicates a Darriwilian (late Da2 to mid Da3) age. The occurrence of Ansella jemtlandica, Baltoniodus? sp., Periodon macrodentatus, Spinodus sp., Spinodus? sp. and Histiodella holodentata suggests a relatively deeper water (outer shelf to slope) setting, comparable with contemporaneous faunas, …

Forum On The Flood/Post-Flood Boudary, Marcus R. Ross

Marcus R. Ross

The location of the Flood/post-Flood boundary is an important issue for Flood geology because it is the starting point for a host of research questions. Many papers have been published on this topic, but its placement is still controversial. Three main views are advocated: a low Flood boundary in the Paleozoic or below, a boundary at or near the Cretaceous-Tertiary boundary (now the Cretaceous/Paleogene boundary), and a variable boundary towards the upper Cenozoic but with each geographical area to be evaluated on its merits.

In 2012, Marcus Ross, published a biostratigraphic analysis and argued that a Flood/post-Flood boundary at or …