Marsaglia, Kathleen M.¹, Dawn James¹, Shawn Shapiro¹, Alissa DeVaughn¹, Kevin Rivera¹, Luz Noelia Rodriguez¹ 
(1) California State University Northridge, Northridge, CA

ABSTRACT: Sand Provenance from Source-to-Sink: Preliminary Results from Two Case Studies in New Zealand

The aim of this study is to define actualistic models for sand provenance from source to sink across the terrestrial, transitional and marine components of two New Zealand margins. The first area, the Waipaoa Sedimentary System (WSS) on the east coast of North Island, was recently selected as a primary focus site for the MARGINS Source-to-Sink initiative, sponsored by the National Science Foundation. The modern tectonic setting of the WSS is that of an actively deforming forearc basin where older, mainly sedimentary, sequences are uplifted, weathered, eroded and recycled into younger deposits. The second area, the eastern South Island system (ESIS), comprises several source rivers, the Clutha, Waitaki and Rangitata, and a major offshore sink, the Bounty submarine fan. In this region sediments are mainly derived from low-grade metasedimentary to metamorphic rocks uplifted to the east of the Alpine Fault. Modern stream and beach samples have been collected, as well as representative fluvial gravel samples, and Holocene alluvium. Marine samples include offshore piston cores from shelf/slope areas, as well as core samples from an Ocean Drilling program site on the Bounty Fan. Representative source rock lithologies have also been sampled, in some cases along measured sections. Sand detrital modes indicate significant differences between the two margins, with the WSS being more enriched in sedimentary rock fragments and the ESIS being more enriched in quartz, feldspar and mica of likely metamorphic origin. There are significant trends in composition with grain size in the WSS. These data have implications for predicting reservoir quality in deep marine sand plays.

AAPG Search and Discovery Article #90026©2004 AAPG Annual Meeting, Dallas, Texas, April 18-21, 2004.