Slides - Positive 18O:16O Negative 18O:16O Summary --- The...

Info iconThis preview shows pages 1–5. Sign up to view the full content.

View Full Document Right Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: Positive 18O:16O Negative 18O:16O Summary --- The oxygen isotopic proxy thus shows that northern hemisphere glaciation fluctuates in very regular periods. Advances and retreats every ~41,000 yrs from 1.8 Ma to 600,000 years ago. Since then, major changes have occurred at ~100,000 yr periods, lesser ones at ~23,500 yrs. Continuing with the analysis of the oxygen Isotope proxy, .. Positive 18O:16O An analysis of the frequencies within the oxygen isotope curve reveals these 3 periods whose signals exceed noise! These periods must be explained to explain glaciation on this type of time scale. 100,000 21,000 41,000 Frequency (1/kyr) S i g n a l A m p l i t u d e noise Questions that Arise Are we sure all those glacial features and deposits are all the same age? (e.g., maybe the conglomerates are from different (smaller) glaciers in different places at different times) If more than one, how many? And why does climate cool and ice sheets advance; why does climate warm and those sheets retreat? Superposition of tills and C14 dates of the intervening soils indicate at least 4 glacial periods in North America (and 6 in Europe). Older glaciers may have existed but their deposits would have been reworked by younger ice sheets. Oxygen isotope proxy indicates >30 different northern hemisphere glacial and intervening non-glacial times over the last 1.8 my, all occurring at some very distinct periodicities. Why does climate cool and ice sheets advance; why does climate warm and those sheets retreat?...
View Full Document

This note was uploaded on 03/31/2008 for the course GEOL 1020 taught by Professor Pranter during the Spring '07 term at Colorado.

Page1 / 20

Slides - Positive 18O:16O Negative 18O:16O Summary --- The...

This preview shows document pages 1 - 5. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online