159 Paleoclimatology/Paleoceanography II
Thursday, 8 November 2001
8:15 AM - 12:00 PM
FROM SAPROPEL TO RED MARL–ORBITALLY DRIVEN BEHAVIOR OF A CRETACEOUS SEA
Paper number: 159-4
Program: Technical Sessions
Time: 8:15 AM – 12:00 PM
Authors
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Alessandro GrippoUniv of Southern California, Los Angeles, CA
Abstract
Albian deep-water sedimentation in the Umbria-Marche facies of Italy (Mediterranean Tethys) shows complex rhythmic interbedding. Throughout Albian time the 20-ka precession drove cycles in primary productivity which resulted in marl-limestone couplets, of which the limestones, peaks in coccolith productivity, signal less fertile blue-water times. Eccentricity highs in the 95 ka short eccentricity cycle brought monsoonal regimes, upwelling, eutrophy, and bottom stagnation, punctuating the record with cm-scale sapropels. Prolonged eccentricity lows in parts of the long (406 ka) eccentricity rhythm brought dominance of zonally-driven warm, saline, nutrient-depleted waters and downwelling, resulting in episodes of red marl or red clay deposition. Episodes of strong obliquity forcing inserted additional sapropels. These sapropels are markedly distinct from the 300-ka episode of anoxia that produced oceanic anoxic event OAE 1b (the Urbino member).