Spatial and temporal distribution of biogenic carbonate and opal in deep-sea sediments from the eastern equatorial Pacific: implications for ocean history since 1.3 Ma

High-resolution records of glacial-interglacial variations in biogenic carb onate, opal, and detritus (derived from non-destructive core log measuremen ts of density, P-wave velocity and color; r greater than or equal to 0.9) f rom 15 sediment sites in the eastern equatorial (sampling resolution is sim ilar to 1 kyr) clear response to eccentricity and precession forcing. For t he Peru Basin, we generate a high-resolution (21 kyr increment) orbitally-b ased chronology for the last 1.3 Ma. Spectral analysis indicates that the 1 00 kyr cycle became dominant at roughly 1.2 Ma, 200-300 kyr earlier than re ported for other paleoclimatic records. The response to orbital forcing is weaker since the Mid-Brunhes Dissolution Event (at 400 ka). A west-east rec onstruction of biogenic sedimentation in the Peru Basin (four cores; 91-85 degrees W) distinguishes equatorial and coastal upwelling systems in the we stern and eastern sites, respectively. A north-south reconstruction perpend icular to the equatorial upwelling system (11 cores, 11 degrees N-8 degrees S) shows high carbonate contents (greater than or equal to 50%) between 6 degrees N and 4 degrees S and highly variable opal contents between 2 degre es N and 4 degrees S. Carbonate cycles B-6, B-8, B-10, B-12, B-14, M-2, and M-6 are well developed with B-10 (430 ka) as the most prominent cycle. Car bonate highs during glacials and glacial-interglacial transitions extended up to 400 km north and south compared to interglacial or interglacial-glaci al carbonate lows. Our reconstruction thus favors glacial-interglacial expa nsion and contraction of the equatorial upwelling system rather than shifti ng north or south. Elevated accumulation rates are documented near the equa tor from 6 degrees N to 4 degrees S and from 2 degrees N to 4 degrees S for carbonate and opal, respectively. Accumulation rates are higher during gla cials and glacial-interglacial transitions in all cores, whereas increased dissolution is concentrated on Peru Basin sediments close to the carbonate compensation depth and occurred during interglacials or interglacial-glacia l transitions. (C) 1999 Elsevier Science B.V. All rights reserved.