AAPG Bulletin, V. 83 (1999), No. 9, P. 1485-1501.

Physical Property Changes as a Monitor of Pelagic Carbonate Diagenesis: an Empirically Derived Diagenetic Model for Atlantic Ocean Basins¹

Jens Grützner² and Jürgen Mienert³

©Copyright 1999.  The American Association of Petroleum Geologists.  All Rights Reserved

¹Manuscript received February 5, 1998; revised manuscript received February 2, 1999; final acceptance March 16, 1999.
²GEOMAR Forschungszentrum für marine Geowissenschaften, Wischhofstr. 1-3, D-24148 Kiel, Germany; e-mail: [email protected]
³GEOMAR Forschungszentrum für marine Geowissenschaften, Wischhofstr. 1-3, D-24148 Kiel, Germany. Now at Department of Geology, University of Tromsø, Dramsveien 201,N-9037 Tromsø, Norway.

We acknowledge the financial support of the "Deutsche Forschungsgemeinschaft (DFG)." The manuscript was improved by the comments of J. W. Schmoker, R. E. Garrison, and one anonymous reviewer. 

ABSTRACT

A new physical model of carbonate diagenesis has been derived based on physical property measurements from 81 DSDP/ODP (Deep-Sea Drilling Project/Ocean Drilling Project) drill sites in the Atlantic Ocean. Changing depth gradients of porosity, bulk density, P-wave velocity (vertical and horizontal), and acoustic impedance characterize five successive diagenetic stages: (1) compaction of ooze, (2) breakage and dissolution of fossil tests, (3) formation of chalk through precipitation of calcite, (4) cementation, and (5) compaction of calcite crystals. Age-depth information from the drill sites was used to calculate the average duration of these processes in Atlantic Ocean basins. The model can predict carbonate sediment physical properties down to a burial depth of 1000 m. The model is presented for both lab and in-situ conditions and thus can serve as a standard for comparison with lab, log, and seismic measurements. An acoustic impedance vs. age curve derived from the model allows estimation of the initial and present-day diagenetic potential of carbonate sediments and chalk reservoirs.