AAPG Continuing Education Course Note Series #39: An Introduction to the Analysis of Ancient Turbidite Basins from an Outcrop Perspective
by: Emiliano Mutti, Roberto Tinterri, Eduard Remacha, Nicola Mavilla, Stefano Angella and Luca Fava

AAPG Continuing Education Course Note Series #39: An Introduction to the Analysis of Ancient Turbidite Basins from an Outcrop Perspective

AN INTRODUCTION TO THE ANALYSIS OF ANCIENT
TURBIDITE BASINS FROM AN OUTCROP PERSPECTIVE

by

Emiliano Mutti¹, Roberto Tinterri¹, Eduard Remacha¹*, Nicola Mavilla¹,
Stefano Angella¹ and Luca Fava¹

AAPG Continuing Education Course Note Series #39

Published by
The American Association of Petroleum Geologists
Tulsa, Oklahoma, U. S. A.
Printed in the U. S. A.

Published by the Education Department of
The American Association of Petroleum Geologists
Copyright © 1999 by
The American Association of Petroleum Geologists
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ISBN: 0-89181-188-5

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Cover from: Proterozoic Turbidite System, Namibia. Note the impressive lateral continuity of turbidite sandstone lobes. Younging direction is from left to right (Mutti et al., 1999).

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An Introduction to the Analyses of Ancient Turbidite Basins from an Outcrop Perspective

Course Text

NOTE

These course notes, co-authored by some of my graduate students involved in deep-water and fluvio-deltaic sedimentation research, summarize four decades of field work by the senior author in many turbidite basins worldwide and particularly, in co-operation with Eduard Remacha during the last 15 years, in the Eocene strata of the south-central Pyrenean foreland basin.

Most of the data and interpretations presented are previously unpublished and therefore, in many respects, the notes constitute a kind of research paper, particularly where facies, processes and cyclicity are concerned. We are aware that many of our conclusions may seem controversial and far from conventional. However, we felt that in recent years there has been little variety in the approach to turbidites and there was a need for fresh air from the area of outcrop studies.

For the sake of brevity, many problems are dealt with in a very cursory manner but the reader can take advantage of the many bibliographic references which will help him to delve deeper into these problems.

The main scheme of these notes is an attempt to consider turbidite sedimentation of ancient orogenic belts as closely related to that of marginal flood-dominated fluvio-deltaic systems, both types of sedimentation being primarily controlled by tectonism and high-frequency climatic variations. Catastrophic floods are thought to represent the fundamental process of this kind of sedimentation which we have provocatively termed "fluvio-turbidite sedimentation". This kind of sedimentation simply suggests that the final depositional zone of highly-efficient, flood-dominated river systems is located in adjacent deep-water basins and is recorded by turbidite accumulations. Of course, we are aware that while catastrophic floods directly control hyperpycnal flows in shallow marine regions, the relations between hyperpycnal flows and deep-water turbidity currents are not that simple and sediment failures and large-scale bed erosion also play a major role here. In particular, we try to emphasize in these notes that real turbidity currents can originate only after a

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substantial flow acceleration along steep submarine conduits.

Turbidity currents are considered as bipartite currents in which a basal granular layer flows primarily due to inertia conditions and excess pore pressure and is overlain by a turbulent layer which will eventually rework and outdistance the final deposit of the inertia layer in a basinward direction. This scheme strictly conforms to the definition of a turbidity current as given by Kuenen (in Sanders, 1965), thus permitting us to overcome many conceptual and terminology problems discussed in subsequent literature. An extreme example of these problems can be found in a recent paper by Shanmugam (in press), who attempts to dismantle the turbidite paradigm. Paradigms are generally short-lived by nature: nonetheless, turbidites apparently have some life in them yet.

In my experience, it is apparent that courses for petroleum geologists are not infrequently devised to reassure them that existing models are good and that these models have a highly predictive value. Most of these models were actually proposed long ago and would benefit from certain modifications (see Mutti and Normark, 1987). My strong conviction, after many years, is that turbidites are still basically poorly understood and we cannot offer, at present, more than our honest ignorance or little knowledge in this respect. This ignorance is increasingly enhanced by papers which base themselves on terminology problems and disputes, while studies based on basinwide stratigraphic analyses ? the only approach by which a geologist can significantly frame facies and facies associations and attempt to develop an understanding of their formative processes ? are becoming increasingly rare. 

Emiliano Mutti

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AN INTRODUCTION TO THE ANALYSIS OF ANCIENT TURBIDITE BASINS FROM AN OUTCROP PERSPECTIVE

By

Emiliano Mutti, Roberto Tinterri, Eduard Remacha*, Nicola Mavilla, Stefano Angella and Luca Fava

Dipartimento di Scienze della Terra, Universit? di Parma,
viale delle Scienze 78, 43100 PARMA, Italy
e-mail : [email protected]

*Departament de Geologia, Universitat Autonoma de Barcelona, edifici CS, 08193
Bellaterra, BARCELONA, Spain

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