IGCP Project No. 381

Dear Colleague,

The IGCP Scientific Board has approved the proposal for a new IGCP Project on South Atlantic Mesozoic Correlations (SAMC), to which the IGCP serial number 381 has been ascribed. Therefore, it is with great pleasure that we send you the first issue of SAMC News. It is being distributed to individuals who have replied to our preliminary circular and to others, who we believe might be interested in participating actively in the project.

IGCP Project 381

Key Objectives :

Project proposers:

"IGCP is interdisciplinary, covering all specialities of geology, geophysics and geochemistry. IGCP maintains active interfaces with disciplines related to the geological sciences such as marine sciences, atmospheric sciences and biological sciences."

The project newsletter will be issued regularly (every four to six months) as a forum for exchanging information and promoting the integration and collaboration among project participants. Progress reports and research results by individuals and working groups, state-of-the-art reports, information on new collaborative programmes, discussions of scientific novelties within the scope of the project and announcements of forthcoming meetings will be among the topics covered by the newsletter. We invite all participants of SAMC to send us announcements, descriptions and short reports of current research work, information on projects being planned, underway, or recently completed, which relate to the scope of SAMC, literature reviews, etc. to be published in the next issues of the Newsletter. References of papers and abstracts in preparation, in press, or recently published will be compiled and listed in each issue. Please report them for inclusion in our newsletters and annual reports, by sending to the SAMC Secretariat a list of your papers in press and four offprints of published papers (of which two will be forwarded to the IUGS/IGCP Secretariat). Comments and discussions of problems within the areas of interest will be especially welcome. For all written communications please submit a printout of the text and a diskette containing the text file in Microsoft Word, WordPerfect, Nisus or ASCII format (Macintosh or IBM/Windows). Alternatively, texts may be submitted by e-mail to (E. Koutsoukos): bvb5@c53000.petrobras.anrj.br Do not send text for the Newsletter by fax.

Introduction

The Mesozoic sedimentary succession of the South Atlantic marginal and oceanic basins offers an excellent opportunity for major interdisciplinary efforts towards the understanding of processes of basin evolution on passive continental margins. The biostratigraphical and palaeobiogeographical characteristics of these depositional sequences are of foremost significance for studies of the early geological history and subsequent palaeoceanographic evolution of the South Atlantic Ocean. Cretaceous non-marine deposits, proto-marine evaporites and overlying marine rocks are widespread in outcrop, subcrop and in the ocean basins. The marine record is particularly well developed, beginning in the Jurassic in the southern- and northernmost South Atlantic and in the Early Cretaceous in the northern and equatorial South Atlantic.

However, despite half a century of intensive geological studies, few attempts have as yet been made to integrate data from the various basins into a wider, common geological framework. Stratigraphical events recorded in one basin are rarely correlated beyond the immediate adjacent areas into a more global context. Usually, local tectonic events and eustatic sea-level changes are thought to be the main control of sedimentation. Global climatic changes, which exercise a durable and direct imprint on the geological record by controlling biogenic productivity, sediment accumulation rates and biotic distribution trends, are seldom taken into consideration.

Moreover, a number of features of the geology of the South Atlantic are still poorly understood, such as: (1) the delayed development of fully marine successions as a result of the long-term topographic high created by the Walvis Ridge hot spot to the south and the late separation of the equatorial rift basins in the northwest; (2) the resultant fluvio-lacustrine mega-systems and the Aptian salt basin, with their characteristic physico-chemistry and influence on global climate; and (3) the oceanic circulation patterns in the Late Cretaceous and Palaeogene.

Until recently mainly localized data, such as local seismic grids and the results of geological surveys, were all that were available for correlation work. This has resulted in the current plethora of local names and stratigraphic scales that cannot be systematically related. However, as a result of the creation of regional data sets, such as seismic grids and Seasat gravity maps, the past ten years have seen the initial unravelling of the true tectonic framework of the basins. Unfortunately, progress and understanding on all fronts remain severely hindered by the lack of a rigorous integrated stratigraphic framework.

For researchers, the establishment of a modern, rigorously controlled stratigraphic framework will provide the means for determining answers to a wide range of local, regional and global correlation issues. These include:

• 1) Pre-Cretaceous, proto-rift events of the southern and northern South Atlantic.
2) The time and facies framework of the Cretaceous rift sequence and the ensuing drift phases. Currently the exact time of onset of the rifting is not known, neither is the exact timing of the drift phase.
3) The rift and drift ties to interior Africa, interior South America and the geoid as a whole. (Unravelling of the apparently relatively simple rift history of the South Atlantic may ultimately yield the templates needed in order to better understand and model more complex rift margins, such as those of the North Atlantic.)
4) Reliable biostratigraphic correlations for testing the radiometrically determined ages of flood basalts in Brazil and Namibia through the dating of interbedded rift volcanics and sedimentary rocks. A better understanding of the extent, nature, and thermal and topographic influence of the Walvis Ridge hot spot as well as the postulated Niger Delta hot spot will also emerge.
5) The nature and origin of the globally unique "Neocomian"-early Aptian fluvio-lacustrine mega-systems with their abundance of rich hydrocarbon source rocks. The lakes may have been large enough to exercise global effects on the biosphere and may provide clues to the Cretaceous warming phase and to dysoxic-anoxic events. The lakes may also contain pre-late Aptian salts and as yet unrecognised evidence of marine phases. (Barremian organic geochemistry suggests early marine links, whilst the first Red Sea-type segments of oceanic crust are thought to have formed during that time.)
6) The nature and origin of the unique Aptian salt basin.
7) The effects of the Aptian balt basin on global climate and sea-level changes. (It has been hypothesised that the global Aptian sea level drops on the Exxon chart are related to catastrophic, Messinian-type inundations of desiccated South Atlantic rift basins.)
8) The development of the Late Cretaceous and Palaeogene dysoxic-anoxic cycles: again, the size of the basins does not exclude global warming implications.
9) Following consolidation of the issues mentioned above, a more precise sequence-stratigraphic framework for the South Atlantic.

For hydrocarbon exploration the consequences are obvious: lower risks and more discoveries through better understanding. For example, current South Atlantic oil reserves are 11 BBOR (Gabon to Angola) and 19 plus BBOR (Brazil). However, if the hydrocarbon reservoirs and migration pathways can be located using a reliable sequence stratigraphy, the proved source rock volumetrics are sufficient to support far greater reserves. The metallic and industrial mineral industries will profit through improved understanding of Phanerozoic mineral generation systems. For example, unravelling of the Cretaceous rift events, may yield the plumbing systems needed for new onshore base-metal deposits.

Scope and Objectives

The principal aim of the proposed project is to promote interdisciplinary and, most importantly, integrated international and intercontinental correlative studies of the Mesozoic sedimentary basins of the South Atlantic Ocean, including its marginal basins in Africa, West Antarctica and South America. New research data will contribute to establishing a well-defined standard stratigraphical scale for the Mesozoic South Atlantic successions, to further improving our understanding of the nature and sequence of major geological events during the formation of the South Atlantic and the global impact of these events, as well as to improving the basis for hydrocarbon and mineral exploration in the area.

We propose the present-day geographic characterization of the South Atlantic as a convenient means to define the areas covered by the project. Thus, the marginal basins along northeastern and equatorial South America (from Santos to Amapa in Brazil, Guyana, Venezuela, northern Colombia), the Caribbean and Central America, and their correlative central and equatorial West African basins (from Angola to the Senegal-Mauritanian and western Morocco basins) will be included as part of the northern South Atlantic. This wide approach is particularly important as a means to investigating the Cretaceous links between central North Atlantic-western Tethyan provinces and the incipient South Atlantic. For the southern South Atlantic (south of the Rio Grande-Walvis Ridge) the areas from southeastern Brazil, Uruguay, Argentina, southern Chile, West Antarctica and southwestern Africa will be covered. The understanding of the early geological and oceanographic links between South America, West Antartica and Africa demands a thorough investigation of the southernmost sites.

In order to reach the project goal the following broad topics will be pursued as primary research tasks:

(1) To achive, through international scientific cooperation and joint-ventures of working groups, a fully integrated and refined stratigraphical and geochronological framework (with regards to biostratigraphy, magnetostratigraphy, geochemistry, seismic stratigraphy, sequence stratigraphy, cyclostratigraphy and event stratigraphy), which can be applied to the Mesozoic non-marine and marine sequences of the South Atlantic, thereby enhancing interbasinal and intercontinental stratigraphical correlation.

(2) To provide interdisciplinary stratigraphical data that allow the reconstruction of the palaeogeographical and palaeoceanographical history of the South Atlantic during the Mesozoic.

(3) To investigate the nature and magnitude of locally recorded geological and biological events and to explain their possible global significance.

Work Plan

The project will be carried out by individuals and research groups. Data and results will be presented and discussed at conferences and in workshops, where specific problems will be clarified.

Frequent research meetings (working-group sessions, when required, and general meetings, at least annually) will be held. We envisage these meetings as a most important feature for the success of the project, as a means of stimulating new research to be carried out within the scope of the project, as well as of coordinating ongoing research and facilitating scientific exchange and cooperation between specialists from different countries.

We envisage close collaboration with the ongoing IGCP projects 322 'Jurassic Events in South America' and 362 'Tethyan and Boreal Cretaceous', the latter in particular regarding Cretaceous studies of northern South Atlantic sites.

A group of regional coordinators for the project have been designated (see address list below). They will be responsible for liaisonamong participants, for disseminating information about the progress of the project and forthcoming meetings, and for stimulating and coordinating research in their fields of expertise. Additional working groups for the study of selected topics will be formed during the initial stage of the project.

Funding

Financial support for the scientific activities of the project should be sought by participants from governmental and other funding agencies, in particular where collaborative research has been set up. Please note that funding of research activities within the project is the responsability of individual participants or groups, not of IGCP/Unesco, the project leaders or coordinators. Limited IGCP support is provided particularly to facilitate participation in meetings, workshops and field excursions by participants from developing countries who contribute actively to the project.

Concrete Results Expected

Expected results of the project will be:

(1) integrated stratigraphical data sets, comprising intercalibrated biostratigraphical zonation schemes, magnetostratigraphy, sedimentary geochemistry (organic geochemistry, stable isotopes and trace elements), sedimentology, sequence stratigraphy and tectonostratigraphy;

(2) a high resolution event stratigraphy (bioevents, long- and short-term chemostratigraphic events, eustatic fluctuations), testing the synchroneity of regional events and their relationship with tectono-sedimentary and/or climatically-induced variations and global events;

(3) integrated regional models of basin development and evolution;

(4) a series of regional, evolutionary palaeogeographical maps, at 1:500,000 scale, from the last phase of Gondwana to the fully oceanic settings at the end of the Mesozoic, showing palaeoenvironments and the general geological and stratigraphic framework;

(5) general palaeogeographical maps of the South Atlantic, at 1:10,000,000 scale;

(6) biogeographical maps, at 1:10,000,000 scale, with the patterns of distribution of important micro- and macrofossil groups for selected time-intervals;

(7) palaeoceanographical maps, at 1:10,000,000 scale, with inferred bottom and surface circulation patterns;

(8) detailed regional models of the geological setting and genesis of known and potential mineral resources, with sections illustrating the different stratigraphic plays, maps of occurrences (at 1:500,000) and estimates of reserves.

(9) publications of results from the project, proceedings of working group meetings and special volumes, which will include major interdisciplinary contributions of geological correlation within a regional framework.

Outline of Project Meetings

An information meeting was held on 19 July 1994 during the 12th African Micropalaeontological Colloquium and the simultaneously held 2nd Colloquium on the Stratigraphy and Palaeogeography of the South Atlantic at Angers, France. The meeting was attended by 40 persons, including the two project proposers and three regional coordinators (I. de Klasz, N. R. Cameron and S. W. Petters). A draft proposal was presented and discussed, a number of key objectives identified and a schedule for project meetings set up. The attenders expressed their massive support for the intended project proposal.

In July 1995 an inaugural project meeting will be held in Uberaba, Minas Gerais, Brazil, in conjunction with the 14th Brazilian Palaeontological Congress (see below). The meeting will also be used to introduce the project to the Latin American scientific community.

A general meeting is planned for 1996 to be held in Aracaju, Sergipe, northeastern Brazil. Continental Cretaceous sections are widespread in northern Brazil, from which an abundant reptilian fauna has been recorded. Field trips will be organized to visit some of these sites, as well as to sample and investigate a typical rift-phase marginal basin (Reconcavo, Bahia) and the Cretaceous marine outcrop record (Sergipe, Pernambuco-Paraiba and Potiguar basins). The 1996 meeting will focus on ongoing research and the state-of-the-art of geological correlations and the bio-chronostratigraphic frameworks currently adopted for the South Atlantic Mesozoic sequences. The problems identified will prompt the proposal of clearly defined research topics and specific research targets for the forthcoming year(s). For 1996 an European regional meeting is also being planned, to be held in Germany, simultaneously with the 2nd European Round Table on the Palaeontology and Stratigraphy of South America.

The locations for the next annual project meetings are as follows (provisionally):

1: Cameroon (1997), in conjunction with the 13th African Micropalaeontological Colloquium; 2: Argentina (1998); 3: Nigeria (1999); and 4: South Africa (2000). These are all key areas for the understanding of the geological links between West Antarctica, South America and Africa, and between the Austral and Tethyan realms.

Objectives of the meeting:

DAY (24 July)

DAY 2 (25 July)

2. Brainstorming among participants according to area of work.

Action groups:

• 1) northern South America
• 2) northern Africa
• 3) southern South America
• 4) southern Africa
• 5) western Antarctica

Suggested topics of discussion for the action groups:

• a) Objectives of the project.
• b) Research priorities (regional as well as general priorities for all groups).
• c) Discussion of feasible objectives to be reached within a 5 year project-term.
• d) Proposal for working-groups for fields of research and/or geographic areas.
• e) Proposal for working-group coordinators and forthcoming meetings (time, venue and topics of discussion).

3. Meeting of all participants with presentation of results by coordinators of the action groups.

4. Discussion of proposed ideas for integration in the project objectives.

5. Proposal and election of regional coordinators.

6. Election of project leaders.

7. Proposal for general and working-group meetings.

8. Discussion of possibilities of obtaining financial support for organizing and attending project meetings (travel and accomodation of participants).

We propose the following Working Groups to be erected initially:

• 1. Gondwana Palaeogeography and Stratigraphic Correlations.

- Integrated biostratigraphy, correlation of magneto- and biozones, sequence stratigraphy, timing of the main tectono-sedimentary events. - Triassic-Jurassic continental sequences from South America and Africa.

• 2. Lower Cretaceous Stratigraphic Correlations.

- Prerift and synrift sequences of the northern South Atlantic; marine sequences of the equatorial and southern South Atlantic.

• 3. Lower Cretaceous Palaeogeography.
• 4. Upper Cretaceous Stratigraphic Correlations.
• 5. Upper Cretaceous Palaeogeography and Palaeoceanography.

If you are interested in participating and presenting a paper, or for more information, please, write to E. Koutsoukos or to the Project Secretariat (address below). Send your abstract on Microsoft Word, WordPerfect, Nisus or ASCII, on either Macintosh or IBM/Windows-compatible diskettes. Alternatively, it may be submitted by electronic mail to: bvb5@c53000.petrobras.anrj.br. Do not send it by fax. The abstracts should be written in English with a maximum of 1000 words on two letter-sized (A4) pages. Papers can be presented either in oral or poster sessions. Each oral session will be given 25 minutes (approximately), with 5 minutes at the end of the session for an open forum.

For those also interested in participating in the 14th Brazilian Palaeontological Congress, registration can be done at the meeting place. If you wish to present a paper during the Congress, and have your abstract published in the Scientific Programme, deadlines are until the end of March (follow the instructions above for mailing abstracts to the project meeting).

Languages

The official languages at SAMC meetings will be English, French, Spanish and Portuguese, i.e. the main languages of the countries bordering the South Atlantic.

The IGCP Logotype and Project Publications

We wish to emphasize that all publications deriving from project research carried out by participants should be identified with the "IGCP/IUGS/UNESCO-hammer" logotype and the name and/or number of the project, with further reference in the Acknowledgments stating that "This paper is a contribution to IGCP Project 381, South Atlantic Mesozoic Correlations". This will greatly facilitate for official bodies to judge the output and success of the project. Please do not forget to send to the SAMC Secretariat four offprints of your published papers related to the project (of which two will be forwarded to the IUGS/IGCP Secretariat).

SAMC Secretariat

Please send your registration and enquiries about IGCP Project 381 (SAMC) to either one of the following secretaries:

(for English-speaking participants) Marcio R. Mello PETROBRAS-Cenpes/Divex/Segeq Cidade Universitaria, Quadra 7 - Ilha do Fundao BR-21949-900 Rio de Janeiro, RJ - Brazil Tel.: +55-21-5986460, Fax: 5986799 E-mail: bv77@c53000.petrobras.anrj.br

(for French-speaking participants) Mitsuru Arai PETROBRAS-Cenpes/Divex/Sebipe Cidade Universitaria, Quadra 7 - Ilha do Fundao BR-21949-900 Rio de Janeiro, RJ - Brazil Tel.: +55-21-5986440, Fax: 5986795 E-mail: bvb5@c53000.petrobras.anrj.br.

Peter Bengtson - Geologisch-Palaeontologisches Institut der Universitaet Heidelberg, Im Neuenheimer Feld 234, D-69120 Heidelberg, Germany. Tel.: +49-6221-568293 , Fax: 563940 or 565503, E-mail: nick@gmuk.dungeon.com

Alistair Crame - British Antarctic Survey, High Cross, Madingley Road, Cambridge CB3 0ET, UK. Tel.: +44 1223 251 443, Fax: +44 1223 62616.

Ivan de Klasz - "La Verdiane", 74 Av. du Mont Alban, F-06300 Nice, France. Tel.: +33-93-268843, Fax: 894820.

Eduardo A. M. Koutsoukos - PETROBRAS-Cenpes/Divex, Cidade Universitaria, 21949-900 Rio de Janeiro, RJ, Brazil. Tel. +55-21-5986440, Fax 5986795, Tel./Fax(h) 3258306, E-mail: bvb5@c53000.petrobras.anrj.br

Eduardo Musacchio - Lab. de Bioestratigrafia, Universidad Nacional de La Patagonia, Ciudad Universitaria km 4, 9000 Comodoro Rivadavia, Chubut, ARGENTINA. Tel./Fax: +54-967-39339, E-mail: aldo@unpbib.edu.ar

Eduardo B. Olivero - Centro Austral de Investigaciones Cientificas (CADIC), Av. Malvinas Argentinas s/n , C.C. 92, 9410 Ushuaia, Tierra del Fuego, Argentina. Tel.: +54-901-22 310/312/314, Fax: 30644.

Sunday W. Petters - Department of Geology, MOBIL/NNPC Chair of Petroleum Geology, University of Calabar, P.O. Box 3654, Calabar, Nigeria. Tel.: 224747 or 224748, ext. 350, Telex: 65103 UNICAL.

Peter Szatmari - PETROBRAS-Cenpes/Divex/Setec, Cidade Universitaria, 21949-900 Rio de Janeiro, RJ, Brazil. Tel.: +55-21-5986435, Fax: 5986792.

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Last Update 30 January 1996