Marine Micropaleontology 47 (2002) 17^70 www.elsevier.com/locate/marmicro Age and paleoenvironment of the Maastrichtian to Paleocene of the Mahajanga Basin, Madagascar: a multidisciplinary approach S. Abramovich a;Ã, G. Keller a, T. Adatte b, W. Stinnesbeck c, L. Hottinger d, D. Stueben e, Z. Berner e, B. Ramanivosoa f , A. Randriamanantenasoa g a Department of Geosciences, Princeton University, Princeton, NJ 08544, USA b Geological Institute, University of Neucha“tel, CH-2007 Neucha“tel, Switzerland c Geological Institute, University of Karlsruhe, D-76128 Karlsruhe, Germany d Museum of Natural History, CH-4001 Basel, Switzerland e Petrography and Geochemistry Institute, University of Karlsruhe, D-76128 Karlsruhe, Germany f Muse¤e Akiba, PO Box 652, Mahajanga 401, Madagascar g De¤partment des Sciences de la Terre, Universite¤ de Mahajanga, Mahajanga, Madagascar Received 30 May 2001; received in revised form 1 May 2002; accepted 8 May 2002 Abstract Lithology, geochemistry, stable isotopes and integrated high-resolution biostratigraphy of the Berivotra and Amboanio sections provide new insights into the age, faunal turnovers, climate, sea level and environmental changes of the Maastrichtian to early Paleocene of the Mahajanga Basin of Madagascar. In the Berivotra type area, the dinosaur-rich fluvial lowland sediments of the Anembalemba Member prevailed into the earliest Maastrichtian. These are overlain by marginal marine and near-shore clastics that deepen upwards to hemipelagic middle neritic marls by 69.6 Ma, accompanied by arid to seasonally cool temperate climates through the early and late Maastrichtian. An unconformity between the Berivotra Formation and Betsiboka limestone marks the K^Tboundary, and juxtaposes early Danian (zone Plc? or Pld) and latest Maastrichtian (zones CF2^CF1, Micula prinsii) sediments. Seasonally humid warm climates began near the end of the Maastrichtian and prevailed into the early Danian, accompanied by increased volcanic activity. During the late Danian (zones P1d^P2), a change to seasonally arid climates was accompanied by deepening from middle to outer neritic depths. ß 2002 Elsevier Science B.V. All rights reserved. Keywords: Madagascar; Maastrichtian; Paleocene; age; paleoclimate; paleoenvironment 1. Introduction Madagascar plays an unique role in the geo- * Corresponding author. Tel.: +1-609-258-4117; graphic and biological history of the Earth. Ever Fax: +1-609-258-1671. since its separation from Africa 125^130 Ma ago E-mail address: [email protected] (S. Abramovich). and its separation from India and the Seychelles 0377-8398 / 02 / $ ^ see front matter ß 2002 Elsevier Science B.V. All rights reserved. PII: S0377-8398(02)00094-4 MARMIC 894 29-10-02 18 S. Abramovichet al. / Marine Micropaleontology 47 (2002) 17^70 about 88 Ma ago (e.g. Storey et al., 1997; Rogers the age of the marine strata overlying the di- et al., 2000), Madagascar developed a unique nosaur-bearing beds of the Mahajanga Basin; Gondwana paleofauna, and high endemism in ter- (2) lithology, bulk rock and clay mineral compo- restrial and fresh water faunas and £oras persist- sitions to determine the depositional environ- ing until today. Late Cretaceous dinosaur-rich ment; (3) analysis of planktic foraminifera, larger vertebrate faunas of the Mahajanga Basin have benthic foraminifera and macrofossil assemblages long been known and there are many recent stud- to characterize the local marine ecosystem and ies (Forster et al., 1996; Krause and Hartman, identify paleoceanographic events; (4) stable iso- 1996; Krause et al., 1997, 1999; Sampson et al., tope analysis to evaluate climate and productivity 1998). The uppermost dinosaur faunas appear in trends; and (5) correlation and comparison of the Anembalemba Member of the Maevarano faunal and climatic events with global trends. Formation, and are overlain by marine beds of the Berivotra Formation, followed by the Danian Betsiboka limestone. A number of studies have 2. Methods corroborated a Maastrichtian age for the marine sediments of the Berivotra Formation based on Marine Maastrichtian to Danian sections were sporadic calcareous nannofossil and planktic fo- studied from two localities previously reported by raminiferal data (e.g. Perch-Nielsen and Pomerol, Rogers et al. (2000) in the Mahajanga Basin of 1973; Bignot et al., 1996, 1998; Janin et al., 1996), northwestern Madagascar (Fig. 1). One is the type but no systematic study has been published. Rog- locality of the Berivotra Formation near Berivo- ers et al. (2000) argued that the terrestrial se- tra village, and the second is in a cement quarry quence is time transgressive and of late Maas- near the village of Amboanio. The sections were trichtian age in the Berivotra type area, and measured and described with particular emphasis therefore contemporaneous with the dinosaur- on bioturbation, trace fossils, macrofossil hori- rich vertebrate faunas recovered from the Deccan zons, hardgrounds and erosion surfaces. At the basalt sequence of India and dated between 67.5 Berivotra type section, in all 36 samples were col- and 65 Ma. lected at approximately 1-m intervals and at As part of a broader project aimed at develop- 20-cm intervals at the top. At Amboanio, totally ing a global high-resolution faunal, climatic and 54 samples were collected at 20^50-cm intervals, environmental history for the late Cretaceous to with the uppermost meter of the Berivotra For- early Tertiary, we have investigated two sections mation sampled at 10-cm intervals. from the Mahajanga Basin of Madagascar. One is For the micropaleontological studies, marl li- the type section of the Berivotra Formation and thologies were disaggregated in tap water and the second is a cement quarry near the village of washed through a s 63-Wm sieve until clean fora- Amboanio. The primary objectives of this study miniferal residues were recovered. The washed are to determine the biostratigraphy, provide age samples were oven-dried at 50‡C, and sifted control for the various rock units, and reconstruct through a s 150-Wm sieve. At the Berivotra sec- the environmental history of the Mahajanga Ba- tion, the s 150-Wm sieved residues are composed sin based on macrofaunas and microfaunas, sed- mostly of small benthic foraminifera, larger imentology, mineralogy and stable isotopes. Our benthic foraminifera, ostracods, bivalves and analytical approach includes: (1) microfossil stra- bryozoans, with relatively few planktic foraminif- tigraphy based on planktic foraminifera and aug- era. Therefore, only species census data was ob- mented by calcareous nannofossils to determine tained from the s 63-Wm size fraction (Table 1). Fig. 1. (a). Paleolocation of Madagascar and Site 525A during the late Maastrichtian. Note the similar paleolatitude positions of these two localities. (b). Simpli¢ed geographic map of Madagascar Island showing the locality of the Mahajanga Basin. (c). Late Cretaceous geology of the Mahajanga Basin (modi¢ed after Rogers et al., 2000) and locations of the two sections analyzed. MARMIC 894 29-10-02 S. Abramovichet al. / Marine Micropaleontology 47 (2002) 17^70 19 MARMIC 894 29-10-02 20 Table 1 Planktic foraminiferal occurrences at the Berivotra section Madagascar Sample 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 Depth (m) 5.6 6 6.2 11 12 13 14 15 16 18 19 20 21 22 23 24 25 26 27 28 29 Planktic foraminiferal zones CF2^1 CF4 CF5 CF6 (CF) Calcareous nannofossil zones Micula prinsii Lithraphidites quadratus (CC25c) Abathomphalus mayaroensis x Archaeoglobigerina blowi x A. cretacea xx x x S. Abramovichet al. / Marine Micropaleontology 47 (2002) 17^70 Heterohelix dentata xxxxxxxxxxxxxxxxxxxxx H. globulosa xxxxxxxxxxx xxxxxxxxx H. labellosa x H. planata xx H. rajagopalani xx xxx x x Gansserina gansseri x MARMIC 894 29-10-02 G. weidenmayeri x Globigerinelloides aspera x G. a¡. ultramicrus x G. subcarinatus x Globotruncana aegyptiaca xx xxxxxxxxxxxxxx xx G. arca x xxxxxxxxxxxxxxxxxxx G. bulloides xx G. duepeblei xxx G. esnehensis xx x G. falsostuarti xxxx xxx G. insignis x G. linneiana xx G. mariei x G. orientalis xx xxxxx x xxx xx G. rosetta xxxxx x G. ventricosa xxxxx x xx Globotruncanella havanensis x G. petaloidea x Globotruncanita angulata xxx x x x G. pettersi G. stuarti xxxxxxxxxxxxxx G. stuartiformis x xxxxxxxxxxx x xx x Gublerina cuvillieri xx x Guembelitria cretacea xxxxxxxxxxxxxxxxxxxxx G. dammula xxxxxxxxxxxxxxxxxxxxx Laheviheterohelix glabrans x Table 1 (Continued). Sample 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 Depth (m) 5.6 6 6.2 11 12 13 14 15 16 18 19 20 21 22 23 24 25 26 27 28 29 Planktic foraminiferal zones CF2^1 CF4 CF5 CF6 (CF) Calcareous nannofossil zones Micula prinsii Lithraphidites quadratus (CC25c) Planoguembelina acervulinoides x xx x xxxxxx P. brazoensis xxx P. carseyae xx Pseudoguembelina costulata xx x S. Abramovichet al. / Marine Micropaleontology 47 (2002) 17^70 P. excolata xxxxxxx x x P. hariaensis x P. kempensis x P. palpebra xx x Pseudotextularia deformis xx xxxxxxxx xxxx x x P. elegans xxxxxxxxxxxxxxxxxxxxx MARMIC 894 29-10-02 P. intermedia xx xx xxxxx xxx xx Racemiguembelina fructicosa xx R. powelli x xxxxxxxxx Rosita contusa xxxx xx R. fornicata x R. patelliformis xx R. plicata xxxxxxxx R. plummerae xxx R. wal¢schensis xx x x xxx Rugoglobigerina hexacamerata x xx x xxx R. macrocephala xx R. milamensis xx R. pennyi x xx x xx xxx R. rugosa xxxxxxxxxxx xxx x x R. scotti x xxxxx xxxxx x xxx x R. cf. Scotti xx x x x x = present. 21 22 S. Abramovichet al. / Marine Micropaleontology 47 (2002) 17^70 Table 2 Relative percent abundances of planktic foraminifera in the 63^150-Wm size fraction at the Amboanio Quarry, Madagascar Sample 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 18 19 20 22 Depth (m) 0 0.7 1.1 1.5 1.9 2.3 2.7 3.1 3.5 4.02 4.26 4.44 4.6 4.8 5 5.2 5.56 5.72 5.88 6.34 CF zones (planktic foraminifera) CF4 CF3 Calcareous nannofossil zones Lithraphidites quadratus (CC25c) Archaeoglobigerina blowi 1 x x xx x xxx A.