Tropical northeast Africa in the middle–late Eocene: Paleomagnetism of the marine-mammals sites and basalts in the Fayum province, Egypt Hamza Lotfy a,b , Rob Van der Voo a, * a Department of Geological Sciences, University of Michigan, Ann Arbor, 1100 North University, MI 48109-1005, USA b Department of Geology, Fac. Sci., El-Minia University, El-Minia, Egypt Received 9 June 2006; received in revised form 15 December 2006; accepted 20 December 2006 Available online 29 December 2006 Abstract The mid-late Eocene ‘‘Valley of Whales’’ in the Fayum province of Egypt contains hundreds of marine-mammals’ skeletons. Given its paleontological importance, we carried out a paleomagnetic study of the fossil-bearing formations. A sequence of basalts directly over- lying the upper Eocene rocks in three distant clusters within a 25 km-long NW–SE graben in the southwestern part of the area was also studied. Thermal demagnetization of three-axis IRM was used to identify and eliminate sites dominated by hematite and/or goethite as potential remanence carriers. Progressive thermal demagnetization of the NRM isolated a characteristic NNE–SSW dual-polarity direc- tion with a shallow inclination that passes both tilt and reversal tests. The mean tilt-corrected direction of the sedimentary formations is D/I = 16°/30° (k = 50, a 95 =3°) yielding a paleomagnetic pole at 70°N/159°E. The anisotropy of magnetic susceptibility (AMS) indi- cated that the observed inclinations were free from inclination shallowing, as did the nearly identical characteristic remanence of the overlying basalt flows (with a tilt-corrected reversed-polarity direction of D/I = 198°/28° (k = 38, a 95 =7°) and a pole at 68°N/ 158°E). The new paleopoles place the Fayum province at a lower paleolatitude (15–17°N) than today (29.5°N), and point to the possible prevalence of tropical climate in northeast Africa during mid-late Eocene times. This tropical position is nearly identical to the paleol- atitudes extrapolated from the mean of 36 coeval poles rotated from the other major cratons and from Africa itself. The declinations show a minor easterly deviation from those predicted by extrapolation from other continents. This is interpreted as due to a small clock- wise rotation internal to NE Africa, possibly related to Red Sea/Gulf of Suez rifting after the late Eocene. The alternative explanation that the geomagnetic field had a non-zonal non-dipole field contribution is not favored. Ó 2006 Elsevier Ltd. All rights reserved. Keywords: Paleomagnetism; Paleolatitude; Zeuglodon; Eocene; Oligocene; Fayum province; Marine mammal fossils; Cetacea; Sirenea; Valley of Whales; Egypt; Terrestrial vertebrate fossils 1. Introduction Egypt is famous for its unique collection of Eocene marine-mammal and Oligocene terrestrial-vertebrate fos- sils. Since Schweinfurth’s discovery of the Eocene Archae- ocete whale remains in 1879 (Dames, 1883), the Fayum province became one of the most interesting areas in the world for vertebrate paleontologists. The marine mam- mals are embedded within the middle–late Eocene forma- tions in both Fayum and Mokattam, while Oligocene terrestrial vertebrates are only recorded from the Qatrani formation north of Fayum province. For over a century, the terrestrial vertebrates and the marine mammals of the Fayum province have been thoroughly studied by sci- entific expeditions (Simons and Rasmussen, 1990; Ginge- rich, 1992). To the southwest of Cairo, the Fayum province forms a large circular depression adjacent to the Nile Valley (Fig. 1), encircled by a prominent multi-story escarpment rising for 250–350 m. Along the western edge of the depres- sion, the Valley of Whales or ‘‘the Zeuglodon Valley’’ (Fig. 1) is an open exhibit museum where hundreds of 1464-343X/$ - see front matter Ó 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.jafrearsci.2006.12.005 * Corresponding author. Tel.: +1 734 764 8322; fax: +1 734 763 4690. E-mail addresses: hiloutfy@yahoo.com (H. Lotfy), voo@umich.edu (R. Van der Voo). www.elsevier.com/locate/jafrearsci Journal of African Earth Sciences 47 (2007) 135–152