Comparison of measured and BSR-derived heat ﬂow values, Makran accretionary prism, Pakistan N. Kaul * , A. Rosenberger, H. Villinger FB Geowissenschaften, Universita ¨t Bremen, Postfach 330 440, D-28334 Bremen, Germany Received 29 April 1999; received in revised form 29 July 1999; accepted 2 August 1999 Abstract During the German research cruise SO-124 on RV Sonne (fall 1997) on the Makran accretionary wedge off Pakistan, geophysical investigations were carried out to study the thermal regime at a gas hydrate bearing sediment in a tectonically deformed accretionary wedge. On a transect perpendicular to the strike of the deformation front 42 heat ﬂow measurements were carried out, accompanied by seismic reﬂection experiments. The investigations start in the south in the abyssal plain and cover the continental slope up to 2300 m water depth. The aim of this study is to compare the BSR derived heat ﬂow (denoted as estimated heat ﬂow) with the values from measurements at the seaﬂoor. This requires the calculation of sediment physical properties at depth using empirical relation- ships between velocity and porosity. The value measured and corrected for sedimentation of 47 mW/m 2 south of the deforma- tion front is slightly higher than values reported by Hutchison et al. (Earth Planetary Sci. Lett. 56 (1981) 252–262). In all basins the estimated heatﬂow is signiﬁcantly higher than the measured values. As a result, temperatures at the BSR extrapolated from seaﬂoor measurements are 5–6 K lower than those taken from Gas hydrate stability considerations. As an overall trend the estimated as well as the measured heat ﬂow show a small decrease from the deformation front to the northward thickening prism. A similar observation was made at other accretionary wedges and described by Wang et al. (J. Geophys. Res. 98 (B3) (1993) 4121–4142) and Ferguson et al. (J. Geophys. Res. 98 (B6) (1993) 9975–9984). Within the slope basins heat ﬂow values show little variation, indicating predominantly conductive heat transport. Fluid ﬂow might occur at the bounding faults where we have little control. The effect of rapid sedimentation on the dynamic behavior of the BSR might also have a signiﬁcant inﬂuence on the estimated heat ﬂow values. Our data set shows clearly that detailed seismic surveys and good control of the subsurface velocity are absolute necessities for the comparison of measured and BSR-derived heat ﬂow values. However, the uncertainty of the velocity –porosity relationship together with a high and only approximately established sedimentation rate represent crucial but missing constraints which can be gained only by drilling.  2000 Elsevier Science B.V. All rights reserved. Keywords: Bottom simulating reﬂector; Heat ﬂow; Sedimentation 1. Introduction The marine part of the accretionary wedge of Makran in the Gulf of Oman, south of Pakistan (see Fig. 1), is well known for its wide spread occurence of gas hydrates, indicated by a prominent bottom simu- lating reﬂector (BSR), detectable in reﬂection seismic data from about 500 m water depth down to about 3300 m south of the deformation front. The Makran margin has been a target of several seismic investi- gations (White and Louden, 1982; Minshull and White, 1989; Minshull et al., 1992) and heat ﬂow Marine Geology 164 (2000) 37–51 MARGO 2710 0025-3227/00/$ - see front matter  2000 Elsevier Science B.V. All rights reserved. PII: S0025-3227(99)00125-5 * Corresponding author. www.elsevier.nl/locate/margeo