Thermochronological data from Sudan in the frame of the denudational history of the Nubian Red Sea margin

摘要

Low-temperature thermochromology provides information on the timing of rifting and denudation of passive margins, and the Red Sea with its well-exposed, young rift margins is a suitable Setting for its application. Here we present new apatite fission-track (AFT) data from Sudan northern hinterland and Red Sea coastal areas. From the former region we obtained ages between 270 +/- 2 Ma ad 253 +/- 53 Ma, and from the coastal belt between 83 +/- 8 Ma and 39 +/- 7 Ma. These data prompted a review and comparison with low-temperature thermochronological data from the whole Nubian Red Sea Margin, and a discussion on their implication in assessing the margin evolutionary style. AFT data are available for Egypt and Eritrea as well as apatite (U-Th)/He (AHe) ages for two transects transversal to the margin in Eritrea. Both in Egypt and Eritrea AFT data record a cooling event at about 20-25 Ma (Early Miocene) and an earlier, more local, cooling event in Egypt at about 34 Ma (Early Oligocene). The thermal modeling of the Sudan samples provides an indication of a rapid cooling in Miocene times, but does not support nor rules out an Early Oligocene cooling phase. The re-assessment of new and existing thermochronological data within the known geological framework of the Nubian and conjugate Arabian margins favours the hypothesis that early rifting stages were affecting the whole Gulf of Suez-Red Sea-Gulf of Aden system since the Oligocene. These precocious, more attenuated, phases were followed by major extension in Miocene times. As to the mode of margin evolution, AFT age patterns both in Egypt and Eritrea are incompatible with a downwarp model. The distribution of AHe ages across the Eritrean coastal plain Suggests that there the escarpment was evolving predominantly by plateau degradation.