Mode and timing of kurkar and hamra formation, central coastal plain, Israel

Abstract

ABSTRACT Porat, N., Wintle, A.G., Ritte, M. 2003. Mode and timing of kurkar and hamraformation, central coastal plain, Israel. Isr. J. Earth Sci. 53: 13–25. Kurkar ridges along the coastal plain of Israel are composed of alternating calcareousaeolianite (kurkar) and paleosol (hamra) units. Precise infrared-stimulated lumin-escence dating on alkali feldspars from both types of sediment confirms that all theunits comprising the most westerly kurkar ridge in the central coastal plain weredeposited during the last 65 ka. Calculated rates of accumulation for the kurkar give1–7 m/1000 years, with thick beds being deposited over periods as short as 2000–3000 years. On the other hand, accumulation rates for the hamra are at least one orderof magnitude lower, about 0.1 m/1000 years, implying long periods of relativeenvironmental stability. When these results are combined with measurements of thecarbonate content of each unit, it appears that high carbonate content alone is notsufficient for kurkar formation, but a high accumulation rate is essential. Thus thegoverning factor that controls the fate of a deposited aeolianite, whether it will cementinto kurkar or undergo pedogenesis, is the rate of accumulation.