Holocene hydroclimatic variability profoundly influenced the Sistan Basin (southeastern Iran), a hyperarid region underexplored in paleoclimate research. Understanding these dynamics is critical for interpreting environmental controls on human settlement and ecosystem change, particularly the poorly understood interplay between the Indian Ocean Summer Monsoon (IOSM) and Mediterranean winter rainfall. This study presents a multiproxy reconstruction of paleoenvironmental changes in the Sistan Basin, Iran, over the past 5000 years, using AMS 14C dating, sedimentological, geochemical, and biological analyses of a 3-m trench from the Hamoun-e Puzak wetland. Five distinct facies (A-E), reveal major hydroclimatic shifts driven by orbital forcing, IOSM dynamics and Mediterranean precipitation. A pronounced arid phase (∼5000–3850 cal yr BP), coincided with the 4.2 kyr BP megadrought and the decline of early Bronze Age settlements. This was followed by a sustained humid period (3850–2700 cal yr BP) characterized by expanded lake levels, enhanced fluvial input, and higher biological productivity, facilitated by intensified Mediterranean rainfall. Subsequent facies document increasing climate variability and aridity, culminating in extreme dryness in recent centuries. Findings show strong synchronicity with regional paleoclimate records, particularly Persian Gulf Sea surface temperatures (SSTs), an indicator of top-of-atmosphere solar radiation. This research underscores the Sistan Basin\\\\\\\'s extreme climatic volatility and provides crucial long-term insights into climate change and ancient civilizations dynamics in this hyperarid region.

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