This study documents the evolution of the coastal site on which an ancient port fortress, Pelusium, was positioned in the NE corner of Egypt's Nile Delta. Focus is on the stratigraphy, petrology, and faunal assemblages of radiocarbon-dated core sections recovered at major ruins at the site. The late Holocene development of this margin surface is unusual in that it has been subject to important geologically recent uplift since the city's founding, in contrast to predominant subsidence and relative sea-level rise that characterize most of the delta margin west of Pelusium. Vertical tectonics resulted from displacement along the Pelusiac Line, a major structural feature several kilometers south of Pelusium. The geoarchaeological survey shows the was built with ready access to the Mediterranean, after tectonic uplift, from ∼1000 to 800 BC. It was then, when Egypt was subject to Assyrian control, that the margin evolved from an open shallow marine (prodelta, delta-front) setting to a coastal one.
The city's progressive decline was influenced by warfare with Persians and other invaders from the east, effects of plague, and diminished role of its commercial and trade activities following construction of Alexandria by the Greeks. However, Pelusium's eventual demise also resulted from natural factors, especially tectonically controlled motion of the lower delta plain. Vertical shifts around 800–850 AD and subsequent periods resulted in rapid coastal build-out north of Pelusium. This caused a cutoff of the city from the sea and the Nile's Pelusiac branch, the major navigational byway into the delta.
Pelusium, after approximately 800–850 AD, continued as a commercial center for an additional three to four centuries prior to its abandonment by the time of the Crusades. Submergence of the city on the delta margin by rise of relative sea level has been effectively counteracted by episodic fault-related uplift of this lower plain sector and continued subaerial exposure since Byzantine time.