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Sedimentological, paleobiological, mineralogical, and geochemical analyses of a sediment core retrieved on the seafront of Cartagena Bay were performed after high-resolution sampling. A wide series of dates obtained through radiocarbon and amino acid racemization proved that the Holocene record on the analyzed core began at ca. 7300 yr cal BP. Reinterpretation of the marine seismic profiles indicated that the beginning of this transgression was channeled along erosive paleochannels excavated on a coastal plain of, at least, MIS5c age. The Holocene paleoenvironmental evolution consisted of a first period marked by marine conditions with strong inputs from a fan delta linked to the reorganized fluvial network that occurred after the sudden rise of the base level, which caused a growing sedimentary prism. Later, the full marine environment was reflected in the development of a Posidonia - Cymodocea meadow hosting a rich biodiversity of marine species (mollusks, foraminifera, ostracoda). Around 3800 yr cal BP, the area underwent a profound change and a silting process started to alter the conditions, turning the area into a paucispecific brackish marsh environment in which mud deposition was dominant. Since Carthaginian times, arrangement works locally affected the record, allowing the arrival of some marine species due to port work (dredging) undertaken to gain depth and showing anthropic influence. [ABSTRACT FROM AUTHOR]

Here, we sought to reconstruct the Pleistocene and Holocene evolution of Cartagena Bay. Therefore, 16 borehole cores were analysed with the following aims: (1) to define a chronological framework; (2) to obtain data on the palaeoenvironment; and (3) to establish the relationship with human activities, especially focused on the reconstruction of the Carthago Nova (also known as Qart Hadasht) conquest. A total of 147 samples were recovered for amino acid racemisation (AAR) dating; 32 for radiocarbon dating (14C); and 159 for sedimentological, palaeontological, and biomarker determination. These approaches allowed us to elucidate the evolutionary phases of the palaeolandscape in Cartagena. The simultaneous use of AAR and 14C dating allowed the discrimination of spurious ages and the establishment of a chronological scale. During the Marine Isotope Stages (MIS) 7 and 5, the sea level (SL) in Cartagena Bay was almost the same as today. An alluvial plain developed in the northern area, and a delta was formed by an ephemeral river. In contrast, during MIS4, after a fall in SL, a wide sandy coastal plain emerged, leading to the accumulation of colluvial and aeolian deposits. The Holocene transgression was reflected in the hinterland in a late and temporarily floodable marsh fed by alluvial fans and creeks, producing a salinity gradient from freshwater to brackish and saline waters. Along the sea front, the marine influence was evident but not dominant, grading up and landwards to saline and freshwater marshes. Therefore, at the time of Scipio's conquest, the geography of Carthago Nova was quite different from that described by Polybius. The Roman's sudden attack seized Qart Hadasht from the south-west, avoiding the marshy area and not crossing a fast and deep ebb stream as it never existed on the Mediterranean Iberian coast. [ABSTRACT FROM AUTHOR]