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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]

We reconstructed the palaeoenvironmental conditions of Cartagena Bay during the Holocene after a multidisciplinary study to identify natural variations and the anthropic processes of this coastal area. A total of 119 samples were recovered for amino acid racemization dating, 3 for radiocarbon dating (14C), and four sets of 80 samples for sedimentological and palaeontological determination, mineralogical content, biomarker and trace elements quantification. Two natural scenarios were identified from the variations of n -alkane indices and palaeobiological content. The first period (6650–5750 yr cal BP) was marked by the development of euhaline marine conditions with strong inputs from aquatic macrophytes and high biodiversity. After a hiatus, the area underwent a profound change, becoming a paucispecific brackish marsh environment with increasing inputs from land plants, with possible episodes of emersion with a greater presence from terrestrial gastropods (3600–300 cal yr BP). By combining trace element abundance and stanol distributions, our study also provides a novel approach to identify the predominant influence of anthropogenic factors in the last three millennia in the coastal record of Cartagena Bay. Findings confirmed that Pb mining and metallurgy began during the Bronze Age, with considerable inputs of this heavy metal into the atmosphere during Phoenician, Punic and particularly Roman times compared to the Middle Ages. Pollution by Cu and Zn was also observed during Punic and Roman times, and was first documented in the Middle Ages. In addition, faecal stanols, such as coprostanol, derived mainly from humans, and 24-ethylcoprostanol from herbivores were present, thereby indicating for the first time a continuous presence of human populations and significant pollution input since 3600 yr cal BP, this being greater in the late Bronze Age and Phoenician, Punic and Roman times than during Late Antiquity and the Middle Ages, when the city was in decline. [Display omitted] • Euhaline marine conditions and high biodiversity occurred at 6650–5750 yr. • A paucispecific brackish marsh environment occurred at 3400–300 yr after an hiatus. • Faecal sterols revealed pollution from herbivores and humans since Bronze Age. • Pb–Zn–Cu linked to regional mining-metallurgy since Bronze Age to Middle Ages. [ABSTRACT FROM AUTHOR]

• Based on alkane indices, three geochemical units (GU) were identified. • GUs represent major contribution of aquatic macrophytes or terrestrial plants. • Paleoenvironmental episodes (PE) produced oscillations in the marsh water level. • PEs were related to sea level and climatic changes, and recent tectonics. • Emersion led to increased amounts of short-chain and branched fatty acids. We reconstructed the paleoenvironmental conditions of the Mazarrón Basin during MIS 7 and MIS 1 based on their alkane and fatty acid contents, their mineralogy and the fossil content of an amino-acid-dated sediment sequence. The n- alkane and fatty acid indices proved to be excellent paleoenvironmental proxies for studying the paleo-hydrogeological and paleoclimatological evolution of this marshland. Three geochemical units (GUs) were identified from the abundance of the C 25 n -alkane and the ACL, TAR HC and P aq values, confirming the importance of phases with terrestrial plant input or aquatic macrophyte predominance. These GUs were used to define three paleoenvironmental episodes (PEs) during MIS 7. In PE7.1, the contribution of algal and aquatic macrophytes predominated in a temporarily flooded saline muddy plain. In PE7.2, the major contribution was from aquatic macrophytes (flooded marsh), although it was marked by episodes of emersion with greater terrestrial contribution. At the top of the MIS 7 record (PE7.3), there was a significant reduction in the water depth, with the main input deriving from terrestrial plants in a muddy alluvial plain. Six PEs were established during MIS 1 (Holocene), of which three predominately received organic matter derived from aquatic macrophytes, while the major contribution in the other three came from terrestrial plants. The two sets of PEs were linked to episodes of increased and decreased water level, respectively. This interpretation is consistent with the characteristics of the sediment facies, with PE1.1, 1.3 and 1.5 corresponding to a marsh with deeper water and a greater input of detrital materials, and PE1.2, 1.4 and 1.6 to a shallow environment with carbonates and gypsum deposits. Direct marine influence was limited, so the oscillations in the water level in the marsh were likely to be more related to climatic changes (drier/wetter phases) and recent tectonics than to large changes in sea level. Emersion led to degradation of the organic matter and enrichment in short-chain and branched saturated fatty acids. [ABSTRACT FROM AUTHOR]