Search

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 reconstructed the evolution of the Mazarrón Basin during the Pleistocene and Holocene. In this regard, we studied 9 cores with the aim to: 1) define a chronological framework; 2) obtain data on the palaeoenvironment; and 3) establish the relationship with recent tectonics. A total of 158 samples were recovered for amino acid racemization (AAR) dating, 4 for radiocarbon dating (14C), and 332 for sedimentological and palaeontological determination, and 110 for determination of the mineralogical content. These approaches allowed us to elucidate the evolutionary phases of the palaeo-landscape of the Mazarrón Basin, a fault-controlled graben affected by diverse faults, mainly those of Las Moreras and Rella. The ages of the records and the facies correlation indicate that Las Moreras Fault controlled sedimentation during Marine Isotope Stage (MIS) 7, whereas the Rella Fault was strongly active during the Middle Holocene. During MIS7, a brackish lagoon developed in the western area, overlying alluvial fan deposits. Later, the area was uplifted, thereby becoming exposed to erosion. The activity of the Rella Fault allowed sedimentation in the western part of the Mazarrón Basin during the Middle Holocene, while in the Upper Holocene sedimentation occurred in the eastern part. The Holocene transgression was reflected in a temporarily floodable marsh in the hinterland, with changing salinity conditions, from brackish to euhaline waters. Along the sea front, the marine influence was evident but not dominant. Thus, the Mazarrón Basin during the Holocene was brackish to highly euhaline, with variable biological diversity linked to a narrow and probably discontinuous communication with the sea, with restricted circulation and long flushing times, which was reflected by the significant presence of halite. The record ended with recent alluvial/anthropic sediments. [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]

In this paper, we conduct a palynological analysis of a high-resolution Holocene record from Cartagena Bay, southeast of the Iberian Peninsula, to establish paleoenvironmental variability of coastal areas in the western Mediterranean region at a centennial-scale over the last 7300 years. Statistical analysis of four palynozones allows reconstruction of paleotemperature and paleohumidity conditions. Pinus , steppic, xerophilous, and Mediterranean taxa persisted continuously through the record, and only during periods of increased humidity did deciduous and Mediterranean taxa expand (Zones II, subzone IIIb). Cooler and dry conditions favored the development of Cupressaceae and scrubs between 7300 and 7000 yr cal BP. The mid-Holocene (Northgrippian) mesophytic optimum took place between 6800 and 4000 yr cal BP during which time a Mediterranean climate was present and open forest developed, predominantly consisting of Mediterranean taxa and deciduous trees. The gradual rise in aridity in the Meghalayan (4000–1700 yr cal BP) led to Mediterranean forest being replaced by steppic and xerophilous vegetation, a change related mostly to a decrease in summer insolation, with superimposed centennial-scale variability in humidity. In parallel with forest degradation caused by increasing aridity, the record shows marked evidence of human influence since 4000 yr cal BP, which accelerated the progression of open landscapes from the Chalcolithic onwards, this change being especially marked during the Roman period. Significant denudation of the landscape can be attributed to the use of fire, as well as due to agriculture and grazing, with a major contributor being intense metallurgical and mining activity in the area. The Cartagena Bay record reported herein shows centennial-scale oscillations in humidity and temperature that correlate with well-known climatic events during the late Holocene in the western Mediterranean region, synchronous with variability in solar and atmospheric dynamics. The alternation of persistent North Atlantic Oscillation modes is likely to have played a key role in regulating humid–arid periods. • Pollen content allowed the paleoenvironmental reconstruction during the Holocene. • Centennial-scale oscillations in humidity & temperature correlate with climatic events. • The mid-Holocene mesophytic optimum took place between 6800 and 4000 yr cal BP. • Aridity and xerophytization occurred between 4000 and 1700 yr cal BP. • Human influence accelerated the progression of open landscapes since the Chalcolithic. [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]