Environmental change in the ría de vigo, NW iberia, since the mid-Holocene: New palaeoecological and seismic evidence

摘要

Pollen analyses (pollen, dinocysts and others) were combined with high-resolution seismic-stratigraphy sequences to reconstruct environmental dynamics and regional sea-level (RSL) changes in a ria in NW Iberia. The chronological framework was established using radiocarbon dating and pollen markers that are related to a number of historical events. Major intensifications of the regional upwelling regime occurred during predominant NAO positive stages, dated to c. 4600-4300, 3800-3600, 3200-2700 and 2600-2400cal. a BP. The regional Early Highstand System Tract spans from before 4500 to c. 3200cal. a BP. During this period RSL was still rising, but several short episodes of higher terrestrial influence were detected between c. 4300-3800 and 3600-3200cal. a BP. A readjustment occurred between 3200 and 2300cal. a BP, including the first stage of relative sea-level drop (2.8 ka event) dated to 3200-2800cal. a BP, with the RSL recovering between 2800 and 2300cal. a BP. The subsequent Later Highstand System Tract, after 2300cal. a BP, corresponds to a final period of rising sea level that caused the final inundation of San Simón Bay. Since then, only minor changes in relative sea level can be postulated (e.g. towards the end of the Roman Period, in the Middle Ages and during the Little Ice Age). This new evidence is consistent with most of the available palaeoecological and historical information, but it provides a more detailed, near-complete succession of simultaneous changes occurring in both the terrestrial and the marine ecosystems.