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This study was conducted in the Middle Branch of Bue Marino Cave (Sardinia, Italy) to reconstruct paleoecological conditions during the Holocene through microfaunal proxies in seven surface sediment samples and a short sediment core (BMD-2018, 18 cm), all collected in 2018 and another core sampled in 2021 (BMD-2021, 28 cm). The first attempt at dating cave sediment through luminescence was conducted on BMD-2021; the derived age was 6.04 ± 0.47 ka at 18 cm depth. Although continuous sedimentation and constant rates are not probable in the cave, this indicates that the sedimentary record dates to the early times after the Holocene flooding of the cave by the sea. Benthic foraminifera and grain size were analyzed in all surface samples and core BMD-2018, while only benthic foraminifera were studied in BMD-2021. The recent foraminiferal assemblages, studied from an ecological point of view, were applied as modern analog to reconstruct the paleoecological conditions in sediment cores. Significant changes in the sedimentary environment were excluded; the two cores showed a similar foraminiferal turnover at a similar depth, from an older assemblage with prevailing indifferent Ammonia inflata to a younger one with prevailing opportunist Eggerelloides advena. This turnover was attributed to changes in the amount and/or quality of available nutrients. Based on these results, this event is likely related to possibly attributable to the effects of climate changes that occurred in the Holocene. However, more extensive studies are necessary to better understand the effects of the climatic/environmental events in the Late-Holocene in the caves. Although it represents a first attempt at paleoenvironmental reconstruction based on sediments from a Mediterranean marine cave, this study demonstrated that benthic foraminifera are refined paleoenvironmental proxies and that the integrated approach with the luminescence dating produces reliable results for studying the effects of global changes in these environments. [ABSTRACT FROM AUTHOR]

The relict beach deposit of the Cala Mosca marine terrace is considered an important section of Marine Isotopic Stage (MIS) 5e (ca. 125 ka) sea-level highstands. Analysis of the stratigraphy and sediments of the deposit indicates the presence of a composite marine terrace comprising two superimposed marine units, luminescence dated to the MIS 5e (137 ± 7, 134 ± 7 ka) and MIS 5c (92 ± 6 ka) substages. The stratigraphic superimposition of the two highstands, both placed ∼5 m above present sea level, agrees with other areas along the Sardinia coasts. The evident superimposition of two sea-level highstands and development of the composite terrace cannot be accounted solely by high-frequency sea-level oscillation that occurred within MIS 5 for the Mediterranean Sea. This suggests controversial, but significant, regional versus local tectonic activity occurred during the Late Pleistocene. [ABSTRACT FROM AUTHOR]

Loess--palaeosol sequences formed by dust accumulation often provide an excellent record for understanding climate change and the deposition of atmospheric mineral dust. Holocene age loess deposits in the Arctic have to date received little attention, yet potentially can be used for past dust and climate reconstruction in this highly sensitive region. However, one of the prerequisites for utilizing the potential of these deposits is accurate, detailed, and independent chronologies. Here we sample loess and peat-loess sections for combined detailed luminescence and bulk organic radiocarbon dating, as well as testing possible climate proxies around the ice-free area of western Greenland near Kangerlussuaq. While the OSL quartz signal from loess in western Greenland was insensitive or weak, the low-temperature pIRIR180 and IR50 signals yielded reproducible ages. However, although luminescence ages show stratigraphic age consistency with depth, a large age offset of c. 2 thousand years is observed between luminescence ages and bulk organic matter radiocarbon ages, with the latter giving younger ages. This may result from incomplete bleaching of the IR and pIR signals, or from younger carbon contamination of bulk organic matter in the loess, which is generally low (<1%). Here we present further results of tests for the causes of these offsets between different age-dating techniques. It is well known that pIRIR ages are susceptible to overestimates due to 'partial bleaching', where solar exposure is insufficient to completely zero the signal, but rarely has this phenomenon been reported for airborne dust deposits. High-resolution sampling of loess deposits (each 2 cm) from the present field surface to 20 cm depth was performed, and analysis of variation of luminescence dose with depth reveals a consistent natural residual dose of ~ 5 Gy for pIRIR180 and 0.70 Gy for IR50. This yields an age of ~2.28 ka and 0.79 ka respectively, for surface deposits, which we suggest is a result of incomplete bleaching. Assuming that a similar residual dose occurs throughout the section, the ages were corrected and showed better agreement with bulk radiocarbon results. Final corrected ages reveal that most of loess accumulation occurred in Greenland during the Holocene over the last 4-6 ka. However, the possibility that the radiocarbon ages are too young remains and is also being investigated. Should the natural modern equivalent dose in these sediments be due to partial bleaching, this may be a consequence of dust accumulation occurring during the polar night season, combined with short transport distances (10s to 100s of m) and rapid burial at the surface. [ABSTRACT FROM AUTHOR]

Since the late '40 radiocarbon and U/Th methods have been widely used to provide precise ages of Pleistocene/Holocene, continental to marine, sedimentary successions worldwide. The major stratigraph- ic assumption is that the time elapsed since the death of organisms such as corals, shells, plants and (in some cases) bones found in sedimentary bodies correspond to the age of the strata depositions. The lu- minescence method, instead, provides the age since quartz and/or feldpsar grains were hidden by the sunligth and buried in a sedimentary strata. Thus, this method should directly calculate the age of a de- positional events. Despite their enourmous influences on stratigraphy both abiotic and biotic methods aren't silver bullets and when combined for dating marine or continental successions, results are not so straight forward building up, frequently different geochronological frameworks. We present two case studies where luminescence and biotic methos (radiocarbon and/or U/Th) have been applied on Late Quaternary marine and continental successions producing "apparent"geological mismatchings. The first case study is represented by the Marine Isotopic Stage (MIS) 5e (ca. 125 ka)relict beach deposits of Sardinia island (MediterraneanSea) . The succession filling marine terraces, is characterized by two superimposed units with abbundant corals toward the top. Traditional U/Th dating have been performed on corals for more than 30 years dating all the successions to the MIS5e (ca. 125 ka). Newly performed luminescence analysis instead, dated the lower unit to the MIS 5e (ca. 130ka) and the upper unit containing the U/T dated coral fragments to the following MIS 5c (ca. 100 ka) substage. Despite the methods provide a different chornological framework both are accurate and relailable. Thus the resultant interpretation is that the luminescence method is dating the age of the strata deposition (MIS5c) whereas U/Th provide the age of the death of corals (MIS5e) that were reduced in fragments and reworked from the underlain unit toward the top. The second case study is represented by the distal alluvial fan deposits developed along the flank of the Famara cliff (Lanzarote island, CanaryArchipelago). The succession from the bottom up is domina- ted by a ritmitic alternation of sand-sheet and muddy pond-like strata cut at the top by a relatively thick- gravelly channel body. The succession is luminescence dated at the MIS3 (40-25 ka) wherease radiocar- bon on shell-snails found in the muddy strata point to the early-middle Holocene (10-4 ka). The resultant chornological framework clearly appear as a geological nonsense and the age reversal cannot be explai- ned considering a post-death reworking of the snails. Despite these both methods are accurate and the ages fully relailable. The site evolution is thought to be the following; during the MIS3 several high frequency climatic oscillations allow the deposition of the sandy-muddy succession and at the beginning of the last glaciation (MIS2) a strong fluvial incision occurred leaveing the succession partially exposed. Finally, terrestrial gastropods during the extremely dry phases occurred along the early-middle Holocene (possibly cold Bond events) borrowed into the muddy strata trying to find a humid nest and there died. [ABSTRACT FROM AUTHOR]