A standardized database of Last Interglacial (MIS 5e) sea-level indicators in Southeast Asia

Marine Isotope Stage 5e (MIS 5e; the Last Interglacial, 125 ka) represents a process analog for a warmer world. Analysis of sea-level proxies formed in this period helps in constraining both regional and global drivers of sea-level change. In Southeast Asia, several studies have reported elevation and age information on MIS 5e sea-level proxies, such as fossil coral reef terraces or tidal notches, but a standardized database of such data was hitherto missing. In this paper, we produced such a sea-level database using the framework of the World Atlas of Last Interglacial Shorelines (WALIS; https://warmcoasts.eu/world-atlas.html). Overall, we screened and reviewed 14 studies on Last Interglacial sea-level indicators in Southeast Asia, from which we report 43 proxies (42 coral reef terraces and 1 tidal notch) that were correlated to 134 dated samples. Five data points date to MIS 5a (80 ka), six data points are MIS 5c (100 ka), and the rest are dated to MIS 5e. The database compiled in this study is available at https://doi.org/10.5281/zenodo.5040784 (Maxwell et al., 2021).

A standardized database of Last interglacial (MIS 5e) sea-level indicators in Southeast Asia

Marine Isotope Stage 5e (the Last Interglacial, LIG) represents a process analogue for a warmer world expected for the near future. Analysis of LIG relative sea level (RSL) proxies helps in constraining both regional and global drivers of sea-level change. In Southeast Asia, several studies have reported elevation and age information on LIG RSL proxies, such as fossil coral reef terraces or tidal notches, but a standardized database of such data was hitherto missing. In this paper, we produced such sea-level database using the framework of the World Atlas of Last Interglacial Shorelines (WALIS, https://warmcoasts.eu/world-atlas.html). Overall, we screened and reviewed 14 studies on LIG sea-level indicators in Southeast Asia, from which we report 43 unique RSL proxies (42 coral reef terraces and one tidal notch), that were correlated to 134 dated samples. The database compiled in this study (Maxwell et al., 2021) is available at https://doi.org/10.5281/zenodo.4681325.

Oral legend and geological evidence for a 16th century giant tsunami in Kiribati, central Pacific

<p>Within Oceania, the vast Central and Western Pacific (CEWEP) is an intriguing anomaly because of the scarcity of historical tsunami observations and the complete absence of dated palaeotsunami events.  This study establishes the first dated high-magnitude palaeotsunami event within the CEWEP region.  Both geological data and oral legend are presented for a palaeotsunami that struck remote Makin atoll in northernmost Kiribati towards the end of the 16<sup>th</sup> century.  Narration of the euhemeristic myth by the <em>Wiin te Maneaba</em>, traditional storyteller on Makin, offered important details supporting a tsunami hypothesis.  The legend preserves credible information surrounding the giant-wave origin of <em>Rebua </em>and <em>Tokia</em>, two prominent named subaerial reefblocks of megaclast size that were produced and transported shorewards away from the reef edge by the event.  The youngest U-Th age-dates for fossil coral samples in the reefblocks give a maximum age for the palaeotsunami of <em>circa </em>AD 1576.  Several far-field Pacific Rim and regional possibilities exist for tsunamigenesis.  These include subduction-zone seismicity and catastrophic volcanic eruption, both of which have been linked to late 15<sup>th</sup> century palaeotsunamis recorded elsewhere in the Pacific Islands.  Available evidence, however, suggests that the ~AD 1576 Makin event was more likely locally generated by tsunamigenic submarine slope failure associated with the giant arcuate bight structure that characterises the northern atoll rim.</p>

A Global Compilation of U-series Dated Fossil Coral Sea-level Indicators for the Last Interglacial Period (MIS 5e)

This dataset is a comprehensive, global compilation of published uranium series (U-series) dated fossil coral records from ~150–110 thousand years ago, as well as associated elevation measurements and sample metadata. In total, 1312 U-series measurements from 994 unique coral colonies are included in the current version of the dataset, all of which have been normalized and recalculated using the same decay constant values. Two example geochemical screening criteria have been included to assist users with identifying altered fossil corals that display geochemical open-system behaviour, and the originally published interpretations on age quality have been preserved within the sample metadata. Additionally, a clear distinction has been made between coral colonies that are in primary growth position, which may be used for relative sea-level reconstructions and colonies that have been transported/reworked, which cannot be used for these purposes. Future research efforts involving fossil coral sea-level reconstructions should emphasize an integrated and holistic approach that combines careful assessment of U-series age quality with high-precision surveying techniques and detailed facies/stratigraphic observations. This database is available at http://doi.org/10.5281/zenodo.4309796 (Chutcharavan and Dutton 2020).

First sequencing of ancient coral skeletal proteins

Here we report the first recovery, sequencing, and identification of fossil biomineral proteins from a Pleistocene fossil invertebrate, the stony coral Orbicella annularis. This fossil retains total hydrolysable amino acids of a roughly similar composition to extracts from modern O. annularis skeletons, with the amino acid data rich in Asx (Asp + Asn) and Glx (Glu + Gln) typical of invertebrate skeletal proteins. It also retains several proteins, including a highly acidic protein, also known from modern coral skeletal proteomes that we sequenced by LC–MS/MS over multiple trials in the best-preserved fossil coral specimen. A combination of degradation or amino acid racemization inhibition of trypsin digestion appears to limit greater recovery. Nevertheless, our workflow determines optimal samples for effective sequencing of fossil coral proteins, allowing comparison of modern and fossil invertebrate protein sequences, and will likely lead to further improvements of the methods. Sequencing of endogenous organic molecules in fossil invertebrate biominerals provides an ancient record of composition, potentially clarifying evolutionary changes and biotic responses to paleoenvironments.

Coral reconstructed Mid-Holocene seasonality in the southwestern Caribbean

<p>Seasonality is a dominant factor in the Earth’s climate system, but proxy reconstructions on this time scale are sparse. Corals provide an excellent archive to reconstruct environmental conditions on seasonal time scale using geochemical proxies. Here, we use subfossil (~6.2-7.1 ka BP) <em>Siderastrea siderea</em> and <em>Pseudodiploria labyrinthiformis</em> corals from a pristine Mid-Holocene reef, located in Panamá, southwestern Caribbean. Mid-Holocene insolation seasonality in the Northern Hemisphere was stronger than at present. We investigate the resulting changes in SST and hydrological seasonality using coral Sr/Ca, δ<sup>18</sup>O and δ<sup>13</sup>C. To evaluate, if the coral heads can be utilised for geochemical analyses, they have been screened for diagenetic alteration (2D-XRD, thin section analysis). Obtained modern coral Sr/Ca-SST based annual cycle corresponds well with <em>in situ</em> measured SST. Fossil coral Sr/Ca-SST based cycles exceed the modern one by up to 50%. Fossil coral δ<sup>18</sup>O seasonal amplitudes are higher than the modern one by up to 30% and show a reduction in the mean gradient between wet and dry period, attributable to the northward shift of the Intertropical Convergence Zone. Increased SST and δ<sup>18</sup>O seasonality are consistent with model simulated SSTs (Kiel Climate Model) and model-based calculated pseudocoral δ<sup>18</sup>O, but the model underestimates the seasonality increase in the Mid-Holocene.</p>

Oman corals suggest that a stronger winter shamal season caused the Akkadian Empire (Mesopotamia) collapse

The Akkadian Empire was the first united empire in Mesopotamia and was established at 4.6 kyr B.P. (where present is A.D. 1950). The empire abruptly collapsed in 4.2 ± 0.2 kyr B.P. Seasonal-scale climatic dynamics behind this collapse have not yet been resolved. Here, we present monthly climatic parameters (temperature and hydrology) inferred from fossil Omani corals that lived between 4.5 and 2.9 kyr B.P. Winter temperatures derived from a modern Omani coral correlate with winter shamal (western Asian dust storm) frequency. A fossil coral from 4.1 kyr B.P. shows a prolonged winter shamal season with frequent shamal days. This likely caused agricultural failures in Mesopotamia and contributed to the Akkadian Empire collapse, as this region depends on winter rainfall.