Kirsty Elizabeth Helena Penkman's research while affiliated with New York University and other places

An amendment to this paper has been published and can be accessed via the original article.

While amino acid (AA) geochronology has been widely applied to foraminiferal biomineral proteins, there has been limited assessment of the potential of isolating an ‘intra-crystalline’ fraction of proteins to improve the reliability of AA geochronology for foraminifera. In this study, bleaching experiments were carried out on the foraminifer Neogloboquadrina pachyderma (sinistral) from an independently dated core from the south eastern Norwegian Sea spanning the last 120 ka. Results show that this species contains a bleach-resistant fraction of biomineral proteins, and that this intra-crystalline fraction may behave as a closed system. Racemisation in both the intra-crystalline and whole-protein fractions was found to systematically increase with time. Isoleucine epimerisation showed reliable trends with depth when analysed by ion exchange chromatography (IEC); analysis by reverse-phase liquid chromatography (RP-HPLC) resulted in reliable age-D/L relationships for aspartic acid, glutamic acid and alanine. Isolating the intra-crystalline fraction with a 48 h bleach treatment reduced the influence of contamination in younger material. Therefore, this paper recommends that the intra-crystalline approach is used when analysing Neogloboquadrina pachyderma (sinistral) for AA geochronology, especially for younger samples. Material-specific regression equations developed in this study successfully convert IEC A/I to RP-HPLC D/L values for aspartic acid, glutamic acid and alanine, enabling integration of geochronologies developed using different methods for this class of biomineral.

At Sutton Cross, eastern England, an undated River Nene 2nd Terrace was known to record a complex sequence of late Middle to Upper Pleistocene deposits. Amino acid geochronology was carried out for samples from four separate facies associations in order to provide a chronostratigraphic framework for this complex deposit. Each sample comprised three specimens of Bithynia tentaculata opercula. The intracrystalline protein decomposition results confirmed the sedimentary stratigraphic interpretation previously proposed for the site, i.e., that fossiliferous sediments yielding fully temperate Mollusca and Ostracoda faunas are equivalent in age to marine isotope stage (MIS) 7. Palaeotemperature reconstructions based on the Ostracoda fauna (July: +14 to +26 °C; January: ―4 to +5/+3 °C) embrace those of today at this location (July: +17 °C; January +3 °C). The sedimentary succession at Sutton Cross comprises vertically aggraded packages with a probable maximum age of MIS 8 and minimum age of MIS 2. This aggradation pattern (and age range) is also common to downstream sedimentary successions at Whittlesey, and is counterintuitive to the traditional terrace stratigraphy approach that expects laterally aggrading downstepping packages. The preservation of sediments of MIS 7 age and older at Sutton Cross with no evidence of glacial overriding places constraints on recently proposed late Middle Pleistocene regional ice limits.

Sediments deposited in the Loch of Stenness (Orkney Islands, Scotland) during the Holocene transgression, previously dated to between ~5939–5612 bp, were analysed for molecular fossils – lipids and chlorophyll pigments from primary producers – that complement conventional microfossil and lithological approaches for studying past sea‐level change. While microfossil and lithological studies identified a transgression between 102 and 81 cm core depth, key molecular fossils fluctuate in occurrence and concentration between 118 and 85 cm, suggesting an earlier start to the transgression. Terrestrial lipid concentrations decreased and algal‐derived, short‐chain, n‐alkanoic acid concentrations increased at 118 cm, indicating a disruption of the freshwater lake conditions associated with the early stages of the marine transgression. The lipid and pigment analyses provided information that complements and extends that from microfossil analysis, presenting a more complete record of Holocene sea‐level changes and local vegetation changes in the Loch of Stenness. The isostatic stability of Stenness during the Holocene points towards other factors to explain the transgression, such as regional factors and/or melting of the Antarctic ice sheet (which occurred up to 3 ka).

In the North Sea basin the marine bivalve Macoma balthica first appears within the Early Pleistocene ‘Weybourne Crag’, which forms an important biostratigraphical datum. Here we review the fossil assemblages from sites of this age, prompted by new discoveries from Sidestrand, Norfolk, UK. The molluscan assemblages from this horizon are dominated by intertidal species with some colder/deeper water taxa and a few temperate non-marine species. A high boreal/low arctic marine environment with reduced salinities is indicated. An extensive assemblage of small mammals dominated by voles includes two species (Mimomys hordijki and Ungaromys dehmi) previously unknown from the British Pleistocene. The assemblage can be assigned to Tesakov’s Mammal Biozone MNR1 (=MN17, Middle Villafranchian), which according to current estimates corresponds to a date of ∼2.2-2.1 Ma (MIS 84-79). It matches another assemblage from -61 m to -65 m in the Zuurland-2 borehole in The Netherlands, and is similar to that from the Dutch Tiglian type site at Tegelen, although this has more temperate elements. A late Tiglian age is consistent with the co-occurrence of the marine bivalves Macoma balthica, Mya arenaria and the freshwater gastropod Viviparus glacialis in the Zuurland-2 borehole and in a North Sea borehole (BGS 52-02-472). A Macoma balthica – Mya arenaria Concurrent Range Zone is defined for this assemblage, which can be traced across the North Sea basin. Amino acid dating provides strong independent support for these correlations and indicates that the Baventian cold stage post-dates the Bramertonian (Norwich Crag). It also confirms that Early Pleistocene molluscan assemblages with M. balthica are younger than those without it. The correlation of this marine marker horizon with Mammal Biozone MNR1 provides a secure link between continental and marine sequences during the Early Pleistocene. It also provides a basis for dating events in the pre-glacial fluvial drainage history and linking it to the East European mammal zonation.

An aminostratigraphical study was undertaken to provide an independent test of the veracity of the East European Mammal zonation. This important biostratigraphical scheme was originally defined from reference sites in the Azov/Black Sea region of southern Russia, but is now widely used to correlate late Neogene and Quaternary sediments across much of Europe and western Asia. As well as yielding a series of mammal assemblages, these reference sites, which range in age from the late Pliocene (Piacenzian ca. 3.0 Ma) to Late Pleistocene (0.1 Ma), also contain calcitic opercula of two genera (Bithynia and Parafossarulus) of freshwater gastropod snails that are suitable for amino acid dating. The intra-crystalline protein decomposition (IcPD) of four amino acids (aspartic acid, alanine, valine, and glutamic acid) was analysed from the opercula of these two genera, which showed similar patterns of protein degradation, allowing both to be used for aminostratigraphy. The IcPD data are consistent with the relative ages inferred from the mammal biostratigraphy and also with stratigraphical hiatuses interpreted from the fossil record. The temporal resolution provided by IcPD data from opercula is amino acid dependent, and declines in samples older than ∼2 Ma. The high variability of IcPD between opercula samples at some sites suggests reworking. Anomalously high levels of IcPD in samples from the Early Pleistocene site of Tizdar may be due to geothermal heating from local mud volcanism. This study provides the first large-scale application of IcPD-based aminostratigraphy for the Quaternary of continental Europe, and highlights its importance in testing regional stratigraphic schemes for the Late Pliocene and the Pleistocene.

Understanding and quantifying preservation of organic archaeological materials has become increasingly important as wet or waterlogged sites are put at risk from human-driven alterations, such as land drainage, urbanisation, and climate change. Although a wide range of analytical methods can be applied to assess the state of preservation of an archaeological object, determining which of these is most appropriate can be challenging. Within the budgets and deadlines dictated by the project design, an assessment must provide useful information that aids site management and conservation decisions. This review aims to summarise the most commonly reported methods suitable for the analysis of archaeological wood, offering an overview of the information obtained by each. Methods are evaluated in terms of the information gained weighed up against their cost, logistical considerations and time investments. Recommendations are provided to aid with the design of preservation assessment schemes.

Mollusc biogenic carbonates are valuable records of past environmental conditions. In particular, carbonate oxygen (δ¹⁸O) and carbon (δ¹³C) stable isotopes can be used to reconstruct different physical and chemical parameters, according to the different genera used (marine, freshwater or terrestrial). The Last Interglacial (early Eemian) palaeolake of Neumark‐Nord 2 (NN 2), Germany provides an excellent example of a Neanderthal archaeological site with abundant freshwater carbonate remains. As in other European contexts, one of the most abundant species is Bithynia tentaculata . In order to provide a robust regional baseline for the interpretation of the archaeological data, this study includes a calibration phase on modern B. tentaculata opercula. The results indicate that these calcitic structures are likely to be subjected to a growth slowdown/cessation during summer, which influences their geochemistry, reflecting mainly the water properties of the rest of the year. This modern calibration, together with the existing palaeoenvironmental reconstructions developed for NN 2 (e.g. pollen data), represents a valuable opportunity to establish B. tentaculata opercula as reliable environmental proxies applicable to several other freshwater contexts. The isotope data of the NN 2 opercula, in agreement with the pollen record, indicate that the major archaeological horizon was formed during a rather wet period and potentially in a semi‐forested environment. However, human occupation occurred also during drier phases at the site and within a wide temperature range, indicating the absence of restricted environmental preferences by the local Neanderthal groups.

In the North Sea basin the marine bivalve Macoma balthica first appears within the Early Pleistocene ‘Weybourne Crag’, which forms an important biostratigraphical datum. Here we review the fossil assemblages from sites of this age, prompted by new discoveries from Sidestrand, Norfolk, UK. The molluscan assemblages from this horizon are dominated by intertidal species with some colder/deeper water taxa and a few temperate non-marine species. A high boreal/low arctic marine environment with reduced salinities is indicated. An extensive assemblage of small mammals dominated by voles includes two species (Mimomys hordijki and Ungaromys dehmi) previously unknown from the British Pleistocene. The assemblage can be assigned to Tesakov’s Mammal Biozone MNR1 (=MN17, Middle Villafranchian), which according to current estimates corresponds to a date of ∼2.2-2.1 Ma (MIS 84-79). It matches another assemblage from -61 m to -65 m in the Zuurland-2 borehole in The Netherlands, and is similar to that from the Dutch Tiglian type site at Tegelen, although this has more temperate elements. A late Tiglian age is consistent with the co-occurrence of the marine bivalves Macoma balthica, Mya arenaria and the freshwater gastropod Viviparus glacialis in the Zuurland-2 borehole and in a North Sea borehole (BGS 52-02-472). A Macoma balthica – Mya arenaria Concurrent Range Zone is defined for this assemblage, which can be traced across the North Sea basin. Amino acid dating provides strong independent support for these correlations and indicates that the Baventian cold stage post-dates the Bramertonian (Norwich Crag). It also confirms that Early Pleistocene molluscan assemblages with M. balthica are younger than those without it. The correlation of this marine marker horizon with Mammal Biozone MNR1 provides a secure link between continental and marine sequences during the Early Pleistocene. It also provides a basis for dating events in the pre-glacial fluvial drainage history and linking it to the East European mammal zonation.