Molluscs of the Genus Glycymeris from Vogelherd Cave near Niederstotzingen (Lonetal, Southwestern Germany)

The site of Vogelherd in the Lone Valley of southwestern Germany has become world famous for its many unique artworks made from mammoth ivory, personal ornaments, flute fragments, lithic artifacts, and antler and bone artifacts. In the study below, the molluscs from Vogelherd are presented, offering us new insights on the mobility and social behavior of Aurignacian groups in the Lone Valley. Some of the mollusc finds come from the 1931 excavation of Gustav Riek; however, most of them were uncovered during the later re-excavations of the site between 2005 and 2012. In order to provide context for these finds, we compare the molluscs from Vogelherd with those from across Central Europe. The identifiable fragments from Vogelherd belong to the genus Glycymeris. The Glycymeris molluscs originated from the Mainz Basin. This determination makes it possible to reconstruct one of the farthest long-distance connections known for the Upper Paleolithic in Germany. In addition to the Glycymeris finds, we present a tool that was also made from a mollusc. This mollusc-tool, coming from the excavation of 1931 and attributed to the Aurignacian, is a unique find for this time period of southern Germany. With this piece, along with microscopic examinations and discussions of the Glycymeris molluscs, we present a wide range of possible uses for these finds. For example, we discuss the possible use of the molluscs as ochre containers. To test this, we used EDX-analysis and a raster electron microscope. We compare the Glycymeris molluscs of Vogelherd with those from Gravettian and Magdalenian contexts at Hohle Fels, Geißenklösterle, Petersfels, and Gnirshöhle, and we provide a list of all sites from Germany, Switzerland, Eastern France, and Belgium with Glycymeris finds. We use size comparisons to show differences as well among the Glycymeris finds of Vogelherd and other Upper Paleolithic sites in southwestern Germany. In conclusion, we demonstrate that the Glycymeris molluscs of Vogelherd best fit into the Aurignacian, and we provide other Aurignacian sites that contained similar finds. By discussing other long-distance connections in the Aurignacian of southern Germany, it becomes evident that Glycymeris molluscs are not specific only to the Swabian Aurignacian.

Lithological dependence of aragonite preservation in monospecific gastropod deposits of the Miocene Mainz Basin: Implications for the (dia-)genesis of limestone–marl alternations

ABSTRACT The origin of limestone–marl alternations (LMA) and their diagenesis is still lively debated. The most disputed question is whether original variations in sediment input control the differentiation of the precursor sediment into limestone and marl, or if a LMA can form without compositional differences in the precursor sediment. The Miocene brackish-water deposits (Rüssingen Formation) from the Mainz–Weisenau quarry in central Germany offer the opportunity to tackle this question. They are developed as a monospecific alternation of planar beds of moderately and poorly lithified sands of aragonitic Hydrobia snails, corresponding to “limestones” and “marls” in LMA, respectively. XRD analyses and the monospecific composition reveal only minor to no changes in sedimentary input and allow comparison of the preservation of Hydrobia in both lithologies. The differential preservation of the aragonitic fossils in lithified and less lithified layers is documented in thin-sections. CaCO3 contents are high throughout the measured section. However, XRD analyses revealed high amounts of aragonite and low amounts of calcite in less lithified beds, and the opposite in lithified beds in which calcite is the main mineral phase. Mg-calcite is abundant in both lithologies. Although the less lithified beds have experienced significant loss of aragonite by dissolution, they still mainly contain aragonite since the precursor sediment contained only aragonitic shells and Mg-calcite crusts. The relative amount of aragonite is higher than in the more lithified beds because the lithified beds imported the dissolved aragonite, which precipitated as calcite cements. This shifted the aragonite–calcite ratio to higher values in the less lithified beds than in the more lithified beds, although it is counterintuitive at first sight. This is supported by thin-section analyses and point counting, revealing moderate to good preservation of Hydrobia or their replacement by calcite spar in lithified beds, but intense dissolution of aragonite in less lithified beds. The aragonite–calcite ratio and the differential preservation of Hydrobia fit the model of differential diagenesis in “classical” LMAs, which assumes early diagenetic aragonite dissolution in marls and reprecipitation as calcite cement in limestones. It is concluded that the studied succession—although an endmember of LMA—was differentiated into lithified and unlithified beds by incomplete differential diagenesis while minor primary differences are not reflected in the change in lithology. The results suggest that the differentiation of a homogeneous precursor sediment into a LMA is possible and caution should be exercised using lithological change or proxies which are potentially altered by CaCO3 redistribution for cyclostratigraphic analyses.

The bivalve <i>Glycymeris planicostalis</i> as a high-resolution paleoclimate archive for the Rupelian (Early Oligocene) of central Europe

Current global warming is likely to result in a unipolar glaciated world with unpredictable repercussions on atmospheric and oceanic circulation patterns. These changes are expected to affect seasonal extremes and the year-to-year variability of seasonality. To better constrain the mode and tempo of the anticipated changes, climatologists require ultra-high-resolution proxy data of time intervals in the past, e.g., the Oligocene, during which boundary conditions were similar to those predicted for the near future. In the present paper, we assess whether such information can be obtained from shells of the long-lived bivalve mollusk Glycymeris planicostalis from the late Rupelian of the Mainz Basin, Germany. Our results indicate that the studied shells are pristinely preserved and provide an excellent archive for reconstructing changes of sea surface temperature on seasonal to interannual timescales. Shells of G. planicostalis grew uninterruptedly during winter and summer and therefore recorded the full seasonal temperature amplitude that prevailed in the Mainz Basin ~ 30 Ma. Absolute sea surface temperature data were reconstructed from δ18Oshell values assuming a δ18Owater signature that was extrapolated from coeval sirenian tooth enamel. Reconstructed values range between 12.3 and 22.0 °C and agree well with previous estimates based on planktonic foraminifera and shark teeth. However, temperatures during seasonal extremes vary greatly on interannual timescales. Mathematically re-sampled (i.e., corrected for uneven number of samples per annual increment) winter and summer temperatures averaged over 40 annual increments of three specimens equal 13.6 ± 0.8 and 17.3 ± 1.2 °C, respectively. Such high-resolution paleoclimate information can be highly relevant for numerical climate studies aiming to predict possible future climates in a unipolar glaciated or, ultimately, polar-ice-free world.

The bivalve <i>Glycymeris planicostalis</i> as a high-resolution paleoclimate archive for Rupelian (Early Oligocene) of Central Europe

Current global warming is likely to result in a unipolar glaciated world with unpredictable repercussions on atmospheric and oceanic circulation patterns. These changes are expected to affect seasonality as well as the frequency and intensity of decadal climate oscillations. To better constrain the mode and tempo of the anticipated changes, climatologists require high-resolution proxy data of time intervals in the past, e.g. the Early Oligocene during which boundary conditions were similar to those predicted for the near future. As demonstrated by the present study, pristinely preserved shells of the long-lived bivalve mollusk Glycymeris planicostalis from the late Rupelian of the Mainz Basin, Germany, provide an excellent archive to reconstruct changes of sea surface temperature on seasonal to inter-annual time scales. Their shells grew uninterruptedly during winter and summer and therefore recorded the full seasonal temperature amplitude that prevailed in the Mainz Basin 30 Ma ago. Absolute sea surface temperature data were faithfully reconstructed from δ18 Oshell values assuming a δ18Owater signature that was extrapolated from coeval sirenian tooth enamel. Extreme values ranged between 12.3 and 22.0°C and agree well with previous estimates based on planktonic foraminifera and shark teeth. However, summer and winter temperatures varied greatly on inter-annual time-scales. Winter and summer temperatures averaged over 40 annual increments of three specimens equaled 13.6 ± 0.8°C and 17.3 ± 1.2°C, respectively. Unless many samples are analyzed, this variability is hardly seen in foraminiferan tests. Our data also revealed decadal-scale oscillations of seasonal extremes which have – in the absence of appropriate climate archives – never been identified before for the Oligocene. This information can be highly relevant for numerical climate studies aiming to predict possible future climates in a unipolar glaciated or, ultimately, polar ice-free world.