| 11. |
- Piličiauskienė, Giedrė, et al.
(författare)
-
The Origin of Late Roman Period-Post-Migration Period Lithuanian Horses
- 2022
-
Ingår i: Heritage. - : MDPI AG. - 2571-9408. ; 5:1, s. 332-352
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper, we present the 87Sr/86Sr data of 13 samples from horses from six Lithuanian burial sites dating from the 3rd to the 7th C AD. Alongside these data, we also publish the bioavailable 87Sr/86Sr data of 15 Lithuanian archaeological sites, based on 41 animals which enabled the construction of a reliable baseline for the Southeast Baltic area. The 87Sr/86Sr values partially confirmed the hypothesis that the unusually large horses found in Late Roman Period to Post-Migration Period burials are of non-local origin. Of the three non-local horses identified, two were among the largest specimens. However, the overlap of bioavailable 87Sr/86Sr data across different European regions does not permit us to establish whether the non-local horses originated from other areas in Lithuania or from more distant regions. With regards to the 87Sr/86Sr data, the place of origin of the non-local horses could be Southern Sweden. This encourages discussions on the possible directions of migration and compels us to rethink the current models that posit South and Central Europe as the main sources of migration. The results of the 87Sr/86Sr, δ13C, and δ15N analyses demonstrate that horses buried in the same cemetery had different mobility and feeding patterns. Differences could be due to the different function and sex of the horses as well as the lifestyle of their owners. The most sedentary horses were pregnant mares, while the extremely high δ15N of three horses may reflect additional fodder and probably a better diet.
|
|
| 12. |
|
|
| 13. |
- Tual, Lorraine, et al.
(författare)
-
Rapid, paced metamorphism of blueschists (Syros, Greece) from laser-based zoned Lu-Hf garnet chronology and LA-ICPMS trace element mapping
- 2022
-
Ingår i: Chemical Geology. - : Elsevier. - 0009-2541 .- 1872-6836. ; 607
-
Tidskriftsartikel (refereegranskat)abstract
- Unravelling the timing and rate of subduction-zone metamorphism and H2O release requires linking time to the compositional changes of petrogenetic indicator minerals in blueschists and eclogites. Garnet is a key mineral in this regard, as it forms by, and records, H2O-releasing mineral reactions that can be linked to pressure and temperature conditions. These can be placed in time using chronology. Bulk-or multi-grain ages are the norm in garnet chronology. While these ages provide important and precise time constraints on reactions across both facies, the duration, rates and style of growth???crucial parameters in the petrological and geochemical evolution of subducting oceanic crust???remain unconstrained. Domain dating, i.e., dating of individual growth zones, is necessary to investigate these aspects, but is generally impeded in ???common???-sized garnet grains due to sample size requirements. To overcome these limitations, we use a low-loss micro-sampling by laser cutting combined with Lu-Hf chronology. We used this approach to precisely date multiple growth zones in a 1-cm garnet grain from glaucophane-bearing micaceous schist of the Cycladic Blueschist Unit (CBU), Syros Island, Greece. The analysis was combined with major- and trace-element mapping (EPMA, LA-ICPMS) to investigate garnet petrogenesis. Garnet core and mantle zones are chemically comparable and identical in age within 0.1 Myr precision (2??), indicating an initial growth pulse at 51.8 ?? 0.1 Ma (MSWD = 1.13). The two rim zones, which are chemically distinct, were resolvably younger at 51.3 ?? 0.2 Ma (MSWD = 0.67). Integrated with compositional data, these age constraints provide a time-resolved record of extremely fast, pulsed garnet growth and fluidrelease reactions, such as chloritoid breakdown. These reactions can be considered near-instantaneous on subduction time scales, indicating that re-equilibration far outpaces changes in pressure and temperature conditions. The analysed sample is associated with the upper-subunit of the CBU with oceanic affinities, which does not share the last part of the prograde history with the rest of the CBU, i.e., the margin sub-unit. We interpret our sample as a sliver that became attached to the base of the ophiolitic sub-unit and was thrusted onto the lower margin unit at high-pressure. Beyond providing insights into the timing of subduction-zone processes, our new protocol for zoned garnet Lu-Hf geochronology of ???common-sized??? garnet opens new possibilities for constraining the causes and rates of garnet growth and the pace of tectonic processes in general.
|
|
| 14. |
- Walczak, Katarzyna, et al.
(författare)
-
Late Neoproterozoic extended continental margin development recorded by the Seve Nappe Complex of the northern Scandinavian Caledonides
- 2022
-
Ingår i: Lithos. - : Elsevier. - 0024-4937 .- 1872-6143. ; 416
-
Tidskriftsartikel (refereegranskat)abstract
- The Scandinavian Caledonides comprise nappe stacks of far-travelled allochthons that record the opening and closure of the Iapetus Ocean, culminating with the collision of Baltica and Laurentia. The Seve Nappe Complex (SNC) of the Scandinavian Caledonides comprises relics of the outermost Baltoscandian passive margin that were subducted to mantle depths during ocean closure. Subduction of these rocks overprinted much of the Neoproterozoic record for Iapetus Ocean formation, and as a result, much of the work conducted in the SNC has focused solely on the Caledonian orogenic history.& nbsp;In this study, we combined petrological and geochronological work to expand the knowledge about the Neoproterozoic metamorphic history of the Baltoscandian margin in the understudied Vaivancohkka-Salmmecohkat region of the northern Scandinavian Caledonides. The work focused on rocks that belong to the upper gneiss unit, which constitutes part of SNC in the region. The unit comprises migmatitic paragneisses and garnet-mica schist containing metamafic bodies. U-Pb zircon and Th-U-total Pb monazite dating of the migmatitic paragneiss yielded consistent age of metamorphism in 602 +/- 5 Ma and 599 +/- 3 Ma, respectively. A similar U-Pb age of 604 +/- 8 Ma was obtained for the zircon from the leucocratic vein transecting the amphibolite within the studied gneiss. Interestingly, no Caledonian ages were identified. Likewise, no evidence for high or ultra-high pressure conditions was found, neither in the gneisses/schists nor in the metamafic rocks. Petrographic observations and calculated metamorphic P-T conditions indicate that rocks belonging to upper gneiss unit underwent upper-amphibolite facies metamorphism in a melt stability field; 8.0-10.5 kbar at 750-790 degrees C.& nbsp;Since the studied rocks underwent high-grade metamorphism in the Ediacaran and lack obvious evidence for Caledonian high-pressure metamorphism, the studied part of the SNC offers an extraordinary insight into the Late Neoproterozoic history of the hot, extended Baltoscandian margin.
|
|
