Integrated Ocean Drilling Program Expedition 347 aimed to retrieve sediments from different settings of the Baltic Sea, encompassing the last interglacial-glacial cycle to address scientific questions along four main research themes: 1. Climate and sea level dynamics of marine isotope Stage (MIS) 5, including onsets and terminations; 2. Complexities of the latest glacial, MIS 4-MIS 2; 3. Glacial and Holocene (MIS 2-MIS 1) climate forcing; and 4. Deep biosphere in Baltic Sea Basin (BSB) sediments. These objectives were accomplished by drilling in six subbasins: (1) the gateway of the BSB (Anholt), where we focused on sediments from MIS 6-5 and MIS 2-1; (2) a subbasin in the southwestern BSB (Little Belt) that possibly holds a unique MIS 5 record; (3, 4) two subbasins in the south (Bornholm Basin and Hanö Bay) that may hold long complete records from MIS 4-2; (5) a 450 m deep subbasin in the central Baltic (Landsort Deep) that promises to contain a thick and continuous record of the last ~14,000 y; and (6) a subbasin in the very north (Ångermanälven River estuary) that contains a uniquely varved (annually deposited) sediment record of the last 10,000 y. These six areas were expected to contain sediment sequences representative of the last ~140,000 y, with paleoenvironmental information relevant on a semicontinental scale because the Baltic Sea drains an area four times as large as the basin itself. The location of the BSB in the heartland of a recurrently waning and waxing ice sheet, the Scandinavian Ice Sheet, has resulted in a complex development: repeated glaciations of different magnitudes, sensitive responses to sea level and gateway threshold changes, large shifts in sedimentation patterns, and high sedimentation rates. Its position also makes it a unique link between Eurasian and northwest European terrestrial records. Therefore, the sediments of this largest European intracontinental basin form a rare archive of climate evolution over the latest glacial cycle. High sedimentation rates provide an excellent opportunity to reconstruct climatic variability of global importance at a unique resolution from a marine-brackish setting. Comparable sequences cannot be retrieved anywhere in the surrounding onshore regions. Furthermore, and crucially, the large variability (salinity, climate, sedimentation, and oxygenation) that the BSB has under
Laminated, organic‐rich silts and clays with high dissolved gas content characterize sediments at IODP Site M0063 in the Landsort Deep, which at 459 m is the deepest basin in the Baltic Sea. Cores recovered from Hole M0063A experienced significant expansion as gas was released during the recovery process, resulting in high sediment loss. Therefore, during operations at subsequent holes, penetration was reduced to 2 m per 3.3 m core, permitting expansion into 1.3 m of initially empty liner. Fully filled liners were recovered from Holes B through E, indicating that the length of recovered intervals exceeded the penetrated distance by a factor of >1.5. A typical down‐core logarithmic trend in gamma density profiles, with anomalously low‐density values within the upper ∼1 m of each core, suggests that expansion primarily occurred in this upper interval. Thus, we suggest that a simple linear correction is inappropriate. This interpretation is supported by anisotropy of magnetic susceptibility data that indicate vertical stretching in the upper ∼1.5 m of expanded cores. Based on the mean gamma density profiles of cores from Holes M0063C and D, we obtain an expansion function that is used to adjust the depth of each core to conform to its known penetration. The variance in these profiles allows for quantification of uncertainty in the adjusted depth scale. Using a number of bulk 14C dates, we explore how the presence of multiple carbon source pathways leads to poorly constrained radiocarbon reservoir age variability that significantly affects age and sedimentation rate calculations.
Finnish Lapland is known as an area where numerous sites with sediments from Pleistocene glacial and interglacial periods occur. Recent sedimentological observations and dating call for reinterpretation of the record, which shows a complicated Mid-Weichselian ice-sheet evolution within the ice-divide zone. Here, a large, previously unstudied section from a former Hannukainen iron mine was investigated sedimentologically and dated with optically stimulated luminescence (OSL). Ten sedimentary units were identified displaying a variety of depositional environments (glacial, glaciolacustrine, fluvial and aeolian). They are all -except for the lowermost, deeply weathered till -interpreted to be of Mid-or Late Weichselian/Holocene age. Five OSL samples from fluvial sediments give ages ranging from 55 to 35 ka, indicating two MIS 3 ice-free intervals of unknown duration. The Mid-Weichselian interstadial was interrupted by a re-advance event, which occurred later than 35 ka and caused glaciotectonic deformation, folding and stacking of older sediments. This new evidence emphasizes the importance of the Kolari area when unravelling the complex Late Pleistocene glacial history of northern Finland and adjacent regions. -Pekka Salonen (veli-pekka.salonen@helsinki. Veli
The study presents the first description and analysis of ostracod records from three sites cored in different parts of the Baltic Sea during the IODP Expedition 347, Baltic Sea Paleoenvironment. Our data present the first high‐resolution ostracod records from the Late Weichselian and Holocene sediments collected across the Baltic Sea Basin. Using published data on modern ostracod species ecology of the Baltic Sea, we were able to provide ostracod‐based palaeoreconstructions of the history of the region. The stratigraphical framework for the sites is based on radiocarbon‐based age models. The three studied sites reveal different ostracod assemblage successions that reflect environmental changes in the study area. Site M0060, located in the Kattegat area, contains the oldest ostracod assemblages that document a marine environment with very high sedimentation rates during the most recent deglaciation. Between ~13 000 and 7500 cal. a BP a modern‐like near‐shore environment developed. Site M0059 in the southwestern Baltic Sea, Little Belt area, contains assemblages reflecting the transition from a freshwater lake to the brackish Littorina Sea between ~7500 and 7300 cal. a BP. Site M0063 is the deepest location in the central Baltic, Landsort Deep, and yielded very limited ostracod data, but comparison with our organic carbon data allowed us to distinguish the Yoldia Sea, Ancylus Lake and Littorina Sea intervals. The ostracod record correlates well with the organic carbon record with alternation between periods of hypoxia and periods of low oxygen that still supported ostracods.
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