Sedimentary facies and clay mineralogy of the late Pleistocene Landsort Deep sediments, Baltic Sea — Implications for the Baltic Ice Lake development

Figures & data

Figure 1. (a) Map of the study area in the Baltic Sea (Bathymetry Database v0.9.3 by Hell and Öiås 2014). The black rectangle indicates the location of the insert showing detailed location of Site M0063 in the Landsort Deep. The present surface water circulation (gray arrows) and deeper circulation (light gray arrows) are redrawn from Larsson et al. (2017). (b) Pre-Quaternary geology of the Baltic Sea region (modified from Rosentau et al. 2017).

Figure 2. Evolution of the Baltic Ice Lake and decay of the Fennoscandian Ice Sheet at ~13.0 and 11.5 ka BP. Source: Kallio (2006), by M. Saarnisto/Geological Survey of Finland. Black dot marks the location of the Landsort Deep, black triangle marks Mt. Billingen, and black arrow marks the Öresund strait. The contemporary continental rivers (blue lines) are redrawn from Patton et al. (2017).

Figure 3. Core images representing the main lithologies of Units V and VI: (a) brownish/reddish sandy silt with slightly disturbed laminated structures (347-M0063C-38-2, 89–90.5 mbsf); (b) silt–clay with sandy interlaminaes and massive structures (347-M0063C-37-2, 85.7–87.2 mbsf; (c) clay and silt with coarser interlaminaes (347-M0063C-36-1, 80.9–82.4 mbsf); (d) interlaminated silt and clay, slightly disturbed, carbonate concretion (347-M0063C-33-2, 72.5–74 mbsf); (e) silty clay laminated by color and grain size (347-M0063C-30-2, 62.6–64.1 mbsf); (f) silty clay, homogeneous gray clay interbeds (347-M0063C-27-1, 52.6–54.1 mbsf); (g) dark gray/grayish brown silty clay, contorted silt laminaes, convolute bedding, slumping (347-M0063C-25-2, 48.6–50 mbsf); (h) dark gray clay (347-M0063C-24-2, 47.4–48.6 mbsf). Images downloaded from the Pangaea data portal (Expedition 347 Scientists 2014b).

Figure 4. Representative images of sedimentary lithofacies from Units V and VI: (a) disorganized sandy–silty clay (diamict), interval 347-M0063C-38-2, 115 to 135 cm; (b) laminated fine sand and silt (Facies 2), sandy planar laminae indicated with black thin arrows, interval 347-M0063C-38-2, 90 to 100 cm; (c) sandy silt/clay couplets (Facies 3) with thickness of 30 to 60 mm, boundaries indicated with black arrows, interval 347-M0063C-38-2, 10 to 40 cm; (d) sandy silt–clay couplets (Facies 3) with thickness of 10 to 30 mm, boundaries indicated with black arrows, interval 347-M0063C-37-2, 85 to 115 cm; (e) silt–clay couplets (Facies 4) with thickness of 20 to 30 mm, light colored silty portions are laminated, boundaries indicated with black arrows, interval 347-M0063C-30-2, 55 to 75 cm; (f) silt–clay couplets (Facies 4) with thickness of 5 to 20 mm, couplet boundaries (indicated with black arrows) can be diffuse and darker colored clay portions become thicker and massive, interval 347-M0063C-27-1, 105 to 135 cm; (g) laminated to massive silty clay (Facies 5), silty laminae indicated with black thin arrows, interval 347-M0063C-33-2, 87 to 97 cm; (h) faintly laminated clay (Facies 6), interval 347-M0063C-27-1, 55 to 70 cm; (i) deformed clay to silt–clay (Facies 7), microscale transverse fault indicated with black thin arrow, interval 347-M0063C-25-2, 80 to 105 cm. Images downloaded from the Pangaea data portal (Expedition 347 Scientists 2014b).

Table 1. Summary of the sedimentary lithofacies types used for the Landsort Deep sediments.

Lithofacies	Characteristics	Interpretation	Unit^a
Facies 1: Disorganized sandy–silty clay (diamict)	Subangular sand clasts dispersed in fine-grained matrix, bed thickness 10–40 cm	Debris flow^b or deformed fine sediment with dropstones^c	VIc
Facies 2: Laminated sand and silt	Horizontal lamination, sometimes convoluted, thickness 1–5 mm	Planar laminae, reworking and sorting of sediments by bottom current action,^b or episodic sharp-based underflow layers along the bottom of the lake^c	VIc
Facies 3: Sandy silt–clay couplet	Rhythmically laminated couplets composed of a basal sandy silt and laminated sandy–silt portion and faintly laminated to massive clay blanket; couplet thickness 10–60 mm, subangular sand and few dispersed centimeter-scale clasts	Proximal varve deposits (annual summer and winter portions),^c oversize clasts, and dropstones indicate glaciolacustrine environment and ice rafting	VIc
Facies 4: Silt–clay couplet	Rhythmically laminated couplets composed of a basal silt portion (barren for diatomaceous components) and weakly laminated to massive clay portion, couplet thickness 5–30 mm; some couplets can be diffuse	Distal varve deposits representing distal meltwater suspension plumes in a lake (annual summer and winter portions)^c	VIa
Facies 5: Laminated to massive silty clay	Fine-grained sediment showing very thin silt laminae, some 1–2 mm thick, irregular lamination or structureless	Winnowed lamination by reworking by bottom current^b	VIb
Facies 6: Clay	Massive, sometimes mottled	Suspension sedimentation^b	VIa
Facies 7: Deformed clay to silty clay	Fine-grained sediment showing soft sediment folds, microfaulting, and convolute bedding	Slump events^b	V

Notes. ^aIndicates in which unit/subunit each lithofacies mainly occurs.

^bPickering et al. (1986, 1989).

^cAshley (2002).

Figure 5. Sand, silt, and clay content (vol%) of the studied samples from various depths from Units V and VI. Grain size of <2 µm is classified as clay, 2 to 63 µm, is silt and >63 µm is sand. Gamma wet bulk density and magnetic susceptibility values data from the Pangaea data portal (Expedition 347 Scientists 2014b).

Figure 6. Clay mineral distribution and kaolinite–chlorite and quartz–feldspar ratios of the studied samples from Units V and VI.

Figure 7. Water and carbon content from Units V and VI. Data for total organic carbon (TOC), total inorganic carbon (TIC), and total carbon (TC) from the Pangaea data portal (Expedition 347 Scientists 2014b). LOI = Loss on ignition.

Figure 8. X-ray diffractogram of a clay fraction sample from the Landsort Deep sediments showing the principle of the major clay and non-clay mineral evaluation used in this study identified from three runs: normal, ethylene glycol treated, and heated (550°C).

Figure 9. Inferred age–depth model of the sediment deposition of the Baltic Ice Lake stage based on the present multiproxy study from the Landsort Deep sediments from Units V and VI. The lenses illustrate the time span of the different stages of the Baltic Ice Lake presented in the figure. Pollen age distributions by Andrén et al. (2015) are shown by dashed lines.

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