10th Baltic Stratigraphic Conference, Chyciny 12-14 September 20 I -
of oral and poster presentations
Middle and Upper Devonian of the Baltic Basin: sedimentary, stable isotope and magnetic features of the Skuodas-40 core (Lithuania) JUri Plado l , Leho Ainsaar 1, Ants Kaasik2, T6nu Meidla l , Siim Ots l and Sigitas Radzevicius 3 lDepartment o/Geology, University o/Tartu, Ravila 14A, 50411 Tartu, Estonia;
[email protected];
[email protected];
[email protected];
[email protected] 2Department o/Zoology, University o/Tartu, Vanemuise 46,51014 Tartu, Estonia;
[email protected] 3Department o/Geology and Mineralogy, Vilnius University, MK. Cillrlionio 21127, LT-0310] Vilnills, Lithuania; sigitas.radzevicius@g[.vu.lt
During the Devonian Period, the Baltic Plate was located in equatorial latitudes, forming the Laurussia palaeocontinent together with the former Lam'entia Plate. The suture of the former palaeocontinents comprised the Caledonide Mountains that were intensively eroded during the Devonian. This erosion produced a great mass of sandy deposits, preserved today as sandstones of a remarkable thickness. When the epeiric seas statied to transgress during the later Devonian times, deh'ital input decreased and formation of carbonate sediments began (Kleesment 1997). The Devonian sequence can be found in most of the Baltic Basin area, with the maximal thickness in the north-western part of Lithuania, thinning towards the north and south-east. Devonian strata are absent in nOl1hern Estonia and southern Lithuania. In Lithuania, the development of the Devonian basin is divided into 4 stages: (1) the Lochkovian renmant basin; (2 and 3) the shallow epeuic basin stage with mainly siliciclastic (pragian to early Frasnian time) and carbonate (major pati of the Frasnian) sedimentation; and (4) the Famennian infil1Ulg stage of the narrowing basu) (Luksevics et a1. 2014). The Skuodas-40 drill core, NW Lithuania, is studied herein by providing its renewed description, stable isotope composition, and magnetic susceptibility properties. The carbonate rocks of the Skuodas-40 core section were investigated for 8l3Ccarb' The lower Eife1ian, Frasnian and Famennian strata were studied in 180 bulk rock samples . Dolomites and dolomitic marls of the Ledai Fonnation (Narva Regional Stage) have 8 13 C values generally between 0 and +2%0 with a slightly increasing upward trend. Few analyses from the sandstone cement of the upper part of the Narva and Burmieki regional stages show diagenetically strongly depleted 8 13 C values (-3 to -7%0). The carbon isotope values of the Frasnian dolomites are the most valiable, changing between -2 and +5%0, with a few more depleted values of up to -8%0. Carbon isotope values in the limestones, dolomites and marls of the lower Famennian (from the Amule to the lower part of the Ketleri regional stages) are more stable, varying generally between -1 to +1%0. The Upper Famennian (upper Ketleri and Skervele regional stages) sandstone cements reveal again depleted 8 13 C values (-3 to -5%0). Comparison of the Skuodas-40 8 13 C curve with the Devonian isotope curves from central and southern Europe (Buggish and Joachimski 2006) shows similarities in the carbonate-rich intervals and in the secondary I3C depletion from the original marine values in the siliciclastic-rich samples in the Skuodas-40 section. Among the positive peaks in the 8 13 C curve of the Skuodas-40 core, the most prominent are Ul the upper Frasnian interval, in the Amule and Pamusis regional stages. The 8 13 C peak in the Arnule Regional Stage, with values reaching up to +5%0, may be correlated with the global Lower Kellwasser environmental and isotope event (Buggish and Joachlmski 2006). It is also possible that a smaller positive peak (+2%0) higher in the section, in the Siauliai Regional Stage, corresponds to the Upper Kellwasser Event. Mass specific magnetic susceptibility (x; m 3kg- l ) at 1000 Hz was determined with a SM-l 05 susceptibility meter (ZH instruments). It was done on selected 260 chips at about every 2.5 m and used to compute statistical data for individual stages. The magnetic susceptibility (K; SI units) study was based on measurements along the core using a Bartington MS2E sensor and a Bartington MS3 susceptibility bridge. The measurements were made in a scanning mode at every 17.5 cm in average, ending with 3741 data points. The data were statistically treated to create an average curve and to get hints for the rate of sedimentation as K depends on detrital input, and, thus, is a proxy for climatic changes due to eccentricity cycles (Da Silva et al. 2016). v
v
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1I O'h O,h Baltic Stratigraphic Conference, Ch o. of measurements
Median
Average
Standard Deviati on
Famennian
59
39.5
50.7
36.0
Frasnian
69
52.1
58.6
40.5
Givetian
52
52.6
318.2
69-1 .-' 694 .3
Eifelian
61
107.8
184.4
480.11 480.
I I
kg-l ) by stages. Table 1. Average values of mass specific magnetic susceptibility (x ( x 10-9 m 3kgloachimski,, M.M. 2006. Carbon isotope stratigrapby stratigraphy oftbe Devonian of Central and Southern Europe. Buggisch, W. and Joachimski Palaeogeography, Palaeoclimatology, Palaeoecology, 240, 68- 88. Chadimova L. , Slavik, L., Hilgen. El, M.1. 2016. Refining the Da Silva, A.e. , Hladil , 1. , Cbadimova F.J., Babek, O. and Dekkers, M.J. Early Devonian time scale using Milankovitch Milankovitcb cyclicity in Lochkovian-Pragian sediments (Prague Synfonn, Czech Czecb Republic). Earth and PlanetGlY Planetary Science Letters, 455, 125-139. 125- 139. .• Ellwood, B.B., Tomkin, 1.H., El Hassani, A., Bultynck, P., Brett, e.E. e.E.,, Schindler, E., Feist, R. and Bartholomew, A.1. 201l. 2011. Givetian A climate-driven model and development of a floating point time scale for the entire Middle Devonian Gi vetian Palaeoclimatology, Stage: A test using magnetostratigraphy susceptibility as a climate proxy. Palaeogeography, Palaeoclimatology. Palaeoecology, 304, 85- 95. Palaeoecology Kleesment, A. 1997. Fonnation of the Territory, Devonian sedimentation basin. In: A. Raukas and A. Teedumae (Eds.), Geology and Mineral Resources of Estonia, pp. 205-209. Estonian Academy Publishers, Tallinn. l 2014. The Devonian Devoruan stratigraphic succession and Q. , Saks, T., Popovs, K. and latnieks, Jatnieks, 1. Luksevics, E. , Stinkulis, Q., l Pais, 1.e. le. Kullberg and S. Finney (Eds.), STRATI 2013, evolution of the Baltic sedimentary basin. In: R. Rocba, Rocha, 1. pp. 539- 541. Springer, Switzerland.
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