Moldavites from Lusatia (Germany) I: Occurrences and Geo- Logy of Their Host Sediments J.-M

LPS XXVI 827

MOLDAVITES FROM LUSATIA (GERMANY) I: OCCURRENCES AND GEO- LOGY OF THEIR HOST SEDIMENTS J.-M. Langel, G. Knuth2, H. Wagner3. lInstitut liir Geologische Wissenschaften und Geiseltalmuseum, Martin- Luther-Universitit Halle-Wittenberg, present adress: Institut fiir Geophysik und Geologie, UniversiW Leipzig, Talstrak 35, D-04103 Leipzig; 2Geologisches Landesamt Sachsen-Anhalt Halle (Saale); 3Museum der West- lausitz Kamenz.

Abstract: Over 25 years after the first find of a moldavite in Lusatia ("Lausitz"), Germany (E-Saxony, SE-Brandenburg) there are still no detailed studies of these glasses and their host sediments. This work attempts to make a contribution to the discussion about the origin of the Lusatian moldavites. This was done by sedimentary-petrographical studies of moldavite-bearing sediments. Samples: This work presents a documentation of Lusatian moldavites and the surveying of selected outcrops which yield moldavites. 111 Lusatian moldavites with a total mass of more than 600 g have already been registered. Sediment samples from selected profiles from various localities were used for sedimentary-petrographical analyses. Priority was given to Late Tertiary moldavite-bearing sediments: Older Senftenberg Elbe Gravels ("here Senftenberger Elbeschot- tern) and Upper Gravel Sands ("Obere Kiessande") of the Rauno Formation ("Raunoer Folge"). Results: The discussion on the origin of Lusatian moldavites is close connetected with the stratigraphic position of their host sediments. Previous studies suggest a fluvial transport of moldavites from Bohemia to Lusatia [l,2]. Investigations of the Late Tertiary moldavite-bearing sediments show differences between the Older Senftenberg Elbe Gravels in Upper Lusatia and the Upper Gravel Sands of Rauno Formation in Lower Lusatia: Sediments of the Older Senftenberg Elbe Gravels are usually coarser and less well sorted than those of the Rauno Formation. Within the Rauno Formation the Lower Gravel Sands, which are the probably moldavite-free, are more fine-grained and better sorted than the Upper Gravel Sands. The sedimentary environments of the Older Senftenberg Elbe Gravels and Upper Gravel Sands were quite similiar. Both show features of quick and turbulent sedimentation (braided rivers). Older Senftenberg Elbe Gravels and Lower Gravel Sands display a higher content of instable heavy minerals than the Upper Gravel Sands. In the Lower Gravel Sands this can be related to reworked marine Tertiary material. In the study area the ratio of staurolite/sillimanite is useful to distinguish the Rauno Formation. Very rare occurrences of leaf impressions lead to a position of the Upper Gravel Sands of Rauno Formation in the megafloral zone XI11 [3]. The flora from Ottendorf-Okrilla (Older Senf- tenberg Elbe Gravels) is possibly negligible younger [4]. In their composition the florae of Upper Gravel Sands and Older Senftenberg Elbe Gravels indicate a more Miocene than Pliocene age [5]. This observations are supported by the high maturity of these sediments (high concen- trations of quartzic materials (90 to 95 %) and stable heavy minerals) compared to the Pliocene moldavite-bearing sediments in Bohemia. However, a fluvial transport from South Bohemia can be excluded by existence of a watershed divide up to the end of Lower Pliocene [6,7]. Acknowledgement: J.-M. Lange's work was supported by the Deutsche Forschungsgemeinschaft (Re 92911- 1) and the Sachsen-Anhalt state. References: [l] ROSTR et al. (1979) Cas. Mineral. Geol. 24, 263-271; [2] BOUSKAV. and KONTAJ. (1986) Acta Univ. Carolinae, Geol., 1-126; [3] MAI D.H. (1967) Abh. zentr. geol. Inst. 10, 55-81; [4] Mai D.H. pers. cornm.; [5] Walther H. pers. comm.; [6] BOUSKAV. (1987) 2nd Intern. Conf: Natural Glasses, 15-23; [7] MALKOVSK*M. (1975) Vest. WG50, 27-3 1; [8] L~TSCHD. (1968) GrundriJ der Geologie der DDR, 356-379; [9] ALEXOWSKYW. et al. (1989) Geoprofil 1,57-62; [lo] STANDKEG. and STRAU~C. (1991) Abstr. 38. Jahrestag. GGW, 84-89; [ll] WOLFL. and SCHUBERTG. (1992) Geoprofil4, 1-43.

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MOLDAVITES FROM LUSATIA (GERMANY) I: J.-M. Lange et al. Table 1. Occurrences of moldavites in I usatia site geographic coordinates distance moldavite-bearing known first find I from Riesl) sediments finds d [kml lithology n Year U~mrLusatia

Wiesa 151'15'15" N 114'08'00" E 366 redeposited in Pleistocene 3 1 1972 Miltitz 151"12'00"N I 14"11'30"E 365 1 1 1989 1,nwer Lusatia

Rauno Formation: quartz- 51'33'00" N 14"01t30"E rich braided river deposits 1984 51'36'00" N 14"18'00" E 1983 Roitz 51 35'00"N 14'19'30" E

Formation 1993 1980

1) The distances (d) hrnthe Ries Crater are calculated by determination of orthodromes: d = r . arccos 6 = r . =(sin cpl. sin cp2 + cos 91. cos q2. cos('&-L,)) where cpl = 48'52'51" N, Ll = 10'33'31" E (latitude and longitude of center of the Ries Crater) and r = 6371 km (earth radius); 2, total weight; 3) largest specimen

Table 2. Correlation of the moldavite-bearing sediments in Lusatia, Germany (compiled after [4,5, 8-1 11); A moldavite occurrence

Upper Brieske Member

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