Download presentation
Presentation is loading. Please wait.
1
ISZA, Tidal cyclicity reflected in growth lines of bivalves from the Budafok Sand Formation, Lower Miocene, Hungary Németh Alexandra Dr. Sztanó Orsolya (ELTE Általános és Alkalmazott Földtani Tanszék) Dr. Szente István (ELTE TTK Természetrajzi Múzeum )
2
Contents Tidal effect on mollusc’s growth
2 Németh Alexandra Contents Tidal effect on mollusc’s growth Outcrop of Eggenburgian Budafok Sand Formation in Pék Street Analysis of Crassostrea gryphoides (Schloth) shell Paleoenvironmental conclusions
3
Conditions of macrotidal environment:
3 Németh Alexandra Formation of tide Conditions of macrotidal environment: -open seaways -intensified high tides e.g. wide self, long bays, Sztanó, 1995
4
Formation of growth increments and growth lines
4 Németh Alexandra Formation of growth increments and growth lines Matthewson, 2008
5
Tidal effect on growth lines
5 Németh Alexandra Tidal effect on growth lines Murakoshi, 1993
6
Geological settings of Budafok Sand
6 Németh Alexandra Geological settings of Budafok Sand Báldi, 1997
7
Lithology of the outcrop in the end of Pék Street
7 Németh Alexandra Lithology of the outcrop in the end of Pék Street Báldi, 1958 Kereszt hegy
8
Sample preparation -planes by polishing
8 Németh Alexandra Sample preparation -planes by polishing -etched (37,5% HCl for a few minutes) and non-etched samples -coating with coal -backscattered electron images on AMRAY-1830 I/T6 type electronmicroscope, in 10-5 mbar vacuum, 20 kV, x magnification
9
Results: Cyclically changing growth-striae
9 Németh Alexandra Results: Cyclically changing growth-striae (non-etched, non-polished) 2 mm
10
Periodical condensation and rarifaction in growth lines
10 Németh Alexandra Periodical condensation and rarifaction in growth lines BSE image of a polished and etched plane 3 2 1
11
Periodic change in the distance of growth lines
11 Németh Alexandra Periodic change in the distance of growth lines 1 2 BSE image of a polished and etched plane 1 Distance of lines: 5-10 micrometer 3
12
12 Németh Alexandra Variation of simple and double growth increments , strong and dim growth lines 1 2 2 3 3
13
Variation of wide and narrow growth increments
13 Németh Alexandra Variation of wide and narrow growth increments 1 2 4 4 3
14
Németh Alexandra 14 Interpretation Periodical condensation and rarifaction in non-growth lines on striae - Annual change in temperature - winter: cool, summer: water temperatures above 19°C (non-etched, non-polished) 2 mm
15
Interpretation spring and neap tide diurnal inequality
Németh Alexandra 15 Interpretation = diurnal inequality is high enough and the higher low tide is low enough to induce growth line spring and neap tide diurnal inequality Yuriage, Miyagi, Japán: dec. 8 –febr. 1
16
Tidal effect on the distance between growth lines
16 Németh Alexandra Tidal effect on the distance between growth lines Murakoshi, 1993
17
Central-Paratethys during the Eggenburgian, North-Hungarian Bay
17 Németh Alexandra Central-Paratethys during the Eggenburgian, North-Hungarian Bay Sztanó, 1995
18
Summary: Examined Crassostrea specimens:
18 Németh Alexandra Summary: Examined Crassostrea specimens: were living in a seasonaly changing environment semi-diurnal tides with strong diurnal inequality lower part of the intertidal zone A hypothesis by Báldi (1958): „Budafok Sand Formation accumulated in a tidal environment”, was proven from a paleobiological approach.
19
Thank you for your kind attention!
19 Németh Alexandra Thank you for your kind attention! Aknowledgements: Dr. Sztanó Orsolya Dr. Szente István Bendő Zsolt Pósch Dániel
Similar presentations
