LATE GLA CIAL AND HO LO CENE MOL LUS CAN AS SEM BLAGES IN DE POS ITS FILL ING PALAEOLAKES IN NORTH ERN PO LAND
Late Gla cial and Ho lo cene car bon ate lac us trine de pos its de vel oped as lac us trine chalk and cal car e ousgyttja are fairlywide spread across north ern Po land. They form fill ings of palaeolakes which de vel oped dur ing the deglaciation. Thesefor ma tions are usu ally cov ered by peat. Rich and di ver si fied malacofauna has been found in the afore men tioned sed i -ments. The pro files from 154 sites de scribed and pub lished by var i ous au thors were sub jected to malacological anal y- sis. In the whole ma te rial, 18 mol lus can as sem blages were dis tin guished, rep re sent ing three types of hab i tats: terres-trial, of tem po rary wa ter bod ies, and of per ma nent wa ter bod ies. The com po si tion and struc ture of these as sem blagesal lowschar ac ter iz in g cli mate and dif fer en ti at ing hab i tatsThe . time-se quencesof malacological as sem blages pro vided pos si bil ity to de fine three types of malacological se quences. On the ba sis of these suc ces sions, a scheme of the lakewa ter bod ies evo lu tion dur ing Late Gla cial and in north ern Po land was elab o rated.
Late Gla cial and Ho lo
This study pro vides a veg e ta tion and cli mate his tory of an al pine wet land in the cen tre of China’s Qinghai–Ti betan Pla teau (QTP) over the last 14.8 ka. High res o lu tion cli mate prox ies in clude veg e ta tion (pol len), geo chem i cal (Ba, Rb, dC) and phys i cal (par ti cle size and mag netic sus cep ti bil ity) data; op ti cally stim u lated lu mi nes cence (OSL) and AMS ra dio car bon dat ing were used to re con struct the en vi ron men tal changes in the wet land eco sys tem. Based on phys i cal and geo chem i cal prox ies, the sucession di vided into five strati graphic units en com pass ing time in ter vals of 14.76–14.31, 14.31–13.17, 13.17–4.47, 4.47–0.51 and 0.51–0 ka. The av er age sed i men ta tion rate of all these units was 0.098 mm/a. The study showed that this eco sys tem was sen si tive to cli mate change.
Ostracod-based environmental reconstruction over the last 8,400 years of Nam Co Lake on the Tibetan plateau
From a 332-cm long lacustrine core taken at 60 m water depth and 25 surface sediment samples taken at different water depth sites in Nam Co lake (4,718 m a.s.l.) in the middle-south part of the Tibetan Plateau, we identified nine species of ostracods (Crustacea: Ostracoda) belonging to six genera. Using lithological data, auto-ecological information of the recovered taxa and an ostracod-based transfer function for water depth reconstruction, we distinguished three main environmental stages over the past 8,400 years: during Stage I (8,400–6,800 yr BP), the climate changed from warm-humid to cold-humid, and eventually to cold-arid. The water depth of the site was much lower than today and changed from an estimated 50 to 20–30 m. During Stage II (6,800–2,900 yr BP), environmental conditions were again warm-humid, turning into a cold-arid episode. The lake water depth initially stayed much shallower than today, but then gradually deepened to around 50 m. At the earlier period of Stage III (2,900 yr BP–present), the climate became again warm-humid from cold-arid status. There was a cold-dry event between 1,700 and 1,500 yr BP, which intensified afterward while the surface run off weakened. Early in this stage, lake depth decreased slightly, but then it continuously deepened to 60 m. Our results revealed that central Tibet experienced wavily warm toward tendency in early Holocene, a shift from warm-humid to cold-dry conditions in the middle Holocene, and from warm-humid to cold-dry conditions in the late Holocene. They also show that ostracod assemblages are not only indicative of cold-warm conditions, but are also usable to imply the dry–wet status of a lake area by the inferring water depth variations. Finally, this study provides baseline data on (natural) climate change in this mountain region against which to compare global change impacts.