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With 18 figures ZusammenfassungUntersucht wurden Profile yon Kohlenstotf-Isotopen mariner Karbonate aus dem Oberperm und der Untertrias der Tethys-Region aus 20 Lokalit~iten in Jugoslawien, Griechentand, der Tfirkei, der Sowjet-Republik Arrnenien, dem Iran, Pakistan, Indien, Nepal und China. Die oberpermischen Proben zeigen dieselben hohen positiven 613C Werte, wie sie vorher auch aus den oberpermiscben Beeken NWEuropas und dem Westen der USA berichtet wurden. Anhand yon vollstandigeren Abschnitten der Tethys kann dargelegt werden, dai~ die 6 13C Werte yon der Murgabium-bis zur Dzhulfium-Phase des Oberperms abnehmen und dann innerhalb der letzten zwei Biozonen des Dorashamiums abrupt gegen Null verlaufen. Diese 6 13C Niveaus sind repr~-sentativ ffir die Tethys und den Weltozean. Sie gelten auSerdem ffir alle Wassertiefen, wie durch ~ihnliche Werte aus Tiefsee-Sedimenten yon Salamis (Griechenland) bes6itigt wird. Unsere Annahme ist, dag die hohen 6 13C Werte auf sp~itpal~iozoische Speicherung organiscben Kohlenstoffs zuriickzuffihren ist. Die Abnahme stellt episodische Sedimentationsschwankungen des organischen Materials dar, w~ihrend der die organischen Substanzen fiber einen Zeitraum yon mehreren Millionen Jahren zum Tel1 aufoxidiert wurden. Das Kohlenstoff-Isotop Profil entspricht parallelisiert in etwa dem Muster des Massen-Aussterbens w~ih-rend des Oberperms. AbstractProfiles of carbon isotopes were studied in marine limestones of Late Permian and Early Triassic age of the Tethyan region from 20 sections in Yugoslavia, Greece, Turkey, Armenian SSR,

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The Permian Chert Event (PCE) was a 30 Ma long episode of unusual chert accumulation along the northwest margin of Pangea, and possibly worldwide. The onset of the PCE occurred at about the Sakmarian^Artinskian boundary in the Sverdrup Basin, Canadian Arctic, where it coincides with a maximum flooding event, the ending of high-frequency/high-amplitude shelf cyclicity, the onset of massive biogenic chert deposition in deep-water distal areas, and a long-term shift from warm-to cool-water carbonate sedimentation in shallow-water proximal areas. A similar and coeval shift is observed from the Barents Sea to the northwestern USA. A landward and southward expansion of silica factories occurred during the Middle and Late Permian at which time warm-water carbonate producers disappeared completely from the northwest margin of Pangea. Biotically impoverished and increasingly narrow cold-water carbonate factories (characterised by non-cemented bioclasts of sponges, bryozoans, echinoderms and brachiopods) were then progressively replaced by silica factories. By Late Permian time, little carbonate sediments accumulated in the Barents Sea and in the Sverdrup Basin, where the deep-to shallow-water sedimentary spectrum was occupied by siliceous sponge spicules. By that time, biogenic silica sedimentation was common throughout the world. Silica factories collapsed in the Late Permian, abruptly bringing the PCE to an end. In northwest Pangea, the end-Permian collapse of the PCE was associated with a major transgression and with a return to much warmer oceanic and continental climatic conditions. Chert deposition resumed in the distal oceanic areas during the early Middle Triassic (Anisian) after a 8^10 Ma interruption (Early Triassic Chert Gap). The conditions necessary for the onset, expansion and zenith of the PCE were provided by the thermohaline circulation of nutrient-rich cold waters along the northwestern and western margin of Pangea, and possibly throughout the world oceans. These conditions provided an efficient transportation mechanism that constantly replenished the supply of silica in the area, created a nutrient-and oxygen-rich environment favouring siliceous biogenic productivity, established cold sea-floor conditions, hindering silica dissolution, while increasing calcium carbonate solubility, and provided conditions adverse to organic and inorganic carbonate production. The northwest margin of Pangea was, for nearly 30 Ma, bathed by cold waters presumably derived from the seasonal melting of northern sea ice, the assumed engine for thermohaline circulation.This process started near the Sakmarian^Artinskian boundary, intensified throughout Middle and Late Permian time and ceased suddenly in latest Permian time. It led to oceanic conditions much colder than normally expected from the palaeolatitudes, and the influence of cold northerly-derived water was felt as far south southern Nevada. The demise of silica factories was caused by the rapid breakdown of these conditions and the establishment of a much warm...