. Collected reprints / Atlantic Oceanographic and Meteorological Laboratories [and] Pacific Oceanographic Laboratories. Oceanography vj* IRREGULARIY. â SHAPta I \AREA TRANS RIDGE TRANSVERSE VAUEY AV VA>IlLl|l°>âI i ⢠I N z. <â¢* .\0°v \lRREGUlARtY.â¢*NSV"SE VAllEY SE .^ , r ^\ Figure 4. Diagram- matic representation of the tectonic fabric of the study area out- lined from Figure 3. Azimuths of the major trends are noted. The TAG Hydrothermal Field is outlined (trap- ezoid). Note the north arrow in the upper left corner. several sites along transverse ridges (Tabl
. Collected reprints / Atlantic Oceanographic and Meteorological Laboratories [and] Pacific Oceanographic Laboratories. Oceanography vj* IRREGULARIY. â SHAPta I \AREA TRANS RIDGE TRANSVERSE VAUEY AV VA>IlLl|l°>âI i ⢠I N z. <â¢* .\0°v \lRREGUlARtY.â¢*NSV"SE VAllEY SE .^ , r ^\ Figure 4. Diagram- matic representation of the tectonic fabric of the study area out- lined from Figure 3. Azimuths of the major trends are noted. The TAG Hydrothermal Field is outlined (trap- ezoid). Note the north arrow in the upper left corner. several sites along transverse ridges (Table 2"; stations TAG 1972-8, TAG 1972-15). HEAT FLOW Five measurements of conductive transfer of heat through the sea floor were made by Langseth and others (1972). The heat-tlow measurements show higher heat flow through the transverse ridges ( to HFU) than through the intervening trans- verse valleys ( to HFU; Fig. 3). From the limited number of measurements, it is ambiguous whether this distribution of values is related to topography or to dis- tance from the rift valley. A large variation in heat flow occurs over a horizontal dis- tance of 5 km on one of the transverse ridges ( and HFU). A water-temperature profile parallel to the ocean bottom over the southeastern wall of the rift valley at the TAG Hydro- thermal Field was made with a 4-m-long vertical array of three thermistors mounted on a towed deep-sea camera (Rona and others, 1975). The profile revealed an ab- rupt anomaly of +°C associated with a gradient of °C/m, warming down- ward within 20 m of the bottom along a horizontal distance of about 350 m be- tween depths of 3,030 and 2,950 at a step- like level on the southeast wall (Fig. 6, profile F), where hydrothermal material 'Table 3, "Rocks recovered from the Study Area of the NOAA Trans-Atlantic Geotraverse (TAG) on the Mid-Atlantic Ridge Crest at lat. 26°N," GSA sup- plementary material 76-4,
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