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IODP Expedition 330

Louisville Seamount Trail

Daily Science Report for 31 January 2011

LOCATION: Site U1376 (Prospectus Site LOUI-7A). Position: 32°12.99' S Lat., 171°52.84' W Long.

SCIENCE UPDATE: After a successful (open hole) re-entry into Hole U1376A in the early morning, coring of the massive, highly olivine-augite-phyric lava flow continued today with Cores U1376A-11R and -12R (86.8 to 101.2 mbsf). Drilling has now advanced 28 m into this single unit with excellent recovery of 90% but with a slow penetration rate of ~1m/hr. At noon, a Site U1375 meeting was conducted with presentations from the Sedimentology, Paleontology, Igneous Petrology, Alteration Petrology and Structural Geology groups. The Site U1375 reports were submitted by the end of the day.


Daily Science Report for 30 January 2011

LOCATION: Site U1376 (Prospectus Site LOUI-7A). Position: 32°12.99' S Lat., 171°52.84' W Long.

SCIENCE UPDATE: Cores U1376A-8R to -10R (67.0 to 86.8 mbsf) were received with 90% recovery. The high recovery is particularly incredible since most of the cored interval is composed of massive fresh igneous rock. Core U1376A-8R recovered more of the fragmented moderately olivine- and pyroxene-phyric lava breccia within a hyaloclastite matrix. The breccia transitions downhole into a massive (>14 m thick) lava flow comprising the lower half of Core U1376A-8R and continuing throughout Core -10R. The rock is highly olivine-augite phyric and the olivine crystals are very well preserved, which makes them well suited for all kinds of geochemical studies. The ongoing investigation of macrofossil fragments found in the algae reef carbonates above the breccia indicates a Cretaceous age for the igneous succession drilled at this site. Since the drill bit had accumulated 72.4 hours of rotation, we decided to exchange the bit, although the hard rock nature of the seafloor would not support the deployment of a free fall funnel (which usually guides re-entry). After a camera survey it was concluded that direct re-entry might be feasible and preparations started in the late afternoon.


Daily Science Report for 29 January 2011

LOCATION: Site U1376 (Prospectus Site LOUI-7A). Position: 32°12.99' S Lat., 171°52.84' W Long.

SCIENCE UPDATE: Cores U1376A-5R to -7R (38.2 - 67.0 mbsf) were retrieved with 88% recovery. The upper part of Core U1376A-5R records the transition from the bright white limestone to the volcanic basement; the algae reef grew on top of a ~3 m thick conglomerate formed by rounded basaltic clasts of various size within a fine-grained matrix that shows several erosional surfaces. The conglomerate lies on top of a mixed succession of hyaloclastite breccia and vesicular lava units that continues into Core U1376A-7R. The lava is moderately olivine and pyroxene phyric and some units are described as in situ pillow lava. Several intervals in the lava are surprisingly well preserved (containing fresh olivine) and fresh glass is occasionally found in the brecciated matrix. The series of Site U1374 meetings was concluded today with two presentations by the Downhole Logging group. All laboratory groups have submitted their Site U1374 reports and the co-chiefs and expedition manager are busy reviewing them.


Daily Science Report for 28 January 2011

LOCATION: Site U1376 (Prospectus Site LOUI-7A). Position: 32°12.99' S Lat., 171°52.84' W Long.

SCIENCE UPDATE: Cores U1376A-2R to -4R (9.5-38.2 mbsf) were cored with 66% recovery. Layered, sandy volcanic breccia dominates Core U1376A-2R. Core U1376A-3R shows a sharp transition from brown-beige bioturbated volcanic tuff in the upper core sections to dazzling white limestone in Section U1376A-3R-4 (corresponding to 23.4 mbsf). The limestone continues downhole in Core U1376A-4R. First investigations revealed that the limestone was not formed by corals but by reef-building algae. Minor components are gastropods, bivalves and solitary corals. The rock is described as boundstone (a carbonate rock whose original components were bound together during formation and remained in the position of growth). The series of Site U1374 meetings was continued today with presentations by the Geochemistry, Physical Properties and Paleomagnetics laboratory groups.


Daily Science Report for 27 January 2011

LOCATION: Site U1376 (Prospectus Site LOUI-7A). Position: 32°12.99' S Lat., 171°52.84' W Long.

SCIENCE UPDATE: Although the TV survey of the seafloor at new Site U1376 found no soft sediment cover, Hole U1376A was successfully spudded into hard bottom in the mid-morning. Core U1376A-1R (0-9.5 mbsf) retrieved an interesting succession of sedimentary rocks with 85% recovery. The material is described as cemented volcaniclastic breccia and volcaniclastic sandstone. Four prominent 1-2 cm thick manganese layers and two yellow, several cm thick altered and bioturbated volcanic ash layers can be found in the upper part of the core. The series of Site U1374 meetings was continued today with presentations by the Igneous Petrology, Alteration Petrology and Structural Geology laboratory groups.


Daily Science Report for 26 January 2011

LOCATION: Site U1376 (Prospectus Site LOUI-7A). Position: 32°12.99' S Lat., 171°52.84' W Long.

SCIENCE UPDATE: The second attempt to start a proper hole at Site U1375 was unsuccessful. Hole U1375B had to be abandoned after just 8.5 meters of advancement when it became clear that the uppermost part of the formation was not stable enough for drilling. However, Core U1375B-1R (0-8.5 mbsf) recovered 0.57 cm of relatively fresh micro-gabbro; a term that was chosen to reflect its coarser mineral grain size. The rock is olivine-augite-phyric and contains abundant plagioclase needles in the groundmass. Since it was highly questionable that a suitable drill site could be found on this seamount it was decided to move to the nearest Alternate Site LOUI-7A, located 90 nm to the NW on Burton Seamount. The vessel arrived at the new Site U1376 shortly before midnight. Sampling for post-expedition research from Site U1374 cores was finally completed today by selecting samples from Cores U1374A-51R through -73R.


Daily Science Report for 25 January 2011

LOCATION: Site U1375 (Prospectus Site LOUI-2B). Position: 33°41.9' S Lat., 171°26.94' W Long.

SCIENCE UPDATE: The vessel arrived at the new site in the early morning and Hole U1375A was spudded on a flat, sandy seafloor plane in the early afternoon. Core U1357A-1R (0-8.5 mbsf) recovered only 2 cm of loose sand in the core catcher. The material is described as sandy, foraminiferal ooze containing abundant Pleistocene to Holocene planktonic foraminifers and nannofossils. Unfortunately the uppermost part of the hole was not stable enough to continue coring, therefore coring was cut short and Core U1375A-2R (8.5-11.5 mbsf) was retrieved after 3 m of advancement. The core recovered 1.5 m of consolidated material of varying lithology. The upper 1 m is a colorful conglomerate composed of at least three different types of volcanic clasts (detailed description is ongoing) that are cemented by a white, foraminifer-rich limestone matrix. The lower part of the core is a yellowish volcanic sandstone containing (shallow-marine?) bioclasts. The decision was made to start a new hole 300 m further to the NW in the hope of finding better drilling conditions. Hole U1357B was spudded shortly before midnight. Sampling for personal, post-expedition research continued today from Cores U1374A-50R through -60R.


Daily Science Report for 24 January 2011

LOCATION: Underway to Site U1375 (Prospectus Site LOUI-2B). Midnight position: 33°18.9' S Lat., 171°54.2' W Long.

SCIENCE UPDATE: While the ship is steaming towards our next drill site the laboratory groups are catching up with thin section observations and physical and chemical analysis for the lowermost cores from Hole U1374A. The first groups submitted their reports for Site U1374 and the co-chiefs and expedition manager are busy reviewing them. Before noon, sampling for post-expedition research continued from Cores U1374A-38R through -49R.


Daily Science Report for 23 January 2011

LOCATION: Underway to Site U1375 (Prospectus Site LOUI-2B). Midnight position: 29°17.5' S Lat., 173°7.01' W Long.

SCIENCE UPDATE: Despite all efforts the stuck pipe could not be worked free. Therefore the lower end of the drill string (bottom hole assembly) was severed in the early afternoon. After the remaining drill string was recovered and the vessel secured, we started our 322 nmi long transit to next Site U1375 (Prospectus Primary Site LOUI-2B). Today the last Site U1374 cores got sampled for shipboard studies and the series of Site U1374 meetings was opened with presentations by the sedimentology and biostratigraphy lab groups. Scientists and technical personnel are preparing for sampling the cores from the lower part of Hole U1374A (from 201 to 522 mbsf) for postcruise research during the next few days (over 230 sections).


Daily Science Report for 22 January 2011

LOCATION: Site U1374 (Prospectus Site LOUI-6B). Position: 28°35.75' S Lat., 173° 22.83' W Long.

SCIENCE UPDATE: The extensive downhole logging program in Hole U1374A is completed. The Formation MicroScanner (high-resolution electrical images of the borehole wall and its structures) was run two times, the Ultrasonic Borehole Imager (acoustic amplitude images with 100% borehole wall coverage) acquired high-resolution data from 5 main sections of the hole, and the downhole magnetometer was run a second time to complement the data set from yesterday's first run of the instrument. Unfortunately, the upper part of the formation (surrounding the buried end of the drill pipe) became increasingly unstable towards the end of the logging program. In the late evening the drill string became irretrievably stuck.


Daily Science Report for 21 January 2011

LOCATION: Site U1374 (Prospectus Site LOUI-6B). Position: 28°35.75' S Lat., 173° 22.83' W Long.

SCIENCE UPDATE: After Hole U1374A was prepared for downhole logging the Triple Combo tool string (measuring total and spectral natural gamma ray, density, porosity, and resistivity as well as the hole diameter) was deployed and successfully logged the entire hole up from 520 mbsf. The second deployed instrument was a sophisticated downhole magnetometer (GBM) that also was able to log the entire hole. The next tool will be the Formation MicroScanner that acquires high-resolution electrical images of the borehole wall and its structures. At the end of today the last core sections from Hole U1374A have been processed through the whole-round multisensor data loggers (including the natural gamma detector) and were split for further measurements, description and sampling.


Daily Science Report for 20 January 2011

LOCATION: Site U1374 (Prospectus Site LOUI-6B). Position: 28°35.75' S Lat., 173° 22.83' W Long.

SCIENCE UPDATE: By mid-morning the second attempt to log Hole U1374A had to be abandoned. Even a shorter version of the tool string was not able to advance further than a few meters into open hole. Since downhole logging (including running the third-party borehole magnetometer) is considered very important for this particular deep site, it was decided to make a third and final attempt. The entire drill string was retrieved and Hole U1374A was re-entered with a used C-4 drill bit. The hole was then washed and reamed down to the bottom and after some additional treatment filled with heavy mud, which is supposed to stabilize the hole walls. Logging is scheduled to start the next morning. Sampling for post-expedition research continued today with cores from the upper part of Hole U1374A.


Daily Science Report for 19 January 2011

LOCATION: Site U1374 (Prospectus Site LOUI-6B). Position: 28°35.75' S Lat., 173° 22.83' W Long.

SCIENCE UPDATE: After a new drill string was assembled with a shorter bottom hole assembly and dedicated logging bit, Hole U1374A was successfully re-entered in the early morning. The following time was spent with preparing Hole U1374A for downhole logging and attempts to start the actual logging operations. Unfortunately, the first logging tool suite (Triple Combo) was not able to advance more than a few meters beyond the drill pipe due to formation blockage. In response, the blockage was cleared by circulating and rotating the drill pipe further down, and the logging depth (end of the drill pipe) was deepened to bridge any potentially tight spot further above. At midnight, a new attempt to deploy the logging tool string was made. Meanwhile, splitting and description of the last cores recovered from this hole continued. After splitting the core sections it became clear that many of the basaltic units that were recovered from the deeper part of the hole (below 336 mbsf) represent dikes rather than lava flows. A beautiful example was found in Core U1374A-59R with multiple steep contacts between the aphyric dike and the surrounding plagioclase-phyric volcanoclastic breccia, with the dike displaying chilled margins and edge-parallel vesicle bands. The dikes show a strong magnetic signal and shipboard paleomagnetic investigations are currently underway.


Daily Science Report for 18 January 2011

LOCATION: Site U1374 (Prospectus Site LOUI-6B). Position: 28°35.75' S Lat., 173° 22.83' W Long.

SCIENCE UPDATE: After 133.5 hours drilling with the present bit, Hole U1347A was terminated this morning. To everyone's delight, Cores U1374A-71R, -72R and -73R (513.1-522.0 mbsf) retrieved predominantly lava flows (and only minor intervals of volcanoclastic breccia) with 81% recovery. Advancement for the last Core U1374A-73R had to be stopped after only 1 m (due to beginning bit failure) and retrieved 88 cm of basalt. Curiously, its recovery of 88% reflects exactly the overall recovery for this amazingly successful hole. The beginning of the downhole logging program was delayed due to the failure of the mechanical bit release mechanism to drop the drill bit at the bottom of the hole. This required the retrieval of the entire drill string and re-entering of Hole U1347A with a specialized logging bit. However, this provided the opportunity to shorten the bottom hole assembly (the heavier, lowermost part of the drill string that needs to remain in the upper part of the hole during logging). With the shorter configuration more open hole (below the end of the drill string) is available for logging. The extensive logging program scheduled for this site will enable scientists and technical personal to catch up with core processing and description.


Daily Science Report for 17 January 2011

LOCATION: Site U1374 (Prospectus Site LOUI-6B). Position: 28°35.75' S Lat., 173° 22.83' W Long.

SCIENCE UPDATE: Although the drill bit had accumulated 128 hours of rotation, Cores U1374A-65R to -70R (460.3 to 513.1 mbsf) were retrieved with continuing high penetration rate (3.1 m/hr) and high recovery (93%). Whereas Cores U1374A-65R through -67R recovered the familiar brecciated material, Cores -68R, -69R, and -70R contained well-preserved volcanic units with >6 m, <1 m and ~5 m recovered thickness, respectively. The recovered contacts between the volcanic units and the breccia indicate that these units represent in situ lava flows, which are much desired for the paleomagnetic investigations. Sampling for post-expedition research of "hard rock" samples continued today with cores from Site U1373.


Daily Science Report for 16 January 2011

LOCATION: Site U1374 (Prospectus Site LOUI-6B). Position: 28°35.75' S Lat., 173° 22.83' W Long.

SCIENCE UPDATE: Although the drill bit has accumulated 110 hours of rotation, today's penetration rate (3 m/hr) and recovery (93%) is still record-high. Cores U1374A-59R to -64R (402.8 - 460.3 mbsf) continue to deliver greenish-gray, relatively homogeneous breccia with intercalated lava flows. Whereas two smaller volcanic units are found in U1374A-59R, a massive flow (>7 m recovered) was found in U1374A-60R. The first sampling party for post-expedition research of “hard rock” samples from Site U1372 was conducted in the conference room. This unusual location was chosen to maintain core-processing activities in the core laboratory with the high recovery rate.


Daily Science Report for 15 January 2011

LOCATION: Site U1374 (Prospectus Site LOUI-6B). Position: 28°35.75' S Lat., 173° 22.83' W Long.

SCIENCE UPDATE: Cores U1347A-52R to -58R (335.9-402.8 mbsf) were retrieved with 86% recovery and 3.5 m/hr penetration rate and continued to deliver mainly volcaniclastic breccia. However, the character of the breccia has changed to greenish-gray, finer, and more homogenous material. In addition, the number and thickness of intercalated volcanic units increased; Cores U1347A-52R, -55R and - 58R contain thick lava flows (~4 m, ~3 m and ~1m recovered respectively). Although the bit has reached 93 hours of rotation at the end of today, penetration rate and recovery are still record-breaking. Staff and scientists are preparing for the first large sampling party (for personal, post-expedition research) scheduled for the next 2 days.


Daily Science Report for 14 January 2011

LOCATION: Site U1374 (Prospectus Site LOUI-6B). Position: 28°35.75' S Lat., 173° 22.83' W Long.

SCIENCE UPDATE: Coring in Hole U1374A continues with record-breaking recovery; Cores U1374A-46R to -51R (278.3-335.9 mbsf) were retrieved with 97% recovery and a penetration rate of 3.0 m/hr. The lithology continues to be volcaniclastic breccia with occasionally intercalated possible lava flows. Thin section examinations reveal that a specific clast type contains large (> 1 cm) plagioclase (feldspar) crystals (e.g., found in Cores U1374AR-25 and -29), which contain numerous large melt inclusions.


Daily Science Report for 13 January 2011

LOCATION: Site U1374 (Prospectus Site LOUI-6B). Position: 28°35.75' S Lat., 173° 22.83' W Long.

SCIENCE UPDATE: Deepening of Hole U1374A continued. Cores U1374A-41R to -45R (230.3 to 278.3 mbsf) were drilled at 2.9 m/hr and attained 92% recovery. We are still coring the unusual thick sequence (>230 m) of mainly volcaniclastic breccia occasionally containing thin units of unbrecciated volcanic rocks. It can be debated if those units represent thin lava flows or larger clasts. A small sampling party for postcruise research was conducted for unconsolidated (soft) sediments from the first three sites.


Daily Science Report for 12 January 2011

LOCATION: Site U1374 (Prospectus Site LOUI-6B). Position: 28°35.75' S Lat., 173° 22.83' W Long.

SCIENCE UPDATE: Cores U1374A-34R to -40R (182.3-230.3 mbsf) were recovered with 71% recovery and continued to deliver variably altered volcaniclastic breccia with occasionally intercalated thin volcanic units (possible lava flows?). In the meantime, the biostratigraphic investigation of the thin limestone layer recovered at the top of Core U1374A-3R continued. By now we have compelling evidence both from nannofossil and foraminifer identifications that the limestone is of Late Cretaceous age. This confirms that the volcanic succession recovered below was formed during the main stage of the seamount's formation above the estimated position of the Louisville hotspot at this time. This information is of fundamental importance for the significance of the paleomagnetic studies aimed to constrain the paleolatitude of the Louisville hotspot.


Daily Science Report for 11 January 2011

LOCATION: Site U1374 (Prospectus Site LOUI-6B). Position: 28°35.75' S Lat., 173° 22.83' W Long.

SCIENCE UPDATE: Cores U1374A-27R to -33R (140.0-182.3 mbsf) were retrieved with 91% recovery and continue to deliver variably altered volcaniclastic breccia. It is still unclear to what extent the breccia was transported and reworked before deposition. Some intervals appear autobrecciated (possible lava flow fragments) other intervals represent sedimentary interbeds (with bivalve fragments between volcanic clasts). Well-preserved clasts can be found next to completely altered material whereas other clasts have a relatively fresh interior but show broad alteration rims. Overall, the breccia seemed to be of diachronous origin (rock unit of varying age) with volcanic material (clast, lava fragments) forming the bulk of the material with some cracks and voids subsequently filled by background sedimentation. Eventually, calcite and occasionally zeolite precipitated in the remaining space. Minor, possible in situ (?) lava flows can be found within the breccia such as in Sections U1374A-31R-6 and -32R-4 but the description of these units is still underway. Meanwhile, the co-chief scientists and expedition manager are busy reviewing the Site U1373 reports.


Daily Science Report for 10 January 2011

LOCATION: Site U1374 (Prospectus Site LOUI-6B). Position: 28°35.75' S Lat., 173° 22.83' W Long.

SCIENCE UPDATE: Cores U1374A-24R and -25R (120.8 to 130.4 mbsf) were retrieved in the early morning hours with an amazing recovery of 105%. The necessity of the subsequently scheduled drill bit change provided a welcome opportunity for all laboratory groups to catch up with core descriptions and shipboard measurements. After the hole was successfully re-entered in the late afternoon, Core U1374-26R (130.4-135.2 mbsf) was retrieved in the late evening with 97% recovery. All three cores recovered more of the highly to moderately altered volcaniclastic breccia containing abundant basaltic clasts of variable size. Some of the clasts are surprisingly well preserved and might even contain some fresh volcanic glass, as found in clasts higher up in the breccia succession. Some of the more dense intervals in today's cores could represent thin altered lava flows, but this interpretation cannot be confirmed until the material is split and fully described. At noon, the series of site summary meetings for Site U1373 concluded with presentations by the Geochemistry, Paleomagnetism and Physical Properties laboratory groups. By the end of the day, all sample requests from shipboard scientists for personal postcruise studies were approved by the Sample Allocation Committee. The first sampling party is scheduled after the end of drilling operation at this site.


Daily Science Report for 9 January 2011

LOCATION: Site U1374 (Prospectus Site LOUI-6B). Position: 28°35.75' S Lat., 173° 22.83' W Long.

SCIENCE UPDATE: Today's Cores U1374A-17R through -23R (87.2-120.8 mbsf) continued to recover volcaniclastic breccia with 86% recovery. So far, 12 lithologically different volcanic clast types have been identified. Occasionally (e.g., in Core U1374A-21R), large bioclasts, such as complete bivalve shells, are found, providing evidence that this material has been reworked under submarine conditions. Meanwhile, the shipboard investigation of the 10 cm thick fossil-rich limestone that was recovered in Core U1374A-3R, above the first lava flow at this site, is nearly completed. The identified fossils include benthic and planktonic foraminifera, sea urchin spines, bivalve fragments and bryozoans The occurrence of double-keeled planktonic foraminifers (confined to Turonian through Maastrichtian ages) proves that volcanism at Site U1374 ceased in the late Cretaceous.


Daily Science Report for 8 January 2011

LOCATION: Site U1374 (Prospectus Site LOUI-6B). Position: 28°35.75' S Lat., 173° 22.83' W Long.

SCIENCE UPDATE: Cores U1374A-9R (43.8-48.6 mbsf), -10R (48.6-53.4 mbsf), -11R (53.4-58.4 mbsf), -12R (58.4-68.0 mbsf), -13R (68.0-72.8 mbsf), -14R (72.8-77.6 mbsf), -15R (77.6-84.6 mbsf) and -16R (84.6-87.2 mbsf) were retrieved with an average recovery of 84%. Almost the whole recovered sequence consists of reddish, highly to completely altered volcaniclastic breccia cemented by white calcite (and minor zeolite) that fills most of the voids. Some of the larger (>5 cm) clasts are possible pillow lava fragments with altered glass rims. Downhole (Cores U1374A-14R and -15R), the basaltic intervals are getting thicker and could represent intercalated lava flows but detailed description of these cores is still underway. Core U1374A-16R recovered 2.6 m of massive dark-gray volcanic rock that has a fresh appearance but is not split and processed yet. At noon, the series of site summary meetings for Site U1373 continued with presentations by the Igneous Petrology, Alteration Petrology and Structural Geology lab groups.


Daily Science Report for 7 January 2011

LOCATION: Site U1374 (Prospectus Site LOUI-6B). Position: 28°35.75' S Lat., 173° 22.83' W Long.

SCIENCE UPDATE: Drilling in Hole U1374A progresses slowly (today's average penetration rate= 1.1 m/hr) because the hole is not yet deep enough to apply effective weight on the drill bit. In return, Cores U1374A-5R (25.1-29.4 mbsf), U1374A-6R (29.4-34.2 mbsf), U1374A-7R (34.2-39.0 mbsf), and U1374A-8R (39.0-43.8 mbsf) were retrieved with an exceptional average recovery rate of 98%. A large variety of different lithologies were recovered starting with aphyric, massive basalt in Core U1374A-5R. The horizontal magmatic foliation (preferred orientation of crystal grains and/or flattened vesicles) supports the interpretation that this unit represents a lava flow. At the bottom of the core, the flow transitions into a calcite-cemented, volcaniclastic breccia with pillow fragments containing slightly altered glass, which continues across Core U1374A-6R. Aphyric lava is encountered again in Core U1374A-7R underlain by volcanic sandstone containing bioclasts and small (mm-size) yellow particles of pumice (?) but the description of this core is not completed yet. The shipboard paleontologists found a possible ammonite fragment in the conglomerate of Core U1374A-3R that was recovered the day before. Since this conglomerate is overlying the igneous basement it would confirm that the volcanism at this site ceased in the Mesozoic. However, further paleontological investigations (including the attempt to identify foraminifers in a small limestone interval within the conglomerate) are pending. At noon, the series of site summary meetings for previous Site U1373 was opened with presentations by the Sedimentology, Paleontology and Microbiology laboratory groups.


Daily Science Report for 6 January 2011

LOCATION: Site U1374 (Prospectus Site LOUI-6B). Position: 28°35.75' S Lat., 173° 22.83' W Long.

SCIENCE UPDATE: Today's Cores U1374A-2R (9.6-14.4 mbsf), U1374A-3R (14.4-20.4 mbsf), and U1374A-4R (20.4-25.1 mbsf) were retrieved with recoveries of 91%, 54% and 76%, respectively and record the transition from the thin sedimentary cover into the igneous basement of this seamount. Core U1374A-2R retrieved the same, light-brown cemented sandstone already seen at the bottom of previous Core U1374A-1R that was recovered the day before. In contrast to the unconsolidated, upper part of this succession, no foraminifers were found in the cemented lower part of the sandstone. The main components are altered volcanic rock particles and igneous mineral grains. However, Section U1374A-2R-4 contains a 25 cm thick gastropod-rich horizon. The bedding structure of the sandstone indicates turbidite-like deposition. The sandstone is discordantly underlain by a thin (~1 m recovered) layer of conglomerate. Its well-rounded clasts are made of basaltic rocks coated with a thin layer of manganese and spotty annelid tube fossils. Below the conglomerate, a 10 cm thick foraminifer-rich limestone marks the transition to the first lava flow, which defines the top of the igneous basement at U1374A-3R-2, 89 cm (corresponding to 16.7 mbsf). The lava flow is composed of a highly pyroxene-olivine-phyric basalt that appears very similar to the uppermost flow that was found at the previous Site U1373 (located just 5.6 nm away on the eastern side of this seamount).


Daily Science Report for 5 January 2011

LOCATION: Site U1374 (Prospectus Site LOUI-6B). Position: 28°35.75' S Lat., 173° 22.83' W Long.

SCIENCE UPDATE: After we were unable to re-enter Hole U1373A, we moved to the new Alternate Site LOUI-6B located on the opposite site of this seamount. Hole U1374A was spudded in the evening. It is hoped that drilling at Site U1374 will sample a different set of lava flows (formed at a slightly different time) compared to the lavas recovered at Site U1373. This would add valuably new individual volcanic cooling units for improving the determination of the paleolatitude of the Louisville hotspot at the time this seamount was formed (a primary objective of this expedition). Core U1374A-1R (0.0-9.6 mbsf) arrived at midnight with 75% recovery. The core retrieved a 7.22 m long interval of light-brown, sandy ooze with small volcanic glass shards and pumice fragments. The material contains abundant planktonic and some benthic foraminifers but the detailed biostratigraphic investigation is still underway. With increasing depth, the core material gets more consolidated and cemented. Meanwhile, the Co-Chief Scientists and the Expedition Manager are busy reviewing the site report chapters for Site U1372.


Daily Science Report for 4 January 2011

LOCATION: Site U1373 (Prospectus Site LOUI-6A). Position: 28°33.93' S Lat., 173° 16.78' W Long.

SCIENCE UPDATE: Cores U1373A-12R (56.0-60.7 mbsf) and -13R (60.7-65.7 mbsf) were retrieved with 61% and 88% recovery. The lithology continues with well-preserved, medium gray, aphyric basalt (lava flows). In contrast to the previous cores, the rocks are highly fractured and show a distinct magmatic foliation. At noon, the series of site summary meetings for Site U1372 were concluded by presentations from the Geochemistry and Paleomagnetic laboratory groups. The necessity of the scheduled drill bit change in the evening provided a welcome opportunity to catch up with core descriptions and shipboard measurements.


Daily Science Report for 3 January 2011

LOCATION: Site U1373 (Prospectus Site LOUI-6A). Position: 28°33.93' S Lat., 173° 16.78' W Long.

SCIENCE UPDATE: Today's Cores U1373A-7R (32.7-37.4 mbsf), -8R (37.4-42.1 mbsf), -9R (42.1-46.5 mbsf), -10R (46.5-51.3 mbsf) and -11R (51.3-56.0 mbsf) were retrieved with excellent average recovery of 97%. Fluorescent microspheres for microbiologic contamination testing were deployed in Core U1373A-11R. The transition from predominantly clastic (conglomerate) sediment with minor lava units to "igneous basement" (predominantly lava flows) was identified at U1373A-7R-1, 121 cm corresponding to 33.9 mbsf. At that depth, a distinct highly olivine-pyroxene-phyric basaltic lava flow was encountered. The same lithology was found in some of the clasts in the overlying conglomerate, and pending geochemical analyses will show if those clasts can be related to this flow. Below this distinct flow, the lavas become less phyric to aphyric. Several flows show a peperitic texture (caused by mixture or shallow intrusion of lava into unconsolidated sediment) either at the flow margins or throughout the whole flow. At noon, the site summary meetings for previous Site U1372 continued with presentations by the Physical Properties and Microbiology laboratory groups.


Daily Science Report for 2 January 2011

LOCATION: Site U1373 (Prospectus Site LOUI-6A). Position: 28°33.93' S Lat., 173° 16.78' W Long.

SCIENCE UPDATE: Drilling in Hole U1373A progressed slowly (1 m/hr average penetration rate) but with increasing drilling depth more weight can be applied on the drill bit resulting in progressively faster penetration. Cores U1373A-2R (9.6-14.1 mbsf), -3R (14.1-18.6 mbsf), -4R (18.6-23.8 mbsf), -5R (23.8-28.0 mbsf) and -6R (28.0-32.7 mbsf) were retrieved with 53% average recovery. The cores show a succession of conglomerates and breccias with volcanic clasts up to boulder size. Nine different clast types are identified based on distinct phenocryst assemblage and vesicularity. The conglomerate in Cores U1373A-2R and -3R possibly host two brecciated lava flows. The interval from the bottom of Core U1373A-3R to the end of Core U1373A-4R is interpreted as "beach rock", a slightly carbonate-cemented sediment consistent of bedded sand and gravel with abundant biogenic components (shell fragments). It contains well-rounded volcanic clasts. The largest clast (U1373A-4R-1A, 0-20 cm, #1) is covered by annelid tube fossils. At noon, the site summary meetings for previous Site U1372 continued with presentations by the Igneous Petrologists, Structural Geologists and Alteration Petrologists.


Daily Science Report for 1 January 2011

LOCATION: Site U1373 (Prospectus Site LOUI-6A). Position: 28°33.93' S Lat., 173° 16.78' W Long.

SCIENCE UPDATE: After the drill string was deployed, the VIT camera revealed that the seafloor at the summit of this guyot is covered by boulders and outcrops of hard rock (lava flows?). Eventually a clear location was found and seafloor was tagged at 1458 meter below rig floor. Hole 1373A was spud at 07:00 hr but due to the hard formation the first core was not received until 20:10. Core U1373A-1R (0-9.6 mbsf) recovered a 2.86 m succession of carbonate-cemented, poorly sorted conglomerate, which contains abundant volcanic clasts of all sizes and rare small bioclasts. Of particular interest is a ~75 cm large highly olivine-phyric bolder. The individual olivine phenocrysts reach up to ~0.5 cm in diameter and appear, except for the outer 4 cm at the bolder rim, surprisingly fresh. Geochemical analyses will reveal if this rock can be called "picritic" (a volcanic rock characterized by high magnesium and low silica content). To everyone's surprise, the core catcher contained some unconsolidated sediment (about 3 tablespoons full) that most likely came from the top of the core. The sand- to pebble-size sediment is composed of abundant volcanic rock fragments and planktonic foraminifers and rare benthic foraminifers, nannofossils and Mn-crust fragments. Preliminary assessments of the fossil assemblage and the fact that the foraminifer shells are not filled also suggest that the sediment represents a sample of the present-day seafloor cover.




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Modified on Friday, 11-Feb-2011 14:56:12 CST.