IODP Expedition 344

Costa Rica Seismogenesis Project,
Program A Stage 2 (CRISP-A2)

Daily Science Report for 10 December 2012

LOCATION: Hole U1414A (8°30.2304′N, 84°13.5298′W, 2459 m water depth; proposed Site CRIS-19A),
and in transit to Puntarenas, Costa Rica

SCIENCE UPDATE: Sampling was completed for the hard rock cores. The first logging run with the triple combo-Ultrasonic Borehole Imager (UBI) tool string finished at 0405 h. The second logging run with the Formation MicroScanner (FMS)-Sonic tool string started at 0635 h and finished at 1200 h. The end of the expedition was celebrated with a talk by Miriam Kastner on the role of gas hydrates on climate change. Scientists spent the remainder of the day finalizing the Site U1414 reports and Expedition Summary chapter.

As the drill string was being pulled out of the hole the JOIDES Resolution started the 95-nmi transit to Puntarenas, Costa Rica, in dynamic positioning mode. The end of the drill string cleared the rig floor at 1935 h, ending Site U1414. The thrusters were raised at 2015 h and the vessel picked up speed, arriving at the Puntarenas pilot station at 0335 h on 11 December. The first line ashore was at 0502 h.

CRISP-2 Expedition 344 signing out

Daily Science Report for 9 December 2012

LOCATION: Hole U1414A (8°30.2304′N, 84°13.5298′W, 2459 m water depth; proposed Site CRIS-19A)

SCIENCE UPDATE: Cores U1414A-60R to 63R were recovered from 447.3 to 471.7 mbsf with 15.1 m recovered (62%). Core 63R, the last core of the expedition, arrived on deck at 1205 h. In preparation for logging, the hole was swept clean with mud and the bit was released. The end of the drill string was set at 96 mbsf and the logging tools were rigged up at 1630 h. The first logging run with the triple combo-Ultrasonic Borehole Imager (UBI) tool string started at 1915 h. Logs were collected down to 421 mbsf, where the tools string encountered an obstruction. Logging activities are scheduled to end by 1200 h on 10 December so that the vessel can be prepared for the transit back to Puntarenas.

Core description for the expedition ended with Cores U1414A-58R to 63R. A calcareous, layered sandstone with siliceous mud was encountered between 437.7 and 439.4 mbsf. This unit consists of greenish sandstone, reddish calcareous siltstone, and rare claystone. Beneath the intercalated sediment unit, we encountered a second massive basaltic unit with similar textures to the massive basaltic unit above the sediment. Devitrified glass and autobrecciation were observed at the uppermost portion of the second basaltic unit. Megacrysts of plagioclase are present in Core U1414A-62R. The presence of intercalated sediment with massive basalt above and below divides basement at Site U1414 into three units. Sampling continued for the hard rock cores. A science meeting was held to discuss the results of Site U1414. Scientists spent the remainder of the day measuring the last few cores and writing the Site U1414 reports and Expedition Summary chapter.

Daily Science Report for 8 December 2012

LOCATION: Hole U1414A (8°30.2304′N, 84°13.5298′W, 2459 m water depth; proposed Site CRIS-19A)

SCIENCE UPDATE: Cores U1414A-54R to 59R were recovered from 418.2 to 447.3 mbsf with 17.2 m recovered (59%). Recovery of igneous basement continued with little change in lithology, which is dominated by massive, fine-grained, moderately phyric and slightly to moderately altered basaltic lavas flows with low vesicle abundances. Plagioclase is the dominant phenocryst, followed by pyroxene and rare olivine. Veins of millimeter thickness are common and typically contain calcite, pyrite, silicate and additional unidentified secondary minerals. The first few basalt cores were laid out so that scientists could identify their samples.

Daily Science Report for 7 December 2012

LOCATION: Hole U1414A (8°30.2304′N, 84°13.5298′W, 2459 m water depth; proposed Site CRIS-19A)

SCIENCE UPDATE: Cores U1414A-47R to 53R were recovered from 384.3 to 418.2 mbsf with 26.2 m recovered (77%). Igneous basement was encountered at 375 mbsf. Cores 45R to 50R comprise a ~25 m thick sequence of massive basalt. So far two units have been tentatively identified based on a textural changes. Alteration is slight to moderate, with veins composed of carbonate, sulfides, silicates, and unidentified green minerals that are evenly distributed. One videoconference was held with high school students in Jefferson, Georgia.

Daily Science Report for 6 December 2012

LOCATION: Hole U1414A (8°30.2304′N, 84°13.5298′W, 2459 m water depth; proposed Site CRIS-19A)

SCIENCE UPDATE: Cores U1414A-39R to 46R were recovered from 335.8 to 384.3 mbsf with 13.9 m recovered (29%). The lowermost part of the sedimentary sequence at Hole U1414A is made out of gray to light gray, heavily bioturbated calcareous siltstone with varying amounts of silicic biogenic components. Slight color changes are associated with more sandy components, mainly tephras and coarser biogenic material, that are disseminated in the cores and are sometimes enriched in diffuse layers. Close to the boundary with the igneous basement the mix of biogenic calcite and silica material became well lithified and was replaced by calcareous and silicic cement, although the sedimentary structures are still preserved. The contact between the sediments and igneous ocean crust was recovered in Core 45R. Two videoconferences were held with high school students in Jefferson, Georgia, and in France with the participation of a French scientist.

Daily Science Report for 5 December 2012

LOCATION: Hole U1414A (8°30.2304′N, 84°13.5298′W, 2459 m water depth; proposed Site CRIS-19A)

SCIENCE UPDATE: The free fall funnel was released at 0025 h and the subsea camera was deployed to observe the position of the cone on the seafloor and the drill pipe clearing it as it was being pulled out of the hole. The drill string continued to be pulled and cleared the rig floor at 0740 h. An RCB coring assembly was put together and the drill string was lowered back down to the seafloor. The subsea camera was redeployed at 1315 h and, after searching for the cone, Hole U1414A was reentered at 1543 h. The drill string continued its advance down the hole without encountering any resistance and coring resumed at 1830 h where XCB coring had stopped on 4 December. Cores U1414A-36R to 38R were recovered from 311.9 to 335.8 mbsf with 12.2 m recovered (51%).

The lithology of Cores 24X to 30X is characterized by several meter-scale changes from a brownish beige nannofossil-rich calcareous ooze to a whitish sponge spicule-rich calcareous ooze with nannofossils. Radiolarians, silicoflagellates, foraminifers, and diatoms are common to abundant. Eight mostly felsic ash layers were identified in the sediments. Nannofossils and radiolarians are Miocene age below Core 24R. A science meeting was held to discuss the findings from Hole U1412D and review the hard rock sampling plan for Hole U1414A. The design that won the expedition logo competition was printed on t-shirts in the afternoon.

Daily Science Report for 4 December 2012

LOCATION: Hole U1414A (8°30.2304′N, 84°13.5298′W, 2459 m water depth; proposed Site CRIS-19A)

SCIENCE UPDATE: Cores U1414A-19H to 35X were recovered from 162.1 to 311.9 mbsf with 132.9 m recovered (89%). Cores 33X–35X had partial advancement due to the hard layers encountered, and the decision was made to switch from XCB to RCB coring. The drill string was pulled out of the hole starting at 2115 h and by 2245 h had reached 114 mbsf. At the end of the day, a free fall funnel was installed on the moonpool in preparation for reentering the hole with the RCB coring assembly.

The lithology changed gradually from terrigenous- and biogenic-dominated components in Core 7H to a nearly terrigenous-free calcareous ooze dominated by nannofossils, radiolarians, foraminifers, and diatoms. So far 20 tephra layers have been observed, ranging in thickness from 1 to 65 cm. Nannofossils indicate a Pliocene age around Core 19H and radiolarians indicate a Miocene age around Core 24X. Three videoconferences were held with high school students in Toledo, Ohio, and middle school students in St. Petersburg, Florida. A fourth conference was held with fifth grade students in a Spanish immersion class in Washington, DC, with the participation of scientists from Spain and Costa Rica.

Daily Science Report for 3 December 2012

LOCATION: Hole U1414A (8°30.2304′N, 84°13.5298′W, 2459 m water depth; proposed Site CRIS-19A)

SCIENCE UPDATE: The JOIDES Resolution arrived at Site U1414 at 0015 h. The drill string continued to be lowered to the seafloor and Hole U1414A was spudded at 0805 h. Cores U1414A-1H to 18H were recovered from 0 to 162.1 mbsf with 167.4 m recovered (103%). APCT-3 formation temperature measurements were taken with Cores 3H, 5H, 7H, and 9H.

The first few cores from Hole U1414A are composed of the typical hemipelagic, greenish gray, silty clay characterized by terrigenous rock fragments and magmatic minerals from the nearby Costa Rican volcanic arc. There are abundant nannofossils and radiolarians, and common to rare diatoms and foraminifers. Nannofossils from the top two cores indicate a late Pleistocene age. A science meeting was held to discuss the Site U1413 results. Five videoconferences were held with education officer Dena Rosenberger’s high school students in Lakeside, California.

Daily Science Report for 2 December 2012

LOCATION: Hole U1412D (8°29.1402′N, 84°7.7793′W, 1973 m water depth; proposed Site CRIS-9A)

SCIENCE UPDATE: The day started with drilling without recovery from 273 to 350.4 mbsf. Cores U1412D-2R to 3R were recovered from 350.4 to 369.2 mbsf with 12.3 m recovered (65%). Following the retrieval of Core 3R, hole conditions deteriorated drastically. The drill string became stuck and was eventually worked free with 175 klbs of overpull. The decision was made to abandon Hole U1412D and to proceed to Site U1414 (proposed Site CRIS-19A) to characterize the sediments and basement incoming into the subduction zone along the transect that includes Site U1413 (proposed Site CRIS-13B). The drill string was pulled out of the hole, clearing the rotary table at 2105 h and ending Hole U1412D. An APC/XCB botton-hole assembly was rigged up and the drill string had been lowered to 164 m below the rig floor by midnight. In the meantime, the JOIDES Resolution started the transit to Site U1414 in dynamic positioning mode at 1745 h and by the end of the day had completed 5.4 nmi out of the 6-nmi transit.

Cores U1412D-2R and 3R contain foraminifer-rich grayish olive green claystone with minor amounts of silt. Horizons with reworked silty clay clasts as well as abundant bioturbation structures have been post-depositionally deformed and several disseminated tephra pod layers occur throughout the cores. Nannofossils from Core 3R indicate an early Pleistocene age. Paleomagnetic measurements continued for Hole U1413C and scientists continued to work on Site U1413 reports. Alan Baxter gave a talk on Himalayan geology.

Daily Science Report for 1 December 2012

LOCATION: Hole U1412D (8°29.1402′N, 84°7.7793′W, 1973 m water depth; proposed Site CRIS-9A)

SCIENCE UPDATE: The day started with the rest of the drill string being pulled out of the hole, clearing the rotary table at 0145 h and ending Hole U1413C. The JOIDES Resolution left Site U1413 at 0145 h and arrived at Site U1412 at 0330 h after a 15-nmi transit. The reason for returning to this site is to make one more attempt at recovering the décollement at a slightly shallower depth than Hole U1412C. Upon arrival, an RCB coring assembly was assembled and the drill string was lowered to just above the seafloor. Hole U1412D was spudded at 0850 h and drilling without recovery advanced to 273 mbsf by the end of the day. Sampling and most measurements have been completed for Site U1413 and scientists are working on site reports. A science meeting was held to discuss end of cruise activities as well as postcruise activities and publication obligations.