Application of core-log-seismic data integration for the high-resolution seismic ... · 1 FRONTIER RESEARCH ON EARTH EVOLUTION, VOL. 2 Application of core-log-seismic data integration

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FRONTIER RESEARCH ON EARTH EVOLUTION, VOL. 2

Application of core-log-seismic data integration for the high-resolution seismicstratigraphy in the Shatsky Rise

Moe Kyaw Thu and Tetsuro Tsuru

Research Program for Data and Sample Analyses, Institute for Research on Earth Evolution (IFREE)

1. Introduction

Core-log-seismic data integration method is an interdiscipli-

nary strategy, integrating core measurements, logging data and

seismic data which are in different resolution and different meas-

urement scales. The investigation by use of multiple scales of

seismic, downhole logging, and core data, contributes to improve

the confidence of each data set. With the availability of the best

combination of facilities in the IFREE, application of this unique

technique has been carried out in various studies with the datasets

taken at different geologic settings around the world.

This study is based on the successful drilling and logging in the

Shatsky Rise in the Ocean Drilling Program (ODP) Leg 198 (Fig.

1). During the two months long leg, eight sites are drilled on a

broad depth transect with six cored sites and two logged sites at all

three heights. A virtually complete section from the Holocene to

Jurassic/ Cretaceous, and first ever igneous rocks are cored from

the region [Shipboard Scientific Party, 2002]. Objective of this study

is to apply high-resolution seismic stratigraphy in the regional

scale through the core-log-seismic data integration between sites.

The results include successful establishing of onsite seismic

stratigraphy at Site 1213 in data integrated way, extension of its

stratigraphy to the Site 1214 along the high-resolution seismic pro-

file, and establishing onsite seismic stratigraphy of Site 1214 for

the lithology of its deeper section which was unknown previously.

2. Data and method

All the data sets, core lithology, well-log and reflection seismic

data, used in this study are taken from the ODP’s Leg 198 in the

Shatsky Rise. Since integration of core-log-seismic data needs

careful adjustments, synthetic seismograms are made from the

density and velocity data and are used to correlate different scales

of data in the integration process. Interpreted units are applicable

to wider area seismic profiles and have close relationship with the

representative lithology [Moe et al., 2002].

At first, high-resolution processing of the multi-channel seis-

mic data is initiated through several trials with various processing

sequences by correlating with synthetic profile. Final processing

sequence includes resampling of the data into 1 ms sampling rate,

filtering of the data within the range of 10 and 180 Hz, and spec-

tral whitening with wider frequency range. Then, onsite seismic

stratigraphic interpretation is carried out at Site 1213 due to the

availability of all data sets for the core-log-seismic data integra-

tion. In this interpretation, synthetic seismogram is modeled

through density and velocity logs and then used as basic interpre-

tation between seismic and logs, and then its equivalent lithos-

tratigraphy. After successful interpretation of seismic stratigraphy

at Site 1213, careful extension of the established stratigraphy is

carried out to the Site 1214 with the support of lithostratigraphy at

Site 1214. With the partial availability of the density and velocity

from the depth of 188 mbsf to 418 mbsf on the logs, the direct

integrated interpretation between synthetic seismogram and seis-

mic profile is based only on this depth range. Even thought litho-

logic units from the each site are used from the onboard interpre-

tations, Site 1213 units are extended to the 1214 on the final inter-

site interpretation.

3. Results

The purpose of core-log-seismic integration in Shatsky Rise is

to relate paleoceanographic events found in the core sample, to

the seismic record. By using logging data as an intermediary

between the core and seismic data, the spatial and temporal extent

of these events can be traced from the borehole location to the

whole study area along the seismic profile. During ODP Leg 198,

only two sites, Site 1207 at the northern height and Site 1213 at

the southern height, were logged. Unlike Site 1207 which is only

site drilled in the northern height, six sites are drilled in the south-

ern height. Since sediment units are cut off in the troughs between

the three heights, inter-site correlation is difficult to make between

them. After considering on the location of sites being on the same

height and reaching oldest sediments and basement, Site 1213 is

chosen to use as primary site for the data integration.

At first, onsite interpretation is followed on the onboard core

description and its lithostratigraphy due to the higher core recovery

at Site 1213. Through the process of depth and well-log properties’

correlations, similar lithostratigraphic units and its equivalent

depths are made on the seismic profile (Fig. 2B). Unit I character-

izes in medium, parallel reflectors with the lithology of nanno

ooze-rich clay. Regional unconformity of big time gap (Santonian

of Late Cretaceous to Pliocene) rest at the base of Unit I. Unit II of

Cenomanian in Late Cretaceous characterizes in weak and medium

reflectors in a thin zone where two subunits of nanno ooze with

chert at the top and chert with porcellanite at the bottom. Unit III is

subdivided into 5 units on its 607.9 m thick zone. Unit IIIA charac-

terizes the strong, parallel reflectors with weak and transparent

reflectors at the top and bottom of the unit in which chert with por-

cellanite and limestone dominates. Chert with porcellanite in unit

IIIB characterizes in weak and transparent reflectors which is sup-

ported by the stable and gradual increase of well-log density.

Below this unit is thin and strong reflecting unit which covers

clayey and porcellanite sediments including thin black shale layer.

Higher restivity, and gamma values are assumed to be the reason

of strong reflectors around black shale layer. Unit IIID is mixed

medium and weak reflector zones which may have caused from the

compact and hard porcellanite and soft nanno chalk. The lower-

most unit IIIE characterizes strong, parallel seismic reflectors at

the upper half and weak reflectors at the lower half of chert, por-

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FRONTIER RESEARCH ON EARTH EVOLUTION, VOL. 2

cellanite, claystone lithology. The age of this unit ranges from

Berriasian (early Cretaceous) to possibility of Late Jurassic.

Extended interpretation of the onsite seismic stratigraphy from

the Site 1213 reached to the Site 1214 with some difficulties due

to the stratigraphic complexity at small trough between two sites

(Fig. 2C). Those difficulties are 1) two topographic troughs

between two sites at which unit II of Cenomanian age is truncat-

ing (Fig. 2C), and 2) thinner sediment layers at the high-angel

slope near Site 1214. Primary interpretations were in doubt

between two seismic patterns, onlapping and truncation.

Thorough investigations concluded it as erosional truncation

which cut off the Unit II at the Height B, not continuing to the

Site 1214. Sediments layers in the Site 1214 changed to thinner in

thickness to the Trough A and caused difficulties in making inter-

pretations. Moreover, unit thicknesses are in big difference

between two sites. Unit I covers thin layer of clayey nanno ooze

in Pleistocene age which are in medium, parallel reflectors.

Cenomanian aged Unit II has been missing at the Site 1214, hence

sediments in the area jumped to the Albian aged bioturbated chert

to porcellanite with strong, parallel seismic reflectors as Unit IIIA.

Unit IIIB mixes weak and strong seismic reflectors of chert, por-

cellanite and limestone lithology. Black shale layer appears in the

Unit IIIC of claystone to clayey porcellanite with strong reflectors

as in Site 1213. ODP drilling at the Site 1214 ended at the top of

the Unit IIID of porcellanite and chert lithology. Extended inter-

pretation from there is the result of the inter-site correlation along

the seismic. This thick unit characterizes strong reflectors at upper

half and semitransparent reflectors at the lower half. The last Unit

IIIE is interpreted as chert, porcellanite and claystone with mix-

ture of strong and medium reflectors.

4. Conclusions

Successful application of the core-log-seismic data integration

in the Shatsky Rise benefited inter-site correlation of the seismic

stratigraphy and lithostratigraphy of the area in wider scale and

higher resolution. Further study is carrying on in the process of

interpretation in depositional and paleoceanographic history of the

region in combination with micropaleontologic and geochemical

results. Final results will have detailed understanding on the depo-

sitional and paleoceanographic history of the area.

Acknowledgements. We thank the captain, crew and technicians of

the JOIDES Resolution from Ocean Drilling Program for the core and

downhole logging data acquisition, A. Klaus and W. Sager from the

Texas A & M University for the seismic data.

References

Moe K. T., K. Tamaki, S. Kuramoto, R. Tada and S. Saito, High-reso-

lution seismic stratigraphy of the Yamato Basin, Japan Sea and its

geological application, The Island Arc, 11/1, 61-78, 2002.

Shipboard Scientific Party, Leg 198 Initial Report, ODP Init. Repts.,

198, 2002.

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FRONTIER RESEARCH ON EARTH EVOLUTION, VOL. 2

Figure 1. Location and bathymetric map illustrating seismic track lines in the southern height of the ShatskyRise. ODP Sites 1213 and 1214 (red circles) and other sites (black and white circles) are shown on the map.

Figure 2. Core-log-seismic data integrated stratigraphic correlation at Sites 1213 and 1214. (A) Onsite lithostratig-raphy and seismic stratigraphy of the Site 1214 in its depth in meters below seafloor, core numbers and their recov-ery, lithologic symbols, units, their geologic age and lithology, their equivalent seismic units are shown from left toright. (B) Onsite lithostratigraphy and seismic stratigraphy of the Site 1213 with additional well-logs and syntheticprofile. (C) Regional seismic stratigraphy of the southern height of the Shatsky Rise through core-log-seismic dataintegrated correlation between Sites 1214 and 1213. Vertical scales are in two-way travel time in seconds.