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These data are high-resolution seismic reflection profile data of the seafloor offshore of Massachusetts, from Nahant to Gloucester. Approximately 1,175 kms of seismic reflection profile data were collected using a Knudsen 320b chirp system Data were processed using SIOSEIS (Scripps Institute of Oceanography) and Seismic Unix (Colorado School of Mines) to produce segy files and jpg images of the profiles. Data were then imported into Landmark SeisWorks, an interactive computer system where horizons were interpreted and digitized to calculate depth to reflectors below the seafloor. Interpreted depth to reflectors were calculated, exported every 5 shots, and then imported to ArcGIS for interpolation into a 50-m raster grid. These data were used to generate a sediment isopach map, which shows the total thickness of sediment that overlies bedrock

This report presents a series of maps that describe the bathymetry and late Quaternary geology of the San Pedro shelf area as interpreted from seismic-reflection profiles and 3.5-kHz and multibeam bathymetric data. Some of the seismic-reflection profiles were collected with Uniboom and 120-kJ sparker during surveys conducted by the U.S. Geological Survey (USGS) in 1973 (K-2-73-SC), 1978 (S-2-78-SC), and 1979 (S-2a-79-SC). The remaining seismic-reflection profiles were collected in 2000 using Geopulse boomer and minisparker during USGS cruise A-1-00-SC. The report consists of seven oversized sheets: 1. Map of 1978 and 1979 uniboom seismic-reflection and 3.5-kHz tracklines used to map faults and folds on San Pedro Shelf. 2. Maps of multibeam shaded bathymetric relief with faults and folds, and bathymetric contours. 3. Isopach map of unconsolidated sediment, seismic-reflection profile across the San Pedro shelf, seismic-reflection profile across San Gabriel paleo-valley. 4. Seismic-reflection profiles across the Palos Verdes Fault Zone. 5. Geologic map and samples of Uniboom and 120-kJ sparker seismic-reflection profiles used to make the map. 6. Map showing thickness of uppermost (Holocene?) sediment layer. 7. Map of San Gabriel Canyon paleo-valley and associated drainage basins.

A seismic-stratigraphic study that used existing USGS high-resolution seismic-reflection profiles was made in the area of the TACTS coreholes. This report presents interpreted cross sections and isopach and structure-contour maps that resulted from that study and some preliminary conclusions. Structure contour maps showing depth below sea level to the upper Eocene, Oligocene, lower Miocene, middle Miocene, lower Pliocene, upper Pliocene, and Quaternary strata are presented. Maps that show the thickness of Oligocene, lower and middle Miocene, middle Miocene, lower Pliocene, upper Pliocene, and Quaternary strata and the total sediment thickness above the phosphatic middle Miocene strata are also shown.

Field and laboratory experiments show that color alteration in conodonts is directly related to the depth and duration of burial and the geothermal gradient and correlates with fixed carbon, vitrinite reflectance, palynomorph translucency, and isopach data. Five progressive and irreversible color changes ranging from pale yellow to black are discriminated. Compilation of color alteration index (CAI) maps for limestones of several ages in the Appalachian basin show: (1) a general systematic change from pale yellow (CAI = 1) to black (CAI = 5) from west to east; (2) within a structural belt, older conodonts are darkest; (3) fixed carbon values determined from coals cannot be directly applied to carbonate rocks; (4) several areas of anomalously low CAI values in windows exposing Ordovician rocks within the Blue Ridge-Piedmont terrane. Data show: (1) color alteration of conodonts is time and temperature dependent; (2) the sequence of color change from pale yellow to black found in field collections is the same as that produced by heating alone; (3) upper and lower geologic temperature limits for each CAI determined from a log time versus reciprocal of absolute temperature plot. Water in combination with confined pressure retards color alteration. The color alteration of conodonts ismore » a valuable tool for assessing organic metamorphism because it is a rapid and inexpensive method requiring only standard laboratory techniques and a binocular microscope. The technique provides thermal cutoffs for oil, condensate, and dry gas generation. Conodont color alteration begins near the upper thermal limit for the preservation of many palynomorphs.« less