ACCESS NUMBER: 31054 

STUDY TITLE: Refining and Revising the GOM OCS Region High Probability Model 

for Historic Shipwrecks

REPORT TITLE: Refining and Revising the Gulf of Mexico OCS Region High 

Probability Model for Historic Shipwrecks, Volume I: Executive Summary, Volume II: 

Technical Narrative, and Volume III: Appendices 

CONTRACT NUMBER: 1435-01-00-CT-31054 

SPONSORING OCS REGION: Gulf of Mexico 

APPLICABLE PLANNING AREA: Gulf of Mexico 

FISCAL YEAR(S) OF PROJECT FUNDING: 2000; 2001 

COMPLETION DATE OF REPORT: March 2004 

COST(S): FY 2000 $161,004; FY 2001 $259,507 

PROJECT MANAGER: Stephen R. James, Jr. 

AFFILIATION: Panamerican Consultants, Inc. 

ADDRESS: 15 South Idlewild Street, Memphis, Tennessee 38104 

PRINCIPAL INVESTIGATOR*: Charles E. Pearson 

KEY WORDS: Gulf of Mexico, shipwreck, probability model, survey, magnetometer, 

line spacing 

BACKGROUND: For 20 years, the Minerals Management Service (MMS) has required 

cultural resources assessments for oil and gas leases in the northern Gulf of Mexico. In 

1989, the Texas A&M Research Foundation completed a study for the MMS to identify 

high probability areas and establish remote sensing survey guidelines and equipment 

requirements most appropriate for locating historic shipwrecks on Federal lands in the 

Gulf of Mexico Region (GOMR). Over the years, deficiencies in the 1989 model of 

historic shipwreck distributions and occurrences have been noted, plus new remote 

sensing technologies have been developed that have application to the MMS program 

of offshore surveys. The present study was undertaken to refine the model of 

shipwreck distributions presented in the 1989 study and reevaluate the survey 

strategies and instrumentation recommended.

OBJECTIVES: (1) To update and expand the existing MMS GOMR shipwreck 

database by examining primary and secondary sources for shipwreck information; (2) 

To determine the spatial correlation between shipwreck locations in the updated 

shipwreck database and recorded seafloor hang sites and sidescan sonar targets and 
ACCESS NUMBER: 31054 

anomalies representing potential shipwrecks identified during previous OCS lease block 

surveys. Then, to ground-truth selected locations where hang sites and reported 

shipwreck locations appear to correlate to determine if hang sites are shipwrecks; (3) To 

conduct a marine magnetometer survey over several verified shipwreck sites using both 

the “industry-standard” proton precession magnetometer and the new cesium 

magnetometer, as well as two other types to determine whether there is a significant 

difference in their performance in detecting shipwrecks and to assess whether changes 

are warranted in MMS GOMR survey methodology; and (4) Based on the results from 

objectives (1), (2) and (3) prepare a revised predictive model for shipwrecks in the 

GOMR, and recommend survey instrumentation and strategies that would be the most 

effective in locating these shipwrecks. 

DESCRIPTION: The study area consists of the entire MMS Gulf of Mexico Region 

(GOMR). The study encompassed four principal tasks. Task 1 involved research to 

collect information to reevaluate and expand the shipwreck data collected in the 1989 

study and to develop a new database of shipwrecks in the GOMR. Task 2 involved the 

correlation of shipwreck data with other sorts of submerged object data from the GOMR, 

such as reported snag and hang data and unidentified objects identified during offshore 

remote sensing surveys. This task included diving on selected offshore targets to 

determine their identity. Task 3 involved conducting magnetometer surveys at selected 

shipwreck target locations at different intervals and speeds using differing equipment 

and survey strategies in order to assess how each instrument recorded the same wreck 

site, and if differences were present, determine if these findings predicated changes to 

the current MMS GOMR survey methodology. Task 4 involved the analysis of collected 

data, the development of a revised model of shipwreck occurrences in the GOMR, and 

the recommendation of survey instrumentation and strategies that would be the most 

effective in locating these shipwrecks. As part of Task 4, all of the information on 

shipwrecks collected during Task 1 was entered into a relational database (Microsoft 

Access) and incorporated into a GIS program (ArcView) that can serve as a tool for 

MMS personnel for the continued assessment and monitoring of shipwreck data in the 

GOMR. 

SIGNIFICANT CONCLUSIONS: The identification of high probability areas requiring 

archaeological survey for historic shipwrecks derived from the 1989 study was flawed 

because of the poor reliability of the positions of loss for so many historic vessels. 

Shipwrecks with very unreliable positions of loss should be eliminated from use in the 

identification and delineation of high probability areas in order to strengthen any effort to 

“predict” wreck location in the GOMR. Besides revealing that all magnetometers 

performed well in the field trials, field investigations found that the current 50m survey 

was effective in recording all study wreck types, but that it is unlikely to be effective in 

identifying all wreck types in the GOMR such as earlier wrecks containing less iron or 

small wooden vessels. Therefore, it is recommended that a closer spaced interval 

should be considered by the MMS for employment in high probability areas. The G-866 

is somewhat antiquated with respect to newer digital magnetometer models and 

changes should be made to the NTL that will accommodate digital technology. 
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STUDY RESULTS: Shipwreck frequencies in the GOMR have increased over time. 

Approximately 41 percent of all shipwreck losses with known dates of loss have 

occurred in the past 25 years and slightly over 77 percent have occurred in the past 50 

years. This pattern is in large part a reflection of the great increase in the number of 

vessels operating in the Gulf of Mexico in the past 50 years, particularly fishing 

(shrimping) vessels, recreational craft, and vessels associated with the offshore oil and 

gas industry. Additionally, this pattern is a reflection of the underreporting of losses 

during earlier historic periods. Twentieth century fishing vessels, principally shrimp 

trawlers, comprise the largest class of vessels reported lost in the GOMR. The 

preservation potentials for shipwrecks in various areas in the GOMR appear to be 

somewhat better than had been anticipated by the 1989 study. 

Areas where historic shipwrecks are most likely to occur and where remote-sensing 

survey should be conducted prior to development were identified. The delineation of 

these "high probability areas" relied on densities of reported shipwrecks and on the 

reliabilities assigned to positions of loss. Broad high probability zones were delineated 

where shipwreck densities were 25 or more within 0.5-degree areas. Reported 

shipwrecks with very poor or unknown reliabilities of position of loss were eliminated 

from this analysis. Other high probability areas were delineated relying on the reported 

locations of specific vessels and their assigned reliability of location. All lease blocks 

containing reported or discovered shipwrecks assigned the highest reliability rating of 

position are classified as high probability lease blocks. Additionally, all lease blocks 

containing the positions of reported shipwrecks assigned a good to moderate reliability 

of position are considered as high probability lease blocks. Further, following the lead 

of the 1989 study, because of the potential for some error in the actual positions of 

these losses the eight contiguous lease blocks around the one containing the vessel 

position are classified as high probability blocks. 

Field investigations revealed that all magnetometers performed well in the survey trials, 

including the G-866, one of the “industry-standards” that we feel at this time has 

become antiquated although functional in most respects. Specific findings of the field 

investigations indicate that: 1) the order of which instrument records the highest 

amplitude appears generally to remain relatively constant, with the SeaSPY and G-877 

exchanging places followed by the G-881 and then the G-866; 2) the 50-m interval is 

unlikely to be effective in identifying all wreck types in the GOMR, especially earlier 

wrecks containing less iron or small wooden vessels or parts of wooden vessels that 

produce smaller magnetic signatures. Therefore, it is recommended that in order to 

provide better detection capability for all types of shipwrecks, especially earlier wrecks 

which might be the most historically significant types within the GOMR, a closer spaced 

transect interval, such as the 30-m interval, should be considered by the MMS for 

employment in high probability areas; 3) given the computer-driven, digital nature of all 

instruments today, NTL requirements appear now to be outmoded and in need of 

revision at least for those magnetometers that are totally digital; 4) the investigation 

highlighted the submersible base station’s potential as an offshore tool in the collection 

of data for post-processing of magnetic survey data. Because of the release 

mechanism failure more in-field research is needed before we will recommend its use; 
ACCESS NUMBER: 31054 

and 5) because contouring presents critical analytic data, it is recommended that even 

without the use of a base station, offshore magnetometer survey data should be 

contoured in situations where a survey is conducted as a single unit (i.e., not split over 

multiple days). 

STUDY PRODUCT(S): 1. REPORT, 2. ACCESS DATABASES, 3. ARCVIEW GIS 

DATA
ACCESS NUMBER: 31054 

20o

25o

30o

24o

0 80 160 240

miles

kilometers

0 100 300

RIO

GRANDE

TAMPA

MOBILE TALLAHASSEE

NEW 

ORLEANS GALVESTON

MEXICO

TEXAS

LOUISIANA

MISSISSIPPI ALABAMA

FLORIDA

CUBA

HAVANA

YUCATAN

98o 95o 90o 85o 81o

SOUTHERN BOUNDARY OF STUDY AREA FEDERAL LEASE BLOCKS

GULF OF MEXICO