Geochemistry of North Atlantic Igneous Province basalts

New Sr-Nd-Pb-Hf data require the existence of at least four mantle components in the genesis of basalts from the the North Atlantic Igneous Province (NAIP): (1) one (or more likely a small range of) enriched component(s) within the Iceland plume, (2) a depleted component within the Iceland plume (distinct from the shallow N-MORB source), (3) a depleted sheath surrounding the plume and (4) shallow N-MORB source mantle. These components have been available since the major phase of igneous activity associated with plume head impact during Paleogene times. In Hf-Nd isotope space, samples from Iceland, DSDP Leg 49 (Sites 407, 408 and 409), ODP Legs 152 and 163 (southeast Greenland margin), the Reykjanes Ridge, Kolbeinsey Ridge and DSDP Leg 38 (Site 348) define fields that are oblique to the main ocean island basalt array and extend toward a component with higher 176Hf/177Hf than the N-MORB source available prior to arrival of the plume, as indicated by the compositions of Cretaceous basalts from Goban Spur (~95 Ma). Aside from Goban Spur, only basalts from Hatton Bank on the oceanward side of the Rockall Plateau (DSDP Leg 81) lie consistently within the field of N-MORB, which indicates that the compositional influence of the plume did not reach this far south and east ~55 Ma ago. Thus, Hf-Nd isotope systematics are consistent with previous studies which indicate that shallow MORB-source mantle does not represent the depleted component within the Iceland plume (Thirlwall, J. Geol. Soc. London 152 (1995) 991-996; Hards et al., J. Geol. Soc. London 152 (1995) 1003-1009; Fitton et al., 1997 doi:10.1016/S0012-821X(97)00170-2). They also indicate that the depleted component is a long-lived and intrinsic feature of the Iceland plume, generated during an ancient melting event in which a mineral (such as garnet) with a high Lu/Hf was a residual phase. Collectively, these data suggest a model for the Iceland plume in which a heterogeneous core, derived from the lower mantle, consists of 'enriched' streaks or blobs dispersed in a more depleted matrix. A distinguishing feature of both the enriched and depleted components is high Nb/Y for a given Zr/Y (i.e. positive DeltaNb), but the enriched component has higher Sr and Pb isotope ratios, combined with lower epsilon-Nd and epsilon-Hf. This heterogeneous core is surrounded by a sheath of depleted material, similar to the depleted component of the Iceland plume in its epsilon-Nd and epsilon-Hf, but with lower 87Sr/86Sr, 208Pb/204Pb and negative DeltaNb; this material was probably entrained from near the 670 km discontinuity when the plume stalled at the boundary between the upper and lower mantle. The plume sheath displaced more normal MORB asthenosphere (distinguished by its lower epsilon-Hf for a given epsilon-Nd or Zr/Nb ratio), which existed in the North Atlantic prior to plume impact. Preliminary data on MORBs from near the Azores plume suggest that much of the North Atlantic may be 'polluted' not only by enriched plume material but also by depleted material similar to the Iceland plume sheath. If this hypothesis is correct, it may provide a general explanation for some of the compositional diversity and variations in inferred depth of melting (Klein and Langmuir, 1987 doi:10.1029/JB092iB08p08089) along the MAR in the North Atlantic.

GIS for cartographic accuracy analysis of settlements in the province of Madrid (AGE Tomas Lopez 1804).

Purpose: In this paper we study all settlements shown on the map of the Province of Madrid, sheet number 1 of AGE (Atlas Geográfico de España of Tomas Lopez 1804) and their correspondence with the current ones. This map is divided in to zones: Madrid and Almonacid de Zorita. Method: The steps followed in the methodology are as follow: 1. Geo-reference of maps with latitude and longitude framework. Move the historical longitude origin to the origin longitude of modern cartography. 2 Digitize of all population settlements or cities (97 on Madrid and 42 on Almonacid de Zorita), 3 Identify historic settlements or cities corresponding with current ones. 4. If the maps have the same orientation and scale, replace the coordinate transformation of historical settlements with a new one, by a translation in latitude and longitude equal to the calculated mean value of all ancient map points corresponding to the new. 5. Calculation of absolute accuracy of the two maps. 6 draw in the GIS, the settlements accuracy. Result: It was found that all AGE settlements have good correspondence with current, ie only 27 settlements lost in Madrid and 2 in Almonacid. The average accuracy is 2.3 and 5.7 km to Madrid and Almonacid de Zorita respectively. Discussion & Conclusion: The final accuracy map obtained shows that there is less error in the middle of the map. This study highlights the great work done by Tomas Lopez in performing this mapping without fieldwork. This demonstrates the great value that has been the work of Tomas Lopez in the history of cartography.

The petitioners for settling His Majesties lands and islands lying between Nova Scotia and the province of Main in New England in America : manuscript, [ca. 1720]

Written in an unidentified hand, signed by Barkstead.

Sherbrooke, Eastern Townships and Kennebec Railway, New England, 1874 (Raster Image)

This layer is a georeferenced raster image of the historic paper map entitled: Map of the Sherbrooke, Eastern Townships and Kennebec Railway : with connections, prepared by G.W. & C.B. Colton & Co. It was published in 1874. Scale [ca. 1:1,267,200]. Covers New Hampshire, Vermont, Massachusetts, Connecticut, Rhode Island, and portions of New Jersey, Pennsylvania, New York, Maine, and the province of Quebec, Canada. The image inside the map neatline is georeferenced to the surface of the earth and fit to the USA Contiguous Albers Equal Area Conic projection (Meters). All map collar and inset information is also available as part of the raster image, including any inset maps, profiles, statistical tables, directories, text, illustrations, or other information associated with the principal map. This map shows features such as railroads, railroad connections and stations, drainage, state and county boundaries, and more. Includes inset: [Sherbrooke, Eastern Townships and Kennebec Railway in province of Québec]. Scale [ca. 1:921,600]. This layer is part of a selection of digitally scanned and georeferenced historic maps of New England from the Harvard Map Collection. These maps typically portray both natural and manmade features. The selection represents a range of regions, originators, ground condition dates, scales, and purposes.