Preliminary geologic Map of the Perris 7.5' Quadrangle, Riverside County, California

This data set maps and describes the geology of the Perris 7.5' quadrangle, Riverside County, California. Created using Environmental Systems Research Institute's ARC/INFO software, the data base consists of the following items: (1) a map coverage containing geologic contacts and units, (2) a coverage containing structural data, (3) a coverage containing geologic unit annotation and leaders, and (4) attribute tables for geologic units (polygons), contacts (arcs), and site-specific data (points). In addition, the data set includes the following graphic and text products: (1) a postscript graphic plot-file containing the geologic map, topography, cultural data, a Correlation of Map Units (CMU) diagram, a Description of Map Units (DMU), and a key for point and line symbols, and (2) PDF files of the Readme (including the metadata file as an appendix), and the graphic produced by the Postscript plot file.
The Perris quadrangle is located in the northern part of the Peninsular Ranges Province within the central part of the Perris block, a relatively stable, rectangular in plan area located between the Elsinore and San Jacinto fault zones.
The quadrangle is underlain by Cretaceous age and older basement rocks. The Cretaceous plutonic rocks are part of the composite Peninsular Ranges batholith. A wide variety of intermediate composition granitic rocks are located in the quadrangle. These rocks are mainly of tonalitic composition but range from monzogranite to diorite. Most rock is faintly to intensely foliated. Many are heterogenous and contain varying amounts of meso-and melanocratic discoidal-shaped inclusions. Some rocks are composed essentially of inclusion material and some are migmatitic. Included within these granitic rocks are a few septa of Paleozoic(?) schist of upper amphibolite metamorphic grade.
Metamorphic rocks of probable Mesozoic age occur in the southwest corner of the quadrangle. Most of these rocks are well-foliated phyllite of Mesozoic age. The metamorphic grade of these rocks is greenschist or sub-greenschist. Rocks of probable Paleozoic age occur as scattered masses within plutonic rocks in the northern part of the quadrangle. These rocks are of amphibolite grade and include cordierite and sillimanite biotite schist.
In the center and southeast quarter of the quadrangle, biotite-hornblende tonalite of the Lakeview Mountains pluton is characterized by ubiquitous schlieren and by a lack of potassium feldspar. Masses of leucocratic and melanocratic rock occur scattered throughout the pluton. Mesocratic-to melanocratic discoidal-shaped inclusions are oriented parallel to the schlieren. A small body of comb-layered gabbro is located with the tonalite near the southern margin of the pluton. The tonalite contains rare-earth bearing, zoned pegmatite dikes.
Biotite-hornblende tonalite located in the southwest part of the quadrangle is part of the Val Verde pluton. This tonalite is similar to that of the Lakeview Mountains pluton but lacks the ubiquitous schlieren and contains potassium feldspar.
Diagonally crossing the quadrangle is the channel and flood plain of the ephemeral San Jacinto River. Most of the alluviated area west of the San Jacinto River consists of Pleistocene age fluvial deposits, which have a degraded upper surface that is preserved in some places near the contact with granitic rocks. The upper part of these deposits form the Paloma surface of Woodford and others (1971). A modern-to Holocene-age drainage channel is within these older Pleistocene deposits. Younger Pleistocene alluvial fans emanate from the Lakeview Mountains east of the San Jacinto River.

本数据集对加利福尼亚州里弗赛德县佩里斯7.5分幅测区（Perris 7.5' quadrangle）的地质情况进行填图与描述。本数据集采用环境系统研究所（Environmental Systems Research Institute）的ARC/INFO软件构建，其数据库包含以下内容：(1) 存储地质接触关系与地质单元的地图覆盖数据集（map coverage）；(2) 存储构造数据的覆盖数据集（coverage）；(3) 包含地质单元注记与引导线的覆盖数据集（coverage）；(4) 针对地质单元（多边形）、接触线（弧段）以及专项点位数据（点要素）的属性表。此外，本数据集还包含以下图文成果：(1) 包含地质图、地形数据、人文地理数据、地质单元对比图（Correlation of Map Units，CMU）、地质单元描述图（Description of Map Units，DMU）以及点线符号图例的PostScript图形绘图文件；(2) 包含自述文件（Readme，含作为附录的元数据文件（metadata file））以及由PostScript绘图文件生成的图形的PDF文件。
佩里斯测区位于佩里斯地块（Perris block）中部的半岛山脉省（Peninsular Ranges Province）北部，佩里斯地块为一处相对稳定的平面呈矩形的区域，地处埃尔西诺尔断裂带（Elsinore fault zone）与圣哈辛托断裂带（San Jacinto fault zone）之间。
本测区基底为白垩纪（Cretaceous age）及更古老的基底岩系（basement rocks）。白垩纪深成岩（plutonic rocks）属于复合半岛山脉岩基（Peninsular Ranges batholith）的组成部分。测区内广泛分布多种中等成分的花岗质岩石（granitic rocks），其主体为英云闪长岩（tonalitic composition）成分，范围涵盖二长花岗岩（monzogranite）至闪长岩（diorite）。多数岩石具微弱至强烈的面状叶理（foliated），多数岩石非均质性（heterogenous）明显，含有不同含量的中色-暗色圆盘状包体（meso-and melanocratic discoidal-shaped inclusions）；部分岩石几乎完全由包体物质构成，另有部分为混合岩（migmatitic）。这些花岗质岩石中还夹有少量疑似古生代（Paleozoic(?)）的高角闪岩相变质片岩。
测区西南角分布有疑似中生代（Mesozoic age）的变质岩，其中多数为具良好面状叶理的中生代千枚岩（phyllite），其变质相为绿片岩相（greenschist）或亚绿片岩相（sub-greenschist）。测区北部的深成岩中散布有疑似古生代的岩块，这些岩石属于角闪岩相，包括堇青石（cordierite）-矽线石（sillimanite）黑云母片岩（biotite schist）。
在测区中部与东南部，莱克维尤山岩体（Lakeview Mountains pluton）的黑云母角闪石英云闪长岩（biotite-hornblende tonalite）以普遍发育的石香肠构造（schlieren）且不含钾长石（potassium feldspar）为典型特征。岩体中散布有浅色岩（leucocratic rock）与暗色岩（melanocratic rock），中色至暗色的圆盘状包体与石香肠构造平行排列。在岩体南缘附近的英云闪长岩中，产出一处梳状层状辉长岩（comb-layered gabbro）。该英云闪长岩含有含稀土元素（rare-earth）的分带伟晶岩脉（zoned pegmatite dikes）。
测区西南部的黑云母角闪石英云闪长岩属于瓦尔德韦德岩体（Val Verde pluton），该英云闪长岩与莱克维尤山岩体的英云闪长岩类似，但不发育普遍分布的石香肠构造，且含有钾长石。
季节性圣哈辛托河（ephemeral San Jacinto River）的河道与河漫滩（flood plain）斜穿本测区。圣哈辛托河西侧的大部分冲积区域（alluviated area）由更新世（Pleistocene age）河流沉积（fluvial deposits）构成，其上部地表已遭剥蚀，仅在部分与花岗质岩石接触的区域得以保存。该沉积层的上部构成了伍德福德等人（1971）提出的帕洛玛面（Paloma surface）。在这些较老的更新世沉积中，发育有现代至全新世（Holocene-age）的排水河道。圣哈辛托河东侧的莱克维尤山产出了较新的更新世冲积扇（alluvial fans）。